WorldWideScience

Sample records for satellite relay systems

  1. Advanced tracking and data relay satellite system

    Science.gov (United States)

    Stern, Daniel

    1992-01-01

    The purpose of this communication satellite system are as follows: to provide NASA needs for satellite tracking and communications through the year 2012; to maintain and augment the current TDRS system when available satellite resources are expended in the latter part of the decade; to provide the necessary ground upgrade to support the augmented services; and to introduce new technology to reduce the system life cycle cost. It is concluded that no ATDRS spacecraft requirement for new modulation techniques, that data rate of 650 MBps is required, and that Space Station Freedom requirement is for 650 MBps data some time after the year 2000.

  2. The power relay satellite

    Science.gov (United States)

    Glaser, Peter E.

    The availability and use of renewable energy sources compatible with reducing risks to the global environment are key to sustainable development. Large-scale, renewable energy resources at undeveloped or underutilized sites are potentially available on several continents. The Power Relay Satellite (PRS) concept has the potential to access these remote energy resources by coupling primary electricity generation from terrestrial transmission lines. A global PRS network can be envisioned to provide a high degree of flexibility for supplying energy demands worldwide with wireless power transmitted from sites on Earth to geosynchronous orbit and then reflected to receivers interfacing with terrestrial power transmision networks. Past developments in wireless power transmission (WPT) are reviewed and recent successful results are noted. The origins of the PRS concept, and a possible configuration are discussed, principles of WPT at microwave frequencies, functional requirements, and system design contraints are outlined, and space transportation concepts presented. PRS assessments including applicable technologies, economic projections, and societal issues are highlighted. It is concluded that the PRS provides a promising option to access renewable resources at great distances from major markets, and represents an important stage in the future development in the future of solar power satellites.

  3. A MEO Tracking and Data Relay Satellite System Constellation Scheme for China

    Institute of Scientific and Technical Information of China (English)

    WU Ting-yong; WU Shi-qi; LING Xiang

    2005-01-01

    A medium earth orbit (MEO) tracking and data relay satellite system (TDRSS) constellation scheme for China is proposed. This system consists of MEO satellite constellation, inter-satellite links (ISLs) and terrestrial gateway station, which can provide continuous bidirectional data transmission links between low altitude spacecrafts and the terrestrial gateway station in China. Theoretical analysis and simulation results indicate that the proposed constellation can cover the global low altitude space sphere and earth surface of China continuously, and has a preferable practical perspective.

  4. Advanced spacecraft tracking techniques using the Tracking and Data Relay Satellite System /TDRSS/

    Science.gov (United States)

    Teles, J.; Ayres, C.

    1977-01-01

    The TDRSS will consist initially of two geosynchronous satellites and a common ground station at White Sands, New Mexico. According to current schedules, operations are to begin in November 1980. The overall TDRSS will provide high and low bit-rate telemetry, commands, and satellite-to-satellite tracking services. Each Tracking and Data Relay Satellite (TDRS) will have four antenna systems for NASA use. The common ground station at White Sands will have three 18-meter K-band antennas. The tracking equipment at the ground station is required to meet the following specifications: (1) 0.1-radian root-mean-square (rms) phase noise on nondestruct Doppler measurements; (2) 10-nanosecond rms range noise; (3) 50-nanosecond maximum systematic range error. Attention is given to two-way range and Doppler measurements, the bilateration tracking of TDRS, and an experiment using differenced one-way Doppler measurements.

  5. ASDAR (aircraft to satellite data relay) flight test report

    Science.gov (United States)

    Domino, E. J.; Lovell, R. R.; Conroy, M. J.; Culp, D. H.

    1977-01-01

    The aircraft to Satellite Data Relay (ASDAR), an airborne data collection system that gathers meteorological data from existing aircraft instrumentation and relays it to ground user via a geo-synchronous meteorological satellite, is described and the results of the first test flight on a commercial Boeing 747 aircraft are presented. The flight test was successful and verified system performance in the anticipated environment.

  6. Power system relaying

    CERN Document Server

    Horowitz, Stanley H; Niemira, James K

    2013-01-01

    The previous three editions of Power System Relaying offer comprehensive and accessible coverage of the theory and fundamentals of relaying and have been widely adopted on university and industry courses worldwide. With the third edition, the authors have added new and detailed descriptions of power system phenomena such as stability, system-wide protection concepts and discussion of historic outages. Power System Relaying, 4th Edition continues its role as an outstanding textbook on power system protection for senior and graduate students in the field of electric power engineering and a refer

  7. Error analysis for relay type satellite-aided search and rescue systems

    Science.gov (United States)

    Marini, J. W.

    1979-01-01

    An analysis is made of the errors in the determination of the position of an emergency transmitter in a satellite-aided search and rescue system. The satellite is assumed to be at a height of 820 km in a near-circular near polar orbit. Short data spans of four minutes or less are used. The error sources considered are measurement noise, transmitter frequency drift, ionospheric effects, and error in the assumed height of the transmitter. The errors are calculated for several different transmitter positions, data rates, and data spans. The only transmitter frequency used was 406 MHz, but the result can be scaled to different frequencies.

  8. Harnessing Light: Laser/Satellite Relay Mirror Systems and Deterrence in 2035

    Science.gov (United States)

    2010-02-16

    satellites. 49 Shutter Controls – Shutter controls on a satellite would enable the electronics and optical sensors to be protected, either as a...from a high-energy laser beam, but it would be a prudent precaution, especially if the shutters were constructed out of one of the advanced materials...October 2009). Fusion Energy Foundation. Beam Defense: An Alternative to Nuclear Destruction. Fallbrook, CA: Aero Publishers, Inc., 1983

  9. Ionospheric refraction effects on TOPEX orbit determination accuracy using the Tracking and Data Relay Satellite System (TDRSS)

    Science.gov (United States)

    Radomski, M. S.; Doll, C. E.

    1991-01-01

    This investigation concerns the effects on Ocean Topography Experiment (TOPEX) spacecraft operational orbit determination of ionospheric refraction error affecting tracking measurements from the Tracking and Data Relay Satellite System (TDRSS). Although tracking error from this source is mitigated by the high frequencies (K-band) used for the space-to-ground links and by the high altitudes for the space-to-space links, these effects are of concern for the relatively high-altitude (1334 kilometers) TOPEX mission. This concern is due to the accuracy required for operational orbit-determination by the Goddard Space Flight Center (GSFC) and to the expectation that solar activity will still be relatively high at TOPEX launch in mid-1992. The ionospheric refraction error on S-band space-to-space links was calculated by a prototype observation-correction algorithm using the Bent model of ionosphere electron densities implemented in the context of the Goddard Trajectory Determination System (GTDS). Orbit determination error was evaluated by comparing parallel TOPEX orbit solutions, applying and omitting the correction, using the same simulated TDRSS tracking observations. The tracking scenarios simulated those planned for the observation phase of the TOPEX mission, with a preponderance of one-way return-link Doppler measurements. The results of the analysis showed most TOPEX operational accuracy requirements to be little affected by space-to-space ionospheric error. The determination of along-track velocity changes after ground-track adjustment maneuvers, however, is significantly affected when compared with the stringent 0.1-millimeter-per-second accuracy requirements, assuming uncoupled premaneuver and postmaneuver orbit determination. Space-to-space ionospheric refraction on the 24-hour postmaneuver arc alone causes 0.2 millimeter-per-second errors in along-track delta-v determination using uncoupled solutions. Coupling the premaneuver and postmaneuver solutions

  10. An Intermediate Frequency Acquisition Scheme for S-band Single Access Link of the Tracking and Data Relay Satellite System

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A nonzero intermediate frequency (IF) likelihood acquisition scheme designed for S-band Single Access (SSA) link of China's Tracking and Data Relay Satellite S y stem (CTDRSS) is introduced. The received signal is downconv erted to IF, and then direct sampled in IF using a 1-bit A/D. After the digital i zation, the sampled data is detected using a hybrid likelihood acquisition schem e. Using this structure, large noise figure of the analog mixer or active filter s, amplitude and phase imbalance between low-frequency in-phase and quandratur e- phase channel can be avoided. An easy designing algorithm of the acquisition sch eme is also derived. The performance and algorithm are verified by computer simu lation.

  11. Subcarrier phase recovery performance in bent-pipe mode of Shuttle data transmission. [on Tracking and Data Relay Satellite System Ku-band return link

    Science.gov (United States)

    Mckenzie, T. M.; Braun, W. R.

    1978-01-01

    The subcarrier phase recovery is analyzed for the bent-pipe mode of Space Shuttle detached-payload data transmission on the Tracking and Data Relay Satellite System (TDRSS) Ku-band return link. The high-power component of the subcarrier modulation is unrestored payload data, either at baseband or modulating another subcarrier. At the receiver a Costas loop recovers the subcarrier phase. To analyze its performance in the baseband case, we obtain the loop S-curve, the power spectral density of the equivalent noise process, and the loop phase error variance.

  12. Airborne relay-based regional positioning system

    National Research Council Canada - National Science Library

    Lee, Kyuman; Noh, Hongjun; Lim, Jaesung

    2015-01-01

    .... To address these pseudolite system limitations, we propose an airborne relay-based regional positioning system that consists of a master station, reference stations, airborne relays and a user...

  13. ARQ strategies for relay cooperative systems

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We propose two novel automatic repeat request (ARQ) strategies for relay cooperative systems over Rayleigh fading channel: one uses relay ARQ and the other destination ARQ. The BER performance of these two strategies is derived in fast block fading. Numerical analysis and simulation show the systems can get more performance gain when the inter-channel (the source to the relay) quality is bad in the relay ARQ strategy. In the destination ARQ strategy, when the uplink qualities of the source and relay to the destination are poor, the average received SNR of the destination is much low, the systems performance can be improved efficiently.

  14. 国外激光链路中继卫星系统的发展与启示%Development and enlightenment of data-relay satellite systems using laser links abroad

    Institute of Scientific and Technical Information of China (English)

    程洪玮; 陈二虎

    2012-01-01

    Laser link data-relay satellite system refers to the satellite system that utilizes laser beam as transmission medium, and relays high rate data of low earth orbit (LEO) information acquisition satellites. Foreign countries have carried out a number of inter-satellite and satellite-ground laser communication experiments. Communication technology has been developed to phase modulation/coherent demodulation from intensity modulation/direct detection, and the communication rate has sped up to 5.6 Gbps. Satellite laser communication is developed towards higher rate, networking applications, terminal miniaturization, and terminal lightweight now. Based on systematical analysis of the typical inter-satellite and satellite-ground laser communication experiments and the development plan of data-relay satellite systems in countries as Europe, Japan and the United States, the development trend of the laser link data-relay satellite system was disaussed, and some enlightenments to construct China's laser link data-relay satellite system were summarized.%激光链路中继卫星系统是指以激光波束为媒介,为低轨信息获取类卫星提供高速数据传输服务的卫星系统.国外已开展了多次星问、星地激光通信实验,已由强度调制/直接探测通信体制过渡到相位调制/相干解调通信体制,通信速率可达5.6 Gbps.卫星激光通信正向更高通信速率、组网应用、终端小型化、轻量化方向发展.在系统分析欧洲、日本、美国等国家典型星间、星地激光通信实验和中继卫星发展计划的基础上,讨论了激光链路中继卫星系统的发展趋势,总结得到对发展我国激光链路中继卫星系统的若干启示.

  15. 77 FR 6949 - Tracking and Data Relay Satellite System (TDRSS) Rates for Non-U.S. Government Customers

    Science.gov (United States)

    2012-02-10

    ... customers via commercial fiber optic cables and/or commercial communications satellites. In the event one of... general by application of principles of priority to user service requirements. Services shall be provided... service actually occurred. (2) The time scheduled by the user project shall include the slew time, set...

  16. Coordination procedure for radio relay and communication satellite services

    Science.gov (United States)

    Eckerman, J.

    1973-01-01

    A global rain rate statistic model is used to link microwave propagation statistics to measurable rain statistics in order to develop international telecommunication site criteria for radio relay and communication satellite services that minimize interference between receivers and transmitters. This rain coordination procedure utilizes a rain storm cell size, a statistical description of the rainfall rate within the cell valid for most of the earth's surface, approximations between Raleigh scatter and constancy of precipitation with altitude, and an analytic relation between radar reflectivity and rain rate.

  17. Alternate transmission relaying based on interference alignment in 3-relay half-duplex MIMO systems

    KAUST Repository

    Park, Seongho

    2012-09-01

    In a half-duplex relaying, the capacity pre-log factor 1/2 is a major drawback in spectral efficiency. This paper proposes a linear precoding/decoding scheme and an alternate relaying protocol in a dual-hop half-duplex system where three relays help the communication between the source and the destination. In our proposed scheme, we consider a phase incoherent method in relays in which the source alternately transmits message signals to the different relays. In addition, we propose a linear interference alignment scheme which can suppress the inter-relay interference resulting from the phase incoherence of relaying. Based on our analysis of degrees of freedom and our simulation results, we show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying. © 2012 IEEE.

  18. Sort-based relay selection algorithm for decode-and-forward relay system

    Institute of Scientific and Technical Information of China (English)

    XIE Gang; LIU YuanAn; GAO JinChun; LI XingZheng

    2013-01-01

    In this paper, a sort-based relay selection algorithm is proposed for decode-and-forward wireless relay systems. The proposed algorithm can reduce computational complexity and system overhead in the relay selection for practical decode-and-forward wireless relay systems with multiple sources and multiple relays. This would be a very important improvement. Firstly, the sufficient and necessary conditions for a relay to be feasible to a source are derived. By adopting relay transmission via its feasible relay, the source can improve channel capacity compared to direct transmission. Then, a sort-based relay selection algorithm is proposed based on the sufficient and necessary conditions. In the proposed algorithm, each relay makes decision on its feasibility individually, but the final source-relay paring decision is made in a centralized manner. Simulation results show that the proposed algorithm can provide considerable system performance improvement over the existing algorithm. Especially at low signal-to-noise (SNR) region, the performance of the proposed algorithm almost reaches the optimal one.

  19. Optical terminal definition for the Future Service Growth (FSG) module of the Advanced Tracking and Data Relay Satellite (ATDRSS)

    Science.gov (United States)

    Bruno, Ronald C.; Kalil, Ford

    1992-01-01

    Results are presented from preliminary analyses and definition studies for an optical terminal's incorporation into the FSG module of the ATDRS system, which must support crosslinks between selected relay satellites of a modified ATDRS constellation and thereby allow the placement of a relay satellite at an orbital location which eliminates the zone of exclusion. These studies have attempted to identify alternative constellations by means of one or more crosslinks, and to formulate the service-routing requirement for the FSG terminal. Attention is given to an FSG optical terminal that furnishes the functionality and performance required for a crosslink terminal.

  20. Optical terminal definition for the Future Service Growth (FSG) module of the Advanced Tracking and Data Relay Satellite (ATDRSS)

    Science.gov (United States)

    Bruno, Ronald C.; Kalil, Ford

    1992-01-01

    Results are presented from preliminary analyses and definition studies for an optical terminal's incorporation into the FSG module of the ATDRS system, which must support crosslinks between selected relay satellites of a modified ATDRS constellation and thereby allow the placement of a relay satellite at an orbital location which eliminates the zone of exclusion. These studies have attempted to identify alternative constellations by means of one or more crosslinks, and to formulate the service-routing requirement for the FSG terminal. Attention is given to an FSG optical terminal that furnishes the functionality and performance required for a crosslink terminal.

  1. Filter-and-Forward Transparent Relay Design for OFDM Systems

    CERN Document Server

    Kim, Donggun; Sung, Youngchul

    2012-01-01

    In this paper, the filter-and-forward (FF) relay design for orthogonal frequency-division multiplexing (OFDM) transmission systems is considered to improve the system performance over simple amplify-and-forward (AF) relaying. Unlike conventional OFDM relays performing OFDM demodulation and remodulating, to reduce processing complexity, the proposed FF relay directly filters the incoming signal with a finite impulse response (FIR) and forwards the filtered signal to the destination. Two design criteria are considered to optimize the relay filter for given source power allocation. One is to minimize the relay transmit power subject to per-subcarrier signal-to-noise ratio (SNR) constraints and the other is to maximize the worst subcarrier channel SNR subject to the total relay transmit power constraint. It is shown that the two problems reduce to semi-definite programming (SDP) problems. Furthermore, the problem of joint source power allocation and relay filter design is considered for the second criterion, and ...

  2. Design Concepts for a Small Space-Based GEO Relay Satellite for Missions Between Low Earth and near Earth Orbits

    Science.gov (United States)

    Bhasin, Kul B.; Warner, Joseph D.; Oleson, Steven; Schier, James

    2014-01-01

    The main purpose of the Small Space-Based Geosynchronous Earth orbiting (GEO) satellite is to provide a space link to the user mission spacecraft for relaying data through ground networks to user Mission Control Centers. The Small Space Based Satellite (SSBS) will provide services comparable to those of a NASA Tracking Data Relay Satellite (TDRS) for the same type of links. The SSBS services will keep the user burden the same or lower than for TDRS and will support the same or higher data rates than those currently supported by TDRS. At present, TDRSS provides links and coverage below GEO; however, SSBS links and coverage capability to above GEO missions are being considered for the future, especially for Human Space Flight Missions (HSF). There is also a rising need for the capability to support high data rate links (exceeding 1 Gbps) for imaging applications. The communication payload on the SSBS will provide S/Ka-band single access links to the mission and a Ku-band link to the ground, with an optical communication payload as an option. To design the communication payload, various link budgets were analyzed and many possible operational scenarios examined. To reduce user burden, using a larger-sized antenna than is currently in use by TDRS was considered. Because of the SSBS design size, it was found that a SpaceX Falcon 9 rocket could deliver three SSBSs to GEO. This will greatly reduce the launch costs per satellite. Using electric propulsion was also evaluated versus using chemical propulsion; the power system size and time to orbit for various power systems were also considered. This paper will describe how the SSBS will meet future service requirements, concept of operations, and the design to meet NASA users' needs for below and above GEO missions. These users' needs not only address the observational mission requirements but also possible HSF missions to the year 2030. We will provide the trade-off analysis of the communication payload design in terms of

  3. Protocols for Relay-Assisted Free-Space Optical Systems

    CERN Document Server

    Chatzidiamantis, Nestor D; Kriezis, Emmanouil E; Karagiannidis, George K; Schober, Robert

    2011-01-01

    We investigate transmission protocols for relay-assisted free-space optical (FSO) systems, when multiple parallel relays are employed and there is no direct link between the source and the destination. As alternatives to all-active FSO relaying, where all the available relays transmit concurrently, we propose schemes that select only a single relay to participate in the communication between the source and the destination in each transmission slot. This selection is based on the channel state information (CSI) obtained either from all or from some of the FSO links. Thus, the need for synchronizing the relays' transmissions is avoided and the slowly varying nature of the atmospheric channel is exploited. For both relay selection and all-active relaying, novel closed-form expressions for their outage performance are derived, assuming the versatile Gamma-Gamma channel model. Furthermore, based on the derived analytical results, the problem of allocating the optical power resources to the FSO links is addressed, ...

  4. Tracking and data relay satellite system configuration and tradeoff study. Volume 4: TDRS system operation and control and telecommunications service system, part 1

    Science.gov (United States)

    1972-01-01

    Major study areas treated in this volume are: 1) operations and control and 2) the telecommunication service system. The TDRS orbit selection, orbital deployment, ground station visibility, sequence of events from launch to final orbit position, and TDRS control center functions required for stationkeeping, repositioning, attitude control, and antenna pointing are briefly treated as part of the operations and control section. The last topic of this section concerns the operations required for efficiently providing the TDRSS user telecommunication services. The discussion treats functions of the GSFC control and data processing facility, ground station, and TDRS control center. The second major portion of this volume deals with the Telecommunication Service System (TSS) which consists of the ground station, TDRS communication equipment and the user transceiver. A summary of the requirements and objectives for the telecommunication services and a brief summary of the TSS capabilities is followed by communication system analysis, signal design, and equipment design. Finally, descriptions of the three TSS elements are presented.

  5. Outage performance of two-way DF relaying systems with a new relay selection metric

    KAUST Repository

    Hyadi, Amal

    2012-04-01

    This paper investigates a new constrained relay selection scheme for two-way relaying systems where two end terminals communicate simultaneously via a relay. The introduced technique is based on the maximization of the weighted sum rate of both users. To evaluate the performance of the proposed system, the outage probability is derived in a general case (where an arbitrary channel is considered), and then over independently but not necessarily identically distributed (i.n.i.d.) Rayleigh fading channels. The analytical results are verified through simulations. © 2012 IEEE.

  6. Power supply devices and systems of relay protection

    CERN Document Server

    Gurevich, Vladimir

    2013-01-01

    Power Supply Devices and Systems of Relay Protection brings relay protection and electrical power engineers a single, concentrated source of information on auxiliary power supply systems and devices. The book also tackles specific problems and solutions of relay protection power supply systems and devices, which are often not dealt with in the literature. The author, an experienced engineer with more than 100 patents, draws on his own experience to offer practical, tested advice to readers. A Guide to Relay Protection Power Supply for Engineers and Technicians The first chapter reviews the ele

  7. G. Marconi: A Data Relay Satellite for Mars Communications

    Science.gov (United States)

    Dionisio, C.; Marcozzi, M.; Landriani, C.

    2002-01-01

    Mars has always been a source of intrigue and fascination. Recent scientific discoveries have stimulated this longstanding interest, leading to a renaissance in Mars exploration. Future missions to Mars will be capable of long-distance surface mobility, hyperspectral imaging, subsurface exploration, and even life-detection. Manned missions and, eventually, colonies may follow. No mission to the Red Planet stands alone. New scientific and technological knowledge is passed on from one mission to the next, not only improving the journey into space, but also providing benefits here on Earth. The Mars Relay Network, an international constellation of Mars orbiters with relay radios, directly supports other Mars missions by relaying communications between robotic vehicles at Mars and ground stations on Earth. The ability of robotic visitors from Earth to explore Mars will take a gigantic leap forward in 2007 with the launch of the Guglielmo Marconi Orbiter (GMO), the first spacecraft primarily dedicated to providing communication relay, navigation and timing services at Mars. GMO will be the preeminent node of the Mars Relay Network. GMO will relay communications between Earth and robotic vehicles near Mars. GMO will also provide navigation services to spacecraft approaching Mars. GMO will receive transmissions from ground stations on Earth at X-band and will transmit to ground stations on Earth at X- and Ka-bands. GMO will transmit to robotic vehicles at Mars at UHF and receive from these vehicles at UHF and X-band. GMO's baseline 4450 km circular orbit provides complete coverage of the planet for telecommunication and navigation support. GMO will arrive at Mars in mid-2008, just before the NetLander and Mars Scout missions that will be its first users. GMO is designed for a nominal operating lifetime of 10 years and will support nominal commanding and data acquisition, as well as mission critical events such as Mars Orbit Insertion, Entry, Descent and Landing, and Mars

  8. Beamforming Design for Coordinated Direct and Relay Systems

    DEFF Research Database (Denmark)

    Sun, Fan; De Carvalho, Elisabeth; Thai, Chan

    2012-01-01

    Joint processing of multiple communication flows in wireless systems has given rise to a number of novel transmission techniques, notably the two-way relaying based on wireless network coding. Recently, a related set of techniques has emerged, termed coordinated direct and relay (CDR) transmissions......, where the constellation of traffic flows is more general than the two-way. Regardless of the actual traffic flows, in a CDR scheme the relay has a central role in managing the interference. In this paper we investigate the novel transmission modes, based on amplify-and-forward, that arise when the relay...

  9. Relay protection coordination with generator capability curve, excitation system limiters and power system relay protections settings

    Directory of Open Access Journals (Sweden)

    Buha Danilo

    2016-01-01

    Full Text Available The relay protection settings performed in the largest thermal powerplant (TE "Nikola Tesla B" are reffered and explained in this paper. The first calculation step is related to the coordination of the maximum stator current limiter settings, the overcurrent protection with inverse characteristics settings and the permitted overload of the generator stator B1. In the second calculation step the settings of impedance generator protection are determined, and the methods and criteria according to which the calculations are done are described. Criteria used to provide the protection to fulfill the backup protection role in the event of malfunction of the main protection of the transmission system. are clarified. The calculation of all protection functions (32 functions of generator B1 were performed in the project "Coordination of relay protection blocks B1 and B2 with the system of excitation and power system protections -TENT B".

  10. Tracking and Data Relay Satellite (TDRS) Orbit Estimation Using an Extended Kalman Filter

    Science.gov (United States)

    Ward, Douglas T.; Dang, Ket D.; Slojkowski, Steve; Blizzard, Mike; Jenkins, Greg

    2007-01-01

    Alternatives to the Tracking and Data Relay Satellite (TDRS) orbit estimation procedure were studied to develop a technique that both produces more reliable results and is more amenable to automation than the prior procedure. The Earth Observing System (EOS) Terra mission has TDRS ephemeris prediction 3(sigma) requirements of 75 meters in position and 5.5 millimeters per second in velocity over a 1.5-day prediction span. Meeting these requirements sometimes required reruns of the prior orbit determination (OD) process, with manual editing of tracking data to get an acceptable solution. After a study of the available alternatives, the Flight Dynamics Facility (FDF) began using the Real-Time Orbit Determination (RTOD(Registered TradeMark)) Kalman filter program for operational support of TDRSs in February 2007. This extended Kalman filter (EKF) is used for daily support, including within hours after most thrusting, to estimate the spacecraft position, velocity, and solar radiation coefficient of reflectivity (C(sub R)). The tracking data used are from the Bilateration Ranging Transponder System (BRTS), selected TDRS System (TDRSS) User satellite tracking data, and Telemetry, Tracking, and Command (TT&C) data. Degraded filter results right after maneuvers and some momentum unloads provided incentive for a hybrid OD technique. The results of combining EKF strengths with the Goddard Trajectory Determination System (GTDS) Differential Correction (DC) program batch-least-squares solutions, as recommended in a 2005 paper on the chain-bias technique, are also presented.

  11. Cognitive Spectrum Efficient Multiple Access Technique using Relay Systems

    DEFF Research Database (Denmark)

    Frederiksen, Flemming Bjerge; Prasad, Ramjee

    2007-01-01

    Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context will be presented and discussed in this paper. Ideas to increase the coverage of cellular systems by relay channels, relay stations and collaborate ra...

  12. Cognitive Spectrum Efficient Multiple Access Technique using Relay Systems

    DEFF Research Database (Denmark)

    Frederiksen, Flemming Bjerge; Prasad, Ramjee

    2007-01-01

    Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context will be presented and discussed in this paper. Ideas to increase the coverage of cellular systems by relay channels, relay stations and collaborate...

  13. Relay-and-antenna selection and digital transceiver design for two-way AF-MIMO multiple-relay systems

    Science.gov (United States)

    Hu, Chia-Chang; Su, Hao-Hsian; Tang, Kang-Tsao

    2014-09-01

    This paper considers a two-way multiple-input multiple-output (MIMO) relaying system with multiple relays between two terminals nodes. The relay antenna selection scheme based on channel singular valued decomposition (SVD) is used to reduce energy consumption. To enhance the system performance, we apply a SVD-based algorithm with MSE criterion which calculates optimal linear transceivers precoding jointly at the source nodes and relay nodes for amplify-and-forward (AF) protocols. In computer simulations, we use an iteration method to compute the non-convex function of joint source and relays power allocation. The simulation results show the SVD-based precoding design with SVD-based relay and antenna selection scheme can achieve a superior system bit error rate (BER) performance and reduce the power consume of relay antennas.

  14. Performance evaluation of the fixed relay in OFDMA systems

    Institute of Scientific and Technical Information of China (English)

    Gao Peng; Wu Xiaoyan; Meng Dexiang; Chen Yanming; Tu Guofang

    2010-01-01

    Performance of fixed relays in orthogonal frequency division multiple access (OFDMA) systems, especially the coverage and capacity performance at the cell edge, is evaluated in this paper.Two methods, theoretical analysis and calculation and Monte Carlo simulation, are used for the evaluations.By theoretical analysis and calculation, frequency efficiency equation of a relay is introduced and numerical results are calculated.Monte Carlo simulation results also verify that the calculation method is reasonable.The evaluation shows that a relay can increase system performance to a certain level if it is designed appropriately, otherwise it will be harmful for the system performance, even to reduce it.

  15. User RF requirements for a Ka-band data relay satellite link

    Science.gov (United States)

    Copeland, David J.; Aleman, Roberto M.

    1989-01-01

    The user G/T and EIRP requirements were determined for a data relay satellite link consisting of a forward link to 360 Mbps at 23 GHz and a return link to 2 Gbps at 26.5 GHz. Hardware for this data link would be a modular expansion to the NASA Data Link Module. Calculations were based on a data relay satellite model of predetermined characteristics patterned after the NASA Tracking and Data Relay Satellite (TDRS). The desired data rates could be achieved with a G/T of 21.7 dB/deg K (forward link) and an EIRP of 68.2 dBW (return link) for the user satellite. Hardware configurations meeting these requirements are discussed in terms of RF performance, efficiency, reliability, and modular flexibility. A planar array configuration emerges as the logical candidate for most NASA missions. Pertinent Ka-band technology and certain ongoing research efforts are reviewed. Areas of particular interest include new power device families, 0.25-micron low-noise HEMT technology, and fiber optic distribution and control of RF arrays.

  16. Sum-Rate Maximization of Coordinated Direct and Relay Systems

    DEFF Research Database (Denmark)

    Sun, Fan; Popovski, Petar; Thai, Chan

    2012-01-01

    Joint processing of multiple communication flows in wireless systems has given rise to a number of novel transmission techniques, notably the two-way relaying based on wireless network coding. Recently, a related set of techniques has emerged, termed coordinated direct and relay (CDR) transmissions......, where the constellation of traffic flows is more general than the two-way. Regardless of the actual traffic flows, in a CDR scheme the relay has a central role in managing the interference and boosting the overall system performance. In this paper we investigate the novel transmission modes, based...

  17. The Laser Communications Relay and the Path to the Next Generation Near Earth Relay

    Science.gov (United States)

    Israel, David J.

    2015-01-01

    NASA Goddard Space Flight Center is currently developing the Laser Communications Relay Demonstration (LCRD) as a Path to the Next Generation Near Earth Space Communication Network. The current NASA Space Network or Tracking and Data Relay Satellite System is comprised of a constellation of Tracking and Data Relay Satellites (TDRS) in geosynchronous orbit and associated ground stations and operation centers. NASA is currently targeting a next generation of relay capability on orbit in the 2025 timeframe.

  18. Overlay cognitive radio systems with adaptive two-way relaying

    KAUST Repository

    Hyadi, Amal

    2013-12-01

    In this paper, we propose a spectrum sharing mechanism with a two-phase two-way relaying protocol for an overlay cognitive network. The system comprises two primary users (PUs) and two secondary users (SUs). One of the SUs acts as a relay for the PUs and gains spectrum sharing as long as he respects outage probability constraints of the primary system. Moreover, we consider that the relaying node performs an optimal power allocation scheme that minimizes the outage performance of the secondary receiver. Closed form expressions for the outage probability are derived for the cases of Decode-and-Forward (DF), Amplify-and-Forward (AF), and adaptive relaying. Numerical simulations are presented to illustrate and compare the obtained results. © 2013 IEEE.

  19. Educational Software Tool for Protection System Engineers. Distance Relay

    Directory of Open Access Journals (Sweden)

    Trujillo-Guajardo L.A.

    2012-04-01

    Full Text Available In this article, a graphical software tool is presented; this tool is based on the education of protection system engineers. The theoretical fundaments used for the design of operation characteristics of distance relays and their algorithms are presented. The software allows the evaluation and analysis of real time events or simulated ones of every stage of design of the distance relay. Some example cases are presented to illustrate the activities that could be done with the graphical software tool developed.

  20. Conceptual Design of a Communications Relay Satellite for a Lunar Sample Return Mission

    Science.gov (United States)

    Brunner, Christopher W.

    2005-01-01

    In 2003, NASA solicited proposals for a robotic exploration of the lunar surface. Submissions were requested for a lunar sample return mission from the South Pole-Aitken Basin. The basin is of interest because it is thought to contain some of the oldest accessible rocks on the lunar surface. A mission is under study that will land a spacecraft in the basin, collect a sample of rock fragments, and return the sample to Earth. Because the Aitken Basin is on the far side of the Moon, the lander will require a communications relay satellite (CRS) to maintain contact with the Earth during its surface operation. Design of the CRS's orbit is therefore critical. This paper describes a mission design which includes potential transfer and mission orbits, required changes in velocity, orbital parameters, and mission dates. Several different low lunar polar orbits are examined to compare their availability to the lander versus the distance over which they must communicate. In addition, polar orbits are compared to a halo orbit about the Earth-Moon L2 point, which would permit continuous communication at a cost of increased fuel requirements and longer transmission distances. This thesis also examines some general parameters of the spacecraft systems for the mission under study. Mission requirements for the lander dictate the eventual choice of mission orbit. This mission could be the first step in a period of renewed lunar exploration and eventual human landings.

  1. Technical Note: Animal-borne CTD-Satellite Relay Data Loggers for real-time oceanographic data collection

    Directory of Open Access Journals (Sweden)

    L. Boehme

    2009-06-01

    Full Text Available The increasing need for continuous monitoring of the world oceans has stimulated the development of a range of autonomous sampling platforms. One novel addition to these approaches is a small, relatively inexpensive data-relaying device that can be deployed on marine mammals to provide vertical oceanographic profiles throughout the upper 2000 m of the water column. When an animal dives, the CTD-Satellite Relay Data Logger (CTD-SRDL records vertical profiles of temperature, conductivity and pressure. Data are compressed once the animal returns to the surface where it is located by, and relays data to, the Argos satellite system. The technical challenges met in the design of the CTD-SRDL are the maximising of energy efficiency by minimising size, whilst simultaneously maintaining the reliability of an instrument that cannot be recovered and is required to survive its lifetime attached to a marine mammal. The CTD-SRDLs record temperature and salinity with an accuracy of better than 0.005°C and 0.02 respectively. However, due to the limited availability of reference data for post-processing, data are often associated with slightly higher errors. The potential to collect large numbers of profiles cost-effectively makes data collection using CTD-SRDL technology particularly beneficial in regions where traditional oceanographic measurements are scarce. Depending on the CTD-SRDL configuration, it is possible to sample and transmit hydrographic profiles on a daily basis, providing valuable and often unique information for a real-time ocean observing system.

  2. Decode and Zero-Forcing Forward Relaying with Relay Selection in Cognitive Radio Systems

    KAUST Repository

    Park, Kihong

    2014-05-01

    In this paper, we investigate a cognitive radio (CR) relay network with multiple relay nodes that help forwarding the signal of CR users. Best relay selection is considered to take advantage of its low complexity of implementation. When the primary user (PU) is located close to the relay nodes, the performance of the secondary network is severely degraded due to the interference power constraint during the transmission in the second hop. We propose a decode and zero-forcing forward scheme to suppress the interference power at the relay nodes and analyze the statistics of the end-to-end signal-to-noise ratio when the relay nodes are located arbitrarily and experience therefore non-identical Rayleigh fading channels. Numerical results validate our theoretical results and show that our proposed scheme improves the performance of the CR network when the PU is close to the relay nodes. © 2014 IEEE.

  3. Four-Way Relaying in Wireless Cellular Systems

    DEFF Research Database (Denmark)

    Liu, Huaping; Popovski, Petar; De Carvalho, Elisabeth

    2013-01-01

    Two-way relaying in wireless systems has initiated a large research effort during the past few years. Nevertheless, it represents only a specific traffic pattern and it is of interest to investigate other traffic patterns where such a simultaneous processing of information flows can bring...

  4. ESA Earth terminals in the European data relay system

    Science.gov (United States)

    Beck, T.

    1991-10-01

    The projected ESA earth terminal which will be the main traffic stations for the space/ground communications via the European Data Relay System (DRS) are considered. The major station and subsystem characteristics of these terminals as derived during the detailed definition phase by European industry are described.

  5. An advanced OBP-based payload operating in an asynchronous network for future data relay satellites utilising CCSDS-standard data structures

    Science.gov (United States)

    Grant, M.; Vernucci, A.

    1991-01-01

    A possible Data Relay Satellite System (DRSS) topology and network architecture is introduced. An asynchronous network concept, whereby each link (Inter-orbit, Inter-satellite, Feeder) is allowed to operate on its own clock, without causing loss of information, in conjunction with packet data structures, such as those specified by the CCSDS for advanced orbiting systems is discussed. A matching OBP payload architecture is described, highlighting the advantages provided by the OBP-based concept and then giving some indications on the OBP mass/power requirements.

  6. Power optimization for maximum channel capacity in MIMO relay system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Introducing multiple-input multiple-output (MIMO) relay channel could offer significant capacity gain.And it is of great importance to develop effective power allocation strategies to achieve power efficiency and improve channel capacity in amplify-and-forward relay system.This article investigates a two-hop MIMO relay system with multiple antennas in relay node (RN) and receiver (RX).Maximizing capacity with antenna selection (MCAS) and maximizing capacity with eigen-decomposition (MCED) schemes are proposed to efficiently allocate power among antennas in RN under first and second hop limited scenarios.The analysis and simulation results show that both MCED and MCAS can improve the channel capacity compared with uniform power allocation (UPA) scheme in most of the studied areas.The MCAS bears comparison with MCED with an acceptable capacity loss, but lowers the complexity by saving channel state information (CSI) feedback to the transmitter (TX).Moreover, when the RN is close to RX, the performance of UPA is also close to the upper bound as the performance of first hop is limited.

  7. Cooperative AF Relaying in Spectrum-Sharing Systems: Outage Probability Analysis under Co-Channel Interferences and Relay Selection

    KAUST Repository

    Xia, Minghua

    2012-11-01

    For cooperative amplify-and-forward (AF) relaying in spectrum-sharing wireless systems, secondary users share spectrum resources originally licensed to primary users to communicate with each other and, thus, the transmit power of secondary transmitters is strictly limited by the tolerable interference powers at primary receivers. Furthermore, the received signals at a relay and at a secondary receiver are inevitably interfered by the signals from primary transmitters. These co-channel interferences (CCIs) from concurrent primary transmission can significantly degrade the performance of secondary transmission. This paper studies the effect of CCIs on outage probability of the secondary link in a spectrum-sharing environment. In particular, in order to compensate the performance loss due to CCIs, the transmit powers of a secondary transmitter and its relaying node are respectively optimized with respect to both the tolerable interference powers at the primary receivers and the CCIs from the primary transmitters. Moreover, when multiple relays are available, the technique of opportunistic relay selection is exploited to further improve system performance with low implementation complexity. By analyzing lower and upper bounds on the outage probability of the secondary system, this study reveals that it is the tolerable interference powers at primary receivers that dominate the system performance, rather than the CCIs from primary transmitters. System designers will benefit from this result in planning and designing next-generation broadband spectrum-sharing systems.

  8. Physical-Layer Security of a Buffer-Aided Full-Duplex Relaying System

    KAUST Repository

    El Shafie, Ahmed

    2016-07-07

    This letter proposes a novel hybrid half-/full-duplex relaying scheme to enhance the relay channel security. A source node (Alice) communicates with her destination node (Bob) in the presence of a buffer-aided full-duplex relay node (Rooney) and a potential eavesdropper (Eve). Rooney adopts two different relaying, namely randomize-and-forward and decode-andforward relaying strategies, to improve the security of the legitimate system. In the first relaying strategy, Rooney uses a codebook different from that used at Alice. In the second relaying strategy, Rooney and Alice use the same codebooks. In addition, Rooney switches between half-duplex and full-duplex modes to further enhance the security of the legitimate system. The numerical results demonstrate that our proposed scheme achieves a significant average secrecy end-to-end throughput improvement relative to the conventional bufferless full-duplex relaying scheme.

  9. Earth Orbiting Support Systems for commercial low Earth orbit data relay: Assessing architectures through tradespace exploration

    Science.gov (United States)

    Palermo, Gianluca; Golkar, Alessandro; Gaudenzi, Paolo

    2015-06-01

    As small satellites and Sun Synchronous Earth Observation systems are assuming an increased role in nowadays space activities, including commercial investments, it is of interest to assess how infrastructures could be developed to support the development of such systems and other spacecraft that could benefit from having a data relay service in Low Earth Orbit (LEO), as opposed to traditional Geostationary relays. This paper presents a tradespace exploration study of the architecture of such LEO commercial satellite data relay systems, here defined as Earth Orbiting Support Systems (EOSS). The paper proposes a methodology to formulate architectural decisions for EOSS constellations, and enumerate the corresponding tradespace of feasible architectures. Evaluation metrics are proposed to measure benefits and costs of architectures; lastly, a multicriteria Pareto criterion is used to downselect optimal architectures for subsequent analysis. The methodology is applied to two case studies for a set of 30 and 100 customer-spacecraft respectively, representing potential markets for LEO services in Exploration, Earth Observation, Science, and CubeSats. Pareto analysis shows how increased performance of the constellation is always achieved by an increased node size, as measured by the gain of the communications antenna mounted on EOSS spacecraft. On the other hand, nonlinear trends in optimal orbital altitude, number of satellites per plane, and number of orbital planes, are found in both cases. An upward trend in individual node memory capacity is found, although never exceeding 256 Gbits of onboard memory for both cases that have been considered, assuming the availability of a polar ground station for EOSS data downlink. System architects can use the proposed methodology to identify optimal EOSS constellations for a given service pricing strategy and customer target, thus identifying alternatives for selection by decision makers.

  10. Interference alignment for degrees of freedom improvement in 3-relay half-duplex systems

    KAUST Repository

    Park, Seongho

    2011-12-01

    In a half-duplex relaying, the capacity pre-log factor is a major drawback in spectral efficiency. This paper proposes a linear precoding scheme and an alternate relaying protocol in a dual-hop half-duplex system where three relays help the communication between the source and the destination. In our proposed scheme, we consider a phase incoherent method in relays in which the source alternately transmits message signals to the different relays. In addition, we propose a linear interference alignment scheme which can eliminate the inter-relay interference resulted from the phase incoherence of relaying. Based on our analysis of degrees of freedom and our simulation results, we show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying. © 2011 IEEE.

  11. Network coding and its applications to satellite systems

    DEFF Research Database (Denmark)

    Vieira, Fausto; Roetter, Daniel Enrique Lucani

    2015-01-01

    Network coding has its roots in information theory where it was initially proposed as a way to improve a two-node communication using a (broadcasting) relay. For this theoretical construct, a satellite communications system was proposed as an illustrative example, where the relay node would...... be a satellite covering the two nodes. The benefits in terms of throughput, resilience, and flexibility of network coding are quite relevant for wireless networks in general, and for satellite systems in particular. This chapter presents some of the basics in network coding, as well as an overview of specific...... scenarios where network coding provides a significant improvement compared to existing solutions, for example, in broadcast and multicast satellite networks, hybrid satellite-terrestrial networks, and broadband multibeam satellites. The chapter also compares coding perspectives and revisits the layered...

  12. Network coding and its applications to satellite systems

    DEFF Research Database (Denmark)

    Vieira, Fausto; Roetter, Daniel Enrique Lucani

    2015-01-01

    Network coding has its roots in information theory where it was initially proposed as a way to improve a two-node communication using a (broadcasting) relay. For this theoretical construct, a satellite communications system was proposed as an illustrative example, where the relay node would...... be a satellite covering the two nodes. The benefits in terms of throughput, resilience, and flexibility of network coding are quite relevant for wireless networks in general, and for satellite systems in particular. This chapter presents some of the basics in network coding, as well as an overview of specific...... scenarios where network coding provides a significant improvement compared to existing solutions, for example, in broadcast and multicast satellite networks, hybrid satellite-terrestrial networks, and broadband multibeam satellites. The chapter also compares coding perspectives and revisits the layered...

  13. Cooperative HARQ protocol and diversity analysis of systems with multiple incremental relays

    Institute of Scientific and Technical Information of China (English)

    FAN Bin; WANG Wen-bo; LIN Yi-cheng; ZHENG Kan

    2009-01-01

    Wireless networks contain an inherent distributed spatial diversity that can be exploited by relays. Relay networks can take advantage of the broadcast-oriented nature of wireless transmission, but require more radio resource to transmit data for their multi-hop traits. Fortunately, incremental relaying technique, which can choose direct or multi-hop transmission adaptively, can efficiently utilize resource. In this article, the incremental transmission with amplify-and-forward (AF) relays is focused on. A practical hybrid-automatic retransmission request (HARQ) protocol is designed, and the related optimal relay selection strategy is proposed. To analyze the cooperative diversity of system with the proposed protocol, the capacity lower bound is deduced. Simulation and analytical results indicate that by adopting the optimal relay selection strategy, the system with the proposed HARQ protocol can achieve an order of cooperative diversity that equals the aggregated number of the relay and source nodes.

  14. TYCHO: Demonstrator and operational satellite mission to Earth-Moon-Libration point EML-4 for communication relay provision as a service

    Science.gov (United States)

    Hornig, Andreas; Homeister, Maren

    2015-03-01

    In the current wake of mission plans to the Moon and to Earth-Moon Libration points (EML) by several agencies and organizations, TYCHO identifies the key role of telecommunication provision for the future path of lunar exploration. It demonstrates an interesting extension to existing communication methods to the Moon and beyond by combining innovative technology with a next frontier location and the commercial space communication sector. It is evident that all communication systems will rely on direct communication to Earth ground stations. In case of EML-2 missions around HALO orbits or bases on the far side of the Moon, it has to be extended by communication links via relay stations. The innovative approach is that TYCHO provides this relay communication to those out-of-sight lunar missions as a service. TYCHO will establish a new infrastructure for future missions and even create a new market for add-on relay services. The TMA-0 satellite is TYCHO's first phase and a proposed demonstrator mission to the Earth-Moon Libration point EML-4. It demonstrates relay services needed for automated exploratory and manned missions (Moon bases) on the rim (>90°E and >90°W) and far side surface, to lunar orbits and even to EML-2 halo orbits (satellites and space stations). Its main advantage is the permanent availability of communication coverage. This will provide full access to scientific and telemetry data and furthermore to crucial medical monitoring and safety. The communication subsystem is a platform for conventional communication but also a test-bed for optical communication with high data-rate LASER links to serve the future needs of manned bases and periodic burst data-transfer from lunar poles. The operational TMA-1 satellite is a stand-alone mission integrated into existing space communication networks to provide open communication service to external lunar missions. Therefore the long-time stable libration points EML-4 and -5 are selected to guarantee an

  15. Detecting relay attacks on RFID communication systems using quantum bits

    Science.gov (United States)

    Jannati, Hoda; Ardeshir-Larijani, Ebrahim

    2016-08-01

    RFID systems became widespread in variety of applications because of their simplicity in manufacturing and usability. In the province of critical infrastructure protection, RFID systems are usually employed to identify and track people, objects and vehicles that enter restricted areas. The most important vulnerability which is prevalent among all protocols employed in RFID systems is against relay attacks. Until now, to protect RFID systems against this kind of attack, the only approach is the utilization of distance-bounding protocols which are not applicable over low-cost devices such as RFID passive tags. This work presents a novel technique using emerging quantum technologies to detect relay attacks on RFID systems. Recently, it is demonstrated that quantum key distribution (QKD) can be implemented in a client-server scheme where client only requires an on-chip polarization rotator that may be integrated into a handheld device. Now we present our technique for a tag-reader scenario which needs similar resources as the mentioned QKD scheme. We argue that our technique requires less resources and provides lower probability of false alarm for the system, compared with distance-bounding protocols, and may pave the way to enhance the security of current RFID systems.

  16. Detecting relay attacks on RFID communication systems using quantum bits

    Science.gov (United States)

    Jannati, Hoda; Ardeshir-Larijani, Ebrahim

    2016-11-01

    RFID systems became widespread in variety of applications because of their simplicity in manufacturing and usability. In the province of critical infrastructure protection, RFID systems are usually employed to identify and track people, objects and vehicles that enter restricted areas. The most important vulnerability which is prevalent among all protocols employed in RFID systems is against relay attacks. Until now, to protect RFID systems against this kind of attack, the only approach is the utilization of distance-bounding protocols which are not applicable over low-cost devices such as RFID passive tags. This work presents a novel technique using emerging quantum technologies to detect relay attacks on RFID systems. Recently, it is demonstrated that quantum key distribution (QKD) can be implemented in a client-server scheme where client only requires an on-chip polarization rotator that may be integrated into a handheld device. Now we present our technique for a tag-reader scenario which needs similar resources as the mentioned QKD scheme. We argue that our technique requires less resources and provides lower probability of false alarm for the system, compared with distance-bounding protocols, and may pave the way to enhance the security of current RFID systems.

  17. Real-Time Multimission Event Notification System for Mars Relay

    Science.gov (United States)

    Wallick, Michael N.; Allard, Daniel A.; Gladden, Roy E.; Wang, Paul; Hy, Franklin H.

    2013-01-01

    As the Mars Relay Network is in constant flux (missions and teams going through their daily workflow), it is imperative that users are aware of such state changes. For example, a change by an orbiter team can affect operations on a lander team. This software provides an ambient view of the real-time status of the Mars network. The Mars Relay Operations Service (MaROS) comprises a number of tools to coordinate, plan, and visualize various aspects of the Mars Relay Network. As part of MaROS, a feature set was developed that operates on several levels of the software architecture. These levels include a Web-based user interface, a back-end "ReSTlet" built in Java, and databases that store the data as it is received from the network. The result is a real-time event notification and management system, so mission teams can track and act upon events on a moment-by-moment basis. This software retrieves events from MaROS and displays them to the end user. Updates happen in real time, i.e., messages are pushed to the user while logged into the system, and queued when the user is not online for later viewing. The software does not do away with the email notifications, but augments them with in-line notifications. Further, this software expands the events that can generate a notification, and allows user-generated notifications. Existing software sends a smaller subset of mission-generated notifications via email. A common complaint of users was that the system-generated e-mails often "get lost" with other e-mail that comes in. This software allows for an expanded set (including user-generated) of notifications displayed in-line of the program. By separating notifications, this can improve a user's workflow.

  18. Initial Design and Concept of Operations for a Clandestine Data Relay UUV To Circumvent Jungle Canopy Effects on Satellite Communications

    Science.gov (United States)

    2011-09-01

    18 Grant Ehrlich, "Lithium-Ion Batteries ," In Handbook of Batteries (Third Edition), ed. D. Linden and T. Reddy, (New York: McGraw...Ehrlich, Grant. "Lithium-Ion Batteries ." In Handbook of Batteries (Third Edition), edited by D. Linden and T. Reddy, 35.1–35.94, New York...Concept of Operations for a Clandestine Data Relay UUV To Circumvent Jungle Canopy Effects on Satellite Communications 6. AUTHOR( S ) Michael G.Tyree

  19. The adaptive optics and transmit system for NASA's Laser Communications Relay Demonstration project

    Science.gov (United States)

    Roberts, Lewis C.; Burruss, Rick; Fregoso, Santos; Herzog, Harrison; Piazzola, Sabino; Roberts, Jennifer E.; Spiers, Gary D.; Truong, Tuan N.

    2016-09-01

    The Laser Communication Relay Demonstration is NASA's multi-year demonstration of laser communication to a geosynchronous satellite. We are currently assembling the optical system for the first of the two baseline ground stations. The optical system consists of an adaptive optics system, the transmit system and a camera for target acquisition. The adaptive optics system is responsible for compensating the downlink beam for atmospheric turbulence and coupling it into the modem's single mode fiber. The adaptive optics system is a woofer/tweeter design, with one deformable mirror correcting for low spatial frequencies with large amplitude and a second deformable mirror correcting for high spatial frequencies with small amplitude. The system uses a Shack- Hartmann wavefront sensor. The transmit system relays four beacon beams and one communication laser to the telescope for propagation to the space terminal. Both the uplink and downlink beams are centered at 1.55 microns. We present an overview of the design of the system as well as performance predictions including time series of coupling efficiency and expected uplink beam quality.

  20. Uplink Power Saving Potential of Cellular System with Fixed Relays

    Institute of Scientific and Technical Information of China (English)

    SHI Hong-kui; RONG Meng-tian; LIU Tao; YU Dan

    2007-01-01

    This paper presented a scheme of relayed cellular mobile telecommunication network, which only employs fixed digital relays and not more than two-hop relay routes. Power saving potential of the network is deeply studied under the assumption of not occupying additional frequency bands (i. e. relays share the same frequency bands as used by the base stations). Theoretical analysis and simulation results have both shown that, with the same radio coverage requirement, the necessary effective transmission powers in such a relayed network have greatly decreased compared to conventional cellular network.

  1. Line Differential Protection Scheme Modelling for Underground 420 kV Cable Systems, EMTDC/PSCAD Relays Modelling

    DEFF Research Database (Denmark)

    Bak, Claus Leth; Sztykiel, Michal; Dollerup, Sebastian

    2011-01-01

    Based on the analysis of a specific relay model and an HVAC (High Voltage Alternating Current) cable system, a new approach to EMTDC/PSCAD modelling of protective relays is presented. Such approach allows creating complex and accurate relay models derived from the original algorithms. Relay model...

  2. Real-time, Near Global, Low Earth Orbit Communications using Geostationary Inmarsat BGAN System as a Relay

    OpenAIRE

    Lenz, Christian; McCormick, Chris; Goldsmith, Rob; Trachtman, Eyal

    2010-01-01

    This paper describes a new service and related communications hardware that provides continuous, near global access to and from Leo Spacecraft utilizing the existing geostationary INMARSAT BGAN Satellite System as a data relay. This new communications link for LEO platforms will provide full duplex data rates from as low as 100kbps up to 475kbps with near-real time latencies and near global coverage. A team of Broad Reach Engineering (US), COM DEV Europe (UK), and INMARSAT (UK) is developing ...

  3. Polar On-Line Acquisition Relay and Transmission System (POLARATS)

    Energy Technology Data Exchange (ETDEWEB)

    Yuracko, K.

    2004-07-15

    POLARATS (Polar On-Line Acquisition Relay And Transmission System) is being developed by YAHSGS LLC (YAHSGS) and Oak Ridge National Laboratory (ORNL) to provide remote, unattended monitoring of environmental parameters under harsh environmental conditions. In particular, instrumental design and engineering is oriented towards protection of human health in the Arctic, and with the additional goal of advancing Arctic education and research. POLARATS will obtain and transmit environmental data from hardened monitoring devices deployed in locations important to understanding atmospheric and aquatic pollutant migration as it is biomagnified in Arctic food chains. An Internet- and personal computer (PC)-based educational module will provide real time sensor data, on-line educational content, and will be integrated with workbooks and textbooks for use in middle and high school science programs. The educational elements of POLARATS include an Internet-based educational module that will instruct students in the use of the data and how those data fit into changing Arctic environments and food chains. POLARATS will: (1) Enable students, members of the community, and scientific researchers to monitor local environmental conditions in real time over the Internet; and (2) Provide additional educational benefits through integration with middle- and high-school science curricula. Information will be relayed from POLARATS devices to classrooms and libraries along with custom-designed POLARATS teaching materials that will be integrated into existing curricula to enhance the educational benefits realized from the information obtained.

  4. Multihop relaying and multiple antenna techniques: performance trade-offs in cellular systems

    OpenAIRE

    Jacobson Kevin; Krzymień Witold

    2011-01-01

    Abstract Two very important and active areas of wireless research are multihop relaying and multiple antenna techniques. Wireless multihop relaying can increase the aggregate network data capacity and improve coverage of cellular systems by reducing path loss, mitigating shadowing, and enabling spatial reuse. In particular, multihop relaying can improve the throughput for mobiles suffering from poor signal to interference and noise ratio at the edge of a cell and reduce cell size to increase ...

  5. Relay telescope for high power laser alignment system

    Science.gov (United States)

    Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.

    2006-09-19

    A laser system includes an optical path having an intracavity relay telescope with a telescope focal point for imaging an output of the gain medium between an image location at or near the gain medium and an image location at or near an output coupler for the laser system. A kinematic mount is provided within a vacuum chamber, and adapted to secure beam baffles near the telescope focal point. An access port on the vacuum chamber is adapted for allowing insertion and removal of the beam baffles. A first baffle formed using an alignment pinhole aperture is used during alignment of the laser system. A second tapered baffle replaces the alignment aperture during operation and acts as a far-field baffle in which off angle beams strike the baffle a grazing angle of incidence, reducing fluence levels at the impact areas.

  6. Precoder Design and Power Allocation for MIMO Cognitive Radio Two-Way Relaying Systems

    KAUST Repository

    Sboui, Lokman

    2016-08-11

    In this paper, we study a multiple-antenna two-way relaying (TWR) cognitive radio (CR) system. A space alignment (SA) technique is adopted by the secondary users (SUs) to avoid interference with the primary users (PUs). We derive the optimal power allocation that maximizes the TWR achievable SU sum- rate while respecting the total power budget and the relay power constraints. We also analyze the case in which the relay is able to optimize its gain matrix structure to enhance the SU sum-rate. In the numerical results, we quantify the sum-rate gain of using the SA in the TWR CR and we show that the SU sum-rate is very limited when the relay power is low or the PU power and its resulting interference are high. In addition, we optimize the relay gain using an iterative algorithm and compare between different relay matrix structures.

  7. Simultaneous Wireless Information and Power Transfer for MIMO Amplify-and-Forward Relay Systems

    KAUST Repository

    Benkhelifa, Fatma

    2016-01-06

    In this paper, we investigate the simultaneous wireless information and power transfer (SWIPT) for the two-hop Multiple-Input Multiple-Output (MIMO) Amplify-and-Forward (AF) relay communication systems with the multiantenna energy harvesting relay. We derive the optimal source and relay covariance matrices to characterize the achievable region between the sourcedestination rate and the harvested energy at the relay, namely Rate-Energy (R-E) region. In this context, we consider the ideal scenario where the energy harvester (EH) receiver and the information decoder (ID) receiver at the relay can simultaneously decode the information and harvest the energy at the relay. Then, we consider more practical schemes which are the power splitting (PS) and the time switching (TS) which separate the EH and ID transfer over the power domain and the time domain, respectively.

  8. Simultaneous Wireless Information and Power Transfer for Decode-and-Forward MIMO Relay Communication Systems

    KAUST Repository

    Benkhelifa, Fatma

    2015-05-01

    In this paper, we investigate the simultaneous wireless information and power transfer (SWIPT) for a decode-and-forward (DF) multiple-input multiple-output (MIMO) relay system where the relay is an energy harvesting node. We consider the ideal scenario where both the energy harvesting (EH) receiver and information decoding (ID) receiver at the relay have access to the whole received signal and its energy. The relay harvests the energy while receiving the signal from the source and uses the harvested power to forward the signal to the destination. We obtain the optimal precoders at the source and the relay to maximize the achievable throughput rate of the overall link. In the numerical results, the effect of the transmit power at the source and the position of the relay between the source and the destination on the maximum achievable rate are investigated. © 2015 IEEE.

  9. Remote infeed and arc resistance effects on distance relays settings for 9 bus WSCC system

    Science.gov (United States)

    Ulla, Irshad; Radwan, M. S.; Baharom, M. N. R.; Ahmad, H.; Luqman, H. M.; Zainal, Zainab

    2017-09-01

    This paper introduce the effects of the remote infeed and arc resistance on the distance relays settings coordination for IEEE 9-bus system and the approach to including this effect on the setting using four zones quadrilateral characteristic, the simulation has been done using MATLAB/SIMULINK program which is helpful in constricting the power system and the distance relays.

  10. The Archimedes satellite system

    Science.gov (United States)

    Taylor, Stuart C.; Shurvinton, William D.

    1992-03-01

    Archimedes is a satellite system conceived by the European Space Agency (ESA) to effectively serve the European market for Mobile Radio Services (MRS). This paper describes the requirements and technical design of the Archimedes satellite system. The underlying assumptions and trade-offs behind the design are detailed and the design is compared and contrasted against alternative design solutions, both technically and economically. A path forward for the development of the system is indicated.

  11. Cooperative joint precoding in a downlink cellular system with shared relay: Design and performance evaluation

    KAUST Repository

    Kwon, JaeWoo

    2012-10-01

    In this paper, we investigate a relay enhanced cellular system, where a relay station is located in the overlap area served by two base stations. We propose cooperative joint precoding schemes for the downlink transmission of such relay enhanced cellular system to maximize the system capacity while minimizing the interference at both the relay station and the mobile stations. We formulate the optimization problems to maximize the system capacity and design the multiuser precoding vectors at each base station and the relay station. We quantify the ergodic rate performance of the proposed multiuser precoding schemes through statistical analysis. The extensively derived ergodic expressions will facilitate the accurate performance evaluation of the proposed transmission schemes. Numerical results show that the proposed schemes can effectively cancel the interference and improve the sum rate and the outage performance for cell edge users. © 2002-2012 IEEE.

  12. Proportional fair scheduling with superposition coding in a cellular cooperative relay system

    DEFF Research Database (Denmark)

    Kaneko, Megumi; Hayashi, Kazunori; Popovski, Petar

    2013-01-01

    Many works have tackled on the problem of throughput and fairness optimization in cellular cooperative relaying systems. Considering firstly a two-user relay broadcast channel, we design a scheme based on superposition coding (SC) which maximizes the achievable sum-rate under a proportional fairn...

  13. Reliable functioning of a system of relay protection

    Energy Technology Data Exchange (ETDEWEB)

    Velicescu, C.; Ivascu, C.; Nicolaescu, A.

    1980-01-01

    An examination is made of the networks of average voltage with neutral connected to the ground through a current-limiting resistor. The reliability is determined for the relay protection of these networks.

  14. China's Meteorological Satellite Application System

    Institute of Scientific and Technical Information of China (English)

    Zhang Jiashen

    2008-01-01

    @@ China's meteorological satellite program consists of five systems,namely the satellite system,the launch vehicle system,the launch center system,TT&C and the ground application system.The satellite system consists of FengYun (FY) polar orbiting series and FY geostationary series,which are launched by LM launch vehicles from Taiyan Satellite Launch Center (TSLC) and Xichang Satellite Launch Center (XSLC) respectively.

  15. Simultaneous Wireless Information and Power Transfer for MIMO Amplify-and-Forward Relay Systems

    KAUST Repository

    Benkhelifa, Fatma

    2016-03-28

    © 2015 IEEE. In this paper, we investigate two-hop Multiple- Input Multiple-Output (MIMO) Amplify-and-Forward (AF) relay communication systems with simultaneous wireless information and power transfer (SWIPT) at the multi-antenna energy harvesting relay. We derive the optimal source and relay covariance matrices to characterize the achievable region between the source-destination rate and the harvested energy at the relay, namely Rate-Energy (R-E) region. In this context, we consider the ideal scenario where the energy harvester (EH) receiver and the information decoder (ID) receiver at the relay can simultaneously decode the information and harvest the energy at the relay. This scheme provides an outer bound for the achievable R-E region since practical energy harvesting circuits are not yet able to harvest the energy and decode the information simultaneously. Then, we consider more practical schemes which are the power splitting (PS) and the time switching (TS) proposed in [1] and which separate the EH and ID transfer over the power domain and the time domain, respectively. In our study, we derive the boundary of the achievable R- E region and we show the effect of the source transmit power, the relay transmit power and the position of the relay between the source and the destination on the achievable R-E region for the ideal scenario and the two practical schemes.

  16. Error-rate performance analysis of cooperative OFDMA system with decode-and-forward relaying

    KAUST Repository

    Fareed, Muhammad Mehboob

    2014-06-01

    In this paper, we investigate the performance of a cooperative orthogonal frequency-division multiple-access (OFDMA) system with decode-and-forward (DaF) relaying. Specifically, we derive a closed-form approximate symbol-error-rate expression and analyze the achievable diversity orders. Depending on the relay location, a diversity order up to (LSkD + 1) + σ M m = 1 min(LSkRm + 1, LR mD + 1) is available, where M is the number of relays, and LS kD + 1, LSkRm + 1, and LRmD + 1 are the lengths of channel impulse responses of source-to-destination, source-to- mth relay, and mth relay-to-destination links, respectively. Monte Carlo simulation results are also presented to confirm the analytical findings. © 2013 IEEE.

  17. Coordinated Direct and Relay Transmission with Interference Cancelation in Wireless Systems

    DEFF Research Database (Denmark)

    Thai, Chan; Popovski, Petar

    2011-01-01

    Two-way relaying schemes in wireless systems obtain throughput gain by utilizing two features (1) jointly serve two communication flows, thus implementing network coding and (2) use of information that is a priori known to cancel interference and obtain the desired signal. Based on these principles......, we propose other schemes that bring throughput gains in wireless cellular systems, where relayed and direct transmissions are carried out in coordinated way. The results show that the coordinated transmission exhibit throughput improvement similar to the two–way relaying schemes....

  18. Greedy Algorithm Applied to Relay Selection for Cooperative Communication Systems in Amplify-and-Forward Mode

    Institute of Scientific and Technical Information of China (English)

    Cheng-Ying Yang; Yi-Shan Lin; Jyh-Horng Wen

    2014-01-01

    Using a relaying system to provide spatial diversity and improve the system performance is a tendency in the wireless cooperative communications. Amplify-and-forward (AF) mode with a low complexity is easy to be implemented. Under the consideration of cooperative communication systems, the scenario includes one information source, M relay stations and N destinations. This work proposes a relay selection algorithm in the Raleigh fading channel. Based on the exhaustive search method, easily to realize, the optimal selection scheme can be found with a highly complicated calculation. In order to reduce the computational complexity, an approximate optimal solution with a greedy algorithm applied for the relay station selection is proposed. With different situations of the communication systems, the performance evaluation obtained by both the proposed algorithm and the exhaustive search algorithm are given for comparison. It shows the proposed algorithm could provide a solution approach to the optimal one.

  19. Development and Testing of a Two-UAV Communication Relay System.

    Science.gov (United States)

    Li, Boyang; Jiang, Yifan; Sun, Jingxuan; Cai, Lingfeng; Wen, Chih-Yung

    2016-10-13

    In the development of beyond-line-of-sight (BLOS) Unmanned Aerial Vehicle (UAV) systems, communication between the UAVs and the ground control station (GCS) is of critical importance. The commonly used economical wireless modules are restricted by the short communication range and are easily blocked by obstacles. The use of a communication relay system provides a practical way to solve these problems, improving the performance of UAV communication in BLOS and cross-obstacle operations. In this study, a communication relay system, in which a quadrotor was used to relay radio communication for another quadrotor was developed and tested. First, the UAVs used as the airborne platform were constructed, and the hardware for the communication relay system was selected and built up. Second, a set of software programs and protocol for autonomous mission control, communication relay control, and ground control were developed. Finally, the system was fully integrated into the airborne platform and tested both indoor and in-flight. The Received Signal Strength Indication (RSSI) and noise value in two typical application scenarios were recorded. The test results demonstrated the ability of this system to extend the communication range and build communication over obstacles. This system also shows the feasibility to coordinate multiple UAVs' communication with the same relay structure.

  20. Development and Testing of a Two-UAV Communication Relay System

    Directory of Open Access Journals (Sweden)

    Boyang Li

    2016-10-01

    Full Text Available In the development of beyond-line-of-sight (BLOS Unmanned Aerial Vehicle (UAV systems, communication between the UAVs and the ground control station (GCS is of critical importance. The commonly used economical wireless modules are restricted by the short communication range and are easily blocked by obstacles. The use of a communication relay system provides a practical way to solve these problems, improving the performance of UAV communication in BLOS and cross-obstacle operations. In this study, a communication relay system, in which a quadrotor was used to relay radio communication for another quadrotor was developed and tested. First, the UAVs used as the airborne platform were constructed, and the hardware for the communication relay system was selected and built up. Second, a set of software programs and protocol for autonomous mission control, communication relay control, and ground control were developed. Finally, the system was fully integrated into the airborne platform and tested both indoor and in-flight. The Received Signal Strength Indication (RSSI and noise value in two typical application scenarios were recorded. The test results demonstrated the ability of this system to extend the communication range and build communication over obstacles. This system also shows the feasibility to coordinate multiple UAVs’ communication with the same relay structure.

  1. The Physical Layer Security Experiments of Cooperative Communication System with Different Relay Behaviors.

    Science.gov (United States)

    Su, Yishan; Han, Guangyao; Fu, Xiaomei; Xu, Naishen; Jin, Zhigang

    2017-04-06

    Physical layer security is an attractive security mechanism, which exploits the randomness characteristics of wireless transmission channel to achieve security. However, it is hampered by the limitation of the channel condition that the main channel must be better than the eavesdropper channel. To alleviate the limitation, cooperative communication is introduced. Few studies have investigated the physical layer security of the relay transmission model. In this paper, we performed some experiments to evaluate the physical layer security of a cooperative communication system, with a relay operating in decode-and-forward (DF) cooperative mode, selfish and malicious behavior in real non-ideal transmission environment. Security performance is evaluated in terms of the probability of non-zero secrecy capacity. Experiments showed some different results compared to theoretical simulation: (1) to achieve the maximum secrecy capacity, the optimal relay power according to the experiments result is larger than that of ideal theoretical results under both cooperative and selfish behavior relay; (2) the relay in malicious behavior who forwards noise to deteriorate the main channel may deteriorate the eavesdropper channel more seriously than the main channel; (3) the optimal relay positions under cooperative and selfish behavior relay cases are both located near the destination because of non-ideal transmission.

  2. Nitrogen economy in relay intercropping systems of wheat and cotton

    NARCIS (Netherlands)

    Zhang, L.Z.; Spiertz, J.H.J.; Zhang, S.; Li, B.; Werf, van der W.

    2008-01-01

    Relay intercropping of wheat and cotton is practiced on a large scale in China. Winter wheat is thereby grown as a food crop from November to June and cotton as a cash crop from April to October. The crops overlap in time, growing as an intercrop, from April till June. High levels of nitrogen are ap

  3. Coordinated Transmissions to Direct and Relayed Users in Wireless Cellular Systems

    DEFF Research Database (Denmark)

    Thai, Chan; Popovski, Petar; Kaneko, Megumi

    2011-01-01

    The ideas of wireless network coding at the physical layer promise high throughput gains in wireless systems with relays and multi–way traffic flows. This gain can be ascribed to two principles: (1) joint transmission of multiple communication flows and (2) usage of a priori information to cancel...... the interference. In this paper we use these principles to devise new transmission schemes in wireless cellular systems that feature both users served directly by the base stations (direct users) and users served through relays (relayed users). We present four different schemes for coordinated transmission...... of uplink and downlink traffic in which one direct and one relayed user are served. These schemes are then used as building blocks in multi–user scenarios, where we present several schemes for scheduling pairs of users for coordinated transmissions. The optimal scheme involves exhaustive search of the best...

  4. Proportional fair scheduling with superposition coding in a cellular cooperative relay system

    DEFF Research Database (Denmark)

    Kaneko, Megumi; Hayashi, Kazunori; Popovski, Petar

    2013-01-01

    Many works have tackled on the problem of throughput and fairness optimization in cellular cooperative relaying systems. Considering firstly a two-user relay broadcast channel, we design a scheme based on superposition coding (SC) which maximizes the achievable sum-rate under a proportional...... fairness constraint. Unlike most relaying schemes where users are allocated orthogonally, our scheme serves the two users simultaneously on the same time-frequency resource unit by superposing their messages into three SC layers. The optimal power allocation parameters of each SC layer are derived...... by analysis. Next, we consider the general multi-user case in a cellular relay system, for which we design resource allocation algorithms based on proportional fair scheduling exploiting the proposed SC-based scheme. Numerical results show that the proposed algorithms allowing simultaneous user allocation...

  5. Coordinated Transmissions to Direct and Relayed Users in Wireless Cellular Systems

    CERN Document Server

    Thai, Chan Dai Truyen; Kaneko, Megumi; de Carvalho, Elisabeth

    2010-01-01

    The ideas of wireless network coding at the physical layer promise high throughput gains in wireless systems with relays and multi-way traffic flows. This gain can be ascribed to two principles: (1) joint transmission of multiple communication flows and (2) usage of \\emph{a priori} information to cancel the interference. In this paper we use these principles to devise new transmission schemes in wireless cellular systems that feature both users served directly by the base stations (direct users) and users served through relays (relayed users). We present four different schemes for \\emph{coordinated transmission} of uplink and downlink traffic in which one direct and one relayed user are served. These schemes are then used as building blocks in multi-user scenarios, where we present several schemes for scheduling pairs of users for coordinated transmissions. The optimal scheme involves exhaustive search of the best user pair in terms of overall rate. We propose several suboptimal scheduling schemes, which perf...

  6. Self-oscillations in dynamic systems a new methodology via two-relay controllers

    CERN Document Server

    Aguilar, Luis T; Fridman, Leonid; Iriarte, Rafael

    2015-01-01

    This monograph presents a simple and efficient two-relay control algorithm for generation of self-excited oscillations of a desired amplitude and frequency in dynamic systems. Developed by the authors, the two-relay controller consists of two relays switched by the feedback received from a linear or nonlinear system, and represents a new approach to the self-generation of periodic motions in underactuated mechanical systems. The first part of the book explains the design procedures for two-relay control using three different methodologies – the describing-function method, Poincaré maps, and the locus-of-a perturbed-relay-system method – and concludes with stability analysis of designed periodic oscillations. Two methods to ensure the robustness of two-relay control algorithms are explored in the second part, one based on the combination of the high-order sliding mode controller and backstepping, and the other on higher-order sliding-modes-based reconstruction of uncertainties and their compensation where...

  7. Joint Linear Filter Design in Multiuser Cooperative Nonregenerative MIMO Relay Systems

    Directory of Open Access Journals (Sweden)

    Li Gen

    2009-01-01

    Full Text Available This paper addresses the filter design issues for multiuser cooperative nonregenerative MIMO relay systems in both downlink and uplink scenarios. Based on the formulated signal model, the filter matrix optimization is first performed for direct path and relay path respectively, aiming to minimize the mean squared error (MSE. To be more specific, for the relay path, we derive the local optimal filter scheme at the base station and the relay station jointly in the downlink scenario along with a more practical suboptimal scheme, and then a closed-form joint local optimal solution in the uplink scenario is exploited. Furthermore, the optimal filter for the direct path is also presented by using the exiting results of conventional MIMO link. After that, several schemes are proposed for cooperative scenario to combine the signals from both paths. Numerical results show that the proposed schemes can reduce the bit error rate (BER significantly.

  8. Integrated Satellite-HAP Systems

    DEFF Research Database (Denmark)

    Cianca, Ernestina; De Sanctis, Mauro; De Luise, Aldo

    2005-01-01

    for an efficient hybrid terrestrial-satellite communication system. Two integrated HAP-satellite scenarios are presented, in which the HAP is used to overcome some of the shortcomings of satellite- based communications. Moreover, it is shown that the integration of HAPs with satellite systems can be used......Thus far, high-altitude platform (HAP)-based systems have been mainly conceived as an alternative to satellites for complementing the terrestrial network. This article aims to show that HAP should no longer be seen as a competitor technology by investors of satellites, but as a key element...

  9. Switched diversity strategies for dual-hop relaying systems

    KAUST Repository

    Gaaloul, Fakhreddine

    2011-04-29

    This paper investigates the effect of different switched diversity configurations on the implementation complexity and achieved performance of dual-hop amplify-and-forward (AF) relaying networks. A low-complexity model of the relay station is adopted, wherein single-input single-output antenna configuration is employed. Each of the transmitter and the receiver however employs multiple antennas to improve the overall link performance. Single-phase and two-phase based receive switching strategies are investigated assuming optimum first hop signal-to-noise ratio (SNR). Moreover, the simple scheme in which the switched diversity is applied independently over the two hops is studied using tight upper bounds. Thorough performance comparisons and switching thresholds optimization for the aforementioned strategies are presented. Simulation results are also provided to validate the mathematical development and to verify the numerical computations.

  10. Implementation of Pass Through PPTP Relay System with Authentication at Each Gateway and Its Performance Evaluations

    Science.gov (United States)

    Saito, Shoichi; Uehara, Tetsutaro; Izumi, Yutaka; Kunieda, Yoshitoshi

    The VPN (Virtual Private Network) technique becomes more and more popular to protect contents of messages and to achieve secure communication from incidents, such as tapping. However, it grow in usage that a VPN server is used on a sub-network in part of an office-wide network. But, a PPTP system included in Windows operating systems cannot establish nested VPN links. Moreover encrypted communication by VPN hides a user of the VPN connection. Consequently, any administrators of network systems can’t find out the users of the VPN connection via firewall, moreover can’t decide whether if the user is legal or not. In order to solve this problem, we developed a multi step PPTP relay system on a firewall. This system solves all the problems of our previously developed PPTP relay system(1). The new relay system improves security by encrypting through the whole end-to-end communication and abolishing of prior registration of passwords for the next step. Furthermore, transport speed is accelerated, and the restriction of the number of steps on relay is also abolished. By these features the multi step PPTP relay system expands usability.

  11. Efficient incremental relaying

    KAUST Repository

    Fareed, Muhammad Mehboob

    2013-07-01

    We propose a novel relaying scheme which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from destination. Our scheme capitalizes on the fact that relaying is only required when direct transmission suffers deep fading. We calculate the packet error rate for the proposed efficient incremental relaying scheme with both amplify and forward and decode and forward relaying. Numerical results are also presented to verify their analytical counterparts. © 2013 IEEE.

  12. Cooperative and cognitive satellite systems

    CERN Document Server

    Chatzinotas, Symeon; De Gaudenzi, Riccardo

    2015-01-01

    Cooperative and Cognitive Satellite Systems provides a solid overview of the current research in the field of cooperative and cognitive satellite systems, helping users understand how to incorporate state-of-the-art communication techniques in innovative satellite network architectures to enable the next generation of satellite systems. The book is edited and written by top researchers and practitioners in the field, providing a comprehensive explanation of current research that allows users to discover future technologies and their applications, integrate satellite and terrestrial systems

  13. Conceptual Design of the Adaptive Optics System for the Laser Communication Relay Demonstration Ground Station at Table Mountain

    Science.gov (United States)

    Roberts, Lewis C., Jr.; Page, Norman A.; Burruss, Rick S.; Truong, Tuan N.; Dew, Sharon; Troy, Mitchell

    2013-01-01

    The Laser Communication Relay Demonstration will feature a geostationary satellite communicating via optical links to multiple ground stations. The first ground station (GS-1) is the 1m OCTL telescope at Table Mountain in California. The optical link will utilize pulse position modulation (PPM) and differential phase shift keying (DPSK) protocols. The DPSK link necessitates that adaptive optics (AO) be used to relay the incoming beam into the single mode fiber that is the input of the modem. The GS-1 AO system will have two MEMS Deformable mirrors to achieve the needed actuator density and stroke limit. The AO system will sense the aberrations with a Shack-Hartmann wavefront sensor using the light from the communication link's 1.55 microns laser to close the loop. The system will operate day and night. The system's software will be based on heritage software from the Palm 3000 AO system, reducing risk and cost. The AO system is being designed to work at r(sub 0) greater than 3.3 cm (measured at 500 nm and zenith) and at elevations greater than 20deg above the horizon. In our worst case operating conditions we expect to achieve Strehl ratios of over 70% (at 1.55 microns), which should couple 57% of the light into the single mode DPSK fiber. This paper describes the conceptual design of the AO system, predicted performance and discusses some of the trades that were conducted during the design process.

  14. Search and rescue satellite-aided tracking system

    Science.gov (United States)

    Trudell, B.; Gutwein, J. M.; Vollmers, R.; Wammer, D.

    1980-10-01

    The objective of Sarsat is to demonstrate that satellites can greatly facilitate the monitoring, detection, and location of distress incidents alerted by Emergency Locator Transmitters (ELTs) and Emergency Position Indicating Radio Beacons (EPIRBs) carried on commercial, military, and general aviation aircraft and some marine vessels. The detection and location will be accomplished by relaying, via satellite, ELT/EPIRB distress information to ground stations, which will complete the data processing and forward alert and position location data to rescue coordination services. This paper presents a Sarsat system description and a summary of Coast Guard and USAF objectives for the initial demonstration and evaluation tests of Sarsat.

  15. Beamforming in Two-Way Fixed Gain Amplify-and-Forward Relay Systems with CCI

    CERN Document Server

    Duong, Trung Q; Zepernick, Hans-Jurgen; Yuen, Chau

    2012-01-01

    We analyze the outage performance of a two-way fixed gain amplify-and-forward (AF) relay system with beamforming, arbitrary antenna correlation, and co-channel interference (CCI). Assuming CCI at the relay, we derive the exact individual user outage probability in closed-form. Additionally, while neglecting CCI, we also investigate the system outage probability of the considered network, which is declared if any of the two users is in transmission outage. Our results indicate that in this system, the position of the relay plays an important role in determining the user as well as the system outage probability via such parameters as signal-to-noise imbalance, antenna configuration, spatial correlation, and CCI power. To render further insights into the effect of antenna correlation and CCI on the diversity and array gains, an asymptotic expression which tightly converges to exact results is also derived.

  16. Performance Analysis of Two Frequency Reuse Schemes in Fixed Relay Systems

    Institute of Scientific and Technical Information of China (English)

    HUANG Lei; RONG Meng-tian

    2007-01-01

    An upsurge of interest in relay-augmented infrastructure-based networks has appeared in recent years.Radio resource management in such relay systems has great influence on the system performance. How to utilize the limited frequency resources efficiently in the system is a hot research topic. In this paper, performance of frequency reuse schemes has been studied in fixed relay systems. A novel scheme is achieved by modifying an existing one. Theoretical model is proposed for the performance analysis of two schemes. Both the theoretical analysis and simulation results show that the modified scheme outperforms the existing one not only in power consumption of mobile stations but also in cell carrier-to-interference ratio coverage.

  17. Performance analysis of AF cooperative systems with HPA nonlinearity in semi-blind relays

    KAUST Repository

    Qi, Jian

    2012-12-01

    In this paper, dual-hop amplify-and-forward (AF) cooperative systems in the presence of high-power amplifier (HPA) nonlinearity at semi-blind relays, are investigated. Based on the modified AF cooperative system model taking into account the HPA nonlinearity, the expression for the output signal-to-noise ratio (SNR) at the destination node is derived, where the interference due to both the AF relaying mechanism and the HPA nonlinearity is characterized. The performance of the AF cooperative system under study is evaluated in terms of average symbol error probability (SEP), which is derived using the moment-generating function (MGF) approach, considering transmissions over Nakagami-m fading channels. Numerical results are provided and show the effects of some system parameters, such as the HPA parameters, numbers of relays, quadrature amplitude modulation (QAM) order, Nakagami parameters, on performance. © 2012 IEEE.

  18. A Systematic Approach to Setting Underfrequency Relays in Electric Power Systems

    Science.gov (United States)

    Qadri, Syed Saadat

    Generation loss contingencies in electric power systems result in a deviation of system frequency from nominal, a condition which must be corrected promptly in order to prevent further degradation of the power system. Automatic load-shedding using underfrequency relays is one of the techniques used to correct abnormal frequency deviations and prevent the risk of uncontrolled outages. If sufficient load is shed following a contingency to preserve interconnections and keep generators on-line, the system can be restored with relative speed and ease. On the other hand, if a declining frequency condition is not dealt with adequately, a cascading disconnection of generating units may develop, leading to a possible total system blackout. This thesis develops and tests a new systematic method for setting underfrequency relays offering a number of advantages over conventional methods. A discretized swing equation model is used to evaluate the system frequency following a contingency, and the operational logic of an underfrequency relay is modeled using mixed integer linear programming (MILP) techniques. The proposed approach computes relay settings with respect to a subset of all plausible contingencies for a given system. A method for selecting the subset of contingencies for inclusion in the MILP is presented. The goal of this thesis is to demonstrate that given certain types of degrees of freedom in the relay setting problem, it is possible to obtain a set of relay settings that limits damage or disconnection of generating units for each and every possible generation loss outage in a given system, while attempting to shed the least amount of load for each contingency.

  19. Application of DIgSILENT POWERFACTORY software for modeling of industrial network relay protection system

    Directory of Open Access Journals (Sweden)

    Sučević Nikola

    2016-01-01

    Full Text Available This paper presents modeling of industrial network relay protection system using DIgSILENT PowerFactory software. The basis for the model of protection system is a model of a single substation in an industrial network. The paper presents the procedure for modeling of protective devices of 6 kV asynchronous motors, 6/0,4 kV/kV transformers as well as protection in the bus coupler and busbar protection. Protective relay system response for the simulated disturbances is shown in the paper.

  20. Relay Protection and Automation Systems Based on Programmable Logic Integrated Circuits

    Energy Technology Data Exchange (ETDEWEB)

    Lashin, A. V., E-mail: LashinAV@lhp.ru; Kozyrev, A. V. [JSC “Lenhydroproject” (Russian Federation)

    2015-09-15

    One of the most promising forms of developing the apparatus part of relay protection and automation devices is considered. The advantages of choosing programmable logic integrated circuits to obtain adaptive technological algorithms in power system protection and control systems are pointed out. The technical difficulties in the problems which today stand in the way of using relay protection and automation systems are indicated and a new technology for solving these problems is presented. Particular attention is devoted to the possibility of reconfiguring the logic of these devices, using programmable logic integrated circuits.

  1. A minimum bit error-rate detector for amplify and forward relaying systems

    KAUST Repository

    Ahmed, Qasim Zeeshan

    2012-05-01

    In this paper, a new detector is being proposed for amplify-and-forward (AF) relaying system when communicating with the assistance of L number of relays. The major goal of this detector is to improve the bit error rate (BER) performance of the system. The complexity of the system is further reduced by implementing this detector adaptively. The proposed detector is free from channel estimation. Our results demonstrate that the proposed detector is capable of achieving a gain of more than 1-dB at a BER of 10 -5 as compared to the conventional minimum mean square error detector when communicating over a correlated Rayleigh fading channel. © 2012 IEEE.

  2. Decentralized Fair Scheduling in Two-Hop Relay-Assisted Cognitive OFDMA Systems

    CERN Document Server

    Wang, Rui; Cui, Ying

    2010-01-01

    In this paper, we consider a two-hop relay-assisted cognitive downlink OFDMA system (named as secondary system) dynamically accessing a spectrum licensed to a primary network, thereby improving the efficiency of spectrum usage. A cluster-based relay-assisted architecture is proposed for the secondary system, where relay stations are employed for minimizing the interference to the users in the primary network and achieving fairness for cell-edge users. Based on this architecture, an asymptotically optimal solution is derived for jointly controlling data rates, transmission power, and subchannel allocation to optimize the average weighted sum goodput where the proportional fair scheduling (PFS) is included as a special case. This solution supports decentralized implementation, requires small communication overhead, and is robust against imperfect channel state information at the transmitter (CSIT) and sensing measurement. The proposed solution achieves significant throughput gains and better user-fairness compa...

  3. Protocol design and stability/delay analysis of half-duplex buffered cognitive relay systems

    CERN Document Server

    Chen, Yan; Zhang, Shunqing; Qiu, Peiliang

    2010-01-01

    In this paper, we quantify the benefits of employing relay station in large-coverage cognitive radio systems which opportunistically access the licensed spectrum of some small-coverage primary systems scattered inside. Through analytical study, we show that even a simple decode-and-forward (SDF) relay, which can hold only one packet, offers significant path-loss gain in terms of the spatial transmission opportunities and link reliability. However, such scheme fails to capture the spatial-temporal burstiness of the primary activities, that is, when either the source-relay (SR) link or relay-destination (RD) link is blocked by the primary activities, the cognitive spectrum access has to stop. To overcome this obstacle, we further propose buffered decode-and-forward (BDF) protocol. By exploiting the infinitely long buffer at the relay, the blockage time on either SR or RD link is saved for cognitive spectrum access. The buffer gain is shown analytically to improve the stability region and average end-to-end dela...

  4. Towards Resource Allocation Algorithm in Opportunistic Relaying Cooperative UWB Communication System

    Directory of Open Access Journals (Sweden)

    Tingting Yang

    2014-02-01

    Full Text Available A novel communication system named “OR cooperative UWB” is proposed by bringing OR (Opportunistic Relaying to UWB system. Particularly, the exact and closed-form symbol error rate (SER expression is derived firstly in this paper. In order to maximize the capacity considering fairness between users, a definition of equivalent mean channel gain is given, and a joint resource allocation algorithm is also proposed which includes three steps: sub-band allocation algorithm, relaying allocation algorithm and power allocation algorithm. Employing the conception of “relative requirement degree”, the algorithm shows a distributed solution targeting relay partner selecting and increasing capacity while satisfying the users’ QoS (Quality of Service requirement. Simulations results validate the performance of the proposed algorithm.

  5. Robust on-line relay automatic tuning of PID control systems

    Science.gov (United States)

    Tan; Lee; Jiang

    2000-01-01

    In this paper, a robust on-line relay automatic tuning method for PID control systems is developed which expand on the application domain of Astrom's renowned relay autotuning method. In the proposed configuration, a relay is applied to an inner loop of a controller-stabilised process in the usual manner. Using the induced limit cycle oscillations from the closed-loop system, the controller settings may be re-tuned non-iteratively to achieve enhanced performance without disrupting closed-loop control. Two control tuning methodologies are developed -- a direct and an indirect method based on an explicit process model. Simulation examples and a real-time experiment are provided to illustrate the practical appeal and potential advantages of the proposed method over the basic one.

  6. Meteorological satellite systems

    CERN Document Server

    Tan, Su-Yin

    2014-01-01

    “Meteorological Satellite Systems” is a primer on weather satellites and their Earth applications. This book reviews historic developments and recent technological advancements in GEO and polar orbiting meteorological satellites. It explores the evolution of these remote sensing technologies and their capabilities to monitor short- and long-term changes in weather patterns in response to climate change. Satellites developed by various countries, such as U.S. meteorological satellites, EUMETSAT, and Russian, Chinese, Japanese and Indian satellite platforms are reviewed. This book also discusses international efforts to coordinate meteorological remote sensing data collection and sharing. This title provides a ready and quick reference for information about meteorological satellites. It serves as a useful tool for a broad audience that includes students, academics, private consultants, engineers, scientists, and teachers.

  7. Towards a Framework for Modelling and Verification of Relay Interlocking Systems

    DEFF Research Database (Denmark)

    Haxthausen, Anne Elisabeth

    2010-01-01

    This paper describes a framework currently under development for modelling, simulation, and verification of relay interlocking systems as used by the Danish railways. The framework is centred around a domain-specific language (DSL) for describing such systems, and provides (1) a graphical editor ...

  8. Digital transceiver design for two-way AF-MIMO relay systems with imperfect CSI

    Science.gov (United States)

    Hu, Chia-Chang; Chou, Yu-Fei; Chen, Kui-He

    2013-09-01

    In the paper, combined optimization of the terminal precoders/equalizers and single-relay precoder is proposed for an amplify-and-forward (AF) multiple-input multiple-output (MIMO) two-way single-relay system with correlated channel uncertainties. Both terminal transceivers and relay precoding matrix are designed based on the minimum mean square error (MMSE) criterion when terminals are unable to erase completely self-interference due to imperfect correlated channel state information (CSI). This robust joint optimization problem of beamforming and precoding matrices under power constraints belongs to neither concave nor convex so that a nonlinear matrix-form conjugate gradient (MCG) algorithm is applied to explore local optimal solutions. Simulation results show that the robust transceiver design is able to overcome effectively the loss of bit-error-rate (BER) due to inclusion of correlated channel uncertainties and residual self-interference.

  9. CHANNEL ESTIMATION TECHNIQUE IN MULTI-ANTENNA AF RELAY COMMUNICATION SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Chen Mingxue; Xu Chengqi

    2011-01-01

    The channel estimation technique is investigated in OFDM communication systems with multi-antenna Amplify-and-Forward (AF) relay.The Space-Time Block Code (STBC) is applied at the transmitter of the relay to obtain diversity gain.According to the transmission characteristics of OFDM symbols on multiple antennas,a pilot-aided Linear Minimum Mean-Square-Error (LMMSE) channel estimation algorithm with low complexity is designed.Simulation results show that,the proposed LMMSE estimator outperforms least-square estimator and approaches the optimal estimator without error in the performance of Symbol Error Ratio (SER) under several modulation modes,and has a good estimation effect in the realistic relay communication scenario.

  10. Joint TAS and power allocation for DF relaying M2M cooperative system

    Science.gov (United States)

    Xu, Lingwei; Zhang, Hao; Gulliver, T. Aaron

    2016-09-01

    The outage probability (OP) performance of transmit antenna selection (TAS) in a decode-and-forward relaying mobile-to-mobile system with relay selection over N-Nakagami fading channels is investigated. Exact closed-form expressions for the OP of two TAS schemes are derived, and the optimal power allocation optimisation problem is formulated. The OP performance is evaluated via Monte Carlo simulation to verify the analysis. The results obtained show that the optimal TAS scheme has better performance than the suboptimal TAS scheme, but the performance gap between these techniques decreases as the number of source antennas increases.

  11. Robust Transceiver Design for AF MIMO Relay Systems with Column Correlations

    CERN Document Server

    Xing, Chengwen; Wu, Yik-Chung; Ma, Shaodan; Kuang, Jingming

    2012-01-01

    In this paper, we investigate the robust transceiver design for dual-hop amplify-and-forward (AF) MIMO relay systems with Gaussian distributed channel estimation errors. Aiming at maximizing the mutual information under imperfect channel state information (CSI), source precoder at source and forwarding matrix at the relay are jointly optimized. Using some elegant attributes of matrix-monotone functions, the structures of the optimal solutions are derived first. Then based on the derived structure an iterative waterfilling solution is proposed. Several existing algorithms are shown to be special cases of the proposed solution. Finally, the effectiveness of the proposed robust design is demonstrated by simulation results.

  12. Robust Beamforming for Amplify-and-Forward MIMO Relay Systems Based on Quadratic Matrix Programming

    CERN Document Server

    Xing, Chengwen; Wu, Yik-Chung; Ng, Tung-Sang

    2010-01-01

    In this paper, robust transceiver design based on minimum-mean-square-error (MMSE) criterion for dual-hop amplify-and-forward MIMO relay systems is investigated. The channel estimation errors are modeled as Gaussian random variables, and then the effect are incorporated into the robust transceiver based on the Bayesian framework. An iterative algorithm is proposed to jointly design the precoder at the source, the forward matrix at the relay and the equalizer at the destination, and the joint design problem can be efficiently solved by quadratic matrix programming (QMP).

  13. Multihop relaying and multiple antenna techniques: performance trade-offs in cellular systems

    Directory of Open Access Journals (Sweden)

    Jacobson Kevin

    2011-01-01

    Full Text Available Abstract Two very important and active areas of wireless research are multihop relaying and multiple antenna techniques. Wireless multihop relaying can increase the aggregate network data capacity and improve coverage of cellular systems by reducing path loss, mitigating shadowing, and enabling spatial reuse. In particular, multihop relaying can improve the throughput for mobiles suffering from poor signal to interference and noise ratio at the edge of a cell and reduce cell size to increase spectral efficiency. On the other hand, multiple antenna techniques can take advantage of scattering in the wireless channel to achieve higher capacity on individual links. Multiple antennas can provide impressive capacity gains, but the greatest gains occur in high scattering environments with high signal to interference and noise ratio, which are not typical characteristics of cellular systems. Emerging standards for fourth generation cellular systems include both multihop relaying and multiple antenna techniques, so it is necessary to study how these two work jointly in a realistic cellular system. In this paper, we look at the joint application of these two techniques in a cellular system and analyze the fundamental tradeoff between them. In order to obtain meaningful results, system performance is evaluated using realistic propagation models.

  14. High power excimer laser image relay system analysis using Delano diagram

    Science.gov (United States)

    Zhang, Yongshen; Zhao, Jun; Zhao, Xueqing; Hu, Yun; Wang, Dahui; Xue, Quanxi; Liu, Jingru

    2013-05-01

    The characteristics of Delano diagram are especially helpful in instrumental systems type with considerably separated components. For high power excimer laser system, especially for image relay scheme, the Delano diagram method is highly advantageous for the system's thin lens layout design. A primitive experimental image relay and it's combination optical layout is investigated in our high power XeCl laser system, with intensity smoothed spatial incoherent source. Instead of the uniform intensity distribution on the target as expected, it is obvious shows in the final image on the target that a gauss like intensity profile and a large amount of astigmatism results. There are two possible reasons: the first one is that not keeping proper relay of pupil plane (or Fourier plane) in the final stage, simply care the collimated beam of virtual object in the final focusing stage. With the help of Delano diagram, it's clearly shown in the diagram that the Fourier plane and the image plane come very close, indicates that a complete image relay of the object plane and Fourier plane is needed. The second reason is due to the off-axis setup in the large aperture main amplifier, which introduce significant astigmatism aberrations in the final optical path. This question can be solved using proper tilt and de-center of reflective mirror pair setup, and two possible such combination pairs are proposed.

  15. Resource optimization in distributed cooperative multi-relay system based on STBC-OFDM

    Institute of Scientific and Technical Information of China (English)

    WU Tong; QU Xin-chun; WANG Ying

    2007-01-01

    On the basis of the amplify-and-forward relaying mode, a two-hop distributed cooperative multi-relay system is proposed combining with the space-time block coding OFDM (STBC-OFDM) technique. Taking (he maximum end-to-end data rate as optimization criterion, the signal-to-noise ratio (SNR)of receiving terminal is deduced. On the basis of the water-filling theory, the optimal power allocation (OPA) is achieved for each subcarrier in each antenna and each relay node (RN) of the two-hop, to realize the resource optimization. Monte Carlo method is adopted in simulation. The simulation results show that compared with the uniform resource allocation scheme, the proposed OPA strategy can improve the system capacity. And the energy consumption of each transmission bit will be decreased, indicating the improvement of resource efficiency. In the scenario that the total power is limited, the system performance can be enhanced further by the distributed cooperative multi-relay through the diversity gain.

  16. Bandwidth and power allocation for two-way relaying in overlay cognitive radio systems

    KAUST Repository

    Alsharoa, Ahmad M.

    2014-12-01

    In this paper, the problem of both bandwidth and power allocation for two-way multiple relay systems in overlay cognitive radio (CR) setup is investigated. In the CR overlay mode, primary users (PUs) cooperate with cognitive users (CUs) for mutual benefits. In our framework, we propose that the CUs are allowed to allocate a part of the PUs spectrum to perform their cognitive transmission. In return, acting as an amplify-and-forward two-way relays, they are used to support PUs to achieve their target data rates over the remaining bandwidth. More specifically, CUs acts as relays for the PUs and gain some spectrum as long as they respect a specific power budget and primary quality-of-service constraints. In this context, we first derive closed-form expressions for optimal transmit power allocated to PUs and CUs in order to maximize the cognitive objective. Then, we employ a strong optimization tool based on particle swarm optimization algorithm to find the optimal relay amplification gains and optimal cognitive released bandwidths as well. Our numerical results illustrate the performance of our proposed algorithm for different utility metrics and analyze the impact of some system parameters on the achieved performance.

  17. Wireless Powered Relaying Networks Under Imperfect Channel State Information: System Performance and Optimal Policy for Instantaneous Rate

    Directory of Open Access Journals (Sweden)

    D. T. Do

    2017-09-01

    Full Text Available In this investigation, we consider wireless powered relaying systems, where energy is scavenged by a relay via radio frequency (RF signals. We explore hybrid time switching-based and power splitting-based relaying protocol (HTPSR and compare performance of Amplify-and-Forward (AF with Decode-and-Forward (DF scheme under imperfect channel state information (CSI. Most importantly, the instantaneous rate, achievable bit error rate (BER are determined in the closed-form expressions under the impact of imperfect CSI. Through numerical analysis, we evaluate system insights via different parameters such as power splitting (PS and time switching (TS ratio of the considered HTPSR which affect outage performance and BER. It is noted that DF relaying networks outperform AF relaying networks. Besides that, the numerical results are given to prove the optimization problems of PS and TS ratio to obtain optimal instantaneous rate.

  18. Semi-Blind System Identification in Wireless Relay Networks via Gaussian Process Iterated Conditioning on the Modes Estimation

    CERN Document Server

    Peters, Gareth W; Yuan, Jinhong; Collings, Ian

    2011-01-01

    This paper presents a flexible stochastic model developed for a class of cooperative wireless relay networks, in which the relay processing functionality is not known at the destination. The challenge is then to perform online system identification in this wireless relay network. To address this challenging problem we develop a novel class of statistical models and a computationally efficient algorithm that can be performed in real time processing, to undertake system identification for each relay channel in the presence of partial Channel State Information (CSI). We also develop a lower bound result and several sub-optimal though computationally efficient solutions to the identification problem, for comparison. We provide several examples for different non-linear relay functionalities.

  19. Achievable Rates of UAV-Relayed Cooperative Cognitive Radio MIMO Systems

    KAUST Repository

    Sboui, Lokman

    2017-04-19

    We study the achievable rate of an uplink MIMO cognitive radio system where the primary user (PU) and the secondary user (SU) aim to communicate to the closest primary base station (BS) via a multi-access channel through the same unmanned aerial vehicle (UAV) relay. The SU message is then forwarded from the primary BS to the secondary network with a certain incentive reward as a part of the cooperation protocol between both networks. A special linear precoding scheme is proposed to enable the SU to exploit the PU free eigenmodes. We analyze two scenarios in which the UAV relay gain matrix is either fixed or optimized. We derive the optimal power allocation that maximizes the achievable rate of the SU respecting power budget, interference, and relay power constraints. Numerical results highlight the cognitive rate gain of our proposed scheme with respect to various problem parameters. We also highlight the effect of UAV altitude on the SU and PU rates. Finally, when the relay matrix is optimized, we show that the PU rate is remarkably enhanced and that the SU rate is only improved at high power regime.

  20. Switched diversity strategies for dual-hop amplify-and-forward relaying systems

    KAUST Repository

    Gaaloul, Fakhreddine

    2012-01-01

    This study investigates different receive single-branch switch-based diversity schemes for dual-hop amplify-and-forward relaying networks. Specifically, three receive processing algorithms are adopted, in which the receive branch is selected using the arbitrary selection algorithm, the switching algorithm, or the switching algorithm with post-examining best branch selection. The identification of the receive branch is carried out for two different system models. For the first model, a single-antenna relaying station is used in conjunction with a multiple-antenna transceiver, where the processing is performed independently of the first hop-fading conditions. The second model suggests the use of parallel deployment of single-antenna relays to transfer information from a multiple-antenna transmitter to a single-antenna receiver, where the active relaying station is determined based on the pre-combining end-to-end fading conditions. Performance comparisons for various transmission scenarios on the first hop are presented using new formulations for the statistics of the combined signal-to-noise ratio. Simulation results are also provided to validate the mathematical development and to verify the numerical computations. © 2012 The Institution of Engineering and Technology.

  1. Protective relay principles

    CERN Document Server

    Sleva, Anthony F

    2009-01-01

    This title lets you improve failure detection and optimize protection. In the ever-evolving field of protective relay technology, an engineer's personal preference and professional judgment are as important to power system protection as the physical relays used to detect and isolate abnormal conditions. With invaluable insights from an experienced expert, ""Protective Relay Principles"" focuses on probable power system failure modes and the important characteristics of the protective relays used to detect these postulated failures.This book presents useful new concepts in a way that is easier

  2. Precoding Design of MIMO Amplify-and-Forward Communication System With an Energy Harvesting Relay and Possibly Imperfect CSI

    KAUST Repository

    Benkhelifa, Fatma

    2017-03-02

    In this paper, we investigate the simultaneous wireless information and power transfer (SWIPT) in a Multiple-Input Multiple-Output (MIMO) Amplify-and-Forward (AF) relay communication system where the relay is an energy harvesting (EH) node and harvests the energy the signals transmitted from the source. The harvested energy is partially used to forward signals from the source to the destination, and the remaining energy is stored for other usages. The SWIPT in relay-assisted communication is interesting as long as the relay stores energy from the source and the destination receives successfully the data from the source. In this context, we propose to investigate the source and relay precoders that characterize the relationship between the achievable stored energy at the relay and the achievable sourceto- destination rate, namely the rate-stored energy (R-E) tradeo region. First, we consider the ideal scheme where there is the simultaneous operation of the EH and ID receivers at the relay. Then, we consider practical schemes such as the power splitting (PS) and the time switching (TS) that separate the operation of EH and information decoding (ID) receivers over power domain or time domain, respectively. Moreover, we study the case of imperfect channel state information (CSI) at the relay and the destination and characterize its impact on the achievable R-E region. Through the simulation results, we show the eect of the position of the relay and the channel uncertainty on the achievable R-E regions of all the schemes when the used energy at the relay is constant or variable. We also show that, although it provides an outer bound on the achievable rate-energy region in one-hop MIMO systems, the ideal scheme provides only an upper bound on the maximum achievable end-to-end rate and not an outer bound on the R-E region.

  3. Development and Testing of a Two-UAV Communication Relay System

    OpenAIRE

    Boyang Li; Yifan Jiang; Jingxuan Sun; Lingfeng Cai; Chih-Yung Wen

    2016-01-01

    In the development of beyond-line-of-sight (BLOS) Unmanned Aerial Vehicle (UAV) systems, communication between the UAVs and the ground control station (GCS) is of critical importance. The commonly used economical wireless modules are restricted by the short communication range and are easily blocked by obstacles. The use of a communication relay system provides a practical way to solve these problems, improving the performance of UAV communication in BLOS and cross-obstacle operations. In thi...

  4. Two-way cooperative AF relaying in spectrum-sharing systems: Enhancing cell-edge performance

    KAUST Repository

    Xia, Minghua

    2012-09-01

    In this contribution, two-way cooperative amplify-and-forward (AF) relaying technique is integrated into spectrumsharing wireless systems to improve spectral efficiency of secondary users (SUs). In order to share the available spectrum resources originally dedicated to primary users (PUs), the transmit power of a SU is optimized with respect to the average tolerable interference power at primary receivers. By analyzing outage probability and achievable data rate at the base station and at a cell-edge SU, our results reveal that the uplink performance is dominated by the average tolerable interference power at primary receivers, while the downlink always behaves like conventional one-way AF relaying and its performance is dominated by the average signal-to-noise ratio (SNR). These important findings provide fresh perspectives for system designers to improve spectral efficiency of secondary users in next-generation broadband spectrum-sharing wireless systems. © 2012 IEEE.

  5. Dual-Hop VLC/RF Transmission System with Energy Harvesting Relay under Delay Constraint

    KAUST Repository

    Rakia, Tamer

    2017-02-09

    In this paper, we introduce a dual-hop visible light communication (VLC) / radio frequency (RF) transmission system to extend the coverage of indoor VLC systems. The relay between the two hops is able to harvest light energy from different artificial light sources and sunlight entering the room. The relay receives data packet over a VLC channel and uses the harvested energy to retransmit it to a mobile terminal over an RF channel. We develop a novel statistical model for the harvested electrical power and analyze the probability of data packet loss. We define a system design parameter (α ∈ [0, 1)) that controls the time dedicated for excess energy harvesting and data packet retransmission. It was found that the parameter has an optimal value which minimizes the packet loss probability. Further more, this optimal value is independent of the RF channel path loss. However, optimal showed inverse dependence on the packet size.

  6. Modeling and control of non-square MIMO system using relay feedback.

    Science.gov (United States)

    Kalpana, D; Thyagarajan, T; Gokulraj, N

    2015-11-01

    This paper proposes a systematic approach for the modeling and control of non-square MIMO systems in time domain using relay feedback. Conventionally, modeling, selection of the control configuration and controller design of non-square MIMO systems are performed using input/output information of direct loop, while the output of undesired responses that bears valuable information on interaction among the loops are not considered. However, in this paper, the undesired response obtained from relay feedback test is also taken into consideration to extract the information about the interaction between the loops. The studies are performed on an Air Path Scheme of Turbocharged Diesel Engine (APSTDE) model, which is a typical non-square MIMO system, with input and output variables being 3 and 2 respectively. From the relay test response, the generalized analytical expressions are derived and these analytical expressions are used to estimate unknown system parameters and also to evaluate interaction measures. The interaction is analyzed by using Block Relative Gain (BRG) method. The model thus identified is later used to design appropriate controller to carry out closed loop studies. Closed loop simulation studies were performed for both servo and regulatory operations. Integral of Squared Error (ISE) performance criterion is employed to quantitatively evaluate performance of the proposed scheme. The usefulness of the proposed method is demonstrated on a lab-scale Two-Tank Cylindrical Interacting System (TTCIS), which is configured as a non-square system.

  7. Multiple Antennas Systems and Full Duplex Relay Systems with Hardware Impairments: New Performance Limits

    KAUST Repository

    Javed, Sidrah

    2016-12-01

    Next generation of wireless communication mostly relies on multiple-input multipleoutput (MIMO) configuration and full-duplex relaying to improve data-rates, spectrale efficiency, spatial-multiplexing, quality-of-service and energy-efficiency etc. However, multiple radio frequency (RF) transceivers in MIMO system and multi-hops in relay networks, accumulate transceiver impairments, rendering an unacceptable system performance. Majority of the technical contributions either assume ideal hardware or inappropriately model hardware impairments which often induce misleading results especially for high data-rate communication systems. We propose statistical mathematical modeling of various hardware impairment (HWI) to characterize their deteriorating effects on the information signal. In addition, we model the aggregate HWI as improper Gaussian signaling (IGS), to fully characterize their asymmetric properties and the self-interfering signal attribute under I/Q imbalance. The proposed model encourages to adopt asymmetric transmission scheme, as opposed to traditional symmetric signaling. First, we present statistical baseband equivalent mathematical models for general MIMO system and two special scenarios of receive and transmit diversity systems under HWI. Then, we express their achievable rate under PGS and IGS transmit schemes. Moreover, we tune the IGS statistical characteristics to maximize the achievable rate. We also present optimal beam-forming/pre-coding and receive combiner vector for multiple-input single-output (MISO) and single-input multiple output (SIMO) systems, which lead to SDNR maximization. Moreover, we propose an adaptive scheme to switch between maximal IGS (MIGS) and PGS transmission based on the described conditions to reduce computational overhead. Subsequently, two case studies are presented. 1) Outage analysis has been carried out for SIMO, under transceiver distortion noise, for two diversity combining schemes 2) The benefits of employing IGS

  8. Probing the Catalytic Charge-Relay System in Alanine Racemase with Genetically Encoded Histidine Mimetics.

    Science.gov (United States)

    Sharma, Vangmayee; Wang, Yane-Shih; Liu, Wenshe R

    2016-12-16

    Histidine is a unique amino acid with an imidazole side chain in which both of the nitrogen atoms are capable of serving as a proton donor and proton acceptor in hydrogen bonding interactions. In order to probe the functional role of histidine involved in hydrogen bonding networks, fine-tuning the hydrogen bonding potential of the imidazole side chain is required but not feasible through traditional mutagenesis methods. Here, we show that two close mimetics of histidine, 3-methyl-histidine and thiazole alanine, can be genetically encoded using engineered pyrrolysine incorporation machinery. Replacement of the three histidine residues predicted to be involved in an extended charge-relay system in alanine racemase with 3-methyl-histidine or thiazole alanine shows a dramatic loss in the enzyme's catalytic efficiency, implying the role of this extended charge-relay system in activating the active site residue Y265, a general acid/base catalyst in the enzyme.

  9. Outage probability of dual-hop FSO fixed gain relay transmission systems

    KAUST Repository

    Zedini, Emna

    2016-12-24

    In this paper, we analyze the end-to-end performance of dual-hop free-space optical (FSO) fixed gain relaying systems in the presence of atmospheric turbulence as well as pointing errors. More specifically, an exact closed-form expression for the outage probability is presented in terms of the bivariate Fox\\'s H function that accounts for both heterodyne detection as well as intensity modulation with direct detection. At high signal-to-noise ratio (SNR) regime, we provide very tight asymptotic result for this performance metric in terms of simple elementary functions. By using dual-hop FSO relaying, we demonstrate a better system performance as compared to the single FSO link. Numerical and Monte-Carlo simulation results are provided to verify the accuracy of the newly proposed results, and a perfect agreement is observed.

  10. Performance analysis of underlay cognitive multihop regenerative relaying systems with multiple primary receivers

    KAUST Repository

    Hyadi, Amal

    2013-12-01

    Multihop relaying is an efficient strategy to improve the connectivity and extend the coverage area of secondary networks in underlay cognitive systems. In this work, we provide a comprehensive performance study of cognitive multihop regenerative relaying systems in an underlay spectrum sharing scenario with the presence of multiple primary receivers. Both interference power and peak power constraints are taken into account. In our analysis, all the links are subject to independent, non-identically distributed Nakagami-m fading. We derive closed-form expressions for the outage probability, high-order amount of fading, bit error rate, symbol error rate, and ergodic capacity. Different scenarios are presented to illustrate the obtained results and Monte Carlo simulations confirm the accuracy of our analytical derivations. © 2013 IEEE.

  11. Transceiver Design at Relay and Destination for Dual-Hop Non-regenerative MIMO-OFDM Relay Systems Under Channel Uncertainties

    CERN Document Server

    Xing, Chengwen; Wu, Yik-Chung; Ng, Tung-Sang

    2010-01-01

    In this paper, joint design of linear relay precoder and destination equalizer for dual-hop non-regenerative amplify-and-forward (AF) MIMO-OFDM systems under channel estimation errors is investigated. Second order moments of channel estimation errors in the two hops are first deduced. Then based on the Bayesian framework, joint design of linear robust precoder at the relay and equalizer at the destination is proposed to minimize the total mean-square-error (MSE) of the output signal at the destination. The optimal designs for both correlated and uncorrelated channel estimation errors are considered. The relationship with existing algorithms is also disclosed. Simulation results show that the proposed robust designs outperform the design based on estimated channel state information only.

  12. Joint Transceiver Optimization for Multiuser MIMO Amplify-and-Forward Relay Broadcast Systems

    Science.gov (United States)

    Liu, Jun; Zhang, Xiong; Qiu, Zhengding

    This letter considers a dual-hop multiuser MIMO amplify-and-forward relay broadcast system with multi-antenna nodes. A unified scheme is addressed to jointly optimize the linear transceiver based on the sum mean-square error (MSE) and the sum rate criterion. The solutions are iteratively obtained by deriving the gradients of the objective functions for a gradient descent algorithm. Simulation results demonstrate the performance improvements in terms of the BER and the sum rate.

