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Sample records for asynchronous cdma systems

  1. Computationally Efficient Blind Code Synchronization for Asynchronous DS-CDMA Systems with Adaptive Antenna Arrays

    Directory of Open Access Journals (Sweden)

    Chia-Chang Hu

    2005-04-01

    Full Text Available A novel space-time adaptive near-far robust code-synchronization array detector for asynchronous DS-CDMA systems is developed in this paper. There are the same basic requirements that are needed by the conventional matched filter of an asynchronous DS-CDMA system. For the real-time applicability, a computationally efficient architecture of the proposed detector is developed that is based on the concept of the multistage Wiener filter (MWF of Goldstein and Reed. This multistage technique results in a self-synchronizing detection criterion that requires no inversion or eigendecomposition of a covariance matrix. As a consequence, this detector achieves a complexity that is only a linear function of the size of antenna array (J, the rank of the MWF (M, the system processing gain (N, and the number of samples in a chip interval (S, that is, 𝒪(JMNS. The complexity of the equivalent detector based on the minimum mean-squared error (MMSE or the subspace-based eigenstructure analysis is a function of 𝒪((JNS3. Moreover, this multistage scheme provides a rapid adaptive convergence under limited observation-data support. Simulations are conducted to evaluate the performance and convergence behavior of the proposed detector with the size of the J-element antenna array, the amount of the L-sample support, and the rank of the M-stage MWF. The performance advantage of the proposed detector over other DS-CDMA detectors is investigated as well.

  2. Equalization With Oversampling in Multiuser CDMA Systems

    National Research Council Canada - National Science Library

    Vrelj, Bojan

    2004-01-01

    ...) for asynchronous or quasi-synchronous CDMA systems. AMOUR converts a multiuser CDMA system into parallel single-user systems regardless of the multipath and guarantees ISI mitigation irrespective of the channel null locations...

  3. Asynchronous Free-Space Optical CDMA Communications System for Last-mile Access Network

    DEFF Research Database (Denmark)

    Jurado-Navas, Antonio; Raddo, Thiago R.; Sanches, Anderson L.

    2016-01-01

    We propose a new hybrid asynchronous OCDMA-FSO communications system for access network solutions. New ABER expressions are derived under gamma-gamma scintillation channels, where all users can surprisingly achieve error-free transmissions when FEC is employed....

  4. CDMA systems capacity engineering

    CERN Document Server

    Kim, Kiseon

    2004-01-01

    This new hands-on resource tackles capacity planning and engineering issues that are crucial to optimizing wireless communication systems performance. Going beyond the system physical level and investigating CDMA system capacity at the service level, this volume is the single-source for engineering and analyzing systems capacity and resources.

  5. Generalized Asynchronous Systems

    Directory of Open Access Journals (Sweden)

    E. S. Kudryashova

    2012-01-01

    Full Text Available The paper consider a mathematical model of a concurrent system, the special case of which is an asynchronous system. Distributed asynchronous automata are introduced here. It is proved that Petri nets and transition systems with independence can be considered as distributed asynchronous automata. Time distributed asynchronous automata are defined in a standard way by correspondence which relates events with time intervals. It is proved that the time distributed asynchronous automata generalize time Petri nets and asynchronous systems.

  6. Computationally Efficient Chaotic Spreading Sequence Selection for Asynchronous DS-CDMA

    Directory of Open Access Journals (Sweden)

    Litviņenko Anna

    2017-12-01

    Full Text Available The choice of the spreading sequence for asynchronous direct-sequence code-division multiple-access (DS-CDMA systems plays a crucial role for the mitigation of multiple-access interference. Considering the rich dynamics of chaotic sequences, their use for spreading allows overcoming the limitations of the classical spreading sequences. However, to ensure low cross-correlation between the sequences, careful selection must be performed. This paper presents a novel exhaustive search algorithm, which allows finding sets of chaotic spreading sequences of required length with a particularly low mutual cross-correlation. The efficiency of the search is verified by simulations, which show a significant advantage compared to non-selected chaotic sequences. Moreover, the impact of sequence length on the efficiency of the selection is studied.

  7. Statistical modelling and reduction of multiple access interference power in wideband DS-CDMA and MC-CDMA communications systems

    OpenAIRE

    Carey, Daniel

    2006-01-01

    La plupart des instances de normalisation ont basé leur système cellulaire 3G sur le DS-CDMA (W-CDMA, UMTS, cdma2000). Les systèmes 4G désirant des services améliorés, cette thèse examine le Multicarrier CDMA (MC-CDMA) comme un candidat possible pour l'interface air des générations futures. Un modèle statistique de la puissance d'interférence totale sur canal asynchrone a été développé et suit une distribution de Nakagami pour les techniques asynchrones DS-CDMA et MC-CDMA. Deux nouvelles tech...

  8. Sequence Selection and Performance in DS/CDMA Systems

    Directory of Open Access Journals (Sweden)

    Jefferson Santos Ambrosio

    2016-03-01

    Full Text Available In this work key concepts on coding division multiple access (CDMA communication systems have been discussed. The sequence selection impact on the performance and capacity of direct sequence CDMA (DS/CDMA systems under AWGN and increasing system loading, as well as under multiple antennas channels was investigated.

  9. A mean field theory of coded CDMA systems

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Toru [Graduate School of Science and Technology, Keio University, Hiyoshi, Kohoku-ku, Yokohama-shi, Kanagawa 223-8522 (Japan); Tanaka, Toshiyuki [Graduate School of Informatics, Kyoto University, Yoshida Hon-machi, Sakyo-ku, Kyoto-shi, Kyoto 606-8501 (Japan); Saad, David [Neural Computing Research Group, Aston University, Birmingham B4 7ET (United Kingdom)], E-mail: yano@thx.appi.keio.ac.jp

    2008-08-15

    We present a mean field theory of code-division multiple-access (CDMA) systems with error-control coding. On the basis of the relation between the free energy and mutual information, we obtain an analytical expression of the maximum spectral efficiency of the coded CDMA system, from which a mean-field description of the coded CDMA system is provided in terms of a bank of scalar Gaussian channels whose variances in general vary at different code symbol positions. Regular low-density parity-check (LDPC)-coded CDMA systems are also discussed as an example of the coded CDMA systems.

  10. Equivalence of Linear MMSE Detection in DS-CDMA and MC-CDMA Systems over Time and Frequency Selective Channels

    Directory of Open Access Journals (Sweden)

    Tamer A. Kadous

    2003-01-01

    Full Text Available The goal of this paper is to compare the performance of the linear minimum mean square error (MMSE detector for a class of code division multiple access (CDMA systems in time and frequency selective channels. Specifically, we consider direct sequence (DS-CDMA, multicarrier (MC-CDMA, and the MC-DS-CDMA systems. Two key tools are used in our development. First, a general time-frequency framework that includes the different CDMA systems as special cases. Second, the duality between time and frequency domains that is used to derive equivalences between the different CDMA systems operating over purely frequency selective and purely time selective channels. We then combine the insights obtained from these special cases to assess the performance of CDMA systems over time and frequency selective channels. We provide sufficient conditions for the codes employed by the CDMA systems for the equivalences to hold. Numerical results are presented to illustrate the results.

  11. Use of CDMA access technology in mobile satellite systems

    Science.gov (United States)

    Ramasastry, Jay; Wiedeman, Bob

    1995-01-01

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

  12. Analysis of PPM-CDMA and OPPM-CDMA communication systems with new optical code

    Science.gov (United States)

    Liu, F.; Ghafouri-Shiraz, H.

    2005-11-01

    A novel type of optical spreading sequences, named the 'new-Modified Prime Code (nMPC)', is proposed for use in synchronous direct-detection optical code-division multiple-access (CDMA) systems which employ both pulse position modulation (PPM) and overlapping pulse position modulation (OPPM) schemes. The upper bounds on the bit error rate (BER) for nMPC used in PPM-CDMA systems are derived and compared with the respective systems, using a modified prime code (MPC) and a padded modified prime code (PMPC). The nMPC is further applied to the OPPM-CDMA system and the system with a proposed interference cancellation scheme. Our results show that under the same conditions the PPM-CDMA system performances are more improved with the use of nMPC than with the two other traditional codes. Moreover, they show that the system performances are significantly enhanced by the proposed interference reduction methods, if the nMPC is used in the OPPM-CDMA systems.

  13. An Iterative Multiuser Detector for Turbo-Coded DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Takawira Fambirai

    2005-01-01

    Full Text Available We propose an iterative multiuser detector for turbo-coded synchronous and asynchronous direct-sequence CDMA (DS-CDMA systems. The receiver is derived from the maximum a posteriori (MAP estimation of the single user's transmitted data, conditioned on information about the estimate of the multiple-access interference (MAI and the received signal from the channel. This multiple-access interference is reconstructed by making hard decisions on the users' detected bits at the preceding iteration. The complexity of the proposed receiver increases linearly with the number of users. The proposed detection scheme is compared with a previously developed one. The multiuser detector proposed in this paper has a better performance when the transmitted powers of all active users are equal in the additive white Gaussian noise (AWGN channel. Also, the detector is found to be resilient against the near-far effect.

  14. Security Enhancement Using Mutual Authentication in Existing CDMA Systems

    OpenAIRE

    L. Krishna Bharathi; Gnanou Florence Sudha

    2010-01-01

    Even though CDMA2000 wireless networks are being widely deployed as a cellular digital standard around the world, it has some hidden vulnerabilities concerned with security issues. The existing CDMA systems use authentication mechanism by CAVE (Cellular Authentication and Voice Encryption) algorithm. This authentication method has several disadvantages. Only one way authentication is provided, that is, only a base station authenticates a subscriber. And, CAVE algorithm is prone to cryptograph...

  15. Asynchronous control for networked systems

    CERN Document Server

    Rubio, Francisco; Bencomo, Sebastián

    2015-01-01

    This book sheds light on networked control systems; it describes different techniques for asynchronous control, moving away from the periodic actions of classical control, replacing them with state-based decisions and reducing the frequency with which communication between subsystems is required. The text focuses specially on event-based control. Split into two parts, Asynchronous Control for Networked Systems begins by addressing the problems of single-loop networked control systems, laying out various solutions which include two alternative model-based control schemes (anticipatory and predictive) and the use of H2/H∞ robust control to deal with network delays and packet losses. Results on self-triggering and send-on-delta sampling are presented to reduce the need for feedback in the loop. In Part II, the authors present solutions for distributed estimation and control. They deal first with reliable networks and then extend their results to scenarios in which delays and packet losses may occur. The novel ...

  16. On Analyzing LDPC Codes over Multiantenna MC-CDMA System

    Directory of Open Access Journals (Sweden)

    S. Suresh Kumar

    2014-01-01

    Full Text Available Multiantenna multicarrier code-division multiple access (MC-CDMA technique has been attracting much attention for designing future broadband wireless systems. In addition, low-density parity-check (LDPC code, a promising near-optimal error correction code, is also being widely considered in next generation communication systems. In this paper, we propose a simple method to construct a regular quasicyclic low-density parity-check (QC-LDPC code to improve the transmission performance over the precoded MC-CDMA system with limited feedback. Simulation results show that the coding gain of the proposed QC-LDPC codes is larger than that of the Reed-Solomon codes, and the performance of the multiantenna MC-CDMA system can be greatly improved by these QC-LDPC codes when the data rate is high.

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

    Science.gov (United States)

    Smith, Partrick O.; Geraniotis, Evaggelos A.

    1988-01-01

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

  18. A Novel Subcarrier Allocation Algorithm for MC-CDMA Systems

    Science.gov (United States)

    Seyman, Muhammet Nuri; Saçakli, Bircan

    2016-09-01

    Multi carrier modulation techniques such as MC-CDMA are used in high-speed communication applications. Due to MC-CDMA being a multiuser in technology, the subcarrier quantity allocated per user decreases in case the quantity of active users increases. Consequently, data rates per user are reduced with the increase in the bit error rate (BER). Efficient allocation of subcarriers to users within the system can aid the overcoming of this problem. This study develops a new algorithm for subcarrier allocation and system performance improvement in terms of BER, and data rates in comparison to other algorithms were ensured.

  19. A modified multitarget adaptive array algorithm for wireless CDMA system.

    Science.gov (United States)

    Liu, Yun-hui; Yang, Yu-hang

    2004-11-01

    The paper presents a modified least squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate (MBER) criterion. The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate (BER) of code division multiple access (CDMA) mobile communication system. In order to achieve adaptive update of weight vectors, a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance, capacity and near-far effect resistance of a given CDMA communication system.

  20. Capacity and coverage of power controlled CDMA cellular systems ...

    African Journals Online (AJOL)

    Coverage and capacity are among the ambitious challenges to be met by the third generation (3G) systems for successful deployment of its services to both residential and commercial subscribers. This paper reports on the performance study of CDMA systems in relation to an optimum step-regulated SNR-based ...

  1. Optical CDMA system using bacteriorhodopsin for optical data storage

    Science.gov (United States)

    Bae; Yang; Jin; Lee; Park

    1999-11-01

    An optical CDMA (code division multiple access) system for the optical data storage using bacteriorhodopsin (BR) is reported as an application of the BR materials. The desired signal of multiple input can be recorded and reconstructed by use of orthogonal codes. An experimental setup is proposed and demonstrated.

  2. Fair channel-dependent scheduling in CDMA systems

    NARCIS (Netherlands)

    de Bruin, I.C.C.; Heijenk, Geert; El Zarki, Magda; Zan, Jasmine Lei

    2003-01-01

    In this study a scheduling algorithm for CDMA systems is presented which is a trade-off between two extreme ways of scheduling: C/I based and Round-Robin scheduling. The simulation results indeed display that the advantages of both these extremes have been combined in the new algorithm: a good

  3. Iterative Decoding for an Optical CDMA based Laser communication System

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Young; Kim, Eun Cheol [Kwangwoon Univ., Seoul (Korea, Republic of); Cha, Jae Sang [Seoul National Univ. of Technology, Seoul (Korea, Republic of)

    2008-11-15

    An optical CDMA(code division multiple access)based Laser communication system has attracted much attention since it requires minimal optical Laser signal processing and it is virtually delay free, while from the theoretical point of view, its performance depends on the auto and cross correlation properties of employed sequences. Various kinds of channel coding schemes for optical CDMA based Laser communication systems have been proposed and analyzed to compensate nonideal channel and receiver conditions in impaired photon channels. In this paper, we propose and analyze an iterative decoding of optical CDMA based Laser communication signals for both shot noise limited and thermal noise limited systems. It is assumed that optical channel is an intensity modulated (IM)channel and direct detection scheme is employed to detect the received optical signal. The performance is evaluated in terms of bit error probability and throughput. It is demonstrated that the BER and throughput performance is substantially improved with interleaver length for a fixed code rate and with alphabet size of PPM (pulse position modulation). Also, the BER and throughput performance is significantly enhanced with the number of iterations for decoding process. The results in this paper can be applied to the optical CDMA based Laser communication network with multiple access applications.

  4. Improved Predictive Power Control Algorithms to Increase CDMA System Capacity

    Directory of Open Access Journals (Sweden)

    A. Kurniawan

    2009-11-01

    Full Text Available In this paper capacity of CDMA system is evaluated using an improved algorithm of channel prediction-based power control in Rayleigh fading channel environments. One of the most serious problems which degrades the performance of power control algorithm is the effect of feedback delay. To overcome the effect of feedback delay, power control algorithm relies on channel prediction techniques, which utilize the correlation property of the past channel measurements. In CDMA power control, however, the correlation property of channel measurements is destroyed because the transmit power is continuously updated for each power control interval. In order to restore the correlation property of the channel, the past channel measurements are compensated for by the same factors that were given by power updating for each power control interval. The prediction algorithm in this paper is proposed using the least mean square (LMS technique. The result shows that the capacity of CDMA systems increase significantly when the improved predictive algorithm is used. Numerical evaluation shows that CDMA capacity increases by more than 40 % for fixed step algorithm and more than 50 % for variable step algorithm when the proposed algorithm is employed.

  5. Improving performance of DS-CDMA systems using chaotic complex Bernoulli spreading codes

    Science.gov (United States)

    Farzan Sabahi, Mohammad; Dehghanfard, Ali

    2014-12-01

    The most important goal of spreading spectrum communication system is to protect communication signals against interference and exploitation of information by unintended listeners. In fact, low probability of detection and low probability of intercept are two important parameters to increase the performance of the system. In Direct Sequence Code Division Multiple Access (DS-CDMA) systems, these properties are achieved by multiplying the data information in spreading sequences. Chaotic sequences, with their particular properties, have numerous applications in constructing spreading codes. Using one-dimensional Bernoulli chaotic sequence as spreading code is proposed in literature previously. The main feature of this sequence is its negative auto-correlation at lag of 1, which with proper design, leads to increase in efficiency of the communication system based on these codes. On the other hand, employing the complex chaotic sequences as spreading sequence also has been discussed in several papers. In this paper, use of two-dimensional Bernoulli chaotic sequences is proposed as spreading codes. The performance of a multi-user synchronous and asynchronous DS-CDMA system will be evaluated by applying these sequences under Additive White Gaussian Noise (AWGN) and fading channel. Simulation results indicate improvement of the performance in comparison with conventional spreading codes like Gold codes as well as similar complex chaotic spreading sequences. Similar to one-dimensional Bernoulli chaotic sequences, the proposed sequences also have negative auto-correlation. Besides, construction of complex sequences with lower average cross-correlation is possible with the proposed method.

  6. Partial interference subspace rejection in CDMA systems

    DEFF Research Database (Denmark)

    Hansen, Henrik; Affes, Sofiene; Mewelstein, Paul

    2001-01-01

    Previously presented interference subspace rejection (ISR) proposed a family of new efficient multiuser detectors for CDMA. We reconsider in this paper the modes of ISR using decision feedback (DF). DF modes share similarities with parallel interference cancellation (PIC) but attempt to cancel...... interference by nulling rather than subtraction. However like the PIC they are prone to wrong tentative decisions. We propose a modification to DF modes that performs partial ISR instead of complete interference cancellation. When tentative decisions are correct, interference is therefore not perfectly...

  7. Joint Transmitter-Receiver Optimization in the Downlink CDMA Systems

    Directory of Open Access Journals (Sweden)

    Mohammad Saquib

    2002-08-01

    Full Text Available To maximize the downlink code-division multiple access (CDMA system capacity, we propose to minimize the total transmitted power of the system subject to users′ signal-to-interference ratio (SIR requirements via designing optimum transmitter sequences and utilizing linear optimum receivers (minimum mean square error (MMSE receiver. In our work on joint transmitter-receiver design for the downlink CDMA systems with multiple antennas and multipath channels, we develop several optimization algorithms by considering various system constraints and prove their convergence. We empirically observed that under the optimization algorithm with no constraint on the system, the optimum receiver structure matches the received transmitter sequences. A simulation study is performed to see how the different practical system constraints penalize the system with respect to the optimum algorithm with no constraint on the system.

  8. Power Control Imperfection in CDMA Systems with Adaptive Antennas

    Directory of Open Access Journals (Sweden)

    V. Wieser

    2002-12-01

    Full Text Available This paper deals with a simulation of cellular CDMA system usingbase station adaptive antennas. The model assumes two tiers area, fourtypes of antennas, lognormal shadowing corresponding to three types ofenvironments and perfect power control or two values of power controlerror, respectively. The capacity of system in up-link is evaluated bya number of mobile stations with higher signal to interference ratiothan threshold with given outage probability.

  9. Adaptive beamforming in a CDMA mobile satellite communications system

    Science.gov (United States)

    Munoz-Garcia, Samuel G.

    1993-01-01

    Code-Division Multiple-Access (CDMA) stands out as a strong contender for the choice of multiple access scheme in these future mobile communication systems. This is due to a variety of reasons such as the excellent performance in multipath environments, high scope for frequency reuse and graceful degradation near saturation. However, the capacity of CDMA is limited by the self-interference between the transmissions of the different users in the network. Moreover, the disparity between the received power levels gives rise to the near-far problem, this is, weak signals are severely degraded by the transmissions from other users. In this paper, the use of time-reference adaptive digital beamforming on board the satellite is proposed as a means to overcome the problems associated with CDMA. This technique enables a high number of independently steered beams to be generated from a single phased array antenna, which automatically track the desired user signal and null the unwanted interference sources. Since CDMA is interference limited, the interference protection provided by the antenna converts directly and linearly into an increase in capacity. Furthermore, the proposed concept allows the near-far effect to be mitigated without requiring a tight coordination of the users in terms of power control. A payload architecture will be presented that illustrates the practical implementation of this concept. This digital payload architecture shows that with the advent of high performance CMOS digital processing, the on-board implementation of complex DSP techniques -in particular digital beamforming- has become possible, being most attractive for Mobile Satellite Communications.

  10. Application of smart antennas in CDMA mobile communication system

    Science.gov (United States)

    Guo, Congliang; Zhou, Yingui; Liu, Tonghui; Wang, Rongsheng; Liu, Shijian

    2001-10-01

    Full coverage in mobile service region will elate mobile telephone customers. Limited frequency resources make mobile system capacity poor. High capacity and full coverage are two main key problems for system design. CDMA system has advantage of customer capacity, and Antenna array brings its coverage ability and intelligence into full play. Smart antenna combined with code division multiple access will improve mobile telecom system performance. Increasing system performance and capacity appear through enhancing desired signal and suppressing interference signals. Several kinds of antenna array techniques including beam forming, diversity, switched-beam antenna array and sectorization were discussed here in detail. The small antenna applications in TDMA mobile telecommunication systems are also discussed.

  11. Theoretical Investigation into Spectral Coexistence of CDMA and TDMA Systems

    Directory of Open Access Journals (Sweden)

    A.M. Abbosh

    2008-12-01

    Full Text Available The scarcity of available radio spectrum presently limits the extension of modern multimedia systems. This paper presents a theoretical investigation into the possibility of using a frequency overlay of a narrowband Code Division Multiple Access (CDMA System and a Time Division Multiple Access (TDMA System to provide a greater spectral efficiency. This paper shows that under certain conditions the two systems can operate in the same frequency band and in the same area with a considerable improvement in the overall capacity of the whole system.

  12. Comparison of CDMA and FDMA for the MobileStar(sm) system

    Science.gov (United States)

    Jacobs, I. M.; Gilhousen, K. S.; Weaver, L. A.; Renshaw, K.; Murphy, T.

    1988-01-01

    Spread-spectrum code division multiple access (CDMA) and single channel per carrier frequency division multiple access (FDMA) systems are compared for spectrum efficiency. CDMA is shown to have greater maximum throughput than FDMA for the MobileStar(sm) system which uses digital voice activated carriers and directive circularly polarized satellite antennas.

  13. Smart Antenna Application in DS-CDMA Mobile Communication System

    Science.gov (United States)

    Ng, Kok K.

    2002-09-01

    This thesis examine the use of an equally-spaced linear adaptive antenna array at the mobile station for a typical Direct Sequence Code Division Multiple Access (DS-CDMA) cellular mobile communications system with forward error correction, with soft decision decoding is studied, We analyze the performance of a randomly positioned mobile terminal with a randomly orientated adaptive antenna array in the forward channel (base- station to mobile) of a multi-cell DS-CDMA system and established four performance% boundaries, Using the more conservative optimized array antenna performance boundary for the 2-, 3- and 4-element linear array, we compare the capacity and the performance% of different cellular systems under a range of shadowing conditions, with and without antenna sectoring at the base-station, and for various user capacities, using Monte Carlo simulation We further apply tapped-delay line (transversal filter) to each antenna element channel, to allow frequency dependent amplitude and phase adjustment for broadband signals, The performance of a DS-CDMA cellular system with a mobile terminal equipped with a linear array and a tapped-delay line is analyzed, It has been demonstrated that the optimization process has been extremely computationally expensive and hence minimum taps should be used for practical consideration, The results illustrated that, in general, for a 2-element linear array system, a 3-tap delay line would be sufficient to equalize the broadband signal while providing a similar performance level to that of a narrow-band adaptive array system In the case of a 3-element linear array system, a 2-tap delay line would suffice.

  14. Adaptive Multiuser Detectors for DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Paul Jean Etienne Jeszensky

    2006-02-01

    Full Text Available This work makes a review of the main Adaptives Multi-user Detectors (MuD-Adpt for Direct Sequence - Code Division Multiple Access (DS-CDMA systems. The MuD-Adpt based on Minimum Mean Square Error (MMSE and Decorrelator (MuD-Dec are focused. Multi-user detectors show great resistance to the near-far effect and combat effectively the Multiple Access Interference (MAI. Comparative numeric results characterize the substantial performance improvement of those detectors in relation to the matched filter conventional receiver (Conv.

  15. An optical CDMA system based on chaotic sequences

    Science.gov (United States)

    Liu, Xiao-lei; En, De; Wang, Li-guo

    2014-03-01

    In this paper, a coherent asynchronous optical code division multiple access (OCDMA) system is proposed, whose encoder/decoder is an all-optical generator. This all-optical generator can generate analog and bipolar chaotic sequences satisfying the logistic maps. The formula of bit error rate (BER) is derived, and the relationship of BER and the number of simultaneous transmissions is analyzed. Due to the good property of correlation, this coherent OCDMA system based on these bipolar chaotic sequences can support a large number of simultaneous users, which shows that these chaotic sequences are suitable for asynchronous OCDMA system.

  16. System level comparison of FDMA vs. CDMA (under conference guideline constraint)

    Science.gov (United States)

    Renshaw, Ken

    1989-01-01

    The margin that is required to mitigate the near-far problem in a Code Division Multiple Access (CDMA) mobile satellite system is determined by the radio-propagation model selected, the distribution of the users in clear and shadowed environments, and implementation techniques. The use of revenue potential as a means of evaluating the relative merits of CDMA and Frequency Division Multiple Access (FDMA) systems is a convenient way to rationalize the performance of systems using high-gain and low-gain antennas. The revenue potential of CDMA is much greater than the revenue potential for FDMA for a particular satellite design considered.

  17. Blind information-theoretic multiuser detection algorithms for DS-CDMA and WCDMA downlink systems.

    Science.gov (United States)

    Waheed, Khuram; Salem, Fathi M

    2005-07-01

    Code division multiple access (CDMA) is based on the spread-spectrum technology and is a dominant air interface for 2.5G, 3G, and future wireless networks. For the CDMA downlink, the transmitted CDMA signals from the base station (BS) propagate through a noisy multipath fading communication channel before arriving at the receiver of the user equipment/mobile station (UE/MS). Classical CDMA single-user detection (SUD) algorithms implemented in the UE/MS receiver do not provide the required performance for modern high data-rate applications. In contrast, multi-user detection (MUD) approaches require a lot of a priori information not available to the UE/MS. In this paper, three promising adaptive Riemannian contra-variant (or natural) gradient based user detection approaches, capable of handling the highly dynamic wireless environments, are proposed. The first approach, blind multiuser detection (BMUD), is the process of simultaneously estimating multiple symbol sequences associated with all the users in the downlink of a CDMA communication system using only the received wireless data and without any knowledge of the user spreading codes. This approach is applicable to CDMA systems with relatively short spreading codes but becomes impractical for systems using long spreading codes. We also propose two other adaptive approaches, namely, RAKE -blind source recovery (RAKE-BSR) and RAKE-principal component analysis (RAKE-PCA) that fuse an adaptive stage into a standard RAKE receiver. This adaptation results in robust user detection algorithms with performance exceeding the linear minimum mean squared error (LMMSE) detectors for both Direct Sequence CDMA (DS-CDMA) and wide-band CDMA (WCDMA) systems under conditions of congestion, imprecise channel estimation and unmodeled multiple access interference (MAI).

  18. Cross-Layer Admission Control Policy for CDMA Beamforming Systems

    Directory of Open Access Journals (Sweden)

    Sheng Wei

    2007-01-01

    Full Text Available A novel admission control (AC policy is proposed for the uplink of a cellular CDMA beamforming system. An approximated power control feasibility condition (PCFC, required by a cross-layer AC policy, is derived. This approximation, however, increases outage probability in the physical layer. A truncated automatic retransmission request (ARQ scheme is then employed to mitigate the outage problem. In this paper, we investigate the joint design of an AC policy and an ARQ-based outage mitigation algorithm in a cross-layer context. This paper provides a framework for joint AC design among physical, data-link, and network layers. This enables multiple quality-of-service (QoS requirements to be more flexibly used to optimize system performance. Numerical examples show that by appropriately choosing ARQ parameters, the proposed AC policy can achieve a significant performance gain in terms of reduced outage probability and increased system throughput, while simultaneously guaranteeing all the QoS requirements.

  19. An efficient digital signal processing method for RRNS-based DS-CDMA systems

    Directory of Open Access Journals (Sweden)

    Peter Olsovsky

    2017-09-01

    Full Text Available This paper deals with an efficient method for achieving low power and high speed in advanced Direct-Sequence Code Division Multiple-Access (DS-CDMA wireless communication systems based on the Residue Number System (RNS. A modified algorithm for multiuser DS-CDMA signal generation in MATLAB is proposed and investigated. The most important characteristics of the generated PN code are also presented. Subsequently, a DS-CDMA system based on the combination of the RNS or the so-called Redundant Residue Number System (RRNS is proposed. The enhanced method using a spectrally efficient 8-PSK data modulation scheme to improve the bandwidth efficiency for RRNS-based DS-CDMA systems is presented. By using the C-measure (complexity measure of the error detection function, it is possible to estimate the size of the circuit. Error detection function in RRNSs can be efficiently implemented by LookUp Table (LUT cascades.

  20. A Charrelation Matrix-Based Blind Adaptive Detector for DS-CDMA Systems.

    Science.gov (United States)

    Luo, Zhongqiang; Zhu, Lidong

    2015-08-14

    In this paper, a blind adaptive detector is proposed for blind separation of user signals and blind estimation of spreading sequences in DS-CDMA systems. The blind separation scheme exploits a charrelation matrix for simple computation and effective extraction of information from observation signal samples. The system model of DS-CDMA signals is modeled as a blind separation framework. The unknown user information and spreading sequence of DS-CDMA systems can be estimated only from the sampled observation signals. Theoretical analysis and simulation results show that the improved performance of the proposed algorithm in comparison with the existing conventional algorithms used in DS-CDMA systems. Especially, the proposed scheme is suitable for when the number of observation samples is less and the signal to noise ratio (SNR) is low.

  1. PV-solar / Wind Hybrid Energy System for GSM/CDMA Type Mobile Telephony Base

    National Research Council Canada - National Science Library

    Station Md. Ibrahim; Mohammad Tayyab

    2015-01-01

    This paper presents the design of optimized PV-Solar and Wind Hybrid Energy System for GSM/CDMA type mobile base station over conventional diesel generator for a particular site in south India (Chennai...

  2. A Charrelation Matrix-Based Blind Adaptive Detector for DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Zhongqiang Luo

    2015-08-01

    Full Text Available In this paper, a blind adaptive detector is proposed for blind separation of user signals and blind estimation of spreading sequences in DS-CDMA systems. The blind separation scheme exploits a charrelation matrix for simple computation and effective extraction of information from observation signal samples. The system model of DS-CDMA signals is modeled as a blind separation framework. The unknown user information and spreading sequence of DS-CDMA systems can be estimated only from the sampled observation signals. Theoretical analysis and simulation results show that the improved performance of the proposed algorithm in comparison with the existing conventional algorithms used in DS-CDMA systems. Especially, the proposed scheme is suitable for when the number of observation samples is less and the signal to noise ratio (SNR is low.

  3. A European mobile satellite system concept exploiting CDMA and OBP

    Science.gov (United States)

    Vernucci, A.; Craig, A. D.

    1993-01-01

    This paper describes a novel Land Mobile Satellite System (LMSS) concept applicable to networks allowing access to a large number of gateway stations ('Hubs'), utilizing low-cost Very Small Aperture Terminals (VSAT's). Efficient operation of the Forward-Link (FL) repeater can be achieved by adopting a synchronous Code Division Multiple Access (CDMA) technique, whereby inter-code interference (self-noise) is virtually eliminated by synchronizing orthogonal codes. However, with a transparent FL repeater, the requirements imposed by the highly decentralized ground segment can lead to significant efficiency losses. The adoption of a FL On-Board Processing (OBP) repeater is proposed as a means of largely recovering this efficiency impairment. The paper describes the network architecture, the system design and performance, the OBP functions and impact on implementation. The proposed concept, applicable to a future generation of the European LMSS, was developed in the context of a European Space Agency (ESA) study contract.

  4. Diversity reception for advanced multi-satellite networks: A CDMA approach

    Science.gov (United States)

    Colzi, E.; Degaudenzi, R.; Elia, C.; Giannetti, F.; Viola, R.

    1993-01-01

    Diversity reception for Synchronous CDMA (S-CDMA) is introduced and analyzed. A Gaussian co-channel synchronous and asynchronous interference approximation is derived to evaluate the effects on the system bit error rate. Numerical results are provided for a simple mobile communication system where the signals transmitted by two distinct satellites in visibility are coherently combined by a three fingers Rake receiver. A second example showing performance of an integrated ground/satellite single frequency network for digital audio broadcasting is presented. Results show the capacity advantage of utilizing S-CDMA in combination with diversity reception.

  5. QS-CDMA: a potential air interface candidate for 4G wireless communications

    Science.gov (United States)

    Stanczak, Slawomir; Boche, Holger

    2002-11-01

    The paper addresses the problem of constructing signature sequences or quasi-synchronous CDMA systems. The major feature of QS-CDMA is hat the duration of any signature waveform is significantly longer than the maximal signal delay with respect to a common clock. In contrast to completely asynchronous CDMA systems for which all aperiodic correlations must be taken into consideration, in case of quasi-synchronous CDMA, it is sufficient to focus on a small window around the zero shift, the so-called interference window. This implifies sequence design and allows us to reduce both the inter-symbol interference and multiple access interference drastically, thereby enhancing the system performance tremendously. This is all the more important since construction of sequences for completely asynchronous CDMA systems is a notoriously difficult problem and no such sequence sets are known. Consequently, random sequences must be used that are known to induce a significant capacity loss. In this paper, we present two possible methods for obtaining sequences with small aperiodic correlation sidelobes in the vicinity of the zero shift. We discuss advantages and disadvantages of QS-CDMA and W-CDMA, the major air interface for third generation mobile communications systems. Some simulation results are presented.

  6. Physical Layer Built-In Security Analysis and Enhancement Algorithms for CDMA Systems

    Directory of Open Access Journals (Sweden)

    Li Tongtong

    2007-01-01

    Full Text Available Historically developed for secure communication and military use, CDMA has been identified as a major modulation and multiple-access technique for 3G systems and beyond. In addition to the wide bandwidth and low power-spectrum density which make CDMA signals robust to narrowband jamming and easy to be concealed within the noise floor, the physical layer built-in information privacy of CDMA system is provided by pseudorandom scrambling. In this paper, first, security weakness of the operational and proposed CDMA airlink interfaces is analyzed. Second, based on the advanced encryption standard (AES, we propose to enhance the physical layer built-in security of CDMA systems through secure scrambling. Performance analysis demonstrates that while providing significantly improved information privacy, CDMA systems with secure scrambling have comparable computational complexity and overall system performance with that of conventionally scrambled systems. Moreover, it is shown that by scrambling the training sequence and the message sequence separately with two independent scrambling sequences, both information privacy and system performance can be further improved. The proposed scheme can readily be applied to 3G systems and beyond.

  7. Timing-Free Blind Multiuser Detection for Multicarrier DS/CDMA Systems with Multiple Antennae

    Directory of Open Access Journals (Sweden)

    Stefano Buzzi

    2004-05-01

    Full Text Available The problem of blind multiuser detection for an asynchronous multicarrier DS-CDMA system employing multiple transmit and receive antennae over a Rayleigh fading channel is considered in this paper. The solutions that we develop require prior knowledge of the spreading code of the user to be decoded only, while no further information either on the user to be decoded or on the other active users is required. Several combining rules for the observables at the output of each receive antenna are proposed and assessed, and the implications of the different options are studied in depth in terms of both detection performance and computational complexity. A closed form expression is also derived for the conditional error probability and a lower bound for the near-far resistance is provided. Results confirm that the proposed blind receivers can cope with both multiple access interference suppression and channel estimation at the price of a limited performance loss as compared to the ideal linear receivers which assume perfect channel state information.

  8. Design and Implementation of a Pilot Signal Scanning Receiver for CDMA Personal Communication Services Systems

    OpenAIRE

    Blankenship, T. Keith III

    1998-01-01

    In cellular and personal communications services (PCS) systems based on code division multiple access (CDMA), a pilot signal is used on the forward link for synchronization, coherent detection, soft handoff, maintaining orthogonality between base stations, and, in the future, position location. It is critical that the percentage of power allocated to the pilot signal transmitted by each base station be fixed properly to ensure the ability of the CDMA ne...

  9. Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System

    Directory of Open Access Journals (Sweden)

    Raulefs Ronald

    2004-01-01

    Full Text Available We investigate rotated Walsh-Hadamard spreading matrices for a broadband MC-CDMA system with robust channel estimation in the synchronous downlink. The similarities between rotated spreading and signal space diversity are outlined. In a multiuser MC-CDMA system, possible performance improvements are based on the chosen detector, the channel code, and its Hamming distance. By applying rotated spreading in comparison to a standard Walsh-Hadamard spreading code, a higher throughput can be achieved. As combining the channel code and the spreading code forms a concatenated code, the overall minimum Hamming distance of the concatenated code increases. This asymptotically results in an improvement of the bit error rate for high signal-to-noise ratio. Higher convolutional channel code rates are mostly generated by puncturing good low-rate channel codes. The overall Hamming distance decreases significantly for the punctured channel codes. Higher channel code rates are favorable for MC-CDMA, as MC-CDMA utilizes diversity more efficiently compared to pure OFDMA. The application of rotated spreading in an MC-CDMA system allows exploiting diversity even further. We demonstrate that the rotated spreading gain is still present for a robust pilot-aided channel estimator. In a well-designed system, rotated spreading extends the performance by using a maximum likelihood detector with robust channel estimation at the receiver by about 1 dB.

  10. Adaptive Space-Time-Spreading-Assisted Wideband CDMA Systems Communicating over Dispersive Nakagami- Fading Channels

    Directory of Open Access Journals (Sweden)

    Yang Lie-Liang

    2005-01-01

    Full Text Available In this contribution, the performance of wideband code-division multiple-access (W-CDMA systems using space-time-spreading- (STS- based transmit diversity is investigated, when frequency-selective Nakagami- fading channels, multiuser interference, and background noise are considered. The analysis and numerical results suggest that the achievable diversity order is the product of the frequency-selective diversity order and the transmit diversity order. Furthermore, both the transmit diversity and the frequency-selective diversity have the same order of importance. Since W-CDMA signals are subjected to frequency-selective fading, the number of resolvable paths at the receiver may vary over a wide range depending on the transmission environment encountered. It can be shown that, for wireless channels where the frequency selectivity is sufficiently high, transmit diversity may be not necessitated. Under this case, multiple transmission antennas can be leveraged into an increased bitrate. Therefore, an adaptive STS-based transmission scheme is then proposed for improving the throughput of W-CDMA systems. Our numerical results demonstrate that this adaptive STS-based transmission scheme is capable of significantly improving the effective throughput of W-CDMA systems. Specifically, the studied W-CDMA system's bitrate can be increased by a factor of three at the modest cost of requiring an extra 0.4 dB or 1.2 dB transmitted power in the context of the investigated urban or suburban areas, respectively.

  11. Blind Identification and Equalization of MC-CDMA Systems Using Higher Order Cumulants

    Directory of Open Access Journals (Sweden)

    Mohammed Zidane

    2014-04-01

    Full Text Available In this work we propose an algorithm based on fourth order cumulants for identification of the linear system (Finite- Impulse Response (FIR with Non Minimum Phase (NMP excited by non-Gaussian sequences, independent identically distributed (i.i.d. In order to test its efficiency, we have compared with the Safi et al. algorithm, for that we considered three practical frequency-selective fading channel, called Broadband Radio Access Network (BRAN A, BRAN B, and BRAN D, normalized for  MC-CDMA systems. In the part of MC-CDMA, we use the zero forcing (ZF and the minimum mean square error (MMSE equalizers to perform our algorithms. The simulation results show that the bit error rate (BER performances of the downlink MC-CDMA systems, using proposed algorithm (AlgoZ is more accurate compared with the results obtained with the Safi et al. (Alg-CUM algorithm.

  12. Performance Analysis of a CDMA VSAT System With Convoltional and Reed-Solomon Coding

    Science.gov (United States)

    Yigit, Ugur

    2002-09-01

    The purpose of this thesis is to model a satellite communication system with VSATs, using Spread Spectrum CDMA methods and Forward Error Correction (FEC), Walsh codes and PN sequences are used to generate a CDMA system and FEC is used to further improve the performance. Convolutional and block coding methods are examined and the results are obtained for each different case, including concatenated use of the codes, The performance of the system is given in terms of Bit Error Rate (BER), As observed from the results, the performance is mainly affected by the number of users and the code rates,

  13. A CDMA architecture for a Ka-band Personal Access Satellite System

    Science.gov (United States)

    Motamedi, Masoud; Sue, Miles K.

    1990-01-01

    A Code Division Multiple Access (CDMA) architecture is currently being studied for use in a Ka-band Personal Access Satellite System (PASS). The complete architecture consisting of block diagrams of the user terminal, the supplier station, the network management center, and the satellite is described along with the access methods and frequency/time plans. The complexity of developing this system using the CDMA architecture is compared to that of a Frequency Division Multiple Access (FDMA) architecture. The inherent advantages and disadvantages of the two architectures are compared and their respective capacities are discussed.

  14. Optimization of hybrid token-CDMA MAC system using cross-layer information

    CSIR Research Space (South Africa)

    Liu, I-S

    2007-08-01

    Full Text Available This paper presents a joint medium access control and physical (MAC-PHY) layers solution for optimizing the system performance in the hybrid Token-CDMA MAC system. The proposed scheme is designed in order to provide continuous monitoring...

  15. Eventual Leader Service in Unreliable Asynchronous Systems: Why? How?

    OpenAIRE

    Raynal, Michel

    2007-01-01

    Providing processes with an {\\it eventual leader} service is an important issue when one has to design and implement a middleware layer on top of a failure-prone asynchronous distributed system. This invited lecture investigates this problem. It first shows that such a service cannot be built if the underlying system is fully asynchronous. Then, the paper visits several additional behavioral assumptions that have been proposed in the literature to cope with this impossibility and presents cor...

  16. On the High Altitude Platform (HAP W-CDMA System Capacity

    Directory of Open Access Journals (Sweden)

    L. de Haro-Ariet

    2004-06-01

    Full Text Available The performance of a downlink power control model, based on a n-thpower distance law, is evaluated for high altitude platform station(HAPS W-CDMA systems. The downlink capacity using this model iscompared with the uplink capacity. It is shown that the uplink capacityis higher than the downlink capacity.

  17. Approximate discrete time analysis of the hybrid Token-CDMA MAC system

    CSIR Research Space (South Africa)

    Liu, YS

    2007-09-01

    Full Text Available In this paper a hybrid Token-CDMA based medium access control (MAC) protocol is considered. The MAC scheme is analytically modelled as a multiserver multiqueue (MSMQ) system in the case of a gated service discipline. The authors present...

  18. Differential Space-Time Block Code Modulation for DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Liu Jianhua

    2002-01-01

    Full Text Available A differential space-time block code (DSTBC modulation scheme is used to improve the performance of DS-CDMA systems in fast time-dispersive fading channels. The resulting scheme is referred to as the differential space-time block code modulation for DS-CDMA (DSTBC-CDMA systems. The new modulation and demodulation schemes are especially studied for the down-link transmission of DS-CDMA systems. We present three demodulation schemes, referred to as the differential space-time block code Rake (D-Rake receiver, differential space-time block code deterministic (D-Det receiver, and differential space-time block code deterministic de-prefix (D-Det-DP receiver, respectively. The D-Det receiver exploits the known information of the spreading sequences and their delayed paths deterministically besides the Rake type combination; consequently, it can outperform the D-Rake receiver, which employs the Rake type combination only. The D-Det-DP receiver avoids the effect of intersymbol interference and hence can offer better performance than the D-Det receiver.

  19. The Design of Data Transmission Terminal in Remote Warning Control System Based on CDMA 1X Network

    Directory of Open Access Journals (Sweden)

    Dan CHEN

    2014-03-01

    Full Text Available This study proposes a framework of data transmission terminal in remote warning control system based on CDMA 1X network. According to the functional requirements of wireless broadband communication system, the hardware interfaces and software of the CDMA 1X data transmission terminal are designed detailedly and the system is implemented using wireless access and embedded development technologies. It has good applicability and portability so that various wireless data transmissions can be achieved by replacing the data source module.

  20. Single Carrier Cyclic Prefix-Assisted CDMA System with Frequency Domain Equalization for High Data Rate Transmission

    Directory of Open Access Journals (Sweden)

    Chin Francois

    2004-01-01

    Full Text Available Multiple-access interference and interfinger interference limit the capacity of conventional single-carrier DS-CDMA systems. Even though multicarrier CDMA posses the advantages of conventional CDMA and OFDM, it suffers from two major implementation difficulties such as peak-to-average power ratio and high sensitivity to frequency offset and RF phase noise. A novel approach based on single-carrier cyclic prefix-assisted CDMA has been proposed to overcome the disadvantages of single-carrier CDMA and multicarrier modulation. The usefulness of the proposed approach for high-speed packet access with simplified channel estimation procedures are investigated in this paper. The paper also proposes a data-dependent pilot structure for the downlink transmission of the proposed system for enhancing pilot-assisted channel estimation in frequency domain. The performance of the proposed pilot structure is compared against the data-independent common pilot structure. The proposed system is extensively simulated for different channel parameters with different channel estimation and equalization methods and the results are compared against conventional multicarrier CDMA systems with identical system specifications.

  1. Performance enhancement of MC-CDMA system through novel sensitive bit algorithm aided turbo multi user detection.

    Science.gov (United States)

    Kumaravel, Rasadurai; Narayanaswamy, Kumaratharan

    2015-01-01

    Multi carrier code division multiple access (MC-CDMA) system is a promising multi carrier modulation (MCM) technique for high data rate wireless communication over frequency selective fading channels. MC-CDMA system is a combination of code division multiple access (CDMA) and orthogonal frequency division multiplexing (OFDM). The OFDM parts reduce multipath fading and inter symbol interference (ISI) and the CDMA part increases spectrum utilization. Advantages of this technique are its robustness in case of multipath propagation and improve security with the minimize ISI. Nevertheless, due to the loss of orthogonality at the receiver in a mobile environment, the multiple access interference (MAI) appears. The MAI is one of the factors that degrade the bit error rate (BER) performance of MC-CDMA system. The multiuser detection (MUD) and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects. In this paper a low complexity iterative soft sensitive bits algorithm (SBA) aided logarithmic-Maximum a-Posteriori algorithm (Log MAP) based turbo MUD is proposed. Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI.

  2. Performance enhancement of MC-CDMA system through novel sensitive bit algorithm aided turbo multi user detection.

    Directory of Open Access Journals (Sweden)

    Rasadurai Kumaravel

    Full Text Available Multi carrier code division multiple access (MC-CDMA system is a promising multi carrier modulation (MCM technique for high data rate wireless communication over frequency selective fading channels. MC-CDMA system is a combination of code division multiple access (CDMA and orthogonal frequency division multiplexing (OFDM. The OFDM parts reduce multipath fading and inter symbol interference (ISI and the CDMA part increases spectrum utilization. Advantages of this technique are its robustness in case of multipath propagation and improve security with the minimize ISI. Nevertheless, due to the loss of orthogonality at the receiver in a mobile environment, the multiple access interference (MAI appears. The MAI is one of the factors that degrade the bit error rate (BER performance of MC-CDMA system. The multiuser detection (MUD and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects. In this paper a low complexity iterative soft sensitive bits algorithm (SBA aided logarithmic-Maximum a-Posteriori algorithm (Log MAP based turbo MUD is proposed. Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI.

  3. Turbo code channel reliability for DS/CDMA systems under slow and frequency selective fading and multiple access interference

    Directory of Open Access Journals (Sweden)

    Taufik Abrão

    2008-08-01

    Full Text Available This work analyzes the Turbo and Convolutional codes strategies applied to the single-user detection (SuD problem in multiple access systems DS/CDMA, in multipath slow Rayleigh channels. In this work, a new equation for the DS/CDMA channel reliability, obtained from Monte Carlo Simulations (MCS, is proposed. Comparison with the literature results and has indicated a superior performance in the high Eb/N0 regions; in other Eb/N0 regions the proposed equation has similar performance than those described in the literature. Additionally, this work makes an analysis of the complexity/memory requirements versus performance of DS/CDMA receivers considering turbo (CDMA2000 and Viterbi (IS-95 decoders.

  4. Successive Interference Cancellation for DS-CDMA Systems with Transmit Diversity

    Directory of Open Access Journals (Sweden)

    Li Wei

    2004-01-01

    Full Text Available We introduce a new successive interference cancellation (SIC technique for direct sequence code division multiple access (DS-CDMA systems with transmit diversity. The transmit diversity is achieved with a space-time block code (STBC. In our work we first consider hard decision SIC with an STBC, and then investigate the performance of soft decision SIC with an STBC. System performance over a Rayleigh fading channel is investigated and the analysis is confirmed by simulation.

  5. A review on synchronous CDMA systems: optimum overloaded codes, channel capacity, and power control

    Directory of Open Access Journals (Sweden)

    Hosseini Seyed Amirhossein

    2011-01-01

    Full Text Available Abstract This paper is a tutorial review on important issues related to code-division multiple-access (CDMA systems such as channel capacity, power control, and optimum codes; specifically, we consider optimum overloaded codes that achieve errorless transmission in the absence of noise for the binary and nonbinary cases. A survey of lower and upper bounds for the sum channel capacity of such systems is given in the presence and absence of channel noise. The asymptotic results for the channel capacity are also investigated. The channel capacity, errorless transmission codes, and power estimation for near-far effects are also explored. The emphasis of this tutorial review is on the overloaded CDMA systems.

  6. Time of Arrival Estimation in Probability-Controlled Generalized CDMA Systems

    Directory of Open Access Journals (Sweden)

    Hagit Messer

    2007-11-01

    Full Text Available In recent years, more and more wireless communications systems are required to provide also a positioning measurement. In code division multiple access (CDMA communication systems, the positioning accuracy is significantly degraded by the multiple access interference (MAI caused by other users in the system. This MAI is commonly managed by a power control mechanism, and yet, MAI has a major effect on positioning accuracy. Probability control is a recently introduced interference management mechanism. In this mechanism, a user with excess power chooses not to transmit some of its symbols. The information in the nontransmitted symbols is recovered by an error-correcting code (ECC, while all other users receive a more reliable data during these quiet periods. Previous research had shown that the implementation of a probability control mechanism can significantly reduce the MAI. In this paper, we show that probability control also improves the positioning accuracy. We focus on time-of-arrival (TOA based positioning systems. We analyze the TOA estimation performance in a generalized CDMA system, in which the probability control mechanism is employed, where the transmitted signal is noncontinuous with a symbol transmission probability smaller than 1. The accuracy of the TOA estimation is determined using appropriate modifications of the Cramer-Rao bound on the delay estimation. Keeping the average transmission power constant, we show that the TOA accuracy of each user does not depend on its transmission probability, while being a nondecreasing function of the transmission probability of any other user. Therefore, a generalized, noncontinuous CDMA system with a probability control mechanism can always achieve better positioning performance, for all users in the network, than a conventional, continuous, CDMA system.

  7. Spreading Code Assignment Strategies for MIMO-CDMA Systems Operating in Frequency-Selective Channels

    Directory of Open Access Journals (Sweden)

    Claude D'Amours

    2009-01-01

    Full Text Available Code Division Multiple Access (CDMA and multiple input multiple output- (MIMO- CDMA systems suffer from multiple access interference (MAI which limits the spectral efficiency of these systems. By making these systems more power efficient, we can increase the overall spectral efficiency. This can be achieved through the use of improved modulation and coding techniques. Conventional MIMO-CDMA systems use fixed spreading code assignments. By strategically selecting the spreading codes as a function of the data to be transmitted, we can achieve coding gain and introduce additional degrees of freedom in the decision variables at the output of the matched filters. In this paper, we examine the bit error rate performance of parity bit-selected spreading and permutation spreading under different wireless channel conditions. A suboptimal detection technique based on maximum likelihood detection is proposed for these systems operating in frequency selective channels. Simulation results demonstrate that these code assignment techniques provide an improvement in performance in terms of bit error rate (BER while providing increased spectral efficiency compared to the conventional system. Moreover, the proposed strategies are more robust to channel estimation errors as well as spatial correlation.

  8. Spreading Code Assignment Strategies for MIMO-CDMA Systems Operating in Frequency-Selective Channels

    Directory of Open Access Journals (Sweden)

    Dahmane AdelOmar

    2009-01-01

    Full Text Available Abstract Code Division Multiple Access (CDMA and multiple input multiple output- (MIMO- CDMA systems suffer from multiple access interference (MAI which limits the spectral efficiency of these systems. By making these systems more power efficient, we can increase the overall spectral efficiency. This can be achieved through the use of improved modulation and coding techniques. Conventional MIMO-CDMA systems use fixed spreading code assignments. By strategically selecting the spreading codes as a function of the data to be transmitted, we can achieve coding gain and introduce additional degrees of freedom in the decision variables at the output of the matched filters. In this paper, we examine the bit error rate performance of parity bit-selected spreading and permutation spreading under different wireless channel conditions. A suboptimal detection technique based on maximum likelihood detection is proposed for these systems operating in frequency selective channels. Simulation results demonstrate that these code assignment techniques provide an improvement in performance in terms of bit error rate (BER while providing increased spectral efficiency compared to the conventional system. Moreover, the proposed strategies are more robust to channel estimation errors as well as spatial correlation.

  9. Performance of Turbo Interference Cancellation Receivers in Space-Time Block Coded DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Emmanuel Oluremi Bejide

    2008-07-01

    Full Text Available We investigate the performance of turbo interference cancellation receivers in the space time block coded (STBC direct-sequence code division multiple access (DS-CDMA system. Depending on the concatenation scheme used, we divide these receivers into the partitioned approach (PA and the iterative approach (IA receivers. The performance of both the PA and IA receivers is evaluated in Rayleigh fading channels for the uplink scenario. Numerical results show that the MMSE front-end turbo space-time iterative approach receiver (IA effectively combats the mixture of MAI and intersymbol interference (ISI. To further investigate the possible achievable data rates in the turbo interference cancellation receivers, we introduce the puncturing of the turbo code through the use of rate compatible punctured turbo codes (RCPTCs. Simulation results suggest that combining interference cancellation, turbo decoding, STBC, and RCPTC can significantly improve the achievable data rates for a synchronous DS-CDMA system for the uplink in Rayleigh flat fading channels.

  10. Compensating for Channel Fading in DS-CDMA Communication Systems Employing ICA Neural Network Detectors

    Directory of Open Access Journals (Sweden)

    David Overbye

    2005-06-01

    Full Text Available In this paper we examine the impact of channel fading on the bit error rate of a DS-CDMA communication system. The system employs detectors that incorporate neural networks effecting methods of independent component analysis (ICA, subspace estimation of channel noise, and Hopfield type neural networks. The Rayleigh fading channel model is used. When employed in a Rayleigh fading environment, the ICA neural network detectors that give superior performance in a flat fading channel did not retain this superior performance. We then present a new method of compensating for channel fading based on the incorporation of priors in the ICA neural network learning algorithms. When the ICA neural network detectors were compensated using the incorporation of priors, they give significantly better performance than the traditional detectors and the uncompensated ICA detectors. Keywords: CDMA, Multi-user Detection, Rayleigh Fading, Multipath Detection, Independent Component Analysis, Prior Probability Hebbian Learning, Natural Gradient

  11. Blind ICA detection based on second-order cone programming for MC-CDMA systems

    Science.gov (United States)

    Jen, Chih-Wei; Jou, Shyh-Jye

    2014-12-01

    The multicarrier code division multiple access (MC-CDMA) technique has received considerable interest for its potential application to future wireless communication systems due to its high data rate. A common problem regarding the blind multiuser detectors used in MC-CDMA systems is that they are extremely sensitive to the complex channel environment. Besides, the perturbation of colored noise may negatively affect the performance of the system. In this paper, a new coherent detection method will be proposed, which utilizes the modified fast independent component analysis (FastICA) algorithm, based on approximate negentropy maximization that is subject to the second-order cone programming (SOCP) constraint. The aim of the proposed coherent detection is to provide robustness against small-to-medium channel estimation mismatch (CEM) that may arise from channel frequency response estimation error in the MC-CDMA system, which is modulated by downlink binary phase-shift keying (BPSK) under colored noise. Noncoherent demodulation schemes are preferable to coherent demodulation schemes, as the latter are difficult to implement over time-varying fading channels. Differential phase-shift keying (DPSK) is therefore the natural choice for an alternative modulation scheme. Furthermore, the new blind differential SOCP-based ICA (SOCP-ICA) detection without channel estimation and compensation will be proposed to combat Doppler spread caused by time-varying fading channels in the DPSK-modulated MC-CDMA system under colored noise. In this paper, numerical simulations are used to illustrate the robustness of the proposed blind coherent SOCP-ICA detector against small-to-medium CEM and to emphasize the advantage of the blind differential SOCP-ICA detector in overcoming Doppler spread.

  12. System-Level Performance of Antenna Arrays in CDMA-Based Cellular Mobile Radio Systems

    Science.gov (United States)

    Czylwik, Andreas; Dekorsy, Armin

    2004-12-01

    Smart antennas exploit the inherent spatial diversity of the mobile radio channel, provide an antenna gain, and also enable spatial interference suppression leading to reduced intracell as well as intercell interference. Especially, for the downlink of future CDMA-based mobile communications systems, transmit beamforming is seen as a well-promising smart antenna technique. The main objective of this paper is to study the performance of diverse antenna array topologies when applied for transmit beamforming in the downlink of CDMA-based networks. In this paper, we focus on uniform linear array (ULA) and uniform circular array (UCA) topologies. For the ULA, we consider three-sector base stations with one linear array per sector. While recent research on downlink beamforming is often restricted to one single cell, this study takes into account the important impact of intercell interference on the performance by evaluating complete networks. Especially, from the operator perspective, system capacity and system coverage are very essential parameters of a cellular system so that there is a clear necessity of intensive system level investigations. Apart from delivering assessments on the performance of the diverse antenna array topologies, in the paper also different antenna array parameters, such as element spacing and beamwidth of the sector antennas, are optimized. Although we focus on the network level, fast channel fluctuations are taken into account by including them analytically into the signal-to-interference calculation.

  13. System-Level Performance of Antenna Arrays in CDMA-Based Cellular Mobile Radio Systems

    Directory of Open Access Journals (Sweden)

    Dekorsy Armin

    2004-01-01

    Full Text Available Smart antennas exploit the inherent spatial diversity of the mobile radio channel, provide an antenna gain, and also enable spatial interference suppression leading to reduced intracell as well as intercell interference. Especially, for the downlink of future CDMA-based mobile communications systems, transmit beamforming is seen as a well-promising smart antenna technique. The main objective of this paper is to study the performance of diverse antenna array topologies when applied for transmit beamforming in the downlink of CDMA-based networks. In this paper, we focus on uniform linear array (ULA and uniform circular array (UCA topologies. For the ULA, we consider three-sector base stations with one linear array per sector. While recent research on downlink beamforming is often restricted to one single cell, this study takes into account the important impact of intercell interference on the performance by evaluating complete networks. Especially, from the operator perspective, system capacity and system coverage are very essential parameters of a cellular system so that there is a clear necessity of intensive system level investigations. Apart from delivering assessments on the performance of the diverse antenna array topologies, in the paper also different antenna array parameters, such as element spacing and beamwidth of the sector antennas, are optimized. Although we focus on the network level, fast channel fluctuations are taken into account by including them analytically into the signal-to-interference calculation.

  14. Channel coding for underwater acoustic single-carrier CDMA communication system

    Science.gov (United States)

    Liu, Lanjun; Zhang, Yonglei; Zhang, Pengcheng; Zhou, Lin; Niu, Jiong

    2017-01-01

    CDMA is an effective multiple access protocol for underwater acoustic networks, and channel coding can effectively reduce the bit error rate (BER) of the underwater acoustic communication system. For the requirements of underwater acoustic mobile networks based on CDMA, an underwater acoustic single-carrier CDMA communication system (UWA/SCCDMA) based on the direct-sequence spread spectrum is proposed, and its channel coding scheme is studied based on convolution, RA, Turbo and LDPC coding respectively. The implementation steps of the Viterbi algorithm of convolutional coding, BP and minimum sum algorithms of RA coding, Log-MAP and SOVA algorithms of Turbo coding, and sum-product algorithm of LDPC coding are given. An UWA/SCCDMA simulation system based on Matlab is designed. Simulation results show that the UWA/SCCDMA based on RA, Turbo and LDPC coding have good performance such that the communication BER is all less than 10-6 in the underwater acoustic channel with low signal to noise ratio (SNR) from -12 dB to -10dB, which is about 2 orders of magnitude lower than that of the convolutional coding. The system based on Turbo coding with Log-MAP algorithm has the best performance.

  15. Antijamming Performance of Adaptive Chaos Based CDMA System with MRC in Imperfect Channel Estimation Environment

    Directory of Open Access Journals (Sweden)

    Meher Krishna Patel

    2017-01-01

    Full Text Available This paper presents the antijamming performance of adaptive multiuser DS-CDMA system using maximal ratio combining technique in slow switching pulse noise jammer. Complex flat fading channel coefficients are assumed to be unknown at the receiver. Pilot symbols are used to estimate the fading coefficients using least mean square (LMS algorithm, and effect of imperfect channel estimation on bit error rate (BER is studied. Under the perfect synchronization conditions, probability of error in closed form is derived.

  16. Adaptive digital beamforming for a CDMA mobile communications payload

    Science.gov (United States)

    Munoz-Garcia, Samuel G.; Ruiz, Javier Benedicto

    1993-01-01

    In recent years, Spread-Spectrum Code Division Multiple Access (CDMA) has become a very popular access scheme for mobile communications due to a variety of reasons: excellent performance in multipath environments, high scope for frequency reuse, graceful degradation near saturation, etc. In this way, a CDMA system can support simultaneous digital communication among a large community of relatively uncoordinated users sharing a given frequency band. Nevertheless, there are also important problems associated with the use of CDMA. First, in a conventional CDMA scheme, the signature sequences of asynchronous users are not orthogonal and, as the number of active users increases, the self-noise generated by the mutual interference between users considerably degrades the performance, particularly in the return link. Furthermore, when there is a large disparity in received powers - due to differences in slant range or atmospheric attenuation - the non-zero cross-correlation between the signals gives rise to the so-called near-far problem. This leads to an inefficient utilization of the satellite resources and, consequently, to a drastic reduction in capacity. Several techniques were proposed to overcome this problem, such as Synchronized CDMA - in which the signature sequences of the different users are quasi-orthogonal - and power control. At the expense of increased network complexity and user coordination, these techniques enable the system capacity to be restored by equitably sharing the satellite resources among the users. An alternative solution is presented based upon the use of time-reference adaptive digital beamforming on board the satellite. This technique enables a high number of independently steered beams to be generated from a single phased array antenna, which automatically track the desired user signal and null the unwanted interference source. In order to use a time-reference adaptive antenna in a communications system, the main challenge is to obtain a

  17. Effects of optical layer impairments on 2.5 Gb/s optical CDMA transmission.

    Science.gov (United States)

    Feng, H; Mendez, A; Heritage, J; Lennon, W

    2000-07-03

    We conducted a computer simulation study to assess the effects of optical layer impairments on optical CDMA (O-CDMA) transmission of 8 asynchronous users at 2.5 Gb/s each user over a 214-km link. It was found that with group velocity dispersion compensation, two other residual effects, namely, the nonzero chromatic dispersion slope of the single mode fiber (which causes skew) and the non-uniform EDFA gain (which causes interference power level to exceed signal power level of some codes) degrade the signal to multi-access interference (MAI) ratio. In contrast, four wave mixing and modulation due to the Kerr and Raman contributions to the fiber nonlinear refractive index are less important. Current wavelength-division multiplexing (WDM) technologies, including dispersion management, EDFA gain flattening, and 3 rd order dispersion compensation, are sufficient to overcome the impairments to the O-CDMA transmission system that we considered.

  18. An information theory criteria based blind method for enumerating active users in DS-CDMA system

    Science.gov (United States)

    Samsami Khodadad, Farid; Abed Hodtani, Ghosheh

    2014-11-01

    In this paper, a new and blind algorithm for active user enumeration in asynchronous direct sequence code division multiple access (DS-CDMA) in multipath channel scenario is proposed. The proposed method is based on information theory criteria. There are two main categories of information criteria which are widely used in active user enumeration, Akaike Information Criterion (AIC) and Minimum Description Length (MDL) information theory criteria. The main difference between these two criteria is their penalty functions. Due to this difference, MDL is a consistent enumerator which has better performance in higher signal-to-noise ratios (SNR) but AIC is preferred in lower SNRs. In sequel, we propose a SNR compliance method based on subspace and training genetic algorithm to have the performance of both of them. Moreover, our method uses only a single antenna, in difference to the previous methods which decrease hardware complexity. Simulation results show that the proposed method is capable of estimating the number of active users without any prior knowledge and the efficiency of the method.

  19. PV-solar / wind hybrid energy system for GSM/CDMA type mobile telephony base station

    OpenAIRE

    Pragya Nema, R.K. Nema, Saroj Rangnekar

    2010-01-01

    This paper gives the design idea of optimized PV-Solar and Wind Hybrid Energy System for GSM/CDMA type mobile base station over conventional diesel generator for a particular site in central India (Bhopal) . For this hybrid system ,the meteorological data of Solar Insolation, hourly wind speed, are taken for Bhopal-Central India (Longitude 77o.23'and Latitude 23o.21' ) and the pattern of load consumption of mobile base station are studied and suitably modeled for optimization of the hybrid en...

  20. BER Performance Simulation of Generalized MC DS-CDMA System with Time-Limited Blackman Chip Waveform

    Directory of Open Access Journals (Sweden)

    I. Develi

    2010-09-01

    Full Text Available Multiple access interference encountered in multicarrier direct sequence-code division multiple access (MC DS-CDMA is the most important difficulty that depends mainly on the correlation properties of the spreading sequences as well as the shape of the chip waveforms employed. In this paper, bit error rate (BER performance of the generalized MC DS-CDMA system that employs time-limited Blackman chip waveform is presented for Nakagami-m fading channels. Simulation results show that the use of Blackman chip waveform can improve the BER performance of the generalized MC DS-CDMA system, as compared to the performances achieved by using timelimited chip waveforms in the literature.

  1. Hopfield neural network implementation of the optimal CDMA multiuser detector.

    Science.gov (United States)

    Kechriotis, G I; Manolakos, E S

    1996-01-01

    We investigate the application of Hopfield neural networks (HNN's) to the problem of multiuser detection in spread spectrum/CDMA (code division multiple access) communication systems. It is shown that the NP-complete problem of minimizing the objective function of the optimal multiuser detector (OMD) can be translated into minimizing an HNN "energy" function, thus allowing to take advantage of the ability of HNN's to perform very fast gradient descent algorithms in analog hardware and produce in real-time suboptimal solutions to hard combinatorial optimization problems. The performance of the proposed HNN receiver is evaluated via computer simulations and compared to that of other suboptimal schemes as well as to that of the OMD for both the synchronous and the asynchronous CDMA transmission cases. It is shown that the HNN detector exhibits a number of attractive properties and that it provides a powerful generalization of a well-known and extensively studied suboptimal scheme, namely the multistage detector.

  2. RBF multiuser detector with channel estimation capability in a synchronous MC-CDMA system.

    Science.gov (United States)

    Ko, K; Choi, S; Kang, C; Hong, D

    2001-01-01

    The authors propose a multiuser detector with channel estimation capability using a radial basis function (RBF) network in a synchronous multicarrier-code division multiple access (MC-CDMA) system. The authors propose to connect an RBF network to the frequency domain to effectively utilize the frequency diversity. Simulations were performed over frequency-selective and multi-path fading channels. These simulations confirmed that the proposed receiver can be used both for the channel estimation and as a multi-user receiver, thus permitting an increase in the number of active users.

  3. Design and implementation of signal processing scheme in CDMA wireless location systems

    Science.gov (United States)

    Yang, Tiejun; Fu, Hongliang

    2012-01-01

    Subscriber radio location techniques for code division multiple access (CDMA) cellular networks has been studied extensively in recent years. The network-based angle of arrival (AOA), time difference of arrival (TDOA), and time of arrival (TOA) techniques offer solutions to the position estimation problem. In this paper, The signal processing scheme of wireless location system based IS-95 is presented, in which TOA of reverse access channel transmissions is measured using sub-correlation detection algorithms and TOA estimation accuracy is improved using second search. Furthermore, reverse access channel decoding is implemented used to identify access channel message type, mobile identification, and dialed number.

  4. PV-solar / wind hybrid energy system for GSM/CDMA type mobile telephony base station

    Energy Technology Data Exchange (ETDEWEB)

    Nema, Pragya; Rangnekar, Saroj [Energy Engineering Department, Maulana Azad National Institute of Technology , Bhopal-462007 M.P. (India); Nema, R.K. [Electrical Engineering Department, Maulana Azad National Institute of Technology, Bhopal-462007 M.P. (India)

    2010-07-01

    This paper gives the design idea of optimized PV-Solar and Wind Hybrid Energy System for GSM/CDMA type mobile base station over conventional diesel generator for a particular site in central India (Bhopal). For this hybrid system ,the meteorological data of Solar Insolation, hourly wind speed, are taken for Bhopal-Central India (Longitude 77 deg.23'and Latitude 23 deg.21' ) and the pattern of load consumption of mobile base station are studied and suitably modeled for optimization of the hybrid energy system using HOMER software. The simulation and optimization result gives the best optimized sizing of wind turbine and solar array with diesel generator for particular GSM/CDMA type mobile telephony base station. This system is more cost effective and environmental friendly over the conventional diesel generator. It should reduced approximate 70%-80% fuel cost over conventional diesel generator and also reduced the emission of CO2 and other harmful gasses in environments. It is expected that the newly developed and installed system will provide very good opportunities for telecom sector in near future.

  5. Reverse Link CDMA System Capacity Evaluation for Stratospheric Platform Mobile Communications

    Directory of Open Access Journals (Sweden)

    Iskandar Iskandar

    2010-10-01

    Full Text Available We propose an analysis of reverse link CDMA multispot beam stratospheric platforms (SPF in this paper. The SPF is currently proposed as a novel wireless technology for the development of the next generation fixed and mobile communications. The geometry of this technology is different from that of the terrestrial but rather similar to the satellite based cellular system. However, evaluation on the CDMA system capacity of this technology has not been much reported. This paper addresses all possible multiple access interference analyses including the effects of channel fading and shadowing in order to evaluate the system capacity. Single SPF and multiple SPF model are evaluated under perfect power control and imperfect power control. The results indicate that in SPF systems the reverse link CDMA capacity is significantly reduced because of the power control imperfections. Moreover, in multiple SPF model the interference caused by the users in overlapped region is not trivial. We found that because of this problem the capacity is reduced for both speech and real-time data applications compared with the single SPF model even though the assumption of perfect power control can be made. In order to improve the system capacity we proposed two methods, first is to increase the minimum elevation angle definition for each platform and the second is to employ an adaptive antenna.

  6. High performance mixed optical CDMA system using ZCC code and multiband OFDM

    Science.gov (United States)

    Nawawi, N. M.; Anuar, M. S.; Junita, M. N.; Rashidi, C. B. M.

    2017-11-01

    In this paper, we have proposed a high performance network design, which is based on mixed optical Code Division Multiple Access (CDMA) system using Zero Cross Correlation (ZCC) code and multiband Orthogonal Frequency Division Multiplexing (OFDM) called catenated OFDM. In addition, we also investigate the related changing parameters such as; effective power, number of user, number of band, code length and code weight. Then we theoretically analyzed the system performance comprehensively while considering up to five OFDM bands. The feasibility of the proposed system architecture is verified via the numerical analysis. The research results demonstrated that our developed modulation solution can significantly enhanced the total number of user; improving up to 80% for five catenated bands compared to traditional optical CDMA system, with the code length equals to 80, transmitted at 622 Mbps. It is also demonstrated that the BER performance strongly depends on number of weight, especially with less number of users. As the number of weight increases, the BER performance is better.

  7. Blind Multiuser Detection for Long-Code CDMA Systems with Transmission-Induced Cyclostationarity

    Directory of Open Access Journals (Sweden)

    Ding Zhi

    2005-01-01

    Full Text Available We consider blind channel identification and signal separation in long-code CDMA systems. First, by modeling the received signals as cyclostationary processes with modulation-induced cyclostationarity, long-code CDMA system is characterized using a time-invariant system model. Secondly, based on the time-invariant model, multistep linear prediction method is used to reduce the intersymbol interference introduced by multipath propagation, and channel estimation then follows by utilizing the nonconstant modulus precoding technique with or without the matrix-pencil approach. The channel estimation algorithm without the matrix-pencil approach relies on the Fourier transform, and requires additional constraint on the code sequences other than being nonconstant modulus. It is found that by introducing a random linear transform, the matrix-pencil approach can remove (with probability one the extra constraint on the code sequences. Thirdly, after channel estimation, equalization is carried out using a cyclic Wiener filter. Finally, since chip-level equalization is performed, the proposed approach can readily be extended to multirate cases, either with multicode or variable spreading factor. Simulation results show that compared with the approach using the Fourier transform, the matrix-pencil-based approach can significantly improve the accuracy of channel estimation, therefore the overall system performance.

  8. Experience with synchronous and asynchronous digital control systems

    Science.gov (United States)

    Regenie, V. A.; Chacon, C. V.; Lock, W. P.

    1986-01-01

    Flight control systems have undergone a revolution since the days of simple mechanical linkages; presently the most advanced systems are full-authority, full-time digital systems controlling unstable aircraft. With the use of advanced control systems, the aerodynamic design can incorporate features that allow greater performance and fuel savings, as can be seen on the new Airbus design and advanced tactical fighter concepts. These advanced aircraft will be and are relying on the flight control system to provide the stability and handling qualities required for safe flight and to allow the pilot to control the aircraft. Various design philosophies have been proposed and followed to investigate system architectures for these advanced flight control systems. One major area of discussion is whether a multichannel digital control system should be synchronous or asynchronous. This paper addressed the flight experience at the Dryden Flight Research Facility of NASA's Ames Research Center with both synchronous and asynchronous digital flight control systems. Four different flight control systems are evaluated against criteria such as software reliability, cost increases, and schedule delays.

  9. Experience with synchronous and asynchronous digital control systems. [for flight

    Science.gov (United States)

    Regenie, Victoria A.; Chacon, Claude V.; Lock, Wilton P.

    1986-01-01

    Flight control systems have undergone a revolution since the days of simple mechanical linkages; presently the most advanced systems are full-authority, full-time digital systems controlling unstable aircraft. With the use of advanced control systems, the aerodynamic design can incorporate features that allow greater performance and fuel savings, as can be seen on the new Airbus design and advanced tactical fighter concepts. These advanced aircraft will be and are relying on the flight control system to provide the stability and handling qualities required for safe flight and to allow the pilot to control the aircraft. Various design philosophies have been proposed and followed to investigate system architectures for these advanced flight control systems. One major area of discussion is whether a multichannel digital control system should be synchronous or asynchronous. This paper addressed the flight experience at the Dryden Flight Research Facility of NASA's Ames Research Center with both synchronous and asynchronous digital flight control systems. Four different flight control systems are evaluated against criteria such as software reliability, cost increases, and schedule delays.

  10. Adaptive Rate-Scheduling with Reactive Delay Control for Next Generation CDMA Wireless Mobile Systems

    Directory of Open Access Journals (Sweden)

    Yu Oliver

    2006-01-01

    Full Text Available To minimize QoS degradations during nonstationary packet loadings, predictive rate schedulers adapt the operation according to anticipated packet arrival rates deduced via specified estimation algorithm. Existing predictive rate schedulers are developed under the assumption of perfect estimation, which may not be possible in future CDMA-based cellular networks characterized with highly nonstationary and bursty traffic. Additional shortcoming of existing rate schedulers is the coupling of delay and bandwidth, that is, close interdependence of delay and bandwidth (rate, whereby controlling one is accomplished solely by changing the other. In order to mitigate for the arrival rate estimation errors and delay-bandwidth coupling, this paper presents the feedback-enhanced target-tracking weighted fair queuing (FT-WFQ rate scheduler. It is an adaptive rate scheduler over multiclass CDMA systems with predictive adaptation control to adapt to nonstationary loadings; and feedback-enhanced reactive adaptation control to counteract arrival rate estimation errors. When the predictive adaptation control is not able to maintain long-term delay targets, feedback information will trigger reactive adaptation control. The objective of FT-WFQ scheduler is to minimize deviations from delay targets subject to maximum throughput utilization. Analytical and simulation results indicate that FT-WFQ is able to substantially reduce degradations caused by arrival rate estimation errors and to minimize delay degradations during nonstationary loading conditions.

  11. A Study on Channel Estimation Methods for Time-Domain Spreading MC-CDMA Systems

    Science.gov (United States)

    Nagate, Atsushi; Fujii, Teruya

    As a candidate for the transmission technology of next generation mobile communication systems, time-domain spreading MC-CDMA systems have begun to attract much attention. In these systems, data and pilot symbols are spread in the time domain and code-multiplexed. To combat fading issues, we need to conduct channel estimation by using the code-multiplexed pilot symbols. Especially in next generation systems, frequency bands higher than those of current systems, which raise the maximum Doppler frequency, are expected to be used, so that a more powerful channel estimation method is expected. Considering this, we propose a channel estimation method for highly accurate channel estimation; it is a combination of a two-dimensional channel estimation method and an impulse response-based channel estimation method. We evaluate the proposed method by computer simulations.

  12. Theoretical analysis and simulation of a code division multiple access system (cdma for secure signal transmission in wideband channels

    Directory of Open Access Journals (Sweden)

    Stevan M. Berber

    2014-06-01

    Full Text Available Chaotic spreading sequences can increase secrecy and resistance to interception in signal transmission. Chaos-based CDMA systems have been well investigated in the case of flat fading and noise presence in the channel. However, these systems operating in wideband channels, characterized by the frequency selective fading and white Gaussian noise, have not been investigated to the level of understanding their practical applications. This paper presents a detailed mathematical model of a CDMA system based on chaotic spreading sequences. In a theoretical analysis, all signals are represented in the discrete time domain. Using the theory of discrete time stochastic processes, the probability of error expressions are derived in a closed form for a multi-user chaos based CDMA system. For the sake of comparison, the expressions for the probability of error are derived separately for narrowband and wideband channels. The application of the system interleaving technique is investigated in particular, which showed that this technique can substantially improve probability of error in the system.  The system is simulated and the findings of the simulation confirmed theoretically expected results. Possible improvements in the probability of bit error due to multipath channel nature, with and without interleavers, are quantified depending on the random delay and the number of users in the system. In the analyzed system, a simplified version of the wideband channel model, proposed for modern wideband wireless networks, is used. Introduction Over the past years, the demand for wireless communications has increased substantially due to advancements in mobile communication systems and networks. Following these increasing demands, modern communication systems require the ability to handle a large number of users to process and transmit wideband signals through complex frequency selective channels. One of the techniques for transmission of multi-user signals is the

  13. The analysis of MAI in large scale MIMO-CDMA system

    Science.gov (United States)

    Berceanu, Madalina-Georgiana; Voicu, Carmen; Halunga, Simona

    2016-12-01

    Recently, technological development imposed a rapid growth in the use of data carried by cellular services, which also implies the necessity of higher data rates and lower latency. To meet the users' demands, it was brought into discussion a series of new data processing techniques. In this paper, we approached the MIMO technology that uses multiple antennas at the receiver and transmitter ends. To study the performances obtained by this technology, we proposed a MIMO-CDMA system, where image transmission has been used instead of random data transmission to take benefit of a larger range of quality indicators. In the simulations we increased the number of antennas, we observed how the performances of the system are modified and, based on that, we were able to make a comparison between a conventional MIMO and a Large Scale MIMO system, in terms of BER and MSSIM index, which is a metric that compares the quality of the image before transmission with the received one.

  14. Handover aspects for a Low Earth Orbit (LEO) CDMA Land Mobile Satellite (LMS) system

    Science.gov (United States)

    Carter, P.; Beach, M. A.

    1993-01-01

    This paper addresses the problem of handoff in a land mobile satellite (LMS) system between adjacent satellites in a low earth orbit (LEO) constellation. In particular, emphasis is placed on the application of soft handoff in a direct sequence code division multiple access (DS-CDMA) LMS system. Soft handoff is explained in terms of terrestrial macroscopic diversity, in which signals transmitted via several independent fading paths are combined to enhance the link quality. This concept is then reconsidered in the context of a LEO LMS system. A two-state Markov channel model is used to simulate the effects of shadowing on the communications path from the mobile to each satellite during handoff. The results of the channel simulation form a platform for discussion regarding soft handoff, highlighting the potential merits of the scheme when applied in a LEO LMS environment.

  15. Bi-orthogonal Symbol Mapping and Detection in Optical CDMA Communication System

    Science.gov (United States)

    Liu, Maw-Yang

    2017-12-01

    In this paper, the bi-orthogonal symbol mapping and detection scheme is investigated in time-spreading wavelength-hopping optical CDMA communication system. The carrier-hopping prime code is exploited as signature sequence, whose put-of-phase autocorrelation is zero. Based on the orthogonality of carrier-hopping prime code, the equal weight orthogonal signaling scheme can be constructed, and the proposed scheme using bi-orthogonal symbol mapping and detection can be developed. The transmitted binary data bits are mapped into corresponding bi-orthogonal symbols, where the orthogonal matrix code and its complement are utilized. In the receiver, the received bi-orthogonal data symbol is fed into the maximum likelihood decoder for detection. Under such symbol mapping and detection, the proposed scheme can greatly enlarge the Euclidean distance; hence, the system performance can be drastically improved.

  16. Performance Analysis of CDMA WLL Systems with Imperfect Power Control and Imperfect Sectorization

    Directory of Open Access Journals (Sweden)

    Sami A. El-Dolil

    2008-01-01

    Full Text Available Wireless local loop (WLL provides reliable, flexible, and economical access to the local telephone service using radio technology in the place of traditional wireline. In this paper, an analytical model is derived to evaluate the effect of both imperfect power control and imperfect sectorization on the performance of code division multiple access (CDMA WLL systems. The results show that the capacity degradation, due to imperfect power control, is about 25.8% and 11.5% for single cell and multiple cell systems, respectively. Increasing the overlapping angle from 0∘ to 5∘ causes the capacity gain to decrease from 6 to 5.53, while the corresponding sectorization efficiency drops from 100% to 92.3%.

  17. Cross-Layer Design and Analysis of Downlink Communications in Cellular CDMA Systems

    Directory of Open Access Journals (Sweden)

    Sun Jin Yuan

    2006-01-01

    Full Text Available A cellular CDMA network with voice and data communications is considered. Focusing on the downlink direction, we seek for the overall performance improvement which can be achieved by cross-layer analysis and design, taking physical layer, link layer, network layer, and transport layer into account. We are concerned with the role of each single layer as well as the interaction among layers, and propose algorithms/schemes accordingly to improve the system performance. These proposals include adaptive scheduling for link layer, priority-based handoff strategy for network admission control, and an algorithm for the avoidance of TCP spurious timeouts at the transport layer. Numerical results show the performance gain of each proposed scheme over independent performance of an individual layer in the wireless mobile network. We conclude that the system performance in terms of capacity, throughput, dropping probability, outage, power efficiency, delay, and fairness can be enhanced by jointly considering the interactions across layers.

  18. H∞ Controller Design for Asynchronous Hybrid Systems with Multiple Delays

    Directory of Open Access Journals (Sweden)

    Xiaoqiang Sun

    2016-01-01

    Full Text Available Solutions for the H∞ synthesis problems of asynchronous hybrid systems with input-output delays are proposed. The continuous-time lifting approach of sampled-data systems is extended to a hybrid system with multiple delays, and some feasible formulas to calculate the operators of the equivalent discrete-time (DT system are given. Different from the existing methods derived from symplectic pair theory or by state augmentation, a Lyapunov-Krasovskii functional to solve the synthesis problem is explicitly constructed. The delay-dependent stability conditions we obtained can be described in terms of nonstrict linear matrix inequalities (LMIs, which are much more convenient to be solved by LMI tools.

  19. CP decomposition approach to blind separation for DS-CDMA system using a new performance index

    Science.gov (United States)

    Rouijel, Awatif; Minaoui, Khalid; Comon, Pierre; Aboutajdine, Driss

    2014-12-01

    In this paper, we present a canonical polyadic (CP) tensor decomposition isolating the scaling matrix. This has two major implications: (i) the problem conditioning shows up explicitly and could be controlled through a constraint on the so-called coherences and (ii) a performance criterion concerning the factor matrices can be exactly calculated and is more realistic than performance metrics used in the literature. Two new algorithms optimizing the CP decomposition based on gradient descent are proposed. This decomposition is illustrated by an application to direct-sequence code division multiplexing access (DS-CDMA) systems; computer simulations are provided and demonstrate the good behavior of these algorithms, compared to others in the literature.

  20. Coherent Code Tracking for Spatial Transmit Diversity DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    R. W. Stewart

    2005-09-01

    Full Text Available Spatial transmit diversity schemes are now well integrated into third-generation cellular mobile communication system specifications. When DS-CDMA-based technology is deployed in typical macro- and microcell environments, multipath diversity and spatial diversity may be exploited simultaneously by a 2D RAKE receiver. The work presented in this paper focuses on taking advantage of spatial transmit diversity in synchronising the 2D RAKE structure. We investigate the use of coherent and noncoherent techniques for tracking the timing parameters of each multipath component. It is shown that both noncoherent and coherent techniques benefit from transmit diversity. Additionally the performance gap between these two techniques increases with the number of antennas.

  1. Exploring Asynchronous Many-Task Runtime Systems toward Extreme Scales

    Energy Technology Data Exchange (ETDEWEB)

    Knight, Samuel [O8953; Baker, Gavin Matthew; Gamell, Marc [Rutgers U; Hollman, David [08953; Sjaardema, Gregor [SNL; Kolla, Hemanth [SNL; Teranishi, Keita; Wilke, Jeremiah J; Slattengren, Nicole [SNL; Bennett, Janine Camille

    2015-10-01

    Major exascale computing reports indicate a number of software challenges to meet the dramatic change of system architectures in near future. While several-orders-of-magnitude increase in parallelism is the most commonly cited of those, hurdles also include performance heterogeneity of compute nodes across the system, increased imbalance between computational capacity and I/O capabilities, frequent system interrupts, and complex hardware architectures. Asynchronous task-parallel programming models show a great promise in addressing these issues, but are not yet fully understood nor developed su ciently for computational science and engineering application codes. We address these knowledge gaps through quantitative and qualitative exploration of leading candidate solutions in the context of engineering applications at Sandia. In this poster, we evaluate MiniAero code ported to three leading candidate programming models (Charm++, Legion and UINTAH) to examine the feasibility of these models that permits insertion of new programming model elements into an existing code base.

  2. BER Analysis of Various Channel Equalization Schemes of a QO-STBC Encoded OFDM based MIMO CDMA System

    OpenAIRE

    Husnul Ajra; Md. Zahid Hasan; Md. Shohidul Islam

    2014-01-01

    Quasi Orthogonal Space Time Block Code (QO-STBC) can provide full-rate transmission and low decoding complexity. This paper deals with channel estimation for Quasi Orthogonal Space Time Block Code (QO-STBC) encoded Orthogonal Frequency Division Multiplexing (OFDM) based Multiple Input multiple Output (MIMO) Code Division Multiple Access (CDMA) system. Using the QO-STBC coding property, we analysis the weight performance that reduce the computational complexity of system. The design of channel...

  3. UNIVERSAL REGULAR AUTONOMOUS ASYNCHRONOUS SYSTEMS: ω-LIMIT SETS, INVARIANCE AND BASINS OF ATTRACTION

    Directory of Open Access Journals (Sweden)

    Serban Vlad

    2011-07-01

    Full Text Available The asynchronous systems are the non-deterministic real timebinarymodels of the asynchronous circuits from electrical engineering.Autonomy means that the circuits and their models have no input.Regularity means analogies with the dynamical systems, thus such systems may be considered to be real time dynamical systems with a’vector field’, Universality refers to the case when the state space of the system is the greatest possible in the sense of theinclusion. The purpose of this paper is that of defining, by analogy with the dynamical systems theory, the omega-limit sets, the invariance and the basins of attraction of the universal regular autonomous asynchronous systems.

  4. Maximal Ratio Combining Using Channel Estimation in Chaos Based Pilot-Added DS-CDMA System with Antenna Diversity

    Directory of Open Access Journals (Sweden)

    Meher Krishna Patel

    2017-01-01

    Full Text Available This paper presents an adaptive multiuser transceiver scheme for DS-CDMA systems in which pilot symbols are added to users’ data to estimate complex channel fading coefficients. The performance of receiver antenna diversity with maximal ratio combining (MRC technique is analyzed for imperfect channel estimation in flat fading environments. The complex fading coefficients are estimated using least mean square (LMS algorithm and these coefficients are utilized by the maximal ratio combiner for generating the decision variable. Probability of error in closed form is derived. Further, the effect of pilot signal power on bit error rate (BER and BER performance of multiplexed pilot and data signal transmission scenario are investigated. We have compared the performance of added and multiplexed pilot-data systems and concluded the advantages of both systems. The proposed CDMA technique uses the chaotic sequence as spreading sequence. Assuming proper synchronization, the computer simulation results demonstrate the better bit error rate performance in the presence of channel estimator in the chaotic based CDMA system and the receiver antenna diversity technique further improves the performance of the proposed system. Also, no channel estimator is required if there is no phase distortion to the transmitted signal.

  5. Adaptive Channel-Tracking Method and Equalization for MC-CDMA Systems over Rapidly Fading Channel under Colored Noise

    Directory of Open Access Journals (Sweden)

    Chen Bor-Sen

    2010-01-01

    Full Text Available A recursive maximum-likelihood (RML algorithm for channel estimation under rapidly fading channel and colored noise in a multicarrier code-division multiple-access (MC-CDMA system is proposed in this paper. A moving-average model with exogenous input (MAX is given to describe the transmission channel and colored noise. Based on the pseudoregression method, the proposed RML algorithm can simultaneously estimate the parameters of channel and colored noise. Following the estimation results, these parameters can be used to enhance the minimum mean-square error (MMSE equalizer. Considering high-speed mobile stations, a one-step linear trend predictor is added to improve symbol detection. Simulation results indicate that the proposed RML estimator can track the channel more precisely than the conventional estimator. Meanwhile, the performance of the proposed enhanced MMSE equalizer is robust to the rapidly Rayleigh fading channel under colored noise in the MC-CDMA systems.

  6. Adaptive Channel-Tracking Method and Equalization for MC-CDMA Systems over Rapidly Fading Channel under Colored Noise

    Science.gov (United States)

    Yang, Chang-Yi; Chen, Bor-Sen

    2010-12-01

    A recursive maximum-likelihood (RML) algorithm for channel estimation under rapidly fading channel and colored noise in a multicarrier code-division multiple-access (MC-CDMA) system is proposed in this paper. A moving-average model with exogenous input (MAX) is given to describe the transmission channel and colored noise. Based on the pseudoregression method, the proposed RML algorithm can simultaneously estimate the parameters of channel and colored noise. Following the estimation results, these parameters can be used to enhance the minimum mean-square error (MMSE) equalizer. Considering high-speed mobile stations, a one-step linear trend predictor is added to improve symbol detection. Simulation results indicate that the proposed RML estimator can track the channel more precisely than the conventional estimator. Meanwhile, the performance of the proposed enhanced MMSE equalizer is robust to the rapidly Rayleigh fading channel under colored noise in the MC-CDMA systems.

  7. Uniform Circular Antenna Array Applications in Coded DS-CDMA Mobile Communication Systems

    National Research Council Canada - National Science Library

    Seow, Tian

    2003-01-01

    ...) has greatly increased. This thesis examines the use of an equally spaced circular adaptive antenna array at the mobile station for a typical coded direct sequence code division multiple access (DS-CDMA...

  8. Multiple-access interference in 2-D wavelength/time optical CDMA system with optical hard-limiters

    Science.gov (United States)

    Chovan, Jozef; Uherek, František

    2005-08-01

    In this paper we present the proposed modification of 2-D wavelength/time (WIT) decoder1 by placing the second optical hard-limiter (0-HL) after decoder"s last optical coupler. The MA1 improvement of the 2-D W/T Optical Code Division Multiple Access (0-CDMA) system for the cases of 2D WIT decoder with one and with two 0-HLs is analyzed. Average value of signal-to-interference difference (SID) is used as the MA1 merit. The model of such 2D W/T 0-CDMA system for numerical calculation of the SID is proposed and presented in this paper. In the analyzed system, 2-D WIT Generalized Multiwavelength Prime Codewords (GMWPC), which are generated by algorithm reported in2 are used for achieving multiple-access. We assume the implemented 0-HL proposed in 3. The properties of such 0-HL were approximated [4] and its two ideality parameters, which characterize the measure of its ideality, were defined. The input and output time optical pulses sequence of W/T 0-CDMA decoder is numerical simulated. Dependencies of SID versus the weight of codeword and the number of active users in the system are presented. The influence of the properties used 0-HLs is evaluated.

  9. Analysis of a Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Multipath Rician Fading Channels

    National Research Council Canada - National Science Library

    Kim Yong-Seok; Whang Keum-Chan

    2005-01-01

    We present the BER analysis of antenna array (AA) receiver in reverse-link asynchronous multipath Rician channels and analyze the performance of an improved AA system which applies a reverse-link synchronous transmission technique (RLSTT...

  10. Code-Division Multiple-Access (CDMA)

    DEFF Research Database (Denmark)

    Justesen, Jørn

    1999-01-01

    A simplified CDMA system is presented. A single-user approach and a multi-user approach to demodulation of transmitted bits is presented.......A simplified CDMA system is presented. A single-user approach and a multi-user approach to demodulation of transmitted bits is presented....

  11. Asynchronous web-based patient-centered home telemedicine system.

    Science.gov (United States)

    Lau, Christopher; Churchill, R Sean; Kim, Janice; Matsen, Frederick A; Kim, Yongmin

    2002-12-01

    A web-based system for asynchronous multimedia messaging between shoulder replacement surgery patients at home and their surgeons was developed and tested. A web browser plug-in simplifies the process of capturing video and transferring it to a web site for novice computer users. The design of the video capture plug-in can be reused to acquire and securely transfer any type of data over the web. For example, readings from home biosensor instruments (e.g., glucometers and spirometers) that can be connected to a personal computer can be transferred to a home telemedicine web site. Both patients and doctors can access this web site to monitor health status longitudinally. Six patients, whose familiarity with computers ranged from no experience to expert users, used the system. All of the subjects were able to use the system to check treatment reminders and to send at least one message with video to their surgeons. The surgeons monitored the system regularly and always responded to messages within 24 h during the six-month trial period.

  12. [System of telesonography with synchronous teleconsultations and asynchronous telediagnoses (Togo)].

    Science.gov (United States)

    Adambounou, K; Farin, F; Boucher, A; Adjenou, K V; Gbeassor, M; N'dakena, K; Vincent, N; Arbeille, P

    2012-01-01

    Ultrasonography is an important nonirradiating diagnostic medical imaging procedure, frequently used, especially in urgent circumstances. This relatively inexpensive noninvasive examination makes it possible to diagnose disorders in various parts of the human body, by examining, for example, the abdomen and pelvis, the cardiovascular system, and the muscles and joints. Ultrasound is also an operator-dependent examination, in that the quality of the result depends on precision in the manipulation of the probe. Unfortunately, many small medical centers and isolated sites do not have an appropriate well-trained sonographer to perform initial evaluations, and an untrained operator cannot capture the appropriate echographic views required for a safe diagnosis of current patients, even with realtime vocal guidance (personal data). The lack of experienced physicians or qualified technicians means that diagnostic ultrasound is not always accessible to patients for rapid examination worldwide, especially in Africa, Amazonia or near the North or South Poles. This situation has led to the development of a new concept of telemedicine: telesonography, with a remote ultrasound diagnosis either in real time (synchronous) or delayed (asynchronous; store-and-forward). These systems of real-time telesonography and data transmission require expensive and complex technology with sophisticated equipment not available in many developing countries. The purpose of this study is to design a low-cost real-time system of telesonography for teleconsultations with experts and a delayed telediagnostic mode between isolated peripheral hospitals and a University Hospital center (UHC). An IP camera and an internet video server were installed in a geographically isolated site equipped with an ultrasound machine and an operator with basic training in its use. Synchronous teleconsultation (second-opinion diagnosis) is possible via internet with a UHC expert. If no ultrasound operator is available at

  13. On Intercell Interference and Its Cancellation in Cellular Multicarrier CDMA Systems

    Directory of Open Access Journals (Sweden)

    Simon Plass

    2007-11-01

    Full Text Available The handling of intercell interference at the cell border area is a strong demand in future communication systems to guarantee efficient use of the available bandwidth. Therefore, this paper focuses on the application of iterative intercell interference cancellation schemes in cellular multicarrier code division multiple access (MC-CDMA systems at the receiver side for the downlink. First, the influence of the interfering base stations to the total intercell interference is investigated. Then, different concepts for intercell interference cancellation are described and investigated for scenarios with several interfering cells. The first approach is based on the use of the hard decision of the demodulator to reconstruct the received signals. This does not require the higher amount of complexity compared to the second approach which is based on the use of the more reliable soft values from the decoding process. Furthermore, the extrinsic information as a reliability measure of this soft iterative cancellation process is investigated in more detail based on the geographical position of the mobile terminal. Both approaches show significant performance gains in the severe cell border area. With the soft intercell interference cancellation scheme, it is possible to reach the single-user bound. Therefore, the intercell interference can be almost eliminated.

  14. On Intercell Interference and Its Cancellation in Cellular Multicarrier CDMA Systems

    Directory of Open Access Journals (Sweden)

    Plass Simon

    2008-01-01

    Full Text Available Abstract The handling of intercell interference at the cell border area is a strong demand in future communication systems to guarantee efficient use of the available bandwidth. Therefore, this paper focuses on the application of iterative intercell interference cancellation schemes in cellular multicarrier code division multiple access (MC-CDMA systems at the receiver side for the downlink. First, the influence of the interfering base stations to the total intercell interference is investigated. Then, different concepts for intercell interference cancellation are described and investigated for scenarios with several interfering cells. The first approach is based on the use of the hard decision of the demodulator to reconstruct the received signals. This does not require the higher amount of complexity compared to the second approach which is based on the use of the more reliable soft values from the decoding process. Furthermore, the extrinsic information as a reliability measure of this soft iterative cancellation process is investigated in more detail based on the geographical position of the mobile terminal. Both approaches show significant performance gains in the severe cell border area. With the soft intercell interference cancellation scheme, it is possible to reach the single-user bound. Therefore, the intercell interference can be almost eliminated.

  15. Modeling and Analysis of Asynchronous Systems Using SAL and Hybrid SAL

    Science.gov (United States)

    Tiwari, Ashish; Dutertre, Bruno

    2013-01-01

    We present formal models and results of formal analysis of two different asynchronous systems. We first examine a mid-value select module that merges the signals coming from three different sensors that are each asynchronously sampling the same input signal. We then consider the phase locking protocol proposed by Daly, Hopkins, and McKenna. This protocol is designed to keep a set of non-faulty (asynchronous) clocks phase locked even in the presence of Byzantine-faulty clocks on the network. All models and verifications have been developed using the SAL model checking tools and the Hybrid SAL abstractor.

  16. Development of a mobile emergency patient information and imaging communication system based on CDMA-1X EVDO

    Science.gov (United States)

    Yang, Keon Ho; Jung, Haijo; Kang, Won-Suk; Jang, Bong Mun; Kim, Joong Il; Han, Dong Hoon; Yoo, Sun-Kook; Yoo, Hyung-Sik; Kim, Hee-Joung

    2006-03-01

    The wireless mobile service with a high bit rate using CDMA-1X EVDO is now widely used in Korea. Mobile devices are also increasingly being used as the conventional communication mechanism. We have developed a web-based mobile system that communicates patient information and images, using CDMA-1X EVDO for emergency diagnosis. It is composed of a Mobile web application system using the Microsoft Windows 2003 server and an internet information service. Also, a mobile web PACS used for a database managing patient information and images was developed by using Microsoft access 2003. A wireless mobile emergency patient information and imaging communication system is developed by using Microsoft Visual Studio.NET, and JPEG 2000 ActiveX control for PDA phone was developed by using the Microsoft Embedded Visual C++. Also, the CDMA-1X EVDO is used for connections between mobile web servers and the PDA phone. This system allows fast access to the patient information database, storing both medical images and patient information anytime and anywhere. Especially, images were compressed into a JPEG2000 format and transmitted from a mobile web PACS inside the hospital to the radiologist using a PDA phone located outside the hospital. Also, this system shows radiological images as well as physiological signal data, including blood pressure, vital signs and so on, in the web browser of the PDA phone so radiologists can diagnose more effectively. Also, we acquired good results using an RW-6100 PDA phone used in the university hospital system of the Sinchon Severance Hospital in Korea.

  17. A CDMA Spotbeam Architecture for the Next Generation Satellite System (NGSS) for the Aeronautical Telecommunications Network (ATN)

    Science.gov (United States)

    Raghavan, Rajesh S.; Shamma, Mohammed A.

    2003-01-01

    This paper will present work being done to model and simulate a CDMA based Mobile Satellite System architecture for providing all or part of the future Air Traffic Management (ATM) services. Such a system, will help in relieving the dependence on ground based networks, if not eliminate it. Additionally such an architecture can be used in parallel or as a supplementary service along with ground based links to help alleviate any capacity bottlenecks, or in areas where such services are difficult to make available such as in oceanic, remote areas outside the jet highways, or in developing countries where ground services are less available.

  18. Bit Error Rate Performance of a MIMO-CDMA System Employing Parity-Bit-Selected Spreading in Frequency Nonselective Rayleigh Fading

    Directory of Open Access Journals (Sweden)

    Claude D'Amours

    2011-01-01

    Full Text Available We analytically derive the upper bound for the bit error rate (BER performance of a single user multiple input multiple output code division multiple access (MIMO-CDMA system employing parity-bit-selected spreading in slowly varying, flat Rayleigh fading. The analysis is done for spatially uncorrelated links. The analysis presented demonstrates that parity-bit-selected spreading provides an asymptotic gain of 10log(Nt dB over conventional MIMO-CDMA when the receiver has perfect channel estimates. This analytical result concurs with previous works where the (BER is determined by simulation methods and provides insight into why the different techniques provide improvement over conventional MIMO-CDMA systems.

  19. Low-power Implementation of an Encryption/Decryption System with Asynchronous Techniques

    Directory of Open Access Journals (Sweden)

    Nikos Sklavos

    2002-01-01

    Full Text Available An asynchronous VLSI implementation of the International Data Encryption Algorithm (IDEA is presented in this paper. In order to evaluate the asynchronous design a synchronous version of the algorithm was also designed. VHDL hardware description language was used in order to describe the algorithm. By using Synopsys commercial available tools the VHDL code was synthesized. After placing and routing both designs were fabricated with 0.6 μm CMOS technology. With a system clock of up to 8 MHz and a power supply of 5 V the two chips were tested and evaluated comparing with the software implementation of the IDEA algorithm. This new approach proves efficiently the lowest power consumption of the asynchronous implementation compared to the existing synchronous. Therefore, the asynchronous chip performs efficiently in Wireless Encryption Protocols and high speed networks.

  20. All-optical differential detection for suppressing multiple-access interference in coherent time-addressed optical CDMA systems.

    Science.gov (United States)

    Kim, Sun-Jong; Kim, Tae-Young; Park, Chul; Park, Chang-Soo; Chun, Young

    2004-05-03

    A novel scheme for suppressing the multiple-access interference (MAI) in coherent time-addressed optical CDMA systems is proposed. This is based on a differential detection using the dual-control NOLM. The basic principle for MAI suppression is described. For experimental demonstration, two encoded channels are constructed and decoded. These decoded signals are sent to the dual-control NOLM and a high autocorrelation peak with suppressed MAI at the output of NOLM is observed. Signal-to-interference ratio is improved by 7 dB.

  1. Performance improvement of FSO/CDMA systems over dispersive turbulence channel using multi-wavelength PPM signaling.

    Science.gov (United States)

    Dang, Ngoc T; Pham, Anh T

    2012-11-19

    Previous studies show that, compared to on-off keying (OOK) signaling, pulse-position modulation (PPM) is favorable in FSO/CDMA systems thanks to its energy efficiency and simple detection. Nevertheless, when the system bit rate increases and the transmission distance is far, the FSO/CDMA systems using PPM signaling critically suffer from the impact of pulse broadening caused by dispersion, especially when the modulation level is high. In this paper, we therefore propose to use multi-wavelength PPM (MWPPM) signaling to overcome the limitation of PPM. To further improve the system performance, avalanche photodiode (APD) is also used. The performance of the proposed system is theoretically analyzed using a realistic model of Gaussian pulse propagation. To model the impact of intensity fluctuation caused by the atmospheric turbulence, the log-normal channel is used. We find that, by using MWPPM, the effects of both intensity fluctuation and pulse broadening are mitigated, the BER is therefore significantly improved. Additionally, we quantitatively show that the system performance is further improved by using APD, especially when the average APD gain is chosen properly.

  2. Intercarrier interference reduction in MC-CDMA system through second order duobinary coded phase rotated conjugate cancellation scheme.

    Science.gov (United States)

    Chitra, S; Kumaratharan, N

    2015-01-01

    Multi-carrier code division multiple access (MC-CDMA) technique is one of the strong candidates for next generation wireless mobile communication systems. Multi-carrier systems are very much sensitive to carrier frequency offset (CFO) results in intercarrier interference (ICI). To mitigate ICI without any spectral loss, a second order duobinary coded phase rotated conjugate cancellation algorithm is proposed in this paper. In the conventional phase rotated conjugate cancellation (PRCC) technique, one path carries the MC-CDMA signal with a phase spin of ϕ and the other path carries the conjugate of the first path signal with -ϕ phase spin. This artificial phase rotation allows the transmitter to tune the transmitted signals so that the ICI effects could be mutually cancelled at the receiver. Although the PRCC technique reduces the spectral efficiency, the limitation can be overcome by the joint second order duobinary coding scheme with PRCC technique. In the proposed method, the correlative coding between the binary symbols modulated on adjacent subcarriers is used to reduce the ICI without any spectral loss. Simulation results show that the proposed PRCC method provides better carrier to interference ratio (CIR) and bit error rate (BER) performances compared to the conventional conjugate cancellation (CC) technique.

  3. Intercarrier interference reduction in MC-CDMA system through second order duobinary coded phase rotated conjugate cancellation scheme.

    Directory of Open Access Journals (Sweden)

    S Chitra

    Full Text Available Multi-carrier code division multiple access (MC-CDMA technique is one of the strong candidates for next generation wireless mobile communication systems. Multi-carrier systems are very much sensitive to carrier frequency offset (CFO results in intercarrier interference (ICI. To mitigate ICI without any spectral loss, a second order duobinary coded phase rotated conjugate cancellation algorithm is proposed in this paper. In the conventional phase rotated conjugate cancellation (PRCC technique, one path carries the MC-CDMA signal with a phase spin of ϕ and the other path carries the conjugate of the first path signal with -ϕ phase spin. This artificial phase rotation allows the transmitter to tune the transmitted signals so that the ICI effects could be mutually cancelled at the receiver. Although the PRCC technique reduces the spectral efficiency, the limitation can be overcome by the joint second order duobinary coding scheme with PRCC technique. In the proposed method, the correlative coding between the binary symbols modulated on adjacent subcarriers is used to reduce the ICI without any spectral loss. Simulation results show that the proposed PRCC method provides better carrier to interference ratio (CIR and bit error rate (BER performances compared to the conventional conjugate cancellation (CC technique.

  4. A Joint Optimization Criterion for Blind DS-CDMA Detection

    Directory of Open Access Journals (Sweden)

    Sergio A. Cruces-Alvarez

    2007-01-01

    Full Text Available This paper addresses the problem of the blind detection of a desired user in an asynchronous DS-CDMA communications system with multipath propagation channels. Starting from the inverse filter criterion introduced by Tugnait and Li in 2001, we propose to tackle the problem in the context of the blind signal extraction methods for ICA. In order to improve the performance of the detector, we present a criterion based on the joint optimization of several higher-order statistics of the outputs. An algorithm that optimizes the proposed criterion is described, and its improved performance and robustness with respect to the near-far problem are corroborated through simulations. Additionally, a simulation using measurements on a real software-radio platform at 5 GHz has also been performed.

  5. A Unified Approach to the Analysis of Multicarrier DS-CDMA over Nakagami-$M$ Fading Channels

    OpenAIRE

    Yang, L-L.; Hanzo, L.

    2001-01-01

    A class of unified multicarrier DS-CDMA (MC DS-CDMA) schemes is defined and its performance is considered over multipath Nakagami-$M$ fading channels. The spacing between two adjacent subcarriers of the unified MC DS-CDMA scheme is a variable, allowing us to gain insight into the effects of the spacing on the bit error rate (BER) performance of MC DS-CDMA systems. This unified MC DS-CDMA scheme includes the subclasses of multitone DS-CDMA and orthogonal MC DS-CDMA as special cases. The optimu...

  6. Quadrature amplitude modulation from basics to adaptive trellis-coded turbo-equalised and space-time coded OFDM CDMA and MC-CDMA systems

    CERN Document Server

    Hanzo, Lajos

    2004-01-01

    "Now fully revised and updated, with more than 300 pages of new material, this new edition presents the wide range of recent developments in the field and places particular emphasis on the family of coded modulation aided OFDM and CDMA schemes. In addition, it also includes a fully revised chapter on adaptive modulation and a new chapter characterizing the design trade-offs of adaptive modulation and space-time coding." "In summary, this volume amalgamates a comprehensive textbook with a deep research monograph on the topic of QAM, ensuring it has a wide-ranging appeal for both senior undergraduate and postgraduate students as well as practicing engineers and researchers."--Jacket.

  7. Beyond an Institutionalized Learning Environment: Fostering Interactions and Learning Using Synchronous and Asynchronous Messaging Systems

    Directory of Open Access Journals (Sweden)

    Nikki Philline C. DE LA ROSA

    2004-07-01

    Full Text Available Beyond an Institutionalized Learning Environment: Fostering Interactions and Learning Using Synchronous and Asynchronous Messaging Systems Ma. Luisa D. MARIANO Nikki Philline C. DE LA ROSA University of the Philippines Open University-PHILIPPINE ABSTRACT This paper seeks to examine the use of synchronous and asynchronous messaging systems with distance education students and the implications for student interaction and learning in the institutionalized Integrated Virtual Learning Environment (IVLE of the University of the Philippines Open University (UPOU. It will present, as a case in point, the learning experiences of UPOU students in obtaining tutorial support and using the IVLE and alternative synchronous and asynchronous messaging systems to maximize and facilitate online activities involving the Faculty-in-Charge, Tutor, UPOU support staff and the students.

  8. Asynchronous control of discrete-time impulsive switched systems with mode-dependent average dwell time.

    Science.gov (United States)

    Wang, Bo; Zhang, Hongbin; Wang, Gang; Dang, Chuangyin; Zhong, Sijun

    2014-03-01

    This paper mainly studies the asynchronous control problem for a class of discrete-time impulsive switched systems, where "asynchronous" means the switching of the controllers has a lag to the switching of system modes. By using multiple Lyapunov functions (MLFs), the much looser asymptotic stability result of closed-loop systems is derived with a mode-dependent average dwell time (MDADT) technique. Based on the stability result obtained, the problem of asynchronous control is solved under a proper switching law. Moreover, the stability and stabilization results are formulated in form of matrix inequalities that are numerically feasible. Finally, an illustrative numerical example is presented to show the effectiveness of the obtained stability results. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

  9. W-CDMA - Spread Spectrum

    DEFF Research Database (Denmark)

    Jakobsen, Kaj Bjarne

    1999-01-01

    Specifications, Direct Sequence, Frequency Hopping, Hybrid, W-CDMA, and Power Amplifier Linearisation.......Specifications, Direct Sequence, Frequency Hopping, Hybrid, W-CDMA, and Power Amplifier Linearisation....

  10. Defining the Symmetry of the Universal Semi-Regular Autonomous Asynchronous Systems

    Directory of Open Access Journals (Sweden)

    Serban E. Vlad

    2012-02-01

    Full Text Available The regular autonomous asynchronous systems are the non-deterministic Boolean dynamical systems and universality means the greatest in the sense of the inclusion. The paper gives four definitions of symmetry of these systems in a slightly more general framework, called semi-regularity, and also many examples.

  11. A satellite mobile communication system based on Band-Limited Quasi-Synchronous Code Division Multiple Access (BLQS-CDMA)

    Science.gov (United States)

    Degaudenzi, R.; Elia, C.; Viola, R.

    1990-01-01

    Discussed here is a new approach to code division multiple access applied to a mobile system for voice (and data) services based on Band Limited Quasi Synchronous Code Division Multiple Access (BLQS-CDMA). The system requires users to be chip synchronized to reduce the contribution of self-interference and to make use of voice activation in order to increase the satellite power efficiency. In order to achieve spectral efficiency, Nyquist chip pulse shaping is used with no detection performance impairment. The synchronization problems are solved in the forward link by distributing a master code, whereas carrier forced activation and closed loop control techniques have been adopted in the return link. System performance sensitivity to nonlinear amplification and timing/frequency synchronization errors are analyzed.

  12. An Asynchronous Time-Division-Multiplexed Network-on-Chip for Real-Time Systems

    DEFF Research Database (Denmark)

    Kasapaki, Evangelia

    Multi-processor architectures using networks-on-chip (NOCs) for communication are becoming the standard approach in the development of embedded systems and general purpose platforms. Typically, multi-processor platforms follow a globally asynchronous locally synchronous (GALS) timing organization...... more flexible timing within its structure, to address signal distribution issues, using a network of synchronous routers. NOCs consist of a switching structure of routers connected by links, with network interfaces (NIs) that connect the processors to the switching structure. Argo uses a novel NI...... design that supports time-predictability, and asynchronous routers that form a time-elastic network. The NI design integrates the DMA functionality and the TDM schedule, and uses dual-ported local memories. The routers combine the router functionality and asynchronous elastic behavior. They also use...

  13. Minimum Mean-Squared Error Iterative Successive Parallel Arbitrated Decision Feedback Detectors for DS-CDMA Systems

    CERN Document Server

    de Lamare, Rodrigo C

    2012-01-01

    In this paper we propose minimum mean squared error (MMSE) iterative successive parallel arbitrated decision feedback (DF) receivers for direct sequence code division multiple access (DS-CDMA) systems. We describe the MMSE design criterion for DF multiuser detectors along with successive, parallel and iterative interference cancellation structures. A novel efficient DF structure that employs successive cancellation with parallel arbitrated branches and a near-optimal low complexity user ordering algorithm are presented. The proposed DF receiver structure and the ordering algorithm are then combined with iterative cascaded DF stages for mitigating the deleterious effects of error propagation for convolutionally encoded systems with both Viterbi and turbo decoding as well as for uncoded schemes. We mathematically study the relations between the MMSE achieved by the analyzed DF structures, including the novel scheme, with imperfect and perfect feedback. Simulation results for an uplink scenario assess the new it...

  14. Trajectory exploration within asynchronous binary asteroid systems using refined Lagrangian coherent structures

    Science.gov (United States)

    Shang, Haibin; Wu, Xiaoyu; Cui, Pingyuan

    2017-02-01

    Ground observations have found that asynchronous systems constitute most of the population of the near-Earth binary asteroids. This paper concerns the trajectory of a particle in the asynchronous system which is systematically described using periodic ellipsoidal and spherical body models. Due to the non-autonomous characteristics of the asynchronous system, Lagrangian coherent structures (LCS) are employed to identify the various dynamical behaviors. To enhance the accuracy of LCS, a robust LCS finding algorithm is developed incorporating hierarchical grid refinement, one-dimensional search and variational theory verification. In this way, the intricate dynamical transport boundaries are detected efficiently. These boundaries indicate that a total of 15 types of trajectories exist near asynchronous binary asteroids. According to their Kepler energy variations, these trajectories can be grouped into four basic categories, i.e., transitory, escape, impact and flyby trajectories. Furthermore, the influence of the ellipsoid's spin period on the dynamical behavior is discussed in the context of the change of dynamical regions. We found that the transitory and impact motions occur easily in the synchronous-like binary systems, in which the rotation period of the ellipsoid is nearly equal to that of the mutual orbit. Meanwhile, the results confirm a positive correlation between the spinning rate of the ellipsoid and the probability of the escape and flyby trajectories. The LCS also reveal a marked increase in trajectory diversity after a larger initial energy is selected.

  15. Asynchronous and synchronous distance learning in stem education, using the example of the online master program wind energy systems

    Science.gov (United States)

    Gleim, Daniela; Kuhl, Detlef

    2017-07-01

    This paper describes the 100% online teaching concepts of the degree program Online M.Sc. Wind Energy Systems. These are the synchronous teaching concept, the asynchronous learning concept and a combination of synchronous and asynchronous learning concept. The challenges that students and teachers have to face in the implementation of these teaching concepts are described here.

  16. Pipelined Asynchronous Cache Design

    OpenAIRE

    Nyströem, Mika

    1997-01-01

    This thesis describes the development of pipelined asynchronous cache memories. The work is done in the context of the performance characteristics of memories and transistor logic of a late 1990's high-performance asynchronous microprocessor. We describe the general framework of asynchronous memory systems, caching, and those system characteristics that make caching of growing importance and keep it an interesting research topic. Finally, we present the main contribution of this work, whi...

  17. FPGA Implementation of Block Parallel DF-MPIC Detectors for DS-CDMA Systems in Frequency-Nonselective Channels

    Directory of Open Access Journals (Sweden)

    Adel Omar Dahmane

    2008-01-01

    Full Text Available Multistage parallel interference cancellation- (MPIC- based detectors allow to mitigate multiple-access interference in direct-sequence code-division multiple-access (DS-CDMA systems. They are considered serious candidates for practical implementation showing a good tradeoff between performance and complexity. Better performance is obtained when decision feedback (DF is employed. Although MPIC and DF-MPIC have the same arithmetic complexity, DF-MPIC needs much more FPGA resources when compared to MPIC without decision feedback. In this letter, FPGA implementation of block parallel DF-MPIC (BP-DF-MPIC is proposed allowing better tradeoff between performance and FPGA area occupancy. To reach an uncoded bit-error rate of 10−3, BP-DF-MPIC shows a 1.5 dB improvement over the MPIC without decision feedback with only 8% increase in FPGA resources compared to 69% for DF-MPIC.

  18. Analysis of a Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Multipath Rician Fading Channels

    OpenAIRE

    Kim Yong-Seok; Whang Keum-Chan

    2005-01-01

    We present the BER analysis of antenna array (AA) receiver in reverse-link asynchronous multipath Rician channels and analyze the performance of an improved AA system which applies a reverse-link synchronous transmission technique (RLSTT) in order to effectively make a better estimation of covariance matrices at a beamformer-RAKE receiver. In this work, we provide a comprehensive analysis of user capacity which reflects several important factors such as the ratio of the specular component pow...

  19. Performance analysis of CDMA-based wireless communication ...

    African Journals Online (AJOL)

    As a result, current world-wide research on CDMA-based systems is geared towards high speed, highly mobile multimedia communication applications. In this paper, the performance of a multi-user DS-CDMA communication system operating in a Rayleigh fading environment is investigated. Performance expressions are ...

  20. Performance analysis of CDMA-based wireless communication

    African Journals Online (AJOL)

    ABSTRACT. The limitations initially prevalent in CDMA-based systems have been gradually solved thereby making CDMA a very promising access mode for future communication systems. Following the move towards higher data transmission rates, however, a number of other problems have emerged that need to be ...

  1. Downlink Space-Frequency Preequalization Techniques for TDD MC-CDMA Mobile Radio Systems

    Directory of Open Access Journals (Sweden)

    Silva Adão

    2004-01-01

    Full Text Available The paper considers downlink space-frequency preequalizations techniques for time division duplex (TDD MC-CDMA. We consider the use of antenna arrays at the base station (BS and analytically derive different preequalization schemes for two different receiver configurations at the mobile terminal: a simple despread receiver without channel equalization and an equal-gain combiner (EGC conventional receiver. We show that the space-frequency preequalization approach proposed allows to format the transmitted signals so that the multiple access interference at mobile terminals is reduced allowing to transfer the most computational complexity from mobile terminal to the BS. Simulation results are carried out to demonstrate the effectiveness of the proposed preequalization schemes.

  2. New high performance SAW convolvers used in high bit rate and wideband spread spectrum CDMA communications system.

    Science.gov (United States)

    Hikita, M; Takubo, C; Asai, K

    2000-01-01

    New surface acoustic wave (SAW) convolver structures with high conversion efficiency and self-temperature compensation characteristics have been developed. Strong piezoelectric substrates, regardless of temperature coefficients of delay (TCD), can be used in these convolvers. New demodulation techniques using the developed SAW convolver for high bit rate and wideband spread spectrum code division multiple access (CDMA) communications have also been developed. I- and Q-channel demodulation data can be derived directly from binary phase shift keying (BPSK) or quadri-phase shift keying (QPSK) CDMA signals. In an experiment using a 128 degrees YX-LiNbO(3) substrate, CDMA signals of 9 Mbps (megabits per second) with 60 Mcps (megachips per second) spread by 13-chip Barker code and 11 Mbps with 140 Mcps spread by 25-chip Shiba's code were clearly demodulated, demonstrating the effectiveness of these techniques for use in future CDMA communications.

  3. Model Based Prediction of Uplink Multi-Path Fading Channel Response for Pre-Equalization in Mobile MC-CDMA Systems

    Science.gov (United States)

    Mkrtchyan, Gagik; Naito, Katsuhiro; Mori, Kazuo; Kobayashi, Hideo

    Multi-carrier code division multiple access (MC-CDMA) has been considered as one of the promising techniques for the next generation of mobile communication systems because of its efficient bandwidth usage, robustness to the multi-path fading and simple channel-sharing scheme. However, MC-CDMA cannot be employed in the uplink communication where the transmitted signal from each user propagates through the different multi-path fading channel, and the received signals are no longer orthogonal at the base station. As a result, bit error rate (BER) performance in the uplink MC-CDMA communication would be strongly degraded due to the occurrence of multi-user interference (MUI). To solve the MUI problem in the uplink MC-CDMA, the pre-equalization method was proposed in which the uplink signal is pre-equalized at the user terminal by using the channel response estimated from the downlink. Although the pre-equalization method is very effective for the stationary uplink channel with fixed users, it is hard to be employed in the time varying fading channel with mobile users, because there is a big difference in the channel responses between downlink and uplink. For the efficient MUI compensation, each user terminal would be required to predict the future channel conditions based on the current observation. This paper proposes a method for model based uplink channel response prediction by employing the spectral decomposition of the downlink channel impulse response. Computer simulation results show that the proposed method can achieve the accurate prediction of channel response for mobile users during the uplink transmission and allows the effective MUI compensation.

  4. Quorum system and random based asynchronous rendezvous protocol for cognitive radio ad hoc networks

    Directory of Open Access Journals (Sweden)

    Sylwia Romaszko

    2013-12-01

    Full Text Available This paper proposes a rendezvous protocol for cognitive radio ad hoc networks, RAC2E-gQS, which utilizes (1 the asynchronous and randomness properties of the RAC2E protocol, and (2 channel mapping protocol, based on a grid Quorum System (gQS, and taking into account channel heterogeneity and asymmetric channel views. We show that the combination of the RAC2E protocol with the grid-quorum based channel mapping can yield a powerful RAC2E-gQS rendezvous protocol for asynchronous operation in a distributed environment assuring a rapid rendezvous between the cognitive radio nodes having available both symmetric and asymmetric channel views. We also propose an enhancement of the protocol, which uses a torus QS for a slot allocation, dealing with the worst case scenario, a large number of channels with opposite ranking lists.

  5. Learning Management System Development with Application of Asynchronous Learning Method in STMIK IBBI Medan

    Directory of Open Access Journals (Sweden)

    Marwa Halim

    2015-10-01

    Full Text Available This article will explain asynchronous learn- ing system using attractive discussion forums and video teaching materials features for user so that the devel- opment of both features will increase e-learning system usage by students and lecturers which can eventually im- prove the students’ absorption on the provided teaching materials, increase the active participation of students, improve self-learning ability, and to improve the quality of learning materials. The method used in this study by distributing questionnaires in online form to stakeholders users consisting of lecturers and students with the num- ber of respondents is 225 people and author use model ADDIE which focuses on Analysis, Design, Development, Implementation and Evaluation as development design. Results of this study is an application of web-based asynchronous learning which can be used by students and lecturers with the results of the application evaluation is based on a survey to students and lecturers. From this study, can be concluded that to support online learning with asynchronous method using the video learning feature in online lecture needs to be developed in order to support the science transformation process from lecturers to students. Attractive video teaching  materials  model for students has characteristics such as screen shots and presentation models.

  6. Synthesis of Asynchronous Systems from Data Flow Specifications

    Science.gov (United States)

    1993-12-01

    is a mix-mode simulator, and it is a registered trademarks of Cadence Design Systems, Inc. DRACULA is an IC layout verification system, and it is a...Experimental results of the multiplier design. with wiring capacitances derived from a parasitic extraction tool, DRACULA (R), and it is labeled "Csim". The

  7. Dynamic analysis methods for detecting anomalies in asynchronously interacting systems

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Akshat; Solis, John Hector; Matschke, Benjamin

    2014-01-01

    Detecting modifications to digital system designs, whether malicious or benign, is problematic due to the complexity of the systems being analyzed. Moreover, static analysis techniques and tools can only be used during the initial design and implementation phases to verify safety and liveness properties. It is computationally intractable to guarantee that any previously verified properties still hold after a system, or even a single component, has been produced by a third-party manufacturer. In this paper we explore new approaches for creating a robust system design by investigating highly-structured computational models that simplify verification and analysis. Our approach avoids the need to fully reconstruct the implemented system by incorporating a small verification component that dynamically detects for deviations from the design specification at run-time. The first approach encodes information extracted from the original system design algebraically into a verification component. During run-time this component randomly queries the implementation for trace information and verifies that no design-level properties have been violated. If any deviation is detected then a pre-specified fail-safe or notification behavior is triggered. Our second approach utilizes a partitioning methodology to view liveness and safety properties as a distributed decision task and the implementation as a proposed protocol that solves this task. Thus the problem of verifying safety and liveness properties is translated to that of verifying that the implementation solves the associated decision task. We develop upon results from distributed systems and algebraic topology to construct a learning mechanism for verifying safety and liveness properties from samples of run-time executions.

  8. A CDMA synchronisation scheme

    Science.gov (United States)

    Soprano, C.

    1993-01-01

    CDMA (Code Division Multiple Access) is known to decrease inter-service interference in Satellite Communication Systems. Its performance is increased by chip quasi-synchronous operation which virtually eliminates the self-noise; however, the theory shows that the time error on the synchronization has to be kept at less than one tenth of a chip which, for 1 Mchip/sec. spreading rate, corresponds to 10(exp -7) sec. This, on the return-link, may only be achieved by means of a closed loop control system which, for mobile communication systems, has to be capable of autonomous operation. Until now some results have been reported on the feasibility of chip quasi-synchronous operation for mobile communication systems only including satellites on GEO (Geostationary Earth Orbit). In what follows, the basic principles are exposed, and results are presented showing how low chip synchronism error may be achieved by means of an autonomous control loop operating through satellites on any Earth orbit.

  9. Reverse Link Outage Probabilities of Multicarrier CDMA Systems with Beamforming in the Presence of Carrier Frequency Offset

    Directory of Open Access Journals (Sweden)

    Xiaoyu Hu

    2007-11-01

    Full Text Available The outage probability of reverse link multicarrier (MC code-division multiple access (CDMA systems with beamforming in the presence of carrier frequency offset (CFO is studied. A conventional uniform linear array (ULA beamformer is utilized. An independent Nakagami fading channel is assumed for each subcarrier of all users. The outage probability is first investigated under a scenario where perfect beamforming is assumed. A closed form expression of the outage probability is derived. The impact of different types of beamforming impairments on the outage probability is then evaluated, including direction-of-arrival (DOA estimation errors, angle spreads, and mutual couplings. Numerical results show that the outage probability improves significantly as the number of antenna elements increases. The effect of CFO on the outage probability is reduced significantly when the beamforming technique is employed. Also, it is seen that small beamforming impairments (DOA estimation errors and angle spreads only affect the outage probability very slightly, and the mutual coupling between adjacent antenna elements does not affect the outage probability noticeably.

  10. Reverse Link Outage Probabilities of Multicarrier CDMA Systems with Beamforming in the Presence of Carrier Frequency Offset

    Directory of Open Access Journals (Sweden)

    Hu Xiaoyu

    2008-01-01

    Full Text Available The outage probability of reverse link multicarrier (MC code-division multiple access (CDMA systems with beamforming in the presence of carrier frequency offset (CFO is studied. A conventional uniform linear array (ULA beamformer is utilized. An independent Nakagami fading channel is assumed for each subcarrier of all users. The outage probability is first investigated under a scenario where perfect beamforming is assumed. A closed form expression of the outage probability is derived. The impact of different types of beamforming impairments on the outage probability is then evaluated, including direction-of-arrival (DOA estimation errors, angle spreads, and mutual couplings. Numerical results show that the outage probability improves significantly as the number of antenna elements increases. The effect of CFO on the outage probability is reduced significantly when the beamforming technique is employed. Also, it is seen that small beamforming impairments (DOA estimation errors and angle spreads only affect the outage probability very slightly, and the mutual coupling between adjacent antenna elements does not affect the outage probability noticeably.

  11. Multigroup Synchronization in 1D-Bernoulli Chaotic Collaborative CDMA

    Directory of Open Access Journals (Sweden)

    Sumith Babu Suresh Babu

    2017-01-01

    Full Text Available Code-division multiple access (CDMA has played a remarkable role in the field of wireless communication systems, and its capacity and security requirements are still being addressed. Collaborative multiuser transmission and detection are a contemporary technique used in CDMA systems. The performance of these systems is governed by the proper accommodation of the users and by proper synchronization schemes. The major research concerns in the existing multiuser overloaded CDMA schemes are (i statistically uncorrelated PN sequences that cause multiple-access interference (MAI and (ii the security of the user’s data. In this paper, a novel grouped CDMA scheme, the 1D-Bernoulli chaotic collaborative CDMA (BCC-CDMA, is introduced, in which mutually orthogonal chaotic sequences spread the users’ data within a group. The synchronization of multiple groups in this scheme has been analyzed under MAI limited environments and the results are presented. This increases the user capacity and also provides sufficient security as a result of the correlation properties possessed by the chaotic codes. Multigroup synchronization is achieved using a 1D chaotic pilot sequence generated by the Bernoulli Map. The mathematical model of the proposed system is described and compared with the theoretical model of the synchronization in CDMA, the simulation results of which are presented.

  12. The Pacific Asynchronous TeleHealth (PATH) system: review of 1,000 pediatric teleconsultations.

    Science.gov (United States)

    Mahnke, Christopher Becket; Jordan, Christopher P; Bergvall, Ethan; Person, Donald A; Pinsker, Jordan E

    2011-01-01

    The aim of this study was to evaluate the impact on pediatric care of the Pacific Asynchronous TeleHealth (PATH) system, a provider-to-provider teleconsultation platform utilized by military medical facilities throughout the Pacific Region. This review focuses on access to care, quality of care, and cost savings for the Department of Defense as a result of ongoing development of the PATH system from 2006 to 2009. This is a retrospective review of 1,000 consecutive teleconsultations occurring from January 2006 to March 2009. Three pediatric subspecialists reviewed the characteristics of each teleconsultation and the ultimate outcome. The PATH system processed > 300 pediatric teleconsultations in 2009 from 20 hospitals and clinics throughout the Pacific Region. The number of teleconsultations has grown significantly since 2006. Median teleconsultation response time was 14.5 h with 97% of teleconsultations answered within 1 week. The majority (75%) of teleconsultations came from areas without host nation pediatric subspecialty resources. Most teleconsultations (72%) involved diagnostic questions, whereas 21% were primarily for treatment issues. Teleconsultations originated predominantly from outpatient clinics (90%), with question resolution in 60% of cases without a face-to-face subspecialty evaluation. Fifteen percent of teleconsultations resulted in patient transfer to our center for definitive diagnosis and treatment. The diagnostic and/or treatment plan was modified in 74% of teleconsultations. PATH precluded patient transfer in 12%-43% of teleconsultations (annual savings: $208,283-$746,348 per year) and generated an average of 1.7 relative value units per teleconsultation. PATH provided patient access to pediatric subspecialty expertise via provider-to-provider asynchronous teleconsultation. Internet-based pediatric subspecialty teleconsultation provides fast, convenient, cost-effective, quality pediatric care to populations of patients who might otherwise

  13. Characterizing CDMA downlink feasibility via effective interference

    NARCIS (Netherlands)

    Endrayanto, A.I.; van den Berg, Hans Leo; Boucherie, Richardus J.

    2003-01-01

    This paper models and analyses downlink power assignment feasibility in Code Division Multiple Access (CDMA) mobile networks. By discretizing the area into small segments, the power requirements are characterized via a matrix representation that separates user and system characteristics. We obtain a

  14. Data-Aware Retrodiction for Asynchronous Harmonic Measurement in a Cyber-Physical Energy System

    Directory of Open Access Journals (Sweden)

    Youda Liu

    2016-08-01

    Full Text Available Cyber-physical energy systems provide a networked solution for safety, reliability and efficiency problems in smart grids. On the demand side, the secure and trustworthy energy supply requires real-time supervising and online power quality assessing. Harmonics measurement is necessary in power quality evaluation. However, under the large-scale distributed metering architecture, harmonic measurement faces the out-of-sequence measurement (OOSM problem, which is the result of latencies in sensing or the communication process and brings deviations in data fusion. This paper depicts a distributed measurement network for large-scale asynchronous harmonic analysis and exploits a nonlinear autoregressive model with exogenous inputs (NARX network to reorder the out-of-sequence measuring data. The NARX network gets the characteristics of the electrical harmonics from practical data rather than the kinematic equations. Thus, the data-aware network approximates the behavior of the practical electrical parameter with real-time data and improves the retrodiction accuracy. Theoretical analysis demonstrates that the data-aware method maintains a reasonable consumption of computing resources. Experiments on a practical testbed of a cyber-physical system are implemented, and harmonic measurement and analysis accuracy are adopted to evaluate the measuring mechanism under a distributed metering network. Results demonstrate an improvement of the harmonics analysis precision and validate the asynchronous measuring method in cyber-physical energy systems.

  15. Modeling and Analysis of Cellular CDMA Forward Channel

    National Research Council Canada - National Science Library

    Tighe, Jan

    2001-01-01

    In this thesis, we develop the forward channel model for a DS-CDMA cellular system operating in a slow-flat Rayleigh fading and log normal shadowing environment, which incorporates the extended Hata...

  16. An asynchronous, pipelined, electronic acquisition system for Active Matrix Flat-Panel Imagers (AMFPIs)

    CERN Document Server

    Huang, W; Berry, J; Maolinbay, M; Martelli, C; Mody, P; Nassif, S; Yeakey, M

    1999-01-01

    The development of a full-custom electronic acquisition system designed for readout of large-area active matrix flat-panel imaging arrays is reported. The arrays, which comprise two-dimensional matrices of pixels utilizing amorphous silicon thin-film transistors, are themselves under development for a wide variety of X-ray imaging applications. The acquisition system was specifically designed to facilitate detailed, quantitative investigations of the properties of these novel imaging arrays and contains significant enhancements compared to a previously developed acquisition system. These enhancements include pipelined preamplifier circuits to allow faster readout speed, expanded addressing capabilities allowing a maximum of 4096 array data lines, and on-board summing of image frames. The values of many acquisition system parameters, including timings and voltages, may be specified and downloaded from a host computer. Once acquisition is enabled, the system operates asynchronously of its host computer. The sys...

  17. A multi-host front end concentrator system for asynchronous consoles

    CERN Document Server

    Palandri, E M

    1974-01-01

    Describes a front end concentrator system for asynchronous time sharing consoles which has recently been put into operation at CERN. The concentrator will control up to 36 consoles at speeds up to 9600 bits per second and has the capability of dynamically connecting these consoles to several large Host processors. Features of the system include specially designed hardware and software to connect a wide range of different types of consoles in a flexible and expandable way, and the use of special purpose microcode to optimise console handling and facilitate the implementation of the system. The system runs in an HP2100 computer initially front-ending CDC 6000 series computers using the INTERCOM time sharing system. (6 refs).

  18. Analysis of a Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Multipath Rician Fading Channels

    Directory of Open Access Journals (Sweden)

    Kim Yong-Seok

    2005-01-01

    Full Text Available We present the BER analysis of antenna array (AA receiver in reverse-link asynchronous multipath Rician channels and analyze the performance of an improved AA system which applies a reverse-link synchronous transmission technique (RLSTT in order to effectively make a better estimation of covariance matrices at a beamformer-RAKE receiver. In this work, we provide a comprehensive analysis of user capacity which reflects several important factors such as the ratio of the specular component power to the Rayleigh fading power, the shape of multipath intensity profile, and the number of antennas. Theoretical analysis demonstrates that for the case of a strong specular path's power or for a high decay factor, the employment of RLSTT along with AA has the potential of improving the achievable capacity by an order of magnitude.

  19. An implantable closedloop asynchronous drug delivery system for the treatment of refractory epilepsy.

    Science.gov (United States)

    Salam, Muhammad Tariqus; Mirzaei, Marjan; Ly, My Sandra; Nguyen, Dang Khoa; Sawan, Mohamad

    2012-07-01

    In this paper, we present an implantable device for intra-cerebral electroencephalography (icEEG) data acquisition and real-time epileptic seizure detection with simultaneous focal antiepileptic drug injection feedback. This implantable device includes a neural signal amplifier, an asynchronous seizure detector, a drug delivery system (DDS) including a micropump, and a hybrid subdural electrode (HSE). The asynchronous detection algorithm is based on data-dependent analysis and validated with Matlab tools. The detector and DDS have a power saving mode. The HSE contacts are made of Platinum (Pt) encapsulated with polydimethylsiloxane (PDMS). Given the heterogeneity of electrographic seizure signals and seizure suppression threshold, the implantable device provides tunable parameters facility through an external transmitter to adapt to each individual's neurophysiology prior to clinical deployment. The proposed detector and DDS were assembled in Ø 50 mm and Ø 30 mm circular printed circuit boards, respectively. The detector was validated using icEEG recordings of seven patients who had previously undergone an intracranial investigation for epilepsy surgery. The triggering of the DDS was tested and a predefined seizure suppression dose was delivered ~16 s after electrographical seizure onsets. The device's power consumption was reduced by 12% in active mode and 49% in power saving mode compared to similar seizure detection algorithms implemented with synchronous architecture.

  20. All-optical code routing in interconnected optical CDMA and WDM ring networks.

    Science.gov (United States)

    Deng, Yanhua; Fok, Mable P; Prucnal, Paul R; Wang, Ting

    2010-11-01

    We propose an all-optical hybrid network composed of optical code division multiple access (CDMA) rings interconnecting through a reconfigurable wavelength division multiplexing (WDM) metro area ring. This network retains the advantages of both the optical CDMA and WDM techniques, including asynchronous access and differentiated quality of service, while removing the hard limit on the number of subscribers and increasing network flexibility. The all-optical network is enabled by using nonlinear optical loop mirrors in an add/drop router (ADR) that performs code conversion, dropping, and switching asynchronously. We experimentally demonstrate the functionalities of the ADR in the proposed scheme asynchronously and obtain error-free performance. The bit-error rate measurements show acceptable power penalties for different code routes.

  1. Wind-powered asynchronous AC/DC/AC converter system. [for electric power supply regulation

    Science.gov (United States)

    Reitan, D. K.

    1973-01-01

    Two asynchronous ac/dc/ac systems are modelled that utilize wind power to drive a variable or constant hertz alternator. The first system employs a high power 60-hertz inverter tie to the large backup supply of the power company to either supplement them from wind energy, storage, or from a combination of both at a preset desired current; rectifier and inverter are identical and operate in either mode depending on the silicon control rectifier firing angle. The second system employs the same rectification but from a 60-hertz alternator arrangement; it provides mainly dc output, some sinusoidal 60-hertz from the wind bus and some high harmonic content 60-hertz from an 800-watt inverter.

  2. Rayleigh fading effect reduction with wideband DS/CDMA signals

    Science.gov (United States)

    Holtzman, Jack M.; Jalloul, Louay M. A.

    1994-02-01

    Mobile radio fading analyses typically assume a single frequency carrier transmitted through the propagation medium. The results are then used for the case of narrowband transmission. New phenomena occur with wideband transmission. This paper presents an analysis of the mitigation of the Rayleigh fading effect for wideband direct sequence code division multiple access (DS/CDMA) signaling. There are measurements that show this phenomenon. The reduction of the Rayleigh fading effect is an advantage of CDMA over narrowband transmission systems and it eases the burden of CDMA power control. A general expression for the coefficient of variation of the received wideband signal power is derived. It is shown how the coefficient of variation of the received power decreases as the bandwidth spreading increases. This paper also analyzes the time correlation needed for other analyses (e.g., CDMA power control).

  3. Analysis Of Functional Stability Of The Triphased Asynchronous Generator Used In Conversion Systems Of A Eolian Energy Into Electric Energy

    Directory of Open Access Journals (Sweden)

    Ion VONCILA

    2003-12-01

    Full Text Available This paper presents a study of the influence of the main perturbation agent over the functional stability of the triphased asynchronous generator (for the two alternative: with coiled and short circuit rotor, used for the conversion systems from a eolian energy into electric energy.

  4. A Link-Level Simulator of the cdma2000 Reverse-Link Physical Layer

    OpenAIRE

    Gharavi, H; Chin, F.; Ban, K.; Wyatt-Millington, R.

    2003-01-01

    The cdma2000 system is an evolutionary enhancement of the IS-95 standards which support 3G services defined by the International Telecommunications Union (ITU). cdma2000 comes in two phases: 1XRTT and 3XRTT (1X and 3X indicates the number of 1.25 MHz wide radio carrier channels used and RTT stands for Radio Transmission Technology). The cdma2000 1XRTT, which operates within a 1.25 MHz bandwidth, can be utilized in existing IS-95 CDMA channels as it uses the same bandwidth, while 3XRTT require...

  5. Successive Interference Cancellation for DS-Optical PPM-CDMA Systems

    Science.gov (United States)

    Alsowaidi, N.; Eltaif, Tawfig; Mokhtar, M. R.

    2016-06-01

    In this paper we introduce a successive interference cancellation (SIC) scheme for direct sequence optical code division multiple access (DS-OCDMA) systems using pulse position modulation (PPM). Considering double-padded modified prime code (DPMPC) as a signature sequence code, results show that the system has better performance in terms of both capacity and bit error rate (BER) as compared to the one without cancellation scheme, where the system with SIC scheme can support up to 88 users while the system without SIC scheme can support only 38 users at similar BER=10-9. Although the receiver sensitivity is affected by the overlapping between users, which limits the system performance, the theoretical analysis of this issue indicates the influence of the size of M-ary PPM on OCDMA system. Hence, the BER value is still sufficient for good system performance.

  6. Asynchronous P300 BCI

    DEFF Research Database (Denmark)

    Panicker, Rajesh; Puthusserypady, Sadasivan; Sun, Ying

    2010-01-01

    An asynchronous hybrid brain-computer interface (BCI) system combining the P300 and steady-state visually evoked potentials (SSVEP) paradigms is introduced. A P300 base system is used for information transfer, and is augmented to include SSVEP for control state detection. The proposed system has...

  7. Model checking methodology for large systems, faults and asynchronous behaviour. SARANA 2011 work report

    Energy Technology Data Exchange (ETDEWEB)

    Lahtinen, J. [VTT Technical Research Centre of Finland, Espoo (Finland); Launiainen, T.; Heljanko, K.; Ropponen, J. [Aalto Univ., Espoo (Finland). Dept. of Information and Computer Science

    2012-07-01

    Digital instrumentation and control (I and C) systems are challenging to verify. They enable complicated control functions, and the state spaces of the models easily become too large for comprehensive verification through traditional methods. Model checking is a formal method that can be used for system verification. A number of efficient model checking systems are available that provide analysis tools to determine automatically whether a given state machine model satisfies the desired safety properties. This report reviews the work performed in the Safety Evaluation and Reliability Analysis of Nuclear Automation (SARANA) project in 2011 regarding model checking. We have developed new, more exact modelling methods that are able to capture the behaviour of a system more realistically. In particular, we have developed more detailed fault models depicting the hardware configuration of a system, and methodology to model function-block-based systems asynchronously. In order to improve the usability of our model checking methods, we have developed an algorithm for model checking large modular systems. The algorithm can be used to verify properties of a model that could otherwise not be verified in a straightforward manner. (orig.)

  8. Multichannel Baseband Processor for Wideband CDMA

    OpenAIRE

    Jalloul Louay MA; Lin Jim

    2005-01-01

    The system architecture of the cellular base station modem engine (CBME) is described. The CBME is a single-chip multichannel transceiver capable of processing and demodulating signals from multiple users simultaneously. It is optimized to process different classes of code-division multiple-access (CDMA) signals. The paper will show that through key functional system partitioning, tightly coupled small digital signal processing cores, and time-sliced reuse architecture, CBME is able to achie...

  9. A Low-Complexity Joint Synchronization and Detection Algorithm for Single-Band DS-CDMA UWB Communications

    DEFF Research Database (Denmark)

    Christensen, Lars P.B.

    2005-01-01

    The problem of asynchronous direct-sequence code division multiple access (DS-CDMA) detection over the ultra-wideband (UWB) multipath channel is considered. A joint synchronization, channel-estimation and multi-user detection scheme based on the adaptive linear minimum mean-square error (LMMSE...

  10. Performance Analysis of SAC Optical PPM-CDMA System-Based Interference Rejection Technique

    Science.gov (United States)

    Alsowaidi, N.; Eltaif, Tawfig; Mokhtar, M. R.

    2016-03-01

    In this paper, we aim to theoretically analyse optical code division multiple access (OCDMA) system that based on successive interference cancellation (SIC) using pulse position modulation (PPM), considering the interference between the users, imperfection cancellation occurred during the cancellation process and receiver noises. Spectral amplitude coding (SAC) scheme is used to suppress the overlapping between the users and reduce the receiver noises effect. The theoretical analysis of the multiple access interference (MAI)-limited performance of this approach indicates the influence of the size of M-ary PPM on OCDMA system. The OCDMA system performance improves with increasing M-ary PPM. Therefore, it was found that the SIC/SAC-OCDMA system using PPM technique along with modified prime (MPR) codes used as signature sequence code offers significant improvement over the one without cancellation and it can support up to 103 users at the benchmarking value of bit error rate (BER) = 10-9 with prime number p = 11 while the system without cancellation scheme can support only up to 52 users.

  11. Noncoherent Spectral Optical CDMA System Using 1D Active Weight Two-Code Keying Codes

    Directory of Open Access Journals (Sweden)

    Bih-Chyun Yeh

    2016-01-01

    Full Text Available We propose a new family of one-dimensional (1D active weight two-code keying (TCK in spectral amplitude coding (SAC optical code division multiple access (OCDMA networks. We use encoding and decoding transfer functions to operate the 1D active weight TCK. The proposed structure includes an optical line terminal (OLT and optical network units (ONUs to produce the encoding and decoding codes of the proposed OLT and ONUs, respectively. The proposed ONU uses the modified cross-correlation to remove interferences from other simultaneous users, that is, the multiuser interference (MUI. When the phase-induced intensity noise (PIIN is the most important noise, the modified cross-correlation suppresses the PIIN. In the numerical results, we find that the bit error rate (BER for the proposed system using the 1D active weight TCK codes outperforms that for two other systems using the 1D M-Seq codes and 1D balanced incomplete block design (BIBD codes. The effective source power for the proposed system can achieve −10 dBm, which has less power than that for the other systems.

  12. Sustainable project of microgeneration systems based on asynchronous generator; Projeto sustentavel de sistemas de microgeracao baseados em gerador assincrono

    Energy Technology Data Exchange (ETDEWEB)

    Salazar Herrera, Victoria Alejandra; Romero, Jesus Franklin Andrade [Universidade Federal do ABC (CECS/UFABC), Santo Andre, SP (Brazil). Centro de Engenharia, Modelagem e Ciencias Sociais Aplicadas. Programa de Pos-Graduacao em Energia], emails: victoria.herrera@ufabc.edu.br, jesus.romero@ufabc.edu.br

    2010-07-01

    Recently, the interest in decentralized generation systems has increased considering a multidisciplinary and sustainable approach. In this sense, this work proposes the evaluation of isolated microgeneration systems, focusing the life cycle of the asynchronous generator, considering the technological, economic and environmental dimensions. By means of the generator efficiency, the unbalanced voltage percentage and the emissions factor, the work point out the relevance of health diagnosis of isolated microgeneration systems objectifying minimize the impacts caused by faulty operation of the generator. (author)

  13. PERFORMANCE ANALYSIS OF OPTICAL CDMA SYSTEM USING VC CODE FAMILY UNDER VARIOUS OPTICAL PARAMETERS

    Directory of Open Access Journals (Sweden)

    HASSAN YOUSIF AHMED

    2012-06-01

    Full Text Available The intent of this paper is to study the performance of spectral-amplitude coding optical code-division multiple-access (OCDMA systems using Vector Combinatorial (VC code under various optical parameters. This code can be constructed by an algebraic way based on Euclidian vectors for any positive integer number. One of the important properties of this code is that the maximum cross-correlation is always one which means that multi-user interference (MUI and phase induced intensity noise are reduced. Transmitter and receiver structures based on unchirped fiber Bragg grating (FBGs using VC code and taking into account effects of the intensity, shot and thermal noise sources is demonstrated. The impact of the fiber distance effects on bit error rate (BER is reported using a commercial optical systems simulator, virtual photonic instrument, VPITM. The VC code is compared mathematically with reported codes which use similar techniques. We analyzed and characterized the fiber link, received power, BER and channel spacing. The performance and optimization of VC code in SAC-OCDMA system is reported. By comparing the theoretical and simulation results taken from VPITM, we have demonstrated that, for a high number of users, even if data rate is higher, the effective power source is adequate when the VC is used. Also it is found that as the channel spacing width goes from very narrow to wider, the BER decreases, best performance occurs at a spacing bandwidth between 0.8 and 1 nm. We have shown that the SAC system utilizing VC code significantly improves the performance compared with the reported codes.

  14. A discussion on mobile satellite system and the myths of CDMA and diversity revealed

    Science.gov (United States)

    Hart, Nicholas; Goerke, Thomas; Jahn, Axel

    1995-01-01

    The paper explores the myths and facts surrounding: link margins and constellation designs; the use of satellite diversity in a mobile satellite channel; trade-offs in multiple access technique. Different satellite constellations are presented, which are comparable with those used by the big LEO proponents, with the associated trade-offs in the system design. Propagation data and results from various narrowband and wideband measurement campaigns are used to illustrate the expected differences in service performance.

  15. A new blind nulling algorithm for CDMA mobile satellite communication systems

    Science.gov (United States)

    Liu, Yunzhi; Wang, Huali; Wang, Zhihui

    2007-11-01

    A new anti-jamming method is proposed combining adaptive array with direct sequence spread spectrum (DSSS) techniques in mobile satellite communication system. Different with the conventional depreading process, the proposed method modifies DSSS despreador, in which the output data are blindly processed. It overcomes the problem that DSSS signal often has very lower SNR, which is difficult to be captured in constant modulus array processing, especially when strong interference/jamming signals exist coincidentally.

  16. Multichannel Baseband Processor for Wideband CDMA

    Directory of Open Access Journals (Sweden)

    Jalloul Louay MA

    2005-01-01

    Full Text Available The system architecture of the cellular base station modem engine (CBME is described. The CBME is a single-chip multichannel transceiver capable of processing and demodulating signals from multiple users simultaneously. It is optimized to process different classes of code-division multiple-access (CDMA signals. The paper will show that through key functional system partitioning, tightly coupled small digital signal processing cores, and time-sliced reuse architecture, CBME is able to achieve a high degree of algorithmic flexibility while maintaining efficiency. The paper will also highlight the implementation and verification aspects of the CBME chip design. In this paper, wideband CDMA is used as an example to demonstrate the architecture concept.

  17. Multichannel Baseband Processor for Wideband CDMA

    Science.gov (United States)

    Jalloul, Louay M. A.; Lin, Jim

    2005-12-01

    The system architecture of the cellular base station modem engine (CBME) is described. The CBME is a single-chip multichannel transceiver capable of processing and demodulating signals from multiple users simultaneously. It is optimized to process different classes of code-division multiple-access (CDMA) signals. The paper will show that through key functional system partitioning, tightly coupled small digital signal processing cores, and time-sliced reuse architecture, CBME is able to achieve a high degree of algorithmic flexibility while maintaining efficiency. The paper will also highlight the implementation and verification aspects of the CBME chip design. In this paper, wideband CDMA is used as an example to demonstrate the architecture concept.

  18. A Geometrical-Based Model for Cochannel Interference Analysis and Capacity Estimation of CDMA Cellular Systems

    Directory of Open Access Journals (Sweden)

    Konstantinos B. Baltzis

    2008-10-01

    Full Text Available A common assumption in cellular communications is the circular-cell approximation. In this paper, an alternative analysis based on the hexagonal shape of the cells is presented. A geometrical-based stochastic model is proposed to describe the angle of arrival of the interfering signals in the reverse link of a cellular system. Explicit closed form expressions are derived, and simulations performed exhibit the characteristics and validate the accuracy of the proposed model. Applications in the capacity estimation of WCDMA cellular networks are presented. Dependence of system capacity of the sectorization of the cells and the base station antenna radiation pattern is explored. Comparisons with data in literature validate the accuracy of the proposed model. The degