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Sample records for bi-directional relay network

  1. Achievable rate regions and outer bounds for a multi-pair bi-directional relay network

    CERN Document Server

    Kim, Sang Joon; Devroye, Natasha

    2010-01-01

    In a bi-directional relay channel, a pair of nodes wish to exchange independent messages over a shared wireless half-duplex channel with the help of relays. Recent work has mostly considered information theoretic limits of the bi-directional relay channel with two terminal nodes (or end users) and one relay. In this work we consider bi-directional relaying with one base station, multiple terminal nodes and one relay, all of which operate in half-duplex modes. We assume that each terminal node communicates with the base-station in a bi-directional fashion through the relay and do not place any restrictions on the channels between the users, relays and base-stations; that is, each node has a direct link with every other node. Our contributions are three-fold: 1) the introduction of four new temporal protocols which fully exploit the two-way nature of the data and outperform simple routing or multi-hop communication schemes by carefully combining network coding, random binning and user cooperation which exploit ...

  2. High-Speed Optical Local Access Network System Using Bi-Directional Polarization Multiplexing

    Institute of Scientific and Technical Information of China (English)

    Mitsuru Miyauchi; Yanjun Sun

    2003-01-01

    A high-speed and economical optical local access network system is proposed where bi-directional polarization multiplexing is applied to a bi-directional transmission. Experimental results using a prototype system confirmlow optical loss and environmental stabilities.

  3. High-Speed Optical Local Access Network System Using Bi-Directional Polarization Multiplexing

    Institute of Scientific and Technical Information of China (English)

    Mitsuru; Miyauchi; Yanjun; Sun

    2003-01-01

    A high-speed and economical optical local access network system is proposed where bi-directional polarization multiplexing is applied to a bi-directional transmission. Experimental results using a prototype system confirm low optical loss and environmental stabilities.

  4. Absolute exponential stability analysis of delayed bi-directional associative memory neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Lou Xuyang [Research Center of Control Science and Engineering, Southern Yangtze University, 1800 Lihu Road, Wuxi, Jiangsu 214122 (China); Cui Baotong [Research Center of Control Science and Engineering, Southern Yangtze University, 1800 Lihu Road, Wuxi, Jiangsu 214122 (China)]. E-mail: btcui@sohu.com

    2007-02-15

    The problem of absolute exponential stability for delayed bi-directional associative memory neural networks with time delay is investigated via Lyapunov stability theory. A new sufficient condition ensuring existence and uniqueness of equilibrium and its absolute exponential stability is derived. An illustrative example is given to demonstrate the effectiveness of the obtained results.

  5. Bi-directional Flooding Protocol for Underwater Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Tariq Ali

    2014-05-01

    Full Text Available Underwater Wireless Sensor Networks (UWSNs are getting more importance in the oceanic exploration. The planet earth is basically a planet of water with less than 30% land mass available for humans to live on. However, the areas covered with water are important to mankind for the various resources which have been proven to be valuable. Such resources are gas, oil, marine products which can be used as food and other minerals. In view of the vast area in which these resources can be found, a network of sensors is necessary so that they can be explored. However, sensor networks may not be helpful in the exploration of these resources if they do not have a sufficiently good routing mechanism. Node mobility, 3-D spaces and horizontal communication links are some critical challenges to the researcher in designing new routing protocols for UWSNs. In this study, we have proposed a novel routing protocol called Layer by Layer Angle-Based Flooding (L2-ABF to address the issues of continuous node movements, end-to-end delays and energy consumption. In L2-ABF, every node can calculate its flooding zone to forward data packets toward the sinks without using any explicit configuration or location information. The simulation results show that L2-ABF has some advantages over some existing flooding-based techniques and also can easily manage quick routing changes where node movements are frequent.

  6. A self-adaptive full asynchronous bi-directional transmission channel for network-on-chips

    International Nuclear Information System (INIS)

    To improve two shortcomings of conventional network-on-chips, i.e. low utilization rate in channels between routers and excessive interconnection lines, this paper proposes a full asynchronous self-adaptive bi-directional transmission channel. It can utilize interconnection lines and register resources with high efficiency, and dynamically detect the data transmission state between routers through a direction regulator, which controls the sequencer to automatically adjust the transmission direction of the bi-directional channel, so as to provide a flexible data transmission environment. Null convention logic units are used to make the circuit quasi-delay insensitive and highly robust. The proposed bi-directional transmission channel is implemented based on SMIC 0.18 μm standard CMOS technology. Post-layout simulation results demonstrate that this self-adaptive bi-directional channel has better performance on throughput, transmission flexibility and channel bandwidth utilization compared to a conventional single direction channel. Moreover, the proposed channel can save interconnection lines up to 30% and can provide twice the bandwidth resources of a single direction transmission channel. The proposed channel can apply to an on-chip network which has limited resources of registers and interconnection lines. (semiconductor integrated circuits)

  7. BI-DIRECTIONAL COHEN-GROSSBERG NEURAL NETWORK WITH DISCRETE TIME

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Discrete-time version of the bi-directional Cohen-Grossberg neural network is stud-ied in this paper. Some sufficient conditions are obtained to ensure the global exponen-tial stability of such networks with discrete time based on Lyapunov method. These results do not require the symmetry of the connection matrix and the monotonicity, boundedness and differentiability of the activation function.

  8. BI-DIRECTIONAL COHEN-GROSSBERG NEURAL NETWORK WITH DISCRETE TIME

    Institute of Scientific and Technical Information of China (English)

    Du Dejun; Chen Anping

    2009-01-01

    Discrete-time version of the bi-directional Cohen-Grossberg neural network is stu-died in this paper. Some sufficient conditions are obtained to ensure the global ex-ponential stability of such" networks with discrete time based on Lyapunov method. These results do not require the symmetry of the connection matrix and the monoto-nicity, boundedness and differentiability of the activation function.

  9. Analysis of global exponential stability for a class of bi-directional associative memory networks

    Institute of Scientific and Technical Information of China (English)

    王宏霞; 何晨

    2003-01-01

    In real-time applications of bi-directional associative memory (BAM) networks, a global exponentially stable equilibrium is highly desired. The existence, uniqueness and global exponential stability for a class of BAM networks are studied in this paper, the signal function of neurons is assumed to be piece-wise linear from the engineering point of view. A very concise condition for the equilibrium of such a network being globally exponentially stable is derived,which makes the practical design of this kind of networks an easy job.

  10. Identifying missing and spurious connections via the bi-directional diffusion on bipartite networks

    Science.gov (United States)

    Zhang, Peng; Zeng, An; Fan, Ying

    2014-06-01

    Link prediction and spurious link detection in complex networks have attracted increasing attention from both physical and computer science communities, due to their wide applications in many real systems. Related previous works mainly focus on monopartite networks while these problems in bipartite networks are not yet systematically addressed. Containing two different kinds of nodes, bipartite networks are essentially different from monopartite networks, especially in node similarity calculation: the similarity between nodes of different kinds (called inter-similarity) is not well defined. In this letter, we employ the local diffusion processes to measure the inter-similarity in bipartite networks. We find that the inter-similarity is asymmetric if the diffusion is applied in different directions. Accordingly, we propose a bi-directional hybrid diffusion method which is shown to achieve higher accuracy than the existing diffusion methods in identifying missing and spurious links in bipartite networks.

  11. Inference of biological networks using Bi-directional Random Forest Granger causality.

    Science.gov (United States)

    Furqan, Mohammad Shaheryar; Siyal, Mohammad Yakoob

    2016-01-01

    The standard ordinary least squares based Granger causality is one of the widely used methods for detecting causal interactions between time series data. However, recent developments in technology limit the utilization of some existing implementations due to the availability of high dimensional data. In this paper, we are proposing a technique called Bi-directional Random Forest Granger causality. This technique uses the random forest regularization together with the idea of reusing the time series data by reversing the time stamp to extract more causal information. We have demonstrated the effectiveness of our proposed method by applying it to simulated data and then applied it to two real biological datasets, i.e., fMRI and HeLa cell. fMRI data was used to map brain network involved in deductive reasoning while HeLa cell dataset was used to map gene network involved in cancer. PMID:27186478

  12. 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.

  13. Handover Framework for Relay Enhanced LTE Networks

    DEFF Research Database (Denmark)

    Teyeb, Oumer Mohammed; Van Phan, Vinh; Raaf, Bernhard;

    2009-01-01

    Relaying is one of the proposed technologies for future releases of UTRAN Long Term Evolution (LTE) networks. Introducing relaying is expected to increase the coverage and capacity of LTE networks. In order to enable relaying, the architecture, protocol and radio resource management procedures...... of LTE, such as handover, have to be modified. A user can be handed over not only between two base stations, but also between relays and base stations, and between two relays. With the introduction of relaying, there is a need for a new procedure to hand over a relay and all its associated users...... to another base station, allowing a flexible and dynamic relay deployment. In this paper, we extend the LTE release 8 handover mechanisms so that it can accommodate these new handover functionalities in a flexible manner....

  14. 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.

  15. Opportunistic Adaptive Relaying in Cognitive Radio Networks

    CERN Document Server

    Jaafar, Wael; Haccoun, David

    2012-01-01

    Combining cognitive radio technology with user cooperation could be advantageous to both primary and secondary transmissions. In this paper, we propose a first relaying scheme for cognitive radio networks (called "Adaptive relaying scheme 1"), where one relay node can assist the primary or the secondary transmission with the objective of improving the outage probability of the secondary transmission with respect to a primary outage probability threshold. Upper bound expressions of the secondary outage probability using the proposed scheme are derived over Rayleigh fading channels. Numerical and simulation results show that the secondary outage probability using the proposed scheme is lower than that of other relaying schemes. Then, we extend the proposed scheme to the case where the relay node has the ability to decode both the primary and secondary signals and also can assist simultaneously both transmissions. Simulations show the performance improvement that can be obtained due to this extension in terms of...

  16. 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.

  17. On Cooperative Relay in Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Donglin Hu

    2013-12-01

    Full Text Available Cognitive radios (CR and cooperative communications represent new paradigms that both can effectively improve the spectrum efficiency of future wireless networks. In this paper, we investigate the problem of cooperative relay in CR networks for further enhanced network performance. We investigate how to effectively integrate these two advanced wireless communications technologies. In particular, we focus on the two representative cooperative relay strategies, decode-and-forward (DF and amplify-and-forward (AF, and develop optimal spectrum sensing and p-Persistent CSMA for spectrum access.We develop an analysis for the comparison of these two relay strategies in the context of CR networks, and derive closed-form expressions for network-wide throughput achieved by DF, AF and direct link transmissions. Our analysis is validated by simulations. We find each of the strategies performs better in a certain parameter range; there is no case of dominance for the two strategies. The significant gaps between the cooperative relay results and the direct link results exemplify the diversity gain achieved by cooperative relays in CR networks.

  18. Threshold-Based Relay Selection for Detect-and-Forward Relaying in Cooperative Wireless Networks

    Directory of Open Access Journals (Sweden)

    Fan Yijia

    2010-01-01

    Full Text Available This paper studies two-hop cooperative demodulate-and-forward relaying using multiple relays in wireless networks. A threshold based relay selection scheme is considered, in which the reliable relays are determined by comparing source-relay SNR to a threshold, and one of the reliable relays is selected by the destination based on relay-destination SNR. The exact bit error rate of this scheme is derived, and a simple threshold function is proposed. It is shown that the network achieves full diversity order ( under the proposed threshold, where is the number of relays in the network. Unlike some other full diversity achieving protocols in the literature, the requirement that the instantaneous/average SNRs of the source-relay links be known at the destination is eliminated using the appropriate SNR threshold.

  19. 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...

  20. Generalized instantly decodable network coding for relay-assisted networks

    KAUST Repository

    Elmahdy, Adel M.

    2013-09-01

    In this paper, we investigate the problem of minimizing the frame completion delay for Instantly Decodable Network Coding (IDNC) in relay-assisted wireless multicast networks. We first propose a packet recovery algorithm in the single relay topology which employs generalized IDNC instead of strict IDNC previously proposed in the literature for the same relay-assisted topology. This use of generalized IDNC is supported by showing that it is a super-set of the strict IDNC scheme, and thus can generate coding combinations that are at least as efficient as strict IDNC in reducing the average completion delay. We then extend our study to the multiple relay topology and propose a joint generalized IDNC and relay selection algorithm. This proposed algorithm benefits from the reception diversity of the multiple relays to further reduce the average completion delay in the network. Simulation results show that our proposed solutions achieve much better performance compared to previous solutions in the literature. © 2013 IEEE.

  1. Compute-and-forward: multiple bi-directional sessions on the line network

    NARCIS (Netherlands)

    Ren, Zhijie; Goseling, Jasper; Weber, Jos H.; Gastpar, Michael

    2013-01-01

    Signal superposition and broadcast are important features of the wireless medium. Compute-and-Forward, also known as Physical Layer Network Coding, is a technique exploiting these features in order to improve performance of wireless networks. In this paper, the possible benefits for the line network

  2. Optimization of the relay selection scheme in cooperative retransmission networks

    OpenAIRE

    He, Xin; Li, Frank Yong

    2011-01-01

    Cooperative MAC protocol design has attracted much attention recently thanks to the development of relaying techniques. In single-relay C-ARQ, the relay selection scheme cannot work efficiently in a dense network, due to high collision probability among different contending relays. In this paper, the throughput performance impairment from the collision is analyzed in a typical network scenario. Thereby, we propose an optimized relay selection scheme aiming at maximizing system throughput by r...

  3. Robust Transmission for Cognitive Relay Networks

    Institute of Scientific and Technical Information of China (English)

    Cao Zhigang; Wang Jianyu; Liu Juan; Wang Xijun; Chen Wei

    2012-01-01

    In cognitive relay networks, the transmission of Secondary Users (SUs) suffers from the activity of Primary Users (PUs) and wireless channel fading. Therefore, how to achieve robust transmission for cognitive relay networks is a challenging task. In this paper, we propose a relaying transmission scheme which exploits robust beamforming at the physical layer and rateless codes at higher layers. We derive the optirml beamforng weight vector and analyze the perforrmnce of the pro- posed scheme when the channel estirmtion is not accurate between two SU nodes. We also study how the anaount of channel information between SU and PU impacts the system perforroance. Sinlation results validate our theoretical analysis and demonstrate that the proposed scheme can signifi- cantly enhance the system throughput.

  4. Time of arrival based location estimation for cooperative relay networks

    KAUST Repository

    Çelebi, Hasari Burak

    2010-09-01

    In this paper, we investigate the performance of a cooperative relay network performing location estimation through time of arrival (TOA). We derive Cramer-Rao lower bound (CRLB) for the location estimates using the relay network. The analysis is extended to obtain average CRLB considering the signal fluctuations in both relay and direct links. The effects of the channel fading of both relay and direct links and amplification factor and location of the relay node on average CRLB are investigated. Simulation results show that the channel fading of both relay and direct links and amplification factor and location of relay node affect the accuracy of TOA based location estimation. ©2010 IEEE.

  5. A Bi-directional Energy Splitable Model for Energy Optimization in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    A. Rajeswari

    2011-01-01

    Full Text Available Wireless Sensor Networks is a budding  prototype of networking and computing, where a node may be self powered and individual node have the capability to sense and compute and communicate. Wireless Sensor Networks have been proposed for variety of applications such as Industrial control and monitoring and home automation and consumer electronics and security andMilitary sensing, Asset tracking and supply chain management, Intelligent Agriculture, Missile directing, Fire alarming, Landslide Warning, Environmental monitoring and health monitoring and commercial applications. In Wireless Sensor Network large number of nodes are deployed randomly. Depends on the network architecture the application may be personalized such as Energy Efficiency, Routing and Power Management and data dissemination. Energy Optimization involves in minimizing an energy expenditure and maximizing the lifetime of the complete network. In the proposed work, the placement of nodes are directly involved with residual energy. Energy Optimization in sensor network is very difficult task to achieve it. The optimization of energy is performed through Bidirectional Energy Splitable Model. The data flow in both forward and backward directions are considered, In order to achieve the best QOS in transmission, some parameters such as load, delay and direction of individual nodes are considered. A mathematical model is developed to determine the data flow of  individual node based on the residual energy.

  6. Linear beamformer schemes with simple relay selection in MIMO relay networks

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This article considers a wireless multi-hop/mesh network where single multi-antenna source-destination pair communicates through a selected relay subset using simple relay selection under the constraint of fixed relay's number. Compared with random selection, the simple relay selection can yield certain capacity advantages while linear zero-forcing (ZF) receiver and linear beamformer are considered at the relay. For match-filter (MF) beamformer and amplified-and-forward (AF) beamformer with a fixed number of relays, the capacities are given. Furthermore, we extend the simple selection methods to the relaying scheme with orthogonal-triangular (QR) beamformer and investigate these linear beamformer schemes over spatially correlated multi-input multi-output (MIMO) links for both the backward and forward channel over the two-hop MIMO relay networks.

  7. RELAY ALGORITHM BASED ON NETWORK CODING IN WIRELESS LOCAL NETWORK

    Institute of Scientific and Technical Information of China (English)

    Wang Qi; Wang Qingshan; Wang Dongxue

    2013-01-01

    The network coding is a new technology in the field of information in 21st century.It could enhance the network throughput and save the energy consumption,and is mainly based on the single transmission rate.However,with the development of wireless network and equipment,wireless local network MAC protocols have already supported the multi-rate transmission.This paper investigates the optimal relay selection problem based on network coding.Firstly,the problem is formulated as an optimization problem.Moreover,a relay algorithm based on network coding is proposed and the transmission time gain of our algorithm over the traditional relay algorithm is analyzed.Lastly,we compare total transmission time and the energy consumption of our proposed algorithm,Network Coding with Relay Assistance (NCRA),Transmission Request (TR),and the Direct Transmission (DT) without relay algorithm by adopting IEEE 802.11b.The simulation results demonstrate that our algorithm that improves the coding opportunity by the cooperation of the relay nodes leads to the transmission time decrease of up to 17% over the traditional relay algorithms.

  8. Relay Selection and Resource Allocation in One-Way and Two-Way Cognitive Relay Networks

    KAUST Repository

    Alsharoa, Ahmad M.

    2013-05-08

    In this work, the problem of relay selection and resource power allocation in one- way and two-way cognitive relay networks using half duplex channels with different relaying protocols is investigated. Optimization problems for both single and multiple relay selection that maximize the sum rate of the secondary network without degrading the quality of service of the primary network by respecting a tolerated interference threshold were formulated. Single relay selection and optimal power allocation for two-way relaying cognitive radio networks using decode-and-forward and amplify-and-forward protocols were studied. Dual decomposition and subgradient methods were used to find the optimal power allocation. The transmission process to exchange two different messages between two transceivers for two-way relaying technique takes place in two time slots. In the first slot, the transceivers transmit their signals simultaneously to the relay. Then, during the second slot the relay broadcasts its signal to the terminals. Moreover, improvement of both spectral and energy efficiency can be achieved compared with the one-way relaying technique. As an extension, a multiple relay selection for both one-way and two-way relaying under cognitive radio scenario using amplify-and-forward were discussed. A strong optimization tool based on genetic and iterative algorithms was employed to solve the 
formulated optimization problems for both single and multiple relay selection, where discrete relay power levels were considered. Simulation results show that the practical and low-complexity heuristic approaches achieve almost the same performance of the optimal relay selection schemes either with discrete or continuous power distributions while providing a considerable saving in terms of computational complexity.

  9. Dynamic Relaying in 3GPP LTE-Advanced Networks

    Directory of Open Access Journals (Sweden)

    Van Phan Vinh

    2009-01-01

    Full Text Available Relaying is one of the proposed technologies for LTE-Advanced networks. In order to enable a flexible and reliable relaying support, the currently adopted architectural structure of LTE networks has to be modified. In this paper, we extend the LTE architecture to enable dynamic relaying, while maintaining backward compatibility with LTE Release 8 user equipments, and without limiting the flexibility and reliability expected from relaying. With dynamic relaying, relays can be associated with base stations on a need basis rather than in a fixed manner which is based only on initial radio planning. Proposals are also given on how to further improve a relay enhanced LTE network by enabling multiple interfaces between the relay nodes and their controlling base stations, which can possibly be based on technologies different from LTE, so that load balancing can be realized. This load balancing can be either between different base stations or even between different networks.

  10. Dynamic Relaying in 3GPP LTE-Advanced Networks

    DEFF Research Database (Denmark)

    Teyeb, Oumer Mohammed; Van Phan, Vinh; Redana, Simone;

    2009-01-01

    Relaying is one of the proposed technologies for LTE-Advanced networks. In order to enable a flexible and reliable relaying support, the currently adopted architectural structure of LTE networks has to be modified. In this paper, we extend the LTE architecture to enable dynamic relaying, while....... Proposals are also given on how to further improve a relay enhanced LTE network by enabling multiple interfaces between the relay nodes and their controlling base stations, which can possibly be based on technologies different from LTE, so that load balancing can be realized. This load balancing can...... be either between different base stations or even between different networks....

  11. 47 CFR 11.20 - State Relay Network.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false State Relay Network. 11.20 Section 11.20... Network. This network is composed of State Relay (SR) sources, leased common carrier communications facilities or any other available communication facilities. The network distributes State EAS...

  12. 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.

  13. Performance Analysis of Relay Subset Selection for Amplify-and-Forward Cognitive Relay Networks

    Directory of Open Access Journals (Sweden)

    Kiran Sultan

    2014-01-01

    Full Text Available Cooperative communication is regarded as a key technology in wireless networks, including cognitive radio networks (CRNs, which increases the diversity order of the signal to combat the unfavorable effects of the fading channels, by allowing distributed terminals to collaborate through sophisticated signal processing. Underlay CRNs have strict interference constraints towards the secondary users (SUs active in the frequency band of the primary users (PUs, which limits their transmit power and their coverage area. Relay selection offers a potential solution to the challenges faced by underlay networks, by selecting either single best relay or a subset of potential relay set under different design requirements and assumptions. The best relay selection schemes proposed in the literature for amplify-and-forward (AF based underlay cognitive relay networks have been very well studied in terms of outage probability (OP and bit error rate (BER, which is deficient in multiple relay selection schemes. The novelty of this work is to study the outage behavior of multiple relay selection in the underlay CRN and derive the closed-form expressions for the OP and BER through cumulative distribution function (CDF of the SNR received at the destination. The effectiveness of relay subset selection is shown through simulation results.

  14. Performance analysis of relay subset selection for amplify-and-forward cognitive relay networks.

    Science.gov (United States)

    Sultan, Kiran; Qureshi, Ijaz Mansoor; Malik, Aqdas Naveed; Zubair, Muhammad

    2014-01-01

    Cooperative communication is regarded as a key technology in wireless networks, including cognitive radio networks (CRNs), which increases the diversity order of the signal to combat the unfavorable effects of the fading channels, by allowing distributed terminals to collaborate through sophisticated signal processing. Underlay CRNs have strict interference constraints towards the secondary users (SUs) active in the frequency band of the primary users (PUs), which limits their transmit power and their coverage area. Relay selection offers a potential solution to the challenges faced by underlay networks, by selecting either single best relay or a subset of potential relay set under different design requirements and assumptions. The best relay selection schemes proposed in the literature for amplify-and-forward (AF) based underlay cognitive relay networks have been very well studied in terms of outage probability (OP) and bit error rate (BER), which is deficient in multiple relay selection schemes. The novelty of this work is to study the outage behavior of multiple relay selection in the underlay CRN and derive the closed-form expressions for the OP and BER through cumulative distribution function (CDF) of the SNR received at the destination. The effectiveness of relay subset selection is shown through simulation results. PMID:24737980

  15. Relay Selection Scheme for AF Relay Network based on Cost Function Criterion

    Directory of Open Access Journals (Sweden)

    Kanghee Lee

    2013-10-01

    Full Text Available An amplify-and-forward (AF wireless relay network consisting of a one-source-one-destination node pair and cooperative multiple N relay nodes is proposed in three adverse wireless communication environments, i.e., jamming, node geometry, and channel uncertainty. Based on the minimum mean square error (MMSE criterion, the optimal amplifying relay matrix in three adverse wireless environments with the relay power constraint is derived. In addition, the MMSE cost function behavior in three adverse environments is analytically investigated using the proposed optimal relay amplifying matrix. Finally, using the cost function value, the relay selection scheme in adverse wireless communication environments is presented, which is the main contribution of this paper

  16. Joint Uplink and Downlink Relay Selection in Cooperative Cellular Networks

    CERN Document Server

    Yang, Wei; Wu, Gang; Wang, Haifeng; Wang, Ying

    2010-01-01

    We consider relay selection technique in a cooperative cellular network where user terminals act as mobile relays to help the communications between base station (BS) and mobile station (MS). A novel relay selection scheme, called Joint Uplink and Downlink Relay Selection (JUDRS), is proposed in this paper. Specifically, we generalize JUDRS in two key aspects: (i) relay is selected jointly for uplink and downlink, so that the relay selection overhead can be reduced, and (ii) we consider to minimize the weighted total energy consumption of MS, relay and BS by taking into account channel quality and traffic load condition of uplink and downlink. Information theoretic analysis of the diversity-multiplexing tradeoff demonstrates that the proposed scheme achieves full spatial diversity in the quantity of cooperating terminals in this network. And numerical results are provided to further confirm a significant energy efficiency gain of the proposed algorithm comparing to the previous best worse channel selection an...

  17. Generalized routing protocols for multihop relay networks

    KAUST Repository

    Khan, Fahd Ahmed

    2011-07-01

    Performance of multihop cooperative networks depends on the routing protocols employed. In this paper we propose the last-n-hop selection protocol, the dual path protocol, the forward-backward last-n-hop selection protocol and the forward-backward dual path protocol for the routing of data through multihop relay networks. The average symbol error probability performance of the schemes is analysed by simulations. It is shown that close to optimal performance can be achieved by using the last-n-hop selection protocol and its forward-backward variant. Furthermore we also compute the complexity of the protocols in terms of number of channel state information required and the number of comparisons required for routing the signal through the network. © 2011 IEEE.

  18. 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.

  19. Spectral efficiency enhancement with interference cancellation for wireless relay network

    DEFF Research Database (Denmark)

    Yomo, Hiroyuki; De Carvalho, Elisabeth

    The introduction of relaying into wireless communication system for coverage enhancement can cause severe decrease of spectral efficiency due to the requirement on extra radio resource. In this paper, we propose a method to increase spectral efficiency in such a wireless relay network by employing...... distance of identical radio resource. We analyze a simple scenario with BS, single RS, and 2 MSs, and show that the proposed method has significant potential to enhance spectral efficiency in wireless relay networks....

  20. Energy and Throughput Optimization for Relay Based Heterogeneous Networks

    OpenAIRE

    Ouni, Anis; Saadani, Ahmed; Rivano, Hervé

    2013-01-01

    High data rate is a challenge for the next generation cellular networks. This objective needs a significant densification of relay nodes within macro cell. In the LTE-Advanced network, multi-hop relaying has been taken as a promising key technique to provide high throughput to the users and to improve the area coverage. Besides, minimizing the energy consumption and electromagnetic pollution is an economic challenge for the operators. This paper is focused on relay based heterogeneous cellula...

  1. Relay selection for multiple access relay channel with decode-forward and analog network coding

    CERN Document Server

    Hassan, Ahmed Hassan M; Huang, Benxiong; Eisa, Edriss; Azhar, Muhammad

    2012-01-01

    This paper presents a relay selection for decode-and-forward based on network coding (DF-NC) and analog-NC protocols in general scheme of cellular network system. In the propose scheme the two source node simultaneously transmit their own information to all the relays as well as the destination node, and then, a single relay i.e. best with a minimum symbol error rate (SER) will be selected to forward the new version of the received signal. Simulation results show that, the DF-NC scheme with considerable performance has exactness over analog-NC scheme. To improve the system performance, optimal power allocation between the two sources and the best relay is determined based on the asymptotic SER. By increasing the number of relays node, the optimum power allocation achieve better performance than asymptotic SER.

  2. Degrees of Freedom of Multi-Source Relay Networks

    CERN Document Server

    Jeon, Sang-Woon; Jafar, Syed A

    2009-01-01

    We study a multi-source Gaussian relay network consisting of $K$ source--destination pairs having $K$ unicast sessions. We assume $M$ layers of relays between the sources and the destinations. We find achievable degrees of freedom of the network. Our schemes are based on interference alignment at the transmitters and symbol extension and opportunistic interference cancellation at the relays. For $K$-$L$-$K$ networks, i.e., 2-hop network with $L$ relays, we show $\\min\\{K,K/2+L/(2(K-1))\\}$ degrees of freedom are achievable. For $K$-hop networks with $K$ relays in each layer, we show the full $K$ degrees of freedom are achievable provided that $K$ is even and the channel distribution satisfies a certain symmetry.

  3. 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

  4. Asymmetric Modulation Gains in Network Coded Relay Networks

    DEFF Research Database (Denmark)

    Roetter, Daniel Enrique Lucani; Fitzek, Frank

    2015-01-01

    –to–end throughput by (i) using network coding to control the use of the relay in an effective manner, and (ii) leveraging asymmetric modulation to enable the source to efficiently allocate its resources. We provide mathematical analysis and a simple optimization mechanism. Numerical results for the case of fading...

  5. A genetic algorithm for multiple relay selection in two-way relaying cognitive radio networks

    KAUST Repository

    Alsharoa, Ahmad M.

    2013-09-01

    In this paper, we investigate a multiple relay selection scheme for two-way relaying cognitive radio networks where primary users and secondary users operate on the same frequency band. More specifically, cooperative relays using Amplifyand- Forward (AF) protocol are optimally selected to maximize the sum rate of the secondary users without degrading the Quality of Service (QoS) of the primary users by respecting a tolerated interference threshold. A strong optimization tool based on genetic algorithm is employed to solve our formulated optimization problem where discrete relay power levels are considered. Our simulation results show that the practical heuristic approach achieves almost the same performance of the optimal multiple relay selection scheme either with discrete or continuous power distributions. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.

  6. Optimal Relay Selection with Channel Probing in Wireless Sensor Networks

    CERN Document Server

    Naveen, K P

    2011-01-01

    Motivated by the problem of distributed geographical packet forwarding in a wireless sensor network with sleep-wake cycling nodes, we propose a local forwarding model comprising a node that wishes to forward a packet towards a destination, and a set of next-hop relay nodes, each of which is associated with a reward that summarises the cost/benefit of forwarding the packet through that relay. The relays wake up at random times, at which instants they reveal only the probability distributions of their rewards (e.g., by revealing their locations). To determine a relay's exact reward, the forwarding node has to further probe the relay, incurring a probing cost. Thus, at each relay wake-up instant, the source, given a set of relay reward distributions, has to decide whether to stop (and forward the packet to an already probed relay), continue waiting for further relays to wake-up, or probe an unprobed relay. We formulate the problem as a Markov decision process, with the objective being to minimize the packet forw...

  7. Multiantenna relay beamforming design for QoS discrimination in two-way relay networks.

    Science.gov (United States)

    Xiong, Ke; Zhang, Yu; Li, Dandan; Chang, Chih-Yung; Zhong, Zhangdui

    2013-01-01

    This paper investigates the relay beamforming design for quality of service (QoS) discrimination in two-way relay networks. The purpose is to keep legitimate two-way relay users exchange their information via a helping multiantenna relay with QoS guarantee while avoiding the exchanged information overhearing by unauthorized receiver. To this end, we propose a physical layer method, where the relay beamforming is jointly designed with artificial noise (AN) which is used to interfere in the unauthorized user's reception. We formulate the joint beamforming and AN (BFA) design into an optimization problem such that the received signal-to-interference-ratio (SINR) at the two legitimate users is over a predefined QoS threshold while limiting the received SINR at the unauthorized user which is under a certain secure threshold. The objective of the optimization problem is to seek the optimal AN and beamforming vectors to minimize the total power consumed by the relay node. Since the optimization problem is nonconvex, we solve it by using semidefinite program (SDP) relaxation. For comparison, we also study the optimal relay beamforming without using AN (BFO) under the same QoS discrimination constraints. Simulation results show that both the proposed BFA and BFO can achieve the QoS discrimination of the two-way transmission. However, the proposed BFA yields significant power savings and lower infeasible rates compared with the BFO method.

  8. Performance of a Cognitive Relay Network under AF Relay Selection Scheme with Imperfect Channel Estimation

    Directory of Open Access Journals (Sweden)

    B. Prasad

    2016-06-01

    Full Text Available In this paper outage performance of a secondary user (SU is evaluated under amplify and forward (AF relay selection scheme with an imperfect channel state information (CSIwhile sharing spectrum in an underlay cognitive radio network (CRN. In underlay, the SU coexists with primary user (PU in the same band provided the interference produced by SU at the PU receiver is below the interference threshold of PU which limits the transmission power of SU and coverage area. Relays help to improve the performance of SU in underlay. However relays are also constrained in transmit power due to interference constraint imposed by PU. Closed form expression of the outage probability of SU with maximum transmit power constraint of relay under imperfect CSI is derived. A scaling factor based power control is used for the SU transmitter and the relay in order to maintain the interference constraint at PU receiver due to imperfect CSI. The impact of different parameters viz. correlation coefficient, channel estimation error, tolerable interference threshold, number of relays and the maximum transmit power constraint of relay on SU performance is investigated. A MATLAB based test bed has also been developed to carry out simulation in order to validate the theoretical result.

  9. Balanced energy-efficient relay selection scheme in wireless mobile relay networks

    Institute of Scientific and Technical Information of China (English)

    Liu Wei; Ji Hong; Li Xi

    2010-01-01

    In order to resolve the relay selection problem in wireless mobile relay networks (WMRNs), a novel balanced energy-efficient mobile relay selection scheme is proposed in this paper.Compared with traditional counter-based algorithm, distance and energy consumption are considered from network respect to provide a better network lifetime performance in the proposed scheme.Also, it performs well when nodes move freely at high speed.A random assessment delay (RAD) mechanism is added to avoid collisions and improve transmission efficiency.Simulation results reveal that, the proposed scheme has advantages in prolonging network lifetime, balancing energy consumption and reducing the total energy consumption compared with existing counter-based scheme.

  10. An RSS based location estimation technique for cognitive relay networks

    KAUST Repository

    Qaraqe, Khalid A.

    2010-11-01

    In this paper, a received signal strength (RSS) based location estimation method is proposed for a cooperative wireless relay network where the relay is a cognitive radio. We propose a method for the considered cognitive relay network to determine the location of the source using the direct and the relayed signal at the destination. We derive the Cramer-Rao lower bound (CRLB) expressions separately for x and y coordinates of the location estimate. We analyze the effects of cognitive behaviour of the relay on the performance of the proposed method. We also discuss and quantify the reliability of the location estimate using the proposed technique if the source is not stationary. The overall performance of the proposed method is presented through simulations. ©2010 IEEE.

  11. Relay Precoder Optimization in MIMO-Relay Networks With Imperfect CSI

    KAUST Repository

    Ubaidulla, P.

    2011-11-01

    In this paper, we consider robust joint designs of relay precoder and destination receive filters in a nonregenerative multiple-input multiple-output (MIMO) relay network. The network consists of multiple source-destination node pairs assisted by a MIMO-relay node. The channel state information (CSI) available at the relay node is assumed to be imperfect. We consider robust designs for two models of CSI error. The first model is a stochastic error (SE) model, where the probability distribution of the CSI error is Gaussian. This model is applicable when the imperfect CSI is mainly due to errors in channel estimation. For this model, we propose robust minimum sum mean square error (SMSE), MSE-balancing, and relay transmit power minimizing precoder designs. The next model for the CSI error is a norm-bounded error (NBE) model, where the CSI error can be specified by an uncertainty set. This model is applicable when the CSI error is dominated by quantization errors. In this case, we adopt a worst-case design approach. For this model, we propose a robust precoder design that minimizes total relay transmit power under constraints on MSEs at the destination nodes. We show that the proposed robust design problems can be reformulated as convex optimization problems that can be solved efficiently using interior-point methods. We demonstrate the robust performance of the proposed design through simulations. © 2011 IEEE.

  12. Optimal relay selection and power allocation for cognitive two-way relaying networks

    KAUST Repository

    Pandarakkottilil, Ubaidulla

    2012-06-01

    In this paper, we present an optimal scheme for power allocation and relay selection in a cognitive radio network where a pair of cognitive (or secondary) transceiver nodes communicate with each other assisted by a set of cognitive two-way relays. The secondary nodes share the spectrum with a licensed primary user (PU), and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. We propose joint relay selection and optimal power allocation among the secondary user (SU) nodes achieving maximum throughput under transmit power and PU interference constraints. A closed-form solution for optimal allocation of transmit power among the SU transceivers and the SU relay is presented. Furthermore, numerical simulations and comparisons are presented to illustrate the performance of the proposed scheme. © 2012 IEEE.

  13. 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

    This paper analyzes the potential uplink capacity gains of a two-hop 802.16J relay network operating in transparent mode. Detailed channel models and adaptive modulation and coding (AMC) in the physical layer are developed. To mitigate the capacity loss due to multihop communications, multi......-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......-to-end spectral efficiency. Furthermore, the position and the number of relay stations (RSs) have a great impact on the capacity gain. These results are further verified in the evaluation of the system Erlang capacity. The study demonstrates that with proper deployment of RSs and use of MIMO transmission in the...

  14. 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.

  15. On Diversity-Multiplexing Tradeoff in Multiple-Relay Networks

    CERN Document Server

    Gharan, Shahab Oveis; Khandani, Amir K

    2008-01-01

    This paper studies the setup of a multiple-relay network in which $K$ half-duplex multiple-antenna relays assist in the transmission between a/several multiple-antenna transmitter(s) and a multiple-antenna receiver. Each two nodes are assumed to be either connected through a quasi-static Rayleigh fading channel, or disconnected. We propose a new scheme, which we call random sequential (RS), based on the amplify-and-forward relaying. We prove that for general multiple-antenna multiple-relay networks, the proposed scheme achieves the maximum diversity gain. Furthermore, we derive diversity-multiplexing tradeoff (DMT) of the proposed RS scheme for general single-antenna multiple-relay networks. Finally, we show that for single-antenna multiple-access multiple-relay ($K>1$) networks (without direct link between the transmitter(s) and the receiver), the proposed RS scheme achieves the optimum DMT. However, for the case of multiple access single relay setup, the RS scheme reduces to the naive amplify-and-forward re...

  16. Diversity Multiplexing Tradeoff of Asynchronous Cooperative Relay Networks

    CERN Document Server

    Krishnakumar, R N; Kumar, P Vijay

    2008-01-01

    The assumption of nodes in a cooperative communication relay network operating in synchronous fashion is often unrealistic. In the present paper, we consider two different models of asynchronous operation in cooperative-diversity networks experiencing slow fading and examine the corresponding diversity-multiplexing tradeoffs (DMT). For both models, we propose protocols and distributed space-time codes that asymptotically achieve the transmit diversity bound for all multiplexing gains and for any number of relays.

  17. 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.

  18. A digital interface for Gaussian relay networks: lifting codes from the discrete superposition model to Gaussian relay networks

    CERN Document Server

    Anand, M

    2010-01-01

    For every Gaussian relay network with a single source-destination pair, it is known that there exists a corresponding deterministic network called the discrete superposition network that approximates its capacity uniformly over all SNR's to within a bounded number of bits. The next step in this program of rigorous approximation is to determine whether coding schemes for discrete superposition models can be lifted to Gaussian relay networks with a bounded rate loss independent of SNR. We establish precisely this property and show that the superposition model can thus serve as a strong surrogate for designing codes for Gaussian relay networks. We show that a code for a Gaussian relay network, with a single source-destination pair and multiple relay nodes, can be designed from any code for the corresponding discrete superposition network simply by pruning it. In comparison to the rate of the discrete superposition network's code, the rate of the Gaussian network's code only reduces at most by a constant that is ...

  19. Network Code Design for Orthogonal Two-hop Network with Broadcasting Relay: A Joint Source-Channel-Network Coding Approach

    OpenAIRE

    Joda, Roghayeh; Lahouti, Farshad

    2010-01-01

    This paper addresses network code design for robust transmission of sources over an orthogonal two-hop wireless network with a broadcasting relay. The network consists of multiple sources and destinations in which each destination, benefiting the relay signal, intends to decode a subset of the sources. Two special instances of this network are orthogonal broadcast relay channel and the orthogonal multiple access relay channel. The focus is on complexity constrained scenarios, e.g., for wirele...

  20. Cooperative Transmission for a Vector Gaussian Parallel Relay Network

    CERN Document Server

    Kim, Muryong

    2009-01-01

    In this paper, we consider a parallel relay network where two relays cooperatively help a source transmit to a destination. We assume the source and the destination nodes are equipped with multiple antennas. Three basic schemes and their achievable rates are studied: Decode-and-Forward (DF), Amplify-and-Forward (AF), and Compress-and-Forward (CF). For the DF scheme, the source transmits two private signals, one for each relay, where dirty paper coding (DPC) is used between the two private streams, and a common signal for both relays. The relays make efficient use of the common information to introduce a proper amount of correlation in the transmission to the destination. We show that the DF scheme achieves the capacity under certain conditions. We also show that the CF scheme is asymptotically optimal in the high relay power limit, regardless of channel ranks. It turns out that the AF scheme also achieves the asymptotic optimality but only when the relays-to-destination channel is full rank. The relative adva...

  1. Opportunistic Wireless Relay Networks: Diversity-Multiplexing Tradeoff

    CERN Document Server

    Abouelseoud, Mohamed

    2011-01-01

    Opportunistic analysis has traditionally relied on independence assumptions that break down in many interesting and useful network topologies. This paper develops techniques that expand opportunistic analysis to a broader class of networks, proposes new opportunistic methods for several network geometries, and analyzes them in the high-SNR regime. For each of the geometries studied in the paper, we analyze the opportunistic DMT of several relay protocols, including amplify-and-forward, decode-and-forward, compress-and-forward, non-orthogonal amplify-forward, and dynamic decode-forward. Among the highlights of the results: in a variety of multi-user single-relay networks, simple selection strategies are developed and shown to be DMT-optimal. It is shown that compress-forward relaying achieves the DMT upper bound in the opportunistic multiple-access relay channel as well as in the opportunistic nxn user network with relay. Other protocols, e.g. dynamic decode-forward, are shown to be near optimal in several cas...

  2. Coarse Network Coding: A Simple Relay Strategy to Resolve Interference

    CERN Document Server

    Razaghi, Peyman

    2010-01-01

    Reminiscent of the parity function in network coding for the butterfly network, it is shown that forwarding an even/odd indicator bit for a scalar quantization of a relay observation recovers 1 bit of information at the two destinations in a noiseless interference channel where interference is treated as noise. Based on this observation, a coding strategy is proposed to improve the rate of both users at the same time using a relay node in an interference channel. In this strategy, the relay observes a linear combination of the two source signals, and broadcasts a common message to the two destinations over a shared out-of-band link of rate R0 bits per channel use. The relay message consists of the bin index of a structured binning scheme obtained from a 2^R0-way partition of the squared lattice in the complex plane. We show that such scalar quantization-binning relay strategy asymptotically achieves the cut-set bound in an interference channel with a common out-of-band relay link of limited rate, improving th...

  3. Selection combining for noncoherent decode-and-forward relay networks

    Directory of Open Access Journals (Sweden)

    Nguyen Ha

    2011-01-01

    Full Text Available Abstract This paper studies a new decode-and-forward relaying scheme for a cooperative wireless network composed of one source, K relays, and one destination and with binary frequency-shift keying modulation. A single threshold is employed to select retransmitting relays as follows: a relay retransmits to the destination if its decision variable is larger than the threshold; otherwise, it remains silent. The destination then performs selection combining for the detection of transmitted information. The average end-to-end bit-error-rate (BER is analytically determined in a closed-form expression. Based on the derived BER, the problem of choosing an optimal threshold or jointly optimal threshold and power allocation to minimize the end-to-end BER is also investigated. Both analytical and simulation results reveal that the obtained optimal threshold scheme or jointly optimal threshold and power-allocation scheme can significantly improve the BER performance compared to a previously proposed scheme.

  4. Relay Selection and Performance Analysis in Multiple-User Networks

    CERN Document Server

    Atapattu, Saman; Jiang, Hai; Tellambura, Chintha

    2011-01-01

    This paper investigates the relay selection (RS) problem in networks with multiple users and multiple common amplify-and-forward (AF) relays. Considering the overall quality-of-service of the network, we first specify our definition of optimal RS for multiple-user relay networks. Then an optimal RS (ORS) algorithm is provided, which is a straightforward extension of an RS scheme in the literature that maximizes the minimum end-to-end receive signal-to-noise ratio (SNR) of all users. The complexity of the ORS is quadratic in both the number of users and the number of relays. Then a suboptimal RS (SRS) scheme is proposed, which has linear complexity in the number of relays and quadratic complexity in the number of users. Furthermore, diversity orders of both the ORS and the proposed SRS are theoretically derived and compared with those of a naive RS scheme and the single-user RS network. It is shown that the ORS achieves full diversity; while the diversity order of the SRS decreases with the the number of users...

  5. Network Code Design for Orthogonal Two-hop Network with Broadcasting Relay: A Joint Source Channel Network Coding Approach

    CERN Document Server

    Joda, Roghayeh

    2010-01-01

    This paper addresses network code design for robust transmission of sources over an orthogonal two-hop wireless network with a broadcasting relay. The network consists of multiple sources and destinations in which each destination, benefiting the relay signal, intends to decode a subset of the sources. Two special instances of this network are orthogonal broadcast relay channel and the orthogonal multiple access relay channel. The focus is on complexity constrained scenarios, e.g., for wireless sensor networks, where channel coding is practically imperfect. Taking a source-channel and network coding approach, we design the code (mapping) at the relay such that the average reconstruction distortion at the destinations is minimized. To this end, by decomposing the source and channel-network distortions, an efficient design algorithm is proposed. The resulting network code at the relay is nonlinear and substantially outperforms the best performing linear network code at the relay. A motivating formulation of a f...

  6. Joint opportunistic scheduling and network coding for bidirectional relay channel

    KAUST Repository

    Shaqfeh, Mohammad

    2013-07-01

    In this paper, we consider a two-way communication system in which two users communicate with each other through an intermediate relay over block-fading channels. We investigate the optimal opportunistic scheduling scheme in order to maximize the long-term average transmission rate in the system assuming symmetric information flow between the two users. Based on the channel state information, the scheduler decides that either one of the users transmits to the relay, or the relay transmits to a single user or broadcasts to both users a combined version of the two users\\' transmitted information by using linear network coding. We obtain the optimal scheduling scheme by using the Lagrangian dual problem. Furthermore, in order to characterize the gains of network coding and opportunistic scheduling, we compare the achievable rate of the system versus suboptimal schemes in which the gains of network coding and opportunistic scheduling are partially exploited. © 2013 IEEE.

  7. Outage analysis for underlay relay-assisted cognitive networks

    KAUST Repository

    Tourki, Kamel

    2012-12-01

    Cooperative relay technology was recently introduced into cognitive radio networks in order to enhance network capacity, scalability, and reliability of end-to-end communication. In this paper, we investigate an underlay cognitive network where the quality of service of the secondary link is maintained by triggering an opportunistic regenerative relaying once it falls under an unacceptable level. We first provide the exact cumulative density function (CDF) of received signal-to-noise (SNR) over each hop with co-located relays. Then, the CDFs are used to determine very accurate closed-form expression for the outage probability for a transmission rate R. We validate our analysis by showing that simulation results coincide with our analytical results in Rayleigh fading channels. © 2012 IEEE.

  8. Relay Selection with Partial Information in Wireless Sensor Networks

    CERN Document Server

    Naveen, K P

    2011-01-01

    Our work is motivated by geographical forwarding of sporadic alarm packets to a base station in a wireless sensor network (WSN), where the nodes are sleep-wake cycling periodically and asynchronously. When a node (referred to as the source) gets a packet to forward, either by detecting an event or from an upstream node, it has to wait for its neighbors in a forwarding set (referred to as relays) to wake-up. Each of the relays is associated with a random reward (e.g., the progress made towards the sink) that is iid. To begin with, the source is uncertain about the number of relays, their wake-up times and the reward values, but knows their distributions. At each relay wake-up instant, when a relay reveals its reward value, the source's problem is to forward the packet or to wait for further relays to wake-up. In this setting, we seek to minimize the expected waiting time at the source subject to a lower bound on the average reward. In terms of the operations research literature, our work can be considered as a...

  9. Interference Cancellation in Multi-Access Wireless Relay Networks

    CERN Document Server

    Li, Liangbin; Jafarkhani, Hamid

    2010-01-01

    This paper studies multi-user transmission and detection schemes for multi-access relay networks (MARNs). In a $(J, J_a, R_a, M)$ MARN, $J$ source nodes, each equipped with $J_a$ antennas, send independent messages to one $M$-antenna destination node through one $R_a$-antenna relay node. For complexity considerations, nodes are subject to two linear constraints. The relay generates its output signal by linearly transforming its received signal without decoding. The receiver has linear decoding complexity in the number of users. A new protocol called IC-Relay-TDMA is proposed which takes two steps. In the first step, user symbols are transmitted concurrently to the relay to enhance transmission rates. At the relay, interference cancellation (IC) schemes, previously proposed for systems with direct transmission, are applied to decouple the information of multi-users without decoding. In the second step, symbols of different users are forwarded to the receiver in the time division multi-access (TDMA) fashion. At...

  10. ON THE CAPACITY REGION OF WIRELESS AD HOC RELAY NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Dai Qinyun; Yao Wangsheng; Peng Jianmin; Su Gang

    2006-01-01

    Network capacity is a key characteristic to evaluate the performance of wireless networks. The goal of this paper is to study the capacity of wireless ad hoc relay network. In the model, there is at most ns source nodes transmitting signal simultaneously in the network and the arbitrarily complex network coding is allowed. The upper capacity bound of the network model are derived from the max-flow min-cut theorem and the lower capacity bound are obtained by the rate-distortion function for the Gaussian source. Finally, simulation results show that the upper network capacity will decrease as the number of source nodes is increased.

  11. Efficient Capacity Computation and Power Optimization for Relay Networks

    CERN Document Server

    Parvaresh, Farzad

    2011-01-01

    The capacity or approximations to capacity of various single-source single-destination relay network models has been characterized in terms of the cut-set upper bound. In principle, a direct computation of this bound requires evaluating the cut capacity over exponentially many cuts. We show that the minimum cut capacity of a relay network under some special assumptions can be cast as a minimization of a submodular function, and as a result, can be computed efficiently. We use this result to show that the capacity, or an approximation to the capacity within a constant gap for the Gaussian, wireless erasure, and Avestimehr-Diggavi-Tse deterministic relay network models can be computed in polynomial time. We present some empirical results showing that computing constant-gap approximations to the capacity of Gaussian relay networks with around 300 nodes can be done in order of minutes. For Gaussian networks, cut-set capacities are also functions of the powers assigned to the nodes. We consider a family of power o...

  12. Coded Cooperation for Multiway Relaying in Wireless Sensor Networks

    OpenAIRE

    Zhongwei Si; Junyang Ma; Ragnar Thobaben

    2015-01-01

    Wireless sensor networks have been considered as an enabling technology for constructing smart cities. One important feature of wireless sensor networks is that the sensor nodes collaborate in some manner for communications. In this manuscript, we focus on the model of multiway relaying with full data exchange where each user wants to transmit and receive data to and from all other users in the network. We derive the capacity region for this specific model and propose a coding strategy throug...

  13. 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.

  14. Joint Relay and Jammer Selection for Secure Two-Way Relay Networks

    CERN Document Server

    Chen, Jingchao; Song, Lingyang; Han, Zhu; Jiao, Bingli

    2011-01-01

    In this paper, we investigate joint relay and jammer selection in two-way cooperative networks, consisting of two sources, a number of intermediate nodes, and one eavesdropper, with the constraints of physical layer security. Specifically, the proposed algorithms select two or three intermediate nodes to enhance security against the malicious eavesdropper. The first selected node operates in the conventional relay mode and assists the sources to deliver their data to the corresponding destinations using an amplify-and-forward protocol. The second and third nodes are used in different communication phases as jammers in order to create intentional interference upon the eavesdropper node. Firstly, we find that in a topology where the intermediate nodes are randomly and sparsely distributed, the proposed schemes with cooperative jamming outperform the conventional non-jamming schemes within a certain transmitted power regime. We also find that, in the scenario in which the intermediate nodes gather as a close clu...

  15. Performance of Ad Hoc Networks with Two-Hop Relay Routing and Limited Packet Lifetime

    NARCIS (Netherlands)

    Al Hanbali, Ahmad; Nain, Philippe; Altman, Eitan

    2006-01-01

    Considered is a mobile ad hoc network consisting of three types of nodes (source, destination and relay nodes) and using the two-hop relay routing protocol. Packets at relay nodes are assumed to have a limited lifetime in the network. All nodes are moving inside a bounded region according to some ra

  16. Resource allocation using time division multiple access over wireless relay networks

    Institute of Scientific and Technical Information of China (English)

    DAI Qin-yun; RONG Lu; HU Hong-lin; SU Gang

    2008-01-01

    This article considers a wireless network consisting of multiple sources that communicate with the corresponding destination utilizing a single half-duplex relay, whereas, the sources use the relay opportunistically. By integrating the information theory with the concept of effective capacity, this article proposes a dynamic time allocation strategy over the wireless relay network that aims at maximizing the relay network throughput, subject to a given delay quality of service (QoS) constraint, where time division multiple access (TDMA) is applied in the relay network. The simulation results show that the proposed allocation strategy can significantly improve the effective capacity as compared to the traditional equal time allocation strategy.

  17. Joint Source-Channel Cooperative Transmission over Relay-Broadcast Networks

    OpenAIRE

    Gunduz, Deniz; Erkip, Elza; Goldsmith, Andrea; Poor, H. Vincent

    2012-01-01

    Reliable transmission of a discrete memoryless source over a multiple-relay relay-broadcast network is considered. Motivated by sensor network applications, it is assumed that the relays and the destinations all have access to side information correlated with the underlying source signal. Joint source-channel cooperative transmission is studied in which the relays help the transmission of the source signal to the destinations by using both their overheard signals, as in the classical channel ...

  18. 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.

  19. Wireless MIMO Switching with Zero-forcing Relaying and Network-coded Relaying

    CERN Document Server

    Wang, Fanggang; Guo, Dongning

    2011-01-01

    A wireless relay with multiple antennas is called a multiple-input-multiple-output (MIMO) switch if it forms a one-to-one mapping from the inputs (uplinks) to the outputs (downlinks). This paper studies the case with $N$ stations and the MIMO switch controls which stations are connected to which other stations. The switching is achieved by "precode-and-forward". In particular, the relay precodes the received vector signal by either a zero-forcing matrix or a network-coded matrix. With the zero-forcing precoder, each destination station receives only its desired signal with enhanced noise but no interference. With the network-coded precoder, on the other hand, each station receives not only its desired signal with noise but also self-interference, which can be perfectly canceled. Assuming full channel state information is available at the switch, the design of both precoders for maximizing the minimum received signal-to-noise ratio is investigated. The problem with two stations is solved in closed form in cert...

  20. Capacity of a Class of Multi-source Relay Networks

    CERN Document Server

    Jeon, Sang-Woon

    2009-01-01

    Characterizing the capacity region of multi-source wireless relay networks is one of the fundamental issues in network information theory. The problem is, however, quite challenging because the transmission of other sessions acts as inter-user interference when there exist multiple source-destination (S-D) pairs in the network. By focusing on a special class of networks, we show that the capacity can be found. Namely, we study a linear finite-field network with time-varying channels, which exhibits broadcast, interference, and fading natures of wireless communication. We observe that fading can play an important role in mitigating inter-user interference effectively for both single-hop and multi-hop networks. We propose new block Markov encoding and relaying schemes with randomized channel pairing, which exploit such channel variations, and derive their achievable rates. By comparing them with the general cut-set upper bound, the capacity region of single-hop networks and the sum-capacity of multi-hop network...

  1. Degrees of Freedom of Asymmetrical Multi-Way Relay Networks

    DEFF Research Database (Denmark)

    Sun, Fan; De Carvalho, Elisabeth

    2011-01-01

    In this paper, we introduce an asymmetrical multi-way relay channel where a base station conveys independent symbols to K different users while receiving independent symbols from the users. In this network, user i Shas Mi antennas (i ∈ [1, ..., K]), the base station has Σi=1K Mi antennas and the ...... with a proposed joint multiple access and broadcast precoding design using the signal space alignment concept....

  2. Relay Subset Selection in Wireless Networks Using Partial Decode-and-Forward Transmission

    CERN Document Server

    Lo, Caleb K; Heath, Robert W

    2007-01-01

    This paper considers the problem of selecting a subset of nodes in a two-hop wireless network to act as relays in aiding the communication between the source-destination pair. Optimal relay subset selection with the objective of maximizing the overall throughput is a difficult problem that depends on multiple factors including node locations, queue lengths and power consumption. A partial decode-and-forward strategy is applied in this paper to improve the tractability of the relay selection problem and performance of the overall network. Note that the number of relays selected ultimately determines the performance of the network. This paper benchmarks this performance by determining the net diversity achieved using the relays selected and the partial decode-and-forward strategy. This framework is subsequently used to further transform relay selection into a simpler relay placement problem, and two proximity-based approximation algorithms are developed to determine the appropriate set of relays to be selected ...

  3. Outage analysis for underlay cognitive networks using incremental regenerative relaying

    KAUST Repository

    Tourki, Kamel

    2013-02-01

    Cooperative relay technology has recently been introduced into cognitive radio (CR) networks to enhance the network capacity, scalability, and reliability of end-to-end communication. In this paper, we investigate an underlay cognitive network where the quality of service (QoS) of the secondary link is maintained by triggering an opportunistic regenerative relaying once it falls under an unacceptable level. Analysis is conducted for two schemes, referred to as the channel-state information (CSI)-based and fault-tolerant schemes, respectively, where different amounts of CSI were considered. We first provide the exact cumulative distribution function (cdf) of the received signal-to-noise ratio (SNR) over each hop with colocated relays. Then, the cdf\\'s are used to determine a very accurate closed-form expression for the outage probability for a transmission rate $R$. In a high-SNR region, a floor of the secondary outage probability occurs, and we derive its corresponding expression. We validate our analysis by showing that the simulation results coincide with our analytical results in Rayleigh fading channels. © 1967-2012 IEEE.

  4. Systematic Network Coding with the Aid of a Full-Duplex Relay

    DEFF Research Database (Denmark)

    Giacaglia, Giuliano; Shi, Xiaomeng; Kim, MinJi;

    2013-01-01

    A characterization of systematic network coding over multi-hop wireless networks is key towards understanding the trade-off between complexity and delay performance of networks that preserve the systematic structure. This paper studies the case of a relay channel, where the source's objective...... is to deliver a given number of data packets to a receiver with the aid of a relay. The source broadcasts to both the receiver and the relay using one frequency, while the relay uses another frequency for transmissions to the receiver, allowing for a full-duplex operation of the relay. We analyze the decoding...

  5. Alternate MIMO AF relaying networks with interference alignment: Spectral efficient protocol and linear filter design

    KAUST Repository

    Park, Kihong

    2013-02-01

    In this paper, we study a two-hop relaying network consisting of one source, one destination, and three amplify-and-forward (AF) relays with multiple antennas. To compensate for the capacity prelog factor loss of 1/2$ due to the half-duplex relaying, alternate transmission is performed among three relays, and the inter-relay interference due to the alternate relaying is aligned to make additional degrees of freedom. In addition, suboptimal linear filter designs at the nodes are proposed to maximize the achievable sum rate for different fading scenarios when the destination utilizes a minimum mean-square error filter. © 1967-2012 IEEE.

  6. Physical Network Coding in Two-Way Wireless Relay Channels

    CERN Document Server

    Popovski, Petar

    2007-01-01

    It has recently been recognized that the wireless networks represent a fertile ground for devising communication modes based on network coding. A particularly suitable application of the network coding arises for the two--way relay channels, where two nodes communicate with each other assisted by using a third, relay node. Such a scenario enables application of \\emph{physical network coding}, where the network coding is either done (a) jointly with the channel coding or (b) through physical combining of the communication flows over the multiple access channel. In this paper we first group the existing schemes for physical network coding into two generic schemes, termed 3--step and 2--step scheme, respectively. We investigate the conditions for maximization of the two--way rate for each individual scheme: (1) the Decode--and--Forward (DF) 3--step schemes (2) three different schemes with two steps: Amplify--and--Forward (AF), JDF and Denoise--and--Forward (DNF). While the DNF scheme has a potential to offer the...

  7. Secure relay selection based on learning with negative externality in wireless networks

    Science.gov (United States)

    Zhao, Caidan; Xiao, Liang; Kang, Shan; Chen, Guiquan; Li, Yunzhou; Huang, Lianfen

    2013-12-01

    In this paper, we formulate relay selection into a Chinese restaurant game. A secure relay selection strategy is proposed for a wireless network, where multiple source nodes send messages to their destination nodes via several relay nodes, which have different processing and transmission capabilities as well as security properties. The relay selection utilizes a learning-based algorithm for the source nodes to reach their best responses in the Chinese restaurant game. In particular, the relay selection takes into account the negative externality of relay sharing among the source nodes, which learn the capabilities and security properties of relay nodes according to the current signals and the signal history. Simulation results show that this strategy improves the user utility and the overall security performance in wireless networks. In addition, the relay strategy is robust against the signal errors and deviations of some user from the desired actions.

  8. Slepian-Wolf Coding Over Cooperative Relay Networks

    CERN Document Server

    Yassaee, Mohammad Hossein

    2009-01-01

    This paper deals with the problem of multicasting a set of discrete memoryless correlated sources (DMCS) over a cooperative relay network. Necessary conditions with cut-set interpretation are presented. A \\emph{Joint source-Wyner-Ziv encoding/sliding window decoding} scheme is proposed, in which decoding at each receiver is done with respect to an ordered partition of other nodes. For each ordered partition a set of feasibility constraints are derived. Then, utilizing sub-modular property of entropy function and a novel geometrical approach, the results of different ordered partitions are consolidated, which lead sufficient conditions for our problem. The proposed scheme achieves operational separation between source coding and channel coding. It is shown that sufficient conditions are indeed necessary conditions in two special cooperative networks, namely, Aref network and finite-field deterministic network. Also, in Gaussian cooperative networks, it is shown that reliable transmission of all DMCS whose Slep...

  9. Power Allocation and Pricing in Multi-User Relay Networks Using Stackelberg and Bargaining Games

    CERN Document Server

    Cao, Qian; Jing, Yindi

    2012-01-01

    This paper considers a multi-user single-relay wireless network, where the relay gets paid for helping the users forward signals, and the users pay to receive the relay service. We study the relay power allocation and pricing problems, and model the interaction between the users and the relay as a two-level Stackelberg game. In this game, the relay, modeled as the service provider and the leader of the game, sets the relay price to maximize its revenue; while the users are modeled as customers and the followers who buy power from the relay for higher transmission rates. We use a bargaining game to model the negotiation among users to achieve a fair allocation of the relay power. Based on the proposed fair relay power allocation rule, the optimal relay power price that maximizes the relay revenue is derived analytically. Simulation shows that the proposed power allocation scheme achieves higher network sum-rate and relay revenue than the even power allocation. Furthermore, compared with the sum-rate-optimal so...

  10. Distributed Relay Selection for MIMO-SDM Cooperative Networks

    Science.gov (United States)

    Tran, Xuan Nam; Nguyen, Vinh Hanh; Bui, Thanh Tam; Dinh, The Cuong; Karasawa, Yoshio

    In this paper, we consider an amplify-and-forward cooperative wireless network in which network nodes use multiple input multiple output (MIMO) spatial division multiplexing (SDM) to communicate with one another. We examine the problem of distributed cooperative relay selection and signal combining at the destination. First, we propose three distributed relay selection algorithms based on the maximum channel gains, the maximum harmonic mean of the channel gains, and the minimum mean squared error (MSE) of the signal estimation. Second, we propose a minimum mean square error (MMSE) signal combining scheme which jointly serves as the optimal signal combiner and interference canceler. It is shown that the MSE selection together with the MMSE combining achieves the maximal diversity gain. We also show that in MIMO-SDM cooperative networks increasing the number of candidate nodes does not help to improve the BER performance as opposed to the cooperative networks where each node is equipped with only single antenna. A practical approach to implementation of the combiner based on the current wireless access network protocols will also be presented.

  11. Joint Next-Hop/Relay Selection for Distributive Multihop Cooperative Networks

    Directory of Open Access Journals (Sweden)

    Ahmed Alkhayyat

    2015-01-01

    Full Text Available Cooperative networks that use adjacent nodes to relay hearing data are employed as an effective technique to deal with channel fading, thereby enhancing the network performances. Next-hop and relay nodes selection schemes determine the optimal next-hop node toward the destination and relay node between the source and the optimal next-hop and/or destination. Offering joint next-hop and relay node selection in distributive multihop cooperative networks will enable the source to select the optimal next-hop node and relay node that can improve the system performance. In this paper, we propose a joint next-hop node and relay node selection (JNRS protocol for wireless distributive multihop cooperative networks. The goal of JNRS is to reduce the spectral efficiency loss and outage probability. Analysis results show that JNRS can enhance the cooperative networks performance under general conditions compared to cooperative networks without the JNRS protocol.

  12. A SDP based design of relay precoding for the power minimization of MIMO AF-relay networks

    KAUST Repository

    Rao, Anlei

    2015-09-11

    Relay precoding for multiple-input and multiple-output (MIMO) relay networks has been approached by either optimizing the efficiency performance with given power consumption constraints or minimizing the power consumption with quality-of-service (QoS) requirements. For the later type design, previous works has worked on minimizing the approximated power consumption. In this paper, exact power consumption for all relays is derived into a quadratic form by diagonalizing the minimum-square error (MSE) matrix, and the relay precoding matrix is designed by optimizing this quadratic form with the help of semidefinite programming (SDP) relaxation. Our simulation results show that such a design can achieve a gain of around 3 dB against the previous design, which optimized the approximated power consumption. © 2015 IEEE.

  13. 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)

  14. Energy efficient networking via dynamic relay node selection in wireless networks

    NARCIS (Netherlands)

    Graaf, de Maurits

    2013-01-01

    Mobile wireless ad-hoc networks need to maximize their network lifetime (defined as the time until the first node runs out of energy). In the broadcast network lifetime problem, all nodes are sending broadcast traffic, and one asks for an assignment of transmit powers to nodes, and for sets of relay

  15. Coded Cooperation for Multiway Relaying in Wireless Sensor Networks

    Science.gov (United States)

    Si, Zhongwei; Ma, Junyang; Thobaben, Ragnar

    2015-01-01

    Wireless sensor networks have been considered as an enabling technology for constructing smart cities. One important feature of wireless sensor networks is that the sensor nodes collaborate in some manner for communications. In this manuscript, we focus on the model of multiway relaying with full data exchange where each user wants to transmit and receive data to and from all other users in the network. We derive the capacity region for this specific model and propose a coding strategy through coset encoding. To obtain good performance with practical codes, we choose spatially-coupled LDPC (SC-LDPC) codes for the coded cooperation. In particular, for the message broadcasting from the relay, we construct multi-edge-type (MET) SC-LDPC codes by repeatedly applying coset encoding. Due to the capacity-achieving property of the SC-LDPC codes, we prove that the capacity region can theoretically be achieved by the proposed MET SC-LDPC codes. Numerical results with finite node degrees are provided, which show that the achievable rates approach the boundary of the capacity region in both binary erasure channels and additive white Gaussian channels. PMID:26131675

  16. Coded Cooperation for Multiway Relaying in Wireless Sensor Networks.

    Science.gov (United States)

    Si, Zhongwei; Ma, Junyang; Thobaben, Ragnar

    2015-01-01

    Wireless sensor networks have been considered as an enabling technology for constructing smart cities. One important feature of wireless sensor networks is that the sensor nodes collaborate in some manner for communications. In this manuscript, we focus on the model of multiway relaying with full data exchange where each user wants to transmit and receive data to and from all other users in the network. We derive the capacity region for this specific model and propose a coding strategy through coset encoding. To obtain good performance with practical codes, we choose spatially-coupled LDPC (SC-LDPC) codes for the coded cooperation. In particular, for the message broadcasting from the relay, we construct multi-edge-type (MET) SC-LDPC codes by repeatedly applying coset encoding. Due to the capacity-achieving property of the SC-LDPC codes, we prove that the capacity region can theoretically be achieved by the proposed MET SC-LDPC codes. Numerical results with finite node degrees are provided, which show that the achievable rates approach the boundary of the capacity region in both binary erasure channels and additive white Gaussian channels. PMID:26131675

  17. Coded Cooperation for Multiway Relaying in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Zhongwei Si

    2015-06-01

    Full Text Available Wireless sensor networks have been considered as an enabling technology for constructing smart cities. One important feature of wireless sensor networks is that the sensor nodes collaborate in some manner for communications. In this manuscript, we focus on the model of multiway relaying with full data exchange where each user wants to transmit and receive data to and from all other users in the network. We derive the capacity region for this specific model and propose a coding strategy through coset encoding. To obtain good performance with practical codes, we choose spatially-coupled LDPC (SC-LDPC codes for the coded cooperation. In particular, for the message broadcasting from the relay, we construct multi-edge-type (MET SC-LDPC codes by repeatedly applying coset encoding. Due to the capacity-achieving property of the SC-LDPC codes, we prove that the capacity region can theoretically be achieved by the proposed MET SC-LDPC codes. Numerical results with finite node degrees are provided, which show that the achievable rates approach the boundary of the capacity region in both binary erasure channels and additive white Gaussian channels.

  18. Improved Relay Node Placement Algorithm for Wireless Sensor Networks Application in Wind Farm

    DEFF Research Database (Denmark)

    Chen, Qinyin; Hu, Y.; Chen, Zhe;

    2013-01-01

    An emergent application of Wireless Sensor Network (WSN) technology is in the area of Wind Farm Monitoring (WFM), in which relays are used to connect sensors. Key problems to solve in WFM include how to balance loads across relay nodes and how to place relay nodes for redundancy and fault...... node placement problem. A heuristic algorithm is proposed for candidate relay nodes selection and its feasibility considered and verified. Based on the results obtained, an improved algorithm is proposed. Linearization of the algorithm’s complexity is then considered to achieve network load balancing...... node placement algorithm is proposed in this paper to approximate the optimal position for relays connecting each turbine. However, constraints are then required to prevent relay nodes being overloaded in 3-dimensions. The algorithm is extended to 3-dimensional Euclidean space for this optimal relay...

  19. Resource Partitioning and Routing Optimization in Relay Enhanced Cellular Network

    Institute of Scientific and Technical Information of China (English)

    LIU Tao; RONG Meng-tian; SHI Hong-kui; XUE Yi-sheng

    2007-01-01

    A joint routing and resource partitioning scheme were proposed to improve cell capacity and user throughput of cellular network enhanced with two-hop fixed relay nodes (FRNs).Radio resources are partitioned under a reuse partitioning based framework, which guarantees effective and efficient inter-cell interference management.At the same time, each mobile terminal was assigned a channel-dependent route by the routing controller,which tries to maximize the cell capacity under the constraint imposed by reuse partitioning.Intensive computer simulations demonstrate the performance superiority of the FRN enhanced cellular network employing this scheme in comparison with conventional network, as well as the validity of the channel-dependent routing mechanism.

  20. New resource allocation scheme for cognitive relay networks with opportunistic access

    KAUST Repository

    Zafar, Ammar

    2012-06-01

    In this paper, a new resource allocation scheme to minimize Symbol Error rate (SER) for relay assisted cognitive radio networks is studied. A cognitive relay network with amplify-and-forward (AF) fixed gain relays and opportunistic access to the licensed spectrum is considered. The SER objective function and the optimization constraints are derived first. The resource allocation algorithm is then derived using the Langrangian multiplier method. Closed form expressions are derived for the source and relay powers and, symbol time. Analytical results show that the optimal power allocation follows an extended water-filling solution. © 2012 IEEE.

  1. Energy-efficient Power Allocation Strategy in Cognitive Relay Networks

    Directory of Open Access Journals (Sweden)

    Z. Zhang

    2012-09-01

    Full Text Available Cognitive radio and cooperative technique are two essential techniques for the future generation green communication paradigm owing to its inherent advantages of adaptability and cognition. Typically, previous studies on power allocation in the cognitive relay networks often concentrate on two goals independently: the first goal is to minimize the transmit power to reduce energy consumption, as depicted in strategy 1; the second goal is to maximize the transmit rate, as depicted in strategy 2. In this paper, we shift our focus to energy-efficient-oriented design, that is, green power allocation between source and relay. Therefore, we present a novel power allocation strategy considering the two goals jointly, as depicted in strategy 3, and compare the proposed strategy with two previous strategies. Specifically, because the strategy 3 is nonlinear, we use the Lagrange dual method to solve it effectively. Finally, the numerical results are presented to validate our theoretical results through theory simulation and Monte Carlo simulation. Numerical performance results show that the proposed strategy works better than that of the two previous strategies from the viewpoints of energy-efficient.

  2. Exact Outage Performance Analysis of Multiuser Multi-relay Spectrum Sharing Cognitive Networks

    Directory of Open Access Journals (Sweden)

    T. Zhang

    2015-04-01

    Full Text Available In this paper, we investigate the outage performance of dual-hop multiuser multi-relay cognitive radio networks under spectrum sharing constraints. Using an efficient relay-destination selection scheme, the exact and asymptotic closed-form expressions for the outage probability are derived. From these expressions it is indicated that the achieved diversity order is only determined by the number of secondary user (SU relays and destinations, and equals to M+N (where M and N are the number of destination nodes and relay nodes, respectively. Further, we find that the coding gain of the SU network will be affected by the interference threshold $bar I$ at the primary user (PU receiver. Specifically, as the increases of the interference threshold, the coding gain of the considered network approaches to that of the multiuser multi-relay system in the non-cognitive network. Finally, our study is corroborated by representative numerical examples.

  3. Relay selection in underlay cognitive networks with fixed transmission power nodes

    KAUST Repository

    Hussain, Syed Imtiaz

    2013-07-31

    Underlay cognitive networks operate simultaneously with primary networks satisfying stringent interference constraints, which reduces their transmission power and coverage area. To reach remote destinations, secondary sources use relaying techniques. Selecting the best relay among the available ones is a well known technique. Recently, selective cooperation is investigated in cognitive networks where the secondary nodes can adapt their transmission power to always satisfy the interference threshold. In this paper, we investigate a situation where the secondary nodes have a fixed transmission power and may violate the interference threshold. We present two relay selection schemes; the first one excludes the relays not satisfying the interference constraint and then picks up a relay from the remaining ones that can provide the maximum signal-to-noise ratio (SNR). The other scheme uses a quotient of the relay link SNR and the interference from the relay to the primary user and optimizes it to maximise the relay link SNR. We derive closed form expressions for outage probability, bit error rate, channel capacity and diversity of the system for both schemes by using tight approximations. We also study mutual effects of interference. Simulation results confirm the analytical results and reveal that the relay selection is feasible at low SNRs. Copyright © 2013 John Wiley & Sons, Ltd.

  4. Joint Source-Channel Cooperative Transmission over Relay-Broadcast Networks

    CERN Document Server

    Gunduz, Deniz; Goldsmith, Andrea; Poor, H Vincent

    2012-01-01

    Reliable transmission of a discrete memoryless source over a multiple-relay relay-broadcast network is considered. Motivated by sensor network applications, it is assumed that the relays and the destinations all have access to side information correlated with the underlying source signal. Joint source-channel cooperative transmission is studied in which the relays help the transmission of the source signal to the destinations by using both their overheard signals, as in the classical channel cooperation scenario, as well as the available correlated side information. Decode-and-forward (DF) based cooperative transmission is considered in a network of multiple relay terminals and two different achievability schemes are proposed: i) a regular encoding and sliding-window decoding scheme without explicit source binning at the encoder, and ii) a semi-regular encoding and backward decoding scheme with binning based on the side information statistics. It is shown that both of these schemes lead to the same source-cha...

  5. Semi-Distributed Relay Selection Algorithm for Multi-User Cooperative Wireless Networks

    Directory of Open Access Journals (Sweden)

    Yafeng Wang

    2011-06-01

    Full Text Available In this paper, we propose a novel semi-distributed algorithm with low overhead and complexity for multi-user cooperative wireless networks with opportunistic relaying. The source is required to satisfy its minimum rate requirement with a feasible relay and help another source as a relay. The optimal solution can be obtained by exhaustive search with intractable computational complexity. Simulation results suggest that the proposed relay selection algorithm has the similar outage probability as the exhaustive search approach but with much less computational burden.

  6. Relay-aided multi-cell broadcasting with random network coding

    DEFF Research Database (Denmark)

    Lu, Lu; Sun, Fan; Xiao, Ming;

    2010-01-01

    We investigate a relay-aided multi-cell broadcasting system using random network codes, where the focus is on devising efficient scheduling algorithms between relay and base stations. Two scheduling algorithms are proposed based on different feedback strategies; namely, a one-step scheduling...

  7. Full-Duplex opportunistic relay selection in future spectrum-sharing networks

    KAUST Repository

    Khafagy, Mohammad Galal

    2015-06-01

    We propose and analyze the performance of full-duplex relay selection in primary/secondary spectrum-sharing networks. Contrary to half-duplex relaying, full-duplex relaying (FDR) enables simultaneous listening/forwarding at the secondary relay, thereby allowing for a higher spectral efficiency. However, since the source and relay simultaneously transmit in FDR, their superimposed signal at the primary receiver should now satisfy the existing interference constraint which can considerably limit the secondary network throughput. In this regard, relay selection can offer an adequate solution to boost the secondary throughput while satisfying the imposed interference limit. We first analyze the performance of opportunistic relay selection among a cluster of full-duplex decode-and-forward relays with self-interference by deriving the exact cumulative distribution function of its end-to-end signal-to-noise ratio. Second, we evaluate the end-to-end performance of relay selection with interference constraints due to the presence of a primary receiver. Finally, the presented exact theoretical findings are verified by numerical simulations.

  8. Best relay selection using SNR and interference quotient for underlay cognitive networks

    KAUST Repository

    Hussain, Syed Imtiaz

    2012-06-01

    Cognitive networks in underlay settings operate simultaneously with the primary networks satisfying stringent interference limits. This condition forces them to operate with low transmission powers and confines their area of coverage. In an effort to reach remote destinations, underlay cognitive sources make use of relaying techniques. Selecting the best relay among those who are ready to cooperate is different in underlay settings than traditional non-cognitive networks. In this paper, we present a relay selection scheme which uses the quotient of the relay link signal to noise ratio (SNR) and the interference generated from the relay to the primary user to choose the best relay. The proposed scheme optimizes this quotient in a way to maximize the relay link SNR above a certain value whereas the interference is kept below a defined threshold. We derive closed expressions for the outage probability and bit error probability of the system incorporating this scheme. Simulation results confirm the validity of the analytical results and reveal that the relay selection in cognitive environment is feasible in low SNR regions. © 2012 IEEE.

  9. Optimization of beamforming and path planning for UAV-assisted wireless relay networks

    Directory of Open Access Journals (Sweden)

    Ouyang Jian

    2014-04-01

    Full Text Available Recently, unmanned aerial vehicles (UAVs acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifically, in the scenario where the access point (AP is mobile, a UAV needs to find an efficient path to guarantee the connectivity of the relay link. Motivated by this fact, this paper proposes an optimal design for beamforming (BF and UAV path planning. First of all, we study a dual-hop amplify-and-forward (AF wireless relay network, in which a UAV is used as relay between a mobile AP and a fixed base station (BS. In the network, both of the AP and the BS are equipped with multiple antennas, whereas the UAV has a single antenna. Then, we obtain the output signal-to-noise ratio (SNR of the dual-hop relay network. Based on the criterion of maximizing the output SNR, we develop an optimal design to obtain the solution of the optimal BF weight vector and the UAV heading angle. Next, we derive the closed-form outage probability (OP expression to investigate the performance of the dual-hop relay network conveniently. Finally, computer simulations show that the proposed approach can obtain nearly optimal flying path and OP performance, indicating the effectiveness of the proposed algorithm. Furthermore, we find that increasing the antenna number at the BS or the maximal heading angle can significantly improve the performance of the considered relay network.

  10. 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.

  11. 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.

  12. Near-optimal quantization and linear network coding for relay networks

    CERN Document Server

    Muralidhar, Anand

    2012-01-01

    We introduce a discrete network corresponding to any Gaussian wireless network that is obtained by simply quantizing the received signals and restricting the transmitted signals to a finite precision. Since signals in the discrete network are obtained from those of a Gaussian network, the Gaussian network can be operated on the quantization-based digital interface defined by the discrete network. We prove that this digital interface is near-optimal for Gaussian relay networks and the capacities of the Gaussian and the discrete networks are within a bounded gap of O(M^2) bits, where M is the number of nodes. We prove that any near-optimal coding strategy for the discrete network can be naturally transformed into a near-optimal coding strategy for the Gaussian network merely by quantization. We exploit this by designing a linear coding strategy for the case of layered discrete relay networks. The linear coding strategy is near-optimal for Gaussian and discrete networks and achieves rates within O(M^2) bits of t...

  13. Outage Analysis of PLNC Based Bidirectional Relay Network in the presence of I/Q Imbalance

    Directory of Open Access Journals (Sweden)

    V.N.Senthil Kumaran

    2014-08-01

    Full Text Available Bidirectional relay network consists of two sources and a relay, where each node has a single antenna and operates in half duplex mode. The PLNC based OFDM system transmits numerous high data streams through narrow band flat fading subchannels to achieve high spectral efficiency over wide band channels. However in practice, I/Q imbalance is introduced at the radio frequency sections of the nodes affects the orthogonality among the subcarriers. In this paper, the bidirectional relay network is modelled with I/Q imbalance and the outage performance of Orthogonal Frequency Division Multiplexing (OFDM based bidirectional relay network which employs physical layer network coding (PLNC is analyzed in the presence of In-phase and Quadrature (I/Q imbalance at both the time slots.

  14. Network Planning and Optimization for Multi-Hop Relay Placement in WiMAX Networks

    Directory of Open Access Journals (Sweden)

    Chitapong Wechtaison

    2012-01-01

    Full Text Available Problem statement: Wireless access networks can provide high level of quality of services at low network installation budget if the networks are planned by using proper methods. In this research, we developed efficient network planning methods for Wireless Interoperability for Microwave Access (WiMAX networks in which the multiple hops of relay stations are deployed. Approach: An integer linear programming model was applied to the proposed problems for WiMAX networks. Our key contribution of the proposed model is two-fold. First, it aims at maximizing the quality of services of the networks, including the physical data rate and the received signal strength. Second, it aims at minimizing the cost to install the networks. The output from the proposed model is the optimal locations for the installation of the WiMAX base stations and the relay stations so that the network can accommodate user traffic demand over the target service area. Results: To evaluate the effectiveness of the proposed model, we conducted numerical experiments in the real network service environments. Conclusion: Applying our proposed model, performances of WiMAX networks can be improved in both the physical data rate and the service coverage area.

  15. On the benefits of location-based relay selection in mobile wireless networks

    DEFF Research Database (Denmark)

    Nielsen, Jimmy Jessen; Madsen, Tatiana Kozlova; Schwefel, Hans-Peter

    2016-01-01

    We consider infrastructure-based mobile networks that are assisted by a single relay transmission where both the downstream destination and relay nodes are mobile. Selecting the optimal transmission path for a destination node requires up-to-date link quality estimates of all relevant links....... If the relay selection is based on link quality measurements, the number of links to update grows quadratically with the number of nodes, and measurements need to be updated frequently when nodes are mobile. In this paper, we consider a location-based relay selection scheme where link qualities are estimated...... from node positions; in the scenario of a node-based location system such as GPS, the location-based approach reduces signaling overhead, which in this case only grows linearly with the number of nodes. This paper studies these two relay selection approaches and investigates how they are affected...

  16. Secure amplify-and-forward untrusted relaying networks using cooperative jamming and zero-forcing cancelation

    KAUST Repository

    Park, Kihong

    2015-12-03

    In this paper, we investigate secure transmission in untrusted amplify-and-forward half-duplex relaying networks with the help of cooperative jamming at the destination (CJD). Under the assumption of full channel state information (CSI), conventional CJD using self-interference cancelation at the destination is efficient when the untrusted relay has no capability to suppress the jamming signal. However, if the source and destination are equipped with a single antenna and the only untrusted relay is equipped with N multiple antennas, it can remove the jamming signal from the received signal by linear filters and the full multiplexing gain of relaying cannot be achievable with the conventional CJD due to the saturation of the secrecy rate at the high transmit power regime. We propose in this paper new CJD scheme where neither destination nor relay can acquire CSI of relay-destination link. Our proposed scheme utilizes zero-forcing cancelation based on known jamming signals instead of self-interference subtraction, while the untrusted relay cannot suppress the jamming signals due to the lack of CSI. We show that the secrecy rate of the proposed scheme can enjoy a half of multiplexing gain in half-duplex relaying while that of conventional CJD is saturated at high transmit power for N ???2. The impact of channel estimation error at the destination is also investigated to show the robustness of the proposed scheme against strong estimation errors.

  17. Wireless Relay Selection in Pocket Switched Networks Based on Spatial Regularity of Human Mobility

    Directory of Open Access Journals (Sweden)

    Jianhui Huang

    2016-01-01

    Full Text Available Pocket switched networks (PSNs take advantage of human mobility to deliver data. Investigations on real-world trace data indicate that human mobility shows an obvious spatial regularity: a human being usually visits a few places at high frequencies. These most frequently visited places form the home of a node, which is exploited in this paper to design two HomE based Relay selectiOn (HERO algorithms. Both algorithms input single data copy into the network at any time. In the basic HERO, only the first node encountered by the source and whose home overlaps a destination’s home is selected as a relay while the enhanced HERO keeps finding more optimal relay that visits the destination’s home with higher probability. The two proposed algorithms only require the relays to exchange the information of their home and/or the visiting frequencies to their home when two nodes meet. As a result, the information update is reduced and there is no global status information that needs to be maintained. This causes light loads on relays because of the low communication cost and storage requirements. Additionally, only simple operations are needed in the two proposed algorithms, resulting in little computation overhead at relays. At last, a theoretical analysis is performed on some key metrics and then the real-world based simulations indicate that the two HERO algorithms are efficient and effective through employing only one or a few relays.

  18. Approximate Capacity of a Class of Multi-source Gaussian Relay Networks

    CERN Document Server

    Jeon, Sang-Woon; Jafar, Syed A

    2010-01-01

    We study a Gaussian relay network in which multiple source--destination (S--D) pairs communicate through relays without direct links between the sources and the destinations. We observe that the time-varying nature of wireless channels or fading can be used to mitigate the interference. The proposed block Markov amplify-and-forward relaying scheme exploits such channel variations and works for a wide class of channel distributions including Rayleigh fading. We completely characterize the degrees of freedom (DoF) region of the Gaussian relay network. Specifically, the DoF region of the $K$-user $M$-hop Gaussian relay network with $K_m$ nodes in the $m^{\\mbox{th}}$ layer is the set of all $(d_1,\\cdots,d_K)$ such that $d_i\\leq 1$ for all $i$ and $\\sum_{i=1}^K d_i\\leq \\min\\{K_1,\\cdots,K_{M+1}\\}$, where $d_i$ is the DoF of the $i^{\\mbox{th}}$ S--D pair and $K=K_1=K_{M+1}$ is the number of S--D pairs. We further characterize the DoF region of the Gaussian relay network with multi-antenna nodes and general message s...

  19. Resource allocation for relay assisted cognitive radio networks

    KAUST Repository

    Zafar, Ammar

    2012-09-16

    In this paper, we present two optimal resource allocation schemes that maximize throughput and symbol correct rate (SCR). The throughput and SCR are derived. The derived throughput and SCR are optimized with respect to the sensing time, the source transmission power and the relay transmission power. Numerical results show that the optimal sensing time is dependent on the primary user\\'s signal-to-noise-ratio (SNR). They also show that SCR increases with increase in the number of relays. © 2012 IEEE.

  20. IEEE 802.16J-Relay Fortified Aeromacs Networks; Benefits and Challenges

    Science.gov (United States)

    Kamali, Behnam; Apaza, Rafael D.

    2014-01-01

    Aeronautical Mobile Airport Communications System (AeroMACS) is an IEEE 802.16 standard-based (WiMAX) broadband aviation transmission technology, developed to provide safety critical communications coverage for airport surface in support of fixed and mobile ground to ground applications and services. We have previously demonstrated that IEEE 802.16j-amendment-based WiMAX is most feasible for AeroMACS applications. The principal argument in favor of application of IEEE 802.16j technology is the flexible and cost effective extension of radio coverage that is afforded by relay fortified WiMAX networks, with virtually no increase in the power requirements. In this article, following introductory remarks on airport surface communications, WiMAX and AeroMACS; the IEEE 802.16j-based WiMAX technology and multihop relay systems are briefly described. The two modes of relay operation supported by IEEE 802.16j amendment; i.e., transparent (TRS) and non-transparent (NTRS) modes, are discussed in some detail. Advantages and disadvantages of using TRS and NTRS in AeroMACS networks are summarized in a table. Practical issues vis--vis the inclusion of relays in AeroMACS networks are addressed. It is argued that the selection of relay type may affect a number of network parameters. A discussion on specific benefits and challenges of inclusion of relays in AeroMACS networks is provided. The article concludes that in case it is desired or necessary to exclusively employ one type of relay mode for all applications throughout an AeroMACS network, the proper selection would be the non-transparent mode.

  1. Cooperative Communication Protocol based on Relay Node Grouping in Wireless Networks

    Directory of Open Access Journals (Sweden)

    Sunmyeng Kim

    2015-10-01

    Full Text Available IEEE 802.11a/b/g standards support multiple data rates. Although the use of multiple data rates increases the capacity of wireless networks, it can lead to a performance anomaly problem. Cooperative communication for wireless networks has attracted considerable interest owing to its ability to mitigate this performance anomaly problem. In cooperative communication, a number of relay nodes support a source node in the forwarding of data packets to a destination node. If the direct transmission of a data packet between a source node and a destination node is not successful, the overheard data packet from the source node is forwarded by relay nodes to the destination node. Several MAC (Medium Access Control protocols have been proposed for cooperative communication in wireless networks. A number of these can result in collisions among the relay nodes in a dense network. Further, cooperative communication can be interrupted by other nodes. To resolve these problems, we propose a new cooperative protocol. In the proposed protocol, relay nodes are divided into several groups based on their data rates. Then, to limit the number of contending relay nodes, only the relay nodes in the highest group are selected. Collisions among the selected relay nodes are resolved based on a backoff mechanism. The proposed protocol ensures that cooperative communication is not interrupted by other nodes by implementing a busy signal and NAV (Network Allocation Vector. The proposed protocol can reduce the collision probability and increase the network performance. Performance evaluation is conducted using simulation, and confirms that the proposed protocol significantly outperforms the previous protocol in terms of throughput, collision probability, and delay.

  2. Performance analysis for a two-way relaying power line network with analog network coding

    Institute of Scientific and Technical Information of China (English)

    Yu-wen QIAN; Meng TIAN; Xue JIANG; Hua-ju SONG; Feng SHU; Jun LI

    2015-01-01

    In this paper, we investigate a two-way relaying power line communication (PLC) network with analog network coding. We focus on the analysis of the system outage probability, symbol error rate, and average capacity. Specifically, we first derive the probability density function (PDF) of the received signal-to-noise ratio (SNR) with a closed form, by exploiting the statistical properties of the PLC channel. Then with the help of this PDF, we develop the outage probability, symbol error rate, and average capacity with closed forms, based on the Hermite polynomial. Simulations show that the derived analytical results are consistent with those by Monte Carlo simulation.

  3. Bi-directional Multi Dimension CAP Transmission for Smart Grid Communication Services

    DEFF Research Database (Denmark)

    Zhang, Xu; Binti Othman, Maisara; Pang, Xiaodan;

    2012-01-01

    We experimentally demonstrate bi-directional multi dimension carrierless amplitude and phase (CAP) transmission for smart grid communication services based on optical fiber networks. The proposed system is able to support multi-Gb/s transmission with high spectral efficiency.......We experimentally demonstrate bi-directional multi dimension carrierless amplitude and phase (CAP) transmission for smart grid communication services based on optical fiber networks. The proposed system is able to support multi-Gb/s transmission with high spectral efficiency....

  4. Exploiting Outage and Error Probability of Cooperative Incremental Relaying in Underwater Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Hina Nasir

    2016-07-01

    Full Text Available This paper embeds a bi-fold contribution for Underwater Wireless Sensor Networks (UWSNs; performance analysis of incremental relaying in terms of outage and error probability, and based on the analysis proposition of two new cooperative routing protocols. Subject to the first contribution, a three step procedure is carried out; a system model is presented, the number of available relays are determined, and based on cooperative incremental retransmission methodology, closed-form expressions for outage and error probability are derived. Subject to the second contribution, Adaptive Cooperation in Energy (ACE efficient depth based routing and Enhanced-ACE (E-ACE are presented. In the proposed model, feedback mechanism indicates success or failure of data transmission. If direct transmission is successful, there is no need for relaying by cooperative relay nodes. In case of failure, all the available relays retransmit the data one by one till the desired signal quality is achieved at destination. Simulation results show that the ACE and E-ACE significantly improves network performance, i.e., throughput, when compared with other incremental relaying protocols like Cooperative Automatic Repeat reQuest (CARQ. E-ACE and ACE achieve 69% and 63% more throughput respectively as compared to CARQ in hard underwater environment.

  5. REDUCING TRANSMITTED POWER OF MOVING RELAY NODE IN LONG-TERM EVOLUTION-ADVANCED CELLULAR NETWORKS

    Directory of Open Access Journals (Sweden)

    Jaafar A. Aldhaibani

    2014-01-01

    Full Text Available Wireless multi-hop relay networks have become very significant technologies in mobile communications. These networks ensure data rate transfer and coverage extension with a low cost. In this study two types of relay are studied; Fixed Relay Node (FRN and Moving Relay Node (MRN. Where system analyses for uplink and downlink transmission are derived in this study. Moreover the optimal relay location of FRN was proposed to provide a maximum achievable rate at user in cell edge region. Finally, a new algorithm was suggested to balance and control on the transmitted power of MRN over cell size to provide the required SNR and throughput at the users inside vehicle with reducing the consumption transmitted relay power. Numerical results indicate an enhancement in received signal strength for users at the cell edge from (-90 to -65 dBm and 40% increment from all cell size after deploying FRN at proposed locations. As well as, the results revealed that there is saving nearly 75% from transmitted power in MRN after using proposed algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain.

  6. Exploiting Outage and Error Probability of Cooperative Incremental Relaying in Underwater Wireless Sensor Networks.

    Science.gov (United States)

    Nasir, Hina; Javaid, Nadeem; Sher, Muhammad; Qasim, Umar; Khan, Zahoor Ali; Alrajeh, Nabil; Niaz, Iftikhar Azim

    2016-01-01

    This paper embeds a bi-fold contribution for Underwater Wireless Sensor Networks (UWSNs); performance analysis of incremental relaying in terms of outage and error probability, and based on the analysis proposition of two new cooperative routing protocols. Subject to the first contribution, a three step procedure is carried out; a system model is presented, the number of available relays are determined, and based on cooperative incremental retransmission methodology, closed-form expressions for outage and error probability are derived. Subject to the second contribution, Adaptive Cooperation in Energy (ACE) efficient depth based routing and Enhanced-ACE (E-ACE) are presented. In the proposed model, feedback mechanism indicates success or failure of data transmission. If direct transmission is successful, there is no need for relaying by cooperative relay nodes. In case of failure, all the available relays retransmit the data one by one till the desired signal quality is achieved at destination. Simulation results show that the ACE and E-ACE significantly improves network performance, i.e., throughput, when compared with other incremental relaying protocols like Cooperative Automatic Repeat reQuest (CARQ). E-ACE and ACE achieve 69% and 63% more throughput respectively as compared to CARQ in hard underwater environment. PMID:27420061

  7. Exploiting Outage and Error Probability of Cooperative Incremental Relaying in Underwater Wireless Sensor Networks

    Science.gov (United States)

    Nasir, Hina; Javaid, Nadeem; Sher, Muhammad; Qasim, Umar; Khan, Zahoor Ali; Alrajeh, Nabil; Niaz, Iftikhar Azim

    2016-01-01

    This paper embeds a bi-fold contribution for Underwater Wireless Sensor Networks (UWSNs); performance analysis of incremental relaying in terms of outage and error probability, and based on the analysis proposition of two new cooperative routing protocols. Subject to the first contribution, a three step procedure is carried out; a system model is presented, the number of available relays are determined, and based on cooperative incremental retransmission methodology, closed-form expressions for outage and error probability are derived. Subject to the second contribution, Adaptive Cooperation in Energy (ACE) efficient depth based routing and Enhanced-ACE (E-ACE) are presented. In the proposed model, feedback mechanism indicates success or failure of data transmission. If direct transmission is successful, there is no need for relaying by cooperative relay nodes. In case of failure, all the available relays retransmit the data one by one till the desired signal quality is achieved at destination. Simulation results show that the ACE and E-ACE significantly improves network performance, i.e., throughput, when compared with other incremental relaying protocols like Cooperative Automatic Repeat reQuest (CARQ). E-ACE and ACE achieve 69% and 63% more throughput respectively as compared to CARQ in hard underwater environment. PMID:27420061

  8. RoCoMAR: robots' controllable mobility aided routing and relay architecture for mobile sensor networks.

    Science.gov (United States)

    Le, Duc Van; Oh, Hoon; Yoon, Seokhoon

    2013-01-01

    In a practical deployment, mobile sensor network (MSN) suffers from a low performance due to high node mobility, time-varying wireless channel properties, and obstacles between communicating nodes. In order to tackle the problem of low network performance and provide a desired end-to-end data transfer quality, in this paper we propose a novel ad hoc routing and relaying architecture, namely RoCoMAR (Robots' Controllable Mobility Aided Routing) that uses robotic nodes' controllable mobility. RoCoMAR repeatedly performs link reinforcement process with the objective of maximizing the network throughput, in which the link with the lowest quality on the path is identified and replaced with high quality links by placing a robotic node as a relay at an optimal position. The robotic node resigns as a relay if the objective is achieved or no more gain can be obtained with a new relay. Once placed as a relay, the robotic node performs adaptive link maintenance by adjusting its position according to the movements of regular nodes. The simulation results show that RoCoMAR outperforms existing ad hoc routing protocols for MSN in terms of network throughput and end-to-end delay. PMID:23881134

  9. Joint Network Coding and Opportunistic Scheduling for the Bidirectional Relay Channel

    KAUST Repository

    Shaqfeh, Mohammad

    2013-05-27

    In this paper, we consider a two-way communication system in which two users communicate with each other through an intermediate relay over block-fading channels. We investigate the optimal opportunistic scheduling scheme in order to maximize the long-term average transmission rate in the system assuming symmetric information flow between the two users. Based on the channel state information, the scheduler decides that either one of the users transmits to the relay, or the relay transmits to a single user or broadcasts to both users a combined version of the two users’ transmitted information by using linear network coding. We obtain the optimal scheduling scheme by using the Lagrangian dual problem. Furthermore, in order to characterize the gains of network coding and opportunistic scheduling, we compare the achievable rate of the system versus suboptimal schemes in which the gains of network coding and opportunistic scheduling are partially exploited.

  10. Impact of joint resource partitioning and routing on performance of relay enhanced cellular networks

    Institute of Scientific and Technical Information of China (English)

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

    2008-01-01

    Radio resource assignment schemes and routing strategies in relay enhanced cellular networks are proposed in this paper. Under the reuse partitioning-based frequency planning framework, the intra-cell re-source partitioning between the base station and relay nodes was addressed firstly by introducing a metric of ef-fective reuse factor. Then, coverage-oriented and capacity-oriented routings, as well as two link bandwidth as-signment schemes" equal-bandwidth per link" and " equal-bandwidth per mobile station" were developed.These key issues and their impacts on the system performance were analyzed comprehensively and supported by simulations. Results show that the cell capacity and edge user throughput of the proposed network are superior to the traditional non-relay network when an appropriate effective reuse factor is adopted.

  11. High-Rate, Distributed Training-Embedded Complex Orthogonal Designs for Relay Networks

    CERN Document Server

    Harshan, J; Hjørungnes, Are

    2009-01-01

    Distributed Space-Time Block Codes (DSTBCs) from Complex Orthogonal Designs (CODs) (both square and non-square CODs other than the Alamouti design) are known to lose their single-symbol ML decodable (SSD) property when used in two-hop wireless relay networks using amplify and forward protocol. For such a network, in this paper, a new class of high rate, training-embedded (TE) SSD DSTBCs are constructed from TE-CODs. The proposed codes include the training symbols in the structure of the code which is shown to be the key point to obtain high rate as well as the SSD property. TE-CODs are shown to offer full-diversity for arbitrary complex constellations. Non-square TE-CODs are shown to provide higher rates (in symbols per channel use) compared to the known SSD DSTBCs for relay networks with number of relays less than $10.$

  12. Scalable DeNoise-and-Forward in Bidirectional Relay Networks

    DEFF Research Database (Denmark)

    Sørensen, Jesper Hemming; Krigslund, Rasmus; Popovski, Petar;

    2010-01-01

    in order to save transmissions. To ensure decodability at the end-nodes, a priori information about the content of the combined packets must be available. This is gathered during the initial transmissions to the relay. The trade-off between decodability and number of necessary transmissions is analysed...... and simulations show, that S-DNF is able to provide a better trade-off than traditional schemes at high SNR....

  13. Resource Partitioning with Beamforming for the Decode-Forward Relay Networks

    Directory of Open Access Journals (Sweden)

    Hwang Duckdong

    2008-01-01

    Full Text Available A joint power and time slot partitioning scheme based on the channel status information (CSI is proposed for networks of multiple relays using decode and forward (DF protocol. A set of power constraints for the famous water pouring method is presented depending on the time slot partitioning and CSI. Optimizing the timing and the power distributions enhances the network throughput in addition to the diversity advantage well known for the open loop relay protocols. Beamforming techniques for the source or destination with multiple antennas are also proposed and utilized in the partitioning process.

  14. Efficient Algorithm for Power Allocation in Relay-based Cognitive Radio Network

    Directory of Open Access Journals (Sweden)

    N. Ferdous

    2011-12-01

    Full Text Available This paper addresses a cognitive radio (CR network scenario where a relay is assigned to mitigate interference to primary users (PUs. We develop an average probability of successful secondary transmission (PSST to introduce relay in the CR network. The power allocation is done using dual domain concept to maximize the system throughput as well as maintaining interference to an acceptable level and this approach is implemented in our paper that has a higher convergence rate. Furthermore, we propose an alternative approach that maintains a high throughput and at the same time reduces the computational complexity significantly. A detailed analysis is done before simulation. The simulated results validate the theoretical analysis.

  15. Full-diversity partial interference cancellation for multi-user wireless relaying networks

    KAUST Repository

    El Astal, M. T O

    2013-12-01

    We focus on the uplink channel of multi-user wireless relaying networks in a coverage extension scenario. The network consists of two users, a single half duplex (HD) relay and a destination, all equipped with multiple antennas. Perfect channel state information (CSI) is assumed to be available exclusively at the receiving nodes (i.e., the relay and the destination) while the users are assumed to be completely blind. The communication through the considered network takes place over two phases. During the first phase, both users send their information concurrently to the relay. The second phase consists of decoding the received data and forwarding it simultaneously to the destination. A transmission scheme that achieves full-diversity under partial interference cancellation (PIC) group decoding is proposed. Unlike many existing schemes, it allows the concurrent transmission in both phases while achieving the full-diversity gain of full time division multiple access (TDMA) transmission regardless of the number of antennas at each node. Numerical comparison with existing schemes in the literature is provided to corroborate our theoretical claims. It is found that our interference cancellation (IC) scheme clearly outperforms existing schemes at the expense of an affordable increase in decoding complexity at both of the relay and destination. © 2013 IEEE.

  16. Asymptotic Analysis of Large Cooperative Relay Networks Using Random Matrix Theory

    Directory of Open Access Journals (Sweden)

    H. Poor

    2008-04-01

    Full Text Available Cooperative transmission is an emerging communication technology that takes advantage of the broadcast nature of wireless channels. In cooperative transmission, the use of relays can create a virtual antenna array so that multiple-input/multiple-output (MIMO techniques can be employed. Most existing work in this area has focused on the situation in which there are a small number of sources and relays and a destination. In this paper, cooperative relay networks with large numbers of nodes are analyzed, and in particular the asymptotic performance improvement of cooperative transmission over direction transmission and relay transmission is analyzed using random matrix theory. The key idea is to investigate the eigenvalue distributions related to channel capacity and to analyze the moments of this distribution in large wireless networks. A performance upper bound is derived, the performance in the low signal-to-noise-ratio regime is analyzed, and two approximations are obtained for high and low relay-to-destination link qualities, respectively. Finally, simulations are provided to validate the accuracy of the analytical results. The analysis in this paper provides important tools for the understanding and the design of large cooperative wireless networks.

  17. Orthogonal DF Cooperative Relay Networks with Multiple-SNR Thresholds and Multiple Hard-Decision Detections

    Directory of Open Access Journals (Sweden)

    Nguyen HaH

    2010-01-01

    Full Text Available This paper investigates a wireless cooperative relay network with multiple relays communicating with the destination over orthogonal channels. Proposed is a cooperative transmission scheme that employs two signal-to-noise ratio (SNR thresholds and multiple hard-decision detections (HDD at the destination. One SNR threshold is used to select transmitting relays, and the other threshold is used at the destination for detection. Then the destination simply combines all the hard-decision results and makes the final binary decision based on majority voting. Focusing on the decode-and-forward (DF relaying protocol, the average bit error probability is derived and diversity analysis is carried out. It is shown that the full diversity order can be achieved by setting appropriate thresholds even when the destination does not know the exact or average SNRs of the source-relay links. The performance analysis is further extended to multi-hop cooperation and/or with the presence of a direct link where multiple thresholds are needed. By combining the multiple-SNR threshold method with a selection of the best relaying link, a high spectral-efficiency cooperative transmission scheme is further presented. Simulation results verify the theoretical analysis and demonstrate performance advantage of our proposed schemes over the existing ones.

  18. Joint Subcarrier Pairing and Resource Allocation for Cognitive Network and Adaptive Relaying Strategy

    KAUST Repository

    Soury, Hamza

    2012-05-01

    Recent measurements show that the spectrum is under-utilized by licensed users in wireless communication. Cognitive radio (CR) has been proposed as a suitable solution to manage the inefficient usage of the spectrum and increase coverage area of wireless networks. The concept is based on allowing a group of secondary users (SUs) to share the unused radio spectrum originally owned by the primary user (PUs). The operation of CR should not cause harmful interference to the PUs. In the other hand, relayed transmission increases the coverage and achievable capacity of communication systems and in particular in CR systems. In fact there are many types of cooperative communications, however the two main ones are decode-and-forward (DAF) and amplify-and-forward (AAF). 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. In this dissertation, we investigate the power allocation for an adaptive relaying protocol (ARP) scheme in cognitive system by maximizing the end-to-end rate and searching the best carriers pairing distribution. The optimization problem is under the interference and power budget constraints. The simulation results confirm the efficiency of the proposed adaptive relaying protocol in comparison to other relaying techniques, and the consequence of the choice of the pairing strategy.

  19. Block compressed sensing for feedback reduction in relay-aided multiuser full duplex networks

    KAUST Repository

    Elkhalil, Khalil

    2016-08-11

    Opportunistic user selection is a simple technique that exploits the spatial diversity in multiuser relay-aided networks. Nonetheless, channel state information (CSI) from all users (and cooperating relays) is generally required at a central node in order to make selection decisions. Practically, CSI acquisition generates a great deal of feedback overhead that could result in significant transmission delays. In addition to this, the presence of a full-duplex cooperating relay corrupts the fed back CSI by additive noise and the relay\\'s loop (or self) interference. This could lead to transmission outages if user selection is based on inaccurate feedback information. In this paper, we propose an opportunistic full-duplex feedback algorithm that tackles the above challenges. We cast the problem of joint user signal-to-noise ratio (SNR) and the relay loop interference estimation at the base-station as a block sparse signal recovery problem in compressive sensing (CS). Using existing CS block recovery algorithms, the identity of the strong users is obtained and their corresponding SNRs are estimated. Numerical results show that the proposed technique drastically reduces the feedback overhead and achieves a rate close to that obtained by techniques that require dedicated error-free feedback from all users. Numerical results also show that there is a trade-off between the feedback interference and load, and for short coherence intervals, full-duplex feedback achieves higher throughput when compared to interference-free (half-duplex) feedback. © 2016 IEEE.

  20. A Relaying Incentive Scheme in Multihop Cellular Networks Based on Coalitional Game with Externalities

    CERN Document Server

    Li, Cuilian; Tian, Feng

    2008-01-01

    Cooperative multihop communication can greatly increase network throughput, yet packet forwarding for other nodes involves opportunity and energy cost for relays. Thus one of the pre-requisite problems in the successful implementation of multihop transmission is how to foster cooperation among selfish nodes. Existing researches mainly adopt monetary stimulating. In this manuscript, we propose instead a simple and self-enforcing forwarding incentive scheme free of indirect monetary remunerating for asymmetric (uplink multihop, downlink single-hop) cellar network based on coalitional game theory, which comprises double compensation, namely, Inter- BEA, global stimulating policy allotting resources among relaying coalitions according to group size, and Intra-BEA, local compensating and allocating rule within coalitions. Firstly, given the global allotting policy, we introduce a fair allocation estimating approach which includes remunerating for relaying cost using Myerson value for partition function game, to en...

  1. Parity-Check Network Coding for Multiple Access Relay Channel in Wireless Sensor Cooperative Communications

    OpenAIRE

    Bing Du; Jun Zhang

    2010-01-01

    A recently developed theory suggests that network coding is a generalization of source coding and channel coding and thus yields a significant performance improvement in terms of throughput and spatial diversity. This paper proposes a cooperative design of a parity-check network coding scheme in the context of a two-source multiple access relay channel (MARC) model, a common compact model in hierarchical wireless sensor networks (WSNs). The scheme uses Low-Density Parity-Check (LDPC) as the ...

  2. Low-Complexity Near-Optimal Codes for Gaussian Relay Networks

    CERN Document Server

    Dikaliotis, Theodoros K; Avestimehr, Salman; Jaggi, Sidharth; Ho, Tracey

    2011-01-01

    We consider the problem of information flow over Gaussian relay networks. Similar to the recent work by Avestimehr \\emph{et al.} [1], we propose network codes that achieve up to a constant gap from the capacity of such networks. However, our proposed codes are also computationally tractable. Our main technique is to use the codes of Avestimehr \\emph{et al.} as inner codes in a concatenated coding scheme.

  3. Joint Channel and Network Decoding for XOR-Based Relay in Multi-Access Channel

    Science.gov (United States)

    Tang, Suhua; Cheng, Jun; Sun, Chen; Miura, Ryu; Obana, Sadao

    In this paper network coding based relay for multi-access channel is studied. In the system, two nodes send messages to a common access point (AP). A relay assists the two nodes by forwarding a network coded version of the messages. The AP performs joint channel and network decoding to recover the two original messages from three received signals. Two schemes, soft network coding (SoftNC) and turbo network coding (TurboNC), both focusing on bitwise exclusive or (XOR) based network coding, are proposed to salvage messages from erroneous signals. SoftNC is simple and backward compatible with existing protocol stack of wireless networks, and reduces packet errors by maximal ratio combining (MRC). TurboNC improves channel efficiency by letting the relay node transmit only parity check bits of the interleaved XORed message, where reliability is retained by iterative decoding. Simulation results show that compared with the network-layer path diversity scheme [8], both SoftNC and TurboNC greatly improve the reliability, and TurboNC also achieves a much higher throughput. The proposed schemes are suitable for improving the performance of wireless local area networks (WLAN).

  4. A digital interface for Gaussian relay and interference networks: Lifting codes from the discrete superposition model

    CERN Document Server

    Anand, M

    2010-01-01

    For every Gaussian network, there exists a corresponding deterministic network called the discrete superposition network. We show that this discrete superposition network provides a near-optimal digital interface for operating a class of Gaussian networks in the sense that any code for the discrete superposition network can be naturally lifted to a corresponding code for the Gaussian network, while achieving a rate that is at most a constant number of bits lesser than the rate it achieves for discrete superposition network. This constant depends only on the number of nodes in the network and not on the channel gains or SNR. Moreover the capacities of the two networks are within a constant of each other, again independent of channel gains and SNR. The class of Gaussian networks for which this property holds includes relay networks with a single source-destination pair, interference networks, multicast networks, and the MIMO counterparts of these networks. The capacity of the Gaussian relay network with a singl...

  5. Conflict-Aware Relay Selection for Multicast in MUD based Wireless Networks

    Directory of Open Access Journals (Sweden)

    Asma Ben Hassouna

    2013-04-01

    Full Text Available Multipoint Relays (MPR [1] selection is a good step toward building a very proficient routing scheme for multicast/broadcast communications. It considers the fact that data transmitted by a node is overheard by all the users in the sender’s communication range, called the Wireless Broadcast Advantage (WBA [2][4][6]. However, when a node elects its MPR nodes it does not consider their channel qualities (i.e. they do not consider the Multi-User Diversity (MUD [3][5] factor, that has a significant influence on the network performance. Many other works consider the MUD and the rate adaptation (RA features [15][16]. However these works are distorted by severe simplifications that are made about some common wireless network problems such as: the number of transmissions, the access scheduling, the interference conflicts, etc. In this paper, we introduce three new MUD, WBA and RA based relay selection schemes. The first one proposed, called the Efficient Multi-user Diversity based Relay (E-MDR selection scheme,  is done over steps by exploiting the channel qualities in term of maximum achievable data rate (or channel capacity. The proposed EMDR based flooding strategy achieves the best multicast throughput without considering concurrent transmissions. It aims jointly (i to reduce the number of relays, (ii to maximize the throughput of each single multicast session (or partition, (iii to reduce the number of transmissions, (iv to exploit extremely the offered link capacities and as a consequence (v to enhance the allover network throughput. The second MUD, WBA and RA based relay selection scheme, called the Conflict free Multi-user Diversity based Relay (C-MDR selection scheme, performs relay selection with consideration of the interference factor. It targets (i to select relay nodes and their data transmission rates that maximize the multicast throughput, (ii to consider the effect of access scheduling when choosing relay nodes and (iii to resolve

  6. Parity-Check Network Coding for Multiple Access Relay Channel in Wireless Sensor Cooperative Communications

    Directory of Open Access Journals (Sweden)

    Du Bing

    2010-01-01

    Full Text Available A recently developed theory suggests that network coding is a generalization of source coding and channel coding and thus yields a significant performance improvement in terms of throughput and spatial diversity. This paper proposes a cooperative design of a parity-check network coding scheme in the context of a two-source multiple access relay channel (MARC model, a common compact model in hierarchical wireless sensor networks (WSNs. The scheme uses Low-Density Parity-Check (LDPC as the surrogate to build up a layered structure which encapsulates the multiple constituent LDPC codes in the source and relay nodes. Specifically, the relay node decodes the messages from two sources, which are used to generate extra parity-check bits by a random network coding procedure to fill up the rate gap between Source-Relay and Source-Destination transmissions. Then, we derived the key algebraic relationships among multidimensional LDPC constituent codes as one of the constraints for code profile optimization. These extra check bits are sent to the destination to realize a cooperative diversity as well as to approach MARC decode-and-forward (DF capacity.

  7. A Java based Implementation of a Network Level Information Model for the ATM / Frame Relay Interconnection

    OpenAIRE

    State, Radu; Nataf, Emmanuel; Festor, Olivier

    2000-01-01

    In this presentation, we illustrate the use of the Java technology to implement a network information model which captures the essence of the ATM and Frame Relay Interconnection. We show how the TMN concepts stay valid and how the existing and extended information models can be reused and implemented according to the TMN principles in a full Java environment.

  8. Approximate Capacity of Gaussian Interference-Relay Networks with Weak Cross Links

    CERN Document Server

    Mohajer, Soheil; Fragouli, Christina; Tse, David N C

    2010-01-01

    In this paper we study a Gaussian relay-interference network, in which relay (helper) nodes are to facilitate competing information flows over a wireless network. We focus on a two-stage relay-interference network where there are weak cross-links, causing the networks to behave like a chain of Z Gaussian channels. For these Gaussian ZZ and ZS networks, we establish an approximate characterization of the rate region. The outer bounds to the capacity region are established using genie-aided techniques that yield bounds sharper than the traditional cut-set outer bounds. For the inner bound of the ZZ network, we propose a new interference management scheme, termed interference neutralization, which is implemented using structured lattice codes. This technique allows for over-the-air interference removal, without the transmitters having complete access the interfering signals. For both the ZZ and ZS networks, we establish a new network decomposition technique that (approximately) achieves the capacity region. We u...

  9. Location-quality-aware policy optimisation for relay selection in mobile networks

    DEFF Research Database (Denmark)

    Nielsen, Jimmy Jessen; Olsen, Rasmus Løvenstein; Madsen, Tatiana Kozlova;

    2016-01-01

    the joint influence of these two factors in the decision process for the example of a mobile location-based relay selection approach using a continuous time Markov chain model. Efficient algorithms are developed based on this model to obtain optimal relay policies under consideration of localization errors...... mobility and propagation models illustrates the applicability of the model-based policy optimizations for realistic scenarios.......In order to perform location-based network optimization, the necessary decision information such as current location needs to be collected from the mobile nodes. The accuracy of the decision information, as e.g. influenced by the localization solution, is one of the influencing factors...

  10. Relay selection and resource allocation for two-way DF-AF cognitive radio networks

    KAUST Repository

    Alsharoa, Ahmad M.

    2013-08-01

    In this letter, the problem of relay selection and optimal resource allocation for two-way relaying cognitive radio networks using half duplex amplify-and-forward and decode-and-forward protocols is investigated. The primary and secondary users are assumed to access the spectrum simultaneously, in a way that the interference introduced to the primary users should be below a certain tolerated limit. Dual decomposition and subgradient methods are used to find the optimal power allocation. A suboptimal approach based on a genetic algorithm is also presented. Simulation results show that the proposed suboptimal algorithm offers a performance close to the optimal performance with a considerable complexity saving. © 2013 IEEE.

  11. AUTONOMOUS MOVEMENT OF MOBILE RELAYS IN WIRELESS SENSOR NETWORK TO ENHANCE NETWORK LIFETIME

    Directory of Open Access Journals (Sweden)

    Regis W. Anne

    2014-06-01

    Full Text Available Wireless Sensor Network (WSN is a collection of intelligent sensors that communicate and coordinate in an energy constrained environment. Due to the limited energy supply of the sensors, lifetime problems arise in static WSN. One of the potential solutions to this problem is a mobility-assisted WSN. Mobility can be introduced by adding extra entities like mobile sinks, mobile cluster-head or mobile relays (MRs to the existing static WSN. The entities can significantly improve the functionality and performance of the WSN by making it flexible to failures, ease data collection, increase energy efficiency, enhance connectivity, improve coverage and prolong network lifetime. The need of today’s applications demands mobility-assisted WSN instead of the traditional static WSN. In this paper, we control the movement of MRs to maximize network lifetime. A distributed algorithm for controlling the movement of MRs is given and its performance is validated for the network parameters such as network lifetime and average residual energy. The proposed method shows that lifetime can be improved compared to that of a static network.

  12. Attempt of automated space network operations at ETS-VI experimental data relay system

    Science.gov (United States)

    Ishihara, Kiyoomi; Sugawara, Masayuki

    1994-01-01

    National Space Development Agency of Japan (NASDA) is to perform experimental operations to acquire necessary technology for the future inter-satellite communications configured with a data relay satellite. This paper intends to overview functions of the experimental ground system which NASDA has developed for the Engineering Test Satellite VI (ETS-VI) Data Relay and Tracking Experiment, and to introduce Space Network System Operations Procedure (SNSOP) method with an example of Ka-band Single Access (KSA) acquisition sequence. To reduce operational load, SNSOP is developed with the concept of automated control and monitor of both ground terminal and data relay satellite. To perform acquisition and tracking operations fluently, the information exchange with user spacecraft controllers is automated by SNSOP functions.

  13. Energy efficient design for MIMO two-way AF multiple relay networks

    KAUST Repository

    Alsharoa, Ahmad M.

    2014-04-01

    This paper studies the energy efficient transmission and the power allocation problem for multiple two-way relay networks equipped with multi-input multi-output antennas where each relay employs an amplify-and-forward strategy. The goal is to minimize the total power consumption without degrading the quality of service of the terminals. In our analysis, we start by deriving closed-form expressions of the optimal powers allocated to terminals. We then employ a strong optimization tool based on the particle swarm optimization technique to find the optimal power allocated at each relay antenna. Our numerical results illustrate the performance of the proposed scheme and show that it achieves a sub-optimal solution very close to the optimal one.

  14. Training-Embedded, Single-Symbol ML-Decodable, Distributed STBCs for Relay Networks

    CERN Document Server

    Harshan, J; Hjørungnes, Are

    2009-01-01

    Recently, a special class of complex designs called Training-Embedded Complex Orthogonal Designs (TE-CODs) has been introduced to construct single-symbol Maximum Likelihood (ML) decodable (SSD) distributed space-time block codes (DSTBCs) for two-hop wireless relay networks using the amplify and forward protocol. However, to implement DSTBCs from square TE-CODs, the overhead due to the transmission of training symbols becomes prohibitively large as the number of relays increase. In this paper, we propose TE-Coordinate Interleaved Orthogonal Designs (TE-CIODs) to construct SSD DSTBCs. Exploiting the block diagonal structure of TE-CIODs, we show that, the overhead due to the transmission of training symbols to implement DSTBCs from TE-CIODs is smaller than that for TE-CODs. We also show that DSTBCs from TE-CIODs offer higher rate than those from TE-CODs for identical number of relays while maintaining the SSD and full-diversity properties.

  15. Energy Efficiency Analysis of a Two Dimensional Cooperative Wireless Sensor Network with Relay Selection

    Directory of Open Access Journals (Sweden)

    M. Kakitani

    2013-06-01

    Full Text Available The energy efficiency of non-cooperative and cooperative transmissions are investigated in a two-dimensional wireless sensor network, considering a target outage probability and the same end-to-end throughput for all transmission schemes. The impact of the relay selection method in the cooperative schemes is also analyzed. We show that under non line-of-sight conditions the relay selection method has a greater impact in the energy efficiency than the availability of a return channel. By its turn, under line-of-sight conditions a return channel is more valuable to the energy efficiency of cooperative transmission than the specific relay selection method. Finally, we demonstrate that the energy efficiency advantage of the cooperative over the non-cooperative transmission increases with the distance among nodes and with the nodes density.

  16. Double-layer video transmission over decode-and-forward wireless relay networks using hierarchical modulation.

    Science.gov (United States)

    Nguyen, Tu V; Cosman, Pamela C; Milstein, Laurence B

    2014-04-01

    We consider a wireless relay network with a single source, a single destination, and a multiple relay. The relays are half-duplex and use the decode-and-forward protocol. The transmit source is a layered video bitstream, which can be partitioned into two layers, a base layer (BL) and an enhancement layer (EL), where the BL is more important than the EL in terms of the source distortion. The source broadcasts both layers to the relays and the destination using hierarchical 16-QAM. Each relay detects and transmits successfully decoded layers to the destination using either hierarchical 16-QAM or QPSK. The destination can thus receive multiple signals, each of which can include either only the BL or both the BL and the EL. We derive the optimal linear combining method at the destination, where the uncoded bit error rate is minimized. We also present a suboptimal combining method with a closed-form solution, which performs very close to the optimal. We use the proposed double-layer transmission scheme with our combining methods for transmitting layered video bitstreams. Numerical results show that the double-layer scheme can gain 2-2.5 dB in channel signal-to-noise ratio or 5-7 dB in video peak signal-to-noise ratio, compared with the classical single-layer scheme using conventional modulation. PMID:24808347

  17. Joint Virtual MIMO and Network Coding Scheme with Superposition ARQ in Relay System

    Directory of Open Access Journals (Sweden)

    Shi Shijie

    2013-09-01

    Full Text Available A new two-way transmission protocol termed VMNC-SARQ (Virtual MIMO Network Coding with Superposition ARQ was proposed in this paper, which could improve throughput efficiency of DF (Decode-and Forward relay network signally. In first step, two single-antenna nodes send messages to the double-antenna relay station simultaneously by using a method similar to 2×2 VBLAST (Vertical Bell Laboratories Layered Space Time system. In step two, relay station processes the decoded signals received from two source nodes through Network Coding, and then broadcasts the combined messages with Alamouti Coding. A novel retransmission strategy will be implemented when demodulation and decoding failure presents. In order to reduce retransmission overhead, we attach the retransmitted packet to the latter normal packet by using higher modulation, and exploit the confidence value of previously error packet to help to recover both packets. Theoretical analysis and simulation results show that the proposed scheme could greatly improve end-to-end throughput efficiency for two-way relaying systems

  18. Relay Protection Coordination for Photovoltaic Power Plant Connected on Distribution Network

    OpenAIRE

    Nikolovski, Srete; Papuga, Vanja; Knežević, Goran

    2014-01-01

    This paper presents a procedure and computation of relay protection coordination for a PV power plant connected to the distribution network. In recent years, the growing concern for environment preservation has caused expansion of photovoltaic PV power plants in distribution networks. Numerical computer simulation is an indispensable tool for studying photovoltaic (PV) systems protection coordination. In this paper, EasyPower computer program is used with the module Power Protector. Time-curr...

  19. Cooperative relaying protocols and distributed coding schemes for wireless multiterminal networks

    OpenAIRE

    Mohamad, Abdulaziz

    2016-01-01

    With the rapid growth of wireless technologies, devices and mobile applications, the quest of high throughput and omnipresent connectivity in wireless networks increases rapidly as well. It is well known that cooperation increases significantly the spectral efficiency (coding gain) and the reliability (diversity gain) of the transmission between the nodes. The concept of cooperation in wireless relays network is still one of the most active research topics in wireless communication, scientist...

  20. A New Method for Setting Calculation Sequence of Directional Relay Protection in Multi-Loop Networks

    Science.gov (United States)

    Haijun, Xiong; Qi, Zhang

    2016-08-01

    Workload of relay protection setting calculation in multi-loop networks may be reduced effectively by optimization setting calculation sequences. A new method of setting calculation sequences of directional distance relay protection in multi-loop networks based on minimum broken nodes cost vector (MBNCV) was proposed to solve the problem experienced in current methods. Existing methods based on minimum breakpoint set (MBPS) lead to more break edges when untying the loops in dependent relationships of relays leading to possibly more iterative calculation workloads in setting calculations. A model driven approach based on behavior trees (BT) was presented to improve adaptability of similar problems. After extending the BT model by adding real-time system characters, timed BT was derived and the dependency relationship in multi-loop networks was then modeled. The model was translated into communication sequence process (CSP) models and an optimization setting calculation sequence in multi-loop networks was finally calculated by tools. A 5-nodes multi-loop network was applied as an example to demonstrate effectiveness of the modeling and calculation method. Several examples were then calculated with results indicating the method effectively reduces the number of forced broken edges for protection setting calculation in multi-loop networks.

  1. Optimal Relay Selection using Efficient Beaconless Geographic Contention-Based Routing Protocol in Wireless Adhoc Networks

    Directory of Open Access Journals (Sweden)

    G. Srimathy

    2012-04-01

    Full Text Available In Wireless Ad hoc network, cooperation of nodes can be achieved by more interactions at higher protocol layers, particularly the MAC (Medium Access Control and network layers play vital role. MAC facilitates a routing protocol based on position location of nodes at network layer specially known as Beacon-less geographic routing (BLGR using Contention-based selection process. This paper proposes two levels of cross-layer framework -a MAC network cross-layer design for forwarder selection (or routing and a MAC-PHY for relay selection. CoopGeo; the proposed cross-layer protocol provides an efficient, distributed approach to select next hops and optimal relays to form a communication path. Wireless networks suffers huge number of communication at the same time leads to increase in collision and energy consumption; hence focused on new Contention access method that uses a dynamical change of channel access probability which can reduce the number of contention times and collisions. Simulation result demonstrates the best Relay selection and the comparative of direct mode with the cooperative networks. And Performance evaluation of contention probability with Collision avoidance.

  2. Two-edge disjoint survivable network design problem with relays: a hybrid genetic algorithm and Lagrangian heuristic approach

    Science.gov (United States)

    Konak, Abdullah

    2014-01-01

    This article presents a network design problem with relays considering the two-edge network connectivity. The problem arises in telecommunications and logistic networks where a constraint is imposed on the distance that a commodity can travel on a route without being processed by a relay, and the survivability of the network is critical in case of a component failure. The network design problem involves selecting two-edge disjoint paths between source and destination node pairs and determining the location of relays to minimize the network design cost. The formulated problem is solved by a hybrid approach of a genetic algorithm (GA) and a Lagrangian heuristic such that the GA searches for two-edge disjoint paths for each commodity, and the Lagrangian heuristic is used to determine relays on these paths. The performance of the proposed hybrid approach is compared to the previous approaches from the literature, with promising results.

  3. Uplink capacity of multi-class IEEE 802.16j relay networks with adaptive modulation and coding

    DEFF Research Database (Denmark)

    Wang, Hua; Xiong, C; Iversen, Villy Bæk

    2009-01-01

    The emerging IEEE 802.16j mobile multi-hop relay (MMR) network is currently being developed to increase the user throughput and extend the service coverage as an enhancement of existing 802.16e standard. In 802.16j, the intermediate relay stations (RSs) help the base station (BS) communicate...

  4. Approximately universal, explicit DMT-optimal constructions for the dynamic-decode-and-forward cooperative wireless relay network

    CERN Document Server

    Elia, Petros

    2007-01-01

    Explicit codes are constructed that achieve the diversity-multiplexing gain tradeoff of the cooperative-relay channel under the dynamic decode-and-forward protocol for any network size, for all delays and for all numbers of transmit and receive antennas at the relays.

  5. Diversity-Multiplexing Tradeoff in Multi-Antenna Multi-Relay Networks: Improvements and Some Optimality Results

    CERN Document Server

    Gharan, Shahab Oveis; Khandani, Amir K

    2009-01-01

    This paper investigates the benefits of Amplify-and-Forward (AF) relaying in the setup of multi-antenna wireless networks. The concept of Random Sequential (RS) relaying is previously introduced in the literature and showed that it achieves the maximum diversity gain in a general multi-antenna network. Here, we show that random unitary matrix multiplication at the relay nodes empowers the RS scheme to achieve a better Diversity-Multiplexing Tradeoff (DMT) as compared to the traditional AF relaying. First, we study the case of a multi-antenna full-duplex single-relay two-hop network, for which we show that the RS achieves the optimum DMT. Applying this result, we derive a new achievable DMT for the case of multi-antenna half-duplex parallel relay network. Interestingly, it turns out that the DMT of the RS scheme is optimum for the case of multi-antenna two parallel non-interfering half-duplex relays. Next, we show that random unitary matrix multiplication also improves the DMT of the Non-Orthogonal AF relaying...

  6. Teach for America, Relay Graduate School, and the Charter School Networks: The Making of a Parallel Education Structure

    Science.gov (United States)

    Mungal, Angus Shiva

    2016-01-01

    In New York City, a partnership between Teach For America (TFA), the New York City Department of Education (NYCDOE), the Relay Graduate School of Education (Relay), and three charter school networks produced a "parallel education structure" within the public school system. Driving the partnership and the parallel education structure are…

  7. Efficient Distributed Authentication Key Scheme for Multi-hop Relay In IEEE 802.16j Network

    Directory of Open Access Journals (Sweden)

    ADNAN SHAHID KHAN,

    2010-06-01

    Full Text Available Relaying and cooperation have re-emerged as important research topic in the wireless communication over the past decade. IEEE 802.16j Multihop relay network is assiduously developing to accomplish high capacity services with large cell coverage. Considerable interest currently exists in the exploitation of Relay based Wimax. This is mainly the result of lower infrastructure cost and high data transfer rates compared to existing 3G. However due to lack of physical boundaries and injection of distributed relays, it is known to be morevulnerable to security holes as a trade off. In this paper we propose a new distributed authentication key scheme for Multihop Relays IEEE 802.16j network service. The propose scheme uses decode and forward relays with localized authentication. The scheme works in distributed authentication to authenticate Subscriber station (SS and Relay stations (RS at initial network entry. Our new efficient distributed scheme utilizes healthy security issues and the Multihop Relay network application features. Both analysis and performance evaluation shows that our scheme can significantly reduce the security holes as well as communication overheads.

  8. Performance analysis of best relay selection scheme for amplify-and-forward cooperative networks in identical Nakagami-m channels

    KAUST Repository

    Hussain, Syed Imtiaz

    2010-06-01

    In cooperative communication networks, the use of multiple relays between the source and the destination was proposed to increase the diversity gain. Since the source and all the relays must transmit on orthogonal channels, multiple relay cooperation is considered inefficient in terms of channel resources and bandwidth utilization. To overcome this problem, the concept of best relay selection was recently proposed. In this paper, we analyze the performance of the best relay selection scheme for a cooperative network with multiple relays operating in amplify-and-forward (AF) mode over identical Nakagami-m channels using exact source-relay-destination signal to noise ratio (SNR) expression. We derive accurate closed form expressions for various system parameters including probability density function (pdf) of end-to-end SNR, average output SNR, average probability of bit error and average channel capacity. T he analytical results are verified through extensive simulations. It is shown that the best relay selection scheme performs better than the regular all relay cooperation.

  9. Linear Time Approximation Algorithms for the Relay Node Placement Problem in Wireless Sensor Networks with Hexagon Tessellation

    Directory of Open Access Journals (Sweden)

    Chi-Chang Chen

    2015-01-01

    Full Text Available The relay node placement problem in wireless sensor network (WSN aims at deploying the minimum number of relay nodes over the network so that each sensor can communicate with at least one relay node. When the deployed relay nodes are homogeneous and their communication ranges are circular, one way to solve the WSN relay node placement problem is to solve the minimum geometric disk cover (MGDC problem first and place the relay nodes at the centers of the covering disks and then, if necessary, deploy additional relay nodes to meet the connection requirement of relay nodes. It is known that the MGDC problem is NP-complete. A novel linear time approximation algorithm for the MGDC problem is proposed, which identifies covering disks using the regular hexagon tessellation of the plane with bounded area. The approximation ratio of the proposed algorithm is (5+ϵ, where 0<ϵ≤15. Experimental results show that the worst case is rare, and on average the proposed algorithm uses less than 1.7 times the optimal disks of the MGDC problem. In cases where quick deployment is necessary, this study provides a fast 7-approximation algorithm which uses on average less than twice the optimal number of relay nodes in the simulation.

  10. A DISTRIBUTED COOPERATIVE RELAYING OPTIMIZATION SCHEME FOR SECONDARY TRANSMISSION IN COGNITIVE RADIO NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Chen Dan; Ji Hong

    2011-01-01

    In Cognitive Radio (CR) networks,cooperative communication has been recently regarded as a key technology for improving the spectral utilization efficiency and ensuring the Quality of Service (QoS) for Primary Users (PUs).In this paper,we propose a distributed joint relay selection and power allocation scheme for cooperative secondary transmission,taking both Instantaneous Channel State Information (I-CSI) and residual energy into consideration,where secondary source and destination may have different available spectrum.Specifically,we formulate the cognitive relay network as a restless bandit system,where the channel and energy state transition is characterized by the finite-state Markov chain.The proposed policy has indexability property that dramatically reduces the computation and implementation complexity.Analytical and simulation results demonstrate that our proposed scheme can efficiently enhance overall system reward,while guaranteeing a good tradeoff between achievable date rate and average network lifetime.

  11. Primary Traffic Based Cooperative Multihop Relaying with Preliminary Farthest Relay Selection in Cognitive Radio Ad Hoc Networks

    Science.gov (United States)

    Lin, I.-Te; Sasase, Iwao

    We propose a primary traffic based multihop relaying algorithm with cooperative transmission (PTBMR-CT). It enlarges the hop transmission distances to reduce the number of cognitive relays on the route from the cognitive source (CS) to the cognitive destination (CD). In each hop, from the cognitive nodes in a specified area depending on whether the primary source (PS) transmits data to the primary destination (PD), the cognitive node that is farthest away from the cognitive relay that sends data is selected as the other one that receives data. However, when the PS is transmitting data to the PD, from the cognitive nodes in a specified area, another cognitive node is also selected and prepared to be the cognitive relay that receives data of cooperative transmission. Cooperative transmission is performed if the PS is still transmitting data to the PD when the cognitive relay that receives data of the next hop transmission is being searched. Simulation results show that the average number of cognitive relays is reduced by PTBMR-CT compared to conventional primary traffic based farthest neighbor relaying (PTBFNR), and PTBMR-CT outperforms conventional PTBFNR in terms of the average end-to-end reliability, the average end-to-end throughput, the average required transmission power of transmitting data from the CS to the CD, and the average end-to-end transmission latency.

  12. Reuse Partitioning-Based Frequency Assignment in Fixed Two-Hop Relay Cellular Network

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In relay cellular network, relay links will consume extra frequency resources, which makes radio resource allocation become more complex and important. A new frequency allocation scheme is proposed to increase cell capacity and improve signal-to-interference ratio (SIR) of users located at cell edges. By dividing cell into different parts and configuring each of these parts with a unique reuse factor, this scheme improves spectral utilization efficiency and avoids inter-cell interference effectively. Optimal combinations of reuse factors and locations of relay nodes are also addressed and investigated. Computer simulation results show that, by employing the proposed scheme, maximum cell capacity gains of about 50%, 35% and 30% can be achieved in comparison with conventional cellular network scheme, traditional reuse partitioning scheme and reuse-adjacent-cell-frequencies scheme, respectively. Moreover, since in the proposed scheme resources are dynamically allocated among relay nodes, more benefits can be obtained in comparison with fixed resource allocation schemes under non-uniform traffic distribution.

  13. Energy-harvesting in cooperative AF relaying networks over log-normal fading channels

    KAUST Repository

    Rabie, Khaled M.

    2016-07-26

    Energy-harvesting (EH) and wireless power transfer are increasingly becoming a promising source of power in future wireless networks and have recently attracted a considerable amount of research, particularly on cooperative two-hop relay networks in Rayleigh fading channels. In contrast, this paper investigates the performance of wireless power transfer based two-hop cooperative relaying systems in indoor channels characterized by log-normal fading. Specifically, two EH protocols are considered here, namely, time switching relaying (TSR) and power splitting relaying (PSR). Our findings include accurate analytical expressions for the ergodic capacity and ergodic outage probability for the two aforementioned protocols. Monte Carlo simulations are used throughout to confirm the accuracy of our analysis. The results show that increasing the channel variance will always provide better ergodic capacity performance. It is also shown that a good selection of the EH time in the TSR protocol, and the power splitting factor in the PTS protocol, is the key to achieve the best system performance. © 2016 IEEE.

  14. A Matrix-Based Proactive Data Relay Algorithm for Large Distributed Sensor Networks

    Directory of Open Access Journals (Sweden)

    Yang Xu

    2016-08-01

    Full Text Available In large-scale distributed sensor networks, sensed data is required to be relayed around the network so that one or few sensors can gather adequate relative data to produce high quality information for decision-making. In regards to very high energy-constraint sensor nodes, data transmission should be extremely economical. However, traditional data delivery protocols are potentially inefficient relaying unpredictable sensor readings for data fusion in large distributed networks for either overwhelming query transmissions or unnecessary data coverage. By building sensors’ local model from their previously transmitted data in three matrixes, we have developed a novel energy-saving data relay algorithm, which allows sensors to proactively make broadcast decisions by using a neat matrix computation to provide balance between transmission and energy-saving. In addition, we designed a heuristic maintenance algorithm to efficiently update these three matrices. This can easily be deployed to large-scale mobile networks in which decisions of sensors are based on their local matrix models no matter how large the network is, and the local models of these sensors are updated constantly. Compared with some traditional approaches based on our simulations, the efficiency of this approach is manifested in uncertain environment. The results show that our approach is scalable and can effectively balance aggregating data with minimizing energy consumption.

  15. A Matrix-Based Proactive Data Relay Algorithm for Large Distributed Sensor Networks.

    Science.gov (United States)

    Xu, Yang; Hu, Xuemei; Hu, Haixiao; Liu, Ming

    2016-08-16

    In large-scale distributed sensor networks, sensed data is required to be relayed around the network so that one or few sensors can gather adequate relative data to produce high quality information for decision-making. In regards to very high energy-constraint sensor nodes, data transmission should be extremely economical. However, traditional data delivery protocols are potentially inefficient relaying unpredictable sensor readings for data fusion in large distributed networks for either overwhelming query transmissions or unnecessary data coverage. By building sensors' local model from their previously transmitted data in three matrixes, we have developed a novel energy-saving data relay algorithm, which allows sensors to proactively make broadcast decisions by using a neat matrix computation to provide balance between transmission and energy-saving. In addition, we designed a heuristic maintenance algorithm to efficiently update these three matrices. This can easily be deployed to large-scale mobile networks in which decisions of sensors are based on their local matrix models no matter how large the network is, and the local models of these sensors are updated constantly. Compared with some traditional approaches based on our simulations, the efficiency of this approach is manifested in uncertain environment. The results show that our approach is scalable and can effectively balance aggregating data with minimizing energy consumption.

  16. A Matrix-Based Proactive Data Relay Algorithm for Large Distributed Sensor Networks.

    Science.gov (United States)

    Xu, Yang; Hu, Xuemei; Hu, Haixiao; Liu, Ming

    2016-01-01

    In large-scale distributed sensor networks, sensed data is required to be relayed around the network so that one or few sensors can gather adequate relative data to produce high quality information for decision-making. In regards to very high energy-constraint sensor nodes, data transmission should be extremely economical. However, traditional data delivery protocols are potentially inefficient relaying unpredictable sensor readings for data fusion in large distributed networks for either overwhelming query transmissions or unnecessary data coverage. By building sensors' local model from their previously transmitted data in three matrixes, we have developed a novel energy-saving data relay algorithm, which allows sensors to proactively make broadcast decisions by using a neat matrix computation to provide balance between transmission and energy-saving. In addition, we designed a heuristic maintenance algorithm to efficiently update these three matrices. This can easily be deployed to large-scale mobile networks in which decisions of sensors are based on their local matrix models no matter how large the network is, and the local models of these sensors are updated constantly. Compared with some traditional approaches based on our simulations, the efficiency of this approach is manifested in uncertain environment. The results show that our approach is scalable and can effectively balance aggregating data with minimizing energy consumption. PMID:27537891

  17. A Matrix-Based Proactive Data Relay Algorithm for Large Distributed Sensor Networks

    Science.gov (United States)

    Xu, Yang; Hu, Xuemei; Hu, Haixiao; Liu, Ming

    2016-01-01

    In large-scale distributed sensor networks, sensed data is required to be relayed around the network so that one or few sensors can gather adequate relative data to produce high quality information for decision-making. In regards to very high energy-constraint sensor nodes, data transmission should be extremely economical. However, traditional data delivery protocols are potentially inefficient relaying unpredictable sensor readings for data fusion in large distributed networks for either overwhelming query transmissions or unnecessary data coverage. By building sensors’ local model from their previously transmitted data in three matrixes, we have developed a novel energy-saving data relay algorithm, which allows sensors to proactively make broadcast decisions by using a neat matrix computation to provide balance between transmission and energy-saving. In addition, we designed a heuristic maintenance algorithm to efficiently update these three matrices. This can easily be deployed to large-scale mobile networks in which decisions of sensors are based on their local matrix models no matter how large the network is, and the local models of these sensors are updated constantly. Compared with some traditional approaches based on our simulations, the efficiency of this approach is manifested in uncertain environment. The results show that our approach is scalable and can effectively balance aggregating data with minimizing energy consumption. PMID:27537891

  18. Network Formation Games Among Relay Stations in Next Generation Wireless Networks

    CERN Document Server

    Saad, Walid; Başar, Tamer; Debbah, Mérouane; Hjørungnes, Are

    2012-01-01

    The introduction of relay station (RS) nodes is a key feature in next generation wireless networks such as 3GPP's long term evolution advanced (LTE-Advanced), or the forthcoming IEEE 802.16j WiMAX standard. This paper presents, using game theory, a novel approach for the formation of the tree architecture that connects the RSs and their serving base station in the \\emph{uplink} of the next generation wireless multi-hop systems. Unlike existing literature which mainly focused on performance analysis, we propose a distributed algorithm for studying the \\emph{structure} and \\emph{dynamics} of the network. We formulate a network formation game among the RSs whereby each RS aims to maximize a cross-layer utility function that takes into account the benefit from cooperative transmission, in terms of reduced bit error rate, and the costs in terms of the delay due to multi-hop transmission. For forming the tree structure, a distributed myopic algorithm is devised. Using the proposed algorithm, each RS can individuall...

  19. Towards increasing diversity for the relaying of LT Fountain Codes in Wireless Sensor Networks

    CERN Document Server

    Anya, Apavatjrut; Jaffrès-Runser, Katia; Comaniciu, Cristina; Gorce, Jean-Marie

    2010-01-01

    Diversity is a powerful means to increase the transmission performance of wireless communications. For the case of fountain codes relaying, it has been shown previously that introducing diversity is also beneficial since it counteracts transmission losses on the channel. Instead of simply hop-by-hop forwarding information, each sensor node diversifies the information flow using XOR combinations of stored packets. This approach has been shown to be efficient for random linear fountain codes. However, random linear codes exhibit high decoding complexity. In this paper, we propose diversity increased relaying strategies for the more realistic Luby Transform code in order to maintain high transmission performance with low decoding computational complexity in a linear network. Results are provided herein for a linear network assuming uniform imperfect channel states.

  20. Indirect Channel Sensing for Cognitive Amplify-and-Forward Relay Networks

    CERN Document Server

    Liu, Yipeng

    2011-01-01

    In cognitive radio network the primary channel information is beneficial. But it can not be obtained by direct channel estimation in cognitive system as pervious methods. And only one possible way is the primary receiver broadcasts the primary channel information to the cognitive users, but it would require the modification of the primary receiver and additional precious spectrum resource. Cooperative communication is also a promising technique. And this paper introduces an indirect channel sensing method for the primary channel in cognitive amplify-and-forward (AF) relay network. As the signal retransmitted from the primary AF relay node includes channel effects, the cognitive radio can receive retransmitted signal from AF node, and then extract the channel information from them. Afterwards, Least squares channel estimation and sparse channel estimation can be used to address the dense and sparse multipath channels respectively. Numerical experiment demonstrates that the proposed indirect channel sensing met...

  1. Power Allocation for Balancing Spectrum Efficiency and Power Consumption in Cognitive Relay Networks

    Directory of Open Access Journals (Sweden)

    Lun Tang

    2011-10-01

    Full Text Available In order to guarantee the QoS requirement of secondary users and not to affect the outage probability of primary user in cognitive relay networks, we propose two optimal power allocation models: (1 maximizing the transmission rate of secondary users; (2 minimizing the total power consumption. Theory analysis shows that two optimal power allocation models conflict between spectrum efficiency and power consumption. Furthermore, an optimal power allocation model which joints the transmission rate and the total power consumption in cognitive relay networks is proposed. By using the Lagrangian method, the optimization algorithm for this model is designed. The proposed algorithm can achieve the trade-off between the transmission rate and the total power consumption by varying the weight. Simulation results show that the proposed algorithm can effectively adjust the transmission rate and the total power consumption of secondary users.

  2. The Performance of Relay-Enhanced Cellular OFDMA-TDD Network for Mobile Broadband Wireless Services

    Directory of Open Access Journals (Sweden)

    Kyungmi Park

    2009-01-01

    Full Text Available A multihop relay (MR and repeater are useful means for improving system throughput and coverage in a cellular mobile packet access system, as the carrier-to-interference ratio can be improved when deploying them in a heavily shadowed region. In this paper, we report on our investigation of bandwidth efficiency and the associated service outage performance for different relay scenarios, using system level simulation for a cellular Orthogonal Frequency Division Multiple Access-Time Division Duplexing (OFDMA-TDD system. We have demonstrated that network throughput gain by typical optical repeaters, which have a simple amplify-and-forwarding capability in a full-duplexing mode, could be minimal in open space subject to cochannel interference from all repeaters in the neighboring cells. This is true, even though they are generally useful for warranting the outage performance with a multiple order of combining gain, especially in the destructive area, for example, basements or indoors with heavy wall attenuation, that naturally shields interference. Meanwhile, we show that multihop relays increase the average system capacity (almost doubling the system throughput by fully reusing the frequency in every relay station, while improving the per-user data rate in the cell edges or improving the outage performance in the heavily shadowed areas.

  3. Applying Hybrid PSO to Optimize Directional Overcurrent Relay Coordination in Variable Network Topologies

    OpenAIRE

    Ming-Ta Yang; An Liu

    2013-01-01

    In power systems, determining the values of time dial setting (TDS) and the plug setting (PS) for directional overcurrent relays (DOCRs) is an extremely constrained optimization problem that has been previously described and solved as a nonlinear programming problem. Optimization coordination problems of near-end faults and far-end faults occurring simultaneously in circuits with various topologies, including fixed and variable network topologies, are considered in this study. The aim of thi...

  4. Device-Relaying in Cellular D2D Networks: A Fairness Perspective

    KAUST Repository

    Chaaban, Anas

    2015-10-24

    Device-to-Device (D2D) communication is envisioned to play a key role in 5G networks as a technique for meeting the demand for high data rates. In a cellular network, D2D allows not only direct communication between users, but also device relaying. In this paper, a simple instance of device-relaying is investigated, and its impact on fairness among users is studied. Namely, a cellular network consisting of two D2D-enabled users and a base-station (BS) is considered. Thus, the users who want to establish communication with the BS can act as relays for each other’s signals. While this problem is traditionally considered in the literature as a multiple-access channel with cooperation in the uplink, and a broadcast channel with cooperation in the downlink, we propose a different treatment of the problem as a multi-way channel. A simple communication scheme is proposed, and is shown to achieve significant gain in terms of fairness (measured by the symmetric rate supported) in comparison to the aforementioned traditional treatment.

  5. 帧中继与ISDN网络%Frame Relay and ISDN network

    Institute of Scientific and Technical Information of China (English)

    林楠; 史苇杭

    2009-01-01

    The process of the network design, configuration and verification was mainly discussed. The Frame Relay link was used in a point-to-point partial mesh topology design between one main campus, Campus A and Campus B. In order to reduce the cost, the communications between others campuses was used the Hub and Spoke Frame Relay topology. The final result of the network test showed that the Frame Relay can provide a high performance network connection, and the ISDN can be active to achieve a backup function when the primary link fails. All functions work correctly.%研究了网络的设计、配置与实例联通验证.其中帧中继被用在点对点部分网状拓扑中,连接某大学主校园和其他两个分散校园A与B;为了降低成本,其他校园的连接使用了星型的帧中继拓扑结构.测试结果表明,帧中继可以提供高性能的网络连接,当连接失败时可使用ISDN作为辅助备份连接,网络运行通畅.

  6. Cross-Layer Design for Two-Way Relaying Networks with Multiple Antennas

    Directory of Open Access Journals (Sweden)

    zhuo wu

    2015-10-01

    Full Text Available In this paper, we developed a cross-layer design for two-way relaying (TWR networks with multiple antennas, where two single antenna source nodes exchange information with the aid of one multiple antenna relay node. The proposed cross-layer design considers adaptive modulation (AM and space-time block coding (STBC at the physical layer with an automatic repeat request (ARQ protocol at the data link layer, in order to maximize the spectral efficiency under specific delay and packet error ratio (PER constraints. An MMSE-interference cancellation (IC receiver is employed at the relay node, to remove the interference in the fist phase of the TWR transmission. The transmission mode is updated for each phase of the TWR transmission on a frame-by-frame basis, to match the time-varying channel conditions and exploit the system performance and throughput gain. Simulation results show that retransmission at the data link layer could alleviate rigorous error-control requirements at the physical layer, and thereby allows higher data transmission. As a result, cross-layer design helps to achieve considerable system spectral efficiency gain for TWR networks, compared to those without cross-layer design.

  7. Preamble-based channel estimation in single-relay networks using FBMC/OQAM

    Science.gov (United States)

    Mavrokefalidis, Christos; Kofidis, Eleftherios; Rontogiannis, Athanasios A.; Theodoridis, Sergios

    2014-12-01

    Preamble-based channel estimation in filter bank-based multicarrier (FBMC) systems using offset quadrature amplitude modulation (OQAM) has been extensively studied in the last few years, due to the many advantages this modulation scheme can offer over cyclic prefix (CP)-based orthogonal frequency division multiplexing (OFDM) and in view of the interesting challenges posed on the channel estimator by the interference effect inherent in such an FBMC system. In particular, preambles of short duration and of both the block ( full) and comb ( sparse) types were designed so as to minimize the channel estimation mean squared error (MSE) subject to a given transmit energy. In the light of the important role that relay-based cooperative networks are expected to play in future wireless communication systems, it is of interest to consider FBMC/OQAM, and in particular questions associated to preamble-based channel estimation, in such a context as well. The goal of this paper is to address these problems and come up with optimal solutions that extend existing results in a single relay-based cooperative network. Both low and medium frequency selective channels are considered. In addition to optimal preamble and estimator design, the equalization/detection task is studied, shedding light to a relay-generated interference effect and proposing a simple way to come over it. The reported simulation results corroborate the analysis and reveal interesting behavior with respect to channel frequency selectivity and signal-to-noise ratio.

  8. Joint subchannel pairing and power control for cognitive radio networks with amplify-and-forward relaying.

    Science.gov (United States)

    Shen, Yanyan; Wang, Shuqiang; Wei, Zhiming

    2014-01-01

    Dynamic spectrum sharing has drawn intensive attention in cognitive radio networks. The secondary users are allowed to use the available spectrum to transmit data if the interference to the primary users is maintained at a low level. Cooperative transmission for secondary users can reduce the transmission power and thus improve the performance further. We study the joint subchannel pairing and power allocation problem in relay-based cognitive radio networks. The objective is to maximize the sum rate of the secondary user that is helped by an amplify-and-forward relay. The individual power constraints at the source and the relay, the subchannel pairing constraints, and the interference power constraints are considered. The problem under consideration is formulated as a mixed integer programming problem. By the dual decomposition method, a joint optimal subchannel pairing and power allocation algorithm is proposed. To reduce the computational complexity, two suboptimal algorithms are developed. Simulations have been conducted to verify the performance of the proposed algorithms in terms of sum rate and average running time under different conditions. PMID:25045731

  9. A novel resource optimization scheme for multi-cell OFDMA relay network

    Institute of Scientific and Technical Information of China (English)

    Ning DU; Fa-sheng LIU

    2016-01-01

    In cellular networks, users communicate with each other through their respective base stations (BSs). Conventionally, users are assumed to be in different cells. BSs serve as decode-and-forward (DF) relay nodes to users. In addition to this type of conventional user, we recognize that there are scenarios users who want to communicate with each other are located in the same cell. This gives rise to the scenario of intra-cell communication. In this case, a BS can behave as a two-way relay to achieve information exchange instead of using conventional DF relay. We consider a multi-cell orthogonal frequency division multiple access (OFDMA) network that comprises these two types of users. We are interested in resource allocation between them. Specifi cally, we jointly optimize subcarrier assignment, subcarrier pairing, and power allocation to maximize the weighted sum rate. We consider the resource allocation problem at BSs when the end users’ power is fi xed. We solve the problem approximately through Lagrange dual decomposition. Simulation results show that the proposed schemes outperform other existing schemes.

  10. Robust distributed two-way relay beamforming in cognitive radio networks

    KAUST Repository

    Pandarakkottilil, Ubaidulla

    2012-04-01

    In this paper, we present distributed beamformer designs for a cognitive radio network (CRN) consisting of a pair of cognitive (or secondary) transceiver nodes communicating with each other through a set of secondary non-regenerative two-way relays. The secondary network shares the spectrum with a licensed primary user (PU), and operates under a constraint on the maximum interference to the PU, in addition to its own resource and quality of service (QoS) constraints. We propose beamformer designs assuming that the available channel state information (CSI) is imperfect, which reflects realistic scenarios. The performance of proposed designs is robust to the CSI errors. Such robustness is critical in CRNs given the difficulty in acquiring perfect CSI due to loose cooperation between the PUs and the secondary users (SUs), and the need for strict enforcement of PU interference limit. We consider a mean-square error (MSE)-constrained beamformer that minimizes the total relay transmit power and an MSE-balancing beamformer with a constraint on the total relay transmit power. We show that the proposed designs can be reformulated as convex optimization problems that can be solved efficiently. Through numerical simulations, we illustrate the improved performance of the proposed robust designs compared to non-robust designs. © 2012 IEEE.

  11. Cooperative beamforming for dual-hop amplify-and-forward multi-antenna relaying cellular networks

    KAUST Repository

    Xing, Chengwen

    2012-11-01

    In this paper, linear beamforming design for amplify-and-forward relaying cellular networks is considered, in which base station, relay station and mobile terminals are all equipped with multiple antennas. The design is based on minimum mean-square-error criterion, and both uplink and downlink scenarios are considered. It is found that the downlink and uplink beamforming design problems are in the same form, and iterative algorithms with the same structure can be used to solve the design problems. For the specific cases of fully loaded or overloaded uplink systems, a novel algorithm is derived and its relationships with several existing beamforming design algorithms for conventional MIMO or multiuser systems are revealed. Simulation results are presented to demonstrate the performance advantage of the proposed design algorithms. © 2012 Published by Elsevier B.V. All rights reserved.

  12. Throughput Improvement and Its Tradeoff with The Queuing Delay in the Diamond Relay Networks

    CERN Document Server

    Wang, Qing; Letaief, Khaled Ben

    2009-01-01

    Diamond relay channel model, as a basic transmission model, has recently been attracting considerable attention in wireless Ad Hoc networks. Node cooperation and opportunistic scheduling scheme are two important techniques to improve the performance in wireless scenarios. In the paper we consider such a problem how to efficiently combine opportunistic scheduling and cooperative modes in the Rayleigh fading scenarios. To do so, we first compare the throughput of SRP (Spatial Reused Pattern) and AFP (Amplify Forwarding Pattern) in the half-duplex case with the assumption that channel side information is known to all and then come up with a new scheduling scheme. It will that that only switching between SRP and AFP simply does little help to obtain an expected improvement because SRP is always superior to AFP on average due to its efficient spatial reuse. To improve the throughput further, we put forward a new processing strategy in which buffers are employed at both relays in SRP mode. By efficiently utilizing ...

  13. Joint Adaptive Modulation-Coding and Cooperative ARQ for Wireless Relay Networks

    CERN Document Server

    Mardani, Morteza; Lahouti, Farshad; Eliasi, Behrouz

    2008-01-01

    This paper presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and cooperative truncated automatic repeat request (ARQ) protocol at the data link layer. We first derive an exact closed form expression for the spectral efficiency of the proposed joint AMC-cooperative ARQ scheme. Aiming at maximizing this system performance measure, we then optimize an AMC scheme which directly satisfies a prescribed packet loss rate constraint at the data-link layer. The results indicate that utilizing cooperative ARQ as a retransmission strategy, noticeably enhances the spectral efficiency compared with the system that employs AMC alone at the physical layer. Moreover, the proposed adaptive rate cooperative ARQ scheme outperforms the fixed rate counterpart when the transmission modes at the source and relay are chosen based on the channel statistics. This in turn quantifies the possible gain achieved by joint design of AMC and ARQ in wireless relay networks.

  14. Relay movement control for maintaining connectivity in aeronautical ad hoc networks

    Institute of Scientific and Technical Information of China (English)

    李杰; 孙志强; 师博浩; 宫二玲; 谢红卫

    2016-01-01

    As a new sort of mobile ad hoc network (MANET), aeronautical ad hoc network (AANET) has fleet-moving airborne nodes (ANs) and suffers from frequent network partitioning due to the rapid-changing topology. In this work, the additional relay nodes (RNs) is employed to repair the network and maintain connectivity in AANET. As ANs move, RNs need to move as well in order to re-establish the topology as quickly as possible. The network model and problem definition are firstly given, and then an online approach for RNs’ movement control is presented to make ANs achieve certain connectivity requirement during run time. By defining the minimum cost feasible moving matrix (MCFM), a fast algorithm is proposed for RNs’ movement control problem. Simulations demonstrate that the proposed algorithm outperforms other control approaches in the highly-dynamic environment and is of great potential to be applied in AANET.

  15. Properties and Stability of Max-Product Fuzzy Bi-Directional Associative Memory

    Institute of Scientific and Technical Information of China (English)

    SHU Lan

    2005-01-01

    In this paper, a fuzzy operator of max-product is defined at first, and the fuzzy bi-directional associative memory (FBAM) based on the fuzzy operator of max-product is given. Then the properties and the Lyapunov stability of equilibriums of the networks are studied.

  16. Inferring bi-directional interactions between circadian clock genes and metabolism with model ensembles

    NARCIS (Netherlands)

    Grzegorczyk, Marco; Aderhold, Andrej; Husmeier, Dirk

    2015-01-01

    There has been much interest in reconstructing bi-directional regulatory networks linking the circadian clock to metabolism in plants. A variety of reverse engineering methods from machine learning and computational statistics have been proposed and evaluated. The emphasis of the present paper is on

  17. Optimal Beamforming for Two-Way Multi-Antenna Relay Channel with Analogue Network Coding

    CERN Document Server

    Zhang, Rui; Chai, Chin Choy

    2008-01-01

    This paper is concerned with the wireless two-way relay channel (TWRC), where two source nodes S1 and S2 exchange their information through an assisting relay node R. It is assumed that R receives the signal from S1 and S2 concurrently in one time-slot, and then amplifies the received signal and broadcasts it to both S1 and S2 in a second time-slot. By applying the principle of analogue network coding (ANC), each one of S1 and S2 first cancels the so-called "self-interference" in the received signal from R and then decodes the other's message. Assuming that S1 and S2 are equipped with single antenna each and R with multiple antennas, this paper studies the optimal design of linear processing (beamforming) at R to achieve the capacity region of TWRC with ANC. The capacity region constitutes all the achievable bidirectional rate-pairs of S1 and S2 under given transmit power constraints at S1, S2, and R. We present the optimal relay beamforming structure as well as efficient algorithms to compute the optimal bea...

  18. Mobile Ad-Hoc Network Based Relaying Data System for Oceanic Flight Routes in Aeronautical Communications

    Directory of Open Access Journals (Sweden)

    Ho Dac Tu

    2009-04-01

    Full Text Available This paper proposes a reliable system to overcome the weakness of current the HF radio communicationsystem for oceanic aeronautical flight routes. This system uses only one aeronautical VHF channel with air-toairradio relay system based on local mobile Ad-hoc networks. For access to/from all aircrafts in the system, aTDMA (Time Division Multiple Access scheme is proposed to be used where each aircraft is assigned onetime slot during its presence in the system in order to transmit its own packet by itself or relay them usingneighbouring aircrafts. These packets contain aircraft position, ID, relative direction which are used to build arouting table at each aircraft. In addition, several algorithms for relaying packets; schemes to reduce thepacket-loss-ratio as well as to reduce the interference caused by surrounding aircrafts have been proposed.The simulations have shown the improvement of such proposals when examining system performance underreal air-traffic scenarios. This system strengthens the reliability of oceanic aeronautical communication andincreases situational awareness of all oceanic flights as an effective solution to operate more flights on theocean but in higher safety.

  19. Relay-based routing protocol for space networks with predictable mobility

    Science.gov (United States)

    Zhang, Zhi; Dai, Guanzhong; Li, Lixin; Zhao, Yuting

    2005-11-01

    Future space scientific missions are envisioned to incorporate a large number of satellites and spacecrafts deployed in different orbits to network together into Space Networks. These networks have some unique characteristics such as limited resource of nodes, large latency and intermittent connectivity, which pose challenges to routing. In this paper, we propose a Relay-based Routing Protocol for Space Networks (RRPSN), which exploits the predictability of nodes motion to help deliver packets. Nodes use the link state and trajectory information received from other nodes to construct the routing tables where the next hop node is selected from the current as well as the future neighbors. Three key components of the protocol, including dissemination link information, modified Dijkstra's algorithm and packet processing are described in this paper. The computation complexity and overhead of the protocol is analyzed.

  20. Japan Data Exchange Network JDXnet and Cloud-type Data Relay Server for Earthquake Observation Data

    Science.gov (United States)

    Takano, K.; Urabe, T.; Tsuruoka, H.; Nakagawa, S.

    2015-12-01

    In Japan, high-sensitive seismic observation and broad-band seismic observation are carried out by several organization such as Japan Meteorological Agency (JMA) , National Research Institute for Earth Science and Disaster Prevention (NIED), nine National Universities, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) , etc. The total number of the observation station is about 1400 points. The total volume of the seismic waveform data collected from all these observation station is about 1MByte for 1 second (about 8 to 10Mbps) by using the WIN system(Urabe 1991). JDXnet is the Japan Data eXchange network for earthquake observation data. JDXnet was started from 2007 by cooperation of the researchers of each organization. All the seismic waveform data are available at the all organizations in real-time. The core of JDXnet is the broadcast type real-time data exchange by using the nationwide L2-VPN service offered in JGN-X of NICT and SINET4 of NII. Before the Tohoku earthquake, the nine national universities had collected seismic data to each data center and then exchanged with other universities and institutions by JDXnet. However, in this case, if the center of the university was stopped, all data of the university could not use even though there are some alive observation stations. Because of this problem, we have prepared the data relay server in the data center of SINET4 ie the cloud center. This data relay server collects data directly from the observation stations of the universities and delivers data to all universities and institutions by JDXnet. By using the relay server on cloud center, even if some universities are affected by a large disaster, it is eliminated that the data of the living station is lost. If the researchers set up seismometers and send data to the relay server, then data are available to all researchers. This mechanism promotes the joint use of the seismometers and joint research activities in nationwide researchers.

  1. Optimal transmit power allocation for MIMO two-way cognitive relay networks with multiple relays using AF strategy

    KAUST Repository

    Alsharoa, Ahmad M.

    2014-02-01

    In this letter, we consider a multiple-input multiple-output two-way cognitive radio system under a spectrum sharing scenario, where primary and secondary users operate on the same frequency band. The secondary terminals aims to exchange different messages with each other using multiple relays where each relay employs an amplify-and-forward strategy. The main objective of our work is to maximize the secondary sum rate allowed to share the spectrum with the primary users by respecting a primary user tolerated interference threshold. In this context, we derive an analytical expression of the optimal power allocated to each antenna of the terminals. We then discuss the impact of some system parameters on the performance in the numerical result section. © 2012 IEEE.

  2. Lossy Broadcasting in Two-Way Relay Networks with Common Reconstructions

    CERN Document Server

    Timo, Roy; Kramer, Gerhard

    2010-01-01

    The broadcast phase (downlink transmission) of the two-way relay network is studied in the source coding and joint source-channel coding settings. The rates needed for reliable communication are characterised for a number of special cases including: small distortions, deterministic distortion measures, and jointly Gaussian sources with quadratic distortion measures. The broadcast problem is also studied with common-reconstruction decoding constraints, and the rates needed for reliable communication are characterised for all discrete memoryless sources and per-letter distortion measures.

  3. Impact of Channel Partitioning and Relay Placement on Resource Allocation in OFDMA Cellular Networks

    Directory of Open Access Journals (Sweden)

    Sultan F. Meko

    2012-07-01

    Full Text Available Tremendous growth in the demand for wireless applications such as streaming audio/videos, Skype and video games require high data rate irrespective of user’s location in the cellular network. However, the Quality of Service (QoS of users degrades at the cell boundary. Relay enhanced multi-hop cellular network is one of the cost effective solution to improve the performance of cell edge users. Optimal deployment of Fixed Relay Nodes (FRNs is essential to satisfy the QoS requirement of edge users. We propose new schemes for channel partitioning and FRN placement in cellular networks. Path-loss, Signal to Interference and Noise Ratio (SINR experienced by users, and effects of shadowing have been considered. The analysis gives more emphasis on the cell-edge users (worst case scenario. The results show that these schemes achieve higher system performance in terms of spectral efficiency and also increase the user data rate at the cell edge.

  4. Enabling Adaptive Rate and Relay Selection for 802.11 Mobile Ad Hoc Networks

    CERN Document Server

    Mehta, Neil; Wang, Wenye

    2011-01-01

    Mobile ad hoc networks (MANETs) are self-configuring wireless networks that lack permanent infrastructure and are formed among mobile nodes on demand. Rapid node mobility results in dramatic channel variation, or fading, that degrades MANET performance. Employing channel state information (CSI) at the transmitter can improve the throughput of routing and medium access control (MAC) protocols for mobile ad hoc networks. Several routing algorithms in the literature explicitly incorporate the fading signal strength into the routing metric, thus selecting the routes with strong channel conditions. While these studies show that adaptation to the time-variant channel gain is beneficial in MANETs, they do not address the effect of the outdated fading CSI at the transmitter. For realistic mobile node speeds, the channel gain is rapidly varying, and becomes quickly outdated due the feedback delay. We analyze the link throughput of joint rate adaptation and adaptive relay selection in the presence of imperfect CSI. Mor...

  5. Capacity Enhancement in 60 GHz Based D2D Networks by Relay Selection and Scheduling

    Directory of Open Access Journals (Sweden)

    Waheed ur Rehman

    2015-01-01

    Full Text Available Millimeter-wave or 60 GHz communication is a promising technology that enables data rates in multigigabits. However, its tremendous propagation loss and signal blockage may severely affect the network throughput. In current data-centric device-to-device (D2D communication networks, the devices with intended data communications usually lay in close proximity, unlike the case in voice-centric networks. So the network can be visualized as a naturally formed groups of devices. In this paper, we jointly consider resource scheduling and relay selection to improve network capacity in 60 GHz based D2D networks. Two types of transmission scenarios are considered in wireless personal area networks (WPANs, intra and intergroup. A distributed receiver based relay selection scheme is proposed for intragroup transmission, while a distance based relay selection scheme is proposed for intergroup transmission. The outage analysis of our proposed relay selection scheme is provided along with the numerical results. We then propose a concurrent transmission scheduling algorithm based on vertex coloring technique. The proposed scheduling algorithm employs time and space division in mmWave WPANs. Using vertex multicoloring, we allow transmitter-receiver (Tx-Rx communication pairs to span over more colors, enabling better time slot utilization. We evaluate our scheduling algorithm in single-hop and multihop scenarios and discover that it outperforms other schemes by significantly improving network throughput.

  6. Theoretical study of network design methodologies for the aerial relay system. [energy consumption and air traffic control

    Science.gov (United States)

    Rivera, J. M.; Simpson, R. W.

    1980-01-01

    The aerial relay system network design problem is discussed. A generalized branch and bound based algorithm is developed which can consider a variety of optimization criteria, such as minimum passenger travel time and minimum liner and feeder operating costs. The algorithm, although efficient, is basically useful for small size networks, due to its nature of exponentially increasing computation time with the number of variables.

  7. Time and Energy Efficient Relay Transmission for Multi-Hop Wireless Sensor Networks.

    Science.gov (United States)

    Kim, Jin-Woo; Barrado, José Ramón Ramos; Jeon, Dong-Keun

    2016-01-01

    The IEEE 802.15.4 standard is widely recognized as one of the most successful enabling technologies for short range low rate wireless communications and it is used in IoT applications. It covers all the details related to the MAC and PHY layers of the IoT protocol stack. Due to the nature of IoT, the wireless sensor networks are autonomously self-organized networks without infrastructure support. One of the issues in IoT is the network scalability. To address this issue, it is necessary to support the multi-hop topology. The IEEE 802.15.4 network can support a star, peer-to-peer, or cluster-tree topology. One of the IEEE 802.15.4 topologies suited for the high predictability of performance guarantees and energy efficient behavior is a cluster-tree topology where sensor nodes can switch off their transceivers and go into a sleep state to save energy. However, the IEEE 802.15.4 cluster-tree topology may not be able to provide sufficient bandwidth for the increased traffic load and the additional information may not be delivered successfully. The common drawback of the existing approaches is that they do not address the poor bandwidth utilization problem in IEEE 802.15.4 cluster-tree networks, so it is difficult to increase the network performance. Therefore, to solve this problem in this paper we study a relay transmission protocol based on the standard protocol in the IEEE 802.15.4 MAC. In the proposed scheme, the coordinators can relay data frames to their parent devices or their children devices without contention and can provide bandwidth for the increased traffic load or the number of devices. We also evaluate the performance of the proposed scheme through simulation. The simulation results demonstrate that the proposed scheme can improve the reliability, the end-to-end delay, and the energy consumption. PMID:27355952

  8. Time and Energy Efficient Relay Transmission for Multi-Hop Wireless Sensor Networks

    Science.gov (United States)

    Kim, Jin-Woo; Barrado, José Ramón Ramos; Jeon, Dong-Keun

    2016-01-01

    The IEEE 802.15.4 standard is widely recognized as one of the most successful enabling technologies for short range low rate wireless communications and it is used in IoT applications. It covers all the details related to the MAC and PHY layers of the IoT protocol stack. Due to the nature of IoT, the wireless sensor networks are autonomously self-organized networks without infrastructure support. One of the issues in IoT is the network scalability. To address this issue, it is necessary to support the multi-hop topology. The IEEE 802.15.4 network can support a star, peer-to-peer, or cluster-tree topology. One of the IEEE 802.15.4 topologies suited for the high predictability of performance guarantees and energy efficient behavior is a cluster-tree topology where sensor nodes can switch off their transceivers and go into a sleep state to save energy. However, the IEEE 802.15.4 cluster-tree topology may not be able to provide sufficient bandwidth for the increased traffic load and the additional information may not be delivered successfully. The common drawback of the existing approaches is that they do not address the poor bandwidth utilization problem in IEEE 802.15.4 cluster-tree networks, so it is difficult to increase the network performance. Therefore, to solve this problem in this paper we study a relay transmission protocol based on the standard protocol in the IEEE 802.15.4 MAC. In the proposed scheme, the coordinators can relay data frames to their parent devices or their children devices without contention and can provide bandwidth for the increased traffic load or the number of devices. We also evaluate the performance of the proposed scheme through simulation. The simulation results demonstrate that the proposed scheme can improve the reliability, the end-to-end delay, and the energy consumption. PMID:27355952

  9. Time and Energy Efficient Relay Transmission for Multi-Hop Wireless Sensor Networks.

    Science.gov (United States)

    Kim, Jin-Woo; Barrado, José Ramón Ramos; Jeon, Dong-Keun

    2016-06-27

    The IEEE 802.15.4 standard is widely recognized as one of the most successful enabling technologies for short range low rate wireless communications and it is used in IoT applications. It covers all the details related to the MAC and PHY layers of the IoT protocol stack. Due to the nature of IoT, the wireless sensor networks are autonomously self-organized networks without infrastructure support. One of the issues in IoT is the network scalability. To address this issue, it is necessary to support the multi-hop topology. The IEEE 802.15.4 network can support a star, peer-to-peer, or cluster-tree topology. One of the IEEE 802.15.4 topologies suited for the high predictability of performance guarantees and energy efficient behavior is a cluster-tree topology where sensor nodes can switch off their transceivers and go into a sleep state to save energy. However, the IEEE 802.15.4 cluster-tree topology may not be able to provide sufficient bandwidth for the increased traffic load and the additional information may not be delivered successfully. The common drawback of the existing approaches is that they do not address the poor bandwidth utilization problem in IEEE 802.15.4 cluster-tree networks, so it is difficult to increase the network performance. Therefore, to solve this problem in this paper we study a relay transmission protocol based on the standard protocol in the IEEE 802.15.4 MAC. In the proposed scheme, the coordinators can relay data frames to their parent devices or their children devices without contention and can provide bandwidth for the increased traffic load or the number of devices. We also evaluate the performance of the proposed scheme through simulation. The simulation results demonstrate that the proposed scheme can improve the reliability, the end-to-end delay, and the energy consumption.

  10. PERFORMANCE ANALYSIS OF ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING BASED BIDIRECTIONAL RELAY NETWORK IN THE PRESENCE OF PHASE NOISE

    Directory of Open Access Journals (Sweden)

    V. N. Senthil Kumaran

    2013-01-01

    Full Text Available In this study, the performance of OFDM based bidirectional relay network which employs Physical Layer Network Coding (PLNC is analyzed in the presence of phase noise. The bidirectional relay network is assumed to consist of two sources and a relay, where each node has a single antenna and operates in half duplex mode. The PLNC based OFDM system transmits high data streams over numerous sub channels in frequency domain. Each sub channel is a narrow band flat fading channel, thereby achieving high spectral efficiency over wide band channels. In practice, phase noise is introduced with the information symbols transmitted on all subcarriers in OFDM transceiver. The influence of phase noise on the received signals are analyzed at both the Multiple Access Channel (MAC and at the Broadcast Channel (BC environments.

  11. Low-complexity full-rate transmission scheme with full diversity for two-path relay networks

    KAUST Repository

    Fareed, Muhammad Mehboob

    2015-04-01

    Existing full-rate transmission schemes for two-path relay networks typically cannot achieve full diversity while demanding high decoding complexity. In this paper, we present a novel low-complexity full-rate transmission scheme for two-path relay networks to harvest maximum achievable diversity. The proposed scheme adopts block transmission with small block size of four symbols, which greatly reduces the decoding complexity at the receiver. Through the performance analysis of the resulting two-path relay network in terms of the symbol error rate (SER) and diversity order, we show the proposed scheme can achieve full diversity order of four and mimic a 2 \\\\times 2 multiple-input multiple-output system. Simulations results are provided to validate the mathematical formulation. © 1967-2012 IEEE.

  12. Inferring bi-directional interactions between circadian clock genes and metabolism with model ensembles

    OpenAIRE

    Grzegorczyk, Marco; Aderhold, Andrej; Husmeier, Dirk

    2015-01-01

    There has been much interest in reconstructing bi-directional regulatory networks linking the circadian clock to metabolism in plants. A variety of reverse engineering methods from machine learning and computational statistics have been proposed and evaluated. The emphasis of the present paper is on combining models in a model ensemble to boost the network reconstruction accuracy, and to explore various model combination strategies to maximize the improvement. Our results demonstrate that a r...

  13. Node Deployment and the Impact of Relay Nodes in Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    Rudranath Mitra

    2012-06-01

    Full Text Available Node deployment is a fundamental issue to be solved in wireless sensor network. A proper node deployment can reduce the complexity of problems in WSN as for eg, routing, data fusion, communication etc. Different node deployment models have been proposed to reduce the complexity. In this paper we will discuss about the three models- Tri-hexagon-tiling (THT, Uniform Random and Square Grid. The nature of deployment of sensor nodes depend on the type of sensors, application and the environment where the networks will operate. Deployment of sensor nodes can be random or pre-determined. In random deployment nodes are deployed in a random manner. In pre-determined deployment, location of the nodes are specified. Most commonly used cell structure is Regular Hexagonal Cell Architecture. Here we will discuss the concept of relay nodes and its impact in sensor nodes

  14. TDMA Achieves the Optimal Diversity Gain in Relay-Assisted Cellular Networks

    CERN Document Server

    Bi, Suzhi; Zhang,

    2011-01-01

    In multi-access wireless networks, transmission scheduling is a key component that determines the efficiency and fairness of wireless spectrum allocation. At one extreme, greedy opportunistic scheduling that allocates airtime to the user with the largest instantaneous channel gain achieves the optimal spectrum efficiency and transmission reliability but the poorest user-level fairness. At the other extreme, fixed TDMA scheduling achieves the fairest airtime allocation but the lowest spectrum efficiency and transmission reliability. To balance the two competing objectives, extensive research efforts have been spent on designing opportunistic scheduling schemes that reach certain tradeoff points between the two extremes. In this paper and in contrast to the conventional wisdom, we find that in relay-assisted cellular networks, fixed TDMA achieves the same optimal diversity gain as greedy opportunistic scheduling. In addition, by incorporating very limited opportunism, a simple relaxed-TDMA scheme asymptotically...

  15. Performance Analysis of Secondary Link with Cross-Layer Design and Cooperative Relay in Cognitive Radio Networks

    KAUST Repository

    Ma, Hao

    2012-06-01

    In this thesis, we investigate two different system infrastructures in underlay cognitive radio network, in which two popular techniques, cross-layer design and cooperative communication, are considered, respectively. In particular, we introduce the Aggressive Adaptive Modulation and Coding (A-AMC) into the cross-layer design and achieve the optimal boundary points in closed form to choose the AMC and A-AMC transmission modes by taking into account the Channel State Information (CSI) from the secondary transmitter to both the primary receiver and the secondary receiver. What’s more, for the cooperative communication design, we consider three different relay selection schemes: Partial Relay Selection, Opportunistic Relay Selection and Threshold Relay Selection. The Probability Density Functions (PDFs) of the Signal-to- Noise Ratio (SNR) in each hop for different selection schemes are provided, and then the exact closed-form expressions for the end-to-end packet loss rate in the secondary link considering the cooperation of the Decode-and-Forward (DF) relay for different relay selection schemes are derived.

  16. Recoverable DTN Routing based on a Relay of Cyclic Message-Ferries on a MSQ Network

    CERN Document Server

    Hayashi, Yukio

    2015-01-01

    An interrelation between a topological design of network and efficient algorithm on it is important for its applications to communication or transportation systems. In this paper, we propose a design principle for a reliable routing in a store-carry-forward manner based on autonomously moving message-ferries on a special structure of fractal-like network, which consists of a self-similar tiling of equilateral triangles. As a collective adaptive mechanism, the routing is realized by a relay of cyclic message-ferries corresponded to a concatenation of the triangle cycles and using some good properties of the network structure. It is recoverable for local accidents in the hierarchical network structure. Moreover, the design principle is theoretically supported with a calculation method for the optimal service rates of message-ferries derived from a tandem queue model for stochastic processes on a chain of edges in the network. These results obtained from a combination of complex network science and computer scie...

  17. Ground wave emergency network environmental assessment for northwestern Colorado relay node site number RN 8C924CO

    Science.gov (United States)

    1993-02-01

    The Ground Wave Emergency Network (GWEN) is a radio communication system designed to relay emergency messages between strategic military areas in the continental United States. The system is immune to the effects of high-altitude electromagnetic pulse (HEMP) energy surges caused by nuclear bursts in the ionosphere that would disrupt conventional communications equipment such as telephones and shortwave radios. A failure of such equipment would prevent timely communications among top military and civilian leaders and strategic Air Force locations and prevent U.S. assessment and retaliation during an attack. GWEN is an essential part of a defense modernization program to upgrade and improve our nation's communications system, thereby strengthening deterrence. The GWEN system consists of a network of relay nodes, receive-only stations, and input/output stations. Each relay node, such as the one proposed in southern Nevada consists of a guyed radio tower facility similar to those used by commercial AM broadcast transmitters.

  18. Game theoretic analysis for pricing-based incentive mechanism in non-dedicated cooperative relay networks

    Institute of Scientific and Technical Information of China (English)

    张闯; 赵洪林; 贾敏

    2015-01-01

    In non-dedicated cooperative relay networks, each node is autonomous and selfish in nature, and thus spontaneous cooperation among nodes is challenged. To stimulate the selfish node to participate in cooperation, a pricing-based cooperation engine using game theory was designed. Firstly, the feasible regions of the charge price and reimbursement price were deduced. Then, the non-cooperative and cooperative games were adopted to analyze the amount of bandwidth that initiating cooperation node (ICN) forwards data through participating cooperation node (PCN) and the amount of bandwidth that PCN helps ICN to relay data. Meanwhile, the Nash equilibrium solutions of cooperation bandwidth allocations (CBAs) were obtained through geometrical interpretation. Secondly, a pricing-based cooperation engine was proposed and a cooperative communication system model with cooperation engines was depicted. Finally, an algorithm based on game theory was proposed to realize the cooperation engine. The simulation results demonstrate that, compared with the system without pricing-based incentive, the proposed system can significantly improve the ICN’s metric measured by bit-per-Joule and increase the PCN’s revenue.

  19. Silent and Efficient Supersonic Bi-Directional Flying Wing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a Phase I study for a novel concept of a supersonic bi-directional (SBiDir) flying wing (FW) that has the potential to revolutionize supersonic flight...

  20. Piezoelectric power converter with bi-directional power transfer

    OpenAIRE

    Meyer, Kaspar Sinding; Rødgaard, Martin Schøler; Andersen, Michael A. E.; Andersen, Thomas

    2014-01-01

    The present invention relates to a bi-directional piezoelectric power converter com¬ prising a piezoelectric transformer. The piezoelectric transformer comprises an input electrode electrically coupled to a primary section of the piezoelectric transformer and an output electrode electrically coupled to an output section of the piezoelectric transformer to provide a transformer output signal. A bi-directional switching circuit is coupled between the output electrode and a DC or AC output volta...

  1. Graduation Report: Directional relay coordination in ungrounded medium voltage networks using a real-time digital simulator

    NARCIS (Netherlands)

    Van der Meer, A.A.

    2009-01-01

    The thesis describes a comprehensive protection relay coordination study in ungrounded 10 kV distribution networks. Until now, single phase-toground faults (also: earth-faults) were never interrupted because resulting fault currents were relatively small. Since the earth-fault current amplitude is p

  2. Channel estimation based on distributed compressed sensing in amplify-and-forward relay networks

    Institute of Scientific and Technical Information of China (English)

    WANG Dong-hao; NIU Kai; HE Zhi-qiang; TIAN Bao-yu

    2010-01-01

    In orthogonal frequency-division multiplexing(OFDM)amplify-and-forward(AF)relay networks,in order to exploit diversity gains over frequency-selective fading channels,the receiver needs to acquire the knowledge of channel state information(CSI).In this article,based on the recent methodology of distributed compressed sensing(DCS),a novel channel estimation scheme is proposed.The joint sparsity model 2(JSM-2)in DCS theory and simultaneous orthogonal matching pursuit(SOMP)are both introduced to improve the estimation performance and increase the spectral efficiency.Simulation results show that compared with current compressed sensing(CS)methods,the estimation error of our scheme is reduced dramatically in high SNR region while the pilot number is still kept small.

  3. Interference Neutralization vs Clean Relaying in Cognitive Radio Networks with Secrecy

    Directory of Open Access Journals (Sweden)

    Pin-Hsun Lin

    2015-08-01

    Full Text Available In this paper we study cognitive radio networks with secrecy constraints on the primary transmission. In particular we consider several transmission schemes for the secondary transmitter, namely interference neutralization (IN and cooperative jamming with and without clean relaying (CR. We derive and analyze the achievable secondary rate performance of the schemes. Furthermore we thoroughly investigate the advantages and shortcomings of these schemes through numerical simulations in a geometric model where we highlight the impact of the users’ locations and show the important difference in all schemes depending on the topology. Our results show that the secondary transmitter can successfully adapt its transmission scheme (and parameters, i.e., either IN or CR, depending on its location to maximize its rate while insuring perfect secrecy of the primary transmission.

  4. A User Cooperation Stimulating Strategy Based on Cooperative Game Theory in Cooperative Relay Networks

    Directory of Open Access Journals (Sweden)

    Ping Zhang

    2009-01-01

    Full Text Available This paper proposes a user cooperation stimulating strategy among rational users. The strategy is based on cooperative game theory and enacted in the context of cooperative relay networks. Using the pricing-based mechanism, the system is modeled initially with two nodes and a Base Station (BS. Within this framework, each node is treated as a rational decision maker. To this end, each node can decide whether to cooperate and how to cooperate. Cooperative game theory assists in providing an optimal system utility and provides fairness among users. Under different cooperative forwarding modes, certain questions are carefully investigated, including “what is each node's best reaction to maximize its utility?” and “what is the optimal reimbursement to encourage cooperation?” Simulation results show that the nodes benefit from the proposed cooperation stimulating strategy in terms of utility and thus justify the fairness between each user.

  5. Optimizing Completion Time and Energy Consumption in a Bidirectional Relay Network

    DEFF Research Database (Denmark)

    Liu, Huaping; Sun, Fan; Thai, Chan;

    2012-01-01

    arises for the minimal required energy. While the requirement for minimal energy consumption is obvious, the shortest completion time is relevant when certain multi-node network needs to reserve the wireless medium in order to carry out the data exchange among its nodes. The completion time....../energy consumption required for multiple flows depends on the current channel realizations, transmission methods used and, notably, the relation between the data sizes of different source nodes. In this paper we investigate the shortest completion time and minimal energy consumption in a two-way relay wireless...... uses Decode-and-Forward (DF), each of them is a quadratic optimization problem. The results show that, for given channel realizations, there is an optimal ratio of the data packets at the sources to obtain minimal completion time or energy consumption. This can be used as a guidance for the nodes...

  6. Scalable Ad Hoc Networks for Arbitrary-Cast: Practical Broadcast-Relay Transmission Strategy Leveraging Physical-Layer Network Coding

    Directory of Open Access Journals (Sweden)

    Cai Kai

    2008-01-01

    Full Text Available Abstract The capacity of wireless ad hoc networks is constrained by the interference of concurrent transmissions among nodes. Instead of only trying to avoid the interference, physical-layer network coding (PNC is a new approach that embraces the interference initiatively. We employ a network form of interference cancellation, with the PNC approach, and propose the multihop, broadcast-relay transmission strategy in linear, rectangular, and hexagonal networks. The theoretical analysis shows that it gains the transmission efficiency by the factors of 2.5 for the rectangular networks and 2 for the hexagonal networks. We also propose a practical signal recovery algorithm in the physical layer to deal with the influence of multipath fading channels and time synchronization errors, as well as to use media access control (MAC protocols that support the simultaneous receptions. This transmission strategy obtains the same efficiency from one-to-one communication to one-to-many. By our approach, the number of the users/terminals of the network has better scalability, and the overall network throughput is improved.

  7. On the performance of hybrid ARQ with incremental redundancy over amplify-and-forward dual-hop relay networks

    KAUST Repository

    Hadjtaieb, Amir

    2014-09-01

    In this paper, we consider a three node relay network comprising a source, a relay, and a destination. The source transmits the message to the destination using hybrid automatic repeat request (HARQ) with incremental redundancy (IR). The relay overhears the transmitted message, amplifies it using a variable gain amplifier, and then forwards the message to the destination. This latter combines both the source and the relay message and tries to decode the information. In case of decoding failure, the destination sends a negative acknowledgement. A new replica of the message containing new parity bits is then transmitted in the subsequent HARQ round. This process continues until successful decoding occurs at the destination or a maximum number M of rounds is reached. We study the performance of HARQ-IR over the considered relay channel from an information theoretic perspective. We derive for instance exact expressions and bounds for the information outage probability, the average number of transmissions, and the average transmission rate. The derived exact expressions are validated by Monte Carlo simulations.

  8. Upgrade of a transverse ventilation system in a bi-directional tunnel

    OpenAIRE

    Vidmar Peter; Petelin Stojan; Luin Blaž

    2012-01-01

    The Karavanke tunnel forms an important link between Slovenia and Austria. The almost 8 km long tunnel is operated with bi-directional traffic and does not have dedicated escape routes. Moreover, the ventilation in case of fire does not satisfy requirements of the EU Directive 2004/54/EC that specifies the minimum requirements for tunnels in the trans-European road network. The paper present results of the research conducted regarding the possibility of upgrade the existing system in or...

  9. Global evaluation of ammonia bi-directional exchange

    Directory of Open Access Journals (Sweden)

    L. Zhu

    2015-02-01

    Full Text Available Bi-directional air–surface exchange of ammonia (NH3 has been neglected in many air quality models. In this study, we implement the bi-directional exchange of NH3 in the GEOS-Chem global chemical transport model. We also introduce an updated diurnal variability scheme for NH3 livestock emissions and evaluate the recently developed MASAGE_NH3 bottom up inventory. While updated diurnal variability improves comparison of modeled-to-hourly in situ measurements in the Southeastern US, NH3 concentrations decrease throughout the globe, up to 17 ppb in India and Southeastern China, with corresponding decreases in aerosol nitrate by up to 7 μg m−3. The ammonium (NH4+ soil pool in the bi-directional exchange model largely extends the NH3 lifetime in the atmosphere. Including bi-directional exchange generally increases NH3 gross emissions (7.1% and surface concentrations (up to 3.9 ppb throughout the globe in July, except in India and Southeastern China. In April and October, it decreases NH3 gross emissions in the Northern Hemisphere (e.g., 43.6% in April in China and increases NH3 gross emissions in the Southern Hemisphere. Bi-directional exchange does not largely impact NH4+ wet deposition overall. While bi-directional exchange is fundamentally a better representation of NH3 emissions from fertilizers, emissions from primary sources are still underestimated and thus significant model biases remain when compared to in situ measurements in the US. The adjoint of bi-directional exchange has also been developed for the GEOS-Chem model and is used to investigate the sensitivity of NH3 concentrations with respect to soil pH and fertilizer application rate. This study thus lays the groundwork for future inverse modeling studies to more directly constrain these physical processes rather than tuning bulk uni-directional NH3 emissions.

  10. Power and time slot allocation in cognitive relay networks using particle swarm optimization.

    Science.gov (United States)

    Derakhshan-Barjoei, Pouya; Dadashzadeh, Gholamreza; Razzazi, Farbod; Razavizadeh, S Mohammad

    2013-01-01

    The two main problems in cognitive radio networks are power and time slot allocation problems which require a precise analysis and guarantee the quality of service in both the primary and secondary users. In this paper, these two problems are considered and a method is proposed to solve the resulting optimization problem. Our proposed method provides an improved performance in solving the constrained nonlinear multiobject optimization for the power control and beamforming in order to reach the maximum capacity and proper adaption of time slots, and as a result a new scheme for joint power and time slot allocation in cognitive relay networks is proposed. We adopt space diversity access as the secondary users access scheme and divide the time between multiple secondary users according to their contribution to primary user's transmission. Helping primary users provides more opportunities for secondary users to access the channel since the primary users can release the channel sooner. In contrast, primary network leases portion of channel access time to the secondary users for their transmission using particle swarm optimization (PSO). Numerical studies show good performance of the proposed scheme with a dynamic cost function in a nonstationary environment.

  11. Outage analysis of selective cooperation in underlay cognitive networks with fixed gain relays and primary interference modeling

    KAUST Repository

    Hussain, Syed Imtiaz

    2012-09-01

    Selective cooperation is a well investigated technique in non-cognitive networks for efficient spectrum utilization and performance improvement. However, it is still a nascent topic for underlay cognitive networks. Recently, it was investigated for underlay networks where the secondary nodes were able to adapt their transmit power to always satisfy the interference threshold to the primary users. This is a valid assumption for cellular networks but many non-cellular devices have fixed transmit powers. In this situation, selective cooperation poses a more challenging problem and performs entirely differently. In this paper, we extend our previous work of selective cooperation based on either hop\\'s signal to noise ratio (SNR) with fixed gain and fixed transmit power relays in an underlay cognitive network. This work lacked in considering the primary interference over the cognitive network and presented a rather idealistic analysis. This paper deals with a more realistic system model and includes the effects of primary interference on the secondary transmission. We first derive end-to-end signal to interference and noise ratio (SINR) expression and the related statistics for a dual-hop relay link using asymptotic and approximate approaches. We then derive the statistics of the selected relay link based on maximum end-to-end SINR among the relays satisfying the interference threshold to the primary user. Using this statistics, we derive closed form asymptotic and approximate expressions for the outage probability of the system. Analytical results are verified through simulations. It is concluded that selective cooperation in underlay cognitive networks performs better only in low to medium SNR regions. © 2012 IEEE.

  12. Piezoelectric power converter with bi-directional power transfer

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a bi-directional piezoelectric power converter com¬ prising a piezoelectric transformer. The piezoelectric transformer comprises an input electrode electrically coupled to a primary section of the piezoelectric transformer and an output electrode electrically...... coupled to an output section of the piezoelectric transformer to provide a transformer output signal. A bi-directional switching circuit is coupled between the output electrode and a DC or AC output voltage of the power converter. Forward and reverse current conducting periods of the bi......, a reverse current is conducted through the bi-directional switching circuit from the DC or AC output voltage to the output electrode to discharge the DC or AC output voltage and return power to the primary section of the piezoelectric transformer....

  13. On the Feedback Reduction of Relay Multiuser Networks using Compressive Sensing

    KAUST Repository

    Elkhalil, Khalil

    2016-01-29

    This paper presents a comprehensive performance analysis of full-duplex multiuser relay networks employing opportunistic scheduling with noisy and compressive feedback. Specifically, two feedback techniques based on compressive sensing (CS) theory are introduced and their effect on the system performance is analyzed. The problem of joint user identity and signal-tonoise ratio (SNR) estimation at the base-station is casted as a block sparse signal recovery problem in CS. Using existing CS block recovery algorithms, the identity of the strong users is obtained and their corresponding SNRs are estimated using the best linear unbiased estimator (BLUE). To minimize the effect of feedback noise on the estimated SNRs, a back-off strategy that optimally backs-off on the noisy estimated SNRs is introduced, and the error covariance matrix of the noise after CS recovery is derived. Finally, closed-form expressions for the end-to-end SNRs of the system are derived. Numerical results show that the proposed techniques drastically reduce the feedback air-time and achieve a rate close to that obtained by scheduling techniques that require dedicated error-free feedback from all network users. Key findings of this paper suggest that the choice of half-duplex or full-duplex SNR feedback is dependent on the channel coherence interval, and on low coherence intervals, full-duplex feedback is superior to the interference-free half-duplex feedback.

  14. 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.

  15. Interference and Spectral Efficiency Analysis in Two-hop Cellular Network with Fixed Relays in FDD Mode

    Institute of Scientific and Technical Information of China (English)

    LI Ping; RONG Meng-tian; HUANG Lei; YU Dan

    2006-01-01

    This paper presented a scheme of two-hop cellular network with fixed relay nodes (FRN). Based on this scheme, co-channel interference and signal interference ratio(SIR) received by base station(BS) and FRN were analyzed. Both the theoretical analysis and simulation results show that the SIR can be improved significantly when relays are employed in the network. The higher spectral efficiency can be obtained due to the improved two-hop link quality through the use of adaptive modulation and coding (AMC). The antenna height of FRN and the cell radius of BS and that of FRN influence SIR received by BS and FRN and the system spectral efficiency greatly. The proper antenna height of FRN and cell radius of BS and that of FRN were also given to get the highest spectral efficiency.

  16. Energy-Efficient Packet Relaying in Wireless Image Sensor Networks Exploiting the Sensing Relevancies of Source Nodes and DWT Coding

    Directory of Open Access Journals (Sweden)

    Paulo Portugal

    2013-07-01

    Full Text Available When camera-enabled sensors are deployed for visual monitoring, a new set of innovative applications is allowed, enriching the use of wireless sensor network technologies. In these networks, energy-efficiency is a highly desired optimization issue, mainly because transmission of images and video streams over resource-constrained sensor networks is more stringent than transmission of conventional scalar data. Due to the nature of visual monitoring, that follows a directional sensing model, camera-enabled sensors may have different relevancies for the application, according to the desired monitoring tasks and the current sensors’ poses and fields of view. Exploiting this concept, each data packet may be associated with a priority level related to the packet’s origins, which may be in turn mapped to an energy threshold level. In such way, we propose an energy-efficient relaying mechanism where data packets are only forwarded to the next hop if the associated energy threshold level is below the current energy level of the relaying node. Thus, packets from low-relevant source nodes will be silently dropped when the current energy level of intermediate nodes run below the pre-defined thresholds. Doing so, energy is saved potentially prolonging the network lifetime. Besides the sensing relevancies of source nodes, the relevance of DWT subbands for reconstruction of original images is also considered. This allows the creation of a second level of packet prioritization, assuring a minimal level of image quality even for the least relevant source nodes. We performed simulations for the proposed relaying mechanism, assessing the expected performance over a traditional relaying paradigm.

  17. Performance Impairments due to Gain Transients in a Raman-based Bi-directional Long-reach PON Link

    DEFF Research Database (Denmark)

    Kjær, Rasmus; Tafur Monroy, Idelfonso; Jensen, Jesper Bevensee;

    2007-01-01

    A Raman-based bi-directional long-reach passive optical network (PON) link was proposed and had shown to be very robust toward WDM channel add/drops and therefore look promising for future high-capacity fiber-to-the-premises (FTTP) systems with bursty traffic. Penalty measurements on a weak data...

  18. Application of Multihop Relay for Performance Enhancement of AeroMACS Networks

    Science.gov (United States)

    Kamali, Behnam; Wilson, Jeffrey D.; Kerczewski, Robert J.

    2012-01-01

    A new transmission technology, based on IEEE 802.16-2009 (WiMAX), is currently being developed for airport surface communications. A C-band spectrum allocation at 5091 to 5150 MHz has been created by International Telecommunications Union (ITU) to carry this application. The proposed technology, known as AeroMACS, will be used to support fixed and mobile ground to ground applications and services. This article proposes and demonstrates that IEEE 802.16j-amendment-based WiMAX is most feasible for AeroMACS applications. This amendment introduces multihop relay as an optional deployment that may be used to provide additional coverage and/or enhance the capacity of the network. Particular airport surface radio coverage situations for which IEEE 802.16-2009-WiMAX provides resolutions that are inefficient, costly, or excessively power consuming are discussed. In all these cases, it is argued that 16j technology offers a much better alternative. A major concern about deployment of AeroMACS is interference to co-allocated applications such as the Mobile Satellite Service (MSS) feeder link. Our initial simulation results suggest that no additional interference to MSS feeder link is caused by deployment of IEEE 802.16j-based AeroMACS.

  19. Load-adaptive frequency reuse scheme for inter-cell interference coordination in relay networks

    Institute of Scientific and Technical Information of China (English)

    CHEN Mu-qiong; JI Hong; LI Xi

    2010-01-01

    Cellular relay networks adopting orthogonal frequency division multiple(OFDM)technology has been widely accepted for next generation wireless communication due to its advantage in enlarging coverage scale as well as improving data rate.In order to improve the performance of user equipments(UEs)near the cell edge,especially to avoid the interference from inter-cell and intra cell,an enhanced soft frequency reuse scheme is adopted in this paper to assure inter-cell interference coordination(ICIC).Compared with traditional frequency allocation work,the proposed scheme is interference-aware and load-adaptive,which dynamically assigns available frequency among UES under certain schedule method in variable traffic load condition and mitigates interference using information provided by interference indicator.It can improve signal-to-interference plus noise ratio(SINR)of the UE in each sub channel thus enable the system achieve better throughput and blocking probability performance.Simulation results prove that the proposed scheme may achieve desirable performance on throughput,blocking probability and spectral utilization in the sector under different traffic load compared with other schemes.

  20. Interference-Based Decode and Forward Scheme Using Relay Nodes in Heterogeneous Networks

    Directory of Open Access Journals (Sweden)

    Kentaro Nishimori

    2012-01-01

    Full Text Available This paper proposes interference-based decode and forward scheme that utilizes relay stations (RSs. In Long-Term-Evolution (LTE- Advanced, heterogeneous networks in which femto- and picocells are overlaid onto macrocells are extensively discussed. However, interference between macro- and pico(femtocells arises due to their different transmit power levels. Unlike conventional cooperative transmission schemes, the RS decodes interference in the first transmit timing period and forwards it to the user equipment (UE in the second period. Moreover, cooperative transmission can be achieved without stopping the transmission from the base station (BS to UE when forwarding the interference from the RS to the UE by utilizing the fact that signal-to-noise power ratio (SNR between the RS and UE is much greater than that between the BS and UE. The basic performance of the proposed method is shown based on computer simulation. Moreover, the interference temperature and shadowing effect are measured when considering the coexistence between macro- and femtocells, and the performance of the proposed method is verified using measured shadowing effect.

  1. Applying Hybrid PSO to Optimize Directional Overcurrent Relay Coordination in Variable Network Topologies

    Directory of Open Access Journals (Sweden)

    Ming-Ta Yang

    2013-01-01

    Full Text Available In power systems, determining the values of time dial setting (TDS and the plug setting (PS for directional overcurrent relays (DOCRs is an extremely constrained optimization problem that has been previously described and solved as a nonlinear programming problem. Optimization coordination problems of near-end faults and far-end faults occurring simultaneously in circuits with various topologies, including fixed and variable network topologies, are considered in this study. The aim of this study was to apply the Nelder-Mead (NM simplex search method and particle swarm optimization (PSO to solve this optimization problem. The proposed NM-PSO method has the advantage of NM algorithm, with a quicker movement toward optimal solution, as well as the advantage of PSO algorithm in the ability to obtain globally optimal solution. Neither a conventional PSO nor the proposed NM-PSO method is capable of dealing with constrained optimization problems. Therefore, we use the gradient-based repair method embedded in a conventional PSO and the proposed NM-PSO. This study used an IEEE 8-bus test system as a case study to compare the convergence performance of the proposed NM-PSO method and a conventional PSO approach. The results demonstrate that a robust and optimal solution can be obtained efficiently by implementing the proposal.

  2. Transfer of Pragmatic Competences: A Bi-Directional Perspective

    Science.gov (United States)

    Su, I-Ru

    2010-01-01

    This study investigated the bi-directionality of language transfer (first language [L1] to second language [L2] and L2 to L1) at the pragmatic level with a focus on the speech act of request. The L2 participants were Chinese English as a foreign language (EFL) learners at the intermediate and advanced levels. Data were collected via discourse…

  3. Bi-directional Secure Communication Based on Discrete Chaotic Synchronization

    Institute of Scientific and Technical Information of China (English)

    LONG Min; QIU Shui-Sheng; PENG Fei

    2007-01-01

    Discrete chaotic systems are used for bi-directional secure communication. Both sides of communication keep sending signals to achieve their synchronization, and then recover the messages. However, the third side without keys cannot get useful information. Known-plaintext attack is also engaged to analyze this method, and the simulation results show that the proposed method can reach high security performance.

  4. Spectrum Sharing between Cooperative Relay and Ad-hoc Networks: Dynamic Transmissions under Computation and Signaling Limitations

    CERN Document Server

    Sun, Yin; Li, Yunzhou; Zhou, Shidong; Xu, Xibin

    2010-01-01

    This paper studies a spectrum sharing scenario between an uplink cognitive relay network (CRN) and some nearby low power ad-hoc networks. In particular, the dynamic resource allocation of the CRN is analyzed, which aims to minimize the average interfering time with the ad-hoc networks subject to a minimal average uplink throughput constraint. A long term average rate formula is considered, which is achieved by a half-duplex decode-and-forward (DF) relay strategy with multi-channel transmissions. Both the source and relay are allowed to queue their data, by which they can adjust the transmission rates flexibly based on sensing and predicting the channel state and ad-hoc traffic. The dynamic resource allocation of the CRN is formulated as a non-convex stochastic optimization problem. By carefully analyzing the optimal transmission time scheduling, it is reduced to a stochastic convex optimization problem and solved by the dual optimization method. The signaling and computation processes are designed carefully t...

  5. PERFORMANCE ANALYSIS OF USER FAIR-BASED RELAY ADAPTIVE POWER ALLOCATION IN PHYSICAL-LAYER NETWORK CODING COOPERATION

    Institute of Scientific and Technical Information of China (English)

    Cheng Yulun; Yang Longxiang

    2012-01-01

    Network Coding (NC) is an effective technology to enhance the cooperative system spectral efficiency.However,since it is network-oriented,the existing performance metric of single-user outage can not comprehensively evaluate its gain and the impact to the entire network,which affect the user fairness.This paper proposes two novel user fair-based adaptive relay power allocation algorithms in single-relay NC cooperative multiple access channels.Firstly,common outage probability is employed as the performance metric,and to minimize it,a specific condition is deduced.On this basis,the instantaneous channel information-based adaptive relay power allocation scheme and the channel statistic information-based one with lower complexity are designed respectively,which make users' signals superimposed at accurately calculated proportion to maintain fairness.Simulation results show that compared with other existing schemes,the proposed schemes can best maintain user fairness,and effectively improve the common outage performance of the whole system,at the expense of small spectral efficiency.

  6. Modeling and Simulation of a Novel Relay Node Based Secure Routing Protocol Using Multiple Mobile Sink for Wireless Sensor Networks.

    Science.gov (United States)

    Perumal, Madhumathy; Dhandapani, Sivakumar

    2015-01-01

    Data gathering and optimal path selection for wireless sensor networks (WSN) using existing protocols result in collision. Increase in collision further increases the possibility of packet drop. Thus there is a necessity to eliminate collision during data aggregation. Increasing the efficiency is the need of the hour with maximum security. This paper is an effort to come up with a reliable and energy efficient WSN routing and secure protocol with minimum delay. This technique is named as relay node based secure routing protocol for multiple mobile sink (RSRPMS). This protocol finds the rendezvous point for optimal transmission of data using a "splitting tree" technique in tree-shaped network topology and then to determine all the subsequent positions of a sink the "Biased Random Walk" model is used. In case of an event, the sink gathers the data from all sources, when they are in the sensing range of rendezvous point. Otherwise relay node is selected from its neighbor to transfer packets from rendezvous point to sink. A symmetric key cryptography is used for secure transmission. The proposed relay node based secure routing protocol for multiple mobile sink (RSRPMS) is experimented and simulation results are compared with Intelligent Agent-Based Routing (IAR) protocol to prove that there is increase in the network lifetime compared with other routing protocols. PMID:26495426

  7. QoS Constrained Optimal Sink and Relay Placement in Planned Wireless Sensor Networks

    OpenAIRE

    Bhattacharya, Abhijit; Rao, Akhila; Naveen, K. P.; Nishanth, P. P.; Anand, S. V. R.; Kumar, Anurag

    2014-01-01

    We are given a set of sensors at given locations, a set of potential locations for placing base stations (BSs, or sinks), and another set of potential locations for placing wireless relay nodes. There is a cost for placing a BS and a cost for placing a relay. The problem we consider is to select a set of BS locations, a set of relay locations, and an association of sensor nodes with the selected BS locations, so that number of hops in the path from each sensor to its BS is bounded by hmax, an...

  8. 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.

  9. Energy-Efficient Power Allocation for Fixed-Gain Amplify-and-Forward Relay Networks with Partial Channel State Information

    KAUST Repository

    Zafar, Ammar

    2012-06-01

    In this report, energy-efficient transmission and power allocation for fixed-gain amplify-and-forward relay networks with partial channel state information (CSI) are studied. In the energy-efficiency problem, the total power consumed is minimized while keeping the signal-to-noise-ratio (SNR) above a certain threshold. In the dual problem of power allocation, the end-to-end SNR is maximized under individual and global power constraints. Closed-form expressions for the optimal source and relay powers and the Lagrangian multiplier are obtained. Numerical results show that the optimal power allocation with partial CSI provides comparable performance as optimal power allocation with full CSI at low SNR.

  10. Energy-Efficient Power Allocation for Fixed-Gain Amplify-and-Forward Relay Networks with Partial Channel State Information

    KAUST Repository

    Zafar, Ammar

    2012-09-16

    In this letter, energy-efficient transmission and power allocation for fixed-gain amplify-and-forward relay networks with partial channel state information (CSI) are studied. In the energy-efficiency problem, the total power consumed is minimized while keeping the signal-to-noise-ratio (SNR) above a certain threshold. In the dual problem of power allocation, the end-to-end SNR is maximized under individual and global power constraints. Closed-form expressions for the optimal source and relay powers and the Lagrangian multiplier are obtained. Numerical results show that the optimal power allocation with partial CSI provides comparable performance as optimal power allocation with full CSI at low SNR. © 2012 IEEE.

  11. Near-optimal power allocation with PSO algorithm for MIMO cognitive networks using multiple AF two-way relays

    KAUST Repository

    Alsharoa, Ahmad M.

    2014-06-01

    In this paper, the problem of power allocation for a multiple-input multiple-output two-way system is investigated in underlay Cognitive Radio (CR) set-up. In the CR underlay mode, secondary users are allowed to exploit the spectrum allocated to primary users in an opportunistic manner by respecting a tolerated temperature limit. The secondary networks employ an amplify-and-forward two-way relaying technique in order to maximize the sum rate under power budget and interference constraints. In this context, we formulate an optimization problem that is solved in two steps. First, we derive a closed-form expression of the optimal power allocated to terminals. Then, we employ a strong optimization tool based on particle swarm optimization algorithm to find the power allocated to secondary relays. Simulation results demonstrate the efficiency of the proposed solution and analyze the impact of some system parameters on the achieved performance. © 2014 IEEE.

  12. 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

  13. 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

  14. Bi-directional associations between psychological arousal, cortisol, and sleep

    DEFF Research Database (Denmark)

    Garde, Anne Helene; Albertsen, Karen; Persson, Roger;

    2012-01-01

    The aim was to elucidate the possible bi-directional relation between daytime psychological arousal, cortisol, and self-reported sleep in a group of healthy employees in active employment. Logbook ratings of sleep (Karolinska Sleep Questionnaire), stress, and energy, as well as positive and negat......The aim was to elucidate the possible bi-directional relation between daytime psychological arousal, cortisol, and self-reported sleep in a group of healthy employees in active employment. Logbook ratings of sleep (Karolinska Sleep Questionnaire), stress, and energy, as well as positive...... and problems during the day. The results underpin the possibility that arousal and poor sleep might create a self-reinforcing vicious circle that negatively affects a person's well-being....

  15. High Voltage Bi-directional Flyback Converter for Capacitive Actuator

    DEFF Research Database (Denmark)

    Thummala, Prasanth; Zhang, Zhe; Andersen, Michael A. E.

    2013-01-01

    This paper presents a high voltage DC-DC converter topology for bi-directional energy transfer between a low voltage DC source and a high voltage capacitive load. The topology is a bi-directional flyback converter with variable switching frequency control during the charge mode, and constant...... switching frequency control during the discharge mode. The converter is capable of charging the capacitive load from 24 V DC source to 2.5 kV, and discharges it to 0 V. The flyback converter has been analyzed in detail during both charge and discharge modes, by considering all the parasitic elements...... in the converter, including the most dominating parameters of the high voltage transformer viz., self-capacitance and leakage inductance. The specific capacitive load for this converter is a dielectric electro active polymer (DEAP) actuator, which can be used as an effective replacement for conventional actuators...

  16. Bi-directional normalized difference vegetation index: concept and application

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The data products of land surface bi-directional reflectance distribution function (BRDF) from the space-borne Polarization and Directionality of the Earth Reflectance (POLDER) of France and the Moderate Resolution Imaging Spectroradiometer (MODIS)of USA are available recently, but the atmospheric correction for meeting the requirement of quantitative remote sensing is still a very dfficult problem. This paper presents a concept: bi-directional normalized difference vegetation index (Bi-NDVI), in order to consider simul taneously the effects of both land surface BRDF and atmospheric path scattering. An atmospheric quality index is thus defined for satellite multi-angular observations. The quality of MODIS/BRDF data products can be improved notably through iterative inversion weighed by this index.

  17. Joint sub-carrier pairing and resource allocation for cognitive networks with adaptive relaying

    KAUST Repository

    Soury, H.

    2013-11-09

    Relayed transmission in a cognitive radio (CR) environment could be used to increase the coverage and capacity of communication system that benefits already from the efficient management of the spectrum developed by CR. Furthermore, there are many types of cooperative communications, including decode-and-forward (DAF) and amplify-and-forward (AAF). In this paper, these techniques are combined in an adaptive mode to benefit from its forwarding advantages; this mode is called adaptive relaying protocol (ARP). Moreover, this work focuses on the joint power allocation in a cognitive radio system in a cooperative mode that operates ARP in multi-carrier mode. The multi-carrier scenario is used in an orthogonal frequency division multiplexing (OFDM) mode, and the problem is formulated to maximize the end-to-end rate by searching the best power allocation at the transmitters. This work includes, besides the ARP model, a sub-carrier pairing strategy that allows the relays to switch to the best sub-carrier pairs to increase the throughput. The optimization problem is formulated and solved under the interference and power budget constraints using the sub-gradient algorithm. The simulation results confirm the efficiency of the proposed adaptive relaying protocol in comparison to other relaying techniques. The results show also the consequence of the choice of the pairing strategy. 2013 Stolojescu-Crisan and Isar; licensee Springer.

  18. Hybrid battery with bi-directional DC/DC converter

    Directory of Open Access Journals (Sweden)

    DUDRIK Jaroslav

    2010-05-01

    Full Text Available Bi-directional buck-boost DC/DC converterfor hybrid battery is described in this paper. The firstpart of the paper is aimed at concept of hybrid battery;main advance compared to conventional accumulatoris explained there. Control circuit with UC3637 andpower circuit of the converter are described in thesecond part of the paper. Experimental results frommeasuring of converter are mentioned in the last part.

  19. Hybrid battery with bi-directional DC/DC converter

    OpenAIRE

    DUDRIK Jaroslav; OLEJAR Martin; BERES Tomáš

    2010-01-01

    Bi-directional buck-boost DC/DC converterfor hybrid battery is described in this paper. The firstpart of the paper is aimed at concept of hybrid battery;main advance compared to conventional accumulatoris explained there. Control circuit with UC3637 andpower circuit of the converter are described in thesecond part of the paper. Experimental results frommeasuring of converter are mentioned in the last part.

  20. Average Sum-Rate of Distributed Alamouti Space--Time Scheme in Two-Way Amplify-and-Forward Relay Networks

    CERN Document Server

    Duong, Trung Q; Zepernick, Hans-Jurgen; Lei, Xianfu

    2010-01-01

    In this paper, we propose a distributed Alamouti space-time code (DASTC) for two-way relay networks employing a single amplify-and-forward (AF) relay. We first derive closed-form expressions for the approximated average sum-rate of the proposed DASTC scheme. Our analysis is validated by a comparison against the results of Monte-Carlo simulations. Numerical results verify the effectiveness of our proposed scheme over the conventional DASTC with one-way communication.

  1. Spectrum Sharing between Cooperative Relay and Ad-hoc Networks: Dynamic Spectrum Access, Resource Allocation and Real-time Implementation

    CERN Document Server

    Sun, Yin; Chang, Tsung-Hui; Zhou, Shidong; Wang, Jing; Chi, Chong-Yung

    2011-01-01

    This paper studies the spectrum sharing problem between a cooperative relay network (CRN) and a nearby ad-hoc network that operates over the same spectral band. In the uplink CRN transmission, both the source node and relay node can interfere with the ad-hoc links. By virtue of that the CRN can predict the ad-hoc traffic through spectrum sensing, we optimize the spectrum access and resource allocation strategy of the CRN such that the average traffic collision time between the two networks can be minimized while maintaining a required uplink throughput for the CRN. The associated design formulation turns out to be a non-convex optimization problem. By analyzing the optimal spectrum access strategy, we show that this spectrum sharing problem can be reformulated as a convex problem and solved by a low-complexity Lagrangian optimization method. The development is first for a frame level resource allocation strategy, and then is further extended to an ergodic resource allocation strategy that considers long term ...

  2. Image Segmentation using bi directional of neural network

    Directory of Open Access Journals (Sweden)

    HimadriNath Moulick

    2016-07-01

    Full Text Available Now a days image processing methods are widely used in medical science, to improve critical disease detection and fast treatment for recovery. Mainly this mechanism detects the disease as soon as possible and also find out the exact point of disorder and calculate the growth of this disease,especially in Squamous cell carcinoma in lower lip. Actinic keratosis which is 1/4 inch in diameter, isa pink or flesh coloured rough spot is one of the most important cause of squamous cell carcinoma,which is mainly grown in sun-exposed area. It is usually grow slowly and affects epidermis layer todermis layer. Our proposed method focuses on five different modules. These methods are including inImage Acquisition module and respective Pre-processing ,Segmentation , Filtering Phase and Edge Detection modules.

  3. Bi-Directional DC-DC Converter for PHEV Applications

    Energy Technology Data Exchange (ETDEWEB)

    Abas Goodarzi

    2011-01-31

    Plug-In Hybrid Electric Vehicles (PHEV) require high power density energy storage system (ESS) for hybrid operation and high energy density ESS for Electric Vehicle (EV) mode range. However, ESS technologies to maximize power density and energy density simultaneously are not commercially feasible. The use of bi-directional DC-DC converter allows use of multiple energy storage, and the flexible DC-link voltages can enhance the system efficiency and reduce component sizing. This will improve fuel consumption, increase the EV mode range, reduce the total weight, reduce battery initial and life cycle cost, and provide flexibility in system design.

  4. Coverage extension and balancing the transmitted power of the moving relay node at LTE-A cellular network.

    Science.gov (United States)

    Aldhaibani, Jaafar A; Yahya, Abid; Ahmad, R Badlishah

    2014-01-01

    The poor capacity at cell boundaries is not enough to meet the growing demand and stringent design which required high capacity and throughput irrespective of user's location in the cellular network. In this paper, we propose new schemes for an optimum fixed relay node (RN) placement in LTE-A cellular network to enhance throughput and coverage extension at cell edge region. The proposed approach mitigates interferences between all nodes and ensures optimum utilization with the optimization of transmitted power. Moreover, we proposed a new algorithm to balance the transmitted power of moving relay node (MR) over cell size and providing required SNR and throughput at the users inside vehicle along with reducing the transmitted power consumption by MR. The numerical analysis along with the simulation results indicates that an improvement in capacity for users is 40% increment at downlink transmission from cell capacity. Furthermore, the results revealed that there is saving nearly 75% from transmitted power in MR after using proposed balancing algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain.

  5. A SELF-ORGANIZED RESOURCE ALLOCATION USING INTER-CELL INTERFERENCE COORDINATION (ICIC IN RELAY-ASSISTED CELLULAR NETWORKS

    Directory of Open Access Journals (Sweden)

    Mahima Mehta

    2011-06-01

    Full Text Available In a multi-cell scenario, the inter-cell interference (ICI is detrimental in achieving the intended system performance, in particular for the edge users. There is paucity of work available in literature on ICI coordination (ICIC for relay-assisted cellular networks (RACN. In this paper, we do a survey on the ICIC schemes in cellular networks and RACN. We then propose a self-organized resource allocation plan for RACN to improve the edge user’s performance by ICIC. We compare the performance of reuse-1, reuse-3, soft frequency reuse (SFR scheme, proposed plan with and without relays. The performance metrics for comparison are edge user’s spectral efficiency, their signal-to-interference-and-noise ratio (SINR and system’s area spectral efficiency. We show by the simulation results that our proposed plan performs better than the existing resource allocation schemes in static allocation scenario. Next, we propose to make our resource allocation plan dynamic and self-organized. The distinct features of our proposed plan are: One, it achieves a trade-off between the system’s area spectral efficiency and the edge user’s spectral efficiency performance. Secondly, it introduces a novel concept of interfering neighbor set to achieve ICIC by local interaction between the entities.

  6. On the performance of future full-duplex relay selection networks

    KAUST Repository

    Khafagy, Mohammad Galal

    2015-09-01

    In this work, we evaluate the performance of relay selection over Nakagami-m fading channels in the presence of a cluster of full-duplex decode-and-forward relays with self-interference. Specifically, we derive the exact cumulative distribution function of the end-to-end signal-to-interference-plus-noise ratio in the presence of a direct source-destination link. When a direct link exists, all dual-hop paths become mutually correlated due to the common direct-link interference. The presented exact results enable the evaluation of the outage performance and system throughput for fixed-rate transmission systems. The theoretical findings are verified by numerical simulations, where the severity of fading effect in the residual self-interference link is also discussed.

  7. Towards increasing packet diversity for relaying LT Fountain Codes in Wireless Sensor Networks

    OpenAIRE

    Apavatjrut, Anya; Goursaud, Claire; Jaffrès-Runser, Katia; Comaniciu, Cristina; Gorce, Jean-Marie

    2010-01-01

    Diversity is a powerful means to increase the transmission performance of wireless communications. For the case of fountain codes relaying, it has been shown previously that introducing diversity is also beneficial since it counteracts transmission losses on the channel. Instead of simply hop-by-hop forwarding information, each sensor node diversifies the information flow using XOR combinations of stored packets. This approach has been shown to be efficient for random linear fountain codes. H...

  8. Towards increasing diversity for the relaying of LT Fountain Codes in Wireless Sensor Networks

    OpenAIRE

    Anya, Apavatjrut; Goursaud, Claire; Jaffrès-Runser, Katia; Comaniciu, Cristina; Gorce, Jean-Marie

    2010-01-01

    Diversity is a powerful means to increase the transmission performance of wireless communications. For the case of fountain codes relaying, it has been shown previously that introducing diversity is also beneficial since it counteracts transmission losses on the channel. Instead of simply hop-by-hop forwarding information, each sensor node diversifies the information flow using XOR combinations of stored packets. This approach has been shown to be efficient for random linear fountain codes. H...

  9. Energy Efficiency Maximization Based on Cooperative sensing in Cognitive Relay Networks

    OpenAIRE

    Yaolian Song; Guangzeng Feng; Xuanhui Xi

    2013-01-01

    In this paper, we investigate the energy efficiency maximization problem of cognitive radio systems. We propose to study energy efficiency of cognitive relay transmission scheme based on cooperative spectrum sensing, since empirical studies have shown that optimal sensing time and transmit power are key factors for energy efficiency maximization. We design a method that simultaneously considers the parameters of spectrum sensing time and transmit power. Finally, we conduct deep experiments wh...

  10. Steady-state analysis of the integrated natural gas and electric power system with bi-directional energy conversion

    DEFF Research Database (Denmark)

    Zeng, Qing; Fang, Jiakun; Liu, Jinghua;

    2016-01-01

    Nowadays, the electric power system and natural gas network are becoming increasingly coupled and interdependent. A harmonized integration of natural gas and electricity network with bi-directional energy conversion is expected to accommodate high penetration levels of renewables in terms of system...... flexibility. This work focuses on the steady-state analysis of the integrated natural gas and electric power system with bi-directional energy conversion. A unified energy flow formulation is developed to describe the nodal balance and branch flow in both systems and it is solved with the Newton...... series of wind power and power load are used to investigate the mitigation effect of the integrated energy system. At last, the effect of wind power and power demand on the output of Power to Gas (P2G) and gas-fired power generation (GPG) has also been investigated....

  11. Ground wave emergency network final operational capability: Environmental assessment for southern Nevada relay node site number RN 8W918NV

    Science.gov (United States)

    1993-03-01

    The Ground Wave Emergency Network (GWEN) is a radio communication system designed to relay emergency messages between strategic military areas in the continental United States. The system is immune to the effects of high-altitude electromagnetic pulse (HEMP) energy surges caused by nuclear bursts in the ionosphere that would disrupt conventional communications equipment such as telephones and shortwave radios. A failure of such equipment would prevent timely communications among top military and civilian leaders and strategic Air Force locations and prevent U.S. assessment and retaliation during an attack. GWEN is an essential part of a defense modernization program to upgrade and improve our nation's communications system, thereby strengthening deterrence. The GWEN system consists of a network of relay nodes, receive-only stations, and input/output stations. Each relay node, such as the one proposed in southern Nevada consists of a guyed radio tower facility similar to those used by commercial AM broadcast transmitters.

  12. Ground wave emergency network final operational capability: Environmental assessment for northwestern Nebraska relay node, site number RN 8C930NE

    Science.gov (United States)

    1993-02-01

    The Ground Wave Emergency Network (GWEN) is a radio communication system designed to relay emergency messages between strategic military areas in the continental United States. The system is immune to the effects of high-altitude electromagnetic pulse (HEMP) energy surges caused by nuclear bursts in the ionosphere that would disrupt conventional communications equipment such as telephones and shortwave radios. A failure of such equipment would prevent timely communications among top military and civilian leaders and strategic Air Force locations and prevent U.S. assessment and retaliation during an attack. GWEN is an essential part of a defense modernization program to upgrade and improve our nation's communications system, thereby strengthening deterrence. The GWEN system consists of a network of relay nodes, receive-only stations, and input/output stations. Each relay node, such as the one proposed in northwestern Nebraska, consists of a guyed radio tower facility similar to those used by commercial AM broadcast transmitters.

  13. Regenerative Strategy for Sum-rate Enhancement in Bi-directional Three-node Cooperation

    Institute of Scientific and Technical Information of China (English)

    Hu Ning; Zhong Xiaofeng; Zhao Ming; Wang Jing

    2009-01-01

    In bi-directional three-node cooperation, one regenerative strategy with network coding and power optimization is proposed for system sum-rate under a total energy constraint. In this paper, the network coding and power optimization are applied to improve system sum-rate. But max-min optimization problem in power allocation is a NP-hard problem. In high Signal-to-Noise Ratio regime, this NP-hard problem is transformed into constrained polynomial optimization problem, which can be computed in polynomial time. Although it is a suboptimal solution, numerical simulations show that this strategy enhances the system sum-rate up to 45% as compared to a traditional four-phase strategy, and up to 13% as compared to the three-phase strategy without power optimization.

  14. Power system transient stability simulation based on module bi-directional iteration

    Institute of Scientific and Technical Information of China (English)

    FANG; Dazhong; YANG; Xiaodong

    2005-01-01

    A new simultaneous solution method using module bi-directional iteration is proposed for power system transient stability simulation. In this method, power network is partitioned into a tree hierarchy; computation modules are established for decomposed power networks and various power system components respectively. Through representing every computation module by a computation node, a computation tree is constructed by connecting the nodes together according to their electrical relations in power systems. A tree-traversing procedure called forward reduction and backward evaluation is performed to calculate correction factors of the variables in Newton iterations. This high-efficiency simulation method is feasible to be applied in parallel computation for large interconnected systems. Simulation tests are conducted on the New England 10-generator test power system and the North China-Northeast interconnected system, and the results are compared with those of the commercial software BPA to validate the effectiveness and correctness of this method.

  15. Conflict-Aware Relay Selection for Multicast in MUD based Wireless Networks

    OpenAIRE

    Asma Ben Hassouna; Hend Koubaa; Farouk Kamoun

    2013-01-01

    Multipoint Relays (MPR) [1] selection is a good step toward building a very proficient routing scheme for multicast/broadcast communications. It considers the fact that data transmitted by a node is overheard by all the users in the sender’s communication range, called the Wireless Broadcast Advantage (WBA) [2][4][6]. However, when a node elects its MPR nodes it does not consider their channel qualities (i.e. they do not consider the Multi-User Diversity (MUD) [3][5] factor), that has a...

  16. Sum-Rate Optimization in a Two-Way Relay Network with Buffering

    DEFF Research Database (Denmark)

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

    2013-01-01

    to the destination is poor, then RS stores more data from the source, in order to use it when the channel to the destination is good. We apply this intuition to the case of half-duplex two-way relaying, where the interactions among the buffers and links become more complex. We investigate the sum-rate maximization...... problem in the Time Division Broadcast (TDBC): the users send signals to the RS in different time slots, the RS decodes and stores messages in the buffers. For downlink transmission, the RS re-encodes and sends using the optimal broadcast strategy. The operation in each time slot is not determined...

  17. Energy Efficiency Maximization Based on Cooperative sensing in Cognitive Relay Networks

    Directory of Open Access Journals (Sweden)

    Yaolian Song

    2013-08-01

    Full Text Available In this paper, we investigate the energy efficiency maximization problem of cognitive radio systems. We propose to study energy efficiency of cognitive relay transmission scheme based on cooperative spectrum sensing, since empirical studies have shown that optimal sensing time and transmit power are key factors for energy efficiency maximization. We design a method that simultaneously considers the parameters of spectrum sensing time and transmit power. Finally, we conduct deep experiments which show that our proposed approach can significantly improve the throughput and energy efficiency than the non-cooperative spectrum sensing method.

  18. Design of zone-based bandwidth management scheme in IEEE 802.16 multi-hop relay networks

    Directory of Open Access Journals (Sweden)

    Chen Kuo-Yang

    2011-01-01

    Full Text Available Abstract IEEE 802.16 Wireless Network technology is a hot research issue in recent years. It provides wider coverage of radio and higher speed wireless access, and Quality-of-Service plays an important part in the standard. For mobile multi-hop wireless network, IEEE 802.16j/MR network not only can supply large area wireless deployment, but also can provide high quality network service to mobile users. Although Mobile QoS supporting has been extensively investigated, Mobile QoS supporting in the IEEE 802.16-MR network is relatively unexplored. In this article, the probability of a mobile user who visits a Relay Station (RS is known beforehand. With the visiting probability at each RS and the system specified size of the range for bandwidth allocation, Base Station (BS can calculate the required bandwidth to meet the mobile user's demand and allocate appropriate bandwidth for a mobile user roaming in the range of the bandwidth allocation. The range of bandwidth allocation for mobile users is called the Zone in this article, which includes the user's current RS and the nearby RSs. The proposed scheme is therefore called Zone-based bandwidth management scheme. The simulation results demonstrate that Zone-based bandwidth management scheme can reduce QoS degradation and bandwidth re-allocation overhead.

  19. Bi-directional charger for swiss2G - Annual report; Bi-directional charger for swiss2G - Jahresbericht

    Energy Technology Data Exchange (ETDEWEB)

    Schwab, M.; Baumann, P.

    2010-11-15

    This short annual report for 2010 for the Swiss Federal Office of Energy (SFOE) takes a look at a bi-directional charger that can be used in intelligent 'Smart Grid' applications. The idea is based on being able to use electric vehicles as a source of electricity to help meet peak demand for mains electricity. The swiss2G project aims to produce an electric car battery-charger that also functions as an inverter to convert the car's DC battery voltage to mains electricity. The project was started in September 2010. The report describes the aims of the project and reports on initial work done in the areas of safety, switching electronics and AC/DC conversion. National and international co-operation is noted and prospects for further work are discussed.

  20. Application of Intelligent Motor Relaying Device in Network Deployment%智能型电动机保护器及其组网应用

    Institute of Scientific and Technical Information of China (English)

    言穆昀

    2013-01-01

    智能型电动机保护器具有保护和通信功能,渐渐替代了传统的热继电器,并进入普及阶段.现代化市政行业中利用智能型电动机保护器的网络通信功能可实现组网需求,大大简化了现场接线,提高了管理水平.%The function of protection and telecommunication was realized by the intelligent motor relaying device, which gradually took the place of the thermal relays, moreover it was went in popularization. The requirement of the network deployment could be realized by the function of the internet telecommunication of the intellgent motor relaying device in the modem municipal field. The wive splice on-site was largely simplized, management level was enhanced.

  1. Risk factors affecting inoperability virtual private network technologies to Frame Relay and X.25

    Directory of Open Access Journals (Sweden)

    Beatriz Perozo

    2010-10-01

    Full Text Available El propósito de este estudio fue determinar cuales son los factores principales de riesgos Internos, externos y administrativos que influyen en la inoperatividad de las Redes Privadas Virtuales bajo la plataforma Frame Relay y X.25, El tipo de investigación es de campo y descriptiva, y la modalidad corresponde a Proyecto Factible, bajo el criterio del diseño no experimental. La población estuvo integradas por los Cinco (5 expertos que laboran en el departamento de Informática y Telecomunicaciones de la mencionada empresa. Se utilizó como instrumento de medición cualitativa la entrevista, cara a cara, informativa y estructurada, debido a la naturaleza del instrumento fue necesario utilizar para el tratamiento de la información un esquema no convencional, la cual requirió además de la validación de los expertos. Otra de las técnicas de recolección que se utilizó fue la Observación, no estructurada, participante e individual. Los resultados obtenidos identificaron factores de riesgo que atenta con la interoperatividad de las redes privada virtuales con las tecnologías antes mencionadas, a nivel de infraestructura de interconexión, Indicadores de rendimiento, factores administrativos, estos últimos evidencian que el incumplimiento de los contratos por parte de los proveedores de servicios (Carrier. También se convierten en una amenaza directa que incide en la inoperancia de la red, pues lo ideal seria el intercambio de información, sin interrupción ni errores y en tiempo real, que es lo que a ciencia cierta requiere toda organización.Palabras Clave:Factores de riesgos, Redes Privadas Virtuales, Tecnologías Frame Relay y X.25

  2. Data Gathering in Networks of Bacteria Colonies: Collective Sensing and Relaying Using Molecular Communication

    CERN Document Server

    Einolghozati, Arash; Beirami, Ahmad; Fekri, Faramarz

    2012-01-01

    The prospect of new biological and industrial applications that require communication in micro-scale, encourages research on the design of bio-compatible communication networks using networking primitives already available in nature. One of the most promising candidates for constructing such networks is to adapt and engineer specific types of bacteria that are capable of sensing, actuation, and above all, communication with each other. In this paper, we describe a new architecture for networks of bacteria to form a data collecting network, as in traditional sensor networks. The key to this architecture is the fact that the node in the network itself is a bacterial colony; as an individual bacterium (biological agent) is a tiny unreliable element with limited capabilities. We describe such a network under two different scenarios. We study the data gathering (sensing and multihop communication) scenario as in sensor networks followed by the consensus problem in a multi-node network. We will explain as to how th...

  3. Analysis on Relay Technology Application in Future Mobile Network%中继技术在未来移动网络中的应用分析

    Institute of Scientific and Technical Information of China (English)

    李国华

    2016-01-01

    Based on analysis of the use of the repeater in mobile communications network, the technical characteristics of various kinds of repeater, the requirement of relay in 4G and the relay technology used in 4G networks, the effective methods via traditional repeaters in combination with layer 3 RN were proposed to solve the problems caused by 4G layer 3 relay, such as inter-cell handover of the RN not being supported and an RN not using another RN as its DeNB in 4G. The research showed that the traditional repeaters would coexist with the layer 3 relay node in the future network.%通过分析传统直放站在移动通信网络中的应用状况及其各类直放站的技术特点、4G网络中继需求和4G中继技术,针对4G网络采用层3中继技术后出现的RN小区间不能切换、不能串联等问题,提出了借助传统直放站与层3中继节点相结合的有效解决方案。研究表明,传统直放站将与层3中继节点共存于未来网络。

  4. Pattern Switchable Antenna System Using Inkjet-Printed Directional Bow-Tie for Bi-Direction Sensing Applications

    OpenAIRE

    Seung-Hyun Eom; Yunsik Seo; Sungjoon Lim

    2015-01-01

    In this paper, we propose a paper-based pattern switchable antenna system using inkjet-printing technology for bi-direction sensor applications. The proposed antenna system is composed of two directional bow-tie antennas and a switching network. The switching network consists of a single-pole-double-throw (SPDT) switch and a balun element. A double-sided parallel-strip line (DSPSL) is employed to convert the unbalanced microstrip mode to the balanced strip mode. Two directional bow-tie antenn...

  5. NOA: A Network Operator Assistant for scheduling Tracking and Data Relay Satellite System (TDRSS)

    Science.gov (United States)

    Janssen, Terry; Berg, Richard A.; Das, Bikas K.

    1988-01-01

    Network Operator Assistant (NOA) is a prototype expert system. NOA uses detailed scheduling knowledge and problem solving heuristics to assist Network Control Center operators schedule the NASA Space Network in time critical situations. The current status of NOA and its future directions is presented.

  6. APLIKASI MIGRASI DATABASE DAN REPLIKASI BI-DIRECTIONAL

    Directory of Open Access Journals (Sweden)

    Michael Yoseph Ricky

    2011-11-01

    Full Text Available This study aims to analyze and design a migration and replication configurations in an enterprise using several methods such as literary study and direc survey to the company; analysis on hangar systems, process migration and replication as well as existing problems; and a prototype design for migration process implementated with Oracle SQL Developer and replication process implementated with Oracle GoldenGate. The study resluts ini a prototype for migration and replication configuration processes using Oracle's Golden Gate which can produce two sets of identical data for backup and recovery. Also a simple tool is designed to assist active-active replication process as well as active-passive one. The migration process from MySQL database to Oracle database using Oracle GoldenGate can not be done because GoldenGate Oracle has bugs related to the binary log, so database migration is done using Oracle SQL Developer. However, bi-directional replication between Oracle database using Oracle GoldenGate can ensure data availability and reduce the workload of primary database.

  7. Design of Bi-Directional Hydrofoils for Tidal Current Turbines

    Science.gov (United States)

    Nedyalkov, Ivaylo; Wosnik, Martin

    2015-11-01

    Tidal Current Turbines operate in flows which reverse direction. Bi-directional hydrofoils have rotational symmetry and allow such turbines to operate without the need for pitch or yaw control, decreasing the initial and maintenance costs. A numerical test-bed was developed to automate the simulations of hydrofoils in OpenFOAM and was utilized to simulate the flow over eleven classes of hydrofoils comprising a total of 700 foil shapes at different angles of attack. For promising candidate foil shapes physical models of 75 mm chord and 150 mm span were fabricated and tested in the University of New Hampshire High-Speed Cavitation Tunnel (HiCaT). The experimental results were compared to the simulations for model validation. The numerical test-bed successfully generated simulations for a wide range of foil shapes, although, as expected, the k - ω - SST turbulence model employed here was not adequate for some of the foils and for large angles of attack at which separation occurred. An optimization algorithm is currently being coupled with the numerical test-bed and additional turbulence models will be implemented in the future.

  8. Mobile Relay Configuration in Data-Intensuive Wireless Sensor with Three Routing Protocols to Mobile Nodes Networks

    Directory of Open Access Journals (Sweden)

    Mohamed Hafizuddin,

    2015-02-01

    Full Text Available Wireless sensor network are increasingly used in data-intensive applications such as micro-climate monitoring, precision agriculture and audio/video surveillance. A key challenges faced by data-intensive wsn’s is to transmit all the data generated with an application’s lifetime to the base station despite the fact that sensor nodes have limited power supply. We propose using low-cost disposable mobile really and our work in the following aspects First, it does not require complex motion planning of mobile nodes. Second we integrate the energy consumption due to both mobility and wireless transmission. Our framework consists of first algorithm computes an optimal routing tree. The second, we integrate the energy consumption due to both mobility and wireless transmissions .The second algorithm improves the topology of the routing tree by greedily adding new nodes. The third algorithm improves the routing tree by relocating its nodes without changing its topology. Frequently forming a network topology without the use of any existing network infrastructure. We compare the performance of the three prominent routing protocols for the mobile relay is Adhoc on Demand Distance Vector (ADVO, Destination Sequenced Distance Vector (DSDV and Temporally Ordered Routing Protocols (TORA. We have chosen four performance metrics such as Average Delay, Packet Delivery Fraction, Routing load and varying Mobility nodes, simulation for the popular routing protocols AODV, DSDV, and TORA. The simulation is carried out on NS-2. The performance differentials are analyzed using varying network size and simulations times. The simulation results confirm that ADVO performs well in terms of Average Delay, Packet Delivery Fraction. As far as routing load concers TORA performs well.

  9. 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.

  10. A chronic generalized bi-directional brain-machine interface

    Science.gov (United States)

    Rouse, A. G.; Stanslaski, S. R.; Cong, P.; Jensen, R. M.; Afshar, P.; Ullestad, D.; Gupta, R.; Molnar, G. F.; Moran, D. W.; Denison, T. J.

    2011-06-01

    A bi-directional neural interface (NI) system was designed and prototyped by incorporating a novel neural recording and processing subsystem into a commercial neural stimulator architecture. The NI system prototype leverages the system infrastructure from an existing neurostimulator to ensure reliable operation in a chronic implantation environment. In addition to providing predicate therapy capabilities, the device adds key elements to facilitate chronic research, such as four channels of electrocortigram/local field potential amplification and spectral analysis, a three-axis accelerometer, algorithm processing, event-based data logging, and wireless telemetry for data uploads and algorithm/configuration updates. The custom-integrated micropower sensor and interface circuits facilitate extended operation in a power-limited device. The prototype underwent significant verification testing to ensure reliability, and meets the requirements for a class CF instrument per IEC-60601 protocols. The ability of the device system to process and aid in classifying brain states was preclinically validated using an in vivo non-human primate model for brain control of a computer cursor (i.e. brain-machine interface or BMI). The primate BMI model was chosen for its ability to quantitatively measure signal decoding performance from brain activity that is similar in both amplitude and spectral content to other biomarkers used to detect disease states (e.g. Parkinson's disease). A key goal of this research prototype is to help broaden the clinical scope and acceptance of NI techniques, particularly real-time brain state detection. These techniques have the potential to be generalized beyond motor prosthesis, and are being explored for unmet needs in other neurological conditions such as movement disorders, stroke and epilepsy.

  11. NetCoDer: A Retransmission Mechanism for WSNs Based on Cooperative Relays and Network Coding.

    Science.gov (United States)

    Valle, Odilson T; Montez, Carlos; Medeiros de Araujo, Gustavo; Vasques, Francisco; Moraes, Ricardo

    2016-01-01

    Some of the most difficult problems to deal with when using Wireless Sensor Networks (WSNs) are related to the unreliable nature of communication channels. In this context, the use of cooperative diversity techniques and the application of network coding concepts may be promising solutions to improve the communication reliability. In this paper, we propose the NetCoDer scheme to address this problem. Its design is based on merging cooperative diversity techniques and network coding concepts. We evaluate the effectiveness of the NetCoDer scheme through both an experimental setup with real WSN nodes and a simulation assessment, comparing NetCoDer performance against state-of-the-art TDMA-based (Time Division Multiple Access) retransmission techniques: BlockACK, Master/Slave and Redundant TDMA. The obtained results highlight that the proposed NetCoDer scheme clearly improves the network performance when compared with other retransmission techniques. PMID:27258280

  12. NetCoDer: A Retransmission Mechanism for WSNs Based on Cooperative Relays and Network Coding

    Directory of Open Access Journals (Sweden)

    Odilson T. Valle

    2016-05-01

    Full Text Available Some of the most difficult problems to deal with when using Wireless Sensor Networks (WSNs are related to the unreliable nature of communication channels. In this context, the use of cooperative diversity techniques and the application of network coding concepts may be promising solutions to improve the communication reliability. In this paper, we propose the NetCoDer scheme to address this problem. Its design is based on merging cooperative diversity techniques and network coding concepts. We evaluate the effectiveness of the NetCoDer scheme through both an experimental setup with real WSN nodes and a simulation assessment, comparing NetCoDer performance against state-of-the-art TDMA-based (Time Division Multiple Access retransmission techniques: BlockACK, Master/Slave and Redundant TDMA. The obtained results highlight that the proposed NetCoDer scheme clearly improves the network performance when compared with other retransmission techniques.

  13. Achievable rate maximization for decode-and-forward MIMO-OFDM networks with an energy harvesting relay.

    Science.gov (United States)

    Du, Guanyao; Yu, Jianjun

    2016-01-01

    This paper investigates the system achievable rate for the multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system with an energy harvesting (EH) relay. Firstly we propose two protocols, time switching-based decode-and-forward relaying (TSDFR) and a flexible power splitting-based DF relaying (PSDFR) protocol by considering two practical receiver architectures, to enable the simultaneous information processing and energy harvesting at the relay. In PSDFR protocol, we introduce a temporal parameter to describe the time division pattern between the two phases which makes the protocol more flexible and general. In order to explore the system performance limit, we discuss the system achievable rate theoretically and formulate two optimization problems for the proposed protocols to maximize the system achievable rate. Since the problems are non-convex and difficult to solve, we first analyze them theoretically and get some explicit results, then design an augmented Lagrangian penalty function (ALPF) based algorithm for them. Numerical results are provided to validate the accuracy of our analytical results and the effectiveness of the proposed ALPF algorithm. It is shown that, PSDFR outperforms TSDFR to achieve higher achievable rate in such a MIMO-OFDM relaying system. Besides, we also investigate the impacts of the relay location, the number of antennas and the number of subcarriers on the system performance. Specifically, it is shown that, the relay position greatly affects the system performance of both protocols, and relatively worse achievable rate is achieved when the relay is placed in the middle of the source and the destination. This is different from the MIMO-OFDM DF relaying system without EH. Moreover, the optimal factor which indicates the time division pattern between the two phases in the PSDFR protocol is always above 0.8, which means that, the common division of the total transmission time into two equal phases in

  14. Eigen-Direction Alignment Based Physical-Layer Network Coding for MIMO Two-Way Relay Channels

    CERN Document Server

    Yang, Tao; Ping, Li; Collings, Iain B; Yuan, Jinhong

    2012-01-01

    In this paper, we propose a novel communication strategy which incorporates physical-layer network coding (PNC) into multiple-input multiple output (MIMO) two-way relay channels (TWRCs). At the heart of the proposed scheme lies a new key technique referred to as eigen-direction alignment (EDA) precoding. The EDA precoding efficiently aligns the two-user's eigen-modes into the same directions. Based on that, we carry out multi-stream PNC over the aligned eigen-modes. We derive an achievable rate of the proposed EDA-PNC scheme, based on nested lattice codes, over a MIMO TWRC. Asymptotic analysis shows that the proposed EDA-PNC scheme approaches the capacity upper bound as the number of user antennas increases towards infinity. For a finite number of user antennas, we formulate the design criterion of the optimal EDA precoder and present solutions. Numerical results show that there is only a marginal gap between the achievable rate of the proposed EDA-PNC scheme and the capacity upper bound of the MIMO TWRC, in ...

  15. 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.

  16. Relay-Linking Models for Prominence and Obsolescence in Evolving Networks

    CERN Document Server

    Singh, Mayank; Goyal, Pawan; Mukherjee, Animesh; Chakrabarti, Soumen

    2016-01-01

    The rate at which nodes in evolving social networks acquire links (friends, citations) shows complex temporal dynamics. Elegant and simple models, such as preferential attachment and link copying, model only rich-gets-richer effects, not aging and decline. Recent aging models are complex and heavily parameterized; most involve estimating 1-3 parameters per node. These parameters are intrinsic: they explain decline in terms of events in the past of the same node, and do not explain, using the network, where the linking attention might go instead. We argue that traditional network characterization, or even per-node linking dynamics, are insufficient to judge the faithfulness of models. We propose a new temporal sketch of an evolving graph, and introduce three new characterizations of a network's temporal dynamics. Then we propose a new family of frugal aging models with no per-node parameters and only 2-3 global parameters. Our model is based on a surprising inversion or undoing of triangle completion, where an...

  17. Dynamic subframe allocation for mobile broadband m-health using IEEE 802.16j mobile multihop relay networks.

    Science.gov (United States)

    Alinejad, Ali; Istepanian, R S H; Philip, N

    2012-01-01

    The concept of 4G health will be one of the key focus areas of future m-health research and enterprise activities in the coming years. WiMAX technology is one of the constituent 4G wireless technologies that provides broadband wireless access (BWA). Despite the fact that WiMAX is able to provide a high data rate in a relatively large coverage; this technology has specific limitations such as: coverage, signal attenuation problems due to shadowing or path loss, and limited available spectrum. The IEEE 802.16j mobile multihop relay (MMR) technology is a pragmatic solution designed to overcome these limitations. The aim of IEEE 802.16j MMR is to expand the IEEE 802.16e's capabilities with multihop features. In particular, the uplink (UL) and downlink (DL) subframe allocation in WiMAX network is usually fixed. However, dynamic frame allocation is a useful mechanism to optimize uplink and downlink subframe size dynamically based on the traffic conditions through real-time traffic monitoring. This particular mechanism is important for future WiMAX based m-health applications as it allows the tradeoff in both UL and DL channels. In this paper, we address the dynamic frame allocation issue in IEEE 802.16j MMR network for m-health applications. A comparative performance analysis of the proposed approach is validated using the OPNET Modeler(®). The simulation results have shown an improved performance of resource allocation and end-to-end delay performance for typical medical video streaming application.

  18. Dynamic subframe allocation for mobile broadband m-health using IEEE 802.16j mobile multihop relay networks.

    Science.gov (United States)

    Alinejad, Ali; Istepanian, R S H; Philip, N

    2012-01-01

    The concept of 4G health will be one of the key focus areas of future m-health research and enterprise activities in the coming years. WiMAX technology is one of the constituent 4G wireless technologies that provides broadband wireless access (BWA). Despite the fact that WiMAX is able to provide a high data rate in a relatively large coverage; this technology has specific limitations such as: coverage, signal attenuation problems due to shadowing or path loss, and limited available spectrum. The IEEE 802.16j mobile multihop relay (MMR) technology is a pragmatic solution designed to overcome these limitations. The aim of IEEE 802.16j MMR is to expand the IEEE 802.16e's capabilities with multihop features. In particular, the uplink (UL) and downlink (DL) subframe allocation in WiMAX network is usually fixed. However, dynamic frame allocation is a useful mechanism to optimize uplink and downlink subframe size dynamically based on the traffic conditions through real-time traffic monitoring. This particular mechanism is important for future WiMAX based m-health applications as it allows the tradeoff in both UL and DL channels. In this paper, we address the dynamic frame allocation issue in IEEE 802.16j MMR network for m-health applications. A comparative performance analysis of the proposed approach is validated using the OPNET Modeler(®). The simulation results have shown an improved performance of resource allocation and end-to-end delay performance for typical medical video streaming application. PMID:23365886

  19. Performance analysis of selective cooperation in amplify-and-forward relay networks over identical Nakagami-m channels

    KAUST Repository

    Hussain, Syed Imtiaz

    2011-05-02

    In cooperative communications, multiple relays between a source and a destination can increase the diversity gain. Because all the nodes must use orthogonal channels, multiple-relay cooperation becomes spectrally inefficient. Therefore, a bestrelay selection scheme was recently proposed. In this paper, we analyzed the performance of this scheme for a system with the relays operating in amplify-and-forward mode over identical Nakagami-m channels using an exact source-relay-destination signal-to-noise ratio (SNR).We derived accurate closed-form expressions for various system parameters including the probability density function of end-to-end SNR, the average output SNR, the bit error probability, and the channel capacity. The analytical results were verified through Monte Carlo simulations. Copyright © 2011 John Wiley & Sons, Ltd.

  20. Inferring bi-directional interactions between circadian clock genes and metabolism with model ensembles.

    Science.gov (United States)

    Grzegorczyk, Marco; Aderhold, Andrej; Husmeier, Dirk

    2015-04-01

    There has been much interest in reconstructing bi-directional regulatory networks linking the circadian clock to metabolism in plants. A variety of reverse engineering methods from machine learning and computational statistics have been proposed and evaluated. The emphasis of the present paper is on combining models in a model ensemble to boost the network reconstruction accuracy, and to explore various model combination strategies to maximize the improvement. Our results demonstrate that a rich ensemble of predictors outperforms the best individual model, even if the ensemble includes poor predictors with inferior individual reconstruction accuracy. For our application to metabolomic and transcriptomic time series from various mutagenesis plants grown in different light-dark cycles we also show how to determine the optimal time lag between interactions, and we identify significant interactions with a randomization test. Our study predicts new statistically significant interactions between circadian clock genes and metabolites in Arabidopsis thaliana, and thus provides independent statistical evidence that the regulation of metabolism by the circadian clock is not uni-directional, but that there is a statistically significant feedback mechanism aiming from metabolism back to the circadian clock. PMID:25719342

  1. Behavior of composite rigid frame bridge under bi-directional seismic excitations

    Directory of Open Access Journals (Sweden)

    Xiaogang Liu

    2014-02-01

    Full Text Available Pushover analysis and time history analysis are conducted to explore the bi-directional seismic behavior of composite steel-concrete rigid frame bridge, which is composed of RC piers and steel-concrete composite girders. Both longitudinal and transverse directions excitations are investigated using OpenSees. Firstly, the applicability of pushover analysis based on the fundamental mode is discussed. Secondly, an improved pushover analysis method considering the contribution of higher modes is proposed, and the applicability on composite rigid frame bridges under bi-directional earthquake is verified. Based on this method, an approach to predict the displacement responses of composite rigid frame bridge under random bi-directional seismic excitations by revising the elasto-plastic demand curve is also proposed. It is observed that the developed method yield a good estimate on the responses of composite rigid frame bridges under bi-directional seismic excitations.

  2. Relay Selection with Limited and Noisy Feedback

    KAUST Repository

    Eltayeb, Mohammed E.

    2016-01-28

    Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. Nonetheless, relay selection algorithms generally require error-free channel state information (CSI) from all cooperating relays. Practically, CSI acquisition generates a great deal of feedback overhead that could result in significant transmission delays. In addition to this, 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 propose a relay selection algorithm that tackles the above challenges. Instead of allocating each relay a dedicated channel for feedback, all relays share a pool of feedback channels. Following that, each relay feeds back its identity only if its effective channel (source-relay-destination) exceeds a threshold. After deriving closed-form expressions for the feedback load and the achievable rate, we show that the proposed algorithm drastically reduces the feedback overhead and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback from all relays. © 2015 IEEE.

  3. Bi-directional light transmission properties assessment for venetian blinds : Computer simulations compared to photogoniometer measurements

    OpenAIRE

    Andersen, Marilyne; Scartezzini, J.-L.; Rubin, M. D.; Powles, R. C.

    2003-01-01

    An accurate evaluation of daylight distribution through advanced fenestration systems (complex glazing, solar shading systems) requires the knowledge of their Bi-directional light Transmission Distribution Function (BTDF). An innovative equipment for the experimental assessment of these bi-directional functions has been developed, based on a digital imaging detection system. An extensive set of BTDF measurements was performed with this photogoniometer on venetian blinds presenting curved slat...

  4. Opportunistic Relay Selection With Limited Feedback

    KAUST Repository

    Eltayeb, Mohammed E.

    2015-08-01

    Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. Generally, relay selection algorithms require channel state information (CSI) feedback from all cooperating relays to make a selection decision. This requirement poses two important challenges, which are often neglected in the literature. Firstly, the fed back channel information is usually corrupted by additive noise. Secondly, CSI feedback generates a great deal of feedback overhead (air-time) that could result in significant performance hits. In this paper, we propose a compressive sensing (CS) based relay selection algorithm that reduces the feedback overhead of relay networks under the assumption of noisy feedback channels. The proposed algorithm exploits CS to first obtain the identity of a set of relays with favorable channel conditions. Following that, the CSI of the identified relays is estimated using least squares estimation without any additional feedback. Both single and multiple relay selection cases are considered. After deriving closed-form expressions for the asymptotic end-to-end SNR at the destination and the feedback load for different relaying protocols, we show that CS-based selection drastically reduces the feedback load and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback. © 1972-2012 IEEE.

  5. Activation and Inhibition of Posterior Parietal Cortex Have Bi-Directional Effects on Spatial Errors Following Interruptions

    Directory of Open Access Journals (Sweden)

    Cyrus Khan Foroughi

    2015-01-01

    Full Text Available Interruptions to ongoing mental activities are omnipresent in our modern digital world, but the brain networks involved in interrupted performance are not known, nor have the activation of those networks been modulated. Errors following interruptions reflect failures in spatial memory, whose maintenance is supported by a brain network including the right posterior parietal cortex (PPC. The present study therefore used bi-directional transcranial Direct Current Stimulation (tDCS of right PPC to examine the neuromodulation of spatial errors following interruptions, as well as performance on another PPC-dependent task, mental rotation. Anodal stimulation significantly reduced the number of interruption-based errors and increased mental rotation accuracy whereas cathodal stimulation significantly increased errors and reduced mental rotation accuracy. The results provide evidence for a causal role of the PPC in the maintenance of spatial representations during interrupted task performance.

  6. Upgrade of a transverse ventilation system in a bi-directional tunnel

    Directory of Open Access Journals (Sweden)

    Vidmar Peter

    2012-01-01

    Full Text Available The Karavanke tunnel forms an important link between Slovenia and Austria. The almost 8 km long tunnel is operated with bi-directional traffic and does not have dedicated escape routes. Moreover, the ventilation in case of fire does not satisfy requirements of the EU Directive 2004/54/EC that specifies the minimum requirements for tunnels in the trans-European road network. The paper present results of the research conducted regarding the possibility of upgrade the existing system in order to reach the required level of safety at lower costs possible. It is shown that with simple but novel adaptations of the ventilation system, a sizeable increase in the overall level of safety can be achieved. The methodology applied is a combination of a simple pipe model for tunnel ventilation and for detailed fluid dynamics analysis the CFD model is used. The existing ventilation system that in fire ventilation extracts smoke from a single duct is replaced with the smoke extraction from both ducts applying four axial fans. The analysis is focused on air/smoke flow through the vents and ducts and on pressure drops calculated over the length of the ventilation duct and its influence on the total flow. The change of the flow condition also has influence on ventilation fan operation point that is investigated in the paper as well.

  7. Performance analysis of relay-assisted all-optical FSO networks over strong atmospheric turbulence channels with pointing errors

    KAUST Repository

    Yang, Liang

    2014-12-01

    In this study, we consider a relay-assisted free-space optical communication scheme over strong atmospheric turbulence channels with misalignment-induced pointing errors. The links from the source to the destination are assumed to be all-optical links. Assuming a variable gain relay with amplify-and-forward protocol, the electrical signal at the source is forwarded to the destination with the help of this relay through all-optical links. More specifically, we first present a cumulative density function (CDF) analysis for the end-to-end signal-to-noise ratio. Based on this CDF, the outage probability, bit-error rate, and average capacity of our proposed system are derived. Results show that the system diversity order is related to the minimum value of the channel parameters.

  8. Applying a Space-Based Security Recovery Scheme for Critical Homeland Security Cyberinfrastructure Utilizing the NASA Tracking and Data Relay (TDRS) Based Space Network

    Science.gov (United States)

    Shaw, Harry C.; McLaughlin, Brian; Stocklin, Frank; Fortin, Andre; Israel, David; Dissanayake, Asoka; Gilliand, Denise; LaFontaine, Richard; Broomandan, Richard; Hyunh, Nancy

    2015-01-01

    Protection of the national infrastructure is a high priority for cybersecurity of the homeland. Critical infrastructure such as the national power grid, commercial financial networks, and communications networks have been successfully invaded and re-invaded from foreign and domestic attackers. The ability to re-establish authentication and confidentiality of the network participants via secure channels that have not been compromised would be an important countermeasure to compromise of our critical network infrastructure. This paper describes a concept of operations by which the NASA Tracking and Data Relay (TDRS) constellation of spacecraft in conjunction with the White Sands Complex (WSC) Ground Station host a security recovery system for re-establishing secure network communications in the event of a national or regional cyberattack. Users would perform security and network restoral functions via a Broadcast Satellite Service (BSS) from the TDRS constellation. The BSS enrollment only requires that each network location have a receive antenna and satellite receiver. This would be no more complex than setting up a DIRECTTV-like receiver at each network location with separate network connectivity. A GEO BSS would allow a mass re-enrollment of network nodes (up to nationwide) simultaneously depending upon downlink characteristics. This paper details the spectrum requirements, link budget, notional assets and communications requirements for the scheme. It describes the architecture of such a system and the manner in which it leverages off of the existing secure infrastructure which is already in place and managed by the NASAGSFC Space Network Project.

  9. Channel estimation for physical layer network coding systems

    CERN Document Server

    Gao, Feifei; Wang, Gongpu

    2014-01-01

    This SpringerBrief presents channel estimation strategies for the physical later network coding (PLNC) systems. Along with a review of PLNC architectures, this brief examines new challenges brought by the special structure of bi-directional two-hop transmissions that are different from the traditional point-to-point systems and unidirectional relay systems. The authors discuss the channel estimation strategies over typical fading scenarios, including frequency flat fading, frequency selective fading and time selective fading, as well as future research directions. Chapters explore the performa

  10. A high-damping magnetorheological elastomer with bi-directional magnetic-control modulus for potential application in seismology

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Miao, E-mail: yumiao@cqu.edu.cn; Qi, Song; Fu, Jie; Zhu, Mi [Key Lab for Optoelectronic Technology and Systems, Ministry of Education, College of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China)

    2015-09-14

    A high-damping magnetorheological elastomer (MRE) with bi-directional magnetic-control modulus is developed. This MRE was synthesized by filling NdFeB particles into polyurethane (PU)/ epoxy (EP) interpenetrating network (IPN) structure. The anisotropic samples were prepared in a permanent magnetic field and magnetized in an electromagnetic field of 1 T. Dynamic mechanical responses of the MRE to applied magnetic fields are investigated through magneto-rheometer, and morphology of MREs is observed via scanning electron microscope (SEM). Test result indicates that when the test field orientation is parallel to that of the sample's magnetization, the shear modulus of sample increases. On the other hand, when the orientation is opposite to that of the sample's magnetization, shear modulus decreases. In addition, this PU/EP IPN matrix based MRE has a high-damping property, with high loss factor and can be controlled by applying magnetic field. It is expected that the high damping property and the ability of bi-directional magnetic-control modulus of this MRE offer promising advantages in seismologic application.

  11. On the achievable degrees of freedom of alternate MIMO relaying with multiple AF relays

    KAUST Repository

    Park, Kihong

    2012-03-01

    In this paper, we consider a two-hop relaying network where one source, one destination, and multiple amplify-and-forward (AF) relays equipped with M antennas operate in a half-duplex mode. In order to compensate for the inherent loss of capacity pre-log factor of 1/2 due to half-duplex relaying, we propose a new transmission protocol which combines alternate relaying and inter-relay interference alignment. We prove that the proposed scheme can (i) exploits M degrees of freedom (DOFs) and (ii) perfectly recover the pre-log factor loss if the number of relays is at least six. From our selected numerical results, we show that our proposed scheme gives significant improvement over conventional AF relaying which offers only M/2 DOFs. © 2012 IEEE.

  12. Ground wave emergency network final operational capability. Environmental assessment for southern Arkansas relay node site no. RN 8C912AR

    Science.gov (United States)

    1993-02-01

    The Ground Wave Emergency Network (GWEN) is a radio communication system designed to relay emergency messages between strategic military areas in the continental United States. The system is immune to the effects of high-attitude electromagnetic pulse (HEMP) energy surges caused by nuclear bursts in the ionosphere that would disrupt conventional communications equipment such as telephones and shortwave radios. A failure of such equipment would prevent timely communications among top military and civilian leaders and strategic Air Force locations and prevent U.S. assessment and retaliation during an attack. GWEN is an essential part of a defense modernization program to upgrade and improve our nation's communications system, thereby strengthening deterrence.

  13. Pattern Switchable Antenna System Using Inkjet-Printed Directional Bow-Tie for Bi-Direction Sensing Applications.

    Science.gov (United States)

    Eom, Seung-Hyun; Seo, Yunsik; Lim, Sungjoon

    2015-01-01

    In this paper, we propose a paper-based pattern switchable antenna system using inkjet-printing technology for bi-direction sensor applications. The proposed antenna system is composed of two directional bow-tie antennas and a switching network. The switching network consists of a single-pole-double-throw (SPDT) switch and a balun element. A double-sided parallel-strip line (DSPSL) is employed to convert the unbalanced microstrip mode to the balanced strip mode. Two directional bow-tie antennas have different radiation patterns because of the different orientation of the reflectors and antennas. It is demonstrated from electromagnetic (EM) simulation and measurement that the radiation patterns of the proposed antenna are successfully switched by the SPDT switch. PMID:26690443

  14. Pattern Switchable Antenna System Using Inkjet-Printed Directional Bow-Tie for Bi-Direction Sensing Applications

    Directory of Open Access Journals (Sweden)

    Seung-Hyun Eom

    2015-12-01

    Full Text Available In this paper, we propose a paper-based pattern switchable antenna system using inkjet-printing technology for bi-direction sensor applications. The proposed antenna system is composed of two directional bow-tie antennas and a switching network. The switching network consists of a single-pole-double-throw (SPDT switch and a balun element. A double-sided parallel-strip line (DSPSL is employed to convert the unbalanced microstrip mode to the balanced strip mode. Two directional bow-tie antennas have different radiation patterns because of the different orientation of the reflectors and antennas. It is demonstrated from electromagnetic (EM simulation and measurement that the radiation patterns of the proposed antenna are successfully switched by the SPDT switch.

  15. Buffer-Aided Relaying with Adaptive Link Selection

    DEFF Research Database (Denmark)

    Zlatanov, Nikola; Schober, Robert; Popovski, Petar

    2013-01-01

    In this paper, we consider a simple network consisting of a source, a half-duplex decode-and-forward relay, and a destination. We propose a new relaying protocol employing adaptive link selection, i.e., in any given time slot, based on the channel state information of the source-relay and the relay-destination...... link a decision is made whether the source or the relay transmits. In order to avoid data loss at the relay, adaptive link selection requires the relay to be equipped with a buffer such that data can be queued until the relay-destination link is selected for transmission. We study both delay......-constrained and delay-unconstrained transmission. For the delay-unconstrained case, we characterize the optimal link selection policy, derive the corresponding throughput, and develop an optimal power allocation scheme. For the delay-constrained case, we propose to starve the buffer of the relay by choosing...

  16. Relay race

    CERN Document Server

    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...

  17. A NEW RELAY DESIGN FOR REACTIVE POWER COMPENSATION AND ECONOMICAL COMPARISION WITH CLASSICAL RELAY

    Directory of Open Access Journals (Sweden)

    Mustafa ŞEKKELİ

    2007-02-01

    Full Text Available In most cases, reactive power compensation is otomatically achieved with reactive power control relay by switching on and off, stationary shunt capasitors to the electrical network. İn this study , a new relay has been designed and developed. İn this method, capasitors which is switched on and of are optimally choosen. İn classical relay , only one capasitor can be added or extructed to the network. But,in designing new relay, 1,2 or 3 capasitor banks which are nearest value for desired inductive reactive power can be optimally choosen. As a result , switching number of capacitor and contactor is reduced minimum value and line is loaded less inductive current , it means that less active power losses. New designed relay has been compared with classical one economically . This relay has been manufactured and approved experimantally.

  18. Bi-directional magnetic resonance based wireless power transfer for electronic devices

    Science.gov (United States)

    Kar, Durga P.; Nayak, Praveen P.; Bhuyan, Satyanarayan; Mishra, Debasish

    2015-09-01

    In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency.

  19. Bi-directional magnetic resonance based wireless power transfer for electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Kar, Durga P.; Nayak, Praveen P.; Bhuyan, Satyanarayan; Mishra, Debasish [Department of Electronics and Instrumentation Engineering, Institute of Technical Education and Research, Siksha ‘O’ Anushandhan University, Bhubaneswar 751030 (India)

    2015-09-28

    In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency.

  20. Detection of Bi-Directionality in Strain-Gage Balance Calibration Data

    Science.gov (United States)

    Ulbrich, Norbert

    2012-01-01

    An indicator variable was developed for both visualization and detection of bi-directionality in wind tunnel strain-gage balance calibration data. First, the calculation of the indicator variable is explained in detail. Then, a criterion is discussed that may be used to decide which gage outputs of a balance have bi- directional behavior. The result of this analysis could be used, for example, to justify the selection of certain absolute value or other even function terms in the regression model of gage outputs whenever the Iterative Method is chosen for the balance calibration data analysis. Calibration data of NASA s MK40 Task balance is analyzed to illustrate both the calculation of the indicator variable and the application of the proposed criterion. Finally, bi directionality characteristics of typical multi piece, hybrid, single piece, and semispan balances are determined and discussed.

  1. Bi-directional magnetic resonance based wireless power transfer for electronic devices

    International Nuclear Information System (INIS)

    In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency

  2. Upper-Bounding the Capacity of Relay Communications - Part I

    OpenAIRE

    Shams, Farshad; Luise, Marco

    2013-01-01

    This paper focuses on the capacity of point-to-point relay communications wherein the transmitter is assisted by an intermediate relay. We detail the mathematical model of cutset and amplify and forward (AF) relaying strategy. We present the upper bound capacity of each relaying strategy from information theory viewpoint and also in networks with Gaussian channels. We exemplify various outer region capacities of the addressed strategies with two different case studies. The results exhibit tha...

  3. Bi-directional WDM transmission by use of SOAs as inline amplifiers without isolators

    DEFF Research Database (Denmark)

    Jeppesen, Palle; Yu, Jianjun

    2001-01-01

    Error-free bi-directional transmission of 8×10 Gb/s signals over two inline SOAs is realized for the first time. It is demonstrated that SOAs can be used for inline amplifiers in bidirectional multi-wavelength transmission systems at 10 Gb/s without any isolator.......Error-free bi-directional transmission of 8×10 Gb/s signals over two inline SOAs is realized for the first time. It is demonstrated that SOAs can be used for inline amplifiers in bidirectional multi-wavelength transmission systems at 10 Gb/s without any isolator....

  4. Transducer-type bi-directional linear ultrasonic motor and experiment

    Institute of Scientific and Technical Information of China (English)

    CHU Xiangcheng; CHEN Zaili

    2002-01-01

    A transducer-type bi-directional linear ultrasonic notor is presented. It has the features of flexible bi-directional drive, simple construction and easy control, etc. The characteristics parameters of the prototype are: frequency 21.46 kHz, maximum moving speed 400 mm/s under pre-load of 3.2 N, maximum thrust 2.1 N under pre-load of 1.6 N. The influence of phase shift and vibration amplitude of ultrasonic transducers on ideal elliptical locus and output characteristics are investigated with theoretical and experimental methods.

  5. Model of Bi-directional Flyback Converter for Hybrid AC/DC Distribution System

    OpenAIRE

    Riku Pasonen

    2013-01-01

    In this article, a simulation model and concept of two switch bi-directional isolated DC/DC converter is presented. Converter is based on flyback converter type. Also control method for voltage regulation with bi-directional power transfer is presented. Target application of the proposed converter was selected to be a hybrid AC/DC distribution system concept of which was briefly described. The requirement of galvanic isolation in the hybrid AC/DC concept comes from use of shared neutral wire;...

  6. Evaluating on Performance of Single-source Single-relay Sr-carq protocol in Tdma Networks with Raleigh Fading

    Directory of Open Access Journals (Sweden)

    Yongqiang Zhou

    2012-09-01

    Full Text Available This paper analyzes the performance of single-source and single-relay SR-CARQ protocol in TDMA wireless communication system. We establish its M/G/1 queuing model with vacations, and provide the expressions of its system time delay and saturation throughput. Then the analysis of theory and simulation results under the slow Raleigh fading channel show that under what conditions the SR-CARQ protocol is superior to its non-cooperative counterpart.

  7. 基于网络编码的无线体域网多中继协作节能策略%A Multi-relay Cooperative Energy-saving Strategy Based on Network Coding in Wireless Body Area Networks

    Institute of Scientific and Technical Information of China (English)

    闫龙; 覃团发; 李亮亮; 蒙云番; 邢杰

    2014-01-01

    Network coding is introduced to multi-source-multi-relay systems to solve the extra energy con-sumption problem caused by transmission link outage in wireless body area networks ( WBAN ) , and a multi-relay cooperative algorithm based on network coding is proposed to analyze the system’s network en-ergy consumption as well. Then an overall-energy-consumption-per-bit formula is derived according to the analysis result of the proposed algorithm. The simulation results show that the proposed algorithm can largely reduce the network’s overall energy consumption compared with the traditional multi-path-multi-relay transmission algorithm. Increasing the number of source nodes or decreasing the number of relay nodes can also help lower the overall energy consumption. The proposed algorithm can reduce the overall energy consumption of multi-source-multi-relay networks and extend the network lifetime.%针对无线体域网中传输链路存在中断情况从而消耗额外能量的问题,在多源多中继系统模型中引入网络编码,提出一种基于网络编码多中继协作算法,并分析了该算法下系统的网络能耗,推导出系统的每比特网络整体能耗公式。仿真结果表明:该算法与传统的多路径多中继转发算法相比,可以较大程度的减少网络的整体能耗,适当地增加信源节点或者减少中继节点的数目对降低网络的整体能耗也有一定的作用。该算法能减少多源多中继网络的整体能耗,延长网络的生命周期。

  8. Reliability analysis of an LCL tuned track segmented bi-directional inductive power transfer system

    DEFF Research Database (Denmark)

    Asif Iqbal, S. M.; Madawala, U. K.; Thrimawithana, D. J.;

    2013-01-01

    Bi-directional Inductive Power Transfer (BDIPT) technique is suitable for renewable energy based applications such as electric vehicles (EVs), for the implementation of vehicle-to-grid (V2G) systems. Recently, more efforts have been made by researchers to improve both efficiency and reliability o...

  9. Anxiety and Reading Difficulties in Early Elementary School: Evidence for Unidirectional- or Bi-Directional Relations?

    Science.gov (United States)

    Grills-Taquechel, Amie E.; Fletcher, Jack M.; Vaughn, Sharon R.; Stuebing, Karla K.

    2012-01-01

    The present study examined competing models of the bi-directional influences of anxiety and reading achievement. Participants were 153 ethnically-diverse children (84 male, 69 female) from general education classes evaluated in the winter and spring of their first-grade academic year. Children completed standardized measures of reading achievement…

  10. Longitudinal Bi-Directional Relationships between Sleep and Youth Substance Use

    Science.gov (United States)

    Pasch, Keryn E.; Latimer, Lara A.; Cance, Jessica Duncan; Moe, Stacey G.; Lytle, Leslie A.

    2012-01-01

    Despite the known deficits in sleep that occur during adolescence and the high prevalence of substance use behaviors among this group, relatively little research has explored how sleep and substance use may be causally related. The purpose of this study was to explore the longitudinal bi-directional relationships between sleep duration, sleep…

  11. High Efficiency Interleaved Bi-Directional ZVS DC-DC Converter

    DEFF Research Database (Denmark)

    Zafar Ullah Khan, M.; Mohsin Naveed, M.; Hussain, Dil Muhammad Akbar

    2013-01-01

    A High Efficiency Interleaved Bi-Directional ZVS DC-DC converter is presented in this paper. This converter can be operated in both buck and boost mode. CoolMOS is used as a power device to achieve low conduction losses and fast turn off. The value of inductance is selected such that the Cool...

  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. High Speed Internet Access And Network Frame Relay Technology%高速网络的访问与联网帧中继技术

    Institute of Scientific and Technical Information of China (English)

    周振波

    2014-01-01

    帧中继是ANSI和CCITT制订的协议,在用户端设备和将数据发送到远程CPE的广域网之间提供了接口。和传统的分组交换技术相比是效率很高的广域通信技术,同电路交换相比帧中继能够为Internet访问和其他LAN互连的突发性通信量在成本和性能方面提供很大的帮助。%The frame relay ANSI and CCITT formulation of the agreement, in the user terminal equipment and sends the data to the remote CPE wide area network provides interface. And the traditional packet switching technology is a wide area communi-cation efficiency is very high, compared with circuit switching frame relay can provide great help for bursty traffic Internet access and other LAN interconnection in terms of cost and performance.

  14. Distributed Antenna Channels with Regenerative Relaying: Relay Selection and Asymptotic Capacity

    Directory of Open Access Journals (Sweden)

    Aitor del Coso

    2007-11-01

    Full Text Available Multiple-input-multiple-output (MIMO techniques have been widely proposed as a means to improve capacity and reliability of wireless channels, and have become the most promising technology for next generation networks. However, their practical deployment in current wireless devices is severely affected by antenna correlation, which reduces their impact on performance. One approach to solve this limitation is relaying diversity. In relay channels, a set of N wireless nodes aids a source-destination communication by relaying the source data, thus creating a distributed antenna array with uncorrelated path gains. In this paper, we study this multiple relay channel (MRC following a decode-and-forward (D&F strategy (i.e., regenerative forwarding, and derive its achievable rate under AWGN. A half-duplex constraint on relays is assumed, as well as distributed channel knowledge at both transmitter and receiver sides of the communication. For this channel, we obtain the optimum relay selection algorithm and the optimum power allocation within the network so that the transmission rate is maximized. Likewise, we bound the ergodic performance of the achievable rate and derive its asymptotic behavior in the number of relays. Results show that the achievable rate of regenerative MRC grows as the logarithm of the Lambert W function of the total number of relays, that is, 𝒞=log⁡2(W0(N. Therefore, D&F relaying, cannot achieve the capacity of actual MISO channels.

  15. Distributed Antenna Channels with Regenerative Relaying: Relay Selection and Asymptotic Capacity

    Directory of Open Access Journals (Sweden)

    del Coso Aitor

    2007-01-01

    Full Text Available Multiple-input-multiple-output (MIMO techniques have been widely proposed as a means to improve capacity and reliability of wireless channels, and have become the most promising technology for next generation networks. However, their practical deployment in current wireless devices is severely affected by antenna correlation, which reduces their impact on performance. One approach to solve this limitation is relaying diversity. In relay channels, a set of wireless nodes aids a source-destination communication by relaying the source data, thus creating a distributed antenna array with uncorrelated path gains. In this paper, we study this multiple relay channel (MRC following a decode-and-forward (D&F strategy (i.e., regenerative forwarding, and derive its achievable rate under AWGN. A half-duplex constraint on relays is assumed, as well as distributed channel knowledge at both transmitter and receiver sides of the communication. For this channel, we obtain the optimum relay selection algorithm and the optimum power allocation within the network so that the transmission rate is maximized. Likewise, we bound the ergodic performance of the achievable rate and derive its asymptotic behavior in the number of relays. Results show that the achievable rate of regenerative MRC grows as the logarithm of the Lambert W function of the total number of relays, that is, . Therefore, D&F relaying, cannot achieve the capacity of actual MISO channels.

  16. 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.

  17. 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.

  18. 80537 based distance relay

    DEFF Research Database (Denmark)

    Pedersen, Knud Ole Helgesen

    1999-01-01

    A method for implementing a digital distance relay in the power system is described.Instructions are given on how to program this relay on a 80537 based microcomputer system.The problem is used as a practical case study in the course 53113: Micocomputer applications in the power system.The relay...

  19. Robust distributed cognitive relay beamforming

    KAUST Repository

    Pandarakkottilil, Ubaidulla

    2012-05-01

    In this paper, we present a distributed relay beamformer design for a cognitive radio network in which a cognitive (or secondary) transmit node communicates with a secondary receive node assisted by a set of cognitive non-regenerative relays. The secondary nodes share the spectrum with a licensed primary user (PU) node, and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. The proposed robust cognitive relay beamformer design seeks to minimize the total relay transmit power while ensuring that the transceiver signal-to-interference- plus-noise ratio and PU interference constraints are satisfied. The proposed design takes into account a parameter of the error in the channel state information (CSI) to render the performance of the beamformer robust in the presence of imperfect CSI. Though the original problem is non-convex, we show that the proposed design can be reformulated as a tractable convex optimization problem that can be solved efficiently. Numerical results are provided and illustrate the performance of the proposed designs for different network operating conditions and parameters. © 2012 IEEE.

  20. Opportunistic Fixed Gain Bidirectional Relaying with Outdated CSI

    KAUST Repository

    Khan, Fahd Ahmed

    2015-05-01

    In a network with multiple relays, relay selection has been shown as an effective scheme to achieve diversity as well as to improve the overall throughput. This paper studies the impact of using outdated channel state information for relay selection on the performance of a network where two sources communicate with each other via fixed-gain amplify-and-forward relays. For a Rayleigh faded channel, closed-form expressions for the outage probability, moment generating function and symbol error rate are derived. Simulations results are also presented to corroborate the derived analytical results. It is shown that adding relays does not improve the performance if the channel is substantially outdated. Furthermore, relay location is also taken into consideration and it is shown that the performance can be improved by placing the relay closer to the source whose channel is more outdated. © 2015 IEEE.

  1. Optimised secure transmission through untrusted AF relays using link adaptation

    Science.gov (United States)

    Taki, Mehrdad; Sadeghi, Mohammad

    2016-05-01

    A new transmission scheme is presented for a two-hop relay network including two AF relays, considering physical layer security where relays are not able to detect signal with an acceptable bit error rate (BER) but the combined received signal is detected with an acceptable BER at the final receiver. It is assumed that there is no direct path between the transmitter and the receiver (relay network without diversity). Adaptive modulation and coding is utilised at the transmitter and transmission powers of the transmitter and of the relays are continuously adapted provisioning individual average power constraint for each node. Numerical evaluations show that an acceptable performance degradation is seen by the proposed secure relaying scheme compared to the optimum relay selection scheme without security constraint.

  2. Opportunistic Relay Selection with Cooperative Macro Diversity

    Directory of Open Access Journals (Sweden)

    Yu Chia-Hao

    2010-01-01

    Full Text Available We apply a fully opportunistic relay selection scheme to study cooperative diversity in a semianalytical manner. In our framework, idle Mobile Stations (MSs are capable of being used as Relay Stations (RSs and no relaying is required if the direct path is strong. Our relay selection scheme is fully selection based: either the direct path or one of the relaying paths is selected. Macro diversity, which is often ignored in analytical works, is taken into account together with micro diversity by using a complete channel model that includes both shadow fading and fast fading effects. The stochastic geometry of the network is taken into account by having a random number of randomly located MSs. The outage probability analysis of the selection differs from the case where only fast fading is considered. Under our framework, distribution of the received power is formulated using different Channel State Information (CSI assumptions to simulate both optimistic and practical environments. The results show that the relay selection gain can be significant given a suitable amount of candidate RSs. Also, while relay selection according to incomplete CSI is diversity suboptimal compared to relay selection based on full CSI, the loss in average throughput is not too significant. This is a consequence of the dominance of geometry over fast fading.

  3. Auction Based Relay Selection and Power Controlling Scheme in Cooperative Relay Network%协作中继网络中基于拍卖的中继选择和功率控制策略

    Institute of Scientific and Technical Information of China (English)

    胡洁; 赵祚喜; 卢丹松

    2013-01-01

    A distributed relay selection and power controlling scheme ARSPC was proposed in the wireless environment of multi-source and multi-relay. ARSPC scheme modeled the relationship of user and relay nodes as a multi-buyer multi-seller auction, and realized the relay selection and relay power controlling by ascending auction. Both theory analysis and simulation results prove ARSPC can converge to pareto efficient result under conditions of a basic price increment which is small enough.%在多源多中继无线网络环境下,提出了实现中继选择和功率控制的分布式算法ARSPC.ARSPC算法将用户和中继节点的关系建模为多买家多卖家的拍卖模型,通过加价式拍卖分布式实现了用户对中继的选择和中继发送功率的控制.理论证明和仿真结果都验证了在基本价格增量足够小的条件下,ARSPC算法收敛的结果是帕累托最优.

  4. Fundamental Relations Between Reactive and Proactive Relay-Selection Strategies

    OpenAIRE

    Xia, Minghua; AÏSSA, Sonia

    2015-01-01

    Two major relay-selection strategies widely applied in cooperative decode-and-forward (DF) relaying networks, namely, reactive relay selection (RRS) and proactive relay selection (PRS), are generally looked upon as independent and studied separately. In this paper, RRS and PRS are proven to be equivalent with respect to the end-to-end outage probability from the first principle, i.e. their respective relay-selection criteria. On the other hand, RRS is shown to be superior to PRS with respect ...

  5. Distributed opportunistic channel access strategy in DF relay networks%DF中继网络中的分布式机会信道接入策略

    Institute of Scientific and Technical Information of China (English)

    董蕾; 王勇超

    2016-01-01

    Considering the two limitations of scenario assumption and performance optimization in distributed opportunistic channel access under the continuous transmission rate, a distributed opportunistic channel access strategy is proposed in DF relay networks under the discrete transmission rate. The proposed strategy maximizes the system average throughput with the instruction of optimal stopping theory. By optimizing the second-hop transmission time in DF relay networks completely, the total transmission time is reduced, and the system performance is improved. Compared with the current strategy, simulation result demonstrates the validity of the proposed strategy in system average throughput.%针对连续传输速率下分布式机会信道接入场景设定与性能优化受限的问题,提出了离散传输速率下译码转发中继网络中的分布式机会信道接入策略.该策略在最优停止理论的指导下,将最大化系统平均吞吐率作为优化目标,通过对译码转发中继网络中的第2跳传输时间进行完全优化,使总体的传输时间大幅度减小,系统性能得到显著提高.仿真结果表明,相较现有策略,文中所提策略在系统平均吞吐率上具有明显优势.

  6. Tissue Microarray Study of Vasculogenic Mimicry in Bi-directional Differentiated Malignant Tumors

    Institute of Scientific and Technical Information of China (English)

    XishanHao; BaocunSun; ShiwuZhang; XiulanZhao

    2004-01-01

    OBJECTIVE To determine if vasculogenic mimicry (VM) exists in bi-directional differentiated malignant tumors. METHODS The blood supply models for bi-directional differentiated tumors were studied with immunohistochemical and PAS double-staining techniques. New sections were made from 158 paraffin-embedded bi-directional malignant-tumor samples, including melanoma (high malignancy n=30, low malignancy n=30); synoviosarcoma(SS) (high malignancy n=26, low malignancy n=13); acinar rhabdomyosarcoma (All) (high malignancy n=16,low malignancy n=13); malignant mesothelioma (MM) (n=26), and epithelioid sarcoma (ES)(n=4). Tissue microarrays were made. The representative points in the paraffin sections were labeled and two tissue microarrays were made, one included 60 cases of melanoma, and the other included the other tumors. Immunohistochemical staining of the platelet-endothelial cell adhesive molecule(CD31 antigen) and periodic acid Schiff(PAS) staining were conducted. The areas were calculated of vessel-like channels consisting of CD31 antigen-positive tumor cells and of PAS positive materials. The VM was studied using the data obtained. RESULTS Some of these bi-directional tumor cells secreted PAS-positive materials and 0D31 positive materials. The walls of the VM consisted of PAS-positive materials lined with CD31 negative tumor cells with red blood cells inside the channel, whereas the walls of the epithelium-dependent vessels were comprised of CD31 positive materials. The positive areas of CD31 were significantly less than that of PAS (P<0.01). The number of cases with VM in highly malignant tumors was greater than that found in the lowly malignant tumors. CONCLUSIONS Bi-directional differentiated malignant tumor cells have the ability to auto-transform and might interact with the extracellular matrix to form a vessel channel system which mimics blood vessels for transporting blood. That process is called VM. Results in this study show that bi-directional

  7. Identification of a bi-directional promoter from Tomato yellow leaf curl China virus

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A bi-directional promoter of Tomato yellow leaf curl China virus (TYLCCNV) was obtained with the total DNA from TYLCCNV isolate Y10 infected tobacco leaves as a template. Plant expression vectors were constructed by fusing the amplified DNA fragment with the gus gene and nopaline terminator in different orientations. The vectors containing promoter fragments were transferred into leaf cells and plant stems of Nicotiana benthamiana by Agrobacterium-mediated method. Transient expression results showed that both the complementary and virion-sense promoters could drive the gus gene to express, and the GUS activity of the complementary-sense promoter was stronger than that of the virion-sense. Co-expression of the vector containing βC1 gene of TYLCCNV DNAβ with the vector containing a bi-directional promoter revealed that the βC1 protein has no impact on expression of either the virion- or the complementarysense promoter.

  8. Model of Bi-directional Flyback Converter for Hybrid AC/DC Distribution System

    Directory of Open Access Journals (Sweden)

    Riku Pasonen

    2013-12-01

    Full Text Available In this article, a simulation model and concept of two switch bi-directional isolated DC/DC converter is presented. Converter is based on flyback converter type. Also control method for voltage regulation with bi-directional power transfer is presented. Target application of the proposed converter was selected to be a hybrid AC/DC distribution system concept of which was briefly described. The requirement of galvanic isolation in the hybrid AC/DC concept comes from use of shared neutral wire; DC current runs with unbalanced part of AC current in neutral wire. Without galvanic isolation grounded neutral would cause short circuit if DC/DC converter is connected to three phase rectifier or inverter. Simulation was carried out with PSCAD electromagnetic transient simulator.

  9. Detailed string stability analysis for bi-directional optimal velocity model

    Institute of Scientific and Technical Information of China (English)

    郑亮

    2015-01-01

    The class of bi-directional optimal velocity models can describe the bi-directional looking effect that usually exists in the reality and is even enhanced with the development of the connected vehicle technologies. Its combined string stability condition can be obtained through the method of the ring-road based string stability analysis. However, the partial string stability about traffic fluctuation propagated backward or forward was neglected, which will be analyzed in detail in this work by the method of transfer function and its H∞norm from the viewpoint of control theory. Then, through comparing the conditions of combined and partial string stabilities, their relationships can make traffic flow be divided into three distinguishable regions, displaying various combined and partial string stability performance. Finally, the numerical experiments verify the theoretical results and find that the final displaying string stability or instability performance results from the accumulated and offset effects of traffic fluctuations propagated from different directions.

  10. Matrix Converter Bi-directional Switch Power Loss and Cooling Condition Estimation for Integrated Drives

    OpenAIRE

    Sokolovs, A; Galkins, I

    2010-01-01

    In this paper power loss estimation of bi-directional switch of matrix converter is done by means of calculation and experiments. For safe operation of power devices an efficient cooling system of specific device must be designed. This work is part of a greater project of integrated matrix converter AC drives and the cooling problem here is viewed in context of this task. It is necessary to develop a compact power board and cooling system to extract excessive heat from power devices.

  11. The bi-directional moving structures in a coronal bright point

    Science.gov (United States)

    Li, Dong; Ning, Zongjun; Su, Yingna

    2016-09-01

    We report the bi-directional moving structures in a coronal bright point (CBP) on 2015 July 14. It is observed by the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). This CBP has a lifetime of ˜10 minutes, and a curved shape. The observations show that many bright structures are moving intermittently outward from the CBP brightness core. Such moving structures are clearly seen at AIA 171 Å, 193 Å, 211 Å, 131 Å, 94 Å, 335 Å and 304 Å, slit-jaw (SJI) 1330 Å and 1400 Å. In order to analyze these moving structures, the CBP is cut along the moving direction with a curved slit from the AIA and SJI images. Then we can obtain the time-distance slices, including the intensity and intensity-derivative diagrams, from which, the moving structures are recognized as the oblique streaks, and they are characterized by the bi-direction, simultaneity, symmetry, and periodicity. The average speed is around 300 km s^{-1}, while the typically period is ˜90 s. All these features (including the bi-directional flows and their periodicity) can be detected simultaneously at all the 9 wavelengths. This CBP takes place at the site between a small pair of magnetic polarities. High time resolution observations show that they are moving close to each other during its lifetime. These facts support the magnetic reconnection model of the CBP and the bi-directional moving structures could be the observational outflows after the reconnection. Therefore, they can be as the direct observation evidence of the magnetic reconnection.

  12. Development of an efficient bi-directional promoter with tripartite enhancer employing three viral promoters.

    Science.gov (United States)

    Patro, Sunita; Maiti, Indu B; Dey, Nrisingha

    2013-02-10

    We have developed a novel bi-directional promoter (FsFfCBD) by placing two heterogeneous core-promoters from the Figwort mosaic virus sub-genomic transcript promoter (FsCP, -69 to +31) and Cauliflower mosaic virus 35S promoter (CCP, -89 to +1) respectively on upstream (5') and downstream (3') ends of a tri-hybrid enhancer (FsEFfECE), in reverse orientation. The FsEFfECE domain encompasses three heterologous enhancer fragments from Figwort mosaic virus sub-genomic transcript promoter (FsE, 101 bp, -70 to -170), Figwort mosaic virus full-length transcript promoter (FfE, 196 bp, -249 to -54) and Cauliflower mosaic virus 35S promoter (CE, 254 bp, -343 to -90). The bi-directional nature of the FsFfCBD promoter (coupled to GFP and GUS) was established both in transient systems (onion epidermal cells and tobacco protoplasts) and transgenic plant (Nicotiana tabacum samsun NN) by monitoring the simultaneous expression of GFP and GUS employing fluorescence (for GFP) and biochemical (for GUS) based assays. In transgenic plants, the FsFfCBD promoter was found to be 6.8 and 2.5 times stronger than two parent promoters; Fs and FfC respectively. The bi-directional compound promoter FsFfCBD, composed of three heterologous enhancers with enhanced activity could become a valuable additional tool for efficient plant metabolic engineering and molecular pharming. PMID:23183382

  13. The Bi-directional Moving Structures in a Coronal Bright Point

    CERN Document Server

    Li, Dong; Su, Yingna

    2016-01-01

    We report the bi-directional moving structures in a coronal bright point (CBP) on 2015 July 14. It is observed by the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). This CBP has a lifetime of about 10 minutes, and a curved shape. The observations show that many bright structures are moving intermittently outward from the CBP brightness core. Such moving structures are clearly seen at AIA 171, 193, 211, 131, 94, 335 and 304 A, slit-jaw (SJI) 1330 and 1400 A. In order to analyze these moving structures, the CBP is cut along the moving direction with a curved slit from the AIA and SJI images. Then we can obtain the time-distance slices, including the intensity and intensity-derivative diagrams, from which, the moving structures are recognized as the oblique streaks, and they are characterized by the bi-direction, simultaneity, symmetry, and periodicity. The average speed is around 300 km/s, while the typically period is about 90 s. All these features (including the bi-directional fl...

  14. Development of an efficient bi-directional promoter with tripartite enhancer employing three viral promoters.

    Science.gov (United States)

    Patro, Sunita; Maiti, Indu B; Dey, Nrisingha

    2013-02-10

    We have developed a novel bi-directional promoter (FsFfCBD) by placing two heterogeneous core-promoters from the Figwort mosaic virus sub-genomic transcript promoter (FsCP, -69 to +31) and Cauliflower mosaic virus 35S promoter (CCP, -89 to +1) respectively on upstream (5') and downstream (3') ends of a tri-hybrid enhancer (FsEFfECE), in reverse orientation. The FsEFfECE domain encompasses three heterologous enhancer fragments from Figwort mosaic virus sub-genomic transcript promoter (FsE, 101 bp, -70 to -170), Figwort mosaic virus full-length transcript promoter (FfE, 196 bp, -249 to -54) and Cauliflower mosaic virus 35S promoter (CE, 254 bp, -343 to -90). The bi-directional nature of the FsFfCBD promoter (coupled to GFP and GUS) was established both in transient systems (onion epidermal cells and tobacco protoplasts) and transgenic plant (Nicotiana tabacum samsun NN) by monitoring the simultaneous expression of GFP and GUS employing fluorescence (for GFP) and biochemical (for GUS) based assays. In transgenic plants, the FsFfCBD promoter was found to be 6.8 and 2.5 times stronger than two parent promoters; Fs and FfC respectively. The bi-directional compound promoter FsFfCBD, composed of three heterologous enhancers with enhanced activity could become a valuable additional tool for efficient plant metabolic engineering and molecular pharming.

  15. CERN Relay Race

    CERN Document Server

    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

  16. 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

  17. Performance Analysis of Amplify-and-Forward Relay Based Cooperative Spectrum Sensing in Fading Channels

    Directory of Open Access Journals (Sweden)

    Shumon Alam

    2012-11-01

    Full Text Available Relay based cooperative spectrum sensing elevates the spectrum sensing problems in harsh propagationconditions if the relay nodes are positioned suitably for the dynamic spectrum access systems. This articleinvestigates the performance of relay based spectrum sensing (energy detection based in myriad fadingenvironments using the area under the receiver operating characteristic curve (AUC performancemetric. AUC is a single statistical parameter, which provides better insight of detection probabilitycompared to the receiver operating characteristic curve (ROC. The article includes the performanceanalysis of two-hop multi-relay amplify-and-forward (AF relay network with channel state information(CSI assisted relaying (variable relay gain and blind (fixed relay gain. A unified model is alsoinvestigated to describe the relay network for variable and fixed relay gain. Various fading and relayconfigurations are illustrated to show the efficacy of the energy detection based collaborative spectrumsensing in AF relay configuration using the AUC performance metric. Performance of the variable andfixed relay gain based AF relay network are analysed and compared considering different factorsaffecting energy sensing such as the per-hop signal-to-noise ratio (SNR, fading index, and the timebandwidth product. The results can be readily used for the design of the cognitive relay network.

  18. Efficient Relay Selection Scheme for Delay-Limited Non-Orthogonal Hybrid-ARQ Relay Channels

    CERN Document Server

    Maham, Behrouz; Debbah, Merouane

    2012-01-01

    We consider a half-duplex wireless relay network with hybrid-automatic retransmission request (HARQ) and Rayleigh fading channels. In this paper, we analyze the outage probability of the multi-relay delay-limited HARQ system with opportunistic relaying scheme in decode-and-forward mode, in which the \\emph{best} relay is selected to transmit the source's regenerated signal. A simple and distributed relay selection strategy is proposed for multi-relay HARQ channels. Then, we utilize the non-orthogonal cooperative transmission between the source and selected relay for retransmitting of the source data toward the destination if needed, using space-time codes or beamforming techniques. We analyze the performance of the system. We first derive the cumulative density function (CDF) and probability density function (PDF) of the selected relay HARQ channels. Then, the CDF and PDF are used to determine the outage probability in the $l$-th round of HARQ. The outage probability is required to compute the throughput-delay...

  19. Relay selection from an effective capacity perspective

    KAUST Repository

    Yang, Yuli

    2013-09-01

    In this work, we consider a cooperative network where multiple relay nodes having different modulation capabilities assist the end-to-end communication between a source and its destination. Firstly, we evaluate the effective capacity (EC) performance of the network under study. According to the analysis, an EC-based relay selection criterion is proposed. Based on the proposed selection rule and half-duplex decode-and-forward protocol, the activated relays cooperatively help with the packet transmission from the source. At the destination, packet combining is taken into account to improve the quality of service. Compared to the popular scheme, opportunistic relay selection, numerical results are provided to prove the validity and advantages of our proposed scheme in certain scenarios. Moreover, the analysis presented herein offers a convenient tool to the relaying transmission design, specifically on which relay selection scheme should be used as well as how to choose the receiving strategy between with and without packet combining at the destination. © 2013 IEEE.

  20. 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.

  1. Comparison of laser-assisted damage in soft tissue using bi-directional and forward-firing optical fiber

    Science.gov (United States)

    Kim, Changhwan; Sohn, Ik-Bu; Park, Hoyong; Lee, Yong Joong; Lee, Ho

    2014-03-01

    Laser-assisted endoscopic surgery is made possible by employing optical devices such as fiber optics and hollow wave-guides. In some applications of laser-assisted endoscopic surgery, it is necessary to change the direction of the light emission. Our group reported a new fabrication method for bi-directional firing fibers. The conical surface of the fiber tip made the bi-directional emission of the laser light at the distal end of the fiber. In this study, we employed the bi-directional firing fiber for laser-assisted coagulation of soft tissue. The developed fiber and the normal forward-firing fiber are used for the endoscopic delivery system of a continuous IR laser into an in vitro porcine liver. The ablation and coagulation pattern were compared for two distinctive fiber systems. Regardless of the laser's parameters, the bi-directional firing fiber produced a cavity and coagulation zone with more or less a circular shape, while the forward fiber produced an elongated cavity and coagulation region. The bi-directional firing fiber produced wider and shorter coagulation and cavity zones compared to that of the forward-firing fiber. We expect the bi-directional firing fiber to be an excellent optical delivery system for endoscopic laser-hyperthermia when used against various tumors in the liver, breast and thyroid.

  2. The Bi-Directional Prediction of Carbon Fiber Production Using a Combination of Improved Particle Swarm Optimization and Support Vector Machine

    Directory of Open Access Journals (Sweden)

    Chuncai Xiao

    2014-12-01

    Full Text Available This paper creates a bi-directional prediction model to predict the performance of carbon fiber and the productive parameters based on a support vector machine (SVM and improved particle swarm optimization (IPSO algorithm (SVM-IPSO. In the SVM, it is crucial to select the parameters that have an important impact on the performance of prediction. The IPSO is proposed to optimize them, and then the SVM-IPSO model is applied to the bi-directional prediction of carbon fiber production. The predictive accuracy of SVM is mainly dependent on its parameters, and IPSO is thus exploited to seek the optimal parameters for SVM in order to improve its prediction capability. Inspired by a cell communication mechanism, we propose IPSO by incorporating information of the global best solution into the search strategy to improve exploitation, and we employ IPSO to establish the bi-directional prediction model: in the direction of the forward prediction, we consider productive parameters as input and property indexes as output; in the direction of the backward prediction, we consider property indexes as input and productive parameters as output, and in this case, the model becomes a scheme design for novel style carbon fibers. The results from a set of the experimental data show that the proposed model can outperform the radial basis function neural network (RNN, the basic particle swarm optimization (PSO method and the hybrid approach of genetic algorithm and improved particle swarm optimization (GA-IPSO method in most of the experiments. In other words, simulation results demonstrate the effectiveness and advantages of the SVM-IPSO model in dealing with the problem of forecasting.

  3. Modeling the distribution of ammonia across Europe including bi-directional surface-atmosphere exchange

    Directory of Open Access Journals (Sweden)

    R. J. Wichink Kruit

    2012-04-01

    Full Text Available A large shortcoming of current chemistry transport models for simulating the fate of ammonia in the atmosphere is the lack of a description of the bi-directional surface-atmosphere exchange. In this paper, results of an update of the dry deposition module DEPAC in the LOTOS-EUROS model are discussed. It is shown that with the new description, which includes bi-directional surface-atmosphere exchange, the modeled ammonia concentrations increase almost everywhere, in particular in agricultural source areas. The reason is that by using a compensation point the ammonia life time and transport distance is increased. As a consequence, deposition of ammonia and ammonium decreases in agricultural source areas, while it increases in large nature areas and remote regions especially in Southern Scandinavia. The inclusion of a compensation point for water reduces the dry deposition over sea and allows reproducing the observed marine background concentrations at coastal locations to a better extend. A comparison with measurements shows that the model results better represent the measured ammonia concentrations. The concentrations in nature areas are slightly overestimated, while the concentrations in agricultural source areas are still underestimated. Although the introduction of the compensation point improves the model performance, the modeling of ammonia remains challenging. Important aspects are emission patterns in space and time as well as a proper approach to deal with the high concentration gradients in relation to model resolution. In short, the inclusion of a bi-directional surface atmosphere exchange is a significant step forward for modeling ammonia.

  4. Optimal Contract Design for Cooperative Relay Incentive Mechanism under Moral Hazard

    OpenAIRE

    Nan Zhao; Minghu Wu; Wei Xiong; Cong Liu

    2015-01-01

    Cooperative relay can effectively improve spectrum efficiency by exploiting the spatial diversity in the wireless networks. However, wireless nodes may acquire different network information with various users’ location and mobility, channels’ conditions, and other factors, which results in asymmetric information between the source and the relay nodes (RNs). In this paper, the relay incentive mechanism between relay nodes and the source is investigated under the asymmetric information. By mode...

  5. Optimization of Bi-Directional Flyback Converter for a High Voltage Capacitor Charging Application

    DEFF Research Database (Denmark)

    Thummala, Prasanth; Schneider, Henrik; Zhang, Zhe;

    2014-01-01

    This paper presents an optimization technique for a flyback converter with a bidirectional energy transfer. The main goal is to optimize the converter for driving an incremental dielectric electro active polymer actuator, which must be charged and discharged from 0 V to 2500 V DC, supplied from...... for this application. The efficiency and loss distribution results provided by the optimization routine provide a deep insight into the transformer design and its impact on total converter efficiency. Finally, experimental work on a prototype of the bi-directional flyback converter is presented. The maximum charging...... and discharging energy efficiencies of the optimized design, are 96.1% and 85%, respectively....

  6. Study on Application of Bi-directional Combination Technology Integrating Residue Hydrotreating with Catalytic Cracking RICP

    Institute of Scientific and Technical Information of China (English)

    Niu Chuanfeng; Gao Yongcan; Dai Lishun; Li Dadong

    2008-01-01

    After analysing the disadvantages of the traditional residue hydrotreating-catalytic cracking combination process, RIPP has proposed a bi-directional combination technology integrating residue hydrotreating with catalytic cracking called RICP which does not further recycles the FCC heavy cycle oil (HCO) inside the FCC unit and delivers HCO to the residue hydrotreating unit as a diluting oil for the residue that is concurrently subjected to hydrotreating prior to being used as the FCC feed oil. The RICP technology can stimulate residue hydrotreating reactions through utilization of HCO along with an increased yield of FCC light distillate, resulting in enhanced petroleum utilization and economic benefits of the refinery.

  7. Moral judgment modulation by disgust is bi-directionally moderated by individual sensitivity

    Directory of Open Access Journals (Sweden)

    How Hwee eOng

    2014-03-01

    Full Text Available Modern theories of moral judgment predict that both conscious reasoning and unconscious emotional influences affect the way people decide about right and wrong. In a series of experiments, we tested the effect of subliminal and conscious priming of disgust facial expressions on moral dilemmas. Trolley-car-type scenarios were used, with subjects rating how acceptable they found the utilitarian course of action to be. On average, subliminal priming of disgust facial expressions resulted in higher rates of utilitarian judgments compared to neutral facial expressions. Further, in replication, we found that individual change in moral acceptability ratings due to disgust priming was modulated by individual sensitivity to disgust, revealing a bi-directional function. Our second replication extended this result to show that the function held for both subliminally and consciously presented stimuli. Combined across these experiments, we show a reliable bi-directional function, with presentation of disgust expression primes to individuals with higher disgust sensitivity resulting in more utilitarian judgments (i.e., number-based and presentations to individuals with lower sensitivity resulting in more deontological judgments (i.e., rules-based. Our results may reconcile previous conflicting reports of disgust modulation of moral judgment by modeling how individual sensitivity to disgust determines the direction and degree of this effect.

  8. Impact of holding umbrella on uni- and bi-directional pedestrian flow: Experiments and modeling

    CERN Document Server

    Guo, Ning; Jiang, Rui; Hu, Mao-Bin; Jia, Bin

    2016-01-01

    In this paper, the impact of holding umbrella on the uni- and bi-directional flow has been investigated via experiment and modeling. In the experiments, pedestrians are required to walk clockwise/anti-clockwise in a ring-shaped corridor under normal situation and holding umbrella situation. No matter in uni- or bi-directional flow, the flow rate under holding umbrella situation decreases comparing with that in normal situation. In bidirectional flow, pedestrians segregate into two opposite moving streams very quickly under normal situation, and clockwise/anti-clockwise walking pedestrians are always in the inner/outer lane due to right-walking preference. Under holding umbrella situation, spontaneous lane formation has also occurred. However, when holding umbrella, pedestrians may separate into more than two lanes. Moreover, the merge of lanes have been observed, and clockwise/anti-clockwise pedestrians are not always in the inner/outer lane. To model the flow dynamics, an improved force-based model has been ...

  9. Geologically controlled bi-directional exchange of groundwater with a hypersaline lake in the Canadian prairies

    Science.gov (United States)

    Bentley, Laurence R.; Hayashi, Masaki; Zimmerman, Elena P.; Holmden, Chris; Kelley, Lynn I.

    2016-06-01

    Hypersaline lakes occur in hydrologically closed basins due to evaporitic enrichment of dissolved salts transported to the lakes by surface water and groundwater. At the hypersaline Lydden Lake in Saskatchewan, Canada, groundwater/lake-water interaction is strongly influenced by the geological heterogeneity of glacial deposits, whereby a highly permeable glaciofluvial sand/gravel deposit is underlain by glaciolacustrine deposits consisting of dense clay interspersed with silt/sand lenses. Pressure head distribution in a near shore area indicates a bi-directional flow system. It consists of topographically driven flow of fresh groundwater towards the lake in the sand/gravel aquifer and density-driven, landward flow of saline groundwater in the underlying glaciolacustrine deposits. Electrical resistivity tomography, and chemical and isotopic composition of groundwater clearly show the landward intrusion of saline water in the heterogeneous unit. The feasibility of bi-directional flow and transport is supported by numerical simulations of density-coupled groundwater flow and transport. The results suggest that the geologically controlled groundwater exchange processes have substantial influences on both inputs and outputs of dissolved minerals in hypersaline lakes in closed basins.

  10. Review and parameterisation of bi-directional ammonia exchange between vegetation and the atmosphere

    Science.gov (United States)

    Massad, R.-S.; Nemitz, E.; Sutton, M. A.

    2010-11-01

    Current deposition schemes used in atmospheric chemical transport models do not generally account for bi-directional exchange of ammonia (NH3). Bi-directional exchange schemes, which have so far been applied at the plot scale, can be included in transport models, but need to be parameterised with appropriate values of the ground layer compensation point (χg), stomatal compensation point (χs) and cuticular resistance (Rw). We review existing measurements of χg, χs as well as Rw and compile a comprehensive dataset from which we then propose generalised parameterisations. χs is related to Γs, the non-dimensional ratio of [NH4+]apo and [H+]apo in the apoplast, through the temperature dependence of the combined Henry and dissociation equilibrium. The meta-analysis suggests that the nitrogen (N) input is the main driver of the apoplastic and bulk leaf concentrations of ammonium (NH4 apomodel for example). In principle, the parameterisations should be applicable to other climates, though there is a need for more underpinning data, with the uncertainties being especially large for tropical and subtropical conditions.

  11. 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....

  12. Adaptive relay selection algorithm in decode-and-forward cooperative communication networks%译码转发协同通信网络自适应中继选择算法

    Institute of Scientific and Technical Information of China (English)

    康虹; 冯文江; 贾年龙; 孟器宇

    2013-01-01

    An adaptive relay selection algorithm(ARS) is proposed to optimize the performance of decode-and-forward cooperative communication networks, both system outage probability and average numbers of cooperative relays are analyzed. When the direct transmission between source and destination is fail, according to the channel quality, the destination orders relay nodes in the decode set, and the ordered relays are included in cooperation in turn until the instantaneous received SNR at destination is not smaller than the preset SNR threshold. Simulation results show that, the proposed algorithm can get optimal outage performance, decrease the average numbers of cooperative relays efficiently, to incrense bandwidth efficiency and reduce system overhead.%为了优化译码转发协同通信网络的性能,提出一种自适应中继选择算法(ARS),并对系统中断概率和平均协同中继数进行分析.该算法在源节点到目的节点的直接传输失败时,目的节点对译码集中的中继节点按信道质量进行降序排列,依次选择序列中的中继节点参与协同,直到目的节点的瞬时接收信噪比不低于预置信噪比门限.仿真结果表明,ARS算法能够获得最优系统中断性能,有效减少平均协同中继数,从而提高带宽效率,降低系统开销.

  13. CERN Relay Race

    CERN Document Server

    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

  14. 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

  15. 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) transmissio...

  16. Multifunction protective relay

    Science.gov (United States)

    Harlow, J.; Yalla, M.; Kantor, J.

    1991-11-01

    Since the enactment of the National Energy Act of 1979, many private energy producers have been planning and building small generation and cogeneration facilities in order to sell power to the local utility. Many of the non-utility generators built after 1979 are connected directly to the closest utility distribution circuit. Aware of the problems associated with connecting generators in this manner, electric utilities across the country developed specifications and standards to allow safe and reliable interconnection. The report describes a malfunction protective relay which uses state-of-the-art digital signal processing procedures to accomplish the objective of providing most of the relay requirements of utility electrical interconnections. The relay has been demonstrated to be suitable for this critical application through extensive laboratory and in-service field testing. The relay, incorporating thirteen distinct protection functions affords the user the savings of the initial capital cost plus simplicity of installation and use.

  17. 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...

  18. 频率选择性信道中的多用户分布式波束形成技术%Distributed Multiuser Beamforming for Relay Networks in Frequency-selective Channels

    Institute of Scientific and Technical Information of China (English)

    张立; 陈海华; 何明; 孙桂玲

    2015-01-01

    该文研究频率选择性信道中多用户点对点分布式中继网络波束形成技术。为了均衡源节点与中继节点以及中继节点与目标节点之间的频率选择性信道,该文提出的波束形成技术在中继节点上采用有限长响应滤波器和滤波而后转发的中继数据传输方法,以最小化中继节点的发射总功率为目标,同时满足所有目标节点的服务质量(QoS)。该波束形成优化问题的直接形式由于其非凸性而难以求得最优解。该文采用半定松弛(SDP)方法将其近似为凸优化问题,进而可以用内点法高效快速求解。仿真结果表明,相较于传统的放大而后转发的波束形成技术,所提波束形成方法能有效提高频率选择性信道中多用户中继网络的性能。%In this paper, a distributed peer-to-peer beamforming technique in frequency-selective relay networks is proposed. It is assumed that all the relay nodes use Filter-and-Forward (FF) protocol to compensate for the source-to-relay and relay-to-destination channels. All the channels of the active source-destination pairs are considered to be frequency-selective. The beamforming strategy that minimizes the total relay transmitted power subject to the Quality-of-Service (QoS) constraints for all of the destination nodes is considered. The resultant problem is approximately solved using Semi-Definite Programming (SDP). Simulation results demonstrate that in frequency-selective multiuser relay networks, the proposed technique substantially outperforms the existing amplify-and-forward peer-to-peer beamforming methods.

  19. 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

  20. Response of piping system on friction support to bi-directional excitation

    International Nuclear Information System (INIS)

    Installation of friction devices between a piping system and its supporting medium is an effective way of energy dissipation in the piping systems. In this paper, seismic effectiveness of friction type support for a piping system subjected to two horizontal components of earthquake motion is investigated. The interaction between the mobilized restoring forces of the friction support is duly considered. The non-linear behavior of the restoring forces of the support is modeled as an elastic-perfectly plastic system with a very high value of initial stiffness. Such an idealization avoids keeping track of transitional rules (as required in conventional modeling of friction systems) under arbitrary dynamic loading. The frictional forces mobilized at the friction support are assumed to be dependent on the sliding velocity and instantaneous normal force acting on the support. A detailed systematic procedure for analysis of piping systems supported on friction support considering the effects of bi-directional interaction of the frictional forces is presented. The proposed procedure is validated by comparing the analytical seismic responses of a spatial piping system supported on a friction support with the corresponding experimental results. The responses of the piping system and the frictional forces of the support are observed to be in close agreement with the experimental results validating the proposed analysis procedure. It was also observed that the friction supports are very effective in reducing the seismic response of piping systems. In order to investigate the effects of bi-directional interaction of the frictional forces, the seismic responses of the piping system are compared by considering and ignoring the interaction under few narrow-band and broad-band (real earthquake) ground motions. The bi-directional interaction of the frictional forces has significant effects on the response of piping system and should be included in the analysis of piping systems

  1. 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.

  2. Optimal Contract Design for Cooperative Relay Incentive Mechanism under Moral Hazard

    Directory of Open Access Journals (Sweden)

    Nan Zhao

    2015-01-01

    Full Text Available Cooperative relay can effectively improve spectrum efficiency by exploiting the spatial diversity in the wireless networks. However, wireless nodes may acquire different network information with various users’ location and mobility, channels’ conditions, and other factors, which results in asymmetric information between the source and the relay nodes (RNs. In this paper, the relay incentive mechanism between relay nodes and the source is investigated under the asymmetric information. By modelling multiuser cooperative relay as a labour market, a contract model with moral hazard for relay incentive is proposed. To effectively incentivize the potential RNs to participate in cooperative relay, the optimization problems are formulated to maximize the source’s utility while meeting the feasible conditions under both symmetric and asymmetric information scenarios. Numerical simulation results demonstrate the effectiveness of the proposed contract design scheme for cooperative relay.

  3. Continuous-variable quantum cryptography with untrusted relays

    CERN Document Server

    Pirandola, Stefano; Spedalieri, Gaetana; Weedbrook, Christian; Braunstein, Samuel L

    2013-01-01

    We extend the field of continuous-variable quantum cryptography to a more robust formulation which can be applied to untrusted networks. We consider two remote parties connected to an untrusted relay by insecure quantum links. To generate correlations, they transmit coherent states to the relay where a continuous-variable Bell detection is performed. Despite the possibility that the working mechanism of the relay could be fully corrupted and the links subject to optimal coherent attacks, the parties are still able to extract a secret key. Furthermore, our analysis shows that very long distances and high rates can be reached when the relay is proximal to one of the parties, configuration typical of a mobile device connecting to a public access point. Thus, using the cheapest possible quantum resources, we show the possibility of long-distance high-rate quantum key distribution in network topologies where direct links are missing between two end-users and intermediate relays cannot be trusted.

  4. A distributed optical fiber bi-directional strain-displacement sensor

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A distributed optical fiber strain-displacement sensor is developed, which consists of an optical fiber gauge of strain-displacement and an optical time domain reflectometer (OTDR). The operational principle is the modulation of fiber loss in OTDR, i.e. the strain and displacement in monitoring position are obtained from the bending loss of optical fiber bonded on the optical fiber gauge of strain-displacement. After examining the strain and displacement in the cantilever and the micro displacement rack respectively, the result indicates that the distributed optical fiber gauge of strain-displacement can monitor strains or displacements in different sensitive lengths. The key technique for measuring bi-directional strain-displacement is the pretreatment of bending of the freely suspended optical fibers, which can be identified with OTDR by inserting time delay optical fiber.

  5. Bi-directional causality in California's electricity and natural-gas markets

    International Nuclear Information System (INIS)

    The Granger instantaneous-causality test is applied to explore the potential causal relationships between wholesale electricity and natural-gas prices in California. The test shows these relationships to be bi-directional, and reveals California's electricity and natural-gas markets to be as inextricably intertwined as casual observation and theoretical considerations would suggest they ought to be. This meshing of markets exacerbated the effects of California's natural-gas crisis on the contemporaneous electricity crisis, while concurrently the electricity crisis may have contributed to the dysfunction in the national-gas market and helped to precipitate the natural-gas crisis. The finding supports an integrated approach, as opposed to a piecemeal approach, for formulating energy policy recommendations, not just in California but in the world at large. (author)

  6. A multi-layered vascular scaffold with symmetrical structure by bi-directional gradient electrospinning.

    Science.gov (United States)

    Wu, Tong; Huang, Chen; Li, Dawei; Yin, Anlin; Liu, Wei; Wang, Jing; Chen, Jianfeng; Ei-Hamshary, Hany; Al-Deyab, Salem S; Mo, Xiumei

    2015-09-01

    Multi-layered scaffolds are advantageous in vascular tissue engineering, in consideration of better combination of biomechanics, biocompatibility and biodegradability than the scaffolds with single structure. In this study, a bi-directional gradient electrospinning method was developed to fabricate poly(l-lactide-co-caprolactone) (P(LLA-CL)), collagen and chitosan based tubular scaffold with multi-layered symmetrical structure. The multi-layered composite scaffold showed improved mechanical property and biocompatibility, in comparison to the blended scaffold using the same proportion of raw materials. Endothelialization on the multi-layered scaffold was accelerated owing to the bioactive surface made of pure natural materials. hSMCs growth showed the similar results because of its better biocompatibility. Additionally, fibers morphology change, pH value balance and long term mechanical support results showed that the gradient structure effectively improved biodegradability. PMID:26101818

  7. High efficiency interleaved bi-directional ZVS DC-DC converter

    Science.gov (United States)

    Zafarullah Khan, M.; Mohsin Naveed, M.; Akbar Hussain, D. M.

    2013-06-01

    A high efficiency interleaved bi-directional ZVS DC-DC converter is presented in this paper. This converter can be operated in both buck and boost mode. CoolMOS is used as a power device to achieve low conduction losses and fast turn off. The value of inductance is selected such that the CoolMOS drain-to-source voltage always falls to zero before it turns on and ZVS is achieved. Multiphase interleaved inductors are used to achieve high power and low ripple currents. Converter is operated at 50kHz and MATLAB Simulink simulation is performed. 6kW prototype converter is implemented in buck mode and simulation results are verified.

  8. A possible mechanism for self coordination of bi-directional traffic across nuclear pores

    CERN Document Server

    Kapon, Ruti; Mukamel, David; Reich, and Ziv

    2008-01-01

    Nuclear pore complexes are constantly confronted by large fluxes of macromolecules and macromolecular complexes that need to get into and out of the nucleus. Such bi-directional traffic occurring in a narrow channel can easily lead to jamming. How then is passage between the nucleus and cytoplasm maintained under the varying conditions that arise during the lifetime of the cell? Here, we address this question using computer simulations in which the behaviour of the ensemble of transporting cargoes is analyzed under different conditions. We suggest that traffic can exist in two distinct modes, depending on concentration of cargoes and dissociation rates of the transport receptor-cargo complexes from the pores. In one mode, which prevails when dissociation is quick and cargo concentration is low, transport in either direction proceeds uninterrupted by the other direction. The result is that overall-traffic-direction fluctuates rapidly and unsystematically between import and export. Remarkably, when cargo concen...

  9. A bi-directional gap model for simulating the directional thermal radiance of row crops

    Institute of Scientific and Technical Information of China (English)

    CHEN; Liangfu; (陈良富); LIU; Qinhuo; (柳钦火); FAN; Wenjie; (范闻捷); LI; Xiaowen; (李小文); XIAO; Qing; (肖青); YAN; Guangjian; (闫广建); TIAN; Guoliang; (田国良)

    2002-01-01

    Row crops are a kind of typical vegetation canopy between discrete canopy and continuous canopy. Kimes et al. studied the directional thermal radiation of row crops using the geometrical optical model, which simplified row structure as "box" and neglected the gap among foliage and did not consider the emissivity effects. In this work we take account of the gaps along illumination and viewing directions and propose a bi-direction gap model on the basis of the idea of gap probability of discrete vegetation canopy introduced by "Li-Strahler" and inter-correlation of continuous vegetation developed by Kuusk. It can be used to explain "hot spot" effects in thermal infrared region. The gap model has been validated by field experiment on winter wheat planted in shape of rows and results show that the gap model is better than Kimes' model in describing the directionality of thermal infrared emission for row crops.

  10. Demonstration and experimental evaluation of a bi-directional 10-GHz microwave photonic filter

    Science.gov (United States)

    Zaldívar-Huerta, I. E.; Correa-Mena, A. G.; Hernández-Nava, P.; García-Juárez, A.; Rodríguez-Asomoza, J.; Lee, Min Won

    2016-09-01

    A bi-directional 10-GHz microwave photonic filter is proposed and experimentally evaluated. Its frequency response consists of a series of microwave band-pass windows obtained by the interaction of externally modulated multimode laser diodes emitting around of 1550 nm associated to the chromatic dispersion parameter of an optical fiber, as well as the length of the optical link. Microwave band-pass windows exhibit on average a-3 dB bandwidth of 378 MHz. This electro-optical system shows an efficient configuration and good performance. Potentially, filtered microwave signals can be used as electrical carriers in optical communication systems to transmit and distribute services such as video, voice and data.

  11. UWB Bi-directional Bow-tie antenna loaded by rings

    Science.gov (United States)

    Peng, Lin; Sun, Kai; Xie, Ji-yang; Qiu, Yu-jie; Jiang, Xing

    2016-07-01

    Performances of bow-tie antennae can be improved by loading a ring. Specially, the distorted radiation patterns of the reference bow-tie antenna (RBA) at high frequencies become less distorted when a ring is added. That is due to the disciplined current flows trained by the ring. Furthermore, when more rings are loaded, which act as reflectors, higher directivities are obtained and, patterns become bi-directional. Antennae with no ring (RBA), one ring, two rings (three cases), three rings, and four rings are investigated. Research find that loading more rings means better directivity. The directivity of the RBA varies from 2.29 dB to 3.66 dB for the frequency band from 2.5 to 7.5 GHz while the directivity for the four-ring-loaded case varies from 4.27 dB to 7.61 dB in that frequency band.

  12. Bi-directional conversion between microwave and optical frequencies in a piezoelectric optomechanical device

    Science.gov (United States)

    Vainsencher, Amit; Satzinger, K. J.; Peairs, G. A.; Cleland, A. N.

    2016-07-01

    We describe the principles of design, fabrication, and operation of a piezoelectric optomechanical crystal with which we demonstrate bi-directional conversion of energy between microwave and optical frequencies. The optomechanical crystal has an optical mode at 1523 nm co-located with a mechanical breathing mode at 3.8 GHz, with a measured optomechanical coupling strength gom/2π of 115 kHz. The breathing mode is driven and detected by curved interdigitated transducers that couple to a Lamb mode in suspended membranes on either end of the optomechanical crystal, allowing the external piezoelectric modulation of the optical signal as well as the converse, the detection of microwave electrical signals generated by a modulated optical signal. We compare measurements to theory where appropriate.

  13. Clinico-serologic co-relation in bi-directional ABO incompatible hemopoietic stem cell transplantation

    Directory of Open Access Journals (Sweden)

    Sabita Basu

    2015-01-01

    Full Text Available Background: The ABO blood group system is of prime significance in red cell transfusion and organ transplantation. However, ABO compatibility is not critical in allogenic hemopoietic stem cell transplantation (HSCT and approximately 40-50% of hemopoietic stem cell transplants are ABO incompatible. This incompatibility may be major, minor or bi-directional. Though there are descriptions of transfusion practice and protocols in ABO incompatible HSCT, there are considerable variations and transfusion support in these patients can be very challenging. Aims: The immunohematologic observations in two cases of bi-directional ABO incompatible HSCT have been described, and clinico-serologic correlation has been attempted. Materials and Methods: In both cases, peripheral blood stem cell harvests were obtained using the Cobe spectra cell separator. Immunohematologic assessments in the donor and recipient were done as a part of pre HSCT evaluation. Both the standard tube technique and column agglutination method (Ortho Biovue Micro Bead System was used. Antibody screen was done by column agglutination method using three cell panel (Surgiscreen cells. Isoagglutinin titration was done by the master dilution method and standard validated techniques were used. Results: The pattern of laboratory findings in the two cases was different and so were the clinical outcomes. Although there was early engraftment in the first case, the second case developed pure red cell aplasia and this was well-reflected in the immunohematologic assessments. Conclusion: Immunohematologic assessment correlated well with the clinical picture and could be used to predict clinical outcome and onset of complications in ABO incompatible HSCT.

  14. An Experimental Investigation of the Responses of Classic Spar Platform Subjected to Bi-directional Waves

    Directory of Open Access Journals (Sweden)

    V.J. Kurian

    2015-01-01

    Full Text Available The effect of the bi-directional short-crested waves on the dynamic motion responses of the moored classic spar is demonstrated from the results of the models test in this study. Practically in the design of offshore structures, long-crested or 2-dimensional wave properties that propagated to one direction are considered. Even though such long-crested wave is widely used for the design purposes, it is hardly determined in the real sea. The wind generated sea state in the real sea conditions are indeed well represented by the short-crested waves. Short-crested waves are defined as linear summation of long-crested wave series that propagated to different directions. Hence, the motions of the model were investigated experimentally by conducting the wave tank tests in the wave tank of Offshore Laboratory of Universiti Teknologi PETRONAS. Five groups of bi-directional wave series were defined and exerted on the classic spar model, which fabricated by using steel with scaling factor of 1:100. From the results measured, it was found that similar trends of the responses in term of Response Amplitude Operator (RAO for surge, heave and pitch motions were obtained. Maximum responses of surge, heave and pitch were found due to wave crossing angle 90°, while minimum response was found due to wave crossing angle 135°, respectively. It could be concluded that the wave crossing angle 90° (BD3 gives the widest spreading for short crested waves, while the wave crossing angle 135° (BD4 gives the narrowest spreading for short crested waves.

  15. Power Allocation Strategies across N Orthogonal Channels at Both Source and Relay

    OpenAIRE

    Ko, Youngwook; Ardakani, Masoud; Vorobyov, Sergiy A.

    2010-01-01

    We consider a wireless relay network with one source, one relay and one destination, where communications between nodes are preformed via N orthogonal channels. This, for example, is the case when orthogonal frequency division multiplexing is employed for data communications. Since the power available at the source and relay is limited, we study optimal power allocation strategies at the source and relay in order to maximize the overall source-destination capacity under individual power const...

  16. Buffer-Aided Relaying with Adaptive Link Selection

    CERN Document Server

    Zlatanov, Nikola; Popovski, Petar

    2012-01-01

    In this paper, we consider a simple network consisting of a source, a half-duplex decode-and-forward relay, and a destination. We propose a new relaying protocol employing adaptive link selection, i.e., in any given time slot, based on the channel state information of the source-relay and the relay-destination link a decision is made whether the source or the relay transmits. In order to avoid data loss at the relay, adaptive link selection requires the relay to be equipped with a buffer such that data can be queued until the relay-destination link is selected for transmission. We study both delay constrained and delay unconstrained transmission. For the delay unconstrained case, we characterize the optimal link selection policy, derive the corresponding throughput, and develop an optimal power allocation scheme. For the delay constrained case, we propose to starve the buffer of the relay by choosing the decision threshold of the link selection policy smaller than the optimal one and derive a corresponding up...

  17. Relay Telecommunications for the Coming Decade of Mars Exploration

    Science.gov (United States)

    Edwards, C.; DePaula, R.

    2010-01-01

    Over the past decade, an evolving network of relay-equipped orbiters has advanced our capabilities for Mars exploration. NASA's Mars Global Surveyor, 2001 Mars Odyssey, and Mars Reconnaissance Orbiter (MRO), as well as ESA's Mars Express Orbiter, have provided telecommunications relay services to the 2003 Mars Exploration Rovers, Spirit and Opportunity, and to the 2007 Phoenix Lander. Based on these successes, a roadmap for continued Mars relay services is in place for the coming decade. MRO and Odyssey will provide key relay support to the 2011 Mars Science Laboratory (MSL) mission, including capture of critical event telemetry during entry, descent, and landing, as well as support for command and telemetry during surface operations, utilizing new capabilities of the Electra relay payload on MRO and the Electra-Lite payload on MSL to allow significant increase in data return relative to earlier missions. Over the remainder of the decade a number of additional orbiter and lander missions are planned, representing new orbital relay service providers and new landed relay users. In this paper we will outline this Mars relay roadmap, quantifying relay performance over time, illustrating planned support scenarios, and identifying key challenges and technology infusion opportunities.

  18. Cooperation with an Untrusted Relay: A Secrecy Perspective

    CERN Document Server

    He, Xiang

    2009-01-01

    We consider the communication scenario where a source-destination pair wishes to keep the information secret from a relay node despite wanting to enlist its help. For this scenario, an interesting question is whether the relay node should be deployed at all. That is, whether cooperation with an untrusted relay node can ever be beneficial. We first provide an achievable secrecy rate for the general untrusted relay channel, and proceed to investigate this question for two types of relay networks with orthogonal components. For the first model, there is an orthogonal link from the source to the relay. For the second model, there is an orthogonal link from the relay to the destination. For the first model, we find the equivocation capacity region and show that answer is negative. In contrast, for the second model, we find that the answer is positive. Specifically, we show by means of the achievable secrecy rate based on compress-and-forward, that, by asking the untrusted relay node to relay information, we can ac...

  19. Non-Markovian Reactivation of Quantum Relays

    CERN Document Server

    Pirandola, Stefano; Jacobsen, Christian S; Spedalieri, Gaetana; Braunstein, Samuel L; Gehring, Tobias; Andersen, Ulrik L

    2015-01-01

    We consider a quantum relay which is used by two parties to perform several continuous-variable protocols: Entanglement swapping, distillation, quantum teleportation, and quantum key distribution. The theory of these protocols is extended to a non-Markovian model of decoherence characterized by correlated Gaussian noise. Even if bipartite entanglement is completely lost at the relay, we show that the various protocols can progressively be reactivated by the separable noise-correlations of the environment. In fact, above a critical amount, these correlations are able to restore the distribution of quadripartite entanglement, which can be localized into an exploitable bipartite form by the action of the relay. Our findings are confirmed by a proof-of-principle experiment and show the potential advantages of non-Markovian effects in a quantum network architecture.

  20. 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.

  1. On the capacity of multiple cognitive links through common relay under spectrum-sharing constraints

    KAUST Repository

    Yang, Yuli

    2011-06-01

    In this paper, we consider an underlay cognitive relaying network consisting of multiple secondary users and introduce a cooperative transmission protocol using a common relay to help with the communications between all secondary source-destination pairs for higher throughput and lower realization complexity. A whole relay-assisted transmission procedure is composed of multiple access phase and broadcast phase, where the relay is equipped with multiple antennas, and the secondary sources and destinations are single-antenna nodes. Considering the spectrum-sharing constraints on the secondary sources and the relay, we analyze the capacity behaviors of the underlay cognitive relaying network under study. The corresponding numerical results provide a convenient tool for the presented network design and substantiate a distinguishing feature of introduced design in that multiple secondary users\\' communications do not rely on multiple relays, hence allowing for a more efficient use of the radio resources. © 2011 IEEE.

  2. Opportunistic Relay Selection Method of Cooperative Communication Network Under Eavesdropping Environment%窃听环境下协作通信网络的机会中继选择方法

    Institute of Scientific and Technical Information of China (English)

    李国兵; 惠鏸

    2015-01-01

    In cooperative communication network,a relay selection procedure is usually based on the channel conditions of legitimate channels in traditional relay selection methods,thus it is hard to guarantee the security and privacy of the transmission in the presence of eavesdroppers. To tackle this problem,an opportunistic relay selection method considering the Channel State Information ( CSI ) of both the legitimate users and the eavesdropper is proposed to minimize the Secrecy Outage Probability ( SOP ) in a cooperative Decode-and-Forward ( DF ) network. Firstly, the optimal power allocation method is given when the total transmit power of the source and relay is constrained. Based on that,the best relay selection algorithm is proposed and the closed form expression of secrecy outage probability is derived. Simulation results verify the correctness of the closed form expression of secrecy outage probability, and show that the proposed algorithm greatly reduces the secrecy outage probability of the system compared with the traditional methods.%传统的最佳中继选择方法仅依赖于合法用户的信道条件,在存在窃听用户的环境中无法保证信息传输的安全性与私密性。针对该问题,以最小化系统安全中断概率为目标,综合考虑合法用户与窃听用户的信道状态信息,提出一种新的机会中继选择方法。针对解码转发协作通信网络,给出系统总发射功率受限条件下的最佳功率分配方案,并在此基础上设计最佳中继节点的选择方法,推导得到系统安全中断概率的闭式表达式。仿真结果验证了该闭式表达式的正确性,并表明与传统中继选择方法相比,提出的中继选择方法可显著降低系统的安全中断概率。

  3. CERN Relay Race

    CERN Document Server

    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.   

  4. ROLE OF LEAF SURFACE WATER IN THE BI-DIRECTIONAL AMMONIA EXCHANGE BETWEEN THE ATMOSPHERE AND TERRESTRIAL BIOSPHERE

    Science.gov (United States)

    A field experiment was conducted to study the ammonia exchange between plants and the atmosphere in a soybean field in Duplin County, North Carolina during the summer of 2002. Measurements indicate that the net canopy-scale ammonia exchange is bi-directional and has a significant...

  5. Dielectric Electro Active Polymer Incremental Actuator Driven by Multiple High-Voltage Bi-directional DC-DC Converters

    DEFF Research Database (Denmark)

    Thummala, Prasanth; Zhang, Zhe; Andersen, Michael A. E.;

    2013-01-01

    capacitive sub-actuators. It needs to be driven by three high voltage (~2.5 kV) DC-DC converters, to achieve the linear incremental motion. The topology used for this application is a bi-directional flyback DC-DC converter. The control of the incremental actuator involves, implementation of digital...

  6. Arginine bi-directional translocation and breakdown into ornithine along the arbuscular mycorrhizal mycelium

    Institute of Scientific and Technical Information of China (English)

    JIN HaiRu

    2009-01-01

    Bi-directional translocatlon and degradation of Arginine (Arg) along the arbuscular mycorrhizal (AM) fungal mycellum were testified through 15N and/or 13C isotopic labeling. In vitro mycorrhizas of Glomus intraradices and Ri T-DNA-transformed carrot roots were grown in dual compartment Petri dishes. [15N-and/or13C]Arg was supplied to either the fungal compartment or the mycorrhizal compartment or separate dishes containing the uncolonized roots. The levels and labeling of free amino acids (AAs) in the mycorrhizal roots and in the extraradical mycelia(ERM) were measured by gas chromatogra-phy/mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). The ERM of AM fungi exposed in either NH4+ or urea as sole external nitrogen source had much higher 15N enrichment of Arg, compared with those In nitrate or exogenous Arg; however, glycerol supplied as an external car-bon source to the ERM had no significant effect on the level of Arg in the ERM. Meanwhile, Arg bio-synthesized In the ERM could be translocated intact to the mycorrhizal roots and thereby the level of Arg in the mycorrhizal roots increased to about 20% after culture of ERM in 4 mmol/L NH4+ for 6 weeks.Also Arg was found to be bi-directionally transported along the AM fungal mycelium through [U-13C]Arg labeling either In the mycorrhizal compartment or in the fungal compartment. Once Arg was translo-cated to the potential N-limited sites, it would be further degraded into ornithine (Orn) and urea since either [U-13C] or [U-15N/U-13C]Orn was apparently shown up in the mycorrhizal root tissues when [U-13C] or [U-15N/U-13C]Arg was labeled In the fungal compartment, respectively. Evidently Orn formation indi-cated the ongoing activities of Arg translocation and degradation through the urea cycle in AM fungal mycelium.

  7. Arginine bi-directional translocation and breakdown into ornithine along the arbuscular mycorrhizal mycelium

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Bi-directional translocation and degradation of Arginine (Arg) along the arbuscular mycorrhizal (AM) fungal mycelium were testified through 15N and/or 13C isotopic labeling. In vitro mycorrhizas of Glomus intraradices and Ri T-DNA-transformed carrot roots were grown in dual compartment Petri dishes. [15N- and/or13C]Arg was supplied to either the fungal compartment or the mycorrhizal compartment or separate dishes containing the uncolonized roots. The levels and labeling of free amino acids (AAs) in the mycorrhizal roots and in the extraradical mycelia(ERM) were measured by gas chromatogra- phy/mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). The ERM of AM fungi exposed in either NH4+ or urea as sole external nitrogen source had much higher 15N enrichment of Arg, compared with those in nitrate or exogenous Arg; however, glycerol supplied as an external car- bon source to the ERM had no significant effect on the level of Arg in the ERM. Meanwhile, Arg bio- synthesized in the ERM could be translocated intact to the mycorrhizal roots and thereby the level of Arg in the mycorrhizal roots increased to about 20% after culture of ERM in 4 mmol/L NH4+ for 6 weeks. Also Arg was found to be bi-directionally transported along the AM fungal mycelium through [U-13C]Arg labeling either in the mycorrhizal compartment or in the fungal compartment. Once Arg was translo- cated to the potential N-limited sites, it would be further degraded into ornithine (Orn) and urea since either [U-13C] or [U-15N/U-13C]Orn was apparently shown up in the mycorrhizal root tissues when [U-13C] or [U-15N/U-13C]Arg was labeled in the fungal compartment, respectively. Evidently Orn formation indi- cated the ongoing activities of Arg translocation and degradation through the urea cycle in AM fungal mycelium.

  8. Developing a Domain Model for Relay Circuits

    DEFF Research Database (Denmark)

    Haxthausen, Anne Elisabeth

    2009-01-01

    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...... defined, checked to be legal, and the reaction to an input can be simulated....

  9. 2005 CERN Relay Race

    CERN Document Server

    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.

  10. CERN Relay Race

    CERN Multimedia

    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...

  11. A Bi-Directional Refinement Algorithm for the Calculus of (Co)Inductive Constructions

    CERN Document Server

    Asperti, Andrea; Coen, Claudio Sacerdoti; Tassi, Enrico

    2012-01-01

    The paper describes the refinement algorithm for the Calculus of (Co)Inductive Constructions (CIC) implemented in the interactive theorem prover Matita. The refinement algorithm is in charge of giving a meaning to the terms, types and proof terms directly written by the user or generated by using tactics, decision procedures or general automation. The terms are written in an "external syntax" meant to be user friendly that allows omission of information, untyped binders and a certain liberal use of user defined sub-typing. The refiner modifies the terms to obtain related well typed terms in the internal syntax understood by the kernel of the ITP. In particular, it acts as a type inference algorithm when all the binders are untyped. The proposed algorithm is bi-directional: given a term in external syntax and a type expected for the term, it propagates as much typing information as possible towards the leaves of the term. Traditional mono-directional algorithms, instead, proceed in a bottom-up way by inferring...

  12. Longitudinal force measurement in continuous welded rail with bi-directional FBG strain sensors

    Science.gov (United States)

    Wang, Ping; Xie, Kaize; Shao, Liyang; Yan, Lianshan; Xu, Jingmang; Chen, Rong

    2016-01-01

    In this work, a new method has been proposed to accurately determine longitudinal force measurement in continuous welded rail (CWR) with bi-directional fiber Bragg grating (B-FBGs) strain sensors (vertically and longitudinally installed according to the axis of rail). The response of B-FBGs has been theoretically analyzed by binding on CWR under different restrained conditions, where the coefficient of strain sensitivity of FBG is calibrated by its temperature sensitivity. Then the proposed sensor structure has been installed at two elaborately selected points on the subgrade on a Chinese high-speed railway in field. The experiment lasts for about 23 h. During the experiment, the rail temperature varied by about 7.8 °C and the differentials of relative value of wavelength change of B-FBGs of two points were 1.7850 × 10-5 and 1.4969 × 10-5. The maximum difference between the experimental and theoretical results is 13.8 kN. The experimental results agree with the theoretical analysis very well. To guarantee the measurement accuracy of over 95%, the ratio of strain sensitivity coefficients of two FBG sensors of B-FBGs structure at one test point shall be within 0.78 ˜ 1.22.

  13. Bi-directional modulation of AMPA receptor unitary conductance by synaptic activity

    Directory of Open Access Journals (Sweden)

    Matthews Paul

    2004-11-01

    Full Text Available Abstract Background Knowledge of how synapses alter their efficiency of communication is central to the understanding of learning and memory. The most extensively studied forms of synaptic plasticity are long-term potentiation (LTP and its counterpart long-term depression (LTD of AMPA receptor-mediated synaptic transmission. In the CA1 region of the hippocampus, it has been shown that LTP often involves a rapid increase in the unitary conductance of AMPA receptor channels. However, LTP can also occur in the absence of any alteration in AMPA receptor unitary conductance. In the present study we have used whole-cell dendritic recording, failures analysis and non-stationary fluctuation analysis to investigate the mechanism of depotentiation of LTP. Results We find that when LTP involves an increase in unitary conductance, subsequent depotentiation invariably involves the return of unitary conductance to pre-LTP values. In contrast, when LTP does not involve a change in unitary conductance then depotentiation also occurs in the absence of any change in unitary conductance, indicating a reduction in the number of activated receptors as the most likely mechanism. Conclusions These data show that unitary conductance can be bi-directionally modified by synaptic activity. Furthermore, there are at least two distinct mechanisms to restore synaptic strength from a potentiated state, which depend upon the mechanism of the previous potentiation.

  14. Bi-directional Effects of Peer Relationships and Adolescent Substance Use: A Longitudinal Study.

    Science.gov (United States)

    McDonough, Meghan H; Jose, Paul E; Stuart, Jaimee

    2016-08-01

    Understanding the predictors of the onset and maintenance of substance use in adolescence is important because it is a recognized health risk. The present longitudinal study examined whether negative peer influence and peer connectedness predicted changes in adolescent alcohol, cigarette, marijuana, and other illegal drug use, and reciprocally whether substance use predicted changes in peer relationships. Adolescents (N = 1940; 52 % female; 52 % European New Zealanders, 30 % Maori, 12 % Pacific Islander) aged 10-15 years completed measures annually for 3 years. Cross-lagged panel models were used to examine bi-directional effects. Negative peer influence predicted increased use of all substances. In turn, alcohol, cigarette, and marijuana use predicted increased negative peer influence, but this effect was inconsistent over time. Peer connectedness, predicted to diminish the frequency of substance use, was found to be unrelated to it. Breaking the reciprocal cycle between peer coercion and substance use would seem to be useful for reducing substance use. PMID:26391360

  15. Development of an Advanced Flow Meter using the Averaging Bi-directional Flow Tube

    International Nuclear Information System (INIS)

    Advanced flow meter using the concept of averaging bi-directional flow tube was developed. To find characteristics of flow meter and derive theory of measurement in the single and two phase flow condition, some basic tests were attempted using flow meters with diameters of 27, 80 and 200 mm. The CFD(computational fluid dynamics) calculation was also performed to find the effects of temperature and pressure, and to optimize design of a prototypic flow meter. Following this procedure, prototypical flow meters with diameters of 200 and 500 mm were designed and manufactured. It is aimed to use in the region in which calibration constant was unchanged. The stress analysis showed that the proposed flow meter of H-beam shape is inherently strong against the bending force induced by flow. The flow computer was developed for the flow rate calculation from the measured pressure difference. In this study, the performance test using this prototype flow meter was carried out. The developed flow meter can be applied in the wide range of pressure and temperature. The basic tests showed that the lineality of the proposed flow meter is ± 0.5 % of full scale and flow turn down ratio is 1:20 where the Reynolds number is larger than 10,000

  16. Current understanding of the bi-directional relationship of major depression with inflammation

    Directory of Open Access Journals (Sweden)

    Messay Berhane

    2012-02-01

    Full Text Available Abstract Consistent evidence links major depression and its affective components to negative health outcomes. Although the pathways of these effects are likely complex and multifactorial, recent evidence suggests that innate inflammatory processes may play a role. An overview of current literature suggests that pathways between negative moods and inflammation are bi-directional. Indeed, negative moods activate peripheral physiologic mechanisms that result in an up regulation of systemic levels of inflammation. Conversely, peripheral inflammatory mediators signal the brain to affect behavioral, affective and cognitive changes that are consistent with symptoms of major depressive disorder. It is likely that these pathways are part of a complex feedback loop that involves the nervous, endocrine, and immune systems and plays a role in the modulation of peripheral inflammatory responses to central and peripheral stimuli, in central responses to peripheral immune activation and in the maintenance of homeostatic balance. Further research is warranted to fully understand the role of central processes in this feedback loop, which likely contributes to the pathophysiology of mental and physical health.

  17. Possible bi-directional link between ETA receptors and protein kinase C in rat blood vessels

    Directory of Open Access Journals (Sweden)

    A. M. Northover

    1995-01-01

    Full Text Available Possible links have been investigated between activation of protein kinase C (PKC and endothelin (ET production by small blood vessels. Perfusion pressures were recorded from rat isolated mesenteric artery, with or without the small intestine attached, before and after addition to the perfusate of either ET-1, ET-3 or the PKC activator 12-deoxyphorbol 13-phenylacetate (DOPPA. Rises in perfusion pressure in response to ET-1 (10−8 Mor DOPPA (10−6 M were reduced significantly by pre-treatment with either the ETA receptor antagonist PD151242 (10−6 M or the PKC inhibitor Ro 31-8220 (10−6 M. ET-3 (10−8 M had a significant, albeit small, effect only when the gut was still attached to the mesentery. Inthis latter preparation ET-1 and DOPPA increased the permeability of villi microvessels to colloidal carbon in the perfusate. This effect of DOPPA was reduced by pre-treatment with either PD151242 or Ro 31-8220, but the effects of ET-1 were reduced significantly only by Ro 31-8220. ET-3 (10−8 M was without effect. The results suggest a possible bi-directional link between ETA receptors and PKC in the intestinal vasculature.

  18. Efficient Parallel and Out of Core Algorithms for Constructing Large Bi-directed de Bruijn Graphs

    CERN Document Server

    Kundeti, Vamsi; Dinh, Hieu

    2010-01-01

    Assembling genomic sequences from a set of overlapping reads is one of the most fundamental problems in computational biology. Algorithms addressing the assembly problem fall into two broad categories -- based on the data structures which they employ. The first class uses an overlap/string graph and the second type uses a de Bruijn graph. However with the recent advances in short read sequencing technology, de Bruijn graph based algorithms seem to play a vital role in practice. Efficient algorithms for building these massive de Bruijn graphs are very essential in large sequencing projects based on short reads. In Jackson et. al. ICPP-2008, an $O(n/p)$ time parallel algorithm has been given for this problem. Here $n$ is the size of the input and $p$ is the number of processors. This algorithm enumerates all possible bi-directed edges which can overlap with a node and ends up generating $\\Theta(n\\Sigma)$ messages. In this paper we present a $\\Theta(n/p)$ time parallel algorithm with a communication complexity e...

  19. Low frequency radio observations of bi-directional electron beams in the solar corona

    CERN Document Server

    Carley, Eoin P; Vilmer, Nicole; Gallagher, Peter T

    2015-01-01

    The radio signature of a shock travelling through the solar corona is known as a type II solar radio burst. In rare cases these bursts can exhibit a fine structure known as `herringbones', which are a direct indicator of particle acceleration occurring at the shock front. However, few studies have been performed on herringbones and the details of the underlying particle acceleration processes are unknown. Here, we use an image processing technique known as the Hough transform to statistically analyse the herringbone fine structure in a radio burst at $\\sim$20-90 MHz observed from the Rosse Solar-Terrestrial Observatory on 2011 September 22. We identify 188 individual bursts which are signatures of bi-directional electron beams continuously accelerated to speeds of 0.16$_{-0.10}^{+0.11} c$. This occurs at a shock acceleration site initially at a constant altitude of $\\sim$0.6 R$_{\\odot}$ in the corona, followed by a shift to $\\sim$0.5 R$_{\\odot}$. The anti-sunward beams travel a distance of 170$_{-97}^{+174}$ ...

  20. Low Frequency Radio Observations of Bi-directional Electron Beams in the Solar Corona

    Science.gov (United States)

    Carley, E.; Reid, H.; Vilmer, N.; Gallagher, P.

    2015-12-01

    The radio signature of a shock travelling through the solar corona is known as a type II solar radio burst. In rare cases, these bursts can exhibit a fine structure known as 'herringbones' which are a direct indicator of particle acceleration occurring at the shock front. However, few studies have been performed on herringbones and the details of the underlying particle acceleration processes are unknown. Here, we use an image processing technique known as the Hough transform to statistically analyse the herringbone fine structure in a radio burst at 20-90MHz observed from the Rosse Solar-Terrestrial Observatory on 2011 September 22. We identify 188 individual bursts which are signatures of bi-directional electron beams continuously accelerated to speeds of 0.16 c. This occurs at a shock acceleration site initially at a constant altitude of 0.6 Rsun in the corona, followed by a shift to 0.5 Rsun. The anti-sunward beams travel a distance of 170 Mm (and possibly further) away from the acceleration site, while those travelling toward the sun come to a stop sooner, reaching a smaller distance of 112 Mm. We show that the stopping distance for the sunward beams may depend on the total number density and the velocity of the beam. Our study concludes that a detailed statistical analysis of herringbone fine structure can provide information on the physical properties of the corona which lead to these relatively rare radio bursts.

  1. 4x10Gb/s WDM Bi-directional Gating in a Semiconductor Optical Amplifier by Using Polarization Multiplexing Technique

    DEFF Research Database (Denmark)

    Yu, Jianjun; Jeppesen, Palle

    2000-01-01

    Bi-directional SOA gating can further reduce the number of gating elements in the space switch, we demonstrate that a conventional SOA employing polarization multiplexing technique (PMT) can be used for bi-directional WDM gating operation at 10Gb/s....

  2. 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......-convex problem and we introduce a low-complexity iterative solution, as well as derive a sum-rate upper performance bound. Numerical results demonstrate an obvious benefit from the usage of multiple antennas at the relay node....

  3. TWO-WAY DENOISE-AND-FORWARD NETWORK CODING OPPORTUNISTIC RELAYING AIMING AT MINIMIZING EUCLIDEAN DISTANCE IN MULTI-ACCESS PHASE

    Institute of Scientific and Technical Information of China (English)

    Jia Xiangdong; Yang Longxiang; Shao Shixiang

    2011-01-01

    To exploit the effect of modulation schemes on the best relay selection,a novel Jointing Modulation schemes max-min criterion (JM-max-min) is proposed firstly for Two-Way DeNoise-and-Forward (DNF) Opportunistic Relaying systems (TW-DNF-OR) by aiming at minimizing the Pairwise Error Probability (PEP) of Multi-Access (MA) phase which dominates the error performance of TW-DNF-OR due to the presence of MA interference.The proposed JM-max-min criterion integrates perfectly the minimum distances of constellations and the relay links gains.Then,with the proposed JM-max-min criterion,we analyze the Symbol Error Probabilities (SEPs) of MA phase and BroadCast (BC) phase by using the approximated mathematics analysis,and present the corresponding closed-form expressions to SEPs.The numerical analysis shows,for a given modulations combination at both sources,the TW-DNF-OR systems with the proposed JM-max-min criterion outperform the one with the conventional max-min criterion.

  4. Review and parameterisation of bi-directional ammonia exchange between vegetation and the atmosphere

    Directory of Open Access Journals (Sweden)

    R.-S. Massad

    2010-11-01

    Full Text Available Current deposition schemes used in atmospheric chemical transport models do not generally account for bi-directional exchange of ammonia (NH3. Bi-directional exchange schemes, which have so far been applied at the plot scale, can be included in transport models, but need to be parameterised with appropriate values of the ground layer compensation point (χg, stomatal compensation point (χs and cuticular resistance (Rw. We review existing measurements of χg, χs as well as Rw and compile a comprehensive dataset from which we then propose generalised parameterisations. χs is related to Γs, the non-dimensional ratio of [NH4+]apo and [H+]apo in the apoplast, through the temperature dependence of the combined Henry and dissociation equilibrium. The meta-analysis suggests that the nitrogen (N input is the main driver of the apoplastic and bulk leaf concentrations of ammonium (NH4 apo, NH4 bulk. For managed ecosystems, the main source of N is fertilisation which is reflected in a peak value of χs a few days following application, but also alters seasonal values of NH4 apo and NH4 bulk. We propose a parameterisation for χs which includes peak values as a function of amount and type of fertiliser application which gradually decreases to a background value. The background χs is based on total N input to the ecosystem as a yearly fertiliser application and N deposition (Ndep. For non-managed ecosystems, χs is parameterised based solely on the link with Ndep.

    For Rw we propose a general parameterisation as a function of atmospheric relative humidity (RH, incorporating a minimum value (

  5. Review and parameterisation of bi-directional ammonia exchange between vegetation and the atmosphere

    Directory of Open Access Journals (Sweden)

    R.-S. Massad

    2010-04-01

    Full Text Available Current deposition schemes used in atmospheric chemical transport models do not generally account for bi-directional exchange of ammonia (NH3. Bi-directional exchange schemes, which have so far been applied at the plot scale, can be included in transport models, but need to be parameterised with appropriate values of the stomatal compensation point (χs and cuticular resistance (Rw. We here review existing measurements of χs as well as Rw and compile a comprehensive dataset from which we then propose generalised parameterisations. χs is related to Γs, the non-dimensional ratio of [NH4+]apo and [H+]apo in the apoplast, through the temperature dependence of the combined Henry and solubility equilibrium. The meta-analysis suggests that the nitrogen (N input is the main driver of the apoplastic and bulk leaf concentrations of ammonium (NH+4 apo, NH+4 bulk. For managed ecosystems, the main source of N is fertilisation which is reflected in a peak value of χs a few days following application, but also alters seasonal values of NH+4 apo and NH+4 bulk. We propose a parameterisation for χs which includes peak values as a function of amount and type of fertiliser application which gradually decreases to a background value. The background χs is set based on total N input to the ecosystem as a yearly fertiliser application and N deposition (Ndep. For non-managed ecosystems, χs is parameterised based solely on the link with Ndep.

    For Rw we propose a general parameterisation as a function of atmospheric Relative Humidity (RH, incorporating a minimum value (R w(min, which depends on the ratio of atmospheric acid

  6. Bi-Directional Tuning of Amygdala Sensitivity in Combat Veterans Investigated with fMRI.

    Directory of Open Access Journals (Sweden)

    Tom Brashers-Krug

    Full Text Available Combat stress can be followed by persistent emotional consequences. It is thought that these emotional consequences are caused in part by increased amygdala reactivity. It is also thought that amygdala hyper-reactivity results from decreased inhibition from portions of the anterior cingulate cortex (ACC in which activity is negatively correlated with activity in the amygdala. However, experimental support for these proposals has been inconsistent.We showed movies of combat and civilian scenes during a functional magnetic resonance imaging (fMRI session to 50 veterans of recent combat. We collected skin conductance responses (SCRs as measures of emotional arousal. We examined the relation of blood oxygenation-level dependent (BOLD signal in the amygdala and ACC to symptom measures and to SCRs.Emotional arousal, as measured with SCR, was greater during the combat movie than during the civilian movie and did not depend on symptom severity. As expected, amygdala signal during the less-arousing movie increased with increasing symptom severity. Surprisingly, during the more-arousing movie amygdala signal decreased with increasing symptom severity. These differences led to the unexpected result that amygdala signal in highly symptomatic subjects was lower during the more-arousing movie than during the less-arousing movie. Also unexpectedly, we found no significant inverse correlation between any portions of the amygdala and ACC. Rather, signal throughout more than 80% of the ACC showed a strong positive correlation with signal throughout more than 90% of the amygdala.Amygdala reactivity can be tuned bi-directionally, either up or down, in the same person depending on the stimulus and the degree of post-traumatic symptoms. The exclusively positive correlations in BOLD activity between the amygdala and ACC contrast with findings that have been cited as evidence for inhibitory control of the amygdala by the ACC. The conceptualization of post

  7. Diversity of MIMO Multihop Relay Channels

    CERN Document Server

    Yang, Sheng

    2007-01-01

    We consider slow fading relay channels with a single multi-antenna source-destination terminal pair. The source signal arrives at the destination via N hops through N-1 layers of relays. We analyze the diversity of such channels with fixed network size at high SNR. In the clustered case where the relays within the same layer can have full cooperation, the cooperative decode-and-forward (DF) scheme is shown to be optimal in terms of the diversity-multiplexing tradeoff (DMT). The upper bound on the DMT, the cut-set bound, is attained. In the non-clustered case, we show that the naive amplify-and-forward (AF) scheme has the maximum multiplexing gain of the channel but is suboptimal in diversity, as compared to the cut-set bound. To improve the diversity, space-time relay processing is introduced through the parallel partition of the multihop channel. The idea is to let the source signal go through K different "AF paths" in the multihop channel. This parallel AF scheme creates a parallel channel in the time domai...

  8. 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.

  9. A bi-directional DC/DC converter for hybrid wind generator/battery system with state machine control

    Energy Technology Data Exchange (ETDEWEB)

    Hua, C.C.; Liao, Y.C. [National Yunlin Univ. of Science and Technology, Yunlin, Taiwan (China). Dept. of Electrical Engineering

    2008-07-01

    A bi-directional DC to DC converter used in a hybrid wind generator/lead-acid battery power system was presented. A state machine control strategy was used to control both the system power flow and load distribution. It was also used to increase the power capacity of the system. The battery was also charged or discharged through the bi-directional DC to DC converter. Multi-stage current charging control of the batteries was accomplished by adjusting the duty cycle of the power converter. This also improved the charging efficiency by the maximum power point tracking algorithm. It was concluded that the proposed control method can be readily extended to other renewable energy conversion systems. 6 refs., 13 figs.

  10. Relay-Aided Decentralized Estimation in Wireless Sensor Networks%无线传感器网络下中继辅助的分布式估计策略

    Institute of Scientific and Technical Information of China (English)

    黄振; 温志刚; 乐光新

    2009-01-01

    The decentralized estimation of a noise-corrupted deterministic parameter in wireless sensor networks with the aid of relay is considered. A new relay-aided decentralized estimation (RADE) scheme is proposed, by which relay collects the overheard messages from sensors and sends the locally processed message to a destination. Amplify-and-forward (AF) and estimate-and-forward (EF) strategies are proposed and the corresponding closed-form solutions are derived. Numerical simulation shows the proposed strategies can provide better estimation performance without any bandwidth loss.%与传统的星形拓扑结构下无中继辅助估计策略相比,新颖的中继辅助分布式参数估计(RADE)策略能利用中继节点协作传输,提高系统估计性能,对传输能量和处理能力受限的无线传感器网络有极大帮助.根据中继节点的信号处理方式,分为放大转发(AF)和估计转发(EF)2种中继辅助分布式估计策略.通过凸优化算法得到上述2种估计策略的闭式解.仿真结果表明,此策略能在不额外占用带宽的情况下提供更好的估计性能.

  11. Advanced relay selection schemes for cooperative communications

    OpenAIRE

    Seyfi, Mehdi

    2013-01-01

    It is widely considered that cooperative diversity, in idealized conditions, can provide dramatic performance improvements in capacity and error probability. But non-ideal phenomena, such as fast time variations of the channel, channel estimation errors (CEE), feedback delay (FD) and co-channel interference, degrade the performance of the cooperative communication networks. This thesis studies the impact of these phenomena on advanced relay selection techniques in cooperative communication ne...

  12. 智能配电网信息物理融合保护系统的研究%Study on cyber-physical relaying protection system of intelligent distribution network

    Institute of Scientific and Technical Information of China (English)

    庄伟; 牟龙华

    2012-01-01

    In order to realize a deeper fusion of the protection information of relay system in intelligent distribution network, the concept of cyber-physical system (CPS) which features a close integration of computational and physical elements is introduced. By applying this characteristic, a new cyber-physical distribution network relaying protection system which consists of embedded computation device, real-time communication network, electronic transformer and intelligent switching device is proposed. The function and structure of each unit are elaborated. The basic structure, function and key technology of the proposed system are discussed. At last, the differences between the execution modes of over-current protection and fault line detection in conventional and cyber-physical distribution network relaying protection system are expounded. And advantages of the new proposed system on executing complex protection algorithms are discussed.%为了实现智能配电网中继电保护系统信息在更深层次上的融合,引入信息物理融合系统(Cyber-Physical System,CPS)的概念,借助其计算机网络与物理系统紧密结合特点,提出了由嵌入式计算设备,实时通信网络、电子式互感器以及智能开关设备组成的智能配电网信息物理融合保护系统.阐述了系统各个组成部分的功能及结构,给出该系统的基本结构并讨论了其功能与关键技术.探讨了智能配电网信息物理融合保护系统中与传统继电保护系统中过流与选线保护执行方式的区别及其优势所在.

  13. 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.

  14. Performance assessment of bi-directional knotless tissue-closure devices in juvenile Chinook salmon surgically implanted with acoustic transmitters

    Energy Technology Data Exchange (ETDEWEB)

    Woodley, Christa M.; Wagner, Katie A.; Bryson, Amanda J.; Eppard, Matthew B.

    2013-07-02

    Acoustic transmitters used in survival and telemetry studies are often surgically implanted in fish. While this is a well-established method, it has the potential to affect health, behavior, and survival, thus affecting study results. Much research has been done to try to minimize the harmful effects caused by the transmitter and tagging process. In 2009, we first investigated the use of a bi-directional knotless (barbed) suture material in juvenile Chinook salmon (Oncorhynchus tshawytscha). We found that it resulted in higher tag retention than the simple interrupted suture pattern; however, the occurrence of ulceration and redness increased. The objective of this study was to refine the suturing patterns of the bi-directional knotless suture and retest suture performance in juvenile Chinook salmon. We tested the bi-directional suture using 3 different suture patterns and two needle types: 6-Point (12-mm needle circumference), Wide “N” (12-mm needle circumference), Wide “N” Knot 12 (12-mm needle circumference), and Wide “N” Knot 18 (18-mm needle circumference).

  15. 面向火星临近空间的分布式中继纠删编码机制研究%Research on Distributed Relay Erasure Codes in Mars Proximity Network

    Institute of Scientific and Technical Information of China (English)

    李云鹤; 顾术实; 焦健; 于淼; 吴绍华; 张钦宇

    2013-01-01

    Data transmission from Mars rovers to deep space stations need to be relayed by Mars orbiters and construct a Mars Proximity Network (MPN),due to the extremely far distance and occultation of planets in Mars exploration communications.In order to guarantee the reliability of data communication and enhance the efficiency of data transmission,the sense of multi-rovers transmitting data from an orbiter to earth stations is researched based on distributed relay erasure codes.Considering the periodic and frequent arrival and departure of nodes in MPN,a random decision relaying scheme (RDRS) is proposed,in which source nodes are used to generate Weaken Robust Soliton Wave Luby Transform codes,and randomly forward/XOR symbols are relayed from two Source nodes to an earth station.Simulation results show that,both proposed RDRS and improved RDRS schemes can achieve decoding success rate of 99.9% with only encoding overhead of 50% compared with existing distributed fountain code scheme.%火星探测极远的通信距离以及行星遮挡,使得探测车与地面站的通信需要构建火星临近空间网络传输信息.为保证数据传输的可靠性并提高传输效率,重点研究基于分布式前向纠删编码的多个火星探测车通过中继轨道器向地面站传输的场景.考虑探测节点的周期性加入和退出的特性,设计了源节点使用弱鲁棒孤波LT码,中继随机转发/异或的中继随机决策编码方案,并推导了转发概率的理论最优值.仿真验证了新方案与已有的分布式喷泉方案相比,降低了约50%的信源编码开销,并通过复杂度与译码冗余的折衷,达到了99.9%的译码成功率.

  16. 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,...

  17. Performance Analysis of Relays in LTE for a Realistic Suburban Deployment Scenario

    DEFF Research Database (Denmark)

    Coletti, Claudio; Mogensen, Preben; Irmer, Ralf

    2011-01-01

    -effectiveness have been widely investigated in the literature, considering mainly statistical deployment scenarios, like regular networks with uniform traffic distribution. This paper is envisaged to illustrate the performances of different relay technologies (In-Band/Out-band) in a realistic suburban network......Relays are likely to play an important role in the deployment of Beyond 3G networks, such as LTE-Advanced, thanks to the possibility of effectively extending Macro network coverage and fulfilling the expected high data-rate requirements. Up until now, the relay technology potential and its cost...... of a lower frequency carrier at the Macro layer guarantee better network coverage and capacity improvements....

  18. 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.

  19. Error-rate performance analysis of opportunistic regenerative relaying

    KAUST Repository

    Tourki, Kamel

    2011-09-01

    In this paper, we investigate an opportunistic relaying scheme where the selected relay assists the source-destination (direct) communication. In our study, we consider a regenerative opportunistic relaying scheme in which the direct path can be considered unusable, and takes into account the effect of the possible erroneously detected and transmitted data at the best relay. We first derive the exact statistics of each hop, in terms of probability density function (PDF). Then, the PDFs are used to determine accurate closed form expressions for end-to-end bit-error rate (BER) of binary phase-shift keying (BPSK) modulation where the detector may use maximum ration combining (MRC) or selection combining (SC). Finally, we validate our analysis by showing that performance simulation results coincide with our analytical results over linear network (LN) architecture and considering Rayleigh fading channels. © 2011 IEEE.

  20. Accurate Performance Analysis of Opportunistic Decode-and-Forward Relaying

    CERN Document Server

    Tourki, Kamel; Alouni, Mohamed-Slim

    2011-01-01

    In this paper, we investigate an opportunistic relaying scheme where the selected relay assists the source-destination (direct) communication. In our study, we consider a regenerative opportunistic relaying scheme in which the direct path can be considered unusable, and takes into account the effect of the possible erroneously detected and transmitted data at the best relay. We first derive statistics based on exact probability density function (PDF) of each hop. Then, the PDFs are used to determine accurate closed form expressions for end-to-end bit-error rate (BER) of binary phase-shift keying (BPSK) modulation. Furthermore, we evaluate the asymptotical performance analysis and the diversity order is deduced. Finally, we validate our analysis by showing that performance simulation results coincide with our analytical results over different network architectures.

  1. New results on performance analysis of opportunistic regenerative relaying

    KAUST Repository

    Tourki, Kamel

    2013-12-01

    In this paper, we investigate an opportunistic relaying scheme where the selected relay assists the source-destination (direct) communication. In our study, we consider a regenerative opportunistic relaying scheme in which the direct path may be unusable, and takes into account the effect of the possible erroneously detected and transmitted data at the selected relay. We first derive the signal-to-noise (SNR) statistics for each hop, which are used to determine accurate closed form expressions for end-to-end bit-error rate (BER) of binary phase-shift keying (BPSK) modulation and end-to-end outage probability for a transmission rate R over Rayleigh fading channels. Furthermore, we evaluate the asymptotical performance and deduce the diversity order. Finally, we validate our analysis by showing that performance simulation results coincide with our analytical results over linear network architecture. © 2013 Elsevier B.V.

  2. 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.

  3. Multihop Relay Techniques for Communication Range Extension in Near-Field Magnetic Induction Communication Systems

    Directory of Open Access Journals (Sweden)

    Mehrnoush Masihpour

    2013-05-01

    Full Text Available In this paper, multihop relaying in RF-based communications and near field magnetic induction communication (NFMIC is discussed. Three multihop relay strategies for NFMIC are proposed: Non Line of Sight Magnetic Induction Relay (NLoS-MI Relay, Non Line of Sight Master/Assistant Magnetic Induction Relay1 (NLoS-MAMI Relay1 and Non Line of Sight Master/Assistant Magnetic Induction Relay2 (NLoSMAMI Relay2. In the first approach only one node contributes to the communication, while in the other two techniques (which are based on a master-assistant strategy, two relaying nodes are employed. This paper shows that these three techniques can be used to overcome the problem of dead spots within a body area network and extend the communication range without increasing the transmission power and the antenna size or decreasing receiver sensitivity. The impact of the separation distance between the nodes on the achievable RSS and channel data rate is evaluated for the three techniques. It is demonstrated that the technique which is most effective depends on the specific network topology. Optimum selection of nodes as relay master and assistant based on the location of the nodes is discussed. The paper also studies the impact of the quality factor on achievable data rate. It is shown that to obtain the highest data rate, the optimum quality factor needs to be determined for each proposed cooperative communication method.

  4. Advanced relay technologies in next generation wireless communications

    CERN Document Server

    Krikidis, Ioannis

    2016-01-01

    This book details the use of the cooperative networks/relaying approach in new and emerging telecommunications technologies such as full-duplex radio, massive multiple-input multiple-output (MIMO), network coding and spatial modulation, and new application areas including visible light communications (VLC), wireless power transfer, and 5G.

  5. 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.  

  6. 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

  7. Proactive Relay Selection with Joint Impact of Hardware Impairment and Co-channel Interference

    OpenAIRE

    Duy, Tran Trung; Duong, Trung Q.; da Costa, Daniel Benevides; Bao, Vo Ngyugen Quoc; Elkashlan, Maged

    2015-01-01

    In this paper, we investigate the end-to-end performance of dual-hop proactive decode-and-forward relaying networks with Nth best relay selection in the presence of two practical deleterious effects: i) hardware impairment and ii) cochannel interference. In particular, we derive new exact and asymptotic closed-form expressions for the outage probability and average channel capacity of Nth best partial and opportunistic relay selection schemes over Rayleigh fading channels. Insightful discussi...

  8. Projecting Ammonia Dry Deposition Using Passive Samplers and a Bi-Directional Exchange Model

    Science.gov (United States)

    Robarge, W. P.; Walker, J. T.; Austin, R. E.

    2011-12-01

    Animal agriculture within the United States is known to be a source of ammonia (NH3) emissions. Dry deposition of NH3 to terrestrial ecosystems immediately surrounding large local sources of NH3 emissions (e.g. animal feeding operations) is difficult to measure, and is best estimated via models. Presented here are results for a semi-empirical modeling approach for estimating air-surface exchange fluxes of NH3 downwind of a large poultry facility (~ 3.5 million layers) using a bi-directional air-surface exchange model. The modeling domain is the western section of the Pocosin Lakes National Wildlife Refuge in Tyrrell, Washington, and Hyde Counties of eastern North Carolina in the South Atlantic Coastal Plain physiographic region. Vegetation within the modeling domain is primarily pocosin wetlands, characterized by acid (pH 3.6) peat soils and a thick canopy of shrub vegetation (leatherwood (Cyrilla racemiflora), inkberry (Ilex glabra), wax myrtle (Morella cerifera)). Land surrounding the refuge is primarily used for crop production: ~ 28%, 24%, and 45% agricultural in Tyrell, Hyde, and Washington counties, respectively. Ammonia air-surface exchange (flux) was calculated using a two-layer canopy compensation point model developed by Nemitz et al. (2001. Quart. J. Roy. Met. Soc. 127, 815 - 833.) as implemented by Walker et al. (2008. Atmos. Environ., 42, 3407 - 3418.), in which the competing processes of emission and deposition within the foliage-soil system were taken into account by relating the net canopy-scale NH3 flux to the net emission potential of the canopy (i.e., foliage and soil). Ammonia air concentrations were measured using ALPHA passive samplers (Center for Ecology and Hydrology, Edinburgh) along transects to the north and northeast of the poultry facility at distances of 800, 2000 and 3200 m, respectively. Samplers were deployed in duplicate at each location at a height of 5.8 m from July 2008 to July 2010 weekly during warm months and bi-weekly curing

  9. Laboratory characterization of a CCD camera system for retrieval of bi-directional reflectance distribution function

    Science.gov (United States)

    Nandy, Prabal; Thome, Kurtis J.; Biggar, Stuart F.

    1999-12-01

    The Remote Sensing Group of the Optical Science Center at the University of Arizona has developed a four-band, multi- spectral, wide-angle, imaging radiometer for the retrieval of the bi-directional reflectance distribution function (BRDF) for vicarious calibration applications. The system consists of a fisheye lens with four interference filters centered at 470 nm, 575 nm, 660 nm, and 835 nm for spectral selection and an astronomical grade 1024 X 1024-pixel, silicon CCD array. Data taken by the system fit in the array as a nominally 0.2 degree per pixel image. This imaging radiometer system has been used in support of the calibration of Landsat-5 and SPOT- satellite sensors. This paper presents the results of laboratory characterization of the system to determine linearity of the detector, point spread function (PSF) and polarization effects. The linearity study was done on detector array without the lens, using a spherical-integrating source with a 1.5-mm aperture. This aperture simulates a point source for distances larger than 60 cm. Data were collected as both a function of exposure time and distance from the source. The results of these measurements indicate that each detector of the array is linear to better than 0.5%. Assuming a quadratic response improves this fit to better than 0.1% over 88% of the upper end of the detector's dynamic range. The point spread function (PSF) of the lens system was measured using the sphere source and aperture with the full camera system operated at a distance of 700 mm from the source, thus the aperture subtends less than the field of view of one pixel. The PSF was measured for several field angles and the signal level was found to fall to less than 1% of the peak signal within 1.5-degrees (10 pixels) for the on-axis case. The effect of this PSF on the retrieval of modeled BRDFs is shown to be less than 0.2% out to view angles of 70 degrees. The final test presented is one to assess the polarization effects of the lens

  10. Ultra-High Voltage 4H-SiC Bi-Directional Insulated Gate Bipolar Transistors

    Science.gov (United States)

    Chowdhury, Sauvik

    4H- Silicon Carbide (4H-SiC) is an attractive material for power semiconductor devices due to its large bandgap, high critical electric field and high thermal conductivity compared to Silicon (Si). For ultra-high voltage applications (BV > 10 kV), 4H-SiC Insulated Gate Bipolar Transistors (IGBTs) are favored over unipolar transistors due to lower conduction losses. With improvements in SiC materials and processing technology, promising results have been demonstrated in the area of conventional unidirectional 4H-SiC IGBTs, with breakdown voltage ratings up to 27 kV. This research presents the experimental demonstration of the world's first high voltage bi-directional power transistors in 4H-SiC. Traditionally, four (two IGBTs and two diodes) or two (two reverse blocking IGBTs) semiconductor devices are necessary to yield a bidirectional switch. With a monolithically integrated bidirectional switch as presented here, the number of semiconductor devices is reduced to only one, which results in increased reliability and reduced cost of the overall system. Additionally, by using the unique dual gate operation of BD-IGBTs, switching losses can be reduced to a small fraction of that in conventional IGBTs, resulting in increased efficiency. First, the performance limits of SiC IGBTs are calculated by using analytical methods. The performance benefits of SiC IGBTs over SiC unipolar devices and Si IGBTs are quantified. Numerical simulations are used to optimize the unit cell and edge termination structures for a 15 kV SiC BD-IGBT. The effect of different device parameters on BD-IGBT static and switching performance are quantified. Second, the process technology necessary for the fabrication of high voltage SiC BD-IGBTs is optimized. The effect of different process steps on parameters such as breakdown voltage, carrier lifetime, gate oxide reliability, SiO2-SiC interface charge density is quantified. A carrier lifetime enhancement process has been optimized for lightly doped

  11. Evaluation of a regional air-quality model with bi-directional NH3 exchange coupled to an agro-ecosystem model

    Directory of Open Access Journals (Sweden)

    J. E. Pleim

    2012-08-01

    Full Text Available Atmospheric ammonia (NH3 is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurements indicate that the air-surface exchange of NH3 is bi-directional. However, the effects of bi-directional exchange, soil biogeochemistry and human activity are not parameterized in air quality models. The US Environmental Protection Agency (EPA's Community Multiscale Air-Quality (CMAQ model with bi-directional NH3 exchange has been coupled with the United States Department of Agriculture (USDA's Environmental Policy Integrated Climate (EPIC agro-ecosystem model's nitrogen geochemistry algorithms. CMAQ with bi-directional NH3 exchange coupled to EPIC connects agricultural cropping management practices to emissions and atmospheric concentrations of reduced nitrogen and models the biogeochemical feedback on NH3 air-surface exchange. This coupled modeling system reduced the biases and error in NHx (NH3 + NH4+ wet deposition and in ambient aerosol concentrations in an annual 2002 Continental US (CONUS domain simulation when compared to a 2002 annual simulation of CMAQ without bi-directional exchange. Fertilizer emissions estimated in CMAQ 5.0 with bi-directional exchange exhibits markedly different seasonal dynamics than the US EPA's National Emissions Inventory (NEI, with lower emissions in the spring and fall and higher emissions in July.

  12. Transparent organic light-emitting diodes with different bi-directional emission colors using color-conversion capping layers

    International Nuclear Information System (INIS)

    We report a study on transparent organic light-emitting diodes (OLEDs) with different bi-directional emission colors, enabled by color-conversion organic capping layers. Starting from a transparent blue OLED with an uncapped Ag top electrode exhibiting an average transmittance of 33.9%, a 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM)-doped tris-(8-hydroxy-quinolinato)-aluminum (Alq3) capping layer is applied to achieve color-conversion from blue to orange-red on the top side while maintaining almost unchanged device transmittance. This color-conversion capping layer does not only change the color of the top side emission, but also enhances the overall device efficiency due to the optical interaction of the capping layer with the primary blue transparent OLED. Top white emission from the transparent bi-directional OLED exhibits a correlated color temperature around 6000–7000 K, with excellent color stability as evidenced by an extremely small variation in color coordinate of Δ(x,y)=(0.002, 0.002) in the forward luminance range of 100–1000 cd m−2. At the same time, the blue emission color of bottom side is not influenced by the color conversion capping layer, which finally results in different emission colors of the two opposite sides of our transparent OLEDs. - Highlights: • We report transparent organic light-emitting diodes (OLEDs) with different bi-directional emission colors. • Transparent blue OLED with color-conversion organic capping layers (CCL) shows orange top side emission. • Top white emission exhibits a CCT around 7000 K, with excellent color stability on a driving voltage

  13. Measuring bi-directional current through a field-effect transistor by virtue of drain-to-source voltage measurement

    Science.gov (United States)

    Turner, Steven Richard

    2006-12-26

    A method and apparatus for measuring current, and particularly bi-directional current, in a field-effect transistor (FET) using drain-to-source voltage measurements. The drain-to-source voltage of the FET is measured and amplified. This signal is then compensated for variations in the temperature of the FET, which affects the impedance of the FET when it is switched on. The output is a signal representative of the direction of the flow of current through the field-effect transistor and the level of the current through the field-effect transistor. Preferably, the measurement only occurs when the FET is switched on.

  14. Voz sobre frame relay

    OpenAIRE

    D´Elia, Gabriel Anibal

    2000-01-01

    Esta tesis trata el tema de VOFR, desde la digitalización de la voz hasta su transmisión a través de dicha red, así también como la comparación con otros medios de transporte como VOIP. Dada las características del protocolo frame relay y su disponibilidad se eligió como el medio más apropiado para la transmisión de voz y datos en forma integrada sobre una misma red. El trabajo comienza con una breve explicación de la voz, su digitalización y forma actual de transmisión a través de una red di...

  15. CERN Relay Race

    CERN Multimedia

    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.

  16. 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.

  17. Optimal Resource Allocation and Relay Selection in Bandwidth and Time Exchange Based Cooperative Forwarding

    CERN Document Server

    Islam, Muhammad Nazmul; Kompella, Sastry

    2011-01-01

    In this paper, we investigate joint optimal relay selection and resource allocation that are fundamental to the understanding of bandwidth exchange (BE) and time exchange (TE) enabled incentivized cooperative forwarding in wireless networks. We consider a network where N nodes transmit data in the uplink to an access point (AP) or base station (BS). We first consider the scenario where each node gets an initial amount (equal, optimal or arbitrary) of resource in the form of bandwidth or time, and uses this resource as a flexible incentive for two hop relaying. We focus on ?-fair network utility maximization (NUM) and total power minimization in this environment. For both BE and TE, we show the concavity or convexity of the resource allocation problem for a fixed relay set. Defining the link weights of each relay pair as the utility gain due to cooperation (over noncooperation), we show that the optimal relay selection, often a combinatorially cumbersome problem, reduces to the maximum weighted matching (MWM) ...

  18. Toward distributed relay selection for opportunistic amplify-and-forward transmission

    KAUST Repository

    Tourki, Kamel

    2011-05-01

    Opportunistic relaying in cooperative communication depends on careful relay selection. However the traditional centralized method used for opportunistic Amplify-and-Forward (OAF) protocols requires precise measurements of channel state information (CSI) at the destination (CSI-OAF). In this paper, we propose a distributed relay selection framework for opportunistic AF (D-OAF) cooperative communications and offer an accurate performance analysis based on exact statistics of the local signalto- noise ratios of the best relay. Furthermore, we validate our analysis by showing that performance simulation results coincide with our analytical results over different network architectures, and we compare our new results with their CSI-based counterparts. © 2011 IEEE.

  19. Behavior Prediction of Untrusted Relays Based on Nonzero-Sum Game

    Institute of Scientific and Technical Information of China (English)

    Fu Xiaomei付晓梅; Wu Xiao吴晓; Wang Qing汪清

    2015-01-01

    To keep the secrecy performance from being badly influenced by untrusted relay(UR), a multi-UR net-work through amplify-and-forward (AF) cooperative scheme is put forward, which takes relay weight and harmful factor into account. A nonzero-sum game is established to capture the interaction among URs and detection strate-gies. Secrecy capacity is investigated as game payoff to indicate the untrusted behaviors of the relays. The maxi-mum probabilities of the behaviors of relay and the optimal system detection strategy can be obtained by using the proposed algorithm.

  20. Estimation of the LTE relay influence on the cell

    Directory of Open Access Journals (Sweden)

    V. Ya. Voropayeva

    2014-06-01

    Full Text Available Problem definition. Information technologies are constantly evolving. This process leads to an annual traffic increasing. Also requirements to infocommunication nerworks are increasing too. It stimulates the development of new technologies that will be able to satisfy the growing needs of users. At the present stage of evolution of world telecommunication technologies in mobile communications development and implementation of the fourth generation standard (4G networks are relevant. This type of networks provides a higher data rate and high quality of service with an overall decrease in operating costs of telecommunications equipment. One of the most relevant technologies is Long Term Evolution (LTE, which is the development of the third generation UMTS networks. Now there is a standard of 3GPP - LTE-Advanced, which is an improvement of LTE and the official wireless communications standard of the 4th generation. Relay Nodes has appeared in LTE-Advanced networks for more effective scheduling. Relay catches the signal from a Mobile Station, amplifies it and transmit it further to a Base Station. Selecting the optimal location of relay. In this paper we consider one LTE cell and one repeater type I (in-band, half-duplex. For this type of relay we calculate the best position of installation. The calculated value of the cell radius is 400 m for densely populated city. The type of division duplex is TDD, the frame configuration is 2, the width of the frequency band is 10 MHz. To calculate the cell radius COST231 Hata s 3GPP TS 25.996 v9.0.0 model for urban macro network is used. Scheduling scheme uses an algorithm Fair Work Conserving (FWC. FWC relates to such type of algorithms that operate on a resource allocation equally between the users. Users connect to the network at the speed of λ, which may be various. Estimation of the LTE relay influence on the cell. From these simulation results, we can conclude that the larger amount of resource blocks

  1. Exploration of pathological prediction of chronic kidney diseases by a novel theory of bi-directional probability

    Science.gov (United States)

    Yang, Yuan; Luo, Min; Xiao, Li; Zhu, Xue-jing; Wang, Chang; Fu, Xiao; Yuan, Shu-guang; Xiao, Fang; Liu, Hong; Dong, Zheng; Liu, Fu-you; Sun, Lin

    2016-01-01

    In the clinic, the pathological types of chronic kidney diseases (CKD) are considered references for choosing treatment protocols. From a statistical viewpoint, a non-invasive method to predict pathological types of CKD is a focus of our work. In the current study, following a frequency analysis of the clinical indices of 588 CKD patients in the department of nephrology, a third-grade class-A hospital, a novel theory is proposed: “bi-directional cumulative probability dichotomy”. Further, two models for the prediction and differential diagnosis of CKD pathological type are established. The former indicates an occurrence probability of the pathological types, and the latter indicates an occurrence of CKD pathological type according to logistic binary regression. To verify the models, data were collected from 135 patients, and the results showed that the highest accuracy rate on membranous nephropathy (MN-100%), followed by IgA nephropathy (IgAN-83.33%) and mild lesion type (MLN-73.53%), whereas lower prediction accuracy was observed for mesangial proliferative glomerulonephritis (0%) and focal segmental sclerosis type (21.74%). The models of bi-directional probability prediction and differential diagnosis indicate a good prediction value in MN, IgAN and MLN and may be considered alternative methods for the pathological discrimination of CKD patients who are unable to undergo renal biopsy. PMID:27557856

  2. The effect of bi-directional loading on fatigue assessment of pressurized piping elbows with local thinned areas

    Energy Technology Data Exchange (ETDEWEB)

    Balan, C. [Department of Mechanical Engineering, Univeristy of Ottawa, Ottawa, Ont., KIN 6N5 (Canada); Redekop, D. [Department of Mechanical Engineering, Univeristy of Ottawa, Ottawa, Ont., KIN 6N5 (Canada)]. E-mail: dredekop@tesla.cc.uottawa.ca

    2005-03-01

    An elastic-plastic finite element study is conducted to determine the effect of bi-directional loading on the fatigue characteristics of pressurized 90 deg. piping elbows with local thinned areas. The analysis is conducted on pressurized piping elbows considered previously in the literature, but analyzed only for in-plane loading. Considering also the out-of-plane loading the present analysis seeks to simulate simultaneous horizontal and vertical seismic actions. A validation study is first conducted in which the present results obtained for in-plane loading are compared with previous results. Comparisons are made for deformation patterns, hoop strain histories, and reaction forces. The relative in-plane to out-of-plane load intensities to be adopted for the combined loading case is determined next. Results considering bi-directional loadings are then found for the pressurized piping elbow for a total of 23 cases of local area thinning. Finally conclusions are drawn about the significance of considering the additional out-of-plane loading.

  3. A new method for the measurement of two-phase mass flow rate using average bi-directional flow tube

    International Nuclear Information System (INIS)

    Average bi-directional flow tube was suggested to apply in the air/steam-water flow condition. Its working principle is similar with Pitot tube, however, it makes it possible to eliminate the cooling system which is normally needed to prevent from flashing in the pressure impulse line of pitot tube when it is used in the depressurization condition. The suggested flow tube was tested in the air-water vertical test section which has 80mm inner diameter and 10m length. The flow tube was installed at 120 of L/D from inlet of test section. In the test, the pressure drop across the average bi-directional flow tube, system pressure and average void fraction were measured on the measuring plane. In the test, fluid temperature and injected mass flow rates of air and water phases were also measured by a RTD and two coriolis flow meters, respectively. To calculate the phasic mass flow rates : from the measured differential pressure and void fraction, Chexal drift-flux correlation was used. In the test a new correlation of momentum exchange factor was suggested. The test result shows that the suggested instrumentation using the measured void fraction and Chexal drift-flux correlation can predict the mass flow rates within 10% error of measured data

  4. Cooperation of electrically stimulated muscle and pneumatic muscle to realize RUPERT bi-directional motion for grasping.

    Science.gov (United States)

    Xikai Tu; Jiping He; Yue Wen; Jian Huang; Xinhan Huang; Hailong Huang; Meng Guo; Yong Yuan

    2014-01-01

    Robot-assisted rehabilitation is an active area of research to meet the demand of repetitive therapy in stroke rehabilitation. Robotic upper-extremity repetitive trainer (RUPERT) with its unidirectional pneumatic muscle actuation (PMA) can be used by most stroke patients that have difficulty moving in one direction because of a weak agonist or hyperactive antagonist. In this research, to broaden the usage of RUPERT, we not only add grasping functionality to the rehabilitation robot with the help of surface Functional Electrical Stimulation (FES) but also realize the robot joint bi-directional motion by using a PMA in cooperation with surface FES evoked paralyzed muscle force. This integrative rehabilitation strategy is explored for training patients to practice coordinated reaching and grasping functions. The effectiveness of this FES electrically evoked bio-actuator way is verified through a method that separates the mixed electromyogram (MEMG) into the electrically evoked electromyogram (EEMG) and voluntary electromyogram (VEMG). This is a promising approach to alleviate the size and mechanical complexity of the robot, thereby the cost of the joint bi-directional actuator rehabilitation robot by means of their own characteristics of stroke subjects.

  5. Relay Implementation in WiMAX System Level Simulator

    Science.gov (United States)

    Mumtaz, Shahid; Tu, Le Thanh; Sadeghi, Rasool; Gamerio, Atilio

    Future wireless communication systems are expected to provide more stable and higher data rate transmissions in the whole network. WiMAX is one of the technologies to cover diverse geographic regions. WiMAX covers the high dense urban areas and provide access over large geographic regions in remote rural area. However, in both scenarios it is challenging to cover the entire service area. In both cases relays are foreseen to extend the range of the BS and to increase the system throughput allowing for a cost-efficient deployment and service. As multi-hop/relay has complex interactions between the routing and medium access control decisions, the extent to which analytical expressions can be used to explore its benefits are limited. Consequently simulations tend to be the preferred way of assessing the performance of relays. In this paper, we explain, how to deploy fixed-relays by using computer simulation in WiMAX system and we consistently observed that the throughput is increased and the outage is decreased in the relay-augmented WiMAX network, which is converted to range extension without any capacity penalty, for the realistic range of values of the propagation and other system parameters investigated.

  6. Relay communications strategies for Mars exploration through 2020

    Science.gov (United States)

    Edwards, C. D., Jr.; Arnold, B.; Depaula, R.; Kazz, G.; Lee, C.; Noreen, G.

    2006-07-01

    Mars exploration poses significant telecommunications challenges, including the return of large data volumes from high-resolution surface instruments, highly constrained mass, power, and energy for surface spacecraft, frequent telemetry and command sessions for supporting complex surface operations, and high-risk mission events such as entry, descent, and landing for which the capture of engineering telemetry is deemed critical. Relay telecommunication via Mars-orbiting spacecraft offers significant advantages in meeting these challenges, relative to conventional direct-to-Earth communications. NASA's Mars Global Surveyor and Mars Odyssey orbiters, along with ESA's Mars Express orbiter, represent an initial relay telecommunications infrastructure that has successfully supported the Spirit and Opportunity rovers. With the arrival of the Mars Reconnaissance Orbiter in 2006, this expanded relay network will provide key support to the 2007 Phoenix Lander and 2009 Mars Science Laboratory missions later this decade. Second-decade mission concepts will introduce new communications challenges; the provision of relay payloads on science orbiters provides a cost-effective means to sustain and evolve the Mars relay network.

  7. Implementing Strategic Planning Capabilities Within the Mars Relay Operations Service

    Science.gov (United States)

    Hy, Franklin; Gladden, Roy; Allard, Dan; Wallick, Michael

    2011-01-01

    Since the Mars Exploration Rovers (MER), Spirit and Opportunity, began their travels across the Martian surface in January of 2004, orbiting spacecraft such as the Mars 2001 Odyssey orbiter have relayed the majority of their collected scientific and operational data to and from Earth. From the beginning of those missions, it was evident that using orbiters to relay data to and from the surface of Mars was a vastly more efficient communications strategy in terms of power consumption and bandwidth compared to direct-to-Earth means. However, the coordination between the various spacecraft, which are largely managed independently and on differing commanding timelines, has always proven to be a challenge. Until recently, the ground operators of all these spacecraft have coordinated the movement of data through this network using a collection of ad hoc human interfaces and various, independent software tools. The Mars Relay Operations Service (MaROS) has been developed to manage the evolving needs of the Mars relay network, and specifically to standardize and integrate the relay planning and coordination data into a centralized infrastructure. This paper explores the journey of developing the MaROS system, from inception to delivery and acceptance by the Mars mission users.

  8. 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...

  9. Severe congestion handling approaches in NSIS RMD domains with bi-directional reservations

    NARCIS (Netherlands)

    Dimitrova, Desislava; Karagiannis, Georgios; Boer, de Pieter-Tjerk

    2008-01-01

    Real time applications usually impose strict QoS requirements on communication networks. Several QoS frameworks have been developed and standardized to satisfy these QoS requirements. Among them is the NSIS QoS framework that is currently being standardized by the NSIS (Next Steps In Signaling) work

  10. Architecture of a bi-directional Bluetooth-UPnP proxy

    NARCIS (Netherlands)

    Delphinanto, A.; Lukkien, J.J.; Koonen, A.M.J.; Hartog, F.T.H. den; Madureira, A.J.P.S.; Niemegeers, I.G.M.M.; Selgert, F.

    2007-01-01

    The current service- and device discovery protocols are not platform- and network independent Therefore, proxy servers will be needed to extend the range of IP-based discovery protocols to non-IP domains. We developed an architecture of a proxy that enables UPnP devices and services to be discovered

  11. Energy-efficient relay selection and optimal power allocation for performance-constrained dual-hop variable-gain AF relaying

    KAUST Repository

    Zafar, Ammar

    2013-12-01

    This paper investigates the energy-efficiency enhancement of a variable-gain dual-hop amplify-and-forward (AF) relay network utilizing selective relaying. The objective is to minimize the total consumed power while keeping the end-to-end signal-to-noise-ratio (SNR) above a certain peak value and satisfying the peak power constraints at the source and relay nodes. To achieve this objective, an optimal relay selection and power allocation strategy is derived by solving the power minimization problem. Numerical results show that the derived optimal strategy enhances the energy-efficiency as compared to a benchmark scheme in which both the source and the selected relay transmit at peak power. © 2013 IEEE.

  12. 76 FR 59551 - Internet-Based Telecommunications Relay Service Numbering

    Science.gov (United States)

    2011-09-27

    ... the public switched telephone network (PSTN) to the provider that had subscribed to the number and... to improve assignment of telephone numbers associated with Internet-based Telecommunications Relay... to toll free telephone numbers that is equivalent to access enjoyed by the hearing community....

  13. Bi-directional controlled release of ibuprofen and Mg(2+) from magnesium alloys coated by multifunctional composite.

    Science.gov (United States)

    Dong, Hongzhou; Li, Qing; Tan, Cui; Bai, Ningning; Cai, Peng

    2016-11-01

    Two major problems for magnesium alloy implant are the high degradation rate and easy infection associated with implantation. Herein, a surface drug delivery system (Mg/Epoxy resin-ZnO/PCL-Ibuprofen) which can realize bi-directional controlled release of ibuprofen and Mg(2+) was designed via a dip coating process followed by spraying. The in vitro test demonstrated that the ibuprofen in drug-eluting compound material showed sustained release profiles for 22days, which can effectively solve the local cellular rejection and inflammation during the early stage of implantation. Besides, the drug carrier also exhibited improved corrosion resistance duel to the high combining strength between Epoxy resin-ZnO coating and magnesium alloy, so Mg(2+) can release slowly at first and then speeded up later. This approach may be suitable for coating other implant materials such as stainless steel, titanium alloy etc. PMID:27524048

  14. Parallel input parallel output high voltage bi-directional converters for driving dielectric electro active polymer actuators

    DEFF Research Database (Denmark)

    Thummala, Prasanth; Zhang, Zhe; Andersen, Michael A. E.;

    2014-01-01

    is to design and implement driving circuits for the DEAP actuators for their use in various applications. This paper presents implementation of parallel input, parallel output, high voltage (~2.5 kV) bi-directional DC-DC converters for driving the DEAP actuators. The topology is a bidirectional flyback DC......-DC converter incorporating commercially available high voltage MOSFETs (4 kV) and high voltage diodes (5 kV). Although the average current of the aforementioned devices is limited to 300 mA and 150 mA, respectively, connecting the outputs of multiple converters in parallel can provide a scalable design....... This enables operating the DEAP actuators in various static and dynamic applications e.g. positioning, vibration generation or damping, and pumps. The proposed idea is experimentally verified by connecting three high voltage converters in parallel to operate a single DEAP actuator. The experimental results...

  15. Bi-directional terahertz-to-infrared emission from metal-coated nanostructures upon femtosecond laser irradiation.

    Science.gov (United States)

    Zhang, Liangliang; Wu, Tong; Zhao, Ji; Zhang, Cunlin; Zhang, X-C

    2015-09-21

    We report on the investigation of bi-directional terahertz-to-infrared (THz-to-IR) radiation from a metal film coated on a substrate with randomly ordered pore arrays by irradiation of femtosecond laser pulses. THz-to-IR radiation was observed both for front-side excitation (laser incident on the metal surface) and for rear-side excitation (laser incident on the substrate). In both cases, the radiation was observed both in the propagation direction of the laser beam and in the reverse direction. Considering these findings, we propose a thermal emission mechanism based on the production of surface plasmons, either delocalized (through phase-matched excitation) or localized (through surface roughness) at the air/metal and metal/substrate interfaces. PMID:26406717

  16. Improvised Security for RDF using Random Salt and Levels with Bi-Directional Translation to Relational Database

    Directory of Open Access Journals (Sweden)

    Siva Srinivasa Rao Mothukuri

    2013-12-01

    Full Text Available A Middleware Framework is required for SemanticWeb applications to access data from relational databases andlegacy storage systems, without replication or synchronization.Resource Description Framework is one such type ofmiddleware framework which bridges the gap between twoneeds. Though, there were some efforts to publish relationaldata as Resource Description Framework triples, they presentthe existing data into respective RDF stack only in Read-onlymanner, also in dearth of security. This paper accomplishes suchin vulnerabilities by enhancing a nexus to be bi-directional,allowing data updates specified as triples to be sent back to therelational database as tuples. The data can beUpdated/Inserted/Deleted wherever required. Also, this paperdeals with the Level-1 and Level-2 security hierarchy. In thosetwo levels, a random “salt” is added up to the data followed byencryption.

  17. 胃肠调节类中西药对胃肠道平滑肌的双向调节作用%Bi-directional Regulation Effect of Chinese and Western Medicines Used in Gastro-Intestine on Gastro-Intestinal Smooth Muscle

    Institute of Scientific and Technical Information of China (English)

    段煜; 张俊; 战丽彬; 林原; 唐泽耀

    2011-01-01

    在不同条件下,单味、复方中药对胃肠道平滑肌可产生双向调节作用.其可能机理为多层次网络系统的平衡调节等.从整体、离体器官、分子水平,单一、配对西药也对胃肠道平滑肌产生双向调节作用.这种双向调节作用充分体现网络系统平衡调节的整体性的哲学内涵,遵循对立统一规律辩证哲学观.%Chinese traditional sole or compound medicines may affect on gastro- intestinal smooth muscle in bi- directional regulation under different conditions. The possible mechanism may be as the balanced regulation under multi-level network system. Moreover, sole or pair western medicines also can act on the gastro-intestinal smooth muscle in bi-directional regulation in general body or isolated organ or molecular level. The bi-directional regulation fully manifestate the integrity philosophy connotation of balancing regulation in the network system, following dialectical philosophy law of the unity of opposites.

  18. Performance of hybrid-ARQ with incremental redundancy over relay channels

    KAUST Repository

    Chelli, Ali

    2012-12-01

    In this paper, we consider a relay network consisting of a source, a relay, and a destination. The source transmits a message to the destination using hybrid automatic repeat request (HARQ) with incremental redundancy (IR). The relay overhears the transmitted messages over the different HARQ rounds and tries to decode the data packet. In case of successful decoding at the relay, both the relay and the source cooperate to transmit the message to the destination. A maximum number M of HARQ rounds is considered. The channel realizations are independent for different HARQ rounds. We assume Rayleigh fading channels for the links source-relay, source-destination, and relay-destination. We investigate the performance of HARQ-IR over relay channel from an information theoretic perspective. Analytical expressions are derived for the information outage probability, the average number of transmissions, and the average transmission rate. We illustrate through our investigation the benefit of relaying. We also show the impact of the target outage probability and the maximum number M of HARQ rounds on the outage probability, the average number of transmissions, and the average transmission rate. © 2012 IEEE.

  19. Bi-Directional Fluorescence Distribution and its Correction for Estimates of Gross Ecosystem Productivity and Photosynthetic Light-Use Efficiency

    Science.gov (United States)

    Liu, Liangyun; Liu, Xinjie

    2015-04-01

    Passive measurement of solar-induced chlorophyll fluorescence (SIF) presents a new way for directly estimating the photosynthetic activities. In this study, one diurnal multi-angular spectral experiment and three independent diurnal flux experiments were carried out on winter wheat and maize to assess directional emission of SIF for estimating photosynthesis activities. Firstly, the Bi-Directional Fluorescence Distribution Function (BFDF) of SIF was investigated. A BFDF shape similar to the red Bi-Directional Reflectance Distribution Function (BRDF) was observed for the directional SIF emissions at 688 nm. Secondly, the relationship between the directional emission of canopy SIF and BRDF reflectance was examined, finding a strict linear correlation between SIF and reflectance at 688 nm, with an R2> 0.80 for all seven BRDF observations on winter wheat. Then, a BFDF correction model for the canopy SIF at 688 nm was presented by dividing by the canopy reflectance, and about 65.3% of the directional variation was successfully removed. Finally, the BFDF-corrected SIF signals were linked to photosynthetic activities, including gross ecosystem productivity (GEP) and photosynthetic light-use efficiency (LUE), and the determination coefficients between photosynthetic activities and the BFDF-corrected SIF increased for most cases. For GEP, the determination coefficients were slightly improved from 0.563, 0.382, and 0.613 (for raw SIF signals) to 0.592, 0.473, and 0.640 for all three diurnal experiments. For LUE, the determination coefficients increased from 0.393, and 0.358 to 0.517, and 0.528 for two experiments, while deceased slightly from 0.695 to 0.607 for one experiment. Therefore, according to the above preliminary results, the canopy SIF cannot be regarded as isotropic, and the directional emission SIF may be an important uncertainty in estimates of GEP and LUE.

  20. Light sensitive memristor with bi-directional and wavelength-dependent conductance control

    Science.gov (United States)

    Maier, P.; Hartmann, F.; Rebello Sousa Dias, M.; Emmerling, M.; Schneider, C.; Castelano, L. K.; Kamp, M.; Marques, G. E.; Lopez-Richard, V.; Worschech, L.; Höfling, S.

    2016-07-01

    We report the optical control of localized charge on positioned quantum dots in an electro-photo-sensitive memristor. Interband absorption processes in the quantum dot barrier matrix lead to photo-generated electron-hole-pairs that, depending on the applied bias voltage, charge or discharge the quantum dots and hence decrease or increase the conductance. Wavelength-dependent conductance control is observed by illumination with red and infrared light, which leads to charging via interband and discharging via intraband absorption. The presented memristor enables optical conductance control and may thus be considered for sensory applications in artificial neural networks as light-sensitive synapses or optically tunable memories.

  1. Telecommunications Relay Support of the Mars Phoenix Lander Mission

    Science.gov (United States)

    Edwards, Charles D., Jr.; Erickson, James K.; Gladden, Roy E.; Guinn, Joseph R.; Ilott, Peter A.; Jai, Benhan; Johnston, Martin D.; Kornfeld, Richard P.; Martin-Mur, Tomas J.; McSmith, Gaylon W.; Thomas, Reid C.; Varghese, Phil; Signori, Gina; Schmitz, Peter

    2010-01-01

    The Phoenix Lander, first of NASA's Mars Scout missions, arrived at the Red Planet on May 25, 2008. From the moment the lander separated from its interplanetary cruise stage shortly before entry, the spacecraft could no longer communicate directly with Earth, and was instead entirely dependent on UHF relay communications via an international network of orbiting Mars spacecraft, including NASA's 2001 Mars Odyssey (ODY) and Mars Reconnaissance Orbiter (MRO) spacecraft, as well as ESA's Mars Express (MEX) spacecraft. All three orbiters captured critical event telemetry and/or tracking data during Phoenix Entry, Descent and Landing. During the Phoenix surface mission, ODY and MRO provided command and telemetry services, far surpassing the original data return requirements. The availability of MEX as a backup relay asset enhanced the robustness of the surface relay plan. In addition to telecommunications services, Doppler tracking observables acquired on the UHF link yielded an accurate position for the Phoenix landing site.

  2. Accurate performance analysis of opportunistic decode-and-forward relaying

    KAUST Repository

    Tourki, Kamel

    2011-07-01

    In this paper, we investigate an opportunistic relaying scheme where the selected relay assists the source-destination (direct) communication. In our study, we consider a regenerative opportunistic relaying scheme in which the direct path may be considered unusable, and the destination may use a selection combining technique. We first derive the exact statistics of each hop, in terms of probability density function (PDF). Then, the PDFs are used to determine accurate closed form expressions for end-to-end outage probability for a transmission rate R. Furthermore, we evaluate the asymptotical performance analysis and the diversity order is deduced. Finally, we validate our analysis by showing that performance simulation results coincide with our analytical results over different network architectures. © 2011 IEEE.

  3. A programmable analog subthreshold biomimetic model for bi-directional communication with the brain.

    Science.gov (United States)

    Ghaderi, Viviane S; Song, Dong; Bouteiller, Jean-Marie C; Choma, John; Berger, Theodore W

    2013-01-01

    In this paper, we present a hardware implementation of a second order Laguerre Expansion of Volterra Kernel (LEV) model with four basis functions. The model is versatile enough to be applied at different abstraction levels (synapse, neuron, or network of neurons) and is implemented with analog building blocks in a modular manner. These analog blocks, realized using low power subthreshold CMOS transistors, can serve as a basis for large-scale hardware systems that emulate multi-input multi-output (MIMO) spike transformations in populations of neurons. The normalized mean square error between the signals produced by the circuit LEV implementation and the ideal LEV model is 8.15%. The total power consumption of the analog circuitry is less than 33nW. PMID:24109805

  4. 帧中继业务互扰问题的分析与解决措施%Analysis of and Solution to Mutual Interference among Traffic over Frame Relay Networks

    Institute of Scientific and Technical Information of China (English)

    林习良; 周锦标; 赵乾宏

    2015-01-01

    帧中继网络采用比特透明数据业务部件传输同步数据,采用虚拟路由器部件传输IP数据,针对网络运行过程中出现的不同传输链路的IP数据相互影响和IP数据影响同步数据现象,测试发现与带宽利用率有关。分析了优先级相同时用户数据报协议( UDP)数据比传输控制协议( TCP)数据更易受数据流量影响和入口数据流量过大的原因,以及帧中继不同类型业务发送优先级的对应关系,通过接入限速控制数据流量,并根据不同用户数据特点与传输要求设置相应优先级,问题得到有效解决。实际应用表明,基于限速策略和区分发送优先级的解决措施能够有效防止不同业务相互间的影响,确保重要数据稳定可靠地传输,可为解决其他类似问题提供参考。%Synchronous data is transmitted over frame relay networks by bit transparent data service compo-nent while IP data is transmitted by virtual router component. It's found that IP data of different transmis-sion links influences each other or IP data influences synchronous data in network running. Test shows that the problem is related to the utilization of network bandwidth. The reason why user data gram protocol (UDP) data is more likely to be affected by traffic flow rate than traffic control protocol(TCP) data in same priority and why traffic flow incoming from the remote node is too heavy is analyzed. The correspond-ing relationship of transfer priority of different traffic types over frame relay networks is also analyzed. As rate limitation is employed to control the traffic flow rate and transfer priority is set properly according to the characteristics and transmission requirements for different traffic types,problems are solved. Applica-tion results demonstrate that solutions based on rate limitation and transfer priority can effectively prevent mutual interference among different traffics and ensure reliable transmission of

  5. Speech-to-Speech Relay Service

    Science.gov (United States)

    ... an STS call from any telephone. You simply call the relay center by dialing 711, and indicate you wish to ... may also receive STS calls. The calling party calls the relay center by dialing 711 and asks the CA to ...

  6. DESIGN FOR SIMULATION KIT FOR TESTING RELAY.

    Directory of Open Access Journals (Sweden)

    ISHWARI TIWARI

    2013-10-01

    Full Text Available The companies, manufacturing relays are bound to test their products for specifications and compatibility. The production line in a company manufactures exceeds thousands of relays each day. This fact necessitates rapid and accurate testing of relays. A single person can’t handle the work alone. Even if he manages to handle, thetime consumption is more and a mistake may occur. So, it is necessary to employ an automation system for the testing of relays. The use of automated system facilitates less time consumption with the least possibility of error as relays are most important part of the circuitand they can be used as automatic switches, we are developing simulator for relay. The project is capable of testing a relay (either SPDT or DPDT along with generation of the relay testing report and its specifications on the desktop.

  7. 49 CFR 236.589 - Relays.

    Science.gov (United States)

    2010-10-01

    ... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and Cab Signal Systems Inspection and Tests; Locomotive § 236.589 Relays. (a) Each relay shall be...

  8. A study of optimization problem for amplify-and-forward relaying over weibull fading channels

    KAUST Repository

    Ikki, Salama Said

    2010-09-01

    This paper addresses the power allocation and relay positioning problems in amplify-and-forward cooperative networks operating in Weibull fading environments. We study adaptive power allocation (PA) with fixed relay location, optimal relay location with fixed power allocation, and joint optimization of the PA and relay location under total transmit power constraint, in order to minimize the outage probability and average error probability at high signal-to-noise ratios (SNR). Analytical results are validated by numerical simulations and comparisons between the different optimization schemes and their performance are provided. Results show that optimum PA brings only coding gain, while optimum relay location yields, in addition to the latter, diversity gains as well. Also, joint optimization improves both, the diversity gain and coding gain. Furthermore, results illustrate that the analyzed adaptive algorithms outperform uniform schemes. ©2010 IEEE.

  9. Performance Enhancement of LTE, a Multi-Hop Relay Node, by Employing Half-Duplex Mode

    Directory of Open Access Journals (Sweden)

    Jaafar Adhab Al-Dhaiban

    2012-05-01

    Full Text Available Relay stations are usually used to improve the signal strength for users near a cell edge, thus extending cell coverage. This paper proposes a study on the performance of a multi-hop relay network. This work introduces half-duplex relay with two scenarios. The first scenario is that wherein the relay node (RN acts to amplify and forward (AF and decode and forward (DF, where the relay and user equipment (UE are fixed. The second scenario is that wherein the proposed UE moves with angular velocity around RN, whereas RN moves with horizontal velocity toward the base station (BS and UE. The performance measures of each scenario are represented, where the impact velocity on the latency time and system capacity is explained. Both simulation and analytical calculations are provided.

  10. Performance analysis of two-way amplify and forward relaying with adaptive modulation

    KAUST Repository

    Hwang, Kyusung

    2009-09-01

    In this paper, we study two-way amplify-and-forward relaying in conjunction with adaptive modulation over a multiple relay network. In order to keep the diversity order equal to the number of relays and maintain a low complexity, we consider the best relay selection scheme in this work. Based on the proposed selection criterion for the best relay, we analyze the average spectral efficiency by its approximated upper bound. In addition, we extend the proposed scheme to the case where a direct path between source and destination exists. Our numerical examples show that the proposed system offers a considerable gain in the spectral efficiency while satisfying the error rates requirements. ©2009 IEEE.

  11. Self-vibration cancellation of a novel bi-directional magnetized NdFeB/magnetostrictive/piezoelectric laminate.

    Science.gov (United States)

    Leung, Chung Ming; Wang, Feifei; Wang, Ya

    2016-06-01

    A novel magnetoelectric (ME) laminated composite structure is proposed in this work, aiming to provide a good self-vibration cancellation performance under the magnetic field detection environment. The proposed structure consists of two Terfenol-D magnetostrictive alloy plates which are revised and length-magnetized by two NdFeB magnets bonded on the top surface of a thickness-polarized Pb(Zr, Ti)O3 (PZT) ceramic plate with separate electrodes. Experiments have shown that great vibration suppression up to 44 dB under harmonic disturbance was observed. The ME coefficient of the proposed structure also reaches up to ∼29 mV/Oe at non-resonance frequency and 758 mV/Oe at resonance frequency of 79 kHz which is ∼2 times larger than the traditional L-T Terfenol-D/PZT bilayer configuration of the same scale. Such performance improvement is achieved based on the bi-directional magnetic field bias (HBias) of two NdFeB magnets in magnetostrictive layer, internal in-series electrical wire connection in piezoelectric layer. The proposed design has great potential to be used for industrial applications associated with heavy environmental vibration noise. PMID:27370467

  12. Self-vibration cancellation of a novel bi-directional magnetized NdFeB/magnetostrictive/piezoelectric laminate

    Science.gov (United States)

    Leung, Chung Ming; Wang, Feifei; Wang, Ya

    2016-06-01

    A novel magnetoelectric (ME) laminated composite structure is proposed in this work, aiming to provide a good self-vibration cancellation performance under the magnetic field detection environment. The proposed structure consists of two Terfenol-D magnetostrictive alloy plates which are revised and length-magnetized by two NdFeB magnets bonded on the top surface of a thickness-polarized Pb(Zr, Ti)O3 (PZT) ceramic plate with separate electrodes. Experiments have shown that great vibration suppression up to 44 dB under harmonic disturbance was observed. The ME coefficient of the proposed structure also reaches up to ˜29 mV/Oe at non-resonance frequency and 758 mV/Oe at resonance frequency of 79 kHz which is ˜2 times larger than the traditional L-T Terfenol-D/PZT bilayer configuration of the same scale. Such performance improvement is achieved based on the bi-directional magnetic field bias (HBias) of two NdFeB magnets in magnetostrictive layer, internal in-series electrical wire connection in piezoelectric layer. The proposed design has great potential to be used for industrial applications associated with heavy environmental vibration noise.

  13. Are there Bi-directional Associations between Depressive Symptoms and C-Reactive Protein in Mid-life Women?

    Science.gov (United States)

    Matthews, Karen A.; Schott, Laura L.; Bromberger, Joyce T.; Cyranowski, Jill M.; Everson-Rose, Susan A.; Sowers, MaryFran

    2009-01-01

    OBJECTIVE: To test whether depressive symptoms are related to subsequent C-reactive protein (CRP) levels and/or whether CRP levels are related to subsequent depressive symptoms in mid-life women. METHODS: Women enrolled in the Study of Women's Health Across the Nation (SWAN) were followed for seven years and had measures of CES-Depression scores and CRP seven times during the follow-up period. Women were pre- or early peri-menopausal at study entry and were of Caucasian, African American, Hispanic, Japanese, or Chinese race/ethnicity. Analyses were restricted to initially healthy women. RESULTS: Longitudinal mixed linear regression models adjusting for age, race, site, time between exams, and outcome variable at year X showed that higher CES-D scores predicted higher subsequent CRP levels and vice versa over a 7-year period. Full multivariate models adjusting for body mass index, physical activity, medications, health conditions, and other covariates showed that higher CRP levels at year X predicted higher CES-D scores at year X+1, p = 0.03. Higher depressive symptoms predicted higher subsequent CRP levels at marginally significant levels, p=0.10. CONCLUSIONS: Higher CRP levels led to higher subsequent depressive symptoms, albeit the effect was small. The study demonstrates the importance of considering bi-directional relationships for depression and other psychosocial factors and risk for heart disease. PMID:19683568

  14. Motile properties of the bi-directional kinesin-5 Cin8 are affected by phosphorylation in its motor domain

    Science.gov (United States)

    Shapira, Ofer; Gheber, Larisa

    2016-01-01

    The Saccharomyces cerevisiae kinesin-5 Cin8 performs essential mitotic functions in spindle assembly and anaphase B spindle elongation. Recent work has shown that Cin8 is a bi-directional motor which moves towards the minus-end of microtubules (MTs) under high ionic strength (IS) conditions and changes directionality in low IS conditions and when bound between anti-parallel microtubules. Previous work from our laboratory has also indicated that Cin8 is differentially phosphorylated during late anaphase at cyclin-dependent kinase 1 (Cdk1)-specific sites located in its motor domain. In vivo, such phosphorylation causes Cin8 detachment from spindles and reduces the spindle elongation rate, while maintaining proper spindle morphology. To study the effect of phosphorylation on Cin8 motor function, we examined in vitro motile properties of wild type Cin8, as well as its phosphorylation using phospho-deficient and phospho-mimic variants, in a single molecule fluorescence motility assay. Analysis was performed on whole cell extracts and on purified Cin8 samples. We found that addition of negative charges in the phospho-mimic mutant weakened the MT-motor interaction, increased motor velocity and promoted minus-end-directed motility. These results indicate that phosphorylation in the catalytic domain of Cin8 regulates its motor function. PMID:27216310

  15. 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.

  16. Sensitivity improvement of time overcurrent relays

    Energy Technology Data Exchange (ETDEWEB)

    Enriquez, Arturo Conde; Martinez, Ernesto Vazquez [Universidad Autonoma de Nuevo Leon, Facultad de Ingenieria Mecanica y Electrica, Apdo. Postal 114-F, Ciudad Universitaria, CP 66450, San Nicolas de los Garza, Nuevo Leon (Mexico)

    2007-02-15

    In this paper, we recommend a new adaptive function for time overcurrent relays. The purpose of the adaptation process is to improve the sensitivity of time overcurrent relays, which then operate with a dynamic pickup setting such as a load current. The results obtained from time overcurrent adaptive relays are collated, and the results from analysis of negative sequence relays and conventional time overcurrent relays are also presented. In this article, we describe the control logic structure of an adaptive pickup current and its performance under different operating states. (author)

  17. Power Allocation Strategies for Fixed-Gain Half-Duplex Amplify-and-Forward Relaying in Nakagami-m Fading

    KAUST Repository

    Zafar, Ammar

    2013-09-01

    In this paper, we study power allocation strategies for a fixed-gain amplify-and-forward relay network employing multiple relays. We consider two optimization problems for the relay network: 1) maximizing the end-to-end signalto- noise ratio (SNR) and 2) minimizing the total power consumption while maintaining the end-to-end SNR over a threshold value. We investigate these two problems for two relaying protocols of all-participate (AP) relaying and selective relaying and two cases of feedback to the relays, full and limited. We show that the SNR maximization problem is concave and the power minimization problem is convex for all protocols and feedback cases considered. We obtain closed-form expressions for the two problems in the case of full feedback and solve the problems through convex programming for limited feedback. Numerical results show the benefit of having full feedback at the relays for both optimization problems. However, they also show that feedback overhead can be reduced by having only limited feedback to the relays with only a small degradation in performance.

  18. Performance Analysis of Amplify-and-Forward Two-Way Relaying with Co-Channel Interference and Channel Estimation Error

    KAUST Repository

    Liang Yang,

    2013-06-01

    In this paper, we consider the performance of a two-way amplify-and-forward relaying network (AF TWRN) in the presence of unequal power co-channel interferers (CCI). Specifically, we first consider AF TWRN with an interference-limited relay and two noisy-nodes with channel estimation errors and CCI. We derive the approximate signal-to-interference plus noise ratio expressions and then use them to evaluate the outage probability, error probability, and achievable rate. Subsequently, to investigate the joint effects of the channel estimation error and CCI on the system performance, we extend our analysis to a multiple-relay network and derive several asymptotic performance expressions. For comparison purposes, we also provide the analysis for the relay selection scheme under the total power constraint at the relays. For AF TWRN with channel estimation error and CCI, numerical results show that the performance of the relay selection scheme is not always better than that of the all-relay participating case. In particular, the relay selection scheme can improve the system performance in the case of high power levels at the sources and small powers at the relays.

  19. 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.

  20. Single relay selection in multi-access relay channel%多接入中继信道中的单中继选择

    Institute of Scientific and Technical Information of China (English)

    宋沈煜; 陈文

    2012-01-01

    It has been shown that cooperative relay selection schemes promise gains in robustness and energy-efficiency in wireless relaying networks. This paper considers multi-access relay channel (MARC) with 2 sources, N relays and 1 destination, where the half-duplexing relays perform non-regenerative network coding for the received signals from the two sources. Taking the direct links into consideration, it develops new single relay selection schemes based on best worst channel selection scheme, best signal-to-noise ratio selection scheme and best harmonic mean selection. The simulation results show that they outperform the existing schemes.%研究表明,协作中继选择能提高无线中继网络的鲁棒性和能效.文中研究一个多接入中继信道,包含2个信源,N个中继和1个信宿.中继节点为半双工,对两个信源的信号采用非再生的网络编码.考虑直接链路,基于最佳最差信道、最佳信噪比和最佳调和平均选择,提出新的选择策略.仿真结果表明其在性能上优于原有策略.