  13. A new hybrid optimization algorithm CRO-DE for optimal coordination of overcurrent relays in complex power systems

    Directory of Open Access Journals (Sweden)

    Mohamed Zellagui

    2017-09-01

    Full Text Available The paper presents a new hybrid global optimization algorithm based on Chemical Reaction based Optimization (CRO and Di¤erential evolution (DE algorithm for nonlinear constrained optimization problems. This approach proposed for the optimal coordination and setting relays of directional overcurrent relays in complex power systems. In protection coordination problem, the objective function to be minimized is the sum of the operating time of all main relays. The optimization problem is subject to a number of constraints which are mainly focused on the operation of the backup relay, which should operate if a primary relay fails to respond to the fault near to it, Time Dial Setting (TDS, Plug Setting (PS and the minimum operating time of a relay. The hybrid global proposed optimization algorithm aims to minimize the total operating time of each protection relay. Two systems are used as case study to check the effeciency of the optimization algorithm which are IEEE 4-bus and IEEE 6-bus models. Results are obtained and presented for CRO and DE and hybrid CRO-DE algorithms. The obtained results for the studied cases are compared with those results obtained when using other optimization algorithms which are Teaching Learning-Based Optimization (TLBO, Chaotic Differential Evolution Algorithm (CDEA and Modiffied Differential Evolution Algorithm (MDEA, and Hybrid optimization algorithms (PSO-DE, IA-PSO, and BFOA-PSO. From analysing the obtained results, it has been concluded that hybrid CRO-DO algorithm provides the most optimum solution with the best convergence rate.

  14. Relay race

    CERN Multimedia

    Staff Association

    2011-01-01

    The CERN relay race will take place around the Meyrin site on Thursday 19th May starting at 12·15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on the course, and how to register your team for the relay race, can be found at: https://espace.cern.ch/Running-Club/CERN-Relay Some advice for all runners from the medical service can also be found here: https://espace.cern.ch/Running-Club/CERN-Relay/RelayPagePictures/MedicalServiceAnnoncement.pdf

  15. Relay race

    CERN Multimedia

    Staff Association

    2011-01-01

    The CERN relay race will take place around the Meyrin site on Thursday 19th May starting at 12:15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on the course, and how to register your team for the relay race, can be found at: https://espace.cern.ch/Running-Club/CERN-Relay Some advice for all runners from the medical service can also be found here: https://espace.cern.ch/Running-Club/CERN-Relay/RelayPagePictures/MedicalServiceAnnoncement.pdf

  16. Method of analyzing vibration characteristics of armature system of hermetically sealed electromagnetic relay

    Institute of Scientific and Technical Information of China (English)

    REN Wan-bin; CUI Li; LUO Fu-biao; ZHAI Guo-fu

    2007-01-01

    Published research is minimal on vibration characteristics of hermetically sealed electromagnetic relay (EMR) exposed to mechanical environment. The vibration characteristics of armature system, link contact system with electromagnetic system will cause EMR malfunction. The nonlinear dynamics model of armature systems was studied by considering electromagnetic attraction force and opposite mechanical force in this paper. Angular displacements of armature under different sinusoidal vibration conditions are solved in order to obtain the failure mode result from armature system. Vibration tests showed the presented analyzing method is suitable for EMR. The conclusions are instructive for increasing vibration resistance of armature systems of EMR, and are significant for reliability design of switch apparatus.

  17. The foundation and analysis of polarized magnetic system's unified mathematical model in aerospace electromagnetic relay

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Polarized magnetic system has a series of features, such as small volume, light weight, low power consumption, high sensitivity, quick movement and so on, widely used in the products of the military aerospace electromagnetic relay. The typical polarized magnetic system has mainly four structures and its simplified equivalent magnetic circuits model is the base of the design of the electromagnetic relay with permanent magnet. In the past, the analysis method that people used was difficult to build the unified mathematical models, which divided the work gap magnetic flux into "permanent magnet flux" and "electromagnetic flux". Based on the analysis method of the work gap magnetic voltage, this paper founds the unified mathematical model of the polarized magnetic system and divides the attractive torque into permanent magnet torque, polarized torque and electromagnetic torque through the energy balance formula. It analyses the influence of permanent magnet sizes on permanent magnet torque, polarized torque and electromagnetic torque through the energy balance formula and the conclusions can direct the design of aerospace electromagnetic relay with permanent magnet.

  18. Joint Robust Weighted LMMSE Transceiver Design for Dual-Hop AF Multiple-Antenna Relay Systems

    CERN Document Server

    Xing, Chengwen; Fei, Zesong; Wu, Yik-Chung; Kuang, Jingming

    2012-01-01

    In this paper, joint transceiver design for dual-hop amplify-and-forward (AF) MIMO relay systems with Gaussian distributed channel estimation errors in both two hops is investigated. Due to the fact that various linear transceiver designs can be transformed to a weighted linear minimum mean-square-error (LMMSE) transceiver design with specific weighting matrices, weighted mean square error (MSE) is chosen as the performance metric. Precoder matrix at source, forwarding matrix at relay and equalizer matrix at destination are jointly designed with channel estimation errors taken care of by Bayesian philosophy. Several existing algorithms are found to be special cases of the proposed solution. The performance advantage of the proposed robust design is demonstrated by the simulation results.

  19. Robust Transceiver with Tomlinson-Harashima Precoding for Amplify-and-Forward MIMO Relaying Systems

    CERN Document Server

    Xing, Chengwen; Gao, Feifei; Wu, Yik-Chung

    2011-01-01

    In this paper, robust transceiver design with Tomlinson-Harashima precoding (THP) for multi-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relaying systems is investigated. At source node, THP is adopted to mitigate the spatial intersymbol interference. However, due to its nonlinear nature, THP is very sensitive to channel estimation errors. In order to reduce the effects of channel estimation errors, a joint Bayesian robust design of THP at source, linear forwarding matrices at relays and linear equalizer at destination is proposed. With novel applications of elegant characteristics of multiplicative convexity and matrix-monotone functions, the optimal structure of the nonlinear transceiver is first derived. Based on the derived structure, the transceiver design problem reduces to a much simpler one with only scalar variables which can be efficiently solved. Finally, the performance advantage of the proposed robust design over non-robust design is demonstrated by simulation results.

  20. Control of relay structure on mineralization of sedimentaryexhalative ore deposit in growth faults of graben systems

    Institute of Scientific and Technical Information of China (English)

    XI Xiao-shuang; TANG Jing-ru; KONG Hua; HE Sho-xun

    2005-01-01

    Based on the study of ore deposits and orebody structures of two sedimentary-exhalative ore deposits,i. e. , Changba and Xitieshan Ore Deposits, it is found that the structural patterns of metallogenic basin of seafloor exhalative sulfide deposits in the ancient graben systems are controlled by relay structures in normal faults. The shapes of metallogenic basins are composed of tilting ramp, fault-tip ramp and relay ramp, which dominate migration of gravity current of ore-hosted fluid and shape of orebody sedimentary fan in the ramp. By measuring and comparing the difference of length-to-thickness ratios of orebody sedimentary fan, the result shows that the occurrence of the ramp has a remarkable impact on the shape of orebody.

  1. Robust Transceiver with Tomlinson-Harashima Precoding for Amplify-and-Forward MIMO Relaying Systems

    KAUST Repository

    Xing, Chengwen

    2012-09-01

    In this paper, robust transceiver design with Tomlinson-Harashima precoding (THP) for multi-hop amplifyand-forward (AF) multiple-input multiple-output (MIMO) relaying systems is investigated. At source node, THP is adopted to mitigate the spatial intersymbol interference. However, due to its nonlinear nature, THP is very sensitive to channel estimationerrors. In order to reduce the effects of channel estimation errors, a joint Bayesian robust design of THP at source, linear forwarding matrices at relays and linear equalizer at destination is proposed. With novel applications of elegant characteristics of multiplicative convexity and matrix-monotone functions, the optimal structure of the nonlinear transceiver is first derived. Based on the derived structure, the transceiver design problem reduces to a much simpler one with only scalar variables which can be efficiently solved. Finally, the performance advantage of the proposed robust design over non-robust design is demonstrated by simulation results.

  2. Robust Tomlinson-Harashima precoding for non-regenerative multi-antenna relaying systems

    KAUST Repository

    Xing, Chengwen

    2012-04-01

    In this paper, we consider the robust transceiver design with Tomlinson-Harashima precoding (THP) for multi-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relaying systems. THP is adopted at the source to mitigate the spatial inter-symbol interference and then a joint Bayesian robust design of THP at source, linear forwarding matrices at relays and linear equalizer at destination is proposed. Based on the elegant characteristics of multiplicative convexity and matrix-monotone functions, the optimal structure of the nonlinear transceiver is first derived. Based on the derived structure, the optimization problem is greatly simplified and can be efficiently solved. Finally, the performance advantage of the proposed robust design is assessed by simulation results. © 2012 IEEE.

  3. Spanish Earth Observation Satellite System

    Science.gov (United States)

    Borges, A.; Cerezo, F.; Fernandez, M.; Lomba, J.; Lopez, M.; Moreno, J.; Neira, A.; Quintana, C.; Torres, J.; Trigo, R.; Urena, J.; Vega, E.; Vez, E.

    2010-12-01

    The Spanish Ministry of Industry, Tourism and Trade (MITyC) and the Ministry of Defense (MoD) signed an agreement in 2007 for the development of a "Spanish Earth Observation Satellite System" based, in first instance, on two satellites: a high resolution optical satellite, called SEOSAT/Ingenio, and a radar satellite based on SAR technology, called SEOSAR/Paz. SEOSAT/Ingenio is managed by MITyC through the Centre for the Development of Industrial Technology (CDTI), with technical and contractual support from the European Space Agency (ESA). HISDESA T together with the Spanish Instituto Nacional de Técnica Aeroespacial (INTA, National Institute for Aerospace Technology) will be responsible for the in-orbit operation and the commercial operation of both satellites, and for the technical management of SEOSAR/Paz on behalf of the MoD. In both cases EADS CASA Espacio (ECE) is the prime contractor leading the industrial consortia. The ground segment development will be assigned to a Spanish consortium. This system is the most important contribution of Spain to the European Programme Global Monitoring for Environment and Security, GMES. This paper presents the Spanish Earth Observation Satellite System focusing on SEOSA T/Ingenio Programme and with special emphasis in the potential contribution to the ESA Third Party Missions Programme and to the Global Monitoring for Environment and Security initiative (GMES) Data Access.

  4. On the spectral-energy efficiency and rate fairness tradeoff in relay-aided cooperative OFDMA systems

    OpenAIRE

    Song, Zhengyu; Ni, Qiang; Navaie, Keivan; Hou, S.; Wu, S.

    2016-01-01

    In resource constrained wireless systems, achieving higher spectral efficiency (SE) and energy efficiency (EE), and greater rate fairness are conflicting objectives. Here a general framework is presented to analyze the tradeoff among these three performance metrics in cooperative OFDMA systems with decode-and-forward (DF) relaying, where subcarrier pairing and allocation, relay selection, choice of transmission strategy, and power allocation are jointly considered. In our analytical framework...

  5. Information management system: A summary discussion. [for use in the space shuttle sortie, modular space station and TDR satellite

    Science.gov (United States)

    Sayers, R. S.

    1972-01-01

    An information management system is proposed for use in the space shuttle sortie, the modular space station, the tracking data relay satellite and associated ground support systems. Several different information management functions, including data acquisition, transfer, storage, processing, control and display are integrated in the system.

  6. Overview and Status of the Laser Communication Relay Demonstration

    Science.gov (United States)

    Luzhanskiy, E.; Edwards, B.; Israel, D.; Cornwell, D.; Staren, J.; Cummings, N.; Roberts, T.; Patschke, R.

    2016-01-01

    NASA is presently developing first all optical high data rate satellite relay system, LCRD. To be flown on commercial geosynchronous satellite, it will communicate at DPSK and PPM modulation formats up to 1.244 Gbps. LCRD flight payload is being developed by NASA's Goddard Space Flight Center. The two ground stations, one on Table Mountain in CA, developed by NASA's Jet Propulsion Laboratory and another on Hawaiian island will enable bi-directional relay operation and ground sites diversity experiments. In this paper we will report on the current state of LCRD system development, planned operational scenarios and expected system performance.

  7. BICM-based cooperative communication systems with relay selection: Constellation and multiplexer design

    KAUST Repository

    Malik, Muhammad Talha

    2014-09-01

    We propose a new bit-interleaved coded modulation (BICM)-based cooperative communication system where different BICM modules can be optimized jointly considering the average signal to noise ratios of the direct and the two-hop Rayleigh fading channels. As such, the full benefit of BICM can be exploited in the context of cooperative communication. Our design considers cooperative communication systems with so called max-min relay selection scheme that has no loss in performance in terms of diversity- multiplexing trade off in orthogonal cooperation. The presented numerical results for rate 1/2 convolutional code with 8-ary pulse amplitude modulation equivalently 64-ary quadrature amplitude modulation show that the proposed design can offer gains up to 1.4 dB over the traditional BICM design for a target bit error rate of 10-6. Moreover the results show that the amount of gain depends on the relays\\' positions and increases with the number of relays available for selection.

  8. Use of a geosynchronous satellite within the SARSAT/COSPAS system

    Science.gov (United States)

    Goudy, P.; Ludwig, D.; Trudell, B.

    1982-01-01

    Operational characteristics of combined LEO SARSAT/COSPAS and GEO spacecraft for localization of aircraft and seacraft emitting distress signals are described. Although 121.5 MHz capability is now included in all SARSAT/COSPAS satellites, limitations on the number of simultaneous signals which can be processed at that frequency due to atmospheric noise indicates the employment of the 406 MHz band. Additionally, the necessity for on-board storage for later transmission when the satellites are in a favorable position is leading to the implementation of GEO stationed relays for real-time transmission and processing of distress signals. Six NOAA spacecraft and two Soviet satellites are planned, with a completed system offering high detection probability, position location, worldwide coverage, coded messages, and high capacity (406 MHz). A significant factor in use of a GEO relay system is noted to be the signal to noise temperature of the repeater.

  9. Serial Failure Diagnosis of a Transmission Line Protection Relaying System by Petri Nets

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    With the development of large-scale complicated modern power systems, the requirement for the associatedprotection scheme tends to be more stringent and its combination more complex. However, it is very difficult to figureout the factors of failure of such systems. This paper proposes a Petri net model of a transmission line protectionrelaying system, including three types of relays as well as an automatic re-closing device, and shows how to diagnoseserial failure of the system by analyzing invariant sets of the model. Furthermore, it gives four basic types of failuresequences and its execution is much more intuitive and effective than the traditional method.

  10. Advanced satellite communication system

    Science.gov (United States)

    Staples, Edward J.; Lie, Sen

    1992-01-01

    The objective of this research program was to develop an innovative advanced satellite receiver/demodulator utilizing surface acoustic wave (SAW) chirp transform processor and coherent BPSK demodulation. The algorithm of this SAW chirp Fourier transformer is of the Convolve - Multiply - Convolve (CMC) type, utilizing off-the-shelf reflective array compressor (RAC) chirp filters. This satellite receiver, if fully developed, was intended to be used as an on-board multichannel communications repeater. The Advanced Communications Receiver consists of four units: (1) CMC processor, (2) single sideband modulator, (3) demodulator, and (4) chirp waveform generator and individual channel processors. The input signal is composed of multiple user transmission frequencies operating independently from remotely located ground terminals. This signal is Fourier transformed by the CMC Processor into a unique time slot for each user frequency. The CMC processor is driven by a waveform generator through a single sideband (SSB) modulator. The output of the coherent demodulator is composed of positive and negative pulses, which are the envelopes of the chirp transform processor output. These pulses correspond to the data symbols. Following the demodulator, a logic circuit reconstructs the pulses into data, which are subsequently differentially decoded to form the transmitted data. The coherent demodulation and detection of BPSK signals derived from a CMC chirp transform processor were experimentally demonstrated and bit error rate (BER) testing was performed. To assess the feasibility of such advanced receiver, the results were compared with the theoretical analysis and plotted for an average BER as a function of signal-to-noise ratio. Another goal of this SBIR program was the development of a commercial product. The commercial product developed was an arbitrary waveform generator. The successful sales have begun with the delivery of the first arbitrary waveform generator.

  11. Comparison of Low-Complexity Diversity Schemes for Dual-Hop AF Relaying Systems

    KAUST Repository

    Gaaloul, Fakhreddine

    2012-02-13

    This paper investigates the performance of two low-complexity combining schemes, which are based on one- or two-phase observation, to mitigate multipath fading in dual-hop amplify-and-forward relaying systems. For the one-phase-based combining, a single-antenna station is assumed to relay information from a multiple-antenna transmitter to a multiple-antenna receiver, and the activation of the receive antennas is adaptively performed based on the second-hop statistics, regardless of the first-hop conditions. On the other hand, the two-phase-based combining suggests using multiple single-antenna stations between the multiple-antenna transmitter and the single-antenna receiver, where the suitable set of active relays is identified according to the precombining end-to-end fading conditions. To facilitate comparisons between the two schemes, formulations for the statistics of the combined signal-to-noise ratio and some performance measures are presented. Numerical and simulation results are shown to clarify the tradeoff between the achieved diversity-array gain, the processing complexity, and the power consumption.

  12. Multistability and hidden attractors in a relay system with hysteresis

    DEFF Research Database (Denmark)

    Zhusubaliyev, Zhanybai T.; Mosekilde, Erik; Rubanov, Vasily G.

    2015-01-01

    For nonlinear dynamic systems with switching control, the concept of a "hidden attractor" naturally applies to a stable dynamic state that either (1) coexists with the stable switching cycle or (2), if the switching cycle is unstable, has a basin of attraction that does not intersect with the nei...

  13. End-to-end performance of cooperative relaying in spectrum-sharing systems with quality of service requirements

    KAUST Repository

    Asghari, Vahid Reza

    2011-07-01

    We propose adopting a cooperative relaying technique in spectrum-sharing cognitive radio (CR) systems to more effectively and efficiently utilize available transmission resources, such as power, rate, and bandwidth, while adhering to the quality of service (QoS) requirements of the licensed (primary) users of the shared spectrum band. In particular, we first consider that the cognitive (secondary) user\\'s communication is assisted by an intermediate relay that implements the decode-and-forward (DF) technique onto the secondary user\\'s relayed signal to help with communication between the corresponding source and the destination nodes. In this context, we obtain first-order statistics pertaining to the first- and second-hop transmission channels, and then, we investigate the end-to-end performance of the proposed spectrum-sharing cooperative relaying system under resource constraints defined to assure that the primary QoS is unaffected. Specifically, we investigate the overall average bit error rate (BER), ergodic capacity, and outage probability of the secondary\\'s communication subject to appropriate constraints on the interference power at the primary receivers. We then consider a general scenario where a cluster of relays is available between the secondary source and destination nodes. In this case, making use of the partial relay selection method, we generalize our results for the single-relay scheme and obtain the end-to-end performance of the cooperative spectrum-sharing system with a cluster of L available relays. Finally, we examine our theoretical results through simulations and comparisons, illustrating the overall performance of the proposed spectrum-sharing cooperative system and quantify its advantages for different operating scenarios and conditions. © 2011 IEEE.

  14. Preliminary Design Options for Meteor Burst Communications Systems Buoy Relays

    Science.gov (United States)

    1986-12-01

    the lithium - thionyl chloride cell exhibit specific energies of the order of 500 watt hours per kilogram, more than 50 percent higher than previous...Supply Buoy Design Type 90 Day Storage Weight Type Energy Type Size (lb) Remote Lithium 2.2 kWh Deployable 8" x 8" x 4’ 200 Battery Pendulous Master...however, that there are various typcs of lithium batteries presently being developed that have energy densities equal to’fuel cell power systems. It is

  15. Cooperative AF Relaying in Spectrum-Sharing Systems: Performance Analysis under Average Interference Power Constraints and Nakagami-m Fading

    KAUST Repository

    Xia, Minghua

    2012-06-01

    Since the electromagnetic spectrum resource becomes more and more scarce, improving spectral efficiency is extremely important for the sustainable development of wireless communication systems and services. Integrating cooperative relaying techniques into spectrum-sharing cognitive radio systems sheds new light on higher spectral efficiency. In this paper, we analyze the end-to-end performance of cooperative amplify-and-forward (AF) relaying in spectrum-sharing systems. In order to achieve the optimal end-to-end performance, the transmit powers of the secondary source and the relays are optimized with respect to average interference power constraints at primary users and Nakagami-$m$ fading parameters of interference channels (for mathematical tractability, the desired channels from secondary source to relay and from relay to secondary destination are assumed to be subject to Rayleigh fading). Also, both partial and opportunistic relay-selection strategies are exploited to further enhance system performance. Based on the exact distribution functions of the end-to-end signal-to-noise ratio (SNR) obtained herein, the outage probability, average symbol error probability, diversity order, and ergodic capacity of the system under study are analytically investigated. Our results show that system performance is dominated by the resource constraints and it improves slowly with increasing average SNR. Furthermore, larger Nakagami-m fading parameter on interference channels deteriorates system performance slightly. On the other hand, when interference power constraints are stringent, opportunistic relay selection can be exploited to improve system performance significantly. All analytical results are corroborated by simulation results and they are shown to be efficient tools for exact evaluation of system performance.

  16. Performance analysis of dual-hop relaying systems in the presence of Co-channel interference

    KAUST Repository

    Ikki, Salama Said

    2010-12-01

    In this paper, we investigate the effect of co-channel interference on the performance of dual-hop communications with amplify-and-forward relaying. Based on the derivation of the effective signal-to-interference-plus-noise ratio (SINR) at the destination node of the system, taking into account co-channel interference, we obtain expressions for the error and outage probabilities. Moreover, we study the performance of the system in the high SINR regime. Monte-Carlo simulations are further provided and confirm the accuracy of the analytical results. ©2010 IEEE.

  17. Analysis of the call blocking rate of two-hop-relay cellular system in the dead spots

    Institute of Scientific and Technical Information of China (English)

    LU Wei-feng; WU Meng

    2007-01-01

    In a traditional cellular system, the call requests initiated by mobile stations (MSs) must be carried through a base station (BS) via the cellular interface, but when MSs are located in the dead spots, their call requests will be blocked because the MSs cannot communicate with the BS. It is considered to relay these blocked calls requested using Ad-hoc network, which will improve the performance of the system as a whole. This article first introduces a novel architecture of the two-hop-relay cellular system in the dead spots, and then analyzes and compares the call blocking rate of the traditional cellular and the two-hop-relay cellular system respectively under three different conditions. The first and second conditions are the traditional cellular system without and with taking account of the effect of the dead spots. The third condition is the two-hop-relay cellular system with taking account of the effect of the dead spots. Numerical analytical result shows that the two-hop-relay cellular system can obtain lower call blocking rate than the traditional cellular system when considering the effect of dead spots. Consequently, this novel architecture can resolve the problem of coverage limitation of a traditional cellular system effectively.

  18. The Omninet mobile satellite system

    Science.gov (United States)

    Salmasi, A.; Curry, W.

    Mobile Satellite System (MSS) design offering relatively low cost voice, data, and position location services to nonmetropolitan areas of North America is proposed. The system provides spectrally efficient multiple access and modulation techniques, and flexible user interconnection to public and private switched networks. Separate UHF and L-band satellites employing two 9.1 m unfurlable antennas each, achieve a 6048 channel capacity and utilize spot beams. Mobile terminals have modular design and employ 5 dBi omnidirectional antennas. Gateway stations (with two 5 m Ku-band antennas) and base stations (with a single 1.8 m Ku-band antenna) transmit terrestrial traffic to the satellite, where traffic is then transponded via an L-band or UHF downlink to mobile users. The Network Management Center uses two 5-m antennas and incorporates the Integrated-Adaptive Mobile Access Protocol to assure demand assignment of satellite capacity. Preliminary implementation of this low-risk system involves a mobile alphanumeric data service employing receive-only terminals at Ku-band projected for 1987, and plans for the launching of L-band receive-only packages as early as 1988.

  19. Performance Characterization of a Hybrid Satellite-Terrestrial System with Co-Channel Interference over Generalized Fading Channels.

    Science.gov (United States)

    Javed, Umer; He, Di; Liu, Peilin

    2016-08-05

    The transmission of signals in a hybrid satellite-terrestrial system (HSTS) in the presence of co-channel interference (CCI) is considered in this study. Specifically, we examine the problem of amplify-and-forward (AF)-based relaying in a hybrid satellite-terrestrial link, where the relay node is operating in the presence of a dominant co-channel interferer. It is assumed that direct connection between a source node (satellite) and a destination node (terrestrial receiver) is not available due to masking by obstacles in the surrounding. The destination node is only able to receive signals from the satellite with the help of a relay node located at the ground. In the proposed HSTS, the satellite-relay channel follows the shadowed Rice fading; and the channels of interferer-relay and relay-destination links experience generalized Nakagami-m fading. For the considered AF-based HSTS, we first develop the analytical expression for the moment generating function (MGF) of the overall output signal-to-interference-plus-noise ratio (SINR). Then, based on the derived exact MGF, we derive novel expressions for the average symbol error rate (SER) of the considered HSTS for the following digital modulation techniques: M-ary phase shift keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM) and M-ary pulse amplitude modulation (M-PAM). To significantly reduce the computational complexity for utility in system-level simulations, simple analytical approximation for the exact SER in the high signal-to-noise ratio (SNR) regime is presented to provide key insights. Finally, numerical results and the corresponding analysis are presented to demonstrate the effectiveness of the developed performance evaluation framework and to view the impact of CCI on the considered HSTS under varying channel conditions and with different modulation schemes.

  20. A Concept GEO-SPS & Airship Multi-Megawatt Power Relay System

    Science.gov (United States)

    Dickinson, R.

    An SPS power relay system for delivering multi-megawatts of grid electric power from GEO via a stratospheric airship platform is presented. A solar powered laser is proposed to beam power to InGaN band-gap matched PV located in a station- kept platform, where the received DC power is converted to 2.45 GHz microwave beams for relay to the surface using a phased array. To complete the power transmission link, spatially diverse, 260-m diameter rectennas provide the interfaces to the electric utility power grid. Unique requirements include that it is to be an all-weather electric delivery system, to be purposely designed to preclude its use as a power beam weapon at the Earth's surface, and to be delivered to orbit in a single launch vehicle. Estimates are presented for the airship design assumptions, expected performance parameters and the various power conversion and power transfer efficiencies and the cost of the parts of the system, along with the suggested alternate revenue sources for making the high altitude platform more cost effective. Unfortunately, the cost to orbit dominates. The sunlight-to-grid power collection, conversion and transfer efficiency of order 8.2% is double that of ground based PV systems given their day-night, atmosphere and weather handicaps.

  1. Relay Placement for FSO Multihop DF Systems With Link Obstacles and Infeasible Regions

    KAUST Repository

    Zhu, Bingcheng

    2015-05-19

    Optimal relay placement is studied for free-space optical multihop communication with link obstacles and infeasible regions. An optimal relay placement scheme is proposed to achieve the lowest outage probability, enable the links to bypass obstacles of various geometric shapes, and place the relay nodes in specified available regions. When the number of relay nodes is large, the searching space can grow exponentially, and thus, a grouping optimization technique is proposed to reduce the searching time. We numerically demonstrate that the grouping optimization can provide suboptimal solutions close to the optimal solutions, but the average searching time linearly grows with the number of relay nodes. Two useful theorems are presented to reveal insights into the optimal relay locations. Simulation results show that our proposed optimization framework can effectively provide desirable solution to the problem of optimal relay nodes placement. © 2015 IEEE.

  2. Joint Relaying Selection and Power Allocation Algorithms for Cooperative Cellular System

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jing-mei; SHAO Chun-ju; WANG Ying; ZHANG Ping

    2005-01-01

    An architecture introducing wireless relaying technologies into the cellular infrastructure has emerged as an approach to enlarge the coverage area and enhance system capacity. In this paper, a two-hop cellular system incorporated with the fixed Relaying Station (RS) is studied, where besides the Uniform Power Allocation (UPA), the Optimal Power Allocation (OPA) between the Base Station (BS) and RS is also adopted considering resource utilization. To maximize the performance gains and reduce the overhead, it is necessary to provide an effective RS selection algorithm and combine it with other resource management strategies. So two kinds of RS selection criteria based upon Signal to Interference Ratio (SIR) and PathLoss (PL), are evolved into four Joint RS Selection and Power Allocation (JRSPA) algorithms, which are based on SIR with OPA (SIR-OPA), SIR with UPA (SIR-UPA), PL with OPA (PL-OPA) and PL with UPA (PL-UPA). The simulation results show that among these four algorithms, the SIR-OPA scheme provides the best capacity performance, but taking the overhead into account, the PL-OPA scheme is a better choice to reduce the complexity and trade off the system performance with signaling load.

  3. Satellite augmentation of cellular type mobile radio telephone systems

    Science.gov (United States)

    Anderson, Roy E.

    NASA's ATS-6 satellite relayed voice bandwidth communications between five trucks and the trucking company dispatchers as the trucks traveled throughout the north-eastern quarter of the contiguous United States. The experiment, conducted over a seven month period, demonstrated that propagation characteristics are much different for the satellite-mobile links than for terrestrial-mobile links. A properly designed satellite system can provide high quality, reliable voice and data communications except where the vehicle-satellite path is shadowed by a structure or terrain feature. Mobile equipment in the experiment was adapted from commercial mobile radios. The vehicle antennas were 75 cm tall, 2 cm diam. Another experiment proved the feasibility of vehicle position surveillance using active two-way tone-code ranging through ATS-6 to provide one line of position and passive one-way ranging by measuring the time-of-arrival of a signal from an independent satellite. A position fix was printed out at an earth station 1 sec after it sent the interrogation signal to the distant vehicle, a towboat on the Mississippi River. The line of position from ATS-6 was accurate to 0.1 nautical mile using a voice bandwidth ranging signal. The line of position from the NOAA GOES satellite was accurate to 2 miles, using 100 Hz signal bandwidth. If the signal from the independent satellite had the same bandwidth and signal-to-noise ratio as ATS-6, the fixes would have been accurate to about 0.1 nautical mile. A concept study concluded that satellites might be a cost effective augmentation of terrestrial cellular type mobile radio telephone systems. The satellites would serve thinly populated areas where terrestrial systems are not cost effective. In the United States, the satellites would serve about 90% of the land area where 20% of the population resides. A multibeam satellite with many channels in each beam would be compatible with the urban terrestrial systems and together they would

  4. Distributed Role Selection With ANC and TDBC Protocols in Two-Way Relaying Systems

    KAUST Repository

    Ding, Haiyang

    2015-09-28

    This paper advocates a distributed role selection strategy to coordinate two-way relaying transmissions among three cooperative nodes. For such, the local channel state information comparison and decision feedback mechanism are merged into classical analog network coding (ANC) and time division broadcast (TDBC) protocols such that the cooperative role of each node can be designated in a distributed fashion. We refer to this distributed role selection rule as d-ROSE. In both ANC-based and TDBC-based two-way relaying scenarios, strict proof for the equivalence of d-ROSE and optimal ROSE is given, which indicates that albeit the different form, their final role decision is essentially the same. Outage analysis for the d-ROSE strategy is carried out and the scaling law of the system outage behavior at high signal-to-noise ratio (SNR) is characterized, which manifests that d-ROSE can enhance the system diversity gain to one-order higher relative to the ANC and TDBC protocols. It is also shown that d-ROSE can reduce the signaling overhead upto 60% to perform the outage-optimal role selection. Finally, the impacts of node placement on the outage performance as well as the average signaling overhead of d-ROSE are numerically evaluated and some useful conclusions are drawn. © 2015 IEEE.

  5. OFDM AF Variable Gain Relay System for the Next Generation Mobile Cellular

    Directory of Open Access Journals (Sweden)

    E. Kocan

    2012-06-01

    Full Text Available In this paper we present analytical performance evaluation of a dual-hop OFDM amplify-andforward (AF variable gain (VG relay system implementing ordered subcarrier mapping (SCM at the relay station (R, considered to be a very interesting solution for the next generation mobile cellular networks. A scenario with no direct communication between the source of information (S and destination terminal (D, with the Rayleigh fading statistics on both hops is assumed. A closed form analytical expression for the bit error rate (BER performance of the considered system with DPSK modulation is derived, while for its ergodic capacity performance, a tight upper bound expression is obtained. The accuracy of the undertaken analytical approach is confirmed through comparison with simulation results. It is shown that significant capacity enhancement can be achieved through SCM implementation at R, for all the signal-to-noise ratio (SNR values on both hops, but especially in the region of small SNRs on hops. BER analysis reveals that in the region of small and medium average SNRs on both hops BER performance may also be improved with SCM at R station.

  6. Minimizing the symbol-error-rate for amplify-and-forward relaying systems using evolutionary algorithms

    KAUST Repository

    Ahmed, Qasim Zeeshan

    2015-02-01

    In this paper, a new detector is proposed for an amplify-and-forward (AF) relaying system. The detector is designed to minimize the symbol-error-rate (SER) of the system. The SER surface is non-linear and may have multiple minimas, therefore, designing an SER detector for cooperative communications becomes an optimization problem. Evolutionary based algorithms have the capability to find the global minima, therefore, evolutionary algorithms such as particle swarm optimization (PSO) and differential evolution (DE) are exploited to solve this optimization problem. The performance of proposed detectors is compared with the conventional detectors such as maximum likelihood (ML) and minimum mean square error (MMSE) detector. In the simulation results, it can be observed that the SER performance of the proposed detectors is less than 2 dB away from the ML detector. Significant improvement in SER performance is also observed when comparing with the MMSE detector. The computational complexity of the proposed detector is much less than the ML and MMSE algorithms. Moreover, in contrast to ML and MMSE detectors, the computational complexity of the proposed detectors increases linearly with respect to the number of relays.

  7. Information-guided transmission in decode-and-forward relaying systems: Spatial exploitation and throughput enhancement

    KAUST Repository

    Yang, Yuli

    2011-07-01

    In addressing the issue of achieving high throughput in half-duplex relay channels, we exploit a concept of information-guided transmission for the network consisting of a source node, a destination node, and multiple half-duplex relay nodes. For further benefiting from multiple relay nodes, the relay-selection patterns are defined as the arbitrary combinations of given relay nodes. By exploiting the difference among the spatial channels states, in each relay-help transmission additional information to be forwarded is mapped onto the index of the active relay-selection pattern besides the basic information mapped onto the traditional constellation, which is forwarded by the relay node(s) in the active relay-selection pattern, so as to enhance the relay throughtput. With iterative decoding, the destination node can achieve a robust detection by decoupling the signals forwarded in different ways. We investigate the proposed scheme considering "decode-and-forward" protocol and establish its achievable transmission rate. The analytical results on capacity behaviors prove the efficiency of the proposed scheme by showing that it achieves better capacity performance than the conventional scheme. © 2011 IEEE.

  8. Satellite Attitude Control System Simulator

    Directory of Open Access Journals (Sweden)

    G.T. Conti

    2008-01-01

    Full Text Available Future space missions will involve satellites with great autonomy and stringent pointing precision, requiring of the Attitude Control Systems (ACS with better performance than before, which is function of the control algorithms implemented on board computers. The difficulties for developing experimental ACS test is to obtain zero gravity and torque free conditions similar to the SCA operate in space. However, prototypes for control algorithms experimental verification are fundamental for space mission success. This paper presents the parameters estimation such as inertia matrix and position of mass centre of a Satellite Attitude Control System Simulator (SACSS, using algorithms based on least square regression and least square recursive methods. Simulations have shown that both methods have estimated the system parameters with small error. However, the least square recursive methods have performance more adequate for the SACSS objectives. The SACSS platform model will be used to do experimental verification of fundamental aspects of the satellite attitude dynamics and design of different attitude control algorithm.

  9. Two-Layer Coding Rate Optimization in Relay-Aided Systems

    DEFF Research Database (Denmark)

    Sun, Fan

    2011-01-01

    We consider a three-node transmission system, where a source node conveys a data block to a destination node with the help of a half-duplex decode and-forward (DF) relay node. The whole data block is transmitted as a sequence of packets. For reliable transmission in the three-node system, a two...... different system performance requirements. For different objectives, two optimization problems are formulated and solutions are presented. One is to minimize the outage probability given the efficiency requirement, while the other one is to maximize the transmission efficiency given the outage probability...... requirement. Numerical results are also provided to show the optimized physical layer coding and network coding rate pairs in different system scenarios....

  10. Microwave-powered airship system design for high-altitude power relay and other applications

    Energy Technology Data Exchange (ETDEWEB)

    Dickinson, R.M. [California Inst. of Tech., Pasadena, CA (United States). Guggenheim Jet Propulsion Center

    1997-11-01

    A concept for a next generation of stratospheric airship platforms was presented and examined. The design was based on a 1MW DC power output from beamed microwave power from the ground. The ground and airborne major subsystems were described. In the future, airborne near-stationary platforms could provide power beaming relay functions plus telecommunications and observation. The system will allow for near-continuous regional Earth sensing of soil moisture, crop condition, vehicular traffic on the ground or vessels at sea and craft in the air, environmental impacts, local weather, stream flow and floods, ice, migration patterns, land use, aerial photographs for mapping, surveillance, detection and tracking. A summary description of how the system might be applied and the currently available applicable technology was presented. System requirements and constraints were also described. A rough cost estimate of a point-design was provided. 22 refs., 1 fig.

  11. Two-Layer Coding Rate Optimization in Relay-Aided Systems

    DEFF Research Database (Denmark)

    Sun, Fan

    2011-01-01

    We consider a three-node transmission system, where a source node conveys a data block to a destination node with the help of a half-duplex decode and-forward (DF) relay node. The whole data block is transmitted as a sequence of packets. For reliable transmission in the three-node system, a two......-layer coding scheme is proposed, where physical layer channel coding is utilized within each packet for error-correction and random network coding is applied on top of channel coding for network error-control. There is a natural tradeoff between the physical layer coding rate and the network coding rate given...... requirement. Numerical results are also provided to show the optimized physical layer coding and network coding rate pairs in different system scenarios....

  12. Ground Simulation of an Autonomous Satellite Rendezvous and Tracking System Using Dual Robotic Systems

    Science.gov (United States)

    Trube, Matthew J.; Hyslop, Andrew M.; Carignan, Craig R.; Easley, Joseph W.

    2012-01-01

    A hardware-in-the-loop ground system was developed for simulating a robotic servicer spacecraft tracking a target satellite at short range. A relative navigation sensor package "Argon" is mounted on the end-effector of a Fanuc 430 manipulator, which functions as the base platform of the robotic spacecraft servicer. Machine vision algorithms estimate the pose of the target spacecraft, mounted on a Rotopod R-2000 platform, relay the solution to a simulation of the servicer spacecraft running in "Freespace", which performs guidance, navigation and control functions, integrates dynamics, and issues motion commands to a Fanuc platform controller so that it tracks the simulated servicer spacecraft. Results will be reviewed for several satellite motion scenarios at different ranges. Key words: robotics, satellite, servicing, guidance, navigation, tracking, control, docking.

  13. Rational Phosphorus Application Facilitates the Sustainability of the Wheat/Maize/Soybean Relay Strip Intercropping System.

    Directory of Open Access Journals (Sweden)

    Yuanxue Chen

    Full Text Available Wheat (Triticum aestivum L./maize (Zea mays L./soybean (Glycine max L. relay strip intercropping (W/M/S system is commonly used by the smallholders in the Southwest of China. However, little known is how to manage phosphorus (P to enhance P use efficiency of the W/M/S system and to mitigate P leaching that is a major source of pollution. Field experiments were carried out in 2011, 2012, and 2013 to test the impact of five P application rates on yield and P use efficiency of the W/M/S system. The study measured grain yield, shoot P uptake, apparent P recovery efficiency (PRE and soil P content. A linear-plateau model was used to determine the critical P rate that maximizes gains in the indexes of system productivity. The results show that increase in P application rates aggrandized shoot P uptake and crops yields at threshold rates of 70 and 71.5 kg P ha-1 respectively. With P application rates increasing, the W/M/S system decreased the PRE from 35.9% to 12.3% averaged over the three years. A rational P application rate, 72 kg P ha-1, or an appropriate soil Olsen-P level, 19.1 mg kg-1, drives the W/M/S system to maximize total grain yield while minimizing P surplus, as a result of the PRE up to 28.0%. We conclude that rational P application is an important approach for relay intercropping to produce high yield while mitigating P pollution and the rational P application-based integrated P fertilizer management is vital for sustainable intensification of agriculture in the Southwest of China.

  14. TDRSS/user satellite timing study

    Science.gov (United States)

    Mcgregor, D.; Douglas, F.; Kaul, R.

    1976-01-01

    A timing analysis for data readout through the Tracking and Data Relay Satellite System (TDRSS) was presented. Various time tagging approaches were considered and the resulting accuracies delineated. The TDRSS was also defined and described in detail.

  15. Attitude Control and Orbital Dynamics Challenges of Removing the First 3-Axis Stabilized Tracking and Data Relay Satellite from the Geosynchronous ARC

    Science.gov (United States)

    Benet, Charles A.; Hofman, Henry; Williams, Thomas E.; Olney, Dave; Zaleski, Ronald

    2011-01-01

    Launched on April 4, 1983 onboard STS 6 (Space Shuttle Challenger), the First Tracking and Data Relay Satellite (TDRS 1) was retired above the Geosynchronous Orbit (GEO) on June 27, 2010 after having provided real-time communications with a variety of low-orbiting spacecraft over a 26-year period. To meet NASA requirements limiting orbital debris 1, a team of experts was assembled to conduct an End-Of-Mission (EOM) procedure to raise the satellite 350 km above the GEO orbit. Following the orbit raising via conventional station change maneuvers, the team was confronted with having to deplete the remaining propellant and passivate all energy storage or generation sources. To accomplish these tasks within the time window, communications (telemetry and control links), electrical power, propulsion, and thermal constraints, a spacecraft originally designed as a three-axis stabilized satellite was turned into a spinner. This paper (a companion paper to Innovative Approach Enabled the Retirement of TDRS 1, paper # 1699, IEEE 2011 Aerospace Conference, March 5-12, 2011 sup 2) focuses on the challenges of maintaining an acceptable spinning dynamics, while repetitively firing thrusters. Also addressed are the effects of thruster firings on the orbit characteristics and how they were mitigated by a careful scheduling of the fuel depletion operations. Periodic thruster firings for spin rate adjustment, nutation damping, and precession of the momentum vector were also required in order to maintain effective communications with the satellite. All operations were thoroughly rehearsed and supported by simulations thus lending a high level of confidence in meeting the NASA EOM goals.

  16. Transceiver Design for Dual-Hop Nonregenerative MIMO-OFDM Relay Systems Under Channel Uncertainties

    Science.gov (United States)

    Xing, Chengwen; Ma, Shaodan; Wu, Yik-Chung; Ng, Tung-Sang

    2010-12-01

    In this paper, linear transceiver design for dual-hop non-regenerative (amplify-and-forward (AF)) MIMO-OFDM systems under channel estimation errors is investigated. Second order moments of channel estimation errors in the two hops are first deduced. Then based on the Bayesian framework, joint design of linear forwarding matrix at the relay and equalizer at the destination under channel estimation errors is proposed to minimize the total mean-square-error (MSE) of the output signal at the destination. The optimal designs for both correlated and uncorrelated channel estimation errors are considered. The relationship with existing algorithms is also disclosed. Moreover, this design is extended to the joint design involving source precoder design. Simulation results show that the proposed design outperforms the design based on estimated channel state information only.

  17. Robust Linear Transceiver Design for Multi-Hop Non-Regenerative MIMO Relaying Systems

    CERN Document Server

    Xing, Chengwen; Ma, Shaodan; Kuang, Jingming; Wu, Yik-Chung

    2011-01-01

    In this paper, optimal linear transceiver designs for multi-hop amplify-and-forward (AF) Multiple-input Multiple-out (MIMO) relaying systems with Gaussian distributed channel estimation errors are investigated. Some commonly used transceiver design criteria are unified into a single matrix-variate optimization problem. With novel applications of majorization theory and properties of matrix-variate function, the optimal structure of robust transceiver is first derived. Based on the optimal structure, the original transceiver design problems are reduced to much simpler problems with only scalar variables whose solutions are readily obtained by iterative water-filling algorithms. The performance advantages of the proposed robust designs are demonstrated by the simulation results.

  18. Economics of satellite communications systems

    Science.gov (United States)

    Pritchard, Wilbur L.

    This paper is partly a tutorial, telling systematically how one goes about calculating the total annual costs of a satellite communications system, and partly the expression of some original ideas on the choice of parameters so as to minimize these costs. The calculation of costs can be divided into two broad categories. The first is technical and is concerned with estimating what particular equipment will cost and what will be the annual expense to maintain and operate it. One starts in the estimation of any new system by listing the principal items of equipment, such as satellites, earth stations of various sizes and functions, telemetry and tracking equipment and terrestrial interfaces, and then estimating how much each item will cost. Methods are presented for generating such estimates, based on a knowledge of the gross parameters, such as antenna size, coverage area, transmitter power and information rate. These parameters determine the system performance and it is usually possible, knowing them, to estimate the costs of the equipment rather well. Some formulae based on regression analyses are presented. Methods are then given for estimating closely related expenses, such as maintenance and operation, and then an approximate method is developed for estimating terrestrial interconnection costs. It is pointed out that in specific cases when tariff and geographical information are available, it is usually better to work with specific data, but nonetheless it is often desirable, especially in global system estimating, to approximate these interconnect costs without recourse to individual tariffs. The procedure results in a set of costs for the purchase of equipment and its maintenance, and a schedule of payments. Some payments will be incurred during the manufacture of the satellite and before any systems operation, but many will not be incurred until the system is no longer in use, e.g. incentives. In any case, with the methods presented in the first section, one

  19. Estimation of a condition of electromagnetic relays a method of acoustic diagnostics in systems of railway automatics

    Directory of Open Access Journals (Sweden)

    V.V. Laguta

    2012-04-01

    Full Text Available The paper deals with methods of preliminary analysis of sound signals to extract stable features in classifying the relay used in railway automation systems. The algorithm of the description of a sound signal on the basis of these attributes is offered.

  20. The typical behaviour of relays

    OpenAIRE

    Alamino, Roberto C.; Saad, David

    2007-01-01

    The typical behaviour of the relay-without-delay channel and its many-units generalisation, termed the relay array, under LDPC coding, is studied using methods of statistical mechanics. A demodulate-and-forward strategy is analytically solved using the replica symmetric ansatz which is exact in the studied system at the Nishimori's temperature. In particular, the typical level of improvement in communication performance by relaying messages is shown in the case of small and large number of re...

  1. Ergodic Capacity Analysis of Multiple Input Multiple Output Systems with Dual Hop Amplify and Forward Relay Networks

    Directory of Open Access Journals (Sweden)

    C. Poongodi

    2011-01-01

    Full Text Available Problem Statement: In MIMO system, capacity mainly depends on the channel and the antenna characteristics. The capacity can be improved by proper design of antenna elements and choosing appropriate array configuration and the directive elements give more capacity than omni directional elements. The dual polarized antennas are better than single polarized antennas as the former can provide two information channels. The mutual coupling also changes the capacity considerably. When the spacing between the elements is less than 0.5λ, the effect of mutual coupling is more. Approach: This study analyzes the capacity of Echelon, H-shaped; V-shaped free standing dipoles and printed dipole arrays of a MIMO system. The channel model for multi-polarized antennas is used in the simulations. The mutual coupling between the dipoles of different orientations is also included to make simulation more realistic. MIMO system with relay network is used to improve the coverage and reliability and to reduce the interference in wireless network. So we have analyzed the characterization of the ergodic capacity of amplify-and-forward (AF MIMO dual-hop relay channels, assuming that the channel state information is available at the destination terminal only. Results: This study presents the results for channel capacity for different antenna configuration and the exact Ergodic capacity, closed form expression for the high SNR regime and tight closed form upper and lower bounds for amplify and forward relay system using the probability density function of an unordered eigenvalues. Conclusion/Recommendations: The Echelon, H-shaped; V-shaped free standing dipoles offer better capacity results in conventional MIMO system. The results produced are valid for all SNR values and for arbitrary numbers of antennas at the source, relay and destination. We also demonstrate a relationship between the conventional point-to-point MIMO Channels and dual-hop AF MIMO relay channel.

  2. Energy-Efficient Relay Selection and Optimal Relay Location in Cooperative Cellular Networks with Asymmetric Traffic

    CERN Document Server

    Yang, Wei; Sun, Wanlu

    2010-01-01

    Energy-efficient communication is an important requirement for mobile relay networks due to the limited battery power of user terminals. This paper considers energy-efficient relaying schemes through selection of mobile relays in cooperative cellular systems with asymmetric traffic. The total energy consumption per information bit of the battery-powered terminals, i.e., the mobile station (MS) and the relay, is derived in theory. In the Joint Uplink and Downlink Relay Selection (JUDRS) scheme we proposed, the relay which minimizes the total energy consumption is selected. Additionally, the energy-efficient cooperation regions are investigated, and the optimal relay location is found for cooperative cellular systems with asymmetric traffic. The results reveal that the MS-relay and the relay-base station (BS) channels have different influence over relay selection decisions for optimal energy-efficiency. Information theoretic analysis of the diversity-multiplexing tradeoff (DMT) demonstrates that the proposed sc...

  3. Analysis of relay based valley coil system of K-130 Cyclotron and an approach to computer controlled system

    Energy Technology Data Exchange (ETDEWEB)

    Shoor, B.

    2016-09-11

    To overcome the first harmonic field imperfection in sector focused cyclotron, a set of coils placed in valleys are used to produce an opposite first harmonic effect. Usually, at the time of beam tuning the phase of the first harmonic is varied using a relay system. It can be shown analytically that magnitude of it changes simultaneously, when phase is changed. This is not desirable at the time of beam tuning. Moreover phase changes in long steps, which hampers accuracy of beam tuning. To overcome this, a computer controlled system is suggested where amplitude remains constant at the time of phase change. Moreover, phase can be changed continuously which gives better tuning accuracy.

  4. Global navigation satellite systems and their applications

    CERN Document Server

    Madry, Scott

    2015-01-01

    Dr. Madry, one of the world's leading experts in the field, provides in a condensed form a quick yet comprehensive overview of satellite navigation. This book concisely addresses the latest technology, the applications, the regulatory issues, and the strategic implications of satellite navigation systems. This assesses the strengths and weaknesses of satellite navigation networks and review of all the various national systems now being deployed and the motivation behind the proliferation of these systems.

  5. On the performance of spectrum sharing systems with two-way relaying and multiuser diversity

    KAUST Repository

    Yang, Liang

    2012-08-01

    In this letter, we consider a spectrum sharing network with two-way relaying and multi-user diversity. More specifically, one secondary transmitter with the best channel quality is selected and splits its partial power to relay its received signals to the primary users by using the amplify-and-forward relaying protocol. We derive a tight approximation for the resulting outage probability. Based on this formula, the performance of the spectral sharing region and the cell coverage are analyzed. Numerical results are given to verify our analysis and are discussed to illustrate the advantages of our newly proposed scheme. © 1997-2012 IEEE.

  6. Joint Bandwidth and Power Allocation for MIMO Two-Way Relays-Assisted Overlay Cognitive Radio Systems

    KAUST Repository

    Alsharoa, Ahmad

    2015-10-08

    This paper studies the achievable cognitive sum rate of an overlay cognitive radio (CR) system assisted with multiple antennas two-way relays in which primary users (PUs) cooperate with cognitive users (CUs) for mutual benefits. In this context, the problem of both bandwidth and power allocation is investigated. We propose that the CUs are allowed to allocate a part of the PUs spectrum to perform their cognitive transmission. In return, acting as amplify-and-forward two-way relays, they are exploited to support PUs to reach their target data rates over the remaining bandwidth. Power expressions for optimal transmit power allocated per PU and CU antenna are derived under primary quality-of-service constraint in addition to bandwidth and power budget constraints. More specifically, CUs act as relays for the PUs transmission and gain some spectrum as long as they respect these constraints. After deriving the optimal transmit powers, we employ a strong optimization tool based on swarm intelligence to optimize the full and complex relay amplification gain matrices in addition to the bandwidths released to primary and cognitive transmission. Furthermore, three different utility functions are considered in our optimization problems depending on the level of fairness among CUs.

  7. Joint terminals and relay optimization for two-way power line information exchange systems with QoS constraints

    Science.gov (United States)

    Wu, Xiaolin; Rong, Yue

    2015-12-01

    The quality-of-service (QoS) criteria (measured in terms of the minimum capacity requirement in this paper) are very important to practical indoor power line communication (PLC) applications as they greatly affect the user experience. With a two-way multicarrier relay configuration, in this paper we investigate the joint terminals and relay power optimization for the indoor broadband PLC environment, where the relay node works in the amplify-and-forward (AF) mode. As the QoS-constrained power allocation problem is highly non-convex, the globally optimal solution is computationally intractable to obtain. To overcome this challenge, we propose an alternating optimization (AO) method to decompose this problem into three convex/quasi-convex sub-problems. Simulation results demonstrate the fast convergence of the proposed algorithm under practical PLC channel conditions. Compared with the conventional bidirectional direct transmission (BDT) system, the relay-assisted two-way information exchange (R2WX) scheme can meet the same QoS requirement with less total power consumption.

  8. Transmit Power Minimization and Base Station Planning for High-Speed Trains with Multiple Moving Relays in OFDMA Systems

    KAUST Repository

    Ghazzai, Hakim

    2016-03-15

    High-speed railway system equipped with moving relay stations placed on the middle of the ceiling of each train wagon is investigated. The users inside the train are served in two hops via the orthogonal frequency-division multiple access (OFDMA) technology. In this work, we first focus on minimizing the total downlink power consumption of the base station (BS) and the moving relays while respecting specific quality of service (QoS) constraints. We first derive the optimal resource allocation solution in terms of OFDMA subcarriers and power allocation using the dual decomposition method. Then, we propose an efficient algorithm based on the Hungarian method in order to find a suboptimal but low complexity solution. Moreover, we propose an OFDMA planning solution for high-speed train by finding the maximal inter-BS distance given the required user data rates in order to perform seamless handover. Our simulation results illustrate the performance of the proposed resource allocation schemes in the case of the 3GPP Long Term Evolution-Advanced (LTE-A) and compare them with previously developed algorithms as well as with the direct transmission scenario. Our results also highlight the significant planning gain obtained thanks to the use of multiple relays instead of the conventional single relay scenario.

  9. Integration of mobile satellite and cellular systems

    Science.gov (United States)

    Drucker, Elliott H.; Estabrook, Polly; Pinck, Deborah; Ekroot, Laura

    1993-01-01

    By integrating the ground based infrastructure component of a mobile satellite system with the infrastructure systems of terrestrial 800 MHz cellular service providers, a seamless network of universal coverage can be established. Users equipped for both cellular and satellite service can take advantage of a number of features made possible by such integration, including seamless handoff and universal roaming. To provide maximum benefit at lowest posible cost, the means by which these systems are integrated must be carefully considered. Mobile satellite hub stations must be configured to efficiently interface with cellular Mobile Telephone Switching Offices (MTSO's), and cost effective mobile units that provide both cellular and satellite capability must be developed.

  10. Cross-layer design for cooperative MIMO systems with relay selection and imperfect CSI

    Institute of Scientific and Technical Information of China (English)

    YU XiangBin; ZHOU TingTing; RUI Yun; YIN Xin; CHEN Ming

    2013-01-01

    Based on imperfect channel state information (CSI) and relay selection, a cross-layer optimization scheme is developed for cooperative MIMO system, and the corresponding system performance is investigated in Rayleigh fading channel. By the theoretical analysis and mathematical manipulation, the average spectral efficiency (SE), packet error rate (PER) and packet loss rate (PLR) are derived. As a result, closed-form expressions of the average SE, PER and PLR are obtained, respectively. According to these, a cross-layer design (CLD) scheme subject to the average PER constraints is proposed to avoid the SE performance loss caused by the conventional instantaneous PER constraints. The scheme optimizes the adaptive thresholds by maximizing the average SE of the system, and an iteration method joint the Lagrange multiplier and Newton methods is presented to solve the above optimization problem. Simulation results verify the validity of the theoretical analysis. The results show that the proposed CLD scheme can improve the SE while target PLR is maintained. The CLD scheme under average PER constraints has higher SE than the conventional CLD scheme under instantaneous PER constraints.

  11. Fairness-Aware and Energy Efficiency Resource Allocation in Multiuser OFDM Relaying System

    Directory of Open Access Journals (Sweden)

    Guangjun Liang

    2016-01-01

    Full Text Available A fairness-aware resource allocation scheme in a cooperative orthogonal frequency division multiple (OFDM network is proposed based on jointly optimizing the subcarrier pairing, power allocation, and channel-user assignment. Compared with traditional OFDM relaying networks, the source is permitted to retransfer the same data transmitted by it in the first time slot, further improving the system capacity performance. The problem which maximizes the energy efficiency (EE of the system with total power constraint and minimal spectral efficiency constraint is formulated into a mixed-integer nonlinear programming (MINLP problem which has an intractable complexity in general. The optimization model is simplified into a typical fractional programming problem which is testified to be quasiconcave. Thus we can adopt Dinkelbach method to deal with MINLP problem proposed to achieve the optimal solution. The simulation results show that the joint resource allocation method proposed can achieve an optimal EE performance under the minimum system service rate requirement with a good global convergence.

  12. IMPLEMENTATION OF AERONAUTICAL LOCAL SATELLITE AUGMENTATION SYSTEM

    Directory of Open Access Journals (Sweden)

    Stojce Ilcev

    2011-03-01

    Full Text Available Abstract. This paper introduces development and implementation of new Local Satellite AugmentationSystem as an integration component of the Regional Satellite Augmentation System (RSAS employingcurrent and new Satellite Communications, Navigation and Surveillance (CNS for improvement of the AirTraffic Control (ATC and Air Traffic Management (ATM and for enhancement safety systems includingtransport security and control of flights in all stages, airport approaching, landing, departures and allmovements over airport surface areas. The current first generation of the Global Navigation Satellite SystemGNSS-1 applications are represented by fundamental military solutions for Position, Velocity and Time ofthe satellite navigation and determination systems such as the US GPS and Russian GLONASS (Former-USSR requirements, respectively. The establishment of Aeronautical CNS is also discussed as a part ofGlobal Satellite Augmentation Systems of GPS and GLONASS systems integrated with existing and futureRSAS and LSAS in airports areas. Specific influence and factors related to the Comparison of the Currentand New Aeronautical CNS System including the Integration of RSAS and GNSS solutions are discussedand packet of facts is determined to maximize the new satellite Automatic Dependent Surveillance System(ADSS and Special Effects of the RSAS Networks. The possible future integration of RSAS and GNSS andthe common proposal of the satellite Surface Movement Guidance and Control are presented in thechangeless ways as of importance for future enfacements of ATC and ATM for any hypothetical airportinfrastructure.Keywords: ADSS, ATC, ATM, CNS, GSAS, LRAS, RSAS, SMGC, Special Effects of RSAS.

  13. Multihop Relaying over IM/DD FSO Systems with Pointing Errors

    KAUST Repository

    Zedini, Emna

    2015-10-19

    In this paper, the end-to-end performance of a multihop free-space optical system with amplify-and-forward channelstate- information-assisted or fixed-gain relays using intensity modulation with direct detection technique over Gamma-Gamma turbulence fading with pointing error impairments is studied. More specifically, novel closed-form results for the probability density function and the cumulative distribution function of the end-to-end signal-to-noise ratio (SNR) are derived in terms of the Fox’s H function. Based on these formulas, closed-form bounds for the outage probability, the average bit-error rate (BER) of on-off keying modulation scheme, the moments, and the ergodic capacity are presented. Furthermore, using the momentsbased approach, tight asymptotic approximations at high and low average SNR regimes are derived for the ergodic capacity in terms of simple elementary functions. The obtained results indicate that the overall system performance degrades with an increase of the number of hops. The effects of the atmospheric turbulence conditions and the pointing error are also quantified. All the analytical results are verified via computer-based Monte- Carlo simulations.

  14. Robust Power Allocation for Multi-Carrier Amplify-and-Forward Relaying Systems

    KAUST Repository

    Rao, Anlei

    2012-09-08

    It has been shown that adaptive power allocation can provide a substantial performance gain in wireless communication systems when perfect channel state information (CSI) is available at the transmitter. However when only imperfect CSI is available, the performance may degrade significantly, and as such robust power allocation schemes have been developed to minimize the effects of this degradation. In this paper, we investigate power allocation strategies for multicarrier systems, in which each subcarrier employs single amplify-and-forward (AF) relaying scheme. Optimal power allocation schemes are proposed by maximizing the approximated channel capacity under aggregate power constraint (APC) and separate power constraint (SPC). By comparison with the uniform power allocation scheme and the best channel power allocation scheme, we confirm that both the APC and SPC schemes achieve a performance gain over benchmark schemes. In addition, the impact of channel uncertainty is also considered in this paper by modeling the uncertainty regions as bounded sets, and results show that the uncertainty can degrade the worst-case performance significantly.

  15. Robust Power Allocation for Multi-Carrier Amplify-and-Forward Relaying Systems

    KAUST Repository

    Rao, Anlei

    2012-09-08

    It has been shown that adaptive power allocation can provide a substantial performance gain in wireless communication systems when perfect channel state information (CSI) is available at the transmitter. However when only imperfect CSI is available, the performance may degrade significantly, and as such robust power allocation schemes have been developed to minimize the effects of this degradation. In this paper, we investigate power allocation strategies for multicarrier systems, in which each subcarrier employs single amplify-and-forward (AF) relaying scheme. Optimal power allocation schemes are proposed by maximizing the approximated channel capacity under aggregate power constraint (APC) and separate power constraint (SPC). By comparison with the uniform power allocation scheme and the best channel power allocation scheme, we confirm that both the APC and SPC schemes achieve a performance gain over benchmark schemes. In addition, the impact of channel uncertainty is also considered in this paper by modeling the uncertainty regions as bounded sets, and results show that the uncertainty can degrade the worst- case performance significantly.

  16. Design of the American Mobile Satellite System

    Science.gov (United States)

    Kittiver, Charles

    1991-01-01

    This paper presents an overview of the American Mobile Satellite Corporation (AMSC) Mobile Satellite System (MSS). A summary of the mobile satellite (MSAT) design and overall performance is provided. The design and components of both the forward link and return link transponders are described in detail. The design and operation of a unique hybrid matrix amplifier that offers flexible power distribution is outlined. The conceptual design and performance of three types of land mobile antennas are described.

  17. A Hybrid Shuffled Frog Leaping Algorithm to Solve Optimal Directional Over Current Relay Coordination Problem for Power Delivery System with DGs

    Directory of Open Access Journals (Sweden)

    Mohammad Sadegh Payam

    2012-01-01

    Full Text Available This study presents a new approach for simultaneous coordinated tuning of over current relay for a Power Delivery System (PDS including Distribution Generations (DGs. In the proposed scheme, instead of changing in protection system structure or using new elements, solving of relay coordination problem is done with revising of relays setting in presence of DGs. For this, the relay coordination problem is formulated as the optimization problem by considering two strategies: minimizing the relays operation time and minimizing the number of changes in relays setting. Also, an efficient hybrid algorithm based on Shuffled Frog Leaping (SFL algorithm and Linear Programming (LP is introduced for solving complex and non-convex optimization problem. To investigate the ability of the proposed method, a 30-bus IEEE test system is considered. Three scenarios are examined to evaluate the effectiveness of the proposed approach to solve the directional overcurrent relay coordination problem for a PDS with DGs. Simulation result show the efficiency of proposed method.

  18. Multihop communications over CSI-assisted relay IM/DD FSO systems with pointing errors

    KAUST Repository

    Zedini, Emna

    2015-09-14

    In this paper, the end-to-end performance of a multihop free-space optical system with amplify-and-forward channel-state-information-assisted relays using intensity modulation with direct detection technique over Gamma-Gamma turbulence fading with pointing error impairments is studied. More specifically, novel closed-form expressions for the moment generating function, the cumulative distribution function, and the probability density function of the end-to-end signal-to-noise ratio (SNR) are derived in terms of the Meijer\\'s G function. Based on these formulas, closed-form bounds for the outage probability, the average bit-error rate (BER) of a variety of modulation schemes, the moments, and the ergodic capacity are presented. Furthermore, by using the asymptotic expansion of the Meijer\\'s G function at high SNR, accurate asymptotic results are introduced for the outage probability, the average BER and the ergodic capacity in terms of simple elementary functions. For the capacity, novel asymptotic results at low and high SNR regimes are also derived through the moments. All the analytical results are verified via computer-based Monte-carlo simulations.

  19. Design of network-coding based multi-edge type LDPC codes for multi-source relaying systems

    CERN Document Server

    Li, Jun; Malaney, Robert; Yuan, Jinhong

    2009-01-01

    In this paper we investigate a multi-source LDPC scheme for a Gaussian relay system, where M sources communicate with the destination under the help of a single relay (M-1-1 system). Since various distributed LDPC schemes in the cooperative single-source system, e.g. bilayer LDPC and bilayer multi-edge type LDPC (BMET-LDPC), have been designed to approach the Shannon limit, these schemes can be applied to the $M-1-1$ system by the relay serving each source in a round-robin fashion. However, such a direct application is not optimal due to the lack of potential joint processing gain. In this paper, we propose a network coded multi-edge type LDPC (NCMET-LDPC) scheme for the multi-source scenario. Through an EXIT analysis, we conclude that the NCMET-LDPC scheme achieves higher extrinsic mutual information, relative to a separate application of BMET-LDPC to each source. Our new NCMET-LDPC scheme thus achieves a higher threshold relative to existing schemes.

  20. Integration of Mobil Satellite and Cellular Systems

    Science.gov (United States)

    Drucker, E. H.; Estabrook, P.; Pinck, D.; Ekroot, L.

    1993-01-01

    By integrating the ground based infrastructure component of a mobile satellite system with the infrastructure systems of terrestrial 800 MHz cellular service providers, a seamless network of universal coverage can be established.

  1. Experimental millimeter-wave satellite communications system

    Science.gov (United States)

    Suzuki, Yoshiaki; Shimada, Masaaki; Arimoto, Yoshinori; Shiomi, Tadashi; Kitazume, Susumu

    This paper describes an experimental system of millimeter-wave satellite communications via Japan's Engineering Test Satellite-VI (ETS-VI) and a plan of experiments. Two experimental missions are planned using ETS-VI millimeter-wave (43/38 GHz bands) transponder, considering the millimeter-wave characteristics such as large transmission capacity and possibility to construct a small earth station with a high gain antenna. They are a personal communication system and an inter-satellite communication system. Experimental system including the configuration and the fundamental functions of the onboard transponder and the outline of the experiments are presented.

  2. Satellite Sanitary Systems in Kampala, Uganda

    NARCIS (Netherlands)

    Letema, S.; Van Vliet, B.; Van Lier, J.B.

    2011-01-01

    Satellite sewage collection and treatment systems have been independently developed and managed in East African cities outside the centrally planned and sewered areas. A satellite approach is a promising provisioning option parallel to public sewerage for middle- and high-income residential areas, e

  3. Satellite Sanitary Systems in Kampala, Uganda

    NARCIS (Netherlands)

    Letema, S.C.; Vliet, van B.J.M.; Lier, van J.B.

    2012-01-01

    Satellite sewage collection and treatment systems have been independently developed and managed in East African cities outside the centrally planned and sewered areas. A satellite approach is a promising provisioning option parallel to public sewerage for middle- and high-income residential areas, e

  4. Cooperative jamming power control to enhance secrecy communications of AF Relaying systems for Rayleigh fading channel

    KAUST Repository

    Park, Kihong

    2012-09-01

    In this paper, we investigate secrecy communications in two-hop wireless relaying networks which consist of one source, one amplify-and-forward (AF) relay, one legitimate destination, and one eavesdropper. To prevent the eavesdropper from intercepting the source message, we make the destination send the intended noise to the AF relay during the first phase. This is referred to as cooperative jamming. According to the channel information at the destination, we address two types of jamming power allocation; (i) rate-optimal power allocation and (ii) outage-optimal power allocation. More specifically, without the instantaneous channel knowledge for the eavesdropper side, the outage probability of the secrecy rate is minimized with respect to the intended noise power level. We show that the outage-optimal allocation gives almost the same outage probability as the rateoptimal one. In addition, the jamming power consumption can be significantly reduced compared to the fixed and rate-optimal power allocation methods. © 2012 IEEE.

  5. Alternate transmission with half-duplex relaying in MIMO interference relay networks

    KAUST Repository

    Park, Seongho

    2013-12-01

    In this paper, we consider an alternate transmission scheme for a multiple-input multiple-output interference relay channel where multiple sources transmit their own signals to their corresponding destinations via one of two relaying groups alternately every time phase. Each of the relaying groups has arbitrary number of relays, and each relay operates in half-duplex amplify-and-forward mode. In our scheme, the received signals at the relay nodes consist of desired signals and two different interference signals such as the inter-source interferences and the inter-group interferences which are caused by the phase incoherence of relaying. As such, we propose an iterative interference alignment algorithm to mitigate the interferences. We show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying system in the interference relay channels. © 2013 IEEE.

  6. Bit Error-Rate Minimizing Detector for Amplify-and-Forward Relaying Systems Using Generalized Gaussian Kernel

    KAUST Repository

    Ahmed, Qasim Zeeshan

    2013-01-01

    In this letter, a new detector is proposed for amplifyand- forward (AF) relaying system when communicating with the assistance of relays. The major goal of this detector is to improve the bit error rate (BER) performance of the receiver. The probability density function is estimated with the help of kernel density technique. A generalized Gaussian kernel is proposed. This new kernel provides more flexibility and encompasses Gaussian and uniform kernels as special cases. The optimal window width of the kernel is calculated. Simulations results show that a gain of more than 1 dB can be achieved in terms of BER performance as compared to the minimum mean square error (MMSE) receiver when communicating over Rayleigh fading channels.

  7. Reliability Growth Analysis of Satellite Systems

    Science.gov (United States)

    2012-09-01

    obtained. In addition, the Cumulative Intensity Function ( CIF ) of a family of satellite systems was analyzed to assess its similarity to that of a...parameters are obtained. In addition, the Cumulative Intensity Function ( CIF ) of a family of satellite systems was analyzed to assess its similarity to that...System Figures 7a through 7i display the real CIF for a variety of GOES missions. These cumulative intensity functions have shapes similar to the

  8. Uplink Capacity of 802.16j Mobile Multihop Relay Networks with Transparent Relays

    DEFF Research Database (Denmark)

    Wang, Hua; Andrews, Jeffrey G.; Iversen, Villy Bæk

    2009-01-01

    -input multi-output (MIMO) transmission is applied in the relay link. We derived the cell coverage and average spectral efficiency, as well as the system Erlang capacity supporting both voice and data traffic. The numerical results show that MIMO transmission in the relay link can significantly improve the end...... in the relay link, significant capacity gains can be achieved with a two-hop 802.16J relay system compared to the conventional single-hop 802.16e system....

  9. Networks systems and operations. [wideband communication techniques for data links with satellites

    Science.gov (United States)

    1975-01-01

    The application of wideband communication techniques for data links with satellites is discussed. A diagram of the demand assigned voice communications system is provided. The development of prototype integrated spacecraft paramps at S- and C-bands is described and the performance of space-qualified paramps is tabulated. The characteristics of a dual parabolic cylinder monopulse zoom antenna for use with the tracking and data relay satellite system (TDRSS) are analyzed. The development of a universally applicable transponder at S-band is reported. A block diagram of the major subassemblies of the S-band transponder is included. The technology aspects of network timing and synchronization of communication systems are to show the use of the Omega navigation system. The telemetry data compression system used during the Skylab program is evaluated.

  10. A new digital land mobile satellite system

    Science.gov (United States)

    Schneider, Philip

    A description is given of the different digital services planned to be carried over existing and planned mobile satellite systems. These systems are then compared with analog services in terms of bandwidth and power efficiency. This comparison provides the rationale for the establishment of a digital land mobile satellite service (DLMSS) to use frequencies that are currently available but not yet assigned to a domestic mobile satellite system in the United States. The focus here is on the expected advantages of digital transmission techniques in accommodating additional mobile satellite systems in this portion of the spectrum, and how such techniques can fully satisfy voice, data and facsimile mobile communications requirements in a cost effective manner. A description is given of the system architecture of the DMLSS service proposed by the Geostar Messaging Corporation (GMC) and the market potential of DLMSS.

  11. Mobile relays for enhanced broadband connectivity in high speed train systems

    KAUST Repository

    Yaacoub, Elias E.

    2014-09-01

    With the introduction of wireless modems and smart phones, the passenger transport industry is witnessing a high demand to ensure not only the safety of the trains, but also to provide users with Internet access all the time inside the train. When the Mobile Terminal (MT) communicates directly with the Base Station (BS), it will experience a severe degradation in the Quality of Service due to the path loss and shadowing effects as the wireless signal is traveling through the train. In this paper, we study the performance in the case of relays placed on top of each train car. In the proposed approach, these relays communicate with the cellular BS on one hand, and with the MTs inside the train cars on the other hand, using the Long Term Evolution (LTE) cellular technology. A low complexity heuristic LTE radio resource management approach is proposed and compared to the Hungarian algorithm, both in the presence and absence of the relays. The presence of the relays is shown to lead to significant enhancements in the effective data rates of the MTs. In addition, the proposed resource management approach is shown to reach a performance close to the optimal Hungarian algorithm. © 2014 Elsevier B.V.

  12. Cellular Systems with Full-Duplex Compress-and-Forward Relaying and Cooperative Base Stations

    CERN Document Server

    Somekh, Oren; Poor, H Vincent; Shamai, Shlomo

    2008-01-01

    In this paper the advantages provided by multicell processing of signals transmitted by mobile terminals (MTs) which are received via dedicated relay terminals (RTs) are studied. It is assumed that each RT is capable of full-duplex operation and receives the transmission of adjacent relay terminals. Focusing on intra-cell TDMA and non-fading channels, a simplified relay-aided uplink cellular model based on a model introduced by Wyner is considered. Assuming a nomadic application in which the RTs are oblivious to the MTs' codebooks, a form of distributed compress-and-forward (CF) scheme with decoder side information is employed. The per-cell sum-rate of the CF scheme is derived and is given as a solution of a simple fixed point equation. This achievable rate reveals that the CF scheme is able to completely eliminate the inter-relay interference, and it approaches a ``cut-set-like'' upper bound for strong RTs transmission power. The CF rate is also shown to surpass the rate of an amplify-and-forward scheme via ...

  13. China's Meteorological Satellite Application System

    Institute of Scientific and Technical Information of China (English)

    Zhang Jiashen

    2008-01-01

    @@ (Continued) Applications In Global Environment And Natural Disaster Monitoring 1) Application in world crop yield estimation China is now one of the few nations in the world that can provide operational service with both GEO and polar-orbit meteorological satellites.

  14. Alignments between galaxies, satellite systems and haloes

    CERN Document Server

    Shao, Shi; Frenk, Carlos S; Gao, Liang; Crain, Robert A; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

    2016-01-01

    The spatial distribution of the satellite populations of the Milky Way and Andromeda are puzzling in that they are nearly perpendicular to the disks of their central galaxies. To understand the origin of such configurations we study the alignment of the central galaxy, satellite system and dark matter halo in the largest of the "Evolution and Assembly of GaLaxies and their Environments" (EAGLE) simulation. We find that centrals and their satellite systems tend to be well aligned with their haloes, with a median misalignment angle of $33^{\\circ}$ in both cases. While the centrals are better aligned with the inner $10$ kpc halo, the satellite systems are better aligned with the entire halo indicating that satellites preferentially trace the outer halo. The central - satellite alignment is weak (median misalignment angle of $52^{\\circ}$) and we find that around $20\\%$ of systems have a misalignment angle larger than $78^{\\circ}$, which is the value for the Milky Way. The central - satellite alignment is a conseq...

  15. Coordinated Transmission of Interference Mitigation and Power Allocation in Two-User Two-Hop MIMO Relay Systems

    Directory of Open Access Journals (Sweden)

    Hee-Nam Cho

    2010-01-01

    Full Text Available This paper considers coordinated transmission for interference mitigation and power allocation in a correlated two-user two-hop multi-input multioutput (MIMO relay system. The proposed transmission scheme utilizes statistical channel state information (CSI (e.g., transmit correlation to minimize the cochannel interference (CCI caused by the relay. To this end, it is shown that the CCI can be represented in terms of the eigenvalues and the angle difference between the eigenvectors of the transmit correlation matrix of the intended and CCI channel, and that the condition minimizing the CCI can be characterized by the correlation amplitude and the phase difference between the transmit correlation coefficients of these channels. Then, a coordinated user-scheduling strategy is designed with the use of eigen-beamforming to minimize the CCI in an average sense. The transmit power of the base station and relay is optimized under separate power constraint. Analytic and numerical results show that the proposed scheme can maximize the achievable sum rate when the principal eigenvectors of the transmit correlation matrix of the intended and the CCI channel are orthogonal to each other, yielding a sum rate performance comparable to that of the minimum mean-square error-based coordinated beamforming which uses instantaneous CSI.

  16. Satellite power system (SPS) initial insurance evaluation

    Energy Technology Data Exchange (ETDEWEB)

    None

    1980-09-01

    The beginning of a process to educate the insurance industry about the Satellite Power System is reported. The report is divided into three sections. In the first section a general history describes how space risks are being insured today. This is followed by an attempt to identify the major risks inherent to the SPS. The final section presents a general projection of insurance market reactions to the Satellite Power System.

  17. 49 CFR 236.52 - Relayed cut-section.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Relayed cut-section. 236.52 Section 236.52...: All Systems Track Circuits § 236.52 Relayed cut-section. Where relayed cut-section is used in... shall be open and the track circuit shunted when the track relay at such cut-section is in deenergized...

  18. Satellite Application for Disaster Management Information Systems

    Science.gov (United States)

    Okpanachi, George

    Abstract Satellites are becoming increasingly vital to modern day disaster management activities. Earth observation (EO) satellites provide images at various wavelengths that assist rapid-mapping in all phases of the disaster management cycle: mitigation of potential risks in a given area, preparedness for eventual disasters, immediate response to a disaster event, and the recovery/reconstruction efforts follo wing it. Global navigation satellite systems (GNSS) such as the Global Positioning System (GPS) assist all the phases by providing precise location and navigation data, helping manage land and infrastructures, and aiding rescue crews coordinate their search efforts. Effective disaster management is a complex problem, because it involves many parameters, which are usually not easy to measure and even identify: Analysis of current situation, planning, optimum resource management, coordination, controlling and monitoring current activities and making quick and correct decisions are only some of these parameters, whose complete list is very long. Disaster management information systems (DMIS) assist disaster management to analyse the situation better, make decisions and suggest further actions following the emergency plans. This requires not only fast and thorough processing and optimization abilities, but also real-time data provided to the DMIS. The need of DMIS for disaster’s real-time data can be satisfied by small satellites data utilization. Small satellites can provide up-to-data, plus a better media to transfer data. This paper suggests a rationale and a framework for utilization of small Satellite data by DMIS. DMIS should be used ‘’before’’, ‘’during’’ and ‘’after’’ the disasters. Data provided by the Small Satellites are almost crucial in any period of the disasters, because early warning can save lives, and satellite data may help to identify disasters before they occur. The paper also presents’ ‘when’’,

  19. Science Hybrid Orbiter and Lunar Relay (SCHOLR) Architecture and Design

    Science.gov (United States)

    Trase, Kathryn K.; Barch, Rachel A.; Chaney, Ryan E.; Coulter, Rachel A.; Gao, Hui; Huynh, David P.; Iaconis, Nicholas A.; MacMillan, Todd S.; Pitner, Gregory M.; Schwab, Devin T.

    2011-01-01

    Considered both a stepping-stone to deep space and a key to unlocking the mysteries of planetary formation, the Moon offers a unique opportunity for scientific study. Robotic precursor missions are being developed to improve technology and enable new approaches to exploration. Robots, lunar landers, and satellites play significant roles in advancing science and technologies, offering close range and in-situ observations. Science and exploration data gathered from these nodes and a lunar science satellite is intended to support future human expeditions and facilitate future utilization of lunar resources. To attain a global view of lunar science, the nodes will be distributed over the lunar surface, including locations on the far side of the Moon. Given that nodes on the lunar far side do not have direct line-of-sight for Earth communications, the planned presence of such nodes creates the need for a lunar communications relay satellite. Since the communications relay capability would only be required for a small portion of the satellite s orbit, it may be possible to include communication relay components on a science spacecraft. Furthermore, an integrated satellite has the potential to reduce lunar surface mission costs. A SCience Hybrid Orbiter and Lunar Relay (SCHOLR) is proposed to accomplish scientific goals while also supporting the communications needs of landers on the far side of the Moon. User needs and design drivers for the system were derived from the anticipated needs of future robotic and lander missions. Based on these drivers and user requirements, accommodations for communications payload aboard a science spacecraft were developed. A team of interns identified and compared possible SCHOLR architectures. The final SCHOLR architecture was analyzed in terms of orbiter lifetime, lunar surface coverage, size, mass, power, and communications data rates. This paper presents the driving requirements, operational concept, and architecture views for SCHOLR

  20. Odyssey, an optimized personal communications satellite system

    Science.gov (United States)

    Rusch, Roger J.

    Personal communications places severe demands on service providers and transmission facilities. Customers are not satisfied with the current levels of service and want improvements. Among the characteristics that users seek are: lower service rates, hand held convenience, acceptable time delays, ubiquitous service, high availability, reliability, and high quality. The space industry is developing commercial space systems for providing mobile communications to personal telephones. Provision of land mobile satellite service is fundamentally different from the fixed satellite service provided by geostationary satellites. In fixed service, the earth based antennas can depend on a clear path from user to satellite. Mobile users in a terrestrial environment commonly encounter blockage due to vegetation, terrain or buildings. Consequently, high elevation angles are of premium value. TRW studied the issues and concluded that a Medium Earth Orbit constellation is the best solution for Personal Communications Satellite Service. TRW has developed Odyssey, which uses twelve satellites in medium altitude orbit to provide personal communications satellite service. The Odyssey communications system projects a multibeam antenna pattern to the Earth. The attitude control system orients the satellites to ensure constant coverage of land mass and coastal areas. Pointing can be reprogrammed by ground control to ensure optimized coverage of the desired service areas. The payload architecture features non-processing, "bent pipe" transponders and matrix amplifiers to ensure dynamic power delivery to high demand areas. Circuit capacity is 3000 circuits per satellite. Each satellite weighs 1917 kg (4226 pounds) at launch and the solar arrays provide 3126 Watts of power. Satellites are launched in pairs on Ariane, Atlas, or other vehicles. Each satellite is placed in a circular orbit at an altitude of 10,354 km. There are three orbit planes inclined at 55° to the equatorial plane

  1. A Space Based Solar Power Satellite System

    Science.gov (United States)

    Engel, J. M.; Polling, D.; Ustamujic, F.; Yaldiz, R.; et al.

    2002-01-01

    (SPoTS) supplying other satellites with energy. SPoTS is due to be commercially viable and operative in 2020. of Technology designed the SPoTS during a full-time design period of six weeks as a third year final project. The team, organized according to the principles of systems engineering, first conducted a literature study on space wireless energy transfer to select the most suitable candidates for use on the SPoTS. After that, several different system concepts have been generated and evaluated, the most promising concept being worked out in greater detail. km altitude. Each SPoTS satellite has a 50m diameter inflatable solar collector that focuses all received sunlight. Then, the received sunlight is further redirected by means of four pointing mirrors toward four individual customer satellites. A market-analysis study showed, that providing power to geo-stationary communication satellites during their eclipse would be most beneficial. At arrival at geo-stationary orbit, the focused beam has expended to such an extent that its density equals one solar flux. This means that customer satellites can continue to use their regular solar arrays during their eclipse for power generation, resulting in a satellite battery mass reduction. the customer satellites in geo-stationary orbit, the transmitted energy beams needs to be pointed with very high accuracy. Computations showed that for this degree of accuracy, sensors are needed, which are not mainstream nowadays. Therefore further research must be conducted in this area in order to make these high-accuracy-pointing systems commercially attractive for use on the SPoTS satellites around 2020. Total 20-year system lifetime cost for 18 SPoT satellites are estimated at approximately USD 6 billion [FY2001]. In order to compete with traditional battery-based satellite power systems or possible ground based wireless power transfer systems the price per kWh for the customer must be significantly lower than the present one

  2. Resource allocation based on genetic algorithm for multi-hop OFDM system with non-regenerative relaying

    Institute of Scientific and Technical Information of China (English)

    SHI Jie; XU Wen-jun; HE Zhi-qiang; NIU Kai; WU Wei-ling

    2009-01-01

    This article investigates resource allocation in multi-hop orthogonal frequency division multiplexing (OFDM) system with amplifying-and-forwarding relaying to maximize the end-to-end capacity. Most existing methods for multi-hop system focus on power allocation or subcarrier selection separately, but joint resource allocation is rarely considered due to the absence of effective interaction schemes. In this work, a novel joint resource allocation methodology is proposed based on Partheno genetic algorithm (PGA), which produces excellent subcarrier allocation set (referred to as individual in PGA) with higher capacity by evolution operator generation by generation. In addition, an adaptive power allocation is also designed to evaluate the fitness of PGA and further enhance the system capacity. Both theoretical analysis and simulated results show the effectiveness of the proposed joint strategy. It outperforms the traditional method by as much as 40% capacity improvement for 3-hop relaying system when system power is high, and obtains much more capacity enhancement percent under conditions of low system power.

  3. Application of a proposed overcurrent relay in radial distribution networks

    Energy Technology Data Exchange (ETDEWEB)

    Conde, A.; Vazquez, E. [Universidad Autonoma de Nuevo Leon, Facultad de Ingenieria Mecanica y Electrica, A.P. 36-F, CU, CP 66450, San Nicolas de los Garza, Nuevo Leon (Mexico)

    2011-02-15

    This paper contains the application criteria and coordination process for a proposed overcurrent relay in a radial power system with feed from one or multiple sources. This relay uses independent functions to detect faults and to calculate the operation time. Also this relay uses a time element function that allows it to reduce the time relay operation, enhancing the backup protection. Some of the proposed approaches improve the sensitivity of the relay. The selection of the best approach in the proposed relay is defined by the needs of the application. The proposed protection can be considered as an additional function protection to conventional overcurrent relays. (author)

  4. Application of Hybrid Real-Time Power System Simulator for Designing and Researching of Relay Protection and Automation

    Science.gov (United States)

    Borovikov, Yu S.; Sulaymanov, A. O.; Andreev, M. V.

    2015-10-01

    Development, research and operation of smart grids (SG) with active-adaptive networks (AAS) are actual tasks for today. Planned integration of high-speed FACTS devices greatly complicates complex dynamic properties of power systems. As a result the operating conditions of equipment of power systems are significantly changing. Such situation creates the new actual problem of development and research of relay protection and automation (RPA) which will be able to adequately operate in the SGs and adapt to its regimes. Effectiveness of solution of the problem depends on using tools - different simulators of electric power systems. Analysis of the most famous and widely exploited simulators led to the conclusion about the impossibility of using them for solution of the mentioned problem. In Tomsk Polytechnic University developed the prototype of hybrid multiprocessor software and hardware system - Hybrid Real-Time Power System Simulator (HRTSim). Because of its unique features this simulator can be used for solution of mentioned tasks. This article introduces the concept of development and research of relay protection and automation with usage of HRTSim.

  5. Optimal allocation of fault current limiters for sustaining overcurrent relays coordination in a power system with distributed generation

    Directory of Open Access Journals (Sweden)

    A. Elmitwally

    2015-12-01

    Full Text Available This paper addresses the problem of overcurrent relays (OCRs coordination in the presence of DGs. OCRs are optimally set to work in a coordinated manner to isolate faults with minimal impacts on customers. The penetration of DGs into the power system changes the fault current levels seen by the OCRs. This can deteriorate the coordinated operation of OCRs. Operation time difference between backup and main relays can be below the standard limit or even the backup OCR can incorrectly work before the main OCR. Though resetting of OCRs is tedious especially in large systems, it cannot alone restore the original coordinated operation in the presence of DGs. The paper investigates the optimal utilization of fault current limiters (FCLs to maintain the directional OCRs coordinated operation without any need to OCRs resetting irrespective of DGs status. It is required to maintain the OCRs coordination at minimum cost of prospective FCLs. Hence, the FCLs location and sizing problem is formulated as a constrained multi-objective optimization problem. Multi-objective particle swarm optimization is adopted for solving the optimization problem to determine the optimal locations and sizes of FCLs. The proposed algorithm is applied to meshed and radial power systems at different DGs arrangements using different types of FCLs. Moreover, the OCRs coordination problem is studied when the system includes both directional and non-directional OCRs. Comparative analysis of results is provided.

  6. Relay race

    CERN Multimedia

    Staff Association

    2012-01-01

    The CERN Relay Race will take place around the Meyrin site on Thursday 24th May at 12:00. This annual event is for teams of six runners covering distances of 1000 m, 800 m, 800 m, 500 m, 500 m and 300 m respectively. Teams may be entered in the Seniors, Veterans, Ladies, Mixed or Open categories. There will also this year be a Nordic Walking event, as part of the Medical Service’s initiative “Move more, eat better!” The registration fee is 10 CHF per runner, and each runner will receive a souvenir prize. There will be a programme of entertainment from 12:00 on the arrival area (the lawn in front of Restaurant 1): 12:00 - 12:45  Music from the Old Bottom Street band 12:15 Start of the race 12:45 - 13h Demonstrations by the Fitness club and Dancing club 13:00 Results and prize giving (including a raffle to win an iPad2 3G offered by the Micro club) 13:20 à 14:00 Music from “What’s next” And many information st...

  7. Verifying command sequences for satellite systems

    Science.gov (United States)

    Peters, James F., III; Ramanna, Sheela

    1992-10-01

    We present a formal basis for the design of a Checker used in validating safe schedules and in selecting error recovery schedules for satellite control systems. This design includes a high-level specification of Checker behavior and properties (called flight rules) of safe schedules. Specifications are written in Timed Linear Logic (TLL). Validation of schedules is performed in terms of real-time telemetry and deduction system proof rules. Telemetry (state information for satellite subsystems) serves as input to the Checker. Detection of violation of a flight rule by the Checker results in the selection of a contingency plan (error recovery schedule). The Checker is illustrated in terms of the TOPEX/Poseidon Oceanographic Satellite System.

  8. Augmented tracking and acquisition system for GBL satellite illumination

    Science.gov (United States)

    Brodsky, Aaron; Goodrich, Alan; Lawson, David G.; Holm, Richard W.

    1991-08-01

    The Augmented Tracking and Acquisition System (ATAS) provides the tracking acquisition aids, line-of-sight stabilization, and active closed-loop beam centering functions at two ground-based laser tracking sites for the Relay Mirror Experiment (RME). Simultaneous, steady illumination of the RME spacecraft with both ground beacons allows for successful beam relay between the two sites off of the orbiting mirror. Described in this paper is an overview of the functions, control system architectures, major subsystem components (steering mirrors and sensors), and mission operation of the ATAS subsystems. A brief discussion of ATAS evolution is included to show that versatility is needed for success.

  9. A relativistic and autonomous navigation satellite system

    CERN Document Server

    Delva, Pacôme; Kostić, Uros; Carloni, Sante

    2011-01-01

    A relativistic positioning system has been proposed by Bartolom\\'e Coll in 2002. Since then, several group developed this topic with different approaches. I will present a work done in collaboration with Ljubljana University and the ESA Advanced Concepts Team. We developed a concept, Autonomous Basis of Coordinates, in order to take advantage of the full autonomy of a satellite constellation for navigation and positioning, by means of satellite inter-links. I will present the advantages of this new paradigm and a number of potential application for reference systems, geophysics and relativistic gravitation.

  10. Advantages of Hybrid Global Navigation Satellite Systems

    Directory of Open Access Journals (Sweden)

    Asim Bilajbegović

    2007-05-01

    Full Text Available In a decision-making situation, what kind of GPS equipment to purchase, one always has a dilemma, tobuy hybrid (GPS+GLONASS or only GPS receivers? In the case of completeness of the GLONASS satellite system, this dilemma probably would not have existed. The answer to this dilemma is given in the present paper, but for the constellation of the GLONASS satellites in summer 2006 (14 satellites operational. Due to the short operational period of these satellites (for example GLONASS-M, 5 years, and not launching new ones, at this moment (February 25, 2007, only 10 satellites are operational. For the sake of research and giving answers to these questions, about 252 RTK measurements have been done using (GPS and GNSS receivers, on points with different obstructions of horizon. Besides that, initialisation time has been investigated for both systems from about 480 measurements, using rover's antenna with metal cover, during a time interval of 0.5, 2 and 5 seconds. Moreover, accuracy, firmware declared accuracy and redundancy of GPS and GNSS RTK measurements have been investigating.  

  11. Providing a Distance Bounding Protocol Named Pasargad in order to Defend against Relay Attacks on RFID-Based Electronic Voting System

    Directory of Open Access Journals (Sweden)

    Mohammad Arjmand

    2011-08-01

    Full Text Available The most important characteristic of RFID-based electronic voting system compared to traditional votingsystem is that votes in the electronic system are as contactless smart cards in place of paper ballots. Forcasting ballots, voters use a computer terminal to write their choices (their chosen candidates intocontactless smart cards and then put the smart card inside the box. The most important threat forRFIDsystems is information robbery and relay attacks. In this article, by designing a protocol calledDistance Bounding Protocol it is tried to defend these systems against relay attacks.

  12. Low-Complexity Combining Schemes in Dual-Hop AF Relaying Systems

    KAUST Repository

    Gaaloul, Fakhreddine

    2011-07-18

    This paper investigates the performance of different low-complexity combining schemes in the context of dual-hop amplify-and-forward (AF) relaying networks. It is assumed that the relay uses single transmit (receive) antenna due to space limitation and to reduce the processing complexity. On the other hand, the transmitter and the receiver use antenna arrays to improve the overall diversity gain. However, this gain is achieved at the expense of increased processing complexity and power consumption. To this end, some combining schemes aiming at reducing the processing complexity and decreasing the number of active receive channels are investigated. Through the analysis, new formulas for the end-to-end signal-to-noise ratio (SNR) statistics in slowly varying and frequency flat Rayleigh fading channels are derived, which are then used to present some performance measures. Numerical and simulation results are presented to clarify the trade-off between the achieved diversity gain and the receive processing complexity. © 2011 IEEE.

  13. A native IP satellite communications system

    Science.gov (United States)

    Koudelka, O.; Schmidt, M.; Ebert, J.; Schlemmer, H.; Kastner-Puschl, S.; Riedler, W.

    2004-08-01

    ≪ In the framework of ESA's ARTES-5 program the Institute of Applied Systems Technology (Joanneum Research) in cooperation with the Department of Communications and Wave Propagation has developed a novel meshed satellite communications system which is optimised for Internet traffic and applications (L*IP—Local Network Interconnection via Satellite Systems Using the IP Protocol Suite). Both symmetrical and asymmetrical connections are supported. Bandwidth on demand and guaranteed quality of service are key features of the system. A novel multi-frequency TDMA access scheme utilises efficient methods of IP encapsulation. In contrast to other solutions it avoids legacy transport network techniques. While the DVB-RCS standard is based on ATM or MPEG transport cells, the solution of the L*IP system uses variable-length cells which reduces the overhead significantly. A flexible and programmable platform based on Linux machines was chosen to allow the easy implementation and adaptation to different standards. This offers the possibility to apply the system not only to satellite communications, but provides seamless integration with terrestrial fixed broadcast wireless access systems. The platform is also an ideal test-bed for a variety of interactive broadband communications systems. The paper describes the system architecture and the key features of the system.

  14. Neptunian Satellites observed with Keck AO system

    Science.gov (United States)

    Marchis, F.; Urata, R.; de Pater, I.; Gibbard, S.; Hammel, H. B.; Berthier, J.

    2004-05-01

    The Neptunian system was observed on 9 different nights between July 2002 and October 2003 with the 10-m Keck telescope on Mauna Kea, Hawaii, and its facility instrument NIRC2 coupled with the Adaptive Optics system. Data were recorded in J (1.2μ m), and H (2.2μ m) bands. The angular resolution achieved on a one-minute integration time image is 0.50 arcsec, corresponding to a spatial resolution of 1100 km. The images display small structures such as the rings (de Pater et al. 2004), clouds in the atmosphere (Gibbard et al. 2003), and inner satellites, mainly Proteus, Larissa, Galatea, Despina, and Thalassa. On the 40 images, the positions and intensities of the satellites detected were accurately measured fitting the signal with a gaussian profile. The center of Neptune was obtained by fitting the disk position with an ellipse. After correcting for the detector distortion, we compared the satellite positions with the predicted ones delivered by several ephemerides. We used the JPL (NEP016 + NEP022 + DE405) and two IMCCE ephemerides, an old version (VSOP87+Owen et al., 1991) and a more recent one (DE405+Le Guyader et al., 1993). All cases, we confirmed the presence of an apparent shift between the predicted and the observed positions. Table 1 (see http://astron.berkeley.edu/ fmarchis/Science/Neptune/Satellites/) summarizes the mean distance of the shift for satellites most frequently observed and the various ephemerides. In this presentation, we will report the positions of the satellites, and present their color and possible photometric variations derived from the observations. This work has been partially supported by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under cooperative agreement No. AST - 9876783.

  15. Delayed Random Relays

    CERN Document Server

    Ohira, Toru

    2016-01-01

    We present here a system with collection of random walks relaying a signal in one dimension with a presence of a delay. We are interested in the time for a signal to travel from one end (start) to the other end (finish) of the lined group of random walkers. It is found that there is an optimal number of walkers for the signal to travel fastest if the delay is present. We discuss implications of this model and associated behaviors to physical and biological systems.

  16. Performance Analysis of Multibranch Dual-Hop Nonregenerative Relay Systems with EGC in Nakagami-m Channels

    Directory of Open Access Journals (Sweden)

    H. Suzuki

    2010-01-01

    Full Text Available The end-to-end performance of multibranch dual-hop wireless communication systems with nonregenerative relays and equal gain combiner (EGC at the destination over independent Nakagami-m fading channels is studied. We present new closed form expressions for probability distribution function (PDF and cumulative distribution function (CDF of end-to-end signal to noise ratio (SNR per branch in terms of Meijer's G function. From these results, analytical formulae for the moments of the output SNR, the average overall SNR, the amount of fading, and the spectral efficiency are also obtained in closed form. Instead of using moments-based approach to analyze the asymptotic error performance of the system, we employ the characteristic function (CHF method to calculate the average bit error probability (ABEP and the outage probability for several coherent and noncoherent modulation schemes. The accuracy of the analytical formulae is verified by various numerical results and simulations.

  17. Networks for Autonomous Formation Flying Satellite Systems

    Science.gov (United States)

    Knoblock, Eric J.; Konangi, Vijay K.; Wallett, Thomas M.; Bhasin, Kul B.

    2001-01-01

    The performance of three communications networks to support autonomous multi-spacecraft formation flying systems is presented. All systems are comprised of a ten-satellite formation arranged in a star topology, with one of the satellites designated as the central or "mother ship." All data is routed through the mother ship to the terrestrial network. The first system uses a TCP/lP over ATM protocol architecture within the formation the second system uses the IEEE 802.11 protocol architecture within the formation and the last system uses both of the previous architectures with a constellation of geosynchronous satellites serving as an intermediate point-of-contact between the formation and the terrestrial network. The simulations consist of file transfers using either the File Transfer Protocol (FTP) or the Simple Automatic File Exchange (SAFE) Protocol. The results compare the IF queuing delay, and IP processing delay at the mother ship as well as application-level round-trip time for both systems, In all cases, using IEEE 802.11 within the formation yields less delay. Also, the throughput exhibited by SAFE is better than FTP.

  18. Communications satellite system for Africa

    Science.gov (United States)

    Kriegl, W.; Laufenberg, W.

    1980-09-01

    Earlier established requirement estimations were improved upon by contacting African administrations and organizations. An enormous demand is shown to exist for telephony and teletype services in rural areas. It is shown that educational television broadcasting should be realized in the current African transport and communications decade (1978-1987). Radio broadcasting is proposed in order to overcome illiteracy and to improve educational levels. The technical and commercial feasibility of the system is provided by computer simulations which demonstrate how the required objectives can be fulfilled in conjunction with ground networks.

  19. Optimal Structure of Robust Linear Transceiver for Amplify-and-Forward Multi-Hop MIMO Relaying Systems

    CERN Document Server

    Xing, Chengwen; Ma, Shaodan; Kuang, Jingming; Wu, Yik-Chung

    2011-01-01

    In this paper, optimal linear transceiver designs for multi-hop amplify-and-forward (AF) Multiple-input Multiple-out (MIMO) relaying systems with Gaussian distributed channel estimation errors are investigated. Some commonly used transceiver design criteria such as weighted mean-square-error (MSE) minimization, mutual information maximization, worst MSE/MAX-MSE minimization and weighted sum-rate maximization, are taken into a single matrix-variate optimization problem. Exploiting majorization theory and properties of matrix-variate functions, the optimal structures of robust transceivers are derived. Based on the optimal structures, the original transceiver design problems are reduced to much simpler problems with only scalar variables whose solutions are readily obtained by iterative water-filling algorithms. A number of existing transceiver design algorithms are found to be special cases of the proposed solution. The performance advantages of the proposed robust designs are demonstrated by the simulation re...

  20. Joint Channel Estimation and Data Detection for Multihop OFDM Relaying System under Unknown Channel Orders and Doppler Frequencies

    CERN Document Server

    Min, Rui

    2012-01-01

    In this paper, channel estimation and data detection for multihop relaying orthogonal frequency division multiplexing (OFDM) system is investigated under time-varying channel. Different from previous works, which highly depend on the statistical information of the doubly-selective channel (DSC) and noise to deliver accurate channel estimation and data detection results, we focus on more practical scenarios with unknown channel orders and Doppler frequencies. Firstly, we integrate the multilink, multihop channel matrices into one composite channel matrix. Then, we formulate the unknown channel using generalized complex exponential basis expansion model (GCE-BEM) with a large oversampling factor to introduce channel sparsity on delay-Doppler domain. To enable the identification of nonzero entries, sparsity enhancing Gaussian distributions with Gamma hyperpriors are adopted. An iterative algorithm is developed under variational inference (VI) framework. The proposed algorithm iteratively estimate the channel, re...

  1. Telemetry data via communications relay

    Science.gov (United States)

    Strock, O. J.; Witchey, Michael

    This paper responds to a test range engineer's need to relay one or more channels of various types of telemetry data from a remotely-located receiving station to the central telemetry station at range headquarters for real-time processing and display. Several types of data are identified, and specific equipment and technology for multiplexing, transmission, and demultiplexing up to eight streams from a variety of sources is discussed. The widely-used T3 communications link, also known as DS-3, can relay data via satellite, microwave link, or other high-speed path at 44.736 megabits per second, of which about 95 percent can be actual telemetry data; other standard links operate at lower aggregate rates. Several links and rates are discussed, with emphasis in the high-rate T3 link.

  2. 49 CFR 236.589 - Relays.

    Science.gov (United States)

    2010-10-01

    ... Cab Signal Systems Inspection and Tests; Locomotive § 236.589 Relays. (a) Each relay shall be removed from service, subjected to thorough test, necessary repairs and adjustments made, and shall not be... spring tension to return contacts to deenergized position in noncoded continuous inductive...

  3. Technology for a quasi-GSO satellite communications system

    OpenAIRE

    Katagi, T.; Yonezawa, R.; Chiba, I.; Urasaki, S.

    1999-01-01

    In this paper, a satellite communications system using a Quasi Geostationary Satellite Orbit (Quasi-GSO) is proposed. A 24-hour period Quasi-GSO system could give high quality communication to high latitude regions with its satellites observed from earth stations having high elevation angles. In this paper, a system concept and a deployable flat antenna with light weight antenna elements are described proposing it to be a good candidate for mobile communications satellite use.

  4. The NOAA Satellite Observing System Architecture Study

    Science.gov (United States)

    Volz, Stephen; Maier, Mark; Di Pietro, David

    2016-01-01

    NOAA is beginning a study, the NOAA Satellite Observing System Architecture (NSOSA) study, to plan for the future operational environmental satellite system that will follow GOES and JPSS, beginning about 2030. This is an opportunity to design a modern architecture with no pre-conceived notions regarding instruments, platforms, orbits, etc. The NSOSA study will develop and evaluate architecture alternatives to include partner and commercial alternatives that are likely to become available. The objectives will include both functional needs and strategic characteristics (e.g., flexibility, responsiveness, sustainability). Part of this study is the Space Platform Requirements Working Group (SPRWG), which is being commissioned by NESDIS. The SPRWG is charged to assess new or existing user needs and to provide relative priorities for observational needs in the context of the future architecture. SPRWG results will serve as input to the process for new foundational (Level 0 and Level 1) requirements for the next generation of NOAA satellites that follow the GOES-R, JPSS, DSCOVR, Jason-3, and COSMIC-2 missions.

  5. Incoherent correlator system for satellite orientation control

    Science.gov (United States)

    Kouris, Aristodemos; Young, Rupert C. D.; Chatwin, Christopher R.; Birch, Philip M.

    2002-03-01

    An incoherent correlator configuration is proposed and experimentally demonstrated that is capable of recognizing star patterns. The device may thus be employed for the orientation and navigation of a satellite or spacecraft. The correlator employs starlight directly and requires no laser or input spatial light modulator for operation. The filter is constructed form an array of mirrors that may be individually appropriately tilted so as recognize a particular star arrangement. The only other components of the system are a converging lens and CCD array detector. The device is capable of determining the pointing direction and rotation of a satellite or space vehicle. Experimental results employing the mirror array device illuminated with a point source early to simulate starlight are presented.

  6. An Opportunistic Relaying Selection Scheme Based on Relay Fairness

    Directory of Open Access Journals (Sweden)

    Ting An

    2013-07-01

    Full Text Available Opportunistic relaying scheme is a single cooperative relay selection method based on Channel State Information. However, the failure probability of the best relay selection may become unacceptable when the number of relays increases. Although most of the existing solutions can reduce the failure probability of relay selection, they ignore the fairness of the relay selection. In order to improve the fairness of the relay selection without affecting the failure probability of the best relay selection, we propose a modified practical best relay selection scheme in this paper,  and by introducing proportional fair algorithm, the relay timer will be given a smaller correlation coefficient. The proposed method makes the probability of selection be improved. In the light of defined fairness factor, the relay fairness is represented. Simulation results show that the new algorithm can improve the fairness of the relay selection on the basis of maintaining the original failure probability of relay selection.

  7. On Alternate Relaying with Improper Gaussian Signaling

    KAUST Repository

    Gaafar, Mohamed

    2016-06-06

    In this letter, we investigate the potential benefits of adopting improper Gaussian signaling (IGS) in a two-hop alternate relaying (AR) system. Given the known benefits of using IGS in interference-limited networks, we propose to use IGS to relieve the inter-relay interference (IRI) impact on the AR system assuming no channel state information is available at the source. In this regard, we assume that the two relays use IGS and the source uses proper Gaussian signaling (PGS). Then, we optimize the degree of impropriety of the relays signal, measured by the circularity coefficient, to maximize the total achievable rate. Simulation results show that using IGS yields a significant performance improvement over PGS, especially when the first hop is a bottleneck due to weak source-relay channel gains and/or strong IRI.

  8. Partial relay selection in underlay cognitive networks with fixed gain relays

    KAUST Repository

    Hussain, Syed Imtiaz

    2012-05-01

    In a communication system with multiple cooperative relays, selecting the best relay utilizes the available spectrum more efficiently. However, selective relaying poses a different problem in underlay cognitive networks compared to the traditional cooperative networks due to interference thresholds to the primary users. In most cases, a best relay is the one which provides the maximum end-to-end signal to noise ratio (SNR). This approach needs plenty of instantaneous channel state information (CSI). The CSI burden could be reduced by partial relay selection. In this paper, a partial relay selection scheme is presented and analyzed for an underlay cognitive network with fixed gain relays operating in the vicinity of a primary user. The system model is adopted in a way that each node needs minimal CSI to perform its task. The best relay is chosen on the basis of maximum source to relay link SNR which then forwards the message to the destination. We derive closed form expressions for the received SNR distributions, system outage, probability of bit error and average channel capacity of the system. The derived results are confirmed through simulations. © 2012 IEEE.

  9. Performance limitations of relay neurons.

    Directory of Open Access Journals (Sweden)

    Rahul Agarwal

    Full Text Available Relay cells are prevalent throughout sensory systems and receive two types of inputs: driving and modulating. The driving input contains receptive field properties that must be transmitted while the modulating input alters the specifics of transmission. For example, the visual thalamus contains relay neurons that receive driving inputs from the retina that encode a visual image, and modulating inputs from reticular activating system and layer 6 of visual cortex that control what aspects of the image will be relayed back to visual cortex for perception. What gets relayed depends on several factors such as attentional demands and a subject's goals. In this paper, we analyze a biophysical based model of a relay cell and use systems theoretic tools to construct analytic bounds on how well the cell transmits a driving input as a function of the neuron's electrophysiological properties, the modulating input, and the driving signal parameters. We assume that the modulating input belongs to a class of sinusoidal signals and that the driving input is an irregular train of pulses with inter-pulse intervals obeying an exponential distribution. Our analysis applies to any [Formula: see text] order model as long as the neuron does not spike without a driving input pulse and exhibits a refractory period. Our bounds on relay reliability contain performance obtained through simulation of a second and third order model, and suggest, for instance, that if the frequency of the modulating input increases or the DC offset decreases, then relay increases. Our analysis also shows, for the first time, how the biophysical properties of the neuron (e.g. ion channel dynamics define the oscillatory patterns needed in the modulating input for appropriately timed relay of sensory information. In our discussion, we describe how our bounds predict experimentally observed neural activity in the basal ganglia in (i health, (ii in Parkinson's disease (PD, and (iii in PD during

  10. System implementation for Earth Radiation Budget Satellite System

    Science.gov (United States)

    Cooper, J. E.; Woerner, C. V.

    1978-01-01

    A description is presented of the instrument system which is needed for the Earth Radiation Budget Satellite System (ERBSS). The system is to be composed of instruments on two of NOAA's near-polar sun-synchronous Tiros-N/NOAA A through G series of operational satellites and on a NASA midinclination satellite of the Applications Explorer Mission (AEM) type referred to as ERBS-A/AEM. The Tiros-N/NOAA satellites will be in nominal 833 km altitude circular orbits with orbital inclinations of 98 deg. The AEM satellite will be in a circular orbit with an inclination of approximately 56 deg and a nominal altitude of 600 km. Each satellite will carry wide field-of-view (WFOV) and medium field-of-view (MFOV) sensors, a sensor for measuring the solar constant, and a narrow field-of-view (NFOV) cross-track scanner. The conceptual design of the W/MFOV instrument is discussed along with the conceptual design of the scanner.

  11. Digital, Satellite-Based Aeronautical Communication

    Science.gov (United States)

    Davarian, F.

    1989-01-01

    Satellite system relays communication between aircraft and stations on ground. System offers better coverage with direct communication between air and ground, costs less and makes possible new communication services. Carries both voice and data. Because many data exchanged between aircraft and ground contain safety-related information, probability of bit errors essential.

  12. Packet scheduling for OFDMA based relay networks

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The combination of relay networks with orthogonal frequency division multiple access (OFDMA) has been proposed as a promising solution for the next generation wireless system. Considering different traffic classes and user quality of service (QoS), three efficient scheduling algorithms are introduced in such networks. The round-robin (RR) algorithm in relay networks serves as a performance benchmark. Numerical results show that the proposed algorithms achieve significant improvement on system throughput and decrease system packet loss rate, compared with the RR and absence of relaying system (traditional network). Furthermore, comparisons have been carried out among the three proposed algorithms.

  13. CERN Relay Race

    CERN Multimedia

    CERN Running Club

    2010-01-01

    The CERN relay race will take place around the Meyrin site on Thursday 20 May, starting at 12.15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on the route, and how to register your team for the relay race, can be found at: https://espace.cern.ch/Running-Club/CERN-Relay

  14. Technical comparison of several global mobile satellite communications systems

    Science.gov (United States)

    Comparetto, Gary M.

    The era of satellite-based mobile satellite communications (MSC) systems started with the first MARISAT satellite which was launched into a geostationary orbit over the Pacific Ocean in 1976 to provide communications between ships and shore stations. The combination of high cost and unacceptably large equipment has kept the space-based MSC systems from appealing to the wider market of personal mobile communications. The progress made over the last ten years, however, in digital voice processing, satellite technology, and component miniaturization has resulted in the viability of satellite-based mobile satellite communications systems to meet the growing market in personal mobile communications using handsets similar to those currently in use with land-based cellular systems. Three of the more mature LEO/MEO satellite systems are addressed in this paper including GLOBALSTAR, Iridium, and Odyssey. The system architectures of each system are presented along with a description of the satellite and user handset designs and the multiaccess techniques employed. It will be shown that, although a number of similarities exist among the system addressed, each system is unique in a variety of significant design areas. It is concluded that the technical feasibility of satellite-based mobile satellite communications systems seems to be secure. It will be challenging, however, for the vendors to actually develop and deploy these systems in a cost effective, timely, and reliable way that meets a continually evolving set of requirements based upon a rapidly changing technology base.

  15. Optimal Release Control of Companion Satellite System Using Electromagnetic Forces

    Institute of Scientific and Technical Information of China (English)

    Zengwen Xu,Peng Shi; Yushan Zhao∗

    2015-01-01

    Electromagnetic forces generated by the inter⁃action of component satellites can be used to release companion satellites. Optimal release trajectories for companion satellite system using inter⁃electromagnetic forces were investigated. Firstly, nonlinear relative motion dynamic equations of a two⁃craft electromagnetic companion satellite system were derived in spatial polar coordinates. Then principles of electromagnetic satellite formation flying were introduced. Secondly, the characteristics of the electromagnetic companion satellites release were analyzed and optimal release trajectories of companion satellites using electromagnetic forces were obtained using Gauss pseudospectral method. Three performance criteria were chosen as minimum time, minimum acceleration of the separation distance and minimum control acceleration. Finally, three release examples including expansion along separation distance, rotation in orbital plane and stable formation reconfiguration were given to demonstrate the feasibility of this method. Results indicated that the release trajectories can converge to optimal solutions effectively and the concept of release companion satellites using electromagnetic forces is practicable.

  16. National Satellite Forest Monitoring systems for REDD+

    Science.gov (United States)

    Jonckheere, I. G.

    2012-12-01

    Reducing Emissions from Deforestation and Forest Degradation (REDD) is an effort to create a financial value for the carbon stored in forests, offering incentives for developing countries to reduce emissions from forested lands and invest in low-carbon paths to sustainable development. "REDD+" goes beyond deforestation and forest degradation, and includes the role of conservation, sustainable management of forests and enhancement of forest carbon stocks. In the framework of getting countries ready for REDD+, the UN-REDD Programme assists developing countries to prepare and implement national REDD+ strategies. For the monitoring, reporting and verification, FAO supports the countries to develop national satellite forest monitoring systems that allow for credible measurement, reporting and verification (MRV) of REDD+ activities. These are among the most critical elements for the successful implementation of any REDD+ mechanism. The UN-REDD Programme through a joint effort of FAO and Brazil's National Space Agency, INPE, is supporting countries to develop cost- effective, robust and compatible national monitoring and MRV systems, providing tools, methodologies, training and knowledge sharing that help countries to strengthen their technical and institutional capacity for effective MRV systems. To develop strong nationally-owned forest monitoring systems, technical and institutional capacity building is key. The UN-REDD Programme, through FAO, has taken on intensive training together with INPE, and has provided technical help and assistance for in-country training and implementation for national satellite forest monitoring. The goal of the support to UN-REDD pilot countries in this capacity building effort is the training of technical forest people and IT persons from interested REDD+ countries, and to set- up the national satellite forest monitoring systems. The Brazilian forest monitoring system, TerraAmazon, which is used as a basis for this initiative, allows

  17. Joint Polar Satellite System Common Ground System Overview

    Science.gov (United States)

    Jamilkowski, M. L.; Miller, S. W.; Grant, K. D.

    2012-12-01

    The National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) are jointly acquiring the next-generation civilian weather and environmental satellite system: the Joint Polar Satellite System (JPSS). JPSS will contribute the afternoon orbit component and ground processing system of the restructured National Polar-orbiting Operational Environmental Satellite System (NPOESS). As such, JPSS replaces the current Polar-orbiting Operational Environmental Satellites (POES) managed by NOAA and the ground processing component of both Polar-orbiting Operational Environmental Satellites and the Defense Meteorological Satellite Program (DMSP) replacement, previously known as the Defense Weather Satellite System (DWSS), managed by the Department of Defense (DoD). The JPSS satellites will carry a suite of sensors designed to collect meteorological, oceanographic, climatological, and solar-geophysical observations of the earth, atmosphere, and space. The ground processing system for JPSS is known as the JPSS Common Ground System (JPSS CGS), and consists of a Command, Control, and Communications Segment (C3S) and an Interface Data Processing Segment (IDPS). Both segments are developed by Raytheon Intelligence and Information Systems (IIS). The C3S currently flies the Suomi National Polar Partnership (Suomi NPP) satellite and transfers mission data from Suomi NPP and between the ground facilities. The IDPS processes Suomi NPP satellite data to provide Environmental Data Records (EDRs) to NOAA and DoD processing centers operated by the United States government. When the JPSS-1 satellite is launched in early 2017, the responsibilities of the C3S and the IDPS will be expanded to support both Suomi NPP and JPSS-1. The JPSS CGS currently provides data processing for Suomi NPP, generating multiple terabytes per day across over two dozen environmental data products; that workload will be multiplied by two when the JPSS-1 satellite is

  18. System architecture for the Canadian interim mobile satellite system

    Science.gov (United States)

    Shariatmadar, M.; Gordon, K.; Skerry, B.; Eldamhougy, H.; Bossler, D.

    1988-05-01

    The system architecture for the Canadian Interim Mobile Satellite Service (IMSS) which is planned for commencement of commercial service in late 1989 is reviewed. The results of an associated field trial program which was carried out to determine the limits of coverage and the preliminary performance characteristics of the system are discussed.

  19. Satellite power system (SPS) public outreach experiment

    Energy Technology Data Exchange (ETDEWEB)

    McNeal, S.R.

    1980-12-01

    To improve the results of the Satellite Power System (SPS) Concept Development and Evaluation Program, an outreach experiment was conducted. Three public interest groups participated: the L-5 Society (L-5), Citizen's Energy Project (CEP), and the Forum for the Advancement of Students in Science and Technology (FASST). Each group disseminated summary information about SPS to approximately 3000 constituents with a request for feedback on the SPS concept. The objectives of the outreach were to (1) determine the areas of major concern relative to the SPS concept, and (2) gain experience with an outreach process for use in future public involvement. Due to the combined efforts of all three groups, 9200 individuals/organizations received information about the SPS concept. Over 1500 receipients of this information provided feedback. The response to the outreach effort was positive for all three groups, suggesting that the effort extended by the SPS Project Division to encourage an information exchange with the public was well received. The general response to the SPS differed with each group. The L-5 position is very much in favor of SPS; CEP is very much opposed and FASST is relatively neutral. The responses are analyzed, and from the responses some questions and answers about the satellite power system are presented in the appendix. (WHK)

  20. Heart Monitoring By Satellite

    Science.gov (United States)

    1978-01-01

    The ambulance antenna shown is a specially designed system that allows satellite-relayed two-way communications between a moving emergency vehicle and a hospital emergency room. It is a key component of a demonstration program aimed at showing how emergency medical service can be provided to people in remote rural areas. Satellite communication permits immediate, hospital- guided treatment of heart attacks or other emergencies by ambulance personnel, saving vital time when the scene of the emergency is remote from the hospital. If widely adopted, the system could save tens of thousands of lives annually in the U.S. alone, medical experts say. The problem in conventional communication with rural areas is the fact that radio signals travel in line of sight. They may be blocked by tall buildings, hills and mountains, or even by the curvature of the Earth, so signal range is sharply limited. Microwave relay towers could solve the problem, but a complete network of repeater towers would be extremely expensive. The satellite provides an obstruction-free relay station in space.

  1. 自适应遗传算法的数据中继卫星光网络资源调度算法%Scheduling algorithm for data relay satellite optical network based on self-adaptive genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    赵卫虎; 赵静; 赵尚弘; 李勇军; 董毅; 李轩

    2015-01-01

    According to the resources, missions and restraints of the data relay satellite optical network, a scheduling algorithm based on improved self-adaptive genetic algorithm was put forwarded. Considering the multi-relay satellite, multi-window, multi-optical-antenna and multi-mission PRI, the model was established. The missions were scheduled by the scheduling operates: the ascertainment of current mission scheduling time and the refreshment of latter mission time-window. The whole weight of the scheduled missions was set as the cost value and the scheduling schemes were optimized by the self-adaptive genetic algorithm. The simulation scene including 3 relay satellites, 12 user satellites, 6 antennas and 60 missions, the result reveals that the algorithm obtains satisfactory results in both time and optimization which is suitable in multi-user, multi-mission and multi-optical-antenna recourse scheduling.%以数据中继卫星光网络系统资源、任务和约束条件为参量,以任务对资源的选择为优化对象,提出了一种基于自适应遗传算法的数据中继卫星光网络资源调度算法。综合考虑多中继星、多时间窗口、多光学天线以及任务优先级要求,建立调度模型;采用“当前任务调度时间的确定”和“后续任务可见时间窗口的更新”的调度操作,对不同资源的任务集合进行调度安排并实现了可见时间窗口的动态更新,获得调度任务的总权值并将其作为参量计算适应度值,最后通过改进的自适应遗传算法对不同调度方案进行寻优。以3颗中继星、12颗用户星,6个光天线,60个任务为条件设置了仿真场景,仿真结果表明该算法在收敛速度、调度效率方面具有优势,适应于多任务、多天线的数据中继卫星光网络系统资源调度。

  2. SAW based systems for mobile communications satellites

    Science.gov (United States)

    Peach, R. C.; Miller, N.; Lee, M.

    1993-01-01

    Modern mobile communications satellites, such as INMARSAT 3, EMS, and ARTEMIS, use advanced onboard processing to make efficient use of the available L-band spectrum. In all of these cases, high performance surface acoustic wave (SAW) devices are used. SAW filters can provide high selectivity (100-200 kHz transition widths), combined with flat amplitude and linear phase characteristics; their simple construction and radiation hardness also makes them especially suitable for space applications. An overview of the architectures used in the above systems, describing the technologies employed, and the use of bandwidth switchable SAW filtering (BSSF) is given. The tradeoffs to be considered when specifying a SAW based system are analyzed, using both theoretical and experimental data. Empirical rules for estimating SAW filter performance are given. Achievable performance is illustrated using data from the INMARSAT 3 engineering model (EM) processors.

  3. Global Ocean Surveillance With Electronic Intelligence Based Satellite System

    Science.gov (United States)

    Venkatramanan, Haritha

    2016-07-01

    The objective of this proposal is to design our own ELINT based satellite system to detect and locate the target by using satellite Trilateration Principle. The target position can be found by measuring the radio signals arrived at three satellites using Time Difference of Arrival(TDOA) technique. To locate a target it is necessary to determine the satellite position. The satellite motion and its position is obtained by using Simplified General Perturbation Model(SGP4) in MATLAB. This SGP4 accepts satellite Two Line Element(TLE) data and returns the position in the form of state vectors. These state vectors are then converted into observable parameters and then propagated in space. This calculations can be done for satellite constellation and non - visibility periods can be calculated. Satellite Trilateration consists of three satellites flying in formation with each other. The satellite constellation design consists of three satellites with an inclination of 61.3° maintained at equal distances between each other. The design is performed using MATLAB and simulated to obtain the necessary results. The target's position can be obtained using the three satellites ECEF Coordinate system and its position and velocity can be calculated in terms of Latitude and Longitude. The target's motion is simulated to obtain the Speed and Direction of Travel.

  4. A General Robust Linear Transceiver Design for Multi-Hop Amplify-and-Forward MIMO Relaying Systems

    Science.gov (United States)

    Xing, Chengwen; Ma, Shaodan; Fei, Zesong; Wu, Yik-Chung; Poor, H. Vincent

    2013-03-01

    In this paper, linear transceiver design for multi-hop amplify-and-forward (AF) multiple-input multiple-out (MIMO) relaying systems with Gaussian distributed channel estimation errors is investigated. Commonly used transceiver design criteria including weighted mean-square-error (MSE) minimization, capacity maximization, worst-MSE/MAX-MSE minimization and weighted sum-rate maximization, are considered and unified into a single matrix-variate optimization problem. A general robust design algorithm is proposed to solve the unified problem. Specifically, by exploiting majorization theory and properties of matrix-variate functions, the optimal structure of the robust transceiver is derived when either the covariance matrix of channel estimation errors seen from the transmitter side or the corresponding covariance matrix seen from the receiver side is proportional to an identity matrix. Based on the optimal structure, the original transceiver design problems are reduced to much simpler problems with only scalar variables whose solutions are readily obtained by iterative water-filling algorithm. A number of existing transceiver design algorithms are found to be special cases of the proposed solution. The differences between our work and the existing related work are also discussed in detail. The performance advantages of the proposed robust designs are demonstrated by simulation results.

  5. Role of Ocrl1 and Inpp5E in primary cilia assembly and maintenance: a phosphatidylinositol phosphatase relay system?

    Directory of Open Access Journals (Sweden)

    Madhivanan K

    2016-02-01

    Full Text Available Kayalvizhi Madhivanan,* Swetha Ramadesikan,* R Claudio Aguilar Department of Biological Sciences, Purdue University, West Lafayette, IN, USA *These authors contributed equally to this work Abstract: The primary cilium (PC is a plasma membrane-derived structure of great importance for cell and organismal physiology. Indeed, abnormalities in assembly or function of the PC trigger the onset of a group of genetic diseases collectively known as ciliopathies. In recent years, it has become evident that the integrity and function of the PC depends substantially on signaling elements such as phosphoinositides (PI and their regulators. Because phospholipids such as PI(4,5P2 constitute recruitment platforms for cytoskeleton, signaling, and trafficking machinery, control over their levels is critical for PC function. Although information about phosphoinositol phosphate (PIP kinases in the PC is scarce, a growing body of evidence supports a role for PIP phosphatases in cilia assembly/maintenance. Indeed, deficiencies in two 5′ PIP phosphatases, Inpp5E and Ocrl1, are clearly linked to ciliopathies like Joubert/MORM syndromes, or ciliopathy-associated diseases like Lowe syndrome. Here, we review the unique roles of these proteins and their specific site of action for ensuring ciliary integrity. Further, we discuss the possibility that a phosphatase relay system able to pass PI control from a preciliary to an intraciliary compartment is in place to ensure PC integrity/function. Keywords: primary cilia, Ocrl1, Inpp5E, Pip2, Pip3

  6. Performance Analysis of Dual-hop MIMO Relay Systems with MRT&RAS in the Presence of Co-channel Interference

    Science.gov (United States)

    Xu, Xiaoming; Cai, Yueming; Yang, Weiwei

    2013-09-01

    This paper focuses on the downlink dual-hop multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay systems that employ the maximal-ratio transmission and receive antenna selection scheme (MRT&RAS) for use in each hop. The system under consideration is equipped with arbitrary NS, NR, and ND antennas at the base station (BS), relay station (RS), and mobile station (MS), respectively. The system performance has been investigated over Nakagami-m fading in presence of independent but not necessarily identically distributed co-channel interferences (CCIs) at both the RS and MS. First, we derive an accurate closed-form approximate expression for the outage probability and a single-integral expression for the average symbol error rate (SER), respectively. Besides, to render direct insights into the combined effect of multiple-antenna and interference on the system performance, the asymptotic expressions for the outage probability and the average SER are also presented. Furthermore, we determine the optimal power allocation (OPA) by using the exact and asymptotic methods, respectively, such that the outage probability is minimized. Finally, numerical results validate the correctness of the derived expressions and show that OPA offers superior performance over uniform power allocation. Our analysis and results provide insights on investigating and optimizing the performance of the downlink MIMO relay transmission in practical interference-limited wireless networks.

  7. Cross-layer combining of information-guided transmission withnetwork coding relaying for multiuser cognitive radio systems

    KAUST Repository

    Yang, Yuli

    2013-02-01

    For a cognitive radio relaying network, we propose a cross-layer design by combining information-guided transmission at the physical layer and network coding at the network layer. With this design, a common relay is exploited to help the communications between multiple secondary source-destination pairs, which allows for a more efficient use of the radio resources, and moreover, generates less interference to primary licensees in the network. Considering the spectrum-sharing constraints on the relay and secondary sources, the achievable data rate of the proposed cross-layer design is derived and evaluated. Numerical results on average capacity and uniform capacity in the network under study substantiate the efficiency of our proposed design. © 2013 IEEE.

  8. Reactive relay selection in underlay cognitive networks with fixed gain relays

    KAUST Repository

    Hussain, Syed Imtiaz

    2012-06-01

    Best relay selection is a bandwidth efficient technique for multiple relay environments without compromising the system performance. The problem of relay selection is more challenging in underlay cognitive networks due to strict interference constraints to the primary users. Generally, relay selection is done on the basis of maximum end-to-end signal to noise ratio (SNR). However, it requires large amounts of channel state information (CSI) at different network nodes. In this paper, we present and analyze a reactive relay selection scheme in underlay cognitive networks where the relays are operating with fixed gains near a primary user. The system model minimizes the amount of CSI required at different nodes and the destination selects the best relay on the basis of maximum relay to destination SNR. We derive close form expressions for the received SNR statistics, outage probability, bit error probability and average channel capacity of the system. Simulation results are also presented to confirm the validity of the derived expressions. © 2012 IEEE.

  9. Communication satellite system beyond the year 2000

    Science.gov (United States)

    Robertson, G. J.; Fourquet, J. M.

    1991-10-01

    The primary evolutionary factors of satellite communications technologies are reviewed based on the results of a study of novel satellite developments. A critical evaluation of the viability and availability of the technologies is utilized in conjunction with market forecasts to determine promising commercial strategies. Modern technologies are almost prepared for the development of a class of communications satellites and include bandwidth utilization, spacecraft bus modularity, and functional integration.

  10. 基于Simulink仿真的用户星天线控制系统分析%Analysis of Simulink-based antenna control system on user satellite

    Institute of Scientific and Technical Information of China (English)

    龙甲禄; 闫剑虹

    2012-01-01

    To meet the need of the antenna pointing accuracy of data relay satellite system, the antenna pointing control concept is described, and the establishment process of the link between the user satellite and data relay satellite is analyzed. A scheme for satelite-borne autonomous control is designed, A mathematic simulation of the antenna pointing control system is conducted under the Simulink circumstance. The tracking performance of the antenna control system on the user satellite is verified by the analysis of the simulation results.%为满足中继卫星系统对天线指向精度的要求,首先描述了天线指向控制概念,对用户星与中继卫星星间链路的建立过程进行了分析,并且设计了星上自主控制方案,在Simulink环境下对所设计的天线指向控制系统进行了数学仿真,最后通过对仿真结果的分析验证了用户星天线控制系统的跟踪性能.

  11. Simultaneous single epoch satellite clock modelling in Global Navigation Satellite Systems

    Science.gov (United States)

    Thongtan, Thayathip

    In order to obtain high quality positions from navigation satellites, range errors have to be identified and either modelled or estimated. This thesis focuses on satellite clock errors, which are needed to be known because satellite clocks are not perfectly synchronised with navigation system time. A new approach, invented at UCL, for the simultaneous estimation, in a single epoch, of all satellite clock offsets within a Global Navigation Satellite System (GNSS) from range data collected at a large number of globally distributed ground stations is presented. The method was originally tested using only data from a limited number of GPS satellites and ground stations. In this work a total of 50 globally distributed stations and the whole GPS constellation are used in order to investigate more fully the capabilities of the method, in terms of both accuracy and reliability. A number of different estimation models have been tested. These include those with different weighting schemes, those with and without tropospheric bias parameters and those that include assumptions regarding prior knowledge of satellite orbits. In all cases conclusions have been drawn based on formal error propagation theory. Accuracy has been assessed largely through the sizes of the predicted satellite clock standard deviations and, in the case of simultaneously estimating satellite positions, their error ellipsoids. Both internal and external reliability have been assessed as these are important contributors to integrity, something that is essential for many practical applications. It has been found that the accuracy and reliability of satellite clock offsets are functions of the number of known ground station clocks and distance from them, quality of orbits and quality of range measurement. Also the introduction of tropospheric zenith delay parameters into the model reduces both accuracy and reliability by amounts depending on satellite elevation angles. (Abstract shortened by UMI.)

  12. Relay Architectures for 3GPP LTE-Advanced

    Directory of Open Access Journals (Sweden)

    Peters StevenW

    2009-01-01

    Full Text Available The Third Generation Partnership Project's Long Term Evolution-Advanced is considering relaying for cost-effective throughput enhancement and coverage extension. While analog repeaters have been used to enhance coverage in commercial cellular networks, the use of more sophisticated fixed relays is relatively new. The main challenge faced by relay deployments in cellular systems is overcoming the extra interference added by the presence of relays. Most prior work on relaying does not consider interference, however. This paper analyzes the performance of several emerging half-duplex relay strategies in interference-limited cellular systems: one-way, two-way, and shared relays. The performance of each strategy as a function of location, sectoring, and frequency reuse are compared with localized base station coordination. One-way relaying is shown to provide modest gains over single-hop cellular networks in some regimes. Shared relaying is shown to approach the gains of local base station coordination at reduced complexity, while two-way relaying further reduces complexity but only works well when the relay is close to the handset. Frequency reuse of one, where each sector uses the same spectrum, is shown to have the highest network throughput. Simulations with realistic channel models provide performance comparisons that reveal the importance of interference mitigation in multihop cellular networks.

  13. Robust Satellite Communications Under Hostile Interference

    Science.gov (United States)

    2015-01-08

    Gaussian Noise BER Bit Error Rate BLER Block Error Rate BPSK Binary Phase Shift Keying CODEC Coder and Decoder CRC Cyclic Redundancy Check dB...Satellite Communication SNR Signal to Noise Ratio STK Systems Took Kit TDRS Tracking and Data Relay Satellite Toff Idle Time of a Transmitter Ton...Received Signal-to- Noise Ratio at the Jammer ...................................................... 15  3.2.2  SNR Threshold for Repeating the Signal

  14. Coordinated Direct and Relay Transmission with Linear Non-Regenerative Relay Beamforming

    DEFF Research Database (Denmark)

    Sun, Fan; De Carvalho, Elisabeth; Popovski, Petar;

    2012-01-01

    Joint processing of multiple communication flows in wireless systems has given rise to a number of novel transmission techniques, notably the two-way relaying, but also more general traffic scenarios, such as coordinated direct and relay (CDR) transmissions. In a CDR scheme the relay has a central...... role in managing the interference and boosting the overall system performance. In this letter we consider the case in which an amplify-and-forward relay has multiple antennas and can use beamforming to support the coordinated transmissions. We focus on one representative traffic type with one uplink...... user and one downlink user. Two different criteria for relay beamforming are analyzed: maximal weighted sum-rate and maximization of the worst-case weighted SNR. We propose iterative optimal solutions, as well as low-complexity near-optimal solutions....

  15. Global navigation satellite system; Jisedai kokoho senjo system

    Energy Technology Data Exchange (ETDEWEB)

    Kawano, S.; Suga, S. [Toshiba Corp., Tokyo (Japan)

    2000-05-01

    The safety of civil aviation relies on ground navigation aids. In areas where there are no ground aids and on oceanic air routes, aircraft must depend on their own navigation system. The predicted increase in civil aviation traffic in the near future will make it difficult for current navigation aids to support navigation in all phases of flights. To avoid this problem, the International Civil Aviation Organization (ICAO) is directing the establishment of standards for the global navigation satellite system (GNSS). GNSS employs navigation satellites, such as those of the global positioning system (GPS), to provide navigation capability throughout the world. In Japan, the Electronic Navigation Research Institute, the Ministry of Transport, and the Japan civil Aviation Promotion Foundation are carrying out research on this navigation system. Toshiba has been providing experimental equipment for this research. (author)

  16. Satellite data assimilation in global forecast system in India

    Science.gov (United States)

    Basu, Swati

    2014-11-01

    Satellite data is very important for model initialization and verification. A large number of satellite observations are currently assimilated into the Numerical Weather Prediction (NWP) systems at the National Centre for Medium Range Weather Forecasting (NCMRWF). Apart from Global meteorological observations from GTS, near-real time satellite observations are received at NCMRWF from other operational centres like ISRO, NOAA/NESDIS, EUMETCAST, etc. Recently India has become member of Asia-Pacific Regional ATOVS Retransmission Service (APRARS) for faster access to high resolution global satellite data useful for high resolution regional models. Indian HRPT at Chennai covers the APRARS data gap region over South East Asia. A robust data monitoring system has been implemented at NCMRWF to assess the quantity and quality of the data as well as the satellite sensor strength, before getting assimilated in the models. Validation of new satellite observations, especially from Indian satellites are being carried out against insitu observations and similar space borne platforms. After establishing the quality of the data, Observation System Experiments (OSEs) are being conducted to study their impact in the assimilation and forecast systems. OSEs have been carried out with the Oceansat-2 scatterometer winds and radiance data from Megha-Tropiques SAPHIR sensor. Daily rainfall analysis dataset is being generated by merging satellite estimates and in-situ observations. ASCAT soil wetness measurements from METOP satellite is being assimilated into the global model. Land surface parameters (LuLc and albedo) retrieved from Indian satellites are being explored for its possible usage in the global and regional models. OLR from Indian satellites are used for validating model outputs. This paper reviews the efforts made at NCMRWF in (i) assimilating the data from Indian/International satellites and (ii) generating useful products from the satellite data.

  17. GNSS global navigation satellite systems : GPS, GLONASS, Galileo, and more

    CERN Document Server

    Hofmann-Wellenhof, Bernhard; Wasle, Elmar

    2008-01-01

    This book is an extension to the acclaimed scientific bestseller "GPS - Theory and Practice". It covers Global Navigation Satellite Systems (GNSS) and includes the Russian GLONASS, the European system Galileo, and additional systems.

  18. Cooperative Jamming for Secure Communications in MIMO Relay Networks

    CERN Document Server

    Huang, Jing

    2011-01-01

    Secure communications can be impeded by eavesdroppers in conventional relay systems. This paper proposes cooperative jamming strategies for two-hop relay networks where the eavesdropper can wiretap the relay channels in both hops. In these approaches, the normally inactive nodes in the relay network can be used as cooperative jamming sources to confuse the eavesdropper. Linear precoding schemes are investigated for two scenarios where single or multiple data streams are transmitted via a decode-and-forward (DF) relay, under the assumption that global channel state information (CSI) is available. For the case of single data stream transmission, we derive closed-form jamming beamformers and the corresponding optimal power allocation. Generalized singular value decomposition (GSVD)-based secure relaying schemes are proposed for the transmission of multiple data streams. The optimal power allocation is found for the GSVD relaying scheme via geometric programming. Based on this result, a GSVD-based cooperative jam...

  19. CERN Relay Race

    CERN Multimedia

    2008-01-01

    The CERN relay race will take place around the Meyrin site on Thursday 5 June starting at 12:15 p.m. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on how to register your team for the relay race are given on the Staff Association Bulletin web site. You can access the online registration form at: http://cern.ch/club-running-relay/form.html

  20. CERN Relay Race

    CERN Multimedia

    2007-01-01

    The CERN relay race will take place around the Meyrin site on Wednesday 23 May starting at 12:15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on how to register your team for the relay race are given on the Staff Association Bulletin web site. You can access the online registration form at: http://cern.ch/club-running-relay/form.html

  1. Performance Analysis of MIMO Relay Systems over Nakagami-m Fading%Nakagami-m衰落MIMO中继系统性能分析

    Institute of Scientific and Technical Information of China (English)

    张攀索; 李光平; 刘东峰

    2012-01-01

    This paper researches that the source and destination are equipped with multiple antennas, the relay only has a two-hop relay system with a single antenna. Quasi-orthogonal Space-Time Block Code(OSTBC) and MRC are employed at source, and destination, respectively, to achieve spatial diversity. To reduce the implementation complexity of the relay, the fixed-gain amplify-to-forward relay protocol is used. New exact expressions for outage probability and average bit error rate are derived in Nakagami-m fading environments. Numerical comparison results between Monte Carlo simulations show the accuracy of the theoretical expressions.%研究固定增益放大转发协议,信源和终端需要配置多根天线,而中继只有单根天线的两跳中继转发系统.为获得空间分集,信源利用正交空时分组编码的发射策略,终端利用选择合并方式,简化中继配置的复杂度,采用固定增益放大转发的协议.导出Nakagami-m衰落下系统终端概率的封闭表达式与平均误比特率的封闭表达式,通过蒙特卡罗仿真和数值结果比较,验证了封闭表达式的精确性.

  2. Computer-Aided Communication Satellite System Analysis and Optimization.

    Science.gov (United States)

    Stagl, Thomas W.; And Others

    Various published computer programs for fixed/broadcast communication satellite system synthesis and optimization are discussed. The rationale for selecting General Dynamics/Convair's Satellite Telecommunication Analysis and Modeling Program (STAMP) in modified form to aid in the system costing and sensitivity analysis work in the Program on…

  3. An Instructional Satellite System for the United States: Preliminary Considerations.

    Science.gov (United States)

    DuMolin, James R.; Morgan, Robert P.

    Based on educational, social, political, and other considerations, an instructional satellite system, AVSIN (Ausio-Visual Satellite Instruction), is hypothesized which represents one possible organizational and administrative arrangement for delivering large amounts of quality software to schools and learning centers. The AVSIN system is conceived…

  4. Power Processing Unit For Micro Satellite Electric Propulsion System

    Directory of Open Access Journals (Sweden)

    Savvas Spiridon

    2017-01-01

    Full Text Available The Micro Satellite Electric Propulsion System (MEPS program has been originated by the increasing need to provide a low-cost and low-power Electric Propulsion System (EPS for small satellites ( 92%, small size and weight and high reliability. Its functional modules and preliminary results obtained at breadboard level are also presented.

  5. Preliminary Assessment/Site Inspection Work Plan for Granite Mountain Radio Relay System

    Science.gov (United States)

    1994-09-01

    Installation Restoration Program IRPIMS Installation Restoration Program Information Management System Jacobs Jacobs Engineering Group Inc. mg ...station; * water supply building; * two 30-foot high disk antennas; * four 60-foot high tropospheric antennas; * two fuel oil storage tanks; and...a predominant surface feature around the peak of Granite Mountain. This pluton is surrounded by an andesitic volcanic unit of early Cretaceous age

  6. Evaluation of CDMA system capacity for mobile satellite system applications

    Science.gov (United States)

    Smith, Partrick O.; Geraniotis, Evaggelos A.

    1988-01-01

    A specific Direct-Sequence/Pseudo-Noise (DS/PN) Code-Division Multiple-Access (CDMA) mobile satellite system (MSAT) architecture is discussed. The performance of this system is evaluated in terms of the maximum number of active MSAT subscribers that can be supported at a given uncoded bit-error probability. The evaluation decouples the analysis of the multiple-access capability (i.e., the number of instantaneous user signals) from the analysis of the multiple-access mutliplier effect allowed by the use of CDMA with burst-modem operation. We combine the results of these two analyses and present numerical results for scenarios of interest to the mobile satellite system community.

  7. Double-Directional Information Azimuth Spectrum and Relay Network Tomography for a Decentralized Wireless Relay Network

    CERN Document Server

    Chen, Yifan

    2010-01-01

    A novel channel representation for a two-hop decentralized wireless relay network (DWRN) is proposed, where the relays operate in a completely distributive fashion. The modeling paradigm applies an analogous approach to the description method for a double-directional multipath propagation channel, and takes into account the finite system spatial resolution and the extended relay listening/transmitting time. Specifically, the double-directional information azimuth spectrum (IAS) is formulated to provide a compact representation of information flows in a DWRN. The proposed channel representation is then analyzed from a geometrically-based statistical modeling perspective. Finally, we look into the problem of relay network tomography (RNT), which solves an inverse problem to infer the internal structure of a DWRN by using the instantaneous doubledirectional IAS recorded at multiple measuring nodes exterior to the relay region.

  8. System refinement for content based satellite image retrieval

    Directory of Open Access Journals (Sweden)

    NourElDin Laban

    2012-06-01

    Full Text Available We are witnessing a large increase in satellite generated data especially in the form of images. Hence intelligent processing of the huge amount of data received by dozens of earth observing satellites, with specific satellite image oriented approaches, presents itself as a pressing need. Content based satellite image retrieval (CBSIR approaches have mainly been driven so far by approaches dealing with traditional images. In this paper we introduce a novel approach that refines image retrieval process using the unique properties to satellite images. Our approach uses a Query by polygon (QBP paradigm for the content of interest instead of using the more conventional rectangular query by image approach. First, we extract features from the satellite images using multiple tiling sizes. Accordingly the system uses these multilevel features within a multilevel retrieval system that refines the retrieval process. Our multilevel refinement approach has been experimentally validated against the conventional one yielding enhanced precision and recall rates.

  9. Development of environmental monitoring satellite systems in China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    With the increase in global environmental problems,the necessity and urgency of remote sensing technology being applied to environmental monitoring has been widely recognized around the world.China has launched the environment and disaster monitoring and forecasting small satellite constellation HJ-1A/B and the FY3 atmosphere and environmental satellite,but they still cannot fully satisfy requirements for environmental monitoring.This paper summarizes the current status of satellite environmental monitoring in China and the existing problems of inadequate load design and low data utilization efficiency,and discusses the demand for environmental monitoring satellites.Based on the development of foreign satellite systems for environmental monitoring,the future development and key tasks of the environmental monitoring satellite system in China is discussed,as are some related initiatives.

  10. Shipboard Radio Frequency and Free Space Optics Communications System using an Airborne Relay

    Science.gov (United States)

    2005-09-01

    gain for FSO systems has the potential to be several orders of magnitude greater than RF gain by virtue of the 21λ factor. An optical antenna with... optical antenna , in this case, has a 40 dB advantage, ten-thousand times the gain, despite its smaller dimensions. 1. Transmit Gain A parabolic...3rd Edition. 2001. [19] Klein, B. J., and Degnan, J. J. “ Optical Antenna Gain. 1: Transmitting Antennas.” Applied Optics, Vol. 13, No. 9

  11. Capture Scheme of the Antenna in Ka-band for Launch Vehicle Based on Tracking and Data Relay Satellite%运载火箭Ka频段天基测控的天线捕获方法

    Institute of Scientific and Technical Information of China (English)

    宫长辉; 曾贵明; 张恒

    2011-01-01

    In order to transmit the space-based signal, the capture and track between the tracking and data relay satellite(TDRS) antenna and the user's aerocraft antenna should be completed firstly. In this paper, the uncertain area of the antenna scan is analyzed, adopting antenna-scan capture scheme for capturing the antenna on TORS by the phased-array antenna on launch vehicle. The values of the antenna array and EIRP are conformed and the capture time is given by computer simulation.%为实现天基信息的传输,首先要完成中继卫星天线与用户飞行器天线之间的捕获与跟踪.针对箭载相控阵天线对中继卫星的捕获,采用Ka频段相控阵天线扫描捕获策略,分析了天线扫描的不确定区域,确定了天线阵元数及EIRP值,给出了捕获时间的仿真结果,为工程应用提供参考.

  12. Reusable Reentry Satellite (RRS) system design study

    Science.gov (United States)

    1991-01-01

    The Reusable Reentry Satellite (RRS) is intended to provide investigators in several biological disciplines with a relatively inexpensive method to access space for up to 60 days with eventual recovery on Earth. The RRS will permit totally intact, relatively soft, recovery of the vehicle, system refurbishment, and reflight with new and varied payloads. The RRS is to be capable of three reflights per year over a 10-year program lifetime. The RRS vehicle will have a large and readily accessible volume near the vehicle center of gravity for the Payload Module (PM) containing the experiment hardware. The vehicle is configured to permit the experimenter late access to the PM prior to launch and rapid access following recovery. The RRS will operate in one of two modes: (1) as a free-flying spacecraft in orbit, and will be allowed to drift in attitude to provide an acceleration environment of less than 10(exp -5) g. the acceleration environment during orbital trim maneuvers will be less than 10(exp -3) g; and (2) as an artificial gravity system which spins at controlled rates to provide an artificial gravity of up to 1.5 Earth g. The RRS system will be designed to be rugged, easily maintained, and economically refurbishable for the next flight. Some systems may be designed to be replaced rather than refurbished, if cost effective and capable of meeting the specified turnaround time. The minimum time between recovery and reflight will be approximately 60 days. The PMs will be designed to be relatively autonomous, with experiments that require few commands and limited telemetry. Mass data storage will be accommodated in the PM. The hardware development and implementation phase is currently expected to start in 1991 with a first launch in late 1993.

  13. Ready, steady… relay!

    CERN Multimedia

    2008-01-01

    Thursday 5 June. With another year comes another success for CERN’s Relay Race. With 76 teams taking part it was the second highest turnout in the race’s history. ‘The Shabbys’ won the relay race in 10 minutes 51 seconds.As popular as ever, this year the relay race took on the atmosphere of a mini carnival. Gathering on the lawn outside Restaurant 1, various stalls and attractions added to the party feeling of the event, with beer courtesy of ‘AGLUP’, the Belgian beer club, and a wandering jazz group entertaining spectators and competitors alike. Reflecting the greater involvement of other associations in the relay race, the president of the Staff Association Clubs Committee, James Purvis, was the guest of honour, launching the start of the race and presenting the prizes. As regular followers of the race could have probably predicted, The Shabbys were once again victorious and claimed first place. The team members th...

  14. Multi-flow scheduling for coordinated direct and relayed users in cellular systems

    DEFF Research Database (Denmark)

    Thai, Chan; Popovski, Petar; Kaneko, Megumi

    2013-01-01

    domain and they need to be assigned a communication resource simultaneously. In this paper we define a novel framework that can be used to analyze MFT schemes and assess the system-level gains. The framework is based on cellular wireless users with two-way traffic and it sets the basis for devising...... composite time-multiplexed MFT schemes, tailored to particular optimization criteria. Those criteria can be formulated by adapting well-known schedulers in order to incorporate MFT schemes. The results show rate advantages brought by the CDR schemes in pertinent scenarios. Another key contribution...

  15. DESIGN THREE PHASE OVERCURRENT RELAYS

    Directory of Open Access Journals (Sweden)

    Mohammed Y Suliman,

    2013-05-01

    Full Text Available  A new design of three phase overcurrent relay described in this paper. The performance of the new design shows the ability to obtain any shape of characteristic with high accuracy and distinguish between transient and steady state fault. This design used more precise and flexible model Sachdev linear model for get any characteristic, also fast measurement theory to measure load current for less than half cycle and good hardware system design controlled by Pentium version 4 processor.

  16. Space Solar Power Satellite Systems, Modern Small Satellites, and Space Rectenna

    Science.gov (United States)

    Bergsrud, Corey Alexis Marvin

    Space solar power satellite (SSPS) systems is the concept of placing large satellite into geostationary Earth orbit (GEO) to harvest and convert massive amounts of solar energy into microwave energy, and to transmit the microwaves to a rectifying antenna (rectenna) array on Earth. The rectenna array captures and converts the microwave power into usable power that is injected into the terrestrial electric grid for use. This work approached the microwave power beam as an additional source of power (with solar) for lower orbiting satellites. Assuming the concept of retrodirectivity, a GEO-SSPS antenna array system tracks and delivers microwave power to lower orbiting satellites. The lower orbiting satellites are equipped with a stacked photovoltaic (PV)/rectenna array hybrid power generation unit (HPGU) in order to harvest solar and/or microwave energy for on-board use during orbit. The area, and mass of the PV array part of the HPGU was reduced at about 32% beginning-of-life power in order to achieve the spacecraft power requirements. The HPGU proved to offer a mass decrease in the PGU, and an increase in mission life due to longer living component life of the rectenna array. Moreover, greater mission flexibility is achieved through a track and power delivery concept. To validate the potential advantages offered by a HPGU, a mission concept was presented that utilizes modern small satellites as technology demonstrators. During launch, a smaller power receiving "daughter" satellite sits inside a larger power transmitting "mother" satellite. Once separated from the launch vehicle the daughter satellite is ejected away from the mother satellite, and each satellite deploys its respective power transmitting or power receiving hardware's for experimentation. The concept of close proximity mission operations between the satellites is considered. To validate the technology of the space rectenna array part of the HPGU, six milestones were completed in the design. The first

  17. CERN Relay Race 2009

    CERN Multimedia

    2009-01-01

    The CERN relay race will take place around the Meyrin site on Thursday 14th May starting at 12:15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. More details on how to register your team for the relay race

  18. Study on fault locating technology for satellite power system

    Institute of Scientific and Technical Information of China (English)

    LONG Bing; JIANG Xing-wei; SONG Zheng-ji

    2005-01-01

    It is currently prevalent to locate faults for a satellite power system based on an expert system, not utilizing all the available information provided by tests. The casual network model for a satellite power system is presented. Considerations for failure probability of each component of the power system, the cost of applying each test, the influence of a precedent test result on the next test selection, and an optimal sequential testing algorithm for fault location is presented. This program is applied to locate the failure component of the power system of a satellite. The results show this program is very effective and it is very fast to generate an optimal diagnosis tree.

  19. Joint Relay Selection and Power Allocation for Cooperative Communication over Frequency Selective Fading Channels

    Directory of Open Access Journals (Sweden)

    Youhua Ma

    2012-08-01

    Full Text Available In this paper, we consider the joint problem of relay selection and optimal power allocation for multi-relay amplify-and-forward (AF cooperative communication system over frequency selective fading channels. An optimization model combined relay selection and power allocation under a total transmission power budget is formulated. Then, this combinatorial problem is solved in a distributed strategy. Relay selection with a new threshold-based multiple-relay selection (MRS scheme is implemented at first, and then power is allocated between source and the selected relays in an optimized way to maximize channel capacity. Simulation result shows that the proposed joint scenario with relay selection and power allocation achieves better throughput performance than that of parallel-relay scenario (means that random relay is selected to forward data and allocated part of total power on average. Furthermore, the performances of the new MRS scheme and other relay selection strategies are also investigated.

  20. Quantum relay schemes for continuous-variable quantum key distribution

    Science.gov (United States)

    Guo, Ying; Liao, Qin; Huang, Duan; Zeng, Guihua

    2017-04-01

    We propose several concatenated quantum relay continuous-variable quantum key distribution schemes based on the parametric amplifier (PA) and the beam splitter (BS). Instead of using only one BS in the traditional relay scheme, the proposed schemes provide two operations that involve both PA and BS, activating the beam splitting and recombining operations in turn. These schemes would benefit the system performance improvement by providing signal amplification and establishing quantum correlations. We show that the different effects of the relay schemes will cause different system performances because of the varied signal-to-noise ratio (SNR) of output fields. The system's secret key rate will be increased when equipping with the PA-BS relay scheme, because the output fields of the PA are entangled with the correlated quantum noises while input fields of the BS are superimposed, subsequently leading to the quantum noise reduction of the total output fields of relay station, while the reversed BS-PA relay scheme has little advantage over the traditional counterpart that contains only one BS in relay data postprocessing because it will not cause any SNR improvement. Moreover, the reinforced PA-PA relay scheme results in a slight improvement due to the increased SNR. These quantum relay schemes can be performed through the beam splitting, the recombining operations, and the relay data postprocessing, such that it would be suitable for secret information exchange in complex networks with intermediate stations.

  1. Developing a Domain Model for Relay Circuits

    DEFF Research Database (Denmark)

    Haxthausen, Anne Elisabeth

    2009-01-01

    the statics as well as the dynamics of relay circuits, i.e. how a relay circuit can be composed legally from electrical components as well as how the components may change state over time. Finally the circuit model is transformed into an executable model, and we show how a concrete circuit can be defined......In this paper we stepwise develop a domain model for relay circuits as used in railway control systems. First we provide an abstract, property-oriented model of networks consisting of components that can be glued together with connectors. This model is strongly inspired by a network model...... for railways madeby Bjørner et.al., however our model is more general: the components can be of any kind and can later be refined to e.g. railway components or circuit components. Then we show how the abstract network model can be refined into an explicit model for relay circuits. The circuit model describes...

  2. LTE-Advanced Relay Technology and Standardization

    CERN Document Server

    Yuan, Yifei

    2013-01-01

    LTE-Advanced Relay Technology and Standardization provides a timely reference work for relay technology with the finalizing of LTE Release 10 specifications. LTE-Advanced is quickly becoming the global standard for 4G cellular communications. The relay technology, as one of the key features in LTE-Advanced, helps not only to improve the system coverage and capacity, but also to save the costs of laying wireline backhaul. As a leading researcher in the field of LTE-Advanced standards, the author provides an in-depth description of LTE-A relay technology, and explains in detail the standard specification and design principles.     Readers from both academic and industrial fields can find sections of interest to them: Sections 2 & 4 could benefit researchers in academia and those who are engaged in exploratory work, while Sections 3 & 4 are more useful to engineers. Dr. Yifei Yuan is the Technical Director at the Standards Department of ZTE Inc.

  3. Opportunistic relaying in multipath and slow fading channel: Relay selection and optimal relay selection period

    KAUST Repository

    Sungjoon Park,

    2011-11-01

    In this paper we present opportunistic relay communication strategies of decode and forward relaying. The channel that we are considering includes pathloss, shadowing, and fast fading effects. We find a simple outage probability formula for opportunistic relaying in the channel, and validate the results by comparing it with the exact outage probability. Also, we suggest a new relay selection algorithm that incorporates shadowing. We consider a protocol of broadcasting the channel gain of the previously selected relay. This saves resources in slow fading channel by reducing collisions in relay selection. We further investigate the optimal relay selection period to maximize the throughput while avoiding selection overhead. © 2011 IEEE.

  4. The satellite based augmentation system – EGNOS for non-precision approach global navigation satellite system

    Directory of Open Access Journals (Sweden)

    Andrzej FELLNER

    2012-01-01

    Full Text Available First in the Poland tests of the EGNOS SIS (Signal in Space were conducted on 5th October 2007 on the flight inspection with SPAN (The Synchronized Position Attitude Navigation technology at the Mielec airfield. This was an introduction to a test campaign of the EGNOS-based satellite navigation system for air traffic. The advanced studies will be performed within the framework of the EGNOS-APV project in 2011. The implementation of the EGNOS system to APV-I precision approach operations, is conducted according to ICAO requirements in Annex 10. Definition of usefulness and certification of EGNOS as SBAS (Satellite Based Augmentation System in aviation requires thorough analyses of accuracy, integrity, continuity and availability of SIS. Also, the project will try to exploit the excellent accuracy performance of EGNOS to analyze the implementation of GLS (GNSS Landing System approaches (Cat I-like approached using SBAS, with a decision height of 200 ft. Location of the EGNOS monitoring station Rzeszów, located near Polish-Ukrainian border, being also at the east border of planned EGNOS coverage for ECAC states is very useful for SIS tests in this area. According to current EGNOS programmed schedule, the project activities will be carried out with EGNOS system v2.2, which is the version released for civil aviation certification. Therefore, the project will allow demonstrating the feasibility of the EGNOS certifiable version for civil applications.

  5. Integration Of GPS And GLONASS Systems In Geodetic Satellite Measurements

    Science.gov (United States)

    Maciuk, Kamil

    2015-12-01

    The article shows the results of satellites measurements elaborations using GPS & GLONASS signals. The aim of this article is to define the influence of adding GLONASS signals on position determination accuracy. It especially concerns areas with big horizon coverages. Object of the study were analysis of DOP coefficients, code and RTK solutions, and usage of satellite techniques in levelling. The performed studies and analysis show that integrated GPS-GLONASS satellite measurements provide possibility to achieve better results than measurements using single navigation satellite system (GPS).

  6. Development of a Novel Embedded Relay Lens Microscopic Hyperspectral Imaging System for Cancer Diagnosis: Use of the Mice with Oral Cancer to Be the Example

    OpenAIRE

    Yao-Fang Hsieh; Mang Ou-Yang; Jeng-Ren Duann; Jin-Chern Chiou; Nai-Wen Chang; Chia-Ing Jan; Ming-Hsui Tsai; Shuen-De Wu; Yung-Jiun Lin; Cheng-Chung Lee

    2012-01-01

    This paper develops a novel embedded relay lens microscopic hyperspectral imaging system (ERL-MHSI) with high spectral resolution (nominal spectral resolution of 2.8 nm) and spatial resolution (30 μm × 10 μm) for cancer diagnosis. The ERL-MHSI system has transmittance and fluorescence mode. The transmittance can provide the morphological information for pathological diagnosis, and the fluorescence of cells or tissue can provide the characteristic signature for identification of normal and ...

  7. Morphology of Dwarf Galaxies in Isolated Satellite Systems

    Science.gov (United States)

    Ann, Hong Bae

    2017-08-01

    The environmental dependence of the morphology of dwarf galaxies in isolated satellite systems is analyzed to understand the origin of the dwarf galaxy morphology using the visually classified morphological types of 5836 local galaxies with z ≲ 0.01. We consider six sub-types of dwarf galaxies, dS0, dE, dE_{bc}, dSph, dE_{blue}, and dI, of which the first four sub-types are considered as early-type and the last two as late-type. The environmental parameters we consider are the projected distance from the host galaxy (r_{p}), local and global background densities, and the host morphology. The spatial distributions of dwarf satellites of early-type galaxies are much different from those of dwarf satellites of late-type galaxies, suggesting the host morphology combined with r_{p} plays a decisive role on the morphology of the dwarf satellite galaxies. The local and global background densities play no significant role on the morphology of dwarfs in the satellite systems hosted by early-type galaxies. However, in the satellite system hosted by late-type galaxies, the global background densities of dE and dSph satellites are significantly different from those of dE_{bc}, dE_{blue}, and dI satellites. The blue-cored dwarf satellites (dE_{bc}) of early-type galaxies are likely to be located at r_{p} > 0.3 Mpc to keep their cold gas from the ram pressure stripping by the hot corona of early-type galaxies. The spatial distribution of dE_{bc} satellites of early-type galaxies and their global background densities suggest that their cold gas is intergalactic material accreted before they fall into the satellite systems.

  8. Stability of Satellites in Closely Packed Planetary Systems

    CERN Document Server

    Payne, Matthew J; Holman, Matthew J; Perets, Hagai B

    2013-01-01

    We perform numerical integrations of four-body (star, planet, planet, satellite) systems to investigate the stability of satellites in planetary Systems with Tightly-packed Inner Planets (STIPs). We find that the majority of closely-spaced stable two-planet systems can stably support satellites across a range of parameter-space which is only slightly decreased compared to that seen for the single-planet case. In particular, circular prograde satellites remain stable out to $\\sim 0.4 R_H$ (where $R_H$ is the Hill Radius) as opposed to $\\sim 0.5 R_H$ in the single-planet case. A similarly small restriction in the stable parameter-space for retrograde satellites is observed, where planetary close approaches in the range 2.5 to 4.5 mutual Hill radii destabilize most satellites orbits only if $a\\sim 0.65 R_H$. In very close planetary pairs (e.g. the 12:11 resonance) the addition of a satellite frequently destabilizes the entire system, causing extreme close-approaches and the loss of satellites over a range of cir...

  9. A Cooperative Network Coding Strategy for the Interference Relay Channel

    CERN Document Server

    Bui, Huyen-Chi; Lacan, Jerome; Boucheret, Marie-Laure

    2012-01-01

    In this paper, we study an interference relay network with a satellite as relay. We propose a cooperative strategy based on physical layer network coding and superposition modulation decoding for uni-directional communications among users. The performance of our solution in terms of throughput is evaluated through capacity analysis and simulations that include practical constraints such as the lack of synchronization in time and frequency. We demonstrate throughputs significantly larger than the classical time sharing case.

  10. Joint Polar Satellite System Common Ground System Overview

    Science.gov (United States)

    Jamilkowski, M. L.; Smith, D. C.

    2011-12-01

    Jointly acquired by NOAA & NASA, the next-generation civilian environmental satellite system, Joint Polar Satellite System (JPSS), will supply the afternoon orbit & ground system of the restructured NPOESS program. JPSS will replace NOAA's current POES satellites and the ground processing part of both POES & DoD's Defense Weather Satellite System (DWSS)(DMSP replacement). JPSS sensors will collect meteorological, oceanographic, climatological and solar-geophysical data. The ground system, or JPSS Common Ground System (CGS), has 6 integrated product teams/segments: Command, Control & Communications (C3S); Interface Data Processing (IDPS); Field Terminal (FTS); Systems Engineering, Integration & Test (SEIT); Operations & Support (O&S); and Sustainment developed by Raytheon Intelligence & Information Systems. The IDPS will process JPSS data to provide Environmental Data Records (EDRs) to NOAA & DoD processing centers beginning with the NPOESS Preparatory Project (NPP) and through JPSS & DWSS eras. C3S will: manage overall JPSS & DWSS missions from control/status of space/ground assets to ensure timely delivery of high-quality data to IDPS; provide globally-distributed ground assets to collect/transport mission, telemetry and command data between satellites & processing locations; provide all commanding & state-of-health monitoring functions of NPP, JPSS and DWSS satellites, and delivery of mission data to each Central IDP and monitor/report system-wide health/status and data communications with external systems and between CGS segments. SEIT leads the overall effort, including: manage/coordinate/execute JPSS CGS activities with NASA participation/oversight; plan/conduct all activities related to systems engineering, develop & ensure completeness of JPSS CGS functional & technical baselines and perform integration, deployment, testing and verification; sponsor/support modeling & simulation, performance analysis and trade studies; provide engineering for the product

  11. Relaying Strategies and Protocols for Efficient Wireless Networks

    KAUST Repository

    Zafar, Ammar

    2014-10-01

    Next generation wireless networks are expected to provide high data rate and satisfy the Quality-of-Service (QoS) constraints of the users. A significant component of achieving these goals is to increase the effi ciency of wireless networks by either optimizing current architectures or exploring new technologies which achieve that. The latter includes revisiting technologies which were previously proposed, but due to a multitude of reasons were ignored at that time. One such technology is relaying which was initially proposed in the latter half of the 1960s and then was revived in the early 2000s. In this dissertation, we study relaying in conjunction with resource allocation to increase the effi ciency of wireless networks. In this regard, we differentiate between conventional relaying and relaying with buffers. Conventional relaying is traditional relaying where the relay forwards the signal it received immediately. On the other hand, in relaying with buffers or buffer-aided relaying as it is called, the relay can store received data in its buffer and forward it later on. This gives the benefit of taking advantage of good channel conditions as the relay can only transmit when the channel conditions are good. The dissertation starts with conventional relaying and considers the problem of minimizing the total consumed power while maintaining system QoS. After upper bounding the system performance, more practical algorithms which require reduced feedback overhead are explored. Buffer-aided relaying is then considered and the joint user-and-hop scheduler is introduced which exploits multi-user diversity (MUD) and 5 multi-hop diversity (MHD) gains together in dual-hop broadcast channels. Next joint user-and-hop scheduling is extended to the shared relay channel where two source-destination pairs share a single relay. The benefits of buffer-aided relaying in the bidirectional relay channel utilizing network coding are then explored. Finally, a new transmission protocol

  12. Optimal Relay Power Allocation for Amplify-and-Forward Relay Networks with Non-linear Power Amplifiers

    OpenAIRE

    Zhang, Chao; Ren, Pinyi; Peng, Jingbo; Wei, Guo; Du, Qinghe; Wang, Yichen

    2011-01-01

    In this paper, we propose an optimal relay power allocation of an Amplify-and-Forward relay networks with non-linear power amplifiers. Based on Bussgang Linearization Theory, we depict the non-linear amplifying process into a linear system, which lets analyzing system performance easier. To obtain spatial diversity, we design a complete practical framework of a non-linear distortion aware receiver. Consider a total relay power constraint, we propose an optimal power allocation scheme to maxim...

  13. RELAY ASSISTED TRANSMISSSION WITH BIT-INTERLEAVED CODED MODULATION

    Institute of Scientific and Technical Information of China (English)

    Meng Qingmin; You Xiaohu; John Boyer

    2006-01-01

    We investigate an adaptive cooperative protocol in a Two-Hop-Relay (THR) wireless system that combines the following: (1) adaptive relaying based on repetition coding; (2) single or two transmit antennas and one receive antenna configurations for all nodes, each using high order constellation; (3) Bit-Interleaved Coded Modulation (BICM). We focus on a simple decoded relaying (i.e. no error correcting at a relay node)and simple signal quality thresholds for relaying. Then the impact of the two simple thresholds on the system performance is studied. Our results suggest that compared with the traditional scheme for direct transmission,the proposed scheme can increase average throughput in high spectral efficiency region with low implementation-cost at the relay.

  14. 14/12-GHz-band satellite communication services

    Science.gov (United States)

    Hayashi, Kunihiro; Nagaki, Kiyoaki; Mori, Yasuo

    1990-01-01

    Three new systems for integrated TV-relay services have been developed: Satellite Video Comunication Service (SVCS) and Satellite Digital Communication Service (SDCS), with Japan's 14/12-GHz-band commercial communication satellites. These systems have been in commercial use since May 1989. Usually SVCS and SDCS have been provided using Ka-band (30/20 GHz-band) of CS-2 and Cs-3. This paper provides an overview of the design, the performance, and the systems of the new 14/12-GHz-band satellite communication services.

  15. Amplify-and-forward relaying in wireless communications

    CERN Document Server

    Rodriguez, Leonardo Jimenez; Le-Ngoc, Tho

    2015-01-01

    This SpringerBrief explores the advantage of relaying techniques in addressing the increasing demand for high data rates and reliable services over the air. It demonstrates how to design cost-effective relay systems that provide high spectral efficiency and fully exploit the diversity of the relay channel. The brief covers advances in achievable rates, power allocation schemes, and error performance for half-duplex (HD) and full-duplex (FD) amplify-and-forward (AF) single-relay systems. The authors discuss the capacity and respective optimal power allocation for a wide range of HD protocols ov

  16. 分布式卫星系统数传调度研究%Research on Transmission Task Scheduling for Distributed Satellite Systems

    Institute of Scientific and Technical Information of China (English)

    国晓博; 刘金灿; 周红彬

    2016-01-01

    With the increase of in⁃orbit sensing satellite,the current relay satellite system is facing a major challenge in terms of data transmission performance.While the payload capability is restricted by satellite platform,the distributed satellite system is a practi⁃cal solution to tremendously improve the performance of relay satellite system. The transmission task scheduling problem of distributed satellite system is studied, a multi⁃satellites multi⁃tasks transmission task scheduling model is proposed based on PSO algorithm by jointly considering constraint conditions such as the visible time windows between distributed satellite systems and user satellites in MEO and LEO, the residual resources of satellite systems and the property of user transmission tasks. Considering the number of scheduling tasks in practice,the typical PSO algorithm is modified and the proposed algorithm is verified by computer simulations.%近年来随着我国在轨遥感卫星数量的不断增加,对当前中继星系统的数传能力提出了更高的要求。在卫星平台载荷能力受限的情况下,分布式卫星系统成为大幅提升中继星系统性能的可行方案。针对分布式卫星系统的数传任务调度问题,综合考虑系统与中低轨航天器用户之间的可见时间窗口、卫星剩余资源及数传任务属性等约束条件,提出了基于粒子群优化( PSO)的多星多任务数传调度方法。根据实际中继系统任务量级对经典 PSO 算法进行了改进,并通过计算机仿真验证了改进算法的有效性。

  17. Protective relaying theory and applications

    CERN Document Server

    Elmore, Walter A

    2003-01-01

    Targeting the latest microprocessor technologies for more sophisticated applications in the field of power system short circuit detection, this revised and updated source imparts fundamental concepts and breakthrough science for the isolation of faulty equipment and minimization of damage in power system apparatus. The Second Edition clearly describes key procedures, devices, and elements crucial to the protection and control of power system function and stability. It includes chapters and expertise from the most knowledgeable experts in the field of protective relaying, and describes micropro

  18. Alternate MIMO relaying with three AF relays using interference alignment

    KAUST Repository

    Park, Kihong

    2012-06-01

    In this paper, we study a two-hop half-duplex relaying network with one source, one destination, and three amplify-and-forward (AF) relays equipped with M antennas each. We consider alternate transmission to compensate for the inherent loss of capacity pre-log factor 1/2 in half duplex mode, where source transmit message to two relays and the other relay alternately. The inter-relay interference caused by alternate transmission is aligned to make additional degrees of freedom (DOFs). It is shown that the proposed scheme enables us to exploit 3M/4 DOFs compared with the M/2 DOFs of conventional AF relaying. More specifically, suboptimal linear filter designs for a source and three relays are proposed to maximize the achievable sum-rate. We verify using some selected numerical results that the proposed filter designs give significant improvement of the sum-rate over a naive filter and conventional relaying schemes. © 2012 IEEE.

  19. Analysis of Maritime Mobile Satellite Communication Systems

    Science.gov (United States)

    1988-12-01

    Communications and Surveil- lance, IEE, Conference publication n.95, 13-15 Mar. 1973. 2. Y. Karasawa and T. Shiokawa , Characteristics of L-Band Multipath Fading... Shiokawa . Analysis of M-ultipath Fading due to Sea Suface Scattering in Maritime Satellite Communication, Technical Group on Antennas and Propagation. IECE

  20. Isolated Galaxies and Isolated Satellite Systems

    CERN Document Server

    Ann, H B; Choi, Yun-Young

    2009-01-01

    We search for isolated galaxies using a volume-limited sample of galaxies with 0.02r_{vir,nei} and \\rho <\\bar{\\rho} well segregates the CIG galaxies. We confirm the morphology conformity between the host and their satellites, which suggests importance of hydrodynamic interaction among galaxies within their virial radii in galaxy evolution.

  1. Architecture analysis of the simplified libration point satellite navigation system

    Science.gov (United States)

    Zhang, Lei; Xu, Bo

    2016-10-01

    The libration point satellite navigation system is a novel navigation architecture that consists of satellites located in periodic orbits around the Earth-Moon libration points. Superiorities of the proposed system lie in its autonomy and extended navigation capability, which have been proved in our previous works. Based on the candidate architectures obtained before, a detailed analysis of the simplified libration point satellite navigation system, i.e. the Earth-Moon L1,2 two-satellite constellation, is conducted in this work. Firstly, relation between orbits amplitude is derived for the candidate two-satellite constellations to ensure continuous crosslink measurements between libration point satellites. Then, with the use of a reference lunar exploration mission scenario, navigation performances of different constellation configurations are evaluated by Monte-Carlo simulations. The simulation results indicate that the amplitude and initial phase combinations of libration point orbits have direct effect on the performance of the two-satellite constellations. By using a cooperative evolutionary algorithm for configuration parameter optimization, some optimal constellations are finally obtained for the simplified navigation architecture. The results obtained in this paper may be a reference for future system design.

  2. Performance analysis of two-way amplify and forward relaying with adaptive modulation over multiple relay network

    KAUST Repository

    Hwang, Kyusung

    2011-02-01

    In this letter, we propose two-way amplify-and-forward relaying in conjunction with adaptive modulation in order to improve spectral efficiency of relayed communication systems while monitoring the required error performance. We also consider a multiple relay network where only the best relay node is utilized so that the diversity order increases while maintaining a low complexity of implementation as the number of relays increases. Based on the best relay selection criterion, we offer an upper bound on the signal-to-noise ratio to keep the performance analysis tractable. Our numerical examples show that the proposed system offers a considerable gain in spectral efficiency while satisfying the error rate requirements. © 2011 IEEE.

  3. Use of CDMA access technology in mobile satellite systems

    Science.gov (United States)

    Ramasastry, Jay; Wiedeman, Bob

    1995-01-01

    Use of Code Division Multiple Access (CDMA) technology in terrestrial wireless systems is fairly well understood. Similarly, design and operation of Power Control in a CDMA-based system in a terrestrial environment is also well established. Terrestrial multipath characteristics, and optimum design of the CDMA receiver to deal with multipath and fading conditions are reliably established. But the satellite environment is different. When the CDMA technology is adopted to the satellite environment, other design features need to be incorporated (for example; interleaving, open-loop and closed-loop power control design, diversity characteristics) to achieve comparable level of system performance. In fact, the GLOBALSTAR LEO/MSS system has incorporated all these features. Contrary to some published reports, CDMA retains the advantages in the satellite environment that are similar to those achieved in the terrestrial environment. This document gives a description of the CDMA waveform and other design features adopted for mobile satellite applications.

  4. Intelligent fault isolation and diagnosis for communication satellite systems

    Science.gov (United States)

    Tallo, Donald P.; Durkin, John; Petrik, Edward J.

    1992-01-01

    Discussed here is a prototype diagnosis expert system to provide the Advanced Communication Technology Satellite (ACTS) System with autonomous diagnosis capability. The system, the Fault Isolation and Diagnosis EXpert (FIDEX) system, is a frame-based system that uses hierarchical structures to represent such items as the satellite's subsystems, components, sensors, and fault states. This overall frame architecture integrates the hierarchical structures into a lattice that provides a flexible representation scheme and facilitates system maintenance. FIDEX uses an inexact reasoning technique based on the incrementally acquired evidence approach developed by Shortliffe. The system is designed with a primitive learning ability through which it maintains a record of past diagnosis studies.

  5. Propagation considerations in the American Mobile Satellite system design

    Science.gov (United States)

    Kittiver, Charles; Sigler, Charles E., Jr.

    1993-01-01

    An overview of the American Mobile Satellite Corporation (AMSC) mobile satellite services (MSS) system with special emphasis given to the propagation issues that were considered in the design is presented. The aspects of the voice codec design that effect system performance in a shadowed environment are discussed. The strategies for overcoming Ku-Band rain fades in the uplink and downlink paths of the gateway station are presented. A land mobile propagation study that has both measurement and simulation activities is described.

  6. Design of House Keeping System for a Certain Micro Satellite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper presents the design of hardware and software of the house keeping system for a certain microsatellite. The system uses microelectronic technique, large scale integrated circuits, processors and computers which has the advantages of strong function, high flexibility and reliability, It satisfies the requirements for efficient performance,light weight, small volume,and low consumption of power for microsatellite.

  7. CERN Relay Race

    CERN Multimedia

    2011-01-01

    The CERN relay race will take place around the Meyrin site on Thursday 19 May starting at 12-15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details of the course and of how to register your team for the relay race can be found here. Some advice for all runners from the Medical Service can also be found here.   

  8. Development of Sequential Calculating Type Autonomous Stabilizing Controller for Maintaining Transient Stability in case of Backup Relay Operation in Load System

    Science.gov (United States)

    Kobayashi, Ryoji; Maekawa, Kazuo; Shimomura, Kimihiko; Sasaki, Takashi; Kowada, Yasuyuki; Maeda, Toru

    A new Autonomous Stabilizing Controller (ASC) has been developed, which is based on the concept of using only locall information measured at the substation where ASC is installed. ASC prevents the power system from wide-area blackout by shedding generators optimally when a serious fault occurs in 154kV-or-below-voltage power system and is cleared by backup relay. ASC consists of three functions, a function of detecting faults and judging of starting stability calculations (The first function), a function of calculating power system stability (The second function), and a function of selecting optimal generators to be shed (The third function). The first function composes a signal for starting stability calculations when a fault cleared by backup relay is detected. According to the starting signal composed by the first function, the second function executes stability calculations based on equal area criterion. If the result of stability calculations is instable, the third function selects a generator to be shed by considering not only the stabilizing effect but also the quickly restoration after shedding. This paper presents total algorithms applied in ASC.

  9. Satellite Attitude Control System Design considering the Fuel Slosh Dynamics

    Directory of Open Access Journals (Sweden)

    Luiz Carlos Gadelha de Souza

    2014-01-01

    Full Text Available The design of the satellite attitude control system (ACS becomes more complex when the satellite structure has different type of components like, flexible solar panels, antennas, mechanical manipulators, and tanks with fuel. A crucial interaction can occur between the fuel slosh motion and the satellite rigid motion during translational and/or rotational manoeuvre since these interactions can change the satellite centre of mass position damaging the ACS pointing accuracy. Although, a well-designed controller can suppress such disturbances quickly, the controller error pointing may be limited by the minimum time necessary to suppress such disturbances thus affecting the satellite attitude acquisition. As a result, the design of the satellite controller needs to explore the limits between the conflicting requirements of performance and robustness. This paper investigates the effects of the interaction between the liquid motion (slosh and the satellite dynamics in order to predict what the damage to the controller performance and robustness is. The fuel slosh dynamics is modelled by a pendulum which parameters are identified using the Kalman filter technique. This information is used to design the satellite controller by the linear quadratic regulator (LQR and linear quadratic Gaussian (LQG methods to perform a planar manoeuvre assuming thrusters are actuators.

  10. Data communications method for mobile network in fourth generation communications system, involves delivering decoded data to mobile station from relay station, where mobile station receives data from both relay and base stations

    DEFF Research Database (Denmark)

    2008-01-01

    The method involves utilizing a base station (BS) (100) to transmit data to a relay station (RS) (110) and a mobile station (MS) (120), where the data includes two messages. The BS is utilized to transmit the two messages by utilizing a linear combination method, and the data is received in the R...

  11. Advanced Strategic and Tactical Relay Request Management for the Mars Relay Operations Service

    Science.gov (United States)

    Allard, Daniel A.; Wallick, Michael N.; Gladden, Roy E.; Wang, Paul; Hy, Franklin H.

    2013-01-01

    This software provides a new set of capabilities for the Mars Relay Operations Service (MaROS) in support of Strategic and Tactical relay, including a highly interactive relay request Web user interface, mission control over relay planning time periods, and mission management of allowed strategic vs. tactical request parameters. Together, these new capabilities expand the scope of the system to include all elements critical for Tactical relay operations. Planning of replay activities spans a time period that is split into two distinct phases. The first phase is called Strategic, which begins at the time that relay opportunities are identified, and concludes at the point that the orbiter generates the flight sequences for on board execution. Any relay request changes from this point on are called Tactical. Tactical requests, otherwise called Orbit - er Relay State Changes (ORSC), are highly restricted in terms of what types of changes can be made, and the types of parameters that can be changed may differ from one orbiter to the next. For example, one orbiter may be able to delay the start of a relay request, while another may not. The legacy approach to ORSC management involves exchanges of e-mail with "requests for change" and "acknowledgement of approval," with no other tracking of changes outside of e-mail folders. MaROS Phases 1 and 2 provided the infrastructure for strategic relay for all supported missions. This new version, 3.0, introduces several capabilities that fully expand the scope of the system to include tactical relay. One new feature allows orbiter users to manage and "lock" Planning Periods, which allows the orbiter team to formalize the changeover from Strategic to Tactical operations. Another major feature allows users to interactively submit tactical request changes via a Web user interface. A third new feature allows orbiter missions to specify allowed tactical updates, which are automatically incorporated into the tactical change process

  12. 622 Mbps High-speed satellite communication system for WINDS

    Science.gov (United States)

    Ogawa, Yasuo; Hashimoto, Yukio; Yoshimura, Naoko; Suzuki, Ryutaro; Gedney, Richard T.; Dollard, Mike

    2006-07-01

    WINDS is the experimental communications satellite currently under joint development by Japanese Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT). The high-speed satellite communication system is very effective for quick deployment of high-speed networks economically. The WINDS will realize ultra high-speed networking and demonstrate operability of satellite communication systems in high-speed internet. NICT is now developing high-speed satellite communication system for WINDS. High-speed TDMA burst modem with high performance TPC error correction is underdevelopment. Up to the DAC on the transmitter and from the ADC on the receiver, all modem functions are performed in the digital processing technology. Burst modem has been designed for a user data rate up to 1244 Mbps. NICT is developing the digital terminal as a user interface and a network controller for this earth station. High compatibility with the Internet will be provided.

  13. Engineering satellite-based navigation and timing global navigation satellite systems, signals, and receivers

    CERN Document Server

    Betz, J

    2016-01-01

    This book describes the design and performance analysis of satnav systems, signals, and receivers. It also provides succinct descriptions and comparisons of all the world’s satnav systems. Its comprehensive and logical structure addresses all satnav signals and systems in operation and being developed. Engineering Satellite-Based Navigation and Timing: Global Navigation Satellite Systems, Signals, and Receivers provides the technical foundation for designing and analyzing satnav signals, systems, and receivers. Its contents and structure address all satnav systems and signals: legacy, modernized, and new. It combines qualitative information with detailed techniques and analyses, providing a comprehensive set of insights and engineering tools for this complex multidisciplinary field. Part I describes system and signal engineering including orbital mechanics and constellation design, signal design principles and underlying considerations, link budgets, qua tifying receiver performance in interference, and e...

  14. IMPGSS - International Medical Program Global Satellite System

    Science.gov (United States)

    2004-02-01

    additional comments regarding the significance of working with Tachyon and NASK under this Contract). 5.2.5 Requirements - Country/Region Assessments...services on a tentative exploratory basis by Tachyon ]. 5.2.7 Program Development Deliverable A 007 This is currently summarized in the Program Content...based satellite transmissions and transmission pricing based on segmented, limited use data volumes via Tachyon . " A more involved use of evaluation

  15. A Survey of Satellite Communications System Vulnerabilities

    Science.gov (United States)

    2008-06-01

    Myers, Raymond M. Nuber, Jaime L. Prieto , Jr., and Eric R. Wiswell, “Fast Packet Vs. Circuit Switch and Bent Pipe Satellite Network Architectures...2008. 81. Howell, Alan , “INMARSAT HORIZONS PROGRAM,” Institution of Electrical Engineers, Savoy Place, London, 1998. 82. http://www.infosec.gov.hk...ntia-rpt/02- 393/02-393.pdf, NTIA Report 02-393, pages 1-20, May 2002. 134. Sardella, Alan , “Securing Provider Backbone Networks: Packet Filters

  16. An operational satellite remote sensing system for ocean fishery

    Institute of Scientific and Technical Information of China (English)

    MAOZhihua; ZHUQiankun; PANDelu

    2004-01-01

    Ocean environmental information is very important to supporting the fishermen in fishing and satellite remote sensing technology can provide it in large scale and in near real-time. Ocean fishery locations are always far away beyond the coverage of the satellite data received by a land-based satellite receiving station. A nice idea is to install the satellite ground station on a fishing boat. When the boat moves to a fishery location, the station can receive the satellite data to cover the fishery areas. One satellite remote sensing system was once installed in a fishing boat and served fishing in the North Pacific fishery areas when the boat stayed there. The system can provide some oceanic environmental charts such as sea surface temperature (SST) and relevant derived products which are in most popular use in fishery industry. The accuracy of SST is the most important and affects the performance of the operational system, which is found to be dissatisfactory. Many factors affect the accuracy of SST and it is difficult to increase the accuracy by SST retrieval algorithms and clouds detection technology. A new technology of temperature error control is developed to detect the abnormity of satellite-measured SST. The performance of the technology is evaluated to change the temperature bias from-3.04 to 0.05 ℃ and the root mean square (RMS) from 5.71 to 1.75 ℃. It is suitable for employing in an operational satellite-measured SST system and improves the performance of the system in fishery applications. The system has been running for 3 a and proved to be very useful in fishing. It can help to locate the candidates of the fishery areas and monitor the typhoon which is very dangerous to the safety of fishing boats.

  17. Tsinghua-1 Micro-Satellite Power System Architecture and Design

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Tsinghua-1 Micro-satellite, the first satellite made by Tsinghua University, was launched in 2000. The power system of the Tsinghua-1 Micro-satellite is one of the most important subsystems. It provides all the power for the satellite platform and the payloads. The power system design includes the regulation,protection and distribution of a 4 × 35 W solar array and 7 Ah NiCd batteries. This subsystem essentially offerstwo buses: an unregulated 14 V bus and a regulated 5 V bus. All distributed power lines to the users areprotected by current tripping switches. In addition, some essential loads, such as the tele-command system,are supplied through fuses. The Tsinghua-1 Micro-satellite power system provides an efficient, flexible,reliable, and cost-effective solution for small satellites in low earth orbit. A better maximum power pointtracking method has been used to increase reliability margins and to increase the efficiency of the powersystem. The power system reliability was evaluated using several different tests, such as the power boardtest, the assembly integrate test (AIT), the electromagnetic compatibility (EMC) test and the thermal vacuumtest (TVT).``

  18. Uplink Power Control For Earth/Satellite/Earth Communication

    Science.gov (United States)

    Chakraborty, Dayamoy

    1994-01-01

    Proposed control subsystem adjusts power radiated by uplink transmitter in Earth station/satellite relay station/ Earth station communication system. Adjustments made to compensate for anticipated changes in attenuation by rain. Raw input is a received downlink beacon singal, amplitude of which affected not only by rain fade but also by scintillation, attenuation in atmospheric gases, and diurnal effects.

  19. The Submillimeter Wave Astronomy Satellite (SWAS) solar array system

    Science.gov (United States)

    Sneiderman, Gary

    1993-01-01

    The SWAS (Submillimeter Wave Astronomy Satellite) solar array system is described. It is an innovative approach to meet the missions requirements. The SWAS satellite provides a three axis stabilized platform to survey a variety of galactic cloud structures. This system includes highly reliable, lightweight launch latch, deployment, and lock mechanisms, and solar array panels that provide the maximum solar cell area. The design of the solar arrays are the result of system trades that included instrument and spacecraft thermal constraints, attitude control system maneuvering rates and pointing accuracies, the power system, and the spacecraft structure.

  20. 2005 CERN Relay Race

    CERN Multimedia

    Patrice Loiez

    2005-01-01

    The CERN Relay Race takes place each year in May and sees participants from all areas of the CERN staff. The winners in 2005 were The Shabbys with Los Latinos Volantes in second and Charmilles Technologies a close third. To add a touch of colour and levity, the CERN Jazz Club provided music at the finishing line.

  1. CERN Relay Race

    CERN Document Server

    2009-01-01

    The CERN relay race, now in its 39th year, is already a well-known tradition, but this year the organizers say the event will have even more of a festival feeling. Just off the starting line of the CERN relay race.For the past few years, spectators and runners at the CERN relay race have been able to enjoy a beer while listening to music from the CERN music and jazz clubs. But this year the organizers are aiming for "even more of a festival atmosphere". As David Nisbet, President of the CERN running club and organizer of the relay race, says: "Work is not just about getting your head down and doing the theory, it’s also about enjoying the company of your colleagues." This year, on top of music from the Santa Luis Band and the Canettes Blues Band, there will be demonstrations from the Aikido and softball clubs, a stretching session by the Fitness club, as well as various stalls and of course, the well-earned beer from AGLUP, the B...

  2. 3-dimensional current collection model. [of Tethered Satellite System 1

    Science.gov (United States)

    Hwang, Kai-Shen; Shiah, A.; Wu, S. T.; Stone, N.

    1992-01-01

    A three-dimensional, time dependent current collection model of a satellite has been developed for the TSS-1 system. The system has been simulated particularly for the Research of Plasma Electrodynamics (ROPE) experiment. The Maxwellian distributed particles with the geomagnetic field effects are applied in this numerical simulation. The preliminary results indicate that a ring current is observed surrounding the satellite in the equatorial plane. This ring current is found between the plasma sheath and the satellite surface and is oscillating with a time scale of approximately 1 microsec. This is equivalent to the electron plasma frequency. An hour glass shape of electron distribution was observed when the viewing direction is perpendicular to the equatorial plane. This result is consistent with previous findings from Linson (1969) and Antoniades et al. (1990). Electrons that are absorbed by the satellite are limited from the background ionosphere as indicated by Parker and Murphy (1967).

  3. Information content in reflected global navigation satellite system signals

    DEFF Research Database (Denmark)

    Høeg, Per; Carlstrom, Anders

    2011-01-01

    The direct signals from satellites in global satellite navigation satellites systems (GNSS) as, GPS, GLONASS and GALILEO, constitute the primary source for positioning, navigation and timing from space. But also the reflected GNSS signals contain an important information content of signal travel...... times and the characteristics of the reflecting surfaces and structure. Ocean reflected signals from GNSS satellite systems reveal the mean height, the significant wave height and the roughness of the ocean. The estimated accuracy of the average surface height can be as low as 10 cm. For low elevations......, the signals reveal the incoherent scatter process at the reflection zone. By using open-loop high-precision GNSS receivers, it is possible to provide the in-phase and quadrature components of the signal at high sample rates, which enables investigation of the spectral signatures of the observations...

  4. Phase control system concepts and simulations. [solar power satellite system

    Science.gov (United States)

    Lindsay, V. C.

    1980-01-01

    A phase control system concept for a solar power satellite is proposed which partitions the system into three major levels. The first level of phase control consists of a reference phase distribution system implemented in the form of phase distribution tree structure. The major purpose of the tree structure is to electronically compensate for the phase shift due to the transition path lengths from the center of the spacetenna to each phase control center located in each subarray. In the reference system, this is accomplished using the master slave returnable timing system technique. The second level of phase control consists of the beam steering and microwave power generating system which houses the power transponders. This transponder consists of a set of phase conjugation multipliers driven by the reference phase distribution system output and the output of a pilot spread spectrum receiver which accepts the received pilot via a diplexer connected to a separate receive horn or the subarray itself. The output of the phase conjugation circuits serve as inputs to the third level of the phase control system. The third level of phase control is associated with maintaining an equal and constant phase shift through the microwave power amplifier devices while minimizing the associated phase noise effects on the generated power beam. This is accomplished by providing a phase locked loop around each high power amplifier.

  5. Opportunistic Cognitive Relaying: A Win-Win Spectrum Sharing Scheme

    Directory of Open Access Journals (Sweden)

    Luo Haiyan

    2010-01-01

    Full Text Available A cost-effective spectrum sharing architecture is proposed to enable the legacy noncognitive secondary system to coexist with the primary system. Specifically, we suggest to install a few intermediate nodes, namely, the cognitive relays, to conduct the spectrum sensing and coordinate the spectrum access. To achieve the goal of win-win between primary and secondary systems, the cognitive relay may act as a cooperator for both of them, and an Opportunistic Cognitive Relaying (OCR scheme is specially devised. In this scheme, the cognitive relay opportunistically switches among three different working modes, that is, Relay for Primary Link (RPL, Relay for Secondary Link (RSL, or Relay for Neither of the Links (RNL, respectively, based on the channel-dependent observation of both systems. In addition, the transmit power for cognitive relay and secondary transmitter in each mode are optimally determined by maximizing the transmission rate of secondary system while keeping or even reducing the outage probability of primary system. Simulation results validate the efficiency of the proposed spectrum sharing scheme.

  6. Hybrid Atom Electrostatic System for Satellite Geodesy

    Science.gov (United States)

    Zahzam, Nassim; Bidel, Yannick; Bresson, Alexandre; Huynh, Phuong-Anh; Liorzou, Françoise; Lebat, Vincent; Foulon, Bernard; Christophe, Bruno

    2017-04-01

    The subject of this poster comes within the framework of new concepts identification and development for future satellite gravity missions, in continuation of previously launched space missions CHAMP, GRACE, GOCE and ongoing and prospective studies like NGGM, GRACE 2 or E-GRASP. We were here more focused on the inertial sensors that complete the payload of such satellites. The clearly identified instruments for space accelerometry are based on the electrostatic technology developed for many years by ONERA and that offer a high level of performance and a high degree of maturity for space applications. On the other hand, a new generation of sensors based on cold atom interferometry (AI) is emerging and seems very promising in this context. These atomic instruments have already demonstrated on ground impressive results, especially with the development of state-of-the-art gravimeters, and should reach their full potential only in space, where the microgravity environment allows long interaction times. Each of these two types of instruments presents their own advantages which are, for the electrostatic sensors (ES), their demonstrated short term sensitivity and their high TRL, and for AI, amongst others, the absolute nature of the measurement and therefore no need for calibration processes. These two technologies seem in some aspects very complementary and a hybrid sensor bringing together all their assets could be the opportunity to take a big step in this context of gravity space missions. We present here the first experimental association on ground of an electrostatic accelerometer and an atomic accelerometer and underline the interest of calibrating the ES instrument with the AI. Some technical methods using the ES proof-mass as the Raman Mirror seem very promising to remove rotation effects of the satellite on the AI signal. We propose a roadmap to explore further in details and more rigorously this attractive hybridization scheme in order to assess its potential

  7. A low complexity algorithm for multiple relay selection in two-way relaying Cognitive Radio networks

    KAUST Repository

    Alsharoa, Ahmad M.

    2013-06-01

    In this paper, a multiple relay selection scheme for two-way relaying cognitive radio network is investigated. We consider a cooperative Cognitive Radio (CR) system with spectrum sharing scenario using Amplify-and-Forward (AF) protocol, where licensed users and unlicensed users operate on the same frequency band. The main objective is to maximize the sum rate of the unlicensed users allowed to share the spectrum with the licensed users by respecting a tolerated interference threshold. A practical low complexity heuristic approach is proposed to solve our formulated optimization problem. Selected numerical results show that the proposed algorithm reaches a performance close to the performance of the optimal multiple relay selection scheme either with discrete or continuous power distributions while providing a considerable saving in terms of computational complexity. In addition, these results show that our proposed scheme significantly outperforms the single relay selection scheme. © 2013 IEEE.

  8. Educational software tool for protection system engineers: distance relay; Herramienta educativa para la formacion de ingenieros en protecciones electricas: relevador de distancia

    Energy Technology Data Exchange (ETDEWEB)

    Trujillo-Guajardo, L.A.; Conde-Enriquez, A. [Universidad Autonoma de Nuevo Leon, Nuevo Leon (Mexico)]. E-mail: luistrujillo84@gmail.com; con_de@yahoo.com

    2012-04-15

    In this article, a graphical software tool is presented; this tool is based on the education of protection system engineers. The theoretical fundaments used for the design of operation characteristics of distance relays and their algorithms are presented. The software allows the evaluation and analysis of real time events or simulated ones of every stage of design of the distance relay. Some example cases are presented to illustrate the activities that could be done with the graphical software tool developed. [Spanish] En este articulo se presenta una herramienta computacional grafica para apoyar la formacion de ingenieros en protecciones electricas. Los fundamentos teoricos para el diseno de caracteristicas de operacion de relevadores de distancia, asi como las rutinas de programacion de un relevador de distancia son presentados. La herramienta desarrollada permite la evaluacion de las etapas de diseno de relevadores y el analisis de la operacion ante eventos reales o simulados. Se presentan algunos casos de ejemplo para ilustrar las actividades didacticas que son posibles de realizar con la herramienta presentada.

  9. MIMO Four-Way Relaying

    DEFF Research Database (Denmark)

    Liu, Huaping; Sun, Fan; De Carvalho, Elisabeth;

    2013-01-01

    Two-way relaying in wireless systems has initiated a large research effort during the past few years. Nevertheless, it represents only a specific traffic pattern and it is of interest to investigate other traffic patterns where such a simultaneous processing of information flows can bring...... in such a way that one RS and the terminals associated with it do not interfere with the other RS, and vice versa. We introduce and analyze a two-phase transmission scheme to serve the four-way traffic pattern defined in this scenario. Each phase consists of combined broadcast and multiple access. We analyze...

  10. Guidance and Control System for a Satellite Constellation

    Science.gov (United States)

    Bryson, Jonathan Lamar; Cox, James; Mays, Paul Richard; Neidhoefer, James Christian; Ephrain, Richard

    2010-01-01

    A distributed guidance and control algorithm was developed for a constellation of satellites. The system repositions satellites as required, regulates satellites to desired orbits, and prevents collisions. 1. Optimal methods are used to compute nominal transfers from orbit to orbit. 2. Satellites are regulated to maintain the desired orbits once the transfers are complete. 3. A simulator is used to predict potential collisions or near-misses. 4. Each satellite computes perturbations to its controls so as to increase any unacceptable distances of nearest approach to other objects. a. The avoidance problem is recast in a distributed and locally-linear form to arrive at a tractable solution. b. Plant matrix values are approximated via simulation at each time step. c. The Linear Quadratic Gaussian (LQG) method is used to compute perturbations to the controls that will result in increased miss distances. 5. Once all danger is passed, the satellites return to their original orbits, all the while avoiding each other as above. 6. The delta-Vs are reasonable. The controller begins maneuvers as soon as practical to minimize delta-V. 7. Despite the inclusion of trajectory simulations within the control loop, the algorithm is sufficiently fast for available satellite computer hardware. 8. The required measurement accuracies are within the capabilities of modern inertial measurement devices and modern positioning devices.

  11. Multiple relay selection for delay-limited applications

    KAUST Repository

    Alsharoa, Ahmad M.

    2013-12-01

    A multiple relay selection system model that implements the decode-and-forward mode is investigated. All communication nodes are assumed to be equipped by multiple antennas. Furthermore, lattices space-time coded multiple-input multiple-output half duplex channel is applied. The main goal is to increase the throughput of the system by selecting multiple number of relays. The selection criteria depends on the maximum decoding delay at relays where the system implements a decoding time-out algorithm at each relay. This leads to a significant saving in the overall system power consumptions and attempts to solve the relays synchronization problem. All results are presented using numerical simulations. © 2012 IEEE.

  12. Applications of two-way satellite time and frequency transfer in the BeiDou navigation satellite system

    Science.gov (United States)

    Zhou, ShanShi; Hu, XiaoGong; Liu, Li; Guo, Rui; Zhu, LingFeng; Chang, ZhiQiao; Tang, ChengPan; Gong, XiuQiang; Li, Ran; Yu, Yang

    2016-10-01

    A two-way satellite time and frequency transfer (TWSTFT) device equipped in the BeiDou navigation satellite system (BDS) can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method with high accuracy because most system errors such as orbital error, station position error, and tropospheric and ionospheric delay error can be eliminated by calculating the two-way pseudorange difference. Another method, the multi-satellite precision orbit determination (MPOD) method, can be applied to estimate satellite clock errors. By comparison with MPOD clock estimations, this paper discusses the applications of the BDS TWSTFT clock observations in satellite clock measurement, satellite clock prediction, navigation system time monitor, and satellite clock performance assessment in orbit. The results show that with TWSTFT clock observations, the accuracy of satellite clock prediction is higher than MPOD. Five continuous weeks of comparisons with three international GNSS Service (IGS) analysis centers (ACs) show that the reference time difference between BeiDou time (BDT) and golbal positoning system (GPS) time (GPST) realized IGS ACs is in the tens of nanoseconds. Applying the TWSTFT clock error observations may obtain more accurate satellite clock performance evaluation in the 104 s interval because the accuracy of the MPOD clock estimation is not sufficiently high. By comparing the BDS and GPS satellite clock performance, we found that the BDS clock stability at the 103 s interval is approximately 10-12, which is similar to the GPS IIR.

  13. Improvements and Extensions for Joint Polar Satellite System Algorithms

    Science.gov (United States)

    Grant, K. D.

    2016-12-01

    The National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) are jointly acquiring the next-generation civilian weather satellite system: the Joint Polar Satellite System (JPSS). JPSS replaced the afternoon orbit component and ground processing of the old POES system managed by NOAA. JPSS satellites carry sensors designed to collect meteorological, oceanographic, climatological, and solar-geophysical observations of the earth, atmosphere, and space. The ground processing system for JPSS is the Common Ground System (CGS), and provides command, control, and communications (C3), data processing and product delivery. CGS's data processing capability provides environmental data products (Sensor Data Records (SDRs) and Environmental Data Records (EDRs)) to the NOAA Satellite Operations Facility. The first satellite in the JPSS constellation, S-NPP, was launched in October 2011. The second satellite, JPSS-1, is scheduled for launch in January 2017. During a satellite's calibration and validation (Cal/Val) campaign, numerous algorithm updates occur. Changes identified during Cal/Val become available for implementation into the operational system for both S-NPP and JPSS-1. In addition, new capabilities, such as higher spectral and spatial resolution, will be exercised on JPSS-1. This paper will describe changes to current algorithms and products as a result of S-NPP Cal/Val and related initiatives for improved capabilities. Improvements include Cross Track Infrared Sounder high spectral processing, extended spectral and spatial ranges for Ozone Mapping and Profiler Suite ozone Total Column and Nadir Profiles, and updates to Vegetation Index, Snow Cover, Active Fires, Suspended Matter, and Ocean Color. Updates will include Sea Surface Temperature, Cloud Mask, Cloud Properties, and other improvements.

  14. SOFT project: a new forecasting system based on satellite data

    Science.gov (United States)

    Pascual, Ananda; Orfila, A.; Alvarez, Alberto; Hernandez, E.; Gomis, D.; Barth, Alexander; Tintore, Joaquim

    2002-01-01

    The aim of the SOFT project is to develop a new ocean forecasting system by using a combination of satellite dat, evolutionary programming and numerical ocean models. To achieve this objective two steps are proved: (1) to obtain an accurate ocean forecasting system using genetic algorithms based on satellite data; and (2) to integrate the above new system into existing deterministic numerical models. Evolutionary programming will be employed to build 'intelligent' systems that, learning form the past ocean variability and considering the present ocean state, will be able to infer near future ocean conditions. Validation of the forecast skill will be carried out by comparing the forecasts fields with satellite and in situ observations. Validation with satellite observations will provide the expected errors in the forecasting system. Validation with in situ data will indicate the capabilities of the satellite based forecast information to improve the performance of the numerical ocean models. This later validation will be accomplished considering in situ measurements in a specific oceanographic area at two different periods of time. The first set of observations will be employed to feed the hybrid systems while the second set will be used to validate the hybrid and traditional numerical model results.

  15. The Architecture of the Laser Communications Relay Demonstration Ground Stations: An Overview

    Science.gov (United States)

    Moores, John D.; Wilson, Keith E.

    2013-01-01

    NASA's Laser Communication Relay Demonstration (LCRD) will be NASA's first long-duration demonstration of laser communications (lasercom) in space, providing geosynchronous-satellite-hosted bidirectional relay services between two Earth ground stations. LCRD will leverage and enhance existing ground stations. Ground Station 1 (GS-1) will leverage the Optical Communications Telescope Laboratory (OCTL) built by JPL, while Ground Station 2 (GS-2) will leverage the Lunar Laser Communications Demonstration (LLCD) Ground Terminal (LLGT) built by MIT Lincoln Laboratory. While each ground system has unique telescopes and integrated optics, many of the backend subsystems (e.g., communications, environmental monitoring, control, user simulators) will be common to both terminals. Here we provide an overview of the architecture of the LCRD ground stations, and the planned enhancements to the existing facilities.

  16. Commercialization and Standardization Progress Towards an Optical Communications Earth Relay

    Science.gov (United States)

    Edwards, Bernard L.; Israel, David J.

    2015-01-01

    NASA is planning to launch the next generation of a space based Earth relay in 2025 to join the current Space Network, consisting of Tracking and Data Relay Satellites in space and the corresponding infrastructure on Earth. While the requirements and architecture for that relay satellite are unknown at this time, NASA is investing in communications technologies that could be deployed to provide new communications services. One of those new technologies is optical communications. The Laser Communications Relay Demonstration (LCRD) project, scheduled for launch in 2018 as a hosted payload on a commercial communications satellite, is a critical pathfinder towards NASA providing optical communications services on the next generation space based relay. This paper will describe NASA efforts in the on-going commercialization of optical communications and the development of inter-operability standards. Both are seen as critical to making optical communications a reality on future NASA science and exploration missions. Commercialization is important because NASA would like to eventually be able to simply purchase an entire optical communications terminal from a commercial provider. Inter-operability standards are needed to ensure that optical communications terminals developed by one vendor are compatible with the terminals of another. International standards in optical communications would also allow the space missions of one nation to use the infrastructure of another.

  17. The Saturn System's Icy Satellites: New Results from Cassini

    Science.gov (United States)

    Lopes-Gautier, Rosaly M.; Buratti, Bonnie; Hendrix, A. R.

    2008-01-01

    Cassini-Huygens is a multidisciplinary, international planetary mission consisting of an orbiting spacecraft and a probe. The Huygens probe successfully landed on Titan's surface on January 14, 2005, while the orbiter has performed observations of Saturn, its rings, satellites, and magnetosphere since it entered orbit around Saturn on July 1, 2004. The Cassini mission has been prolific in its scientific discoveries about the Saturn system. In this special section, we present new mission results with a focus on the 'icy satellites,' which we define as all Saturn's moons with the exception of Titan. The results included in this section have come out of the Cassini SOST--Satellites Orbiter Science Team--a multi-instrument and multidiscipline group that works together to better understand the icy satellites and their interactions with Saturn and its rings. Other papers included in this issue present ground-based observations and interior modeling of these icy moons.

  18. Cognitive Relay Networks: A Comprehensive Survey

    Directory of Open Access Journals (Sweden)

    Ayesha Naeem

    2015-07-01

    Full Text Available Cognitive radio is an emerging technology to deal with the scarcity and requirement of radio spectrum by dynamically assigning spectrum to unlicensed user . This revolutionary technology shifts the paradigm in the wireless system design by all owing unlicensed user the ability to sense, adapt and share the dynamic spectrum. Cognitive radio technology have been applied to different networks and applications ranging from wireless to public saf ety, smart grid, medical, rela y and cellular applications to increase the throughput and spectrum efficiency of the network. Among these applications, cognitive relay networks is one of the application where cognitive radio technology has been applied. Cognitiv e rela y network increases the network throughput by reducing the complete pa th loss and also by ensuring cooper ation among secondary users and cooperation among primary and secondary users. In this paper , our aim is to provide a survey on cognitive relay network. We also provide a detailed review on existing schemes in cognitive relay networks on the basis of relaying protocol, relay cooperation and channel model.

  19. Spatial Cloud Detection and Retrieval System for Satellite Images

    Directory of Open Access Journals (Sweden)

    Ayman Nasr

    2013-01-01

    Full Text Available In last the decade we witnessed a large increase in data generated by earth observing satellites. Hence, intelligent processing of the huge amount of data received by hundreds of earth receiving stations, with specific satellite image oriented approaches, presents itself as a pressing need. One of the most important steps in earlier stages of satellite image processing is cloud detection. Satellite images having a large percentage of cloud cannot be used in further analysis. While there are many approaches that deal with different semantic meaning, there are rarely approaches that deal specifically with cloud detection and retrieval. In this paper we introduce a novel approach that spatially detect and retrieve clouds in satellite images using their unique properties .Our approach is developed as spatial cloud detection and retrieval system (SCDRS that introduce a complete framework for specific semantic retrieval system. It uses a Query by polygon (QBP paradigm for the content of interest instead of using the more conventional rectangular query by image approach. First, we extract features from the satellite images using multiple tile sizes using spatial and textural properties of cloud regions. Second, we retrieve our tiles using a parametric statistical approach within a multilevel refinement process. Our approach has been experimentally validated against the conventional ones yielding enhanced precision and recall rates in the same time it gives more precise detection of cloud coverage regions.

  20. Analysis of full-duplex relay networks with opportunistic scheduling

    Directory of Open Access Journals (Sweden)

    Lei Shao

    2015-05-01

    Full Text Available This Letter addresses a two-hop decode-and-forward relay system with full-duplex relaying and opportunistic scheduling. Exact expressions for outage probability, average capacity and symbol error rate are presented in an independent identically distributed Rayleigh fading environment. Numerical and simulated results show the validity of the analytical results.

  1. 非对称双向多中继系统机会式网络编码中断概率分析%Outage Probability Analysis of Opportunistic Network Coding on Asymmetrical Bi-directional Multi-Relay System

    Institute of Scientific and Technical Information of China (English)

    梁文文; 田华; 徐友云; 许魁; 陈小杰

    2013-01-01

    A practical asymmetrical bi-directional multi-relay system model is firstly constructed, and then an outage probability expression of the model is given based on opportunistic relay scheme and network coding, which is proved accurate by Monte Carlo simulations. Secondly, it analyzes the system average outage probability with different situations of power allocation coefficient, locations of the relay nodes and the number of relay nodes, indicating the inherent relationship between power allocation coefficient and total system power, as well as the number of relay nodes. Simulation results show that the optimal system outage performance of asymmetrical bi-directional multi-relay system based on opportunistic relay scheme and network coding is attained when power allocation coefficient is chosen at 0. 6 or about 0. 6. It can be known that the location of relay nodes is an important factor for the problem of system outage probability.%建立了一个实际的非对称双向多中继系统模型,并采用机会中继策略,推导出了该模型在译码转发方式下采用网络编码时的中断概率表达式,Monte Carlo仿真和理论值吻合,充分验证了该表达式的正确性.分析了不同中继节点位置、不同中继节点个数和不同功率分配因子等情况下的系统中断性能,揭示了最优功率分配因子与中继节点个数和位置以及系统总功率的内在关系.仿真结果表明,在非对称双向多中继系统中同时采用网络编码和机会中继策略时,功率分配因子取值为0.6时可获得最佳的系统中断性能,并指出在研究系统中断概率问题时,中继节点位置是一个不可忽略的因素.

  2. Dependent surveillance through an experimental satellite data link system

    Science.gov (United States)

    Cobley, G. A.

    The development and testing of an experimental dependent aircraft-surveillance system using a satellite data link is reported. In this system, the aircraft position is determined onboard using GPS or inertial navigation, enclosed in a message block using a data-link system, and transmitted to an Inmarsat GEO communication satellites; the ground station receives and analyzes the data to keep constant track of the aircraft position. The hardware implementation and the results of demonstrations performed on flights from Iowa to Wisconsin and the North Atlantic are discussed, and diagrams and maps are provided.

  3. Radiofrequency testing of satellite segment of simulated 30/20 GHz satellite communications system

    Science.gov (United States)

    Leonard, R. F.; Kerczewski, R.

    1985-01-01

    A laboratory communications system has been developed that can serve as a test bed for the evaluation of advanced microwave (30/20 GHz) components produced under NASA technology programs. The system will ultimately permit the transmission of a stream of high-rate (220 Mbps) digital data from the originating user, through a ground terminal, through a hardware-simulated satellite, to a receiving ground station, to the receiving user. This report contains the results of radiofrequency testing of the satellite portion of that system. Data presented include output spurious responses, attainable signal-to-noise ratios, a baseline power budget, usable frequency bands, phase and amplitude response data for each of the frequency bands, and the effects of power level variation.

  4. Remote Synchronization Experiments for Quasi-Senith Satellite System Using Current Geostationary Satellites

    Directory of Open Access Journals (Sweden)

    Toshiaki Iwata

    2010-01-01

    Full Text Available The remote synchronization system for the onboard crystal oscillator (RESSOX realizes accurate synchronization between an atomic clock at a ground station and the QZSS onboard crystal oscillator, reduces overall cost and satellite power consumption, as well as onboard weight and volume, and is expected to have a longer lifetime than a system with onboard atomic clocks. Since a QZSS does not yet exist, we have been conducting synchronization experiments using geostationary earth orbit satellites (JCSAT-1B or Intelsat-4 to confirm that RESSOX is an excellent system for timing synchronization. JCSAT-1B, the elevation angle of which is 46.5 degrees at our institute, is little affected by tropospheric delay, whereas Intelsat-4, the elevation angle of which is 7.9 degrees, is significantly affected. The experimental setup and the results of uplink experiments and feedback experiments using mainly Intelsat-4 are presented. The results show that synchronization within 10 ns is realized.

  5. [Effects of nitrogen management on maize nitrogen utilization and residual nitrate nitrogen in soil under maize/soybean and maize/sweet potato relay strip intercropping systems].

    Science.gov (United States)

    Wang, Xiao-Chun; Yang, Wen-Yu; Deng, Xiao-Yan; Zhang, Qun; Yong, Tai-Wen; Liu, Wei-Guo; Yang, Feng; Mao, Shu-Ming

    2014-10-01

    A large amount of nitrogen (N) fertilizers poured into the fields severely pollute the environment. Reasonable application of N fertilizer has always been the research hotpot. The effects of N management on maize N utilization and residual nitrate N in soil under maize/soybean and maize/ sweet potato relay strip intercropping systems were reported in a field experiment in southwest China. It was found that maize N accumulation, N harvest index, N absorption efficiency, N contribution proportion after the anthesis stage in maize/soybean relay strip intercropping were increased by 6.1%, 5.4%, 4.3%, and 15.1% than under maize/sweet potato with an increase of 22.6% for maize yield after sustainable growing of maize/soybean intercropping system. Nitrate N accumulation in the 0-60 cm soil layer was 12.9% higher under maize/soybean intercropping than under maize/sweet potato intercropping. However, nitrate N concentration in the 60-120 cm soil layer when intercropped with soybean decreased by 10.3% than when intercropped with sweet potato, indicating a decrease of N leaching loss. Increasing of N application rate enhanced N accumulation of maize and decreased N use efficiency and significantly increased nitrate concentration in the soil profile except in the 60-100 cm soil layer, where no significant difference was observed with nitrogen application rate at 0 to 270 kg · hm(-2). Further application of N fertilizer significantly enhanced nitrate leaching loss. Postponing N application increased nitrate accumulation in the 60-100 cm soil layer. The results suggested that N application rates and ratio of base to top dressing had different influences on maize N concentration and nitrate N between maize/soybean and maize/sweet potato intercropping. Maize N concentration in the late growing stage, N harvest index and N use efficiency under maize/soybean intercropping increased (with N application rate at 180-270 kg · hm(-2) and ratio of base to top dressing = 3:2:5) and

  6. MaROS Strategic Relay Planning and Coordination Interfaces

    Science.gov (United States)

    Allard, Daniel A.

    2010-01-01

    The Mars Relay Operations Service (MaROS) is designed to provide planning and analysis tools in support of ongoing Mars Network relay operations. Strategic relay planning requires coordination between lander and orbiter mission ground data system (GDS) teams to schedule and execute relay communications passes. MaROS centralizes this process, correlating all data relevant to relay coordination to provide a cohesive picture of the relay state. Service users interact with the system through thin-layer command line and web user interface client applications. Users provide and utilize data such as lander view periods of orbiters, Deep Space Network (DSN) antenna tracks, and reports of relay pass performance. Users upload and download relevant relay data via formally defined and documented file structures including some described in Extensible Markup Language (XML). Clients interface with the system via an http-based Representational State Transfer (ReST) pattern using Javascript Object Notation (JSON) formats. This paper will provide a general overview of the service architecture and detail the software interfaces and considerations for interface design.

  7. MaROS Strategic Relay Planning and Coordination Interfaces

    Science.gov (United States)

    Allard, Daniel A.

    2010-01-01

    The Mars Relay Operations Service (MaROS) is designed to provide planning and analysis tools in support of ongoing Mars Network relay operations. Strategic relay planning requires coordination between lander and orbiter mission ground data system (GDS) teams to schedule and execute relay communications passes. MaROS centralizes this process, correlating all data relevant to relay coordination to provide a cohesive picture of the relay state. Service users interact with the system through thin-layer command line and web user interface client applications. Users provide and utilize data such as lander view periods of orbiters, Deep Space Network (DSN) antenna tracks, and reports of relay pass performance. Users upload and download relevant relay data via formally defined and documented file structures including some described in Extensible Markup Language (XML). Clients interface with the system via an http-based Representational State Transfer (ReST) pattern using Javascript Object Notation (JSON) formats. This paper will provide a general overview of the service architecture and detail the software interfaces and considerations for interface design.

  8. PSMG sets A and B protective relaying

    Energy Technology Data Exchange (ETDEWEB)

    Burnett, J.E.

    1978-07-24

    The ''TAN/LOFT 13.8 kV, 2.4 kV, and 480 V Relay and Circuit Breaker Coordination Study'' presented an analysis to determine overcurrent settings for the LOFT Power System protective relays including those for the drive motors of the PSMG sets. This LTR is written to form the basis of the relay settings entered in Specification ES-60238 Rev. B, for protection of the PSMG generator, primary coolant pump motor and interconnecting power cable. A momentary commercial power voltage dip occurred on January 10, 1978 which caused a trip of the PSMG field breakers. A corrective design to prevent reoccurrence is discussed and recommendations are presented.

  9. The principle of the positioning system based on communication satellites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    It is a long dream to realize the communication and navigation functionality in a satellite system in the world. This paper introduces how to establish the system, a positioning system based on communication satellites called Chinese Area Positioning System (CAPS). Instead of the typical navigation satellites, the communication satellites are configured firstly to transfer navigation signals from ground stations, and can be used to obtain service of the positioning, velocity and time, and to achieve the function of navigation and positioning. Some key technique issues should be first solved; they include the accuracy position determination and orbit prediction of the communication satellites, the measur- ing and calculation of transfer time of the signals, the carrier frequency drift in communication satellite signal transfer, how to improve the geometrical configuration of the constellation in the system, and the integration of navigation & communication. Several innovative methods are developed to make the new system have full functions of navigation and communication. Based on the development of crucial techniques and methods, the CAPS demonstration system has been designed and developed. Four communication satellites in the geosynchronous orbit (GEO) located at 87.5°E, 110.5°E, 134°E, 142°E and barometric altimetry are used in the CAPS system. The GEO satellites located at 134°E and 142°E are decommissioned GEO (DGEO) satellites. C-band is used as the navigation band. Dual frequency at C1=4143.15 MHz and C2=3826.02 MHz as well as dual codes with standard code (CA code and precision code (P code)) are adopted. The ground segment consists of five ground stations; the master station is in Lintong, Xi’an. The ground stations take a lot of responsibilities, including monitor and management of the operation of all system components, determination of the satellite position and prediction of the satellite orbit, accomplishment of the virtual atomic clock

  10. Research on Microelectromagnetic Relays

    Institute of Scientific and Technical Information of China (English)

    LI De-sheng; LIU Ben-dong

    2006-01-01

    A new microelectromagnetic relay is presented and fabricated based on micromachining technology,aiming at the miniaturization and high manufacturing efficiency of electromagnetic relays.This microrelay is composed of a lower magnetic circuit,a planar exciting coil,and an upper magnetic armature.A complete magnetic circuit is composed.and the"ON"and"OFF"states are controlled by the current of the exciting coil.The dimension Ofthis microrelay i 5 mm×5 mm×0.4 mm.The fabrication process mainly includes lithography,sputtering,electroplating,etching,sacrifice-layer technology,etc.Electromagnetic force is calculated theoretically.The calculation results are used for the optimization design of the armature and the number of tums of the exciting coil.A microelectromagnetic relay is fabricated and the initial test results are given.The resistance of the exciting coil is about 300 Ω.The switch-on state resistance is about 1.7 Ω at an exciting current of about 50 mA.

  11. Integration of satellite fire products into MPI Earth System Model

    Science.gov (United States)

    Khlystova, Iryna G.; Kloster, Silvia

    2013-04-01

    Fires are the ubiquitous phenomenon affecting all natural biomes. Since the beginning of the satellite Era, fires are being continuously observed from satellites. The most interesting satellite parameter retrieved from satellite measurements is the burned area. Combined with information on biomass available for burning the burned area can be translated into climate relevant carbon emissions from fires into the atmosphere. In this study we integrate observed burned area into a global vegetation model to derive global fire emissions. Global continuous burned area dataset is provided by the Global Fire Emissions Dataset (GFED). GFED products were obtained from MODIS (and pre-MODIS) satellites and are available for the time period of 14 years (1997-2011). This dataset is widely used, well documented and supported by periodical updates containing new features. We integrate the global burned area product into the land model JSBACH, a part of the Earth-System model developed at the Max Plank Institute for Meteorology. The land model JSBACH simulates land biomass in terms of carbon content. Fire is an important disturbance process in the Earth's carbon cycle and affects mainly the carbon stored in vegetation. In the standard JSBACH version fire is represented by process based algorithms. Using the satellite data as an alternative we are targeting better comparability of modeled carbon emissions with independent satellite measurements of atmospheric composition. The structure of burned vegetation inside of a biome can be described as the balance between woody and herbaceous vegetation. GFED provides in addition to the burned area satellite derived information of the tree cover distribution within the burned area. Using this dataset, we can attribute the burned area to the respective simulated herbaceous or woody biomass within the vegetation model. By testing several extreme cases we evaluate the quantitative impact of vegetation balance between woody and herbaceous

  12. Satellite systems for personal applications concepts and technology

    CERN Document Server

    Richharia, Madhavendra

    2010-01-01

    Presents the concepts, technology, and role of satellite systems in support of personal applications, such as mobile and broadband communications, navigation, television, radio and multimedia broadcasting, safety of life services, etc. This book presents a novel perspective on satellite systems, reflecting the modern personal technology context, and hence a focus on the individual as end-user. The book begins by outlining key generic concepts before discussing techniques adopted in particular application areas; next, it exemplifies these techniques through discussion of state-of-art c

  13. Design and characteristics of a multiband communication satellite antenna system

    Science.gov (United States)

    Ueno, Kenji; Itanami, Takao; Kumazawa, Hiroyuki; Ohtomo, Isao

    1995-04-01

    Feasibility studies on a multiband communication satellite antenna system and the key technologies involved in devising this system are described. The proposed multiband communication satellite utilizes four frequency bands: Ka (30/20 GHz), Ku (14/12 GHz), C (6/4 GHz), and S (2.6/2.5 GHz). It has six beam configurations, three multibeam and three shaped-beam. The following key technologies are presented: (1) a low-loss frequency selective subreflector (FSR) for compact feeds, (2) a low-loss and broadband frequency selective surface (FSS), and (3) a highly accurate and reliable mesh reflector.

  14. Efficient Resource Scheduling by Exploiting Relay Cache for Cellular Networks

    Directory of Open Access Journals (Sweden)

    Chun He

    2015-01-01

    Full Text Available In relay-enhanced cellular systems, throughput of User Equipment (UE is constrained by the bottleneck of the two-hop link, backhaul link (or the first hop link, and access link (the second hop link. To maximize the throughput, resource allocation should be coordinated between these two hops. A common resource scheduling algorithm, Adaptive Distributed Proportional Fair, only ensures that the throughput of the first hop is greater than or equal to that of the second hop. But it cannot guarantee a good balance of the throughput and fairness between the two hops. In this paper, we propose a Two-Hop Balanced Distributed Scheduling (TBS algorithm by exploiting relay cache for non-real-time data traffic. The evolved Node Basestation (eNB adaptively adjusts the number of Resource Blocks (RBs allocated to the backhaul link and direct links based on the cache information of relays. Each relay allocates RBs for relay UEs based on the size of the relay UE’s Transport Block. We also design a relay UE’s ACK feedback mechanism to update the data at relay cache. Simulation results show that the proposed TBS can effectively improve resource utilization and achieve a good trade-off between system throughput and fairness by balancing the throughput of backhaul and access link.

  15. Bandwidth-Efficient Cooperative Relaying Schemes with Multiantenna Relay

    Directory of Open Access Journals (Sweden)

    Tho Le-Ngoc

    2008-05-01

    Full Text Available We propose coded cooperative relaying schemes in which all successfully decoded signals from multiple sources are forwarded simultaneously by a multiantenna relay to a common multiantenna destination to increase bandwidth efficiency. These schemes facilitate various retransmission strategies at relay and single-user and multiuser iterative decoding techniques at destination, suitable for trade-offs between performance, latency, and complexity. Simulation results show that the proposed schemes significantly outperform direct transmission under the same transmit power and bandwidth efficiency.

  16. 生产管理系统在继电保护检修中的应用%Application of Production Management System in Relay Protection Maintenance

    Institute of Scientific and Technical Information of China (English)

    王伟; 陶志兴; 李延龙

    2013-01-01

    Relay protection equipment management is the core business of relay protection maintenance work. We establish module of relaying protection equipment account information management, of relaying protection service management, and of relaying protection defect management, and build improved equipment information model in relaying protection service, in order to gradually realize the whole life cycle of equipment asset management, optimize the relay protection maintenance, thus achieve the real meaning of relay protection state overhaul, realize the comprehensive, all-round, the whole process, the unity of the lean management.%继电保护设备管理是继电保护检修工作的核心业务。依靠生产管理系统建立继电保护设备台帐信息管理、继电保护检修管理及继电保护缺陷管理模块,在继电保护检修工作范围内建立完善的设备信息模型,逐步实现设备资产的全生命周期管理,优化继电保护检修,进而达到真正意义的继电保护状态检修,实现电力企业全面、全方位、全过程、精益化的统一管理。

  17. Improvement of orbit determination accuracy for Beidou Navigation Satellite System with Two-way Satellite Time Frequency Transfer

    Science.gov (United States)

    Tang, Chengpan; Hu, Xiaogong; Zhou, Shanshi; Guo, Rui; He, Feng; Liu, Li; Zhu, Lingfeng; Li, Xiaojie; Wu, Shan; Zhao, Gang; Yu, Yang; Cao, Yueling

    2016-10-01

    The Beidou Navigation Satellite System (BDS) manages to estimate simultaneously the orbits and clock offsets of navigation satellites, using code and carrier phase measurements of a regional network within China. The satellite clock offsets are also directly measured with Two-way Satellite Time Frequency Transfer (TWSTFT). Satellite laser ranging (SLR) residuals and comparisons with the precise ephemeris indicate that the radial error of GEO satellites is much larger than that of IGSO and MEO satellites and that the BDS orbit accuracy is worse than GPS. In order to improve the orbit determination accuracy for BDS, a new orbit determination strategy is proposed, in which the satellite clock measurements from TWSTFT are fixed as known values, and only the orbits of the satellites are solved. However, a constant systematic error at the nanosecond level can be found in the clock measurements, which is obtained and then corrected by differencing the clock measurements and the clock estimates from orbit determination. The effectiveness of the new strategy is verified by a GPS regional network orbit determination experiment. With the IGS final clock products fixed, the orbit determination and prediction accuracy for GPS satellites improve by more than 50% and the 12-h prediction User Range Error (URE) is better than 0.12 m. By processing a 25-day of measurement from the BDS regional network, an optimal strategy for the satellite-clock-fixed orbit determination is identified. User Equivalent Ranging Error is reduced by 27.6% for GEO satellites, but no apparent reduction is found for IGSO/MEO satellites. The SLR residuals exhibit reductions by 59% and 32% for IGSO satellites but no reductions for GEO and MEO satellites.

  18. Satellite-aided mobile radio concepts study: Concept definition of a satellite-aided mobile and personal radio communication system

    Science.gov (United States)

    Anderson, R. E.

    1979-01-01

    The satellite system requires the use of a large satellite antenna and spacecraft array power of about 12 kW or more depending on the operating frequency. Technology developments needed include large offset reflector multibeam antennas, satellite electrical power sybsystems providing greater than 12 kW of power, signal switching hardware, and linearized efficient solid state amplifiers for the satellite-aided mobile band. Presently there is no frequency assignment for this service, and it is recommended that an allocation be pursued. The satellite system appears to be within reasonable extrapolation of the state of the art. It is further recommended that the satellite-aided system spacecraft definition studies and supporting technology development be initiated.

  19. Development of a Relay Performance Web Tool for the Mars Network

    Science.gov (United States)

    Allard, Daniel A.; Edwards, Charles D.

    2009-01-01

    Modern Mars surface missions rely upon orbiting spacecraft to relay communications to and from Earth systems. An important component of this multi-mission relay process is the collection of relay performance statistics supporting strategic trend analysis and tactical anomaly identification and tracking.

  20. Opportunistic Relay Selection in Multicast Relay Networks using Compressive Sensing

    KAUST Repository

    Elkhalil, Khalil

    2014-12-01

    Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. However, for relay selection algorithms to make a selection decision, channel state information (CSI) from all cooperating relays is usually required at a central node. This requirement poses two important challenges. Firstly, CSI acquisition generates a great deal of feedback overhead (air-time) that could result in significant transmission delays. Secondly, the fed back channel information is usually corrupted by additive noise. This could lead to transmission outages if the central node selects the set of cooperating relays based on inaccurate feedback information. In this paper, we introduce a limited feedback relay selection algorithm for a multicast relay network. The proposed algorithm exploits the theory of compressive sensing to first obtain the identity of the “strong” relays with limited feedback. Following that, the CSI of the selected relays is estimated using linear minimum mean square error estimation. To minimize the effect of noise on the fed back CSI, we introduce a back-off strategy that optimally backs-off on the noisy estimated CSI. For a fixed group size, we provide closed form expressions for the scaling law of the maximum equivalent SNR for both Decode and Forward (DF) and Amplify and Forward (AF) cases. Numerical results show that the proposed algorithm drastically reduces the feedback air-time and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback channels.

  1. The principle of the positioning system based on communication satellites

    Institute of Scientific and Technical Information of China (English)

    AI GuoXiang; SHI HuLi; WU HaiTao; LI ZhiGang; GUO Ji

    2009-01-01

    It is a long dream to realize the communication and navigation functionality in a satellite system in the world.This paper introduces how to establish the system,a positioning system based on communication satellites called Chinese Area Positioning System (CAPS).Instead of the typical navigation satelIites,the communication satellites are configured firstly to transfer navigation signals from ground stations,and can be used to obtain service of the positioning,velocity and time,and to achieve the function of navigation and positioning.Some key technique issues should be first solved; they include the accuracy position determination and orbit prediction of the communication satellites,the measuring and calculation of transfer time of the signals,the carrier frequency drift in communication satellite ignal transfer,how to improve the geometrical configuration of the constellation in the system,and the integration of navigation & communication.Several innovative methods are developed to make the new system have full functions of navigation and communication.Based on the development of crucial techniques and methods,the CAPS demonstration system has been designed and developed.Four communication satellites in the geosynchronous orbit (GEO) located at 87.5°E,110.5°E,134°E,142°E and barometric altimetry are used in the CAPS system.The GEO satellites located at 134°E and 142°E re decommissioned GEO (DGEO) satellites.C-band is used as the navigation band.Dual frequency at C1=4143.15 MHz and C2=3826.02 MHz as well as dual codes with standard code (CA code and precision code (P code)) are adopted.The ground segment consists of five ground stations; the master station is in Lintong,Xi'an.The ground stations take a lot of responsibilities,including monitor and management of the operation of all system components,determination of the satellite position and prediction of the satellite orbit,accomplishment of the virtual atomic clock measurement,transmission and receiving

  2. An Orbiting Standards Platform for communication satellite system RF measurements

    Science.gov (United States)

    Wallace, R. G.; Woodruff, J. J.

    1978-01-01

    The Orbiting Standards Platform (OSP) is a proposed satellite dedicated to performing RF measurements on space communications systems. It would consist of a quasi-geostationary spacecraft containing an ensemble of calibrated RF sources and field strength meters operating in several microwave bands, and would be capable of accurately and conveniently measuring critical earth station and satellite RF performance parameters, such as EIRP, gain, figure of merit (G/T), crosspolarization, beamwidth, and sidelobe levels. The feasibility and utility of the OSP concept has been under joint study by NASA, NBS, Comsat and NTIA. A survey of potential OSP users was conducted by NTIA as part of this effort. The response to this survey, along with certain trends in satellite communications system design, indicates a growing need for such a measurement service.

  3. Optimum Overcurrent Relay Coordination of a Power Grid

    Directory of Open Access Journals (Sweden)

    Sheila Mahapatra

    2014-04-01

    Full Text Available Protective system plays a pivotal role in any power system operation. In a typical power system there are large numbers of circuit breakers and relays installed which constitute an integral part of the protective scheme. Relay is a device that senses and locates the fault and sends a command to the circuit breaker to disconnect the faulty element. Relay coordination is done to provide primary as well as back up protection from any fault that is likely to occur in the system. In this paper, overcurrent relay coordination is implemented on a 72 bus 220 KV substation. Load flow studies and the short circuit analysis on the test system is initially done followed by relay coordination. Fault current data obtained from short circuit studies enables us to obtain operating time of the relays used in the test system. The simulated value of operating time provides the coordinated operation of all the relays connected from 220kV to 33kV line thereby protecting the equipment of the test system. Keywords-

  4. Data communications method for mobile network in fourth generation communications system, involves delivering decoded data to mobile station from relay station, where mobile station receives data from both relay and base stations

    DEFF Research Database (Denmark)

    2008-01-01

    The method involves utilizing a base station (BS) (100) to transmit data to a relay station (RS) (110) and a mobile station (MS) (120), where the data includes two messages. The BS is utilized to transmit the two messages by utilizing a linear combination method, and the data is received in the RS...... and decoded. The decoded data is delivered to the MS from the RS, where the RS transmits the decoded data by utilizing another linear combination method. The MS receives data from both the BS and the RS....

  5. Testing a satellite automatic nutation control system. [on synchronous meteorological satellite

    Science.gov (United States)

    Hrasiar, J. A.

    1974-01-01

    Testing of a particular nutation control system for the synchronous meteorological satellite (SMS) is described. The test method and principles are applicable to nutation angle control for other satellites with similar requirements. During its ascent to synchronous orbit, a spacecraft like the SMS spins about its minimum-moment-of-inertia axis. An uncontrolled spacecraft in this state is unstable because torques due to fuel motion increase the nutation angle. However, the SMS is equipped with an automatic nutation control (ANC) system which will keep the nutation angle close to zero. Because correct operation of this system is critical to mission success, it was tested on an air-bearing table. The ANC system was mounted on the three-axis air-bearing table which was scaled to the SMS and equipped with appropriate sensors and thrusters. The table was spun up in an altitude chamber and nutation induced so that table motion simulated spacecraft motion. The ANC system was used to reduce the nutation angle. This dynamic test of the ANC system met all its objectives and provided confidence that the ANC system will control the SMS nutation angle.

  6. EFFECTS OF THE NUMBER OF RELAY ANTENNAS AND RELAY-POWER ON MIMO PRECODED TWO-WAY RELAYING

    Directory of Open Access Journals (Sweden)

    S.S. Rajeshwari

    2011-06-01

    Full Text Available In this treatise a two-way Amplify and Forward (AF relay-aided system is considered, which employs the so-called Arithmetic Sum of Average Bit Error Rate (ASABER based MIMO precoding technique. The two-way AF relay system is comprised of the pair of transceiver nodes S1 and S2, and the Relay Node (RN R, where each node is equipped with N1, N2 and Nr antennas, respectively. We study the effects of varying Nr for fixed values of N1 and N2, and as well as the effects of having a fixed transmission power at the RN on the achievable ASABER performance. Based on our intensive simulation campaign, we infer that the attainable diversity order is increased approximately by Nr − min (N1, N2, whenever Nr assumes a value higher than min (N1, N2 for fixed N1, N2 values. However, this is observation is only valid for relay power pr ≥ (p1, p2, where p1 and p2 are the transmit power constraints imposed on the sources S1 and S2, respectively. We also observe that the ASABER MIMO precoder’s BER curve exhibits an error floor for pr ≤ (p1, p2.

  7. Origin of the Different Architectures of the Jovian and Saturnian Satellite Systems

    OpenAIRE

    Sasaki, Takanori; Stewart, Glen R.; Ida, Shigeru

    2010-01-01

    The Jovian regular satellite system mainly consists of four Galilean satellites that have similar masses and are trapped in mutual mean motion resonances except for the outer satellite, Callisto. On the other hand, the Saturnian regular satellite system has only one big icy body, Titan, and a population of much smaller icy moons. We have investigated the origin of these major differences between the Jovian and Saturnian satellite systems by semi-analytically simulating the growth and orbital ...

  8. Multi-agent robotic systems and applications for satellite missions

    Science.gov (United States)

    Nunes, Miguel A.

    A revolution in the space sector is happening. It is expected that in the next decade there will be more satellites launched than in the previous sixty years of space exploration. Major challenges are associated with this growth of space assets such as the autonomy and management of large groups of satellites, in particular with small satellites. There are two main objectives for this work. First, a flexible and distributed software architecture is presented to expand the possibilities of spacecraft autonomy and in particular autonomous motion in attitude and position. The approach taken is based on the concept of distributed software agents, also referred to as multi-agent robotic system. Agents are defined as software programs that are social, reactive and proactive to autonomously maximize the chances of achieving the set goals. Part of the work is to demonstrate that a multi-agent robotic system is a feasible approach for different problems of autonomy such as satellite attitude determination and control and autonomous rendezvous and docking. The second main objective is to develop a method to optimize multi-satellite configurations in space, also known as satellite constellations. This automated method generates new optimal mega-constellations designs for Earth observations and fast revisit times on large ground areas. The optimal satellite constellation can be used by researchers as the baseline for new missions. The first contribution of this work is the development of a new multi-agent robotic system for distributing the attitude determination and control subsystem for HiakaSat. The multi-agent robotic system is implemented and tested on the satellite hardware-in-the-loop testbed that simulates a representative space environment. The results show that the newly proposed system for this particular case achieves an equivalent control performance when compared to the monolithic implementation. In terms on computational efficiency it is found that the multi

  9. Laser Communications Relay Demonstration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Laser Communications Relay Demonstration project will advance optical communications technology, expanding industry’s capability to produce competitive,...

  10. The international maritime satellite communications system INMARSAT (Handbook)

    Science.gov (United States)

    Zhilin, Viktor A.

    The organization and services provided by the INMARSAT satellite communications system are summarized. The structure and operation of the system are described with reference to transmission line parameters, frequency assignment, signals, telex communications, electrical parameters of communication channels, modulation, synchronization, and methods of protection against errors in the transmission of discrete messages. The discussion also covers the principal components of the INMARSAT system and the operation of ship-based stations.

  11. Demonstration of Two-Way Extremely High Frequency (EHF) Satellite Communication (SATCOM) Using Submarine-Survivable Phased Arrays

    Science.gov (United States)

    2009-01-01

    successfully using both the Military Strategic and Tactical Relay (MILSTAR) and Ultra High Frequency Follow-On ( UFO ) military satellites. The antennas...a Navy-qualified submarine FOT and High Power Amplifier (HPA) system, toward a MILSTAR or UFO EHF satellite. FULL-DUPLEX STATIC TESTING...both the K & Q band phased arrays. Both the MILSTAR and UFO satellites were used for this testing, based on availability. Using the Type 8 Mod 3

  12. A Fault tolerant Control Supervisory System development Procedurefor Small Satellites

    DEFF Research Database (Denmark)

    Izadi-Zamanabadi, Roozbeh; Larsen, Jesper Abildgaard

    The paper presents a stepwise procedure to develop a fault tolerant control system for small satellites. The procedure is illustrated through implementation on the AAUSAT-II spacecraft. As it is shown the presented procedure requires expertise from several disciplines that are nevertheless...

  13. Internal Calibration of HJ-1-C Satellite SAR System

    Directory of Open Access Journals (Sweden)

    Yang Zhen

    2014-06-01

    Full Text Available The HJ-1-C satellite is a Synthetic Aperture Radar (SAR satellite of a small constellation for environmental and disaster monitoring. At present, it is in orbit and working well. The SAR system uses a mesh reflector antenna and centralized power amplifier, and has an internal calibration function in orbit. This study introduces the internal calibration modes and signal paths. The design and realization of the internal calibrator are discussed in detail. Finally, the internal calibration data acquired in orbit are also analyzed.

  14. Multi-spectral band selection for satellite-based systems

    Energy Technology Data Exchange (ETDEWEB)

    Clodius, W.B.; Weber, P.G.; Borel, C.C.; Smith, B.W.

    1998-09-01

    The design of satellite based multispectral imaging systems requires the consideration of a number of tradeoffs between cost and performance. The authors have recently been involved in the design and evaluation of a satellite based multispectral sensor operating from the visible through the long wavelength IR. The criteria that led to some of the proposed designs and the modeling used to evaluate and fine tune the designs will both be discussed. These criteria emphasized the use of bands for surface temperature retrieval and the correction of atmospheric effects. The impact of cost estimate changes on the final design will also be discussed.

  15. An interactive system for compositing digital radar and satellite data

    Science.gov (United States)

    Heymsfield, G. M.; Ghosh, K. K.; Chen, L. C.

    1983-01-01

    This paper describes an approach for compositing digital radar data and GOES satellite data for meteorological analysis. The processing is performed on a user-oriented image processing system, and is designed to be used in the research mode. It has a capability to construct PPIs and three-dimensional CAPPIs using conventional as well as Doppler data, and to composite other types of data. In the remapping of radar data to satellite coordinates, two steps are necessary. First, PPI or CAPPI images are remapped onto a latitude-longitude projection. Then, the radar data are projected into satellite coordinates. The exact spherical trigonometric equations, and the approximations derived for simplifying the computations are given. The use of these approximations appears justified for most meteorological applications. The largest errors in the remapping procedure result from the satellite viewing angle parallax, which varies according to the cloud top height. The horizontal positional error due to this is of the order of the error in the assumed cloud height in mid-latitudes. Examples of PPI and CAPPI data composited with satellite data are given for Hurricane Frederic on 13 September 1979 and for a squall line on 2 May 1979 in Oklahoma.

  16. Sensor system for Greenhouse Gas Observing Satellite (GOSAT)

    Science.gov (United States)

    Hamazaki, Takashi; Kuze, Akihiko; Kondo, Kayoko

    2004-11-01

    Global warming has become a very serious issue for human beings. In 1997, the Kyoto Protocol was adopted at the Third Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP3), making it mandatory for developed nations to reduce carbon dioxide emissions by six (6) to eight (8) per cent of their total emissions in 1990, and to meet this goal sometime between 2008 and 2012. The Greenhouse gases Observing SATellite (GOSAT) is design to monitor the global distribution of carbon dioxide (CO2) from orbit. GOSAT is a joint project of Japan Aerospace Exploration Agency (JAXA), the Ministry of Environment (MOE), and the National Institute for Environmental Studies (NIES). JAXA is responsible for the satellite and instrument development, MOE is involved in the instrument development, and NIES is responsible for the satellite data retrieval. The satellite is scheduled to be launched in 2008. In order to detect the CO2 variation of boundary layers, both the technique to measure the column density and the retrieval algorithm to remove cloud and aerosol contamination are investigated. Main mission sensor of the GOSAT is a Fourier Transform Spectrometer with high optical throughput, spectral resolution and wide spectral coverage, and a cloud-aerosol detecting imager attached to the satellite. The paper presents the mission sensor system of the GOSAT together with the results of performance demonstration with proto-type instrument aboard an aircraft.

  17. Accuracy Performance Evaluation of Beidou Navigation Satellite System

    Science.gov (United States)

    Wang, W.; Hu, Y. N.

    2017-03-01

    Accuracy is one of the key elements of the regional Beidou Navigation Satellite System (BDS) performance standard. In this paper, we review the definition specification and evaluation standard of the BDS accuracy. Current accuracy of the regional BDS is analyzed through the ground measurements and compared with GPS in terms of dilution of precision (DOP), signal-in-space user range error (SIS URE), and positioning accuracy. The Positioning DOP (PDOP) map of BDS around Chinese mainland is compared with that of GPS. The GPS PDOP is between 1.0-2.0 and does not vary with the user latitude and longitude, while the BDS PDOP varies between 1.5-5.0, and increases as the user latitude increases, and as the user longitude apart from 118°. The accuracies of the broadcast orbits of BDS are assessed by taking the precise orbits from International GNSS Service (IGS) as the reference, and by making satellite laser ranging (SLR) residuals. The radial errors of the BDS inclined geosynchronous orbit (IGSO) and medium orbit (MEO) satellites broadcast orbits are at the 0.5m level, which are larger than those of GPS satellites at the 0.2m level. The SLR residuals of geosynchronous orbit (GEO) satellites are 65.0cm, which are larger than those of IGSO, and MEO satellites, at the 50.0cm level. The accuracy of broadcast clock offset parameters of BDS is computed by taking the clock measurements of Two-way Satellite Radio Time Frequency Transfer as the reference. Affected by the age of broadcast clock parameters, the error of the broadcast clock offset parameters of the MEO satellites is the largest, at the 0.80m level. Finally, measurements of the multi-GNSS (MGEX) receivers are used for positioning accuracy assessment of BDS and GPS. It is concluded that the positioning accuracy of regional BDS is better than 10m at the horizontal component and the vertical component. The combined positioning accuracy of both systems is better than one specific system.

  18. A satellite-tracking millimeter-wave reflector antenna system for mobile satellite-tracking

    Science.gov (United States)

    Densmore, Arthur C. (Inventor); Jamnejad, Vahraz (Inventor); Woo, Kenneth E. (Inventor)

    1995-01-01

    A miniature dual-band two-way mobile satellite tracking antenna system mounted on a movable ground vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

  19. Satellite-Tracking Millimeter-Wave Reflector Antenna System For Mobile Satellite-Tracking

    Science.gov (United States)

    Densmore, Arthur C. (Inventor); Jamnejad, Vahraz (Inventor); Woo, Kenneth E. (Inventor)

    2001-01-01

    A miniature dual-band two-way mobile satellite-tracking antenna system mounted on a movable vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

  20. Cyber security with radio frequency interferences mitigation study for satellite systems

    Science.gov (United States)

    Wang, Gang; Wei, Sixiao; Chen, Genshe; Tian, Xin; Shen, Dan; Pham, Khanh; Nguyen, Tien M.; Blasch, Erik

    2016-05-01

    Satellite systems including the Global Navigation Satellite System (GNSS) and the satellite communications (SATCOM) system provide great convenience and utility to human life including emergency response, wide area efficient communications, and effective transportation. Elements of satellite systems incorporate technologies such as navigation with the global positioning system (GPS), satellite digital video broadcasting, and information transmission with a very small aperture terminal (VSAT), etc. The satellite systems importance is growing in prominence with end users' requirement for globally high data rate transmissions; the cost reduction of launching satellites; development of smaller sized satellites including cubesat, nanosat, picosat, and femtosat; and integrating internet services with satellite networks. However, with the promising benefits, challenges remain to fully develop secure and robust satellite systems with pervasive computing and communications. In this paper, we investigate both cyber security and radio frequency (RF) interferences mitigation for satellite systems, and demonstrate that they are not isolated. The action space for both cyber security and RF interferences are firstly summarized for satellite systems, based on which the mitigation schemes for both cyber security and RF interferences are given. A multi-layered satellite systems structure is provided with cross-layer design considering multi-path routing and channel coding, to provide great security and diversity gains for secure and robust satellite systems.

  1. Mobile satellite news gathering (SNG) system; Soko SNG (Satellite News Gathering) shasaikyoku

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Commercialization was made for broadcasting stations on a mobile station system capable of capturing a satellite automatically while the system is moving. Its feature is the enhanced tracking accuracy as a result of using the Company's original null-sensor (see Note), and detecting and controlling intersecting polarized waves of reference signals from the satellite. The material for transmission is digitally transmitted by MPEG2, making it possible to transmit more data than by conventional systems. The system is being used for live broadcasting of marathon races and emergency news broadcasting. It is expected that the system may be applied to applications other than broadcasting stations, such as automobiles and ships. (Note: A null-sensor is a unit used for adjusting antenna directions for an SNG transmitter. It uses IF receiving signals of H/V polarized waves of parabolic antenna as an input, and outputs the main polarized wave level and the intersecting polarized wave level.) (translated by NEDO)

  2. Satellite Power Systems (SPS) concept definition study. Volume 5: Special emphasis studies. [rectenna and solar power satellite design studies

    Science.gov (United States)

    Hanley, G. M.

    1980-01-01

    Satellite configurations based on the Satellite Power System baseline requirements were analyzed and a preferred concept selected. A satellite construction base was defined, precursor operations incident to establishment of orbital support facilities identified, and the satellite construction sequence and procedures developed. Rectenna construction requirement were also addressed. Mass flow to orbit requirements were revised and traffic models established based on construction of 60 instead of 120 satellites. Analyses were conducted to determine satellite control, resources, manufacturing, and propellant requirements. The impact of the laser beam used for space-to-Earth power transmission upon the intervening atmosphere was examined as well as the inverse effect. The significant space environments and their effects on spacecraft components were investigated to define the design and operational limits imposed by the environments on an orbit transfer vehicle. The results show that LEO altitude 300 nmi and transfer orbit duration 6 months are preferrable.

  3. CERN Relay Race

    CERN Multimedia

    Running Club

    2010-01-01

    This year’s CERN Relay Race will take place around the Meyrin site on Thursday 20th May at 12h00. This annual event is for teams of 6 runners covering distances of 1000m, 800m, 800m, 500m, 500m and 300m respectively. Teams may be entered in the Seniors, Veterans, Ladies, Mixed or Open categories. The registration fee is 10 CHF per runner, and each runner receives a souvenir prize. As usual, there will be a programme of entertainments from 12h in the arrival area, in front of the Restaurant no. 1. Drinks, food, CERN club information and music will be available for the pleasure of both runners and spectators. The race starts at 12h15, with results and prize giving at 13:15.   For details of the race, and of how to sign up a team, please visit: https://espace.cern.ch/Running-Club/CERN-Relay The event is organised by the CERN Running Club with the support of the CERN Staff Association.  

  4. 47th Relay Race!

    CERN Multimedia

    Staff Association

    2017-01-01

    On Thursday June 1st at 12.15, Fabiola Gianotti, our Director-General, will fire the starting shot for the 47th Relay Race. This Race is above all a festive CERN event, open for runners and walkers, as well as the people cheering them on throughout the race, and those who wish to participate in the various activities organised between 11.30 and 14.30 out on the lawn in front of Restaurant 1. In order to make this sports event accessible for everyone, our Director-General will allow for flexible lunch hours on the day, applicable for all the members of personnel. An alert for the closure of roads will be send out on the day of the event. The Staff Association and the CERN Running Club thank you in advance for your participation and your continued support throughout the years. This year the CERN Running Club has announced the participation of locally and internationally renowned runners, no less! A bit over a week from the Relay Race of 1st June, the number of teams is going up nicely (already almost 40). Am...

  5. Asymptotic analysis for Nakagami-m fading channels with relay selection

    KAUST Repository

    Zhong, Caijun

    2011-06-01

    In this paper, we analyze the asymptotic outage probability performance of both decode-and-forward (DF) and amplify-and-forward (AF) relaying systems using partial relay selection and the "best" relay selection schemes for Nakagami-m fading channels. We derive their respective outage probability expressions in the asymptotic high signal-to-noise ratio (SNR) regime, from which the diversity order and coding gain are analyzed. In addition, we investigate the impact of power allocation between the source and relay terminals and derive the diversity-multiplexing tradeoff (DMT) for these relay selection systems. The theoretical findings suggest that partial relay selection can improve the diversity of the system and can achieve the same DMT as the "best" relay selection scheme under certain conditions. © 2011 IEEE.

  6. The MUSES Satellite Team and Multidisciplinary System Engineering

    Science.gov (United States)

    Chen, John C.; Paiz, Alfred R.; Young, Donald L.

    1997-01-01

    In a unique partnership between three minority-serving institutions and NASA's Jet Propulsion Laboratory, a new course sequence, including a multidisciplinary capstone design experience, is to be developed and implemented at each of the schools with the ambitious goal of designing, constructing and launching a low-orbit Earth-resources satellite. The three universities involved are North Carolina A&T State University (NCA&T), University of Texas, El Paso (UTEP), and California State University, Los Angeles (CSULA). The schools form a consortium collectively known as MUSES - Minority Universities System Engineering and Satellite. Four aspects of this project make it unique: (1) Including all engineering disciplines in the capstone design course, (2) designing, building and launching an Earth-resources satellite, (3) sustaining the partnership between the three schools to achieve this goal, and (4) implementing systems engineering pedagogy at each of the three schools. This paper will describe the partnership and its goals, the first design of the satellite, the courses developed at NCA&T, and the implementation plan for the course sequence.

  7. Satellite Imagery Assisted Road-Based Visual Navigation System

    Science.gov (United States)

    Volkova, A.; Gibbens, P. W.

    2016-06-01

    There is a growing demand for unmanned aerial systems as autonomous surveillance, exploration and remote sensing solutions. Among the key concerns for robust operation of these systems is the need to reliably navigate the environment without reliance on global navigation satellite system (GNSS). This is of particular concern in Defence circles, but is also a major safety issue for commercial operations. In these circumstances, the aircraft needs to navigate relying only on information from on-board passive sensors such as digital cameras. An autonomous feature-based visual system presented in this work offers a novel integral approach to the modelling and registration of visual features that responds to the specific needs of the navigation system. It detects visual features from Google Earth* build a feature database. The same algorithm then detects features in an on-board cameras video stream. On one level this serves to localise the vehicle relative to the environment using Simultaneous Localisation and Mapping (SLAM). On a second level it correlates them with the database to localise the vehicle with respect to the inertial frame. The performance of the presented visual navigation system was compared using the satellite imagery from different years. Based on comparison results, an analysis of the effects of seasonal, structural and qualitative changes of the imagery source on the performance of the navigation algorithm is presented. * The algorithm is independent of the source of satellite imagery and another provider can be used

  8. Interoperability of satellite-based augmentation systems for aircraft navigation

    Science.gov (United States)

    Dai, Donghai

    The Federal Aviation Administration (FAA) is pioneering a transformation of the national airspace system from its present ground based navigation and landing systems to a satellite based system using the Global Positioning System (GPS). To meet the critical safety-of-life aviation positioning requirements, a Satellite-Based Augmentation System (SBAS), the Wide Area Augmentation System (WAAS), is being implemented to support navigation for all phases of flight, including Category I precision approach. The system is designed to be used as a primary means of navigation, capable of meeting the Required Navigation Performance (RNP), and therefore must satisfy the accuracy, integrity, continuity and availability requirements. In recent years there has been international acceptance of Global Navigation Satellite Systems (GNSS), spurring widespread growth in the independent development of SBASs. Besides the FAA's WAAS, the European Geostationary Navigation Overlay Service System (EGNOS) and the Japan Civil Aviation Bureau's MTSAT-Satellite Augmentation System (MSAS) are also being actively developed. Although all of these SBASs can operate as stand-alone, regional systems, there is increasing interest in linking these SBASs together to reduce costs while improving service coverage. This research investigated the coverage and availability improvements due to cooperative efforts among regional SBAS networks. The primary goal was to identify the optimal interoperation strategies in terms of performance, complexity and practicality. The core algorithms associated with the most promising concepts were developed and demonstrated. Experimental verification of the most promising concepts was conducted using data collected from a joint international test between the National Satellite Test Bed (NSTB) and the EGNOS System Test Bed (ESTB). This research clearly shows that a simple switch between SBASs made by the airborne equipment is the most effective choice for achieving the

  9. Automatic charge control system for satellites

    Science.gov (United States)

    Shuman, B. M.; Cohen, H. A.

    1985-01-01

    The SCATHA and the ATS-5 and 6 spacecraft provided insights to the problem of spacecraft charging at geosychronous altitudes. Reduction of the levels of both absolute and differential charging was indicated, by the emission of low energy neutral plasma. It is appropriate to complete the transition from experimental results to the development of a system that will sense the state-of-charge of a spacecraft, and, when a predetermined threshold is reached, will respond automatically to reduce it. A development program was initiated utilizing sensors comparable to the proton electrostatic analyzer, the surface potential monitor, and the transient pulse monitor that flew in SCATHA, and combine these outputs through a microprocessor controller to operate a rapid-start, low energy plasma source.

  10. A Reusable Software Architecture for Small Satellite AOCS Systems

    DEFF Research Database (Denmark)

    Alminde, Lars; Bendtsen, Jan Dimon; Laursen, Karl Kaas

    2006-01-01

    with both hardware and on-board software. Some of the key issues addressed by the framework are automatic translation of mathematical specifications of hybrid systems into executable software entities, management of execution of coupled models in a parallel distributed environment, as well as interaction......This paper concerns the software architecture called Sophy, which is an abbreviation for Simulation, Observation, and Planning in HYbrid systems. We present a framework that allows execution of hybrid dynamical systems in an on-line distributed computing environment, which includes interaction...... with external components, hardware and/or software, through generic interfaces. Sophy is primarily intended as a tool for development of model based reusable software for the control and autonomous functions of satellites and/or satellite clusters....

  11. Gravimetry, Relativity, and the Global Navigation Satellite Systems

    CERN Document Server

    Tarantola, Albert; Pozo, Jose Maria; Coll, Bartolome

    2009-01-01

    Relativity is an integral part of positioning systems, and this is taken into account in today's practice by applying many "relativistic corrections" to computations performed using concepts borrowed from Galilean physics. A different, fully relativistic paradigm can be developed for operating a positioning system. This implies some fundamental changes. For instance, the basic coordinates are four times (with a symmetric meaning, not three space coordinate and one time coordinate) and the satellites must have cross-link capabilities. Gravitation must, of course, be taken into account, but not using the Newtonian theory: the gravitation field is, and only is, the space-time metric. This implies that the positioning problem and the gravimetry problem can not be separated. An optimization theory can be developed that, because it is fully relativistic, does not contain any "relativistic correction". We suggest that all positioning satellite systems should be operated in this way. The first benefit of doing so wou...

  12. Analysis of satellite broadcasting systems for digital television

    Science.gov (United States)

    de Gaudenzi, Riccardo; Elia, Carlo; Viola, Roberto

    1993-01-01

    This paper introduces the new concept of digital direct satellite broadcasting (D-DBS), which allows unprecedented flexibility by providing a large number of audio-visual services. The concept elaborated on in this paper assumes an information rate of about 40 Mb/s, which is compatible with practically all present-day transponders. After discussion of the general system concept, the optimization procedure is introduced and results of the transmission system optimization are presented. Channel distortion and uplink/downlink interference effects are taken into account by means of a time domain system computer simulation approach. It is shown, by means of link budget analysis, how a medium power direct-to-home TV satellite can provide multimedia services to users equipped with small (60 cm) dish antennas.

  13. An active attitude control system for a drag sail satellite

    Science.gov (United States)

    Steyn, Willem Herman; Jordaan, Hendrik Willem

    2016-11-01

    The paper describes the development and simulation results of a full ADCS subsystem for the deOrbitSail drag sail mission. The deOrbitSail satellite was developed as part of an European FP7 collaboration research project. The satellite was launched and commissioning started on 10th July 2015. Various new actuators and sensors designed for this mission will be presented. The deOrbitSail satellite is a 3U CubeSat to deploy a 4 by 4 m drag sail from an initial 650 km circular polar low earth orbit. With an active attitude control system it will be shown that by maximising the drag force, the expected de-orbiting period from the initial altitude will be less than 50 days. A future application of this technology will be the use of small drag sails as low-cost devices to de-orbit LEO satellites, when they have reached their end of life, without having to use expensive propulsion systems. Simulation and Hardware-in-Loop experiments proved the feasibility of the proposed attitude control system. A magnetic-only control approach using a Y-Thomson spin, is used to detumble the 3U Cubesat with stowed sail and subsequently to 3-axis stabilise the satellite to be ready for the final deployment phase. Minituarised torquer rods, a nano-sized momentum wheel, attitude sensor hardware (magnetometer, sun, earth) developed for this phase will be presented. The final phase will be to deploy and 3-axis stabilise the drag sail normal to the satellite's velocity vector, using a combined Y-momentum wheel and magnetic controller. The design and performance improvements when using a 2-axis translation stage to adjust the sail centre-of-pressure to satellite centre-of-mass offset, will also be discussed, although for launch risk reasons this stage was not included in the final flight configuration. To accurately determine the drag sail's attitude during the sunlit part of the orbit, an accurate wide field of view dual sensor to measure both the sun and nadir vector direction was developed for

  14. Multistage Relaying Using Interference Networks

    CERN Document Server

    Muthuramalingam, Bama; Thangaraj, Andrew

    2010-01-01

    Wireless networks with multiple nodes that relay information from a source to a destination are expected to be deployed in many applications. Therefore, understanding their design and performance under practical constraints is important. In this work, we propose and study three multihopping decode and forward (MDF) protocols for multistage half-duplex relay networks with no direct link between the source and destination nodes. In all three protocols, we assume no cooperation across relay nodes for encoding and decoding. Numerical evaluation in illustrative example networks and comparison with cheap relay cut-set bounds for half-duplex networks show that the proposed MDF protocols approach capacity in some ranges of channel gains. The main idea in the design of the protocols is the use of coding in interference networks that are created in different states or modes of a half-duplex network. Our results suggest that multistage half-duplex relaying with practical constraints on cooperation is comparable to point...

  15. Space Weathering on Icy Satellites in the Outer Solar System

    Science.gov (United States)

    Clark, R. N.; Perlman, Z.; Pearson, N.; Cruikshank, D. P.

    2014-01-01

    Space weathering produces well-known optical effects in silicate minerals in the inner Solar System, for example, on the Moon. Space weathering from solar wind and UV (ultraviolet radiation) is expected to be significantly weaker in the outer Solar System simply because intensities are low. However, cosmic rays and micrometeoroid bombardment would be similar to first order. That, combined with the much higher volatility of icy surfaces means there is the potential for space weathering on icy outer Solar System surfaces to show optical effects. The Cassini spacecraft orbiting Saturn is providing evidence for space weathering on icy bodies. The Cassini Visible and Infrared Mapping Spectrometer (VIMS) instrument has spatially mapped satellite surfaces and the rings from 0.35-5 microns and the Ultraviolet Imaging Spectrograph (UVIS) instrument from 0.1 to 0.2 microns. These data have sampled a complex mixing space between H2O ice and non-ice components and they show some common spectral properties. Similarly, spectra of the icy Galilean satellites and satellites in the Uranian system have some commonality in spectral properties with those in the Saturn system. The UV absorber is spectrally similar on many surfaces. VIMS has identified CO2, H2 and trace organics in varying abundances on Saturn's satellites. We postulate that through the spatial relationships of some of these compounds that they are created and destroyed through space weathering effects. For example, the trapped H2 and CO2 observed by VIMS in regions with high concentrations of dark material may in part be space weathering products from the destruction of H2O and organic molecules. The dark material, particularly on Iapetus which has the highest concentration in the Saturn system, is well matched by space-weathered silicates in the .4 to 2.6 micron range, and the spectral shapes closely match those of the most mature lunar soils, another indicator of space weathered material.

  16. The European Satellite Navigation System Galileo

    Institute of Scientific and Technical Information of China (English)

    G.W. Hein; T. Pany

    2003-01-01

    This paper starts with a brief discussion of the Galileo project status and with a description of the present Galileo architecture (space segment, ground segment, user segment). It focuses on explaining special features compared to the American GPS system. The presentation of the user segment comprises a discussion of the actual Galileo signal structure. The Galileo carrier frequency, modulation scheme and data rate of all 10 navigation signals are described as well as parameters of the search and rescue service. The navigation signals are used to realize three types of open services, the safety of life service, two types of commercial services and the public regulated service. The signal performance in terms of the pseudorange code error due to thermal noise and multipath is discussed as well as interference to and from other radionavigation services broadcasting in the E5 and E6 frequency band. The interoperability and compatibility of Galileo and GPS is realized by a properly chosen signal structures in E5a/L5 and E2-L1-E1 and compatible geodetic and time reference frames. Some new results on reciprocal GPS/Galileo signal degradation due to signal overlay are presented as well as basic requirements on the Galileo code sequences.

  17. Autonomous Attitude Determination and Control System for the Ørsted Satellite

    DEFF Research Database (Denmark)

    Bak, Thomas; Wisniewski, Rafal; Blanke, M.

    1996-01-01

    The Ørsted Satellite mission imposes comparatively high requirements on autonomy of the attitude control system.......The Ørsted Satellite mission imposes comparatively high requirements on autonomy of the attitude control system....

  18. Personal Access Satellite System (PASS) study. Fiscal year 1989 results

    Science.gov (United States)

    Sue, Miles K. (Editor)

    1990-01-01

    The Jet Propulsion Laboratory is exploring the potential and feasibility of a personal access satellite system (PASS) that will offer the user greater freedom and mobility than existing or currently planned communications systems. Studies performed in prior years resulted in a strawman design and the identification of technologies that are critical to the successful implementation of PASS. The study efforts in FY-89 were directed towards alternative design options with the objective of either improving the system performance or alleviating the constraints on the user terminal. The various design options and system issues studied this year and the results of the study are presented.

  19. Advanced Microelectronics Technologies for Future Small Satellite Systems

    Science.gov (United States)

    Alkalai, Leon

    1999-01-01

    Future small satellite systems for both Earth observation as well as deep-space exploration are greatly enabled by the technological advances in deep sub-micron microelectronics technologies. Whereas these technological advances are being fueled by the commercial (non-space) industries, more recently there has been an exciting new synergism evolving between the two otherwise disjointed markets. In other words, both the commercial and space industries are enabled by advances in low-power, highly integrated, miniaturized (low-volume), lightweight, and reliable real-time embedded systems. Recent announcements by commercial semiconductor manufacturers to introduce Silicon On Insulator (SOI) technology into their commercial product lines is driven by the need for high-performance low-power integrated devices. Moreover, SOI has been the technology of choice for many space semiconductor manufacturers where radiation requirements are critical. This technology has inherent radiation latch-up immunity built into the process, which makes it very attractive to space applications. In this paper, we describe the advanced microelectronics and avionics technologies under development by NASA's Deep Space Systems Technology Program (also known as X2000). These technologies are of significant benefit to both the commercial satellite as well as the deep-space and Earth orbiting science missions. Such a synergistic technology roadmap may truly enable quick turn-around, low-cost, and highly capable small satellite systems for both Earth observation as well as deep-space missions.

  20. Satellite Power Systems (SPS) concept definition study. Volume 4: SPS point design definition

    Science.gov (United States)

    Hanley, G.

    1978-01-01

    The satellite power systems point design concept is described. The concept definition includes satellite, ground and space systems, and their relationships. Emphasis is placed on the definition of the GaAlAs photovoltaic satellite system. The major subsystems of the satellite system including power conversion, power distribution and control, microwave, attitude control and stationkeeping, thermal control, structures, and information management and control are discussed.

  1. CERN Relay Race

    CERN Document Server

    2005-01-01

    The CERN Relay Race will take place around the Meyrin site on Wednesday 18 May between 12.15 and 12.35. This year, weather permitting, there will be some new attractions in the start/finish area on the field behind the Main Building. You will be able to: listen to music played by the CERN Jazz Club; buy drinks at the bar organised by the CERN Running Club; buy lunch served directly on the terrace by the restaurant Novae. ATTENTION: concerning traffic, the recommendations are the same as always: If possible, please avoid driving on the site during this 20 minute period. If you do meet runners in your car, please STOP until they all have passed. Thank you for your understanding.

  2. Concept of an Effective Sentinel-1 Satellite SAR Interferometry System

    OpenAIRE

    2016-01-01

    This brief study introduces a partially working concept being developed at IT4Innovations supercomputer (HPC) facility. This concept consists of several modules that form a whole body of an efficient system for observation of terrain or objects displacements using satellite SAR interferometry (InSAR). A metadata database helps to locate data stored in various storages and to perform basic analyzes. A special database has been designed to describe Sentinel-1 data, on its burst level. Custom Se...

  3. System analysis for millimeter-wave communication satellites

    Science.gov (United States)

    Holland, L. D.; Hilsen, N. B.; Gallagher, J. J.; Stevens, G.

    1980-01-01

    Research and development needs for millimeter-wave space communication systems are presented. Assumed propagation fade statistics are investigated along with high data rate diversity link and storage. The development of reliable ferrite switches, and high performance receivers and transmitters is discussed, in addition to improved tolerance of dish and lens fabrication for the antennas. The typical cost for using a simplex voice channel via a high capacity 40/50 GHz satellite is presented.

  4. Management approach recommendations. Earth Observatory Satellite system definition study (EOS)

    Science.gov (United States)

    1974-01-01

    Management analyses and tradeoffs were performed to determine the most cost effective management approach for the Earth Observatory Satellite (EOS) Phase C/D. The basic objectives of the management approach are identified. Some of the subjects considered are as follows: (1) contract startup phase, (2) project management control system, (3) configuration management, (4) quality control and reliability engineering requirements, and (5) the parts procurement program.

  5. NFCGate - An NFC Relay Application for Android

    OpenAIRE

    Maaß, Max Jakob; Müller, Uwe; Schons, Tom; Wegemer, Daniel; Schulz, Matthias

    2015-01-01

    Near Field Communication (NFC) is a technology widely used for security-critical applications like access control or payment systems. Many of these systems rely on the security assumption that the card has to be in close proximity to communicate with the reader. We developed NFCGate, an Android application capable of relaying NFC communication between card and reader using two rooted but otherwise unmodified Android phones. This enables us to increase the distance between card and reader, eav...

  6. 77 FR 58579 - Certain Two-Way Global Satellite Communication Devices, System and Components Thereof...

    Science.gov (United States)

    2012-09-21

    ... COMMISSION Certain Two-Way Global Satellite Communication Devices, System and Components Thereof; Institution...-way global satellite communication devices, system and components thereof by reason of infringement of... after importation of certain two-way global satellite communication devices, system and components...

  7. 78 FR 31576 - Enforcement Proceeding; Certain Two-Way Global Satellite Communication Devices, System and...

    Science.gov (United States)

    2013-05-24

    ... Proceeding; Certain Two-Way Global Satellite Communication Devices, System and Components Thereof; Notice of... United States after importation of certain two-way global satellite communication devices, system and... States after importation any two-way global satellite communication devices, system, and components...

  8. Two-hop Secure Communication Using an Untrusted Relay

    CERN Document Server

    He, Xiang

    2009-01-01

    We consider a source-destination pair that can only communicate through an untrusted intermediate relay node. The intermediate node is willing to employ a designated relaying scheme to facilitate reliable communication between the source and the destination. Yet, the information it relays needs to be kept secret from it. In this two-hop communication scenario, where the use of the untrusted relay node is essential, we find that a positive secrecy rate is achievable. The center piece of the achievability scheme is the help provided by either the destination node with transmission capability, or an external "good samaritan" node. In either case, the helper performs cooperative jamming that confuses the eavesdropping relay and disables it from being able to decipher what it is relaying. We next derive an upper bound on the secrecy rate for this system. We observe that the gap between the upper bound and the achievable rate vanishes as the power of the relay node goes to infinity. Overall, the paper presents a ca...

  9. A preliminary design for a satellite power system

    Science.gov (United States)

    Enriquez, Clara V.; Kokaly, Ray; Nandi, Saumya; Timmons, Mike; Garrard, Mark; Mercado, Rommel; Rogers, Brian; Ugaz, Victor

    1991-01-01

    Outlined here is a preliminary design for a Solar Power Satellite (SPS) system. The SPS will provide a clean, reliable source of energy for mass consumption. The system will use satellites in geostationary orbits around the Earth to capture the sun's energy. The intercepted sunlight will be converted to laser beam energy which can be transmitted to the Earth's surface. Ground systems on the Earth will convert the transmissions from space into electric power. The preliminary design for the SPS consists of one satellite in orbit around the Earth transmitting to one ground station. The SPs technology uses multi-layer solar cell technology arranged on a 20 sq km planar array to intercept sunlight and convert it to an electric voltage. Power conditioning devices then send the electricity to a laser, which transmits the power to the surface of the Earth. A ground station will convert the beam into electricity. Construction will take place in low Earth orbit and array sections, 20 in total, will be sailed on the solar wind out to the GEO location in 150 days. These individual transportation sections are referred to as solar sailing panels (SSAPs). The primary truss elements used to support the arrays are composed on composite tubular members in a pentahedral arrangement. Smart segments consisting of passive and active damping devices will increase the control of dynamic SPS modes.

  10. 继电保护故障信息系统智能分析研究%A Research on Intelligent Analysis for Relay Protection Fault Information System

    Institute of Scientific and Technical Information of China (English)

    李七鑫; 续建国

    2015-01-01

    设计了继电保护故障信息系统主站智能分析功能,开发双端测距程序,提高故障测距精度;依据电网故障时故障信息主站收集到的站端设备上送到主站系统的故障信息,基于模拟量、开关量和装置报文等多元信息形成一个全面的保护动作综合分析报告,为调度员快速判断电网故障情况,做出正确的调度决策提供技术支持。%This paper introduces intelligent analysis of the system for relay protection fault information, which helps to develop the programme of double terminal fault location and improve the accuracy of fault location. When there is something wrong with the power grid , the system will collect the fault information sent from station terminal equipment to the master. Meanwhile, based on the multi-information such as analog quantity, switching quantity and device message, it automatically generate an analysis report. The report provides the technical support so that the dispatcher can in no time judge where the power grid fault is and take appropriate measures.

  11. Present and Future Trends in Military Satellite Communication Systems

    Directory of Open Access Journals (Sweden)

    C.K. Chatterjee

    1993-01-01

    Full Text Available Recent years have seen a phenomenal growth in the field of satellite communications. Satcom systems offer many advantages for military applications which include wide area coverage, rapid deployment, flexible networking and long range service to moving platforms like ships, aircraft and vehicles. This paper gives an overview of the special features and future trends in military satcom systems. A brief account of various countermeasures against threats, use of EHF, spread-spectrum techniques and on board processing has also been given. Major technological advances are anticipated in near future to realise high capacity, secure and survivable satcom systems for Defence applications.

  12. Global navigation satellite systems, inertial navigation, and integration

    CERN Document Server

    Grewal, Mohinder S; Bartone, Chris G

    2013-01-01

    An updated guide to GNSS, and INS, and solutions to real-world GNSS/INS problems with Kalman filtering Written by recognized authorities in the field, this third edition of a landmark work provides engineers, computer scientists, and others with a working familiarity of the theory and contemporary applications of Global Navigation Satellite Systems (GNSS), Inertial Navigational Systems, and Kalman filters. Throughout, the focus is on solving real-world problems, with an emphasis on the effective use of state-of-the-art integration techniques for those systems, especially the application of Kal

  13. A study on Relay Effect via Magnetic Resonant Coupling for Wireless Power Transfer

    Directory of Open Access Journals (Sweden)

    Rashid N.A.

    2016-01-01

    Full Text Available Wireless power transfer (WPT transmits electrical energy from a power source to an electrical load wirelessly or without any conductors. The capability of WPT to transmit the energy is limited. Therefore, a relay was introduced to increase the distance of the WPT capabilities. The effect of the relay has been investigated to extend the energy transfer distance. The effect of relay was demonstrated by placing a relay coil between transmitter and receiver, relay biased to transmitter and placing two relay coils in the designed system. Experimental results are provided to prove the concept of the relay effect. The power transmission efficiency can be achieved up to 75% at 1 meter distance.

  14. Joint Relay Selection and Link Adaptation for Distributed Beamforming in Regenerative Cooperative Networks

    CERN Document Server

    Yang, Wei; Wu, Gang; Wang, Haifeng

    2010-01-01

    Relay selection enhances the performance of the cooperative networks by selecting the links with higher capacity. Meanwhile link adaptation improves the spectral efficiency of wireless data-centric networks through adapting the modulation and coding schemes (MCS) to the current link condition. In this paper, relay selection is combined with link adaptation for distributed beamforming in a two-hop regenerative cooperative system. A novel signaling mechanism and related optimal algorithms are proposed for joint relay selection and link adaptation. In the proposed scheme, there is no need to feedback the relay selection results to each relay. Instead, by broadcasting the link adaptation results from the destination, each relay will automatically understand whether it is selected or not. The lower and upper bounds of the throughput of the proposed scheme are derived. The analysis and simulation results indicate that the proposed scheme provides synergistic gains compared to the pure relay selection and link adapt...

  15. Half-Duplex and Full-Duplex AF and DF Relaying with Energy-Harvesting in Log-Normal Fading

    KAUST Repository

    Rabie, Khaled M.

    2017-08-15

    Energy-harvesting (EH) and wireless power transfer in cooperative relaying networks have recently attracted a considerable amount of research attention. Most of the existing work on this topic however focuses on Rayleigh fading channels, which represent outdoor environments. In contrast, this paper is dedicated to analyze the performance of dual-hop relaying systems with EH over indoor channels characterized by log-normal fading. Both half-duplex (HD) and full-duplex (FD) relaying mechanisms are studied in this work with decode-and-forward (DF) and amplify-and-forward (AF) relaying protocols. In addition, three EH schemes are investigated, namely, time switching relaying, power splitting relaying and ideal relaying receiver which serves as a lower bound. The system performance is evaluated in terms of the ergodic outage probability for which we derive accurate analytical expressions. Monte Carlo simulations are provided throughout to validate the accuracy of our analysis. Results reveal that, in both HD and FD scenarios, AF relaying performs only slightly worse than DF relaying which can make the former a more efficient solution when the processing energy cost at the DF relay is taken into account. It is also shown that FD relaying systems can generally outperform HD relaying schemes as long as the loop-back interference in FD is relatively small. Furthermore, increasing the variance of the log-normal channel has shown to deteriorate the performance in all the relaying and EH protocols considered.

  16. Cooperative Handover Algorithm Based on Auxiliary Carrier in LTE-Advanced Relay System%LTE-Advanced中继系统基于辅助载波的协作切换算法

    Institute of Scientific and Technical Information of China (English)

    赵季红; 何炜扬; 曲桦

    2013-01-01

    切换是移动性管理的重要组成部分.在LTE-Advanced系统中,由于中继、载波聚合等新技术的引入,给系统的切换机制提出了更高的要求和挑战.通过对传统LTE-Advanced系统和LTE-Advanced中继系统切换过程的分析,提出了LTE-Advanced中继系统基于辅助载波的协作切换算法.该算法利用低频载波传播范围广、高频载波资源相对较多的优势,并结合中继技术和载波聚合技术,达到了降低切换中断概率、提高系统吞吐量的目的.%Handover is one of the most important parts in mobility management.In the LTE-Advanced system,more new technologies such as relay and carrier aggregation and so on were introduced,which put forward higher requirements and challenges to the handover mechanism of system.The handover process of the traditional LTE-Advanced system and LTE-Advanced relay system were analyzed,the cooperative handover algorithm based on auxiliary carrier in LTE-Advanced relay system was proposed.This algorithm makes use of the advantages of wide spreading of low-frequency carrier and rich resources of high-frequency carrier,and in conjunction with relay technology and carrier aggregation technology,achieving the purpose of reducing the handover outage probability and improving the throughput of the system.

  17. PERFORMANCE ANALYSIS OF COOPERATION SCHEMES IN EAVESDROPPER ASSISTED RELAY CHANNEL

    Directory of Open Access Journals (Sweden)

    Vaibhav Kumar Gupta

    2014-06-01

    Full Text Available The prominence of the wireless communication has been urging the monotonically increasing demand of security and privacy. In wireless systems, the notion of perfect secrecy of information with respect to illegitimate nodes can be ensured via physical layer security (PLS techniques. Unfortunately, they can be made less effective if source- eavesdropper wiretap channel is better than the main source-receiver channel. The various node cooperation schemes can be employed to combat this limitation where a relay node assists the communication to improve the performance significantly. In this paper, a four node wireless communication system consisting of a source, a destination, a relay and an eavesdropper as wire-tapper has been considered. The performance of the traditional cooperation schemes in terms of secrecy rate has been investigated with a different scenario where relay node helps the eavesdropper to deteriorate the secrecy rate. In addition, since legitimate receiver can overhear the transmission of relay, it favours the achievable secrecy rate. We formulate an analytical expression of conditional secrecy outage probability for the investigated system. From the obtained simulation results, it has been observed that secrecy rate is monotonically increases with path loss index. Furthermore, the proper selection of the system parameters leads to enhance the secrecy performance of the system even if relay pertains to degrade the performance. Amplify-and-forward, cooperation, decode-and-Forward, secrecy rate, relay.

  18. Satellite Constellation Design with Adaptively Continuous Ant System Algorithm

    Institute of Scientific and Technical Information of China (English)

    He Quan; Han Chao

    2007-01-01

    The ant system algorithm (ASA) has proved to be a novel meta-heuristic algorithm to solve many multivariable problems. In this paper, the earth coverage of satellite constellation is analyzed and a (n + 1)-fold coverage rate is put forward to evaluate the coverage performance of a satellite constellation. An optimization model of constellation parameters is established on the basis of the coverage performance. As a newly developed method, ASA can be applied to optimize the constellation parameters. In order to improve the ASA,a rule for adaptive number of ants is proposed, by which the search range is obviously enlarged and the convergence speed increased.Simulation results have shown that the ASA is more quick and efficient than other methods.

  19. Real Time Fire Reconnaissance Satellite Monitoring System Failure Model

    Science.gov (United States)

    Nino Prieto, Omar Ariosto; Colmenares Guillen, Luis Enrique

    2013-09-01

    In this paper the Real Time Fire Reconnaissance Satellite Monitoring System is presented. This architecture is a legacy of the Detection System for Real-Time Physical Variables which is undergoing a patent process in Mexico. The methodologies for this design are the Structured Analysis for Real Time (SA- RT) [8], and the software is carried out by LACATRE (Langage d'aide à la Conception d'Application multitâche Temps Réel) [9,10] Real Time formal language. The system failures model is analyzed and the proposal is based on the formal language for the design of critical systems and Risk Assessment; AltaRica. This formal architecture uses satellites as input sensors and it was adapted from the original model which is a design pattern for physical variation detection in Real Time. The original design, whose task is to monitor events such as natural disasters and health related applications, or actual sickness monitoring and prevention, as the Real Time Diabetes Monitoring System, among others. Some related work has been presented on the Mexican Space Agency (AEM) Creation and Consultation Forums (2010-2011), and throughout the International Mexican Aerospace Science and Technology Society (SOMECYTA) international congress held in San Luis Potosí, México (2012). This Architecture will allow a Real Time Fire Satellite Monitoring, which will reduce the damage and danger caused by fires which consumes the forests and tropical forests of Mexico. This new proposal, permits having a new system that impacts on disaster prevention, by combining national and international technologies and cooperation for the benefit of humankind.

  20. Set-up and Management of Relay Protection of 6kV Power Supply System in Coal Mines%煤矿 6kV供电系统继电保护的设置与管理

    Institute of Scientific and Technical Information of China (English)

    楚德全

    2001-01-01

    The relay protection of power supply system in a coal mine is of great importance to safe production of the mine.In this paper, the author advances some views on the management of the relay protection of power supply system according to his experience from the management of mechanical and electrical equipment and site work in many years, which can be as reference for the persons of the same occupation.%结合本单位 6kV供电系统继电保护的设置,就如何加强管理等问题提出了一些看法,供同行参考。

  1. Planning for a data base system to support satellite conceptual design

    Science.gov (United States)

    Claydon, C. R.

    1976-01-01

    The conceptual design of an automated satellite design data base system is presented. The satellite catalog in the system includes data for all earth orbital satellites funded to the hardware stage for launch between 1970 and 1980, and provides a concise compilation of satellite capabilities and design parameters. The cost of satellite subsystems and components will be added to the base. Data elements are listed and discussed. Sensor and science and applications opportunities catalogs will be included in the data system. Capabilities of the BASIS storage, retrieval, and analysis system are used in the system design.

  2. Assessment of a satellite power system and six alternative technologies

    Energy Technology Data Exchange (ETDEWEB)

    Wolsko, T.; Whitfield, R.; Samsa, M.; Habegger, L.S.; Levine, E.; Tanzman, E.

    1981-04-01

    The satellite power system is assessed in comparison to six alternative technologies. The alternatives are: central-station terrestrial photovoltaic systems, conventional coal-fired power plants, coal-gasification/combined-cycle power plants, light water reactor power plants, liquid-metal fast-breeder reactors, and fusion. The comparison is made regarding issues of cost and performance, health and safety, environmental effects, resources, socio-economic factors, and insitutional issues. The criteria for selecting the issues and the alternative technologies are given, and the methodology of the comparison is discussed. Brief descriptions of each of the technologies considered are included. (LEW)

  3. Reliable Remote Relay Protection in Smart Grid

    Institute of Scientific and Technical Information of China (English)

    Jiapeng Zhang; Yingfei Dong

    2015-01-01

    As the false trips of remote protection relays are among the main reasons behind cascading blackouts, it is critical to design reli⁃able relay protection. Even though common protection schemes on traditional power systems have been investigated for a few de⁃cades, cascading failures in recent years indicate more research needed in this area. Consequently, researchers have proposed agent⁃based methods on the Smart Grid (SG) to address this issue. However, these existing agent⁃based methods simply use TCP protocol without considering real⁃time communication requirements (such as bandwidth and delay). To deal with this issue, several methods for efficient network resource management are proposed. Furthermore, these existing methods do not consider the poten⁃tial issues in practical communication networks, which may result in delay violation and trigger relay false trips. We have dis⁃cussed simple backup solutions in the previous work. In this paper, in addition to network efficiency, we focus on improving the system reliability by exploring known power system information and minimizing the chances of false trips of important remote re⁃lays, e.g., defining power line priorities based on their importance. Moreover, to further improve the system reliability, we also in⁃vestigate the peer⁃to⁃peer protection approaches to address the single point of failure of centralized control center.

  4. 47 CFR 25.159 - Limits on pending applications and unbuilt satellite systems.

    Science.gov (United States)

    2010-10-01

    ... satellite systems. 25.159 Section 25.159 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Processing of Applications § 25.159 Limits on pending applications and unbuilt satellite systems. (a) Applicants with a total...

  5. On the Coverage Extension and Capacity Enhancement of Inband Relay Deployments in LTE-Advanced Networks

    Directory of Open Access Journals (Sweden)

    Abdallah Bou Saleh

    2010-01-01

    Full Text Available Decode-and-forward relaying is a promising enhancement to existing radio access networks and is currently being standardized in 3GPP to be part of the LTE-Advanced release 10. Two inband operation modes of relay nodes are to be supported, namely Type 1 and Type 1b. Relay nodes promise to offer considerable gain for system capacity or coverage depending on the deployment prioritization. However, the performance of relays, as any other radio access point, significantly depends on the propagation characteristics of the deployment environment. Hence, in this paper, we investigate the performance of Type 1 and Type 1b inband relaying within the LTE-Advanced framework in different propagation scenarios in terms of both coverage extension capabilities and capacity enhancements. A comparison between Type 1 and Type 1b relay nodes is as well presented to study the effect of the relaying overhead on the system performance in inband relay node deployments. System level simulations show that Type 1 and Type 1b inband relay deployments offer low to very high gains depending on the deployment environment. As well, it is shown that the effect of the relaying overhead is minimal on coverage extension whereas it is more evident on system throughput.

  6. Modular High-Energy Systems for Solar Power Satellites

    Science.gov (United States)

    Howell, Joe T.; Carrington, Connie K.; Marzwell, Neville I.; Mankins, John C.

    2006-01-01

    Modular High-Energy Systems are Stepping Stones to provide capabilities for energy-rich infrastructure located in space to support a variety of exploration scenarios as well as provide a supplemental source of energy during peak demands to ground grid systems. Abundant renewable energy at lunar or other locations could support propellant production and storage in refueling scenarios that enable affordable exploration. Renewable energy platforms in geosynchronous Earth orbits can collect and transmit power to satellites, or to Earth-surface locations. Energy-rich space technologies also enable the use of electric-powered propulsion systems that could efficiently deliver cargo and exploration facilities to remote locations. A first step to an energy-rich space infrastructure is a 100-kWe class solar-powered platform in Earth orbit. The platform would utilize advanced technologies in solar power collection and generation, power management and distribution, thermal management, electric propulsion, wireless avionics, autonomous in space rendezvous and docking, servicing, and robotic assembly. It would also provide an energy-rich free-flying platform to demonstrate in space a portfolio of technology flight experiments. This paper summary a preliminary design concept for a 100-kWe solar-powered satellite system to demonstrate in-flight a variety of advanced technologies, each as a separate payload. These technologies include, but are not limited to state-of-the-art solar concentrators, highly efficient multi-junction solar cells, integrated thermal management on the arrays, and innovative deployable structure design and packaging to enable the 100-kW satellite feasible to launch on one existing launch vehicle. Higher voltage arrays and power distribution systems (PDS) reduce or eliminate the need for massive power converters, and could enable direct-drive of high-voltage solar electric thrusters.

  7. Guidance, Navigation, and Control System for Maneuverable Pico-Satellites Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A compact, low-power GN&C system is essential to the success of pico-satellite Automated Rendezvous and Docking (AR&D). Austin Satellite Design (ASD)...

  8. Preface: BeiDou Navigation Satellite System (BDS)/GNSS+: Recent progress and new applications

    Science.gov (United States)

    Jin, Shuanggen

    2017-02-01

    Nowadays, the new China's BeiDou Navigation Satellite System (BDS) has been developed well. At the end of 2016, over 23 BDS satellites were launched, including five geostationary Earth orbit (GEO) satellites, five inclined geosynchronous orbit (IGSO) satellites and nine medium Earth orbit (MEO) satellites. The current BDS service covers China and most Asia-Pacific regions with accuracy of better than 10 m in positioning, 0.2 m/s in velocity and 50 ns in timing. The BDS with global coverage will be completely established by 2020 with five GEO satellites and 30 MEO satellites. The main function of BDS is the positioning, navigation and timing (PNT) as well as short message communications. Together with the United States' GPS, Russia's GLONASS and the European Union's Galileo system as well as other regional augmentation systems, more new applications of multi-Global Navigation Satellite Systems (GNSS) will be exploited and realized in the next decades.

  9. Guidance, Navigation, and Control System for Maneuverable Pico-Satellites Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Pico-satellites are an emerging new class of spacecraft. Maneuverable pico-satellites require active guidance, navigation, and control (GN&C) systems to perform...

  10. On the Performance of Selection Relaying

    OpenAIRE

    Adinoyi, Abdulkareem; Fan, Yijia; Yanikomeroglu, Halim; Poor, H. Vincent

    2008-01-01

    Interest in selection relaying is growing. The recent developments in this area have largely focused on information theoretic analyses such as outage performance. Some of these analyses are accurate only at high SNR regimes. In this paper error rate analyses that are sufficiently accurate over a wide range of SNR regimes are provided. The motivations for this work are that practical systems operate at far lower SNR values than those supported by the high SNR analysis. To enable designers to m...

  11. Comparison between several satellite constellation schemes for MEO-TDRSS of China

    Institute of Scientific and Technical Information of China (English)

    Wu Tingyong; Wu Shiqi

    2008-01-01

    The satellite constellation classes,which are suitable for the medium earth orbit tracking and data relay satellite system (MEO-TDRSS) of China,are investigated.On the basis of the functionality and the traffic distribution characteristic of MEO-TURSS,the coverage performance and inter-satellite link properties of four different constellation schemes are compared by simulations.Simulation results indicate that the rosette and common-track constellations,whose satellites are distributed on the celestial sphere more uniformly,are appropriate for the implementation of MEO-TDRSS of China.

  12. Optimal power allocation scheme based on minimizing outage probability in two-path relay system%Two-path中继系统中基于最小化中断概率的功率分配方法

    Institute of Scientific and Technical Information of China (English)

    方恒刚; 李莉; 张静; 罗汉文

    2013-01-01

    In order to decrease the outage probability of two-path relay system, this paper derived a closed-form solution of outage probability in DF two-path relay system with the inter-relay interference, and then proposed an optimal power allocation algorithm to minimize the outage probability under the limited total power. The simulation results show that this algorithm can effectively decrease the outage probability and improve the performance of the system.%为了降低two-path中继系统的通信中断概率,针对DF协议中继,推导了two-path中继系统在存在中继间干扰情况下的中断概率闭式解,并在总功率受限的情况下,提出了一种最小化中断概率的最优功率分配算法.仿真验证结果表明该算法能够有效地降低系统的中断概率,提高系统的性能.

  13. 基于VR-Platform的无人机中继通信虚拟教学系统%Virtual Teaching System of UAV Relay Communication Based on VR-Platform

    Institute of Scientific and Technical Information of China (English)

    贾鹏万; 冯寿鹏; 张爱辉

    2012-01-01

    Aiming at the existing practical problems in the teaching of UAV relay communication, such as limited training space and equipment and the high cost-effective training, a virtual teaching system of UAV relay communication based on VR-Platform is proposed, structure and function of which is designed. Three-dimensional modeling, scenario development, and partial system functions are implemented by using the virtual reality software platform of 3ds Max and VR-Platform. It forms the base for integration and improving of virtual teaching system of UAV relay communication.%针对无人机中继通信教学过程中存在的装备有限、培训效费比较高、训练场地受限等实际问题,提出一种基于VR-Platform的无人机中继通信虚拟教学系统,并对系统的结构和功能进行详细设计,运用3ds Max和VR-Platform相结合的虚拟现实软件开发平台,进行三维建模和场景开发,实现了系统的部分功能,为下一步虚拟教学系统的整合和完善奠定了基础.

  14. Simulation of Distance Relay for Load Encroachment Alleviation with Agent Based Supervision of Zone3

    Directory of Open Access Journals (Sweden)

    Mohamed Badr

    2017-03-01

    Full Text Available Cascaded tripping of power lines due to mal-operation of zone-3 distance relays has been one of the main causes of many previous blackouts worldwide. Encroachment of load into zone-3 characteristics during stressed system operation conditions is a basic factor for such mal-operation of the relays. By improving the operation of zone-3, it is possible to prevent mal-operations so that cascaded line tripping can be avoided. For proper study of the behavior of distance relay during faults and load encroachment phenomenon, we must build a model of distance relay, so in this paper a modeling study of distance relay is implemented using MATLAB/Simulink program. However, this model is distinguished from previous models that, examines in detail the third zone of distance relay. Many cases are simulated with changing line loading and fault location to ensure the capability of the relay to detect the fault and thus the maximum load ability limit of distance relay is obtained. In order to prevent cascading events caused by hidden failures in zone-3 relays, agent based relay architectures have been suggested in the recent past. In such architectures each zone-3 relay contains agents that require communication with other agents at various relevant relays in order to distinguish a real zone-3 event from a temporary overload. In this paper, a local master agent is consulted by all zone-3 agents before a tripping decision is made. The master agent maintains a rule base which is updated based on the local topology of the network and real time monitoring of the status of other relays and circuit breakers. Cisco Packet Tracer program is used for running communication network simulations. The result of the simulation indicate that the time estimated to send and receive a packet data unit (PDU message between one relay to anther can satisfy the communication requirement for the proposed scheme with fiber media.

  15. Designing nonuniform satellite systems for continuous global coverage using equatorial and polar circular orbits

    Science.gov (United States)

    Ulybyshev, S. Yu.

    2016-07-01

    We present a method for designing nonuniform satellite systems for continuous global coverage using a combination of equatorial and near-polar satellite segments in circular orbits. Equations are derived to determine the basic design parameters of the satellite system itself and the conditions of its closure at the joint of near-polar and equatorial segments. We analyze specific features of near-polar and equatorial satellite systems and their advantages and disadvantages compared with existing classes of near-polar phased and kinematically correct satellite systems. We estimate the minimum required number of spacecrafts in satellite systems for a given fold of coverage and present calculated dependences for classes of near-polar phased and equatorial satellite systems with different types of closure. For the class of kinematically correct satellite systems, we analyze the characteristics of systems with a minimum spacecraft flight height and reveal that the number of satellites in the orbital plane depends on the flight height for different folds of coverage. We bring examples of the best near-polar equatorial satellite systems of global coverage for different folds and a class of satellite systems with a fixed number of spacecrafts and orbital planes in them.

  16. Sum Rate Maximized Resource Allocation in Multiple DF Relays Aided OFDM Transmission

    CERN Document Server

    Wang, Tao

    2011-01-01

    In relay-aided wireless transmission systems, one of the key issues is how to decide assisting relays and manage the energy resource at the source and each individual relay, to maximize a certain objective related to system performance. This paper addresses the sum rate maximized resource allocation (RA) problem in a point to point orthogonal frequency division modulation (OFDM) transmission system assisted by multiple decode-and-forward (DF) relays, subject to the individual sum power constraints of the source and the relays. In particular, the transmission at each subcarrier can be in either the direct mode without any relay assisting, or the relay-aided mode with one or several relays assisting. We propose two RA algorithms which optimize the assignment of transmission mode and source power for every subcarrier, as well as the assisting relays and the power allocation to them for every {relay-aided} subcarrier. First, it is shown that the considered RA problem has zero Lagrangian duality gap when there is ...

  17. Relay Mirror Experiment overview: a GBL pointing and tracking demonstration

    Science.gov (United States)

    Dierks, Jeffrey S.; Ross, Susan E.; Brodsky, Aaron; Kervin, Paul W.; Holm, Richard W.

    1991-08-01

    The Relay Mirror Experiment (RME) has successfully demonstrated long-range, low-jitter tracking and pointing capabilities appropriate for ground-based laser (GBL) propagation. The RME program includes (1) a passively maneuverable, free-flying low-orbit spacecraft with a laser diode beacon and spoiled retroreflectors as acquisition aids; (2) a payload experiment package (PEP) consisting of sensors, optics, steerable mirrors, and control electronics. This subsystem accomplishes GBL tracking and pointing and the associated positioning of a space-based relay mirror sufficiently to relay an infrared beam between two ground sites. Design considerations for the control system included base motion disturbance and calibration; (3) two GBL sites each a tracking and pointing exercise in itself, using a combination of sensors and acquisition and tracking capabilities. One site includes a beam relay scoring capability.

  18. The 2009 Relay Race

    CERN Multimedia

    2009-01-01

    The 2009 CERN Relay Race was as popular as ever, with a record number of 88 teams competing. var flash_video_player=get_video_player_path(); insert_player_for_external('Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-0753-kbps-480x360-25-fps-audio-64-kbps-44-kHz-stereo', 'mms://mediastream.cern.ch/MediaArchive/Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-Multirate-200-to-753-kbps-480x360.wmv', 'false', 288, 216, 'https://mediastream.cern.ch/MediaArchive/Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-posterframe-480x360-at-10-percent.jpg', '1178303', true, 'Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-0600-kbps-maxH-360-25-fps-audio-128-kbps-48-kHz-stereo.mp4'); Even the rain didn’t dampen the spirits, and it still managed to capture the ‘festival feeling’ with live music, beer and stalls from various CERN clubs set up outside Restaurant 1. The Powercuts on the podium after win...

  19. Joint Source and Relay Precoding Designs for MIMO Two-Way Relaying Based on MSE Criterion

    CERN Document Server

    Wang, Rui

    2011-01-01

    Properly designed precoders can significantly improve the spectral efficiency of multiple-input multiple-output (MIMO) relay systems. In this paper, we investigate joint source and relay precoding design based on the mean-square-error (MSE) criterion in MIMO two-way relay systems, where two multi-antenna source nodes exchange information via a multi-antenna amplify-and-forward relay node. This problem is non-convex and its optimal solution remains unsolved. Aiming to find an efficient way to solve the problem, we first decouple the primal problem into three tractable sub-problems, and then propose an iterative precoding design algorithm based on alternating optimization. The solution to each sub-problem is optimal and unique, thus the convergence of the iterative algorithm is guaranteed. Secondly, we propose a structured precoding design to lower the computational complexity. The proposed precoding structure is able to parallelize the channels in the multiple access (MAC) phase and broadcast (BC) phase. It th...

  20. Pragmatic Analysis of Internet Relay Chat

    Institute of Scientific and Technical Information of China (English)

    张永芳

    2005-01-01

    This article presents a pragmatic analysis of Internet Relay chat. Text-only chat room conversation has been claimed to be interactionally incoherent due to limitations imposed by messaging systems on turn taking. The article tries to schematize the conversational relationships of the speakers in a text-based medium and apply a pragmatic point of view based on the model of turn allocation and the Cooperative Prjnciple. An extract of flowing logs in an on-line chat room is analyzed thoroughly in an attempt to explore the way in which Internet interactants behave in a virtual space. The paper shows that some pragmatic rules people follow in everyday oral conversation are followed in Internet relay chat too.

  1. Joint Polar Satellite System (JPSS) Common Ground System (CGS) Block 3.0 Communications Strategies

    Science.gov (United States)

    Miller, S. W.; Grant, K. D.; Ottinger, K.

    2015-12-01

    The National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) are jointly acquiring the next-generation civilian weather and environmental satellite system: the Joint Polar Satellite System (JPSS). The JPSS program is the follow-on for both space and ground systems to the Polar-orbiting Operational Environmental Satellites (POES) managed by NOAA. The JPSS satellites will carry a suite of sensors designed to collect meteorological, oceanographic, climatological and geophysical observations of the Earth. The ground processing system for JPSS is known as the JPSS Common Ground System (JPSS CGS). Developed and maintained by Raytheon Intelligence, Information and Services (IIS), the CGS is a globally distributed, multi-mission system serving NOAA, NASA and their national and international partners. The CGS has demonstrated its scalability and flexibility to incorporate multiple missions efficiently and with minimal cost, schedule and risk, while strengthening global partnerships in weather and environmental monitoring. In a highly successful international partnership between NOAA and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), the CGS currently provides data routing from McMurdo Station in Antarctica to the EUMETSAT processing center in Darmstadt, Germany. Continuing and building upon that partnership, NOAA and EUMETSAT are collaborating on the development of a new path forward for the 2020's. One approach being explored is a concept of operations where each organization shares satellite downlink resources with the other. This paper will describe that approach, as well as modeling results that demonstrate its feasibility and expected performance.

  2. Production process for advanced space satellite system cables/interconnects.

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza, Luis A.

    2007-12-01

    This production process was generated for the satellite system program cables/interconnects group, which in essences had no well defined production process. The driver for the development of a formalized process was based on the set backs, problem areas, challenges, and need improvements faced from within the program at Sandia National Laboratories. In addition, the formal production process was developed from the Master's program of Engineering Management for New Mexico Institute of Mining and Technology in Socorro New Mexico and submitted as a thesis to meet the institute's graduating requirements.

  3. Satellite Power System (SPS) financial/management scenarios

    Science.gov (United States)

    Vajk, J. P.

    1978-01-01

    The possible benefits of a Satellite Power System (SPS) program, both domestically and internationally, justify detailed and imaginative investigation of the issues involved in financing and managing such a large-scale program. In this study, ten possible methods of financing a SPS program are identified ranging from pure government agency to private corporations. The following were analyzed and evaluated: (1) capital requirements for SPS; (2) ownership and control; (3) management principles; (4) organizational forms for SPS; (5) criteria for evaluation; (6) detailed description and preliminary evaluation of alternatives; (7) phased approaches; and (8) comparative evaluation. Key issues and observations and recommendations for further study are also presented.

  4. Handoff algorithm for mobile satellite systems with ancillary terrestrial component

    KAUST Repository

    Sadek, Mirette

    2012-06-01

    This paper presents a locally optimal handoff algorithm for integrated satellite/ground communication systems. We derive the handoff decision function and present the results in the form of tradeoff curves between the number of handoffs and the number of link degradation events in a given distance covered by the mobile user. This is a practical receiver-controlled handoff algorithm that optimizes the handoff process from a user perspective based on the received signal strength rather than from a network perspective. © 2012 IEEE.

  5. Efficient medium access control protocol for geostationary satellite systems

    Institute of Scientific and Technical Information of China (English)

    王丽娜; 顾学迈

    2004-01-01

    This paper proposes an efficient medium access control (MAC) protocol based on multifrequency-time division multiple access (MF-TDMA) for geostationary satellite systems deploying multiple spot-beams and onboard processing,which uses a method of random reservation access with movable boundaries to dynamically request the transmission slots and can transmit different types of traffic. The simulation results have shown that our designed MAC protocol can achieve a high bandwidth utilization, while providing the required quality of service (QoS) for each class of service.

  6. The Federated Satellite Systems paradigm: Concept and business case evaluation

    Science.gov (United States)

    Golkar, Alessandro; Lluch i Cruz, Ignasi

    2015-06-01

    This paper defines the paradigm of Federated Satellite Systems (FSS) as a novel distributed space systems architecture. FSS are networks of spacecraft trading previously inefficiently allocated and unused resources such as downlink bandwidth, storage, processing power, and instrument time. FSS holds the promise to enhance cost-effectiveness, performance and reliability of existing and future space missions, by networking different missions and effectively creating a pool of resources to exchange between participants in the federation. This paper introduces and describes the FSS paradigm, and develops an approach integrating mission analysis and economic assessments to evaluate the feasibility of the business case of FSS. The approach is demonstrated on a case study on opportunities enabled by FSS to enhance space exploration programs, with particular reference to the International Space Station. The application of the proposed methodology shows that the FSS concept is potentially able to create large commercial markets of in-space resources, by providing the technical platform to offer the opportunity for spacecraft to share or make use of unused resources within their orbital neighborhood. It is shown how the concept is beneficial to satellite operators, space agencies, and other stakeholders of the space industry to more flexibly interoperate space systems as a portfolio of assets, allowing unprecedented collaboration among heterogeneous types of missions.

  7. Basic performance of BeiDou-2 navigation satellite system used in LEO satellites precise orbit determination

    Directory of Open Access Journals (Sweden)

    Liu Junhong

    2014-10-01

    Full Text Available The visibility for low earth orbit (LEO satellites provided by the BeiDou-2 system is analyzed and compared with the global positioning system (GPS. In addition, the spaceborne receivers’ observations are simulated by the BeiDou satellites broadcast ephemeris and LEO satellites orbits. The precise orbit determination (POD results show that the along-track component accuracy is much better over the service area than the non-service area, while the accuracy of the other two directions keeps at the same level over different areas. However, the 3-dimensional (3D accuracy over the two areas shows almost no difference. Only taking into consideration the observation noise and navigation satellite ephemeris errors, the 3D accuracy of the POD is about 30 cm. As for the precise relative orbit determination (PROD, the 3D accuracy is much better over the eastern hemisphere than that of the western hemisphere. The baseline length accuracy is 3.4 mm over the service area, and it is still better than 1 cm over the non-service area. This paper demonstrates that the BeiDou regional constellation could provide global service to LEO satellites for the POD and the PROD. Finally, the benefit of geostationary earth orbit (GEO satellites is illustrated for POD.

  8. Basic performance of BeiDou-2 navigation satellite system used in LEO satellites precise orbit determination

    Institute of Scientific and Technical Information of China (English)

    Liu Junhong; Gu Defeng; Ju Bing; Yao Jing; Duan Xiaojun; Yi Dongyun

    2014-01-01

    The visibility for low earth orbit (LEO) satellites provided by the BeiDou-2 system is analyzed and compared with the global positioning system (GPS). In addition, the spaceborne receivers’ observations are simulated by the BeiDou satellites broadcast ephemeris and LEO satel-lites orbits. The precise orbit determination (POD) results show that the along-track component accuracy is much better over the service area than the non-service area, while the accuracy of the other two directions keeps at the same level over different areas. However, the 3-dimensional (3D) accuracy over the two areas shows almost no difference. Only taking into consideration the observation noise and navigation satellite ephemeris errors, the 3D accuracy of the POD is about 30 cm. As for the precise relative orbit determination (PROD), the 3D accuracy is much better over the eastern hemisphere than that of the western hemisphere. The baseline length accuracy is 3.4 mm over the service area, and it is still better than 1 cm over the non-service area. This paper demon-strates that the BeiDou regional constellation could provide global service to LEO satellites for the POD and the PROD. Finally, the benefit of geostationary earth orbit (GEO) satellites is illustrated for POD.

  9. Performance Evaluation of Data Compression Systems Applied to Satellite Imagery

    Directory of Open Access Journals (Sweden)

    Lilian N. Faria

    2012-01-01

    Full Text Available Onboard image compression systems reduce the data storage and downlink bandwidth requirements in space missions. This paper presents an overview and evaluation of some compression algorithms suitable for remote sensing applications. Prediction-based compression systems, such as DPCM and JPEG-LS, and transform-based compression systems, such as CCSDS-IDC and JPEG-XR, were tested over twenty multispectral (5-band images from CCD optical sensor of the CBERS-2B satellite. Performance evaluation of these algorithms was conducted using both quantitative rate-distortion measurements and subjective image quality analysis. The PSNR, MSSIM, and compression ratio results plotted in charts and the SSIM maps are used for comparison of quantitative performance. Broadly speaking, the lossless JPEG-LS outperforms other lossless compression schemes, and, for lossy compression, JPEG-XR can provide lower bit rate and better tradeoff between compression ratio and image quality.

  10. Consensus for Multiagent Systems with Nonlinear Dynamics and Time Delays Using a Two-Hop Relay Adaptive Method

    Directory of Open Access Journals (Sweden)

    Qian Cao

    2014-01-01

    Full Text Available This paper investigates the consensus problem for multiagent systems with nonlinear dynamics and time delays. A distributed adaptive consensus protocol is proposed in which the time delays are explicitly included in the adaptive algorithm. It is shown that the resultant closed loop system involves doubly larger time delays, making the stability analysis nontrivial. Stability condition on maximum tolerable time delay is established and controlled by the proposed two-hop adaptive algorithm. The explicit expression of the delay margin is derived and analyzed in the frequency domain. Both the agent state errors and the estimation parameter errors converge to zero. A simulation example is illustrated to verify the theory results.

  11. Controllability Analysis for Operation Margin of Zone 3 Impedance Relay

    Science.gov (United States)

    Li, Shenghu; Yorino, Naoto; Zoka, Yoshifumi

    Undesirable operation of zone 3 impedance relay (mho relays) is a possible factor for causing cascading failure as seen in several previous large scale blackouts, where power flow redistribution and power swing caused by outage or switching operations satisfy the condition for the relay operation. So far, the condition itself has not fully been investigated, and therefore, there has been little attempt to avoid the relay operation by means of direct power flow control. This paper analyzes the condition for zone 3 relay operation from the viewpoint of its sensitivity to power flow. An operating margin for security is defined for each relay to carry out effective monitoring. It is newly pointed out that undesirable operation can be effectively avoided by reactive power controls as well as real power controls. The method to compute the operation margin is also given through the analysis of the optimal Var location to control the operation margin. Effectiveness of the proposed method is demonstrated using the IEEE test systems.

  12. Mobile radio alternative systems study satellite/terrestrial (hybrid) systems concepts

    Science.gov (United States)

    Kiesling, J. D.; Anderson, R. E.

    1983-01-01

    The use of satellites for mobile radio service in non-urban areas of the United States in the years from 1985 to 2000 was investigated. Several satellite concepts are considered: a system with single-beam coverage of the fifty United States and Puerto Rico, and multi-beam satellites with greater capacity. All of the needed functions and services identified in the market study are provided by the satellite systems, including nationwide radio access to vehicles without knowledge of vehicle location wideband data transmission from remote sites, two way exchange of short data and control messages between vehicles and dispatch or control centers, and automatic vehicle location (surveillance). The costs of providing the services are within acceptable limits, and the desired returns to the system investors are attractive. The criteria by which the Federal Communication judges the competing demands for public radio spectrum are reviewed with comments on how the criteria might apply to the consideration of land mobile satellites. Institutional arrangements for operating a mobile satellite system are based on the present institutional arrangements in which the services are offered to the end users through wireline and radio common carriers, with direct access by large private and government users.

  13. Low Earth orbit communications satellite

    Science.gov (United States)

    Moroney, D.; Lashbrook, D.; Mckibben, B.; Gardener, N.; Rivers, T.; Nottingham, G.; Golden, B.; Barfield, B.; Bruening, J.; Wood, D.

    1992-01-01

    A current thrust in satellite communication systems considers a low-Earth orbiting constellations of satellites for continuous global coverage. Conceptual design studies have been done at the time of this design project by LORAL Aerospace Corporation under the program name GLOBALSTAR and by Motorola under their IRIDIUM program. This design project concentrates on the spacecraft design of the GLOBALSTAR low-Earth orbiting communication system. Overview information on the program was gained through the Federal Communications Commission licensing request. The GLOBALSTAR system consists of 48 operational satellites positioned in a Walker Delta pattern providing global coverage and redundancy. The operational orbit is 1389 km (750 nmi) altitude with eight planes of six satellites each. The orbital planes are spaced 45 deg., and the spacecraft are separated by 60 deg. within the plane. A Delta 2 launch vehicle is used to carry six spacecraft for orbit establishment. Once in orbit, the spacecraft will utilize code-division multiple access (spread spectrum modulation) for digital relay, voice, and radio determination satellite services (RDSS) yielding position determination with accuracy up to 200 meters.

  14. A low cost data logging system with satellite transmission capabilities

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, E.S.; DeSa, E.J.; Desai, R.G.P.

    satellite navigator, deep sea echosounder, and a magnetometer on board a chartered research vessel. A novel data logger design was implemented with the extra option of transmitting logged data through the ships INMARSAT approved satellite terminal...

  15. A system architecture for an advanced Canadian wideband mobile satellite system

    Science.gov (United States)

    Takats, P.; Keelty, M.; Moody, H.

    In this paper, the system architecture for an advanced Canadian ka-band geostationary mobile satellite system is described, utilizing hopping spot beams to support a 256 kbps wideband service for both N-ISDN and packet-switched interconnectivity to small briefcase-size portable and mobile terminals. An assessment is given of the technical feasibility of the satellite payload and terminal design in the post year 2000 timeframe. The satellite payload includes regeneration and on-board switching to permit single hop interconnectivity between mobile terminals. The mobile terminal requires antenna tracking and platform stabilization to ensure acquisition of the satellite signal. The potential user applications targeted for this wideband service includes: home-office, multimedia, desk-top (PC) videoconferencing, digital audio broadcasting, single and multi-user personal communications.

  16. Performance analysis of selective cooperation with fixed gain relays in Nakagami-m channels

    KAUST Repository

    Hussain, Syed Imtiaz

    2012-09-01

    Selecting the best relay using the maximum signal to noise ratio (SNR) among all the relays ready to cooperate saves system resources and utilizes the available bandwidth more efficiently compared to the regular all-relay cooperation. In this paper, we analyze the performance of the best relay selection scheme with fixed gain relays operating in Nakagami-. m channels. We first derive the probability density function (PDF) of upper bounded end-to-end SNR of the relay link. Using this PDF, we derive some key performance parameters for the system including average bit error probability and average channel capacity. The analytical results are verified through Monte Carlo simulations. © 2012 Elsevier B.V.

  17. Near optimal power allocation algorithm for OFDM-based cognitive using adaptive relaying strategy

    KAUST Repository

    Soury, Hamza

    2012-01-01

    Relayed transmission increases the coverage and achievable capacity of communication systems. Adaptive relaying scheme is a relaying technique by which the benefits of the amplifying or decode and forward techniques can be achieved by switching the forwarding technique according to the quality of the signal. A cognitive Orthogonal Frequency-Division Multiplexing (OFDM) based adaptive relaying protocol is considered in this paper. The objective is to maximize the capacity of the cognitive radio system while ensuring that the interference introduced to the primary user is below the tolerated limit. A Near optimal power allocation in the source and the relay is presented for two pairing techniques such that the matching and random pairing. The simulation results confirm the efficiency of the proposed adaptive relaying protocol, and the consequence of choice of pairing technique. © 2012 ICST.

  18. The Arctic Regional Communications Small SATellite (ARCSAT)

    Science.gov (United States)

    Casas, Joseph; Kress, Martin; Sims, William; Spehn, Stephen; Jaeger, Talbot; Sanders, Devon

    2013-01-01

    Traditional satellite missions are extremely complex and expensive to design, build, test, launch and operate. Consequently many complementary operational, exploration and research satellite missions are being formulated as a growing part of the future space community capabilities using formations of small, distributed, simple to launch and inexpensive highly capable small scale satellites. The Arctic Regional Communications small SATellite (ARCSAT) initiative would launch a Mini-Satellite "Mothership" into Polar or Sun Sync low-earth-orbit (LEO). Once on orbit, the Mothership would perform orbital insertion of four internally stored independently maneuverable nanosatellites, each containing electronically steerable antennas and reconfigurable software-defined radios. Unlike the traditional geostationary larger complex satellite communication systems, this LEO communications system will be comprised of initially a five small satellite formation that can be later incrementally increased in the total number of satellites for additional data coverage. ARCSAT will provide significant enabling capabilities in the Arctic for autonomous voice and data communications relay, Maritime Domain Awareness (MDA), data-extraction from unattended sensors, and terrestrial Search & Rescue (SAR) beacon detection missions throughout the "data starved desert" of the Arctic Region.

  19. Use of satellite images for the monitoring of water systems

    Science.gov (United States)

    Hillebrand, Gudrun; Winterscheid, Axel; Baschek, Björn; Wolf, Thomas

    2015-04-01

    Satellite images are a proven source of information for monitoring ecological indicators in coastal waters and inland river systems. This potential of remote sensing products was demonstrated by recent research projects (e.g. EU-funded project Freshmon - www.freshmon.eu) and other activities by national institutions. Among indicators for water quality, a particular focus was set on the temporal and spatial dynamics of suspended particulate matter (SPM) and Chlorophyll-a (Chl-a). The German Federal Institute of Hydrology (BfG) was using the Weser and Elbe estuaries as test cases to compare in-situ measurements with results obtained from a temporal series of automatically generated maps of SPM distributions based on remote sensing data. Maps of SPM and Chl-a distributions in European inland rivers and alpine lakes were generated by the Freshmon Project. Earth observation based products are a valuable source for additional data that can well supplement in-situ monitoring. For 2015, the BfG and the Institute for Lake Research of the State Institute for the Environment, Measurements and Nature Conservation of Baden-Wuerttemberg, Germany (LUBW) are in the process to start implementing an operational service for monitoring SPM and Chl-a based on satellite images (Landsat 7 & 8, Sentinel 2, and if required other systems with higher spatial resolution, e.g. Rapid Eye). In this 2-years project, which is part of the European Copernicus Programme, the operational service will be set up for - the inland rivers of Rhine and Elbe - the North Sea estuaries of Elbe, Weser and Ems. Furthermore - Lake Constance and other lakes located within the Federal State of Baden-Wuerttemberg. In future, the service can be implemented for other rivers and lakes as well. Key feature of the project is a data base that holds the stock of geo-referenced maps of SPM and Chl-a distributions. Via web-based portals (e.g. GGInA - geo-portal of the BfG; UIS - environmental information system of the

  20. Mobility-Based Mobile Relay Selection in MANETs

    Science.gov (United States)

    Kim, Gilnam; Lee, Hyoungjoo; Lee, Kwang Bok

    The future wireless mobile communication networks are expected to provide seamless wireless access and data exchange to mobile users. In particular, it is expected that the demand for ubiquitous data exchange between mobile users will increase with the widespread use of various wireless applications of the intelligent transportation system (ITS) and intelligent vehicles. Mobile ad hoc networks (MANETs) are one of the representative research areas pursuing the technology needed to satisfy the increasing mobile communication requirements. However, most of the works on MANET systems do not take into account the continuous and dynamic changes of nodal mobility to accommodate system design and performance evaluation. The mobility of nodes limits the reliability of communication between the source and the destination node since a link between two continuously moving nodes is established only when one node enters the transmission range of the other. To alleviate this problem, mobile relay has been studied. In particular, it is shown that relay selection is an efficient way to support nodal mobility in MANET systems. In this paper, we propose a mobility-based relay selection algorithm for the MANET environment. Firstly, we define the lifetime as the maximum link duration for which the link between two nodes remains active. Therefore, the lifetime indicates the reliability of the relay link which measures its capability to successfully support relayed communication when requested by the source node. Furthermore, we consider a series of realistic scenarios according to the randomness of nodal mobility. Thus, the proposed algorithm can be easily applied in practical MANET systems by choosing the appropriate node mobility behavior. The numerical results show that the improved reliability of the proposed algorithm's relayed communication is achieved with a proper number of mobile relay nodes rather than with the conventional selection algorithm. Lastly, we show that random

  1. The changing world of global navigation satellite systems

    Science.gov (United States)

    Dow, John M.; Neilan, Ruth E.; Higgins, Matt; Arias, Felicitas

    The world of global navigation satellite systems (GNSS) has been changing very rapidly during the last years. New constellations are being developed in Europe (Galileo), India (IRNSS), Japan (QZNSS) and China (Compass), while both the US GPS and the Russian GLONASS programmes are engaged in very significant mediumto long-term improvements, which will make them even more valuable in the coming years to an ever wider range of civilian users. In addition, powerful regional augmentation systems are becoming (or have already become) operational, providing users with important real time information concerning the integrity of the signals being broadcast by those two systems: these include the US WAAS, the European EGNOS, the Japanese MSAS, the Indian GAGAN and others. Following a number of United Nations sponsored regional workshops, a report by an ad hoc UN "GNSS Action Team" and several preparatory meetings, the International Committee on GNSS (ICG) was established in December 2005 in Vienna, Austria. The ICG is an informal body with the main objective of promoting cooperation on matters of mutual interest related to civil satellite-based positioning, navigation, timing, and value-added services, as well as compatibility and interoperability among the GNSS systems. A further important objective is to encourage the use of GNSS to support sustainable development, particularly in the developing countries. The United Nations Office for Outer Space Affairs (UNOOSA) plays a key role in facilitating the work of the ICG. The members of the Committee are GNSS system providers, while international organisations representing users of GNSS can qualify for participation in the work of the Committee as associate members or observers. The interests of the space geodetic, mapping and timing communities are represented in particular through ICG associate membership of the IGS, IAG, FIG, IERS, while BIPM is an ICG observer. This paper will highlight the background of these developments

  2. System Design and Key Technologies of the GF-3 Satellite

    Directory of Open Access Journals (Sweden)

    ZHANG Qingjun

    2017-03-01

    Full Text Available GF-3 satellite, the first C band and multi-polarization SAR satellite in China, achieves breakthroughs in a number of core and key technologies. The satellite technology abides by the principle of “Demand Pulls, Technology Pushes”, forming a series of innovation point, and reaching or surpassing international level in main technical specification.

  3. Modified Dynamic Decode-and-Forward Relaying Protocol for Type II Relay in LTE-Advanced and Beyond

    KAUST Repository

    Nam, Sung Sik

    2016-11-29

    In this paper, we propose a modified dynamic decode-and-forward (MoDDF) relaying protocol to meet the critical requirements for user equipment (UE) relays in next-generation cellular systems (e.g., LTE-Advanced and beyond). The proposed MoDDF realizes the fast jump-in relaying and the sequential decoding with an application of random codeset to encoding and re-encoding process at the source and the multiple UE relays, respectively. A subframe-by-subframe decoding based on the accumulated (or buffered) messages is employed to achieve energy, information, or mixed combining. Finally, possible early termination of decoding at the end user can lead to the higher spectral efficiency and more energy saving by reducing the frequency of redundant subframe transmission and decoding. These attractive features eliminate the need of directly exchanging control messages between multiple UE relays and the end user, which is an important prerequisite for the practical UE relay deployment. Copyright: © 2016 Nam et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

  4. Preliminary environmental assessment for the satellite power system (SPS)

    Energy Technology Data Exchange (ETDEWEB)

    1978-10-01

    A preliminary assessment of the impact of the Satellite Power System (SPS) on the environment is presented. Information that has appeared in documents referenced herein is integrated and assimilated. The state-of-knowledge as perceived from recently completed DOE-sponsored studies is disclosed, and prospective research and study programs that can advance the state-of-knowledge and provide an expanded data base for use in an assessment planned for 1980 are defined. Alternatives for research that may be implemented in order to achieve this advancement are also discussed in order that a plan can be selected which will be consistent with the fiscal and time constraints on the SPS Environmental Assessment Program. Health and ecological effects of microwave radiation, nonmicrowave effects on health and the environment (terrestrial operations and space operations), effects on the atmosphere, and effects on communications systems are examined in detail. (WHK)

  5. A European mobile satellite system concept exploiting CDMA and OBP

    Science.gov (United States)

    Vernucci, A.; Craig, A. D.

    1993-01-01

    This paper describes a novel Land Mobile Satellite System (LMSS) concept applicable to networks allowing access to a large number of gateway stations ('Hubs'), utilizing low-cost Very Small Aperture Terminals (VSAT's). Efficient operation of the Forward-Link (FL) repeater can be achieved by adopting a synchronous Code Division Multiple Access (CDMA) technique, whereby inter-code interference (self-noise) is virtually eliminated by synchronizing orthogonal codes. However, with a transparent FL repeater, the requirements imposed by the highly decentralized ground segment can lead to significant efficiency losses. The adoption of a FL On-Board Processing (OBP) repeater is proposed as a means of largely recovering this efficiency impairment. The paper describes the network architecture, the system design and performance, the OBP functions and impact on implementation. The proposed concept, applicable to a future generation of the European LMSS, was developed in the context of a European Space Agency (ESA) study contract.

  6. The silicon solar satellite power system - A net energy analysis

    Science.gov (United States)

    Hannon, B.; Naughton, J. P.

    The physical aspects and net energy balance of a Satellite Solar Power System (SSPS) are examined. The feasibility of operating with or without laser annealing for the cells, possible variations in the total system costs, the projected worth of the energy, and the R&D costs are explored. The energy needed to mine, refine, fabricate, manufacture, launch, and maintain the SSPS materials and structures are included in the energy analysis, and cost-to-energy ratio of energy used to energy produced graphs are provided for the cases of the use or non-use of laser annealing for radiation protection for the solar cells. The resulting energy ratios indicate that the reference SSPS compares unfavorably with coal or nuclear earth-based plants, although further research is necessary to determine what level of technology is actually required for construction of the SSPS.

  7. NASA ACTS Multibeam Antenna (MBA) System. [Advanced Communications Technology Satellite

    Science.gov (United States)

    Choung, Youn H.; Stiles, W. Herschel; Wu, Joseph; Wong, William C.; Chen, C. Harry

    1986-01-01

    The design of the Advanced Communications Technology Satellite MBA system, which provides both spot beam and scanning beam coverage to both high and low burst rates data-users is examined. The MBA consists of receive and transmit antennas installed on a common precision mounting platform that is integrated to the bus through three flexures; a lightweight system with low thermal distortion is obtained by using composite materials for the MBA structures. The RF design, which is a Cassegrain reflector with a large equivalent focal length/aperture size, is described. Consideration is given to the position of the feed in order to minimize scan loss and sidelobe levels, the size of the subreflector in order to minimize feed spillover, and antenna performance degradation caused by reflector surface distortion. Breadbroad model test result reveal that the maximum sidelobe level outside the 2.5 HPBW region is -30 dB or lower relative to the power.

  8. Satellite-instrument system engineering best practices and lessons

    Science.gov (United States)

    Schueler, Carl F.

    2009-08-01

    This paper focuses on system engineering development issues driving satellite remote sensing instrumentation cost and schedule. A key best practice is early assessment of mission and instrumentation requirements priorities driving performance trades among major instrumentation measurements: Radiometry, spatial field of view and image quality, and spectral performance. Key lessons include attention to technology availability and applicability to prioritized requirements, care in applying heritage, approaching fixed-price and cost-plus contracts with appropriate attention to risk, and assessing design options with attention to customer preference as well as design performance, and development cost and schedule. A key element of success either in contract competition or execution is team experience. Perhaps the most crucial aspect of success, however, is thorough requirements analysis and flowdown to specifications driving design performance with sufficient parameter margin to allow for mistakes or oversights - the province of system engineering from design inception to development, test and delivery.

  9. Onboard Supervisor for the Ørsted Satellite Attitude Control System

    DEFF Research Database (Denmark)

    Bøgh, S.A.; Izadi-Zamanabadi, Roozbeh; Blanke, M.

    1995-01-01

    The increasing operational requirements for onboard autonomy in satellite control systems necessitates structural methods that support the design of a complete and reliable supervisory system.......The increasing operational requirements for onboard autonomy in satellite control systems necessitates structural methods that support the design of a complete and reliable supervisory system....

  10. UAS CNPC Satellite Link Performance - Sharing Spectrum with Terrestrial Systems

    Science.gov (United States)

    Kerczewski, Robert J.; Wilson, Jeffrey D.; Bishop, William D.

    2016-01-01

    In order to provide for the safe integration of unmanned aircraft systems into the National Airspace System, the control and non-payload communications (CNPC) link connecting the ground-based pilot with the unmanned aircraft must be highly reliable. A specific requirement is that it must operate using aviation safety radiofrequency spectrum. The 2012 World Radiocommunication Conference (WRC-12) provided a potentially suitable allocation for radio line-of-sight (LOS), terrestrial based CNPC link at 5030-5091 MHz. For a beyond radio line-of-sight (BLOS), satellite-based CNPC link, aviation safety spectrum allocations are currently inadequate. Therefore, the 2015 WRC will consider the use of Fixed Satellite Service (FSS) bands to provide BLOS CNPC under Agenda Item 1.5. This agenda item requires studies to be conducted to allow for the consideration of how unmanned aircraft can employ FSS for BLOS CNPC while maintaining existing systems. Since there are terrestrial Fixed Service systems also using the same frequency bands under consideration in Agenda Item 1.5 one of the studies required considered spectrum sharing between earth stations on-board unmanned aircraft and Fixed Service station receivers. Studies carried out by NASA have concluded that such sharing is possible under parameters previously established by the International Telecommunications Union. As the preparation for WRC-15 has progressed, additional study parameters Agenda Item 1.5 have been proposed, and some studies using these parameters have been added. This paper examines the study results for the original parameters as well as results considering some of the more recently proposed parameters to provide insight into the complicated process of resolving WRC-15 Agenda Item 1.5 and achieving a solution for BLOS CNPC for unmanned aircraft.

  11. NNIC—neural network image compressor for satellite positioning system

    Science.gov (United States)

    Danchenko, Pavel; Lifshits, Feodor; Orion, Itzhak; Koren, Sion; Solomon, Alan D.; Mark, Shlomo

    2007-04-01

    We have developed an algorithm, based on novel techniques of data compression and neural networks for the optimal positioning of a satellite. The algorithm is described in detail, and examples of its application are given. The heart of this algorithm is the program NNIC—neural network image compressor. This program was developed for compression color and grayscale images with artificial neural networks (ANNs). NNIC applies three different methods for compression. Two of them are based on neural networks architectures—multilayer perceptron and kohonen network. The third is based on a widely used method of discrete cosine transform, the basis for the JPEG standard. The program also serves as a tool for determining numerical and visual quality parameters of compression and comparison between different methods. A number of advantages and disadvantages of the compression using ANNs were discovered in the course of the present research, some of them presented in this report. The thrust of the report is the discussion of ANNs implementation problems for modern platforms, such as a satellite positioning system that include intensive image flowing and processing.

  12. Evaluation of voice codecs for the Australian mobile satellite system

    Science.gov (United States)

    Bundrock, Tony; Wilkinson, Mal

    1990-01-01

    The evaluation procedure to choose a low bit rate voice coding algorithm is described for the Australian land mobile satellite system. The procedure is designed to assess both the inherent quality of the codec under 'normal' conditions and its robustness under 'severe' conditions. For the assessment, normal conditions were chosen to be random bit error rate with added background acoustic noise and the severe condition is designed to represent burst error conditions when mobile satellite channel suffers from signal fading due to roadside vegetation. The assessment is divided into two phases. First, a reduced set of conditions is used to determine a short list of candidate codecs for more extensive testing in the second phase. The first phase conditions include quality and robustness and codecs are ranked with a 60:40 weighting on the two. Second, the short listed codecs are assessed over a range of input voice levels, BERs, background noise conditions, and burst error distributions. Assessment is by subjective rating on a five level opinion scale and all results are then used to derive a weighted Mean Opinion Score using appropriate weights for each of the test conditions.

  13. Satellite lines at the ionization threshold in charge transfer systems

    Science.gov (United States)

    Wardermann, W.; von Niessen, W.

    1992-01-01

    This article deals with the possibility of low-energy ionizations of reduced intensity for larger organic molecules. Possible mechanisms which may lead to this phenomenon are outlined and the necessary structural features are discussed. The lowest ionization energies of some organic unsaturated nitro and nitroso compounds are calculated by the ADC(3) ab initio many-body Green's function method. The π-electron system consists either of fused five- and six-membered rings or of two fused five-membered rings with a variable number of heteroatoms. Some of the molecules contain exocylic double bonds and some are substituted with the donor groups -NH 2, -OH and -NHOH. The strongest many-body effects are found for the nitroso compounds, where in one case the spectral line at the ionization threshold has lost more than 40% of its intensity to satellites. We study the many-body effects at or close to the ionization threshold for these compounds. A particular mechanism which involves the screening of localized valence holes by charge transfer excitations appears to be capable of influencing the profile and intensities of the ionization spectrum already at the ionization threshold. The effect leads to strongly reduced relative intensities of the bands and may cause the appearance of satellite bands nearly at the ionization threshold. The spectral changes in the outermost valence region are discussed by using a simple model calculation in terms of ground-state electronic properties of the molecules.

  14. Development of the European Small Geostationary Satellite SGEO

    Science.gov (United States)

    Lübberstedt, H.; Schneider, A.; Schuff, H.; Miesner, Th.; Winkler, A.

    2008-08-01

    The SGEO product portfolio, ranging from Satellite platform delivery up to in-orbit delivery of a turnkey system including satellite and ground control station, is designed for applications ranging from TV Broadcast to multimedia applications, Internet access, mobile or fixed services in a wide range of frequency bands. Furthermore, Data Relay missions such as the European Data Relay Satellite (EDRS) as well as other institutional missions are targeted. Key design features of the SGEO platform are high flexibility and modularity in order to accommodate a very wide range of future missions, a short development time below two years and the objective to build the system based on ITAR free subsystems and components. The system will provide a long lifetime of up to 15 years in orbit operations with high reliability. SGEO is the first European satellite to perform all orbit control tasks solely by electrical propulsion (EP). This design provides high mass efficiency and the capability for direct injection into geostationary orbit without chemical propulsion (CP). Optionally, an Apogee Engine Module based on CP will provide the perigee raising manoeuvres in case of a launch into geostationary transfer orbit (GTO). This approach allows an ideal choice out of a wide range of launcher candidates in dependence of the required payload capacity. SGEO will offer to the market a versatile and high performance satellite system with low investment risk for the customer and a short development time. This paper provides an overview of the SGEO system key features and the current status of the SGEO programme.

  15. Design and observations of satellite laser ranging system for daylight tracking at Shanghai Observatory

    Institute of Scientific and Technical Information of China (English)

    杨福民; 肖炽昆; 陈婉珍; 张忠萍; 谭德同; 龚向东; 陈菊平; 黄力; 章建华

    1999-01-01

    The first satellite laser ranging system for daylight tracking in China was set up at Shanghai Observatory, Chinese Academy of Sciences. Both false alarm probability due to strong background noises and detection probability of the laser returns with single photon level from satellite in daylight for our system are analysed. The system design and performance characteristics of subsystems, adopted techniques and satellite ranging observations are given.

  16. PS2013 Satellite Workshop on Photosynthetic Light-Harvesting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Niederman, Robert A. [Rutgers Univ., New Brunswick, NJ (United States); Blankenship, Robert E. [Washington Univ., St. Louis, MO (United States); Frank, Harry A. [Univ. of Connecticut, Storrs, CT (United States)

    2015-02-07

    These funds were used for partial support of the PS2013 Satellite Workshop on Photosynthetic Light-Harvesting Systems, that was held on 8-11 August, 2013, at Washington University, St. Louis, MO. This conference, held in conjunction with the 16th International Congress on Photosynthesis/St. Louis, continued a long tradition of light-harvesting satellite conferences that have been held prior to the previous six international photosynthesis congresses. In this Workshop, the basis was explored for the current interest in replacing fossil fuels with energy sources derived form direct solar radiation, coupled with light-driven electron transport in natural photosynthetic systems and how they offer a valuable blueprint for conversion of sunlight to useful energy forms. This was accomplished through sessions on the initial light-harvesting events in the biological conversion of solar energy to chemically stored energy forms, and how these natural photosynthetic processes serve as a guide to the development of robust bio-hybrid and artificial systems for solar energy conversion into both electricity or chemical fuels. Organized similar to a Gordon Research Conference, a lively, informal and collegial setting was established, highlighting the exchange of exciting new data and unpublished results from ongoing studies. A significant amount of time was set aside for open discussion and interactive poster sessions, with a special session devoted to oral presentations by talented students and postdoctoral fellows judged to have the best posters. This area of research has seen exceptionally rapid progress in recent years, with the availability of a number of antenna protein structures at atomic resolution, elucidation of the molecular surface architecture of native photosynthetic membranes by atomic force microscopy and the maturing of ultrafast spectroscopic and molecular biological techniques for the investigation and manipulation of photosynthetic systems. The conferees

  17. Partial relay selection based on shadowing side information over generalized composite fading channels

    KAUST Repository

    Yilmaz, Ferkan

    2011-11-01

    In this paper, in contrast to the relay selection protocols available in the literature, we propose a partial relay selection protocol utilizing only the shadowing side information of the relays instead of their full channel side information in order to select a relay in a dual-hop relaying system through the available limited feedback channels and power budget. We then presented an exact unified performance expression combining the average bit error probability, ergodic capacity, and moments-generating function of the proposed partial relay selection over generalized fading channels. Referring to the unified performance expression introduced in [1], we explicitly offer a generic unified performance expression that can be easily calculated and that is applicable to a wide variety of fading scenarios. Finally, as an illustration of the mathematical formalism, some numerical and simulation results are generated for an extended generalized-K fading environment, and these numerical and simulation results are shown to be in perfect agreement. © 2011 IEEE.

  18. Satellite power system. Concept development and evaluation program

    Energy Technology Data Exchange (ETDEWEB)

    1978-10-01

    The Reference System description emphasizes technical and operational information required in support of environmental, socioeconomic, and comparative assessment studies. Supporting information has been developed according to a guideline of implementing two 5 GW SPS systems per year for 30 years beginning with an initial operational data of 2000 and with SPS's being added at the rate of two per year (10 GW/year) until 2030. The Reference System concept, which features gallium--aluminum--arsenide (GaAlAs) and silicon solar cell options, is described in detail. The concept utilizes a planar solar array (about 55 km/sup 2/) built on a graphite fiber reinforced thermoplastic structure. The silicon array uses a concentration ratio of one (no concentration), whereas the GaAlAs array uses a concentration ratio of two. A one-kilometer diameter phased array microwave antenna is mounted on one end. The antenna uses klystrons as power amplifiers with slotted waveguides as radiating elements. The satellite is constructed in geosynchronous orbit in a six-month period. The ground receiving stations (rectenna) are completed during the same time period. The other two major components of an SPS program are (1) the construction bases in space and launch and mission control bases on earth and (2) fleets of various transportation vehicles that support the construction and maintenance operations of the satellites. These transportation vehicles include Heavy Lift Launch Vehicles (HLLV), Personnel Launch Vehicles (PLV), Cargo Orbit Transfer Vehicles (COTV), and Personnel Orbit Transfer Vehicles (POTV). The earth launch site chosen is the Kennedy Space Center, pending further study.

  19. Satellite Data Assimilation within KIAPS-LETKF system

    Science.gov (United States)

    Jo, Y.; Lee, S., Sr.; Cho, K.

    2016-12-01

    Korea Institute of Atmospheric Prediction Systems (KIAPS) has been developing an ensemble data assimilation system using four-dimensional local ensemble transform kalman filter (LETKF; Hunt et al., 2007) within KIAPS Integrated Model (KIM), referred to as "KIAPS-LETKF". KIAPS-LETKF system was successfully evaluated with various Observing System Simulation Experiments (OSSEs) with NCAR Community Atmospheric Model - Spectral Element (Kang et al., 2013), which has fully unstructured quadrilateral meshes based on the cubed-sphere grid as the same grid system of KIM. Recently, assimilation of real observations has been conducted within the KIAPS-LETKF system with four-dimensional covariance functions over the 6-hr assimilation window. Then, conventional (e.g., sonde, aircraft, and surface) and satellite (e.g., AMSU-A, IASI, GPS-RO, and AMV) observations have been provided by the KIAPS Package for Observation Processing (KPOP). Wind speed prediction was found most beneficial due to ingestion of AMV and for the temperature prediction the improvement in assimilation is mostly due to ingestion of AMSU-A and IASI. However, some degradation in the simulation of the GPS-RO is presented in the upper stratosphere, even though GPS-RO leads positive impacts on the analysis and forecasts. We plan to test the bias correction method and several vertical localization strategies for radiance observations to improve analysis and forecast impacts.

  20. Global Navigation Satellite Systems (GNSS: The Utmost Interdisciplinary Integrator

    Directory of Open Access Journals (Sweden)

    Bernd Eissfeller

    2015-08-01

    Full Text Available Currently four global satellite navigation systems are under modernization and development: The US American GPS III, the Russian GLONASS, the European Galileo and Chinese BeiDou systems. In the paper the interdisciplinary contributions of different scientific areas to GNSS are assessed. It is outlined that GNSS is not only a technical system but also a basic element of mobile computing high-tech market. At the same time a GNSS has the role of a force enabler in security related applications. Technology, market and security policies are interdependent and are sometimes in a relationship of tension. The goal of the paper is to describe the overall systemics of GNSS from a holistic point of view. The paper also addresses the human factor side of GNSS. The requirements on human resources in GNSS are at least two-fold: On the one hand very specialized engineers are needed; on the other hand the generalists are necessary who are able to understand the system aspects. Decision makers in institutions and industry need special knowledge in technologies, economics and political strategies. Is the current university system able to educate and prepare such generalists? Are specialized master courses for GNSS needed? Are external training courses necessary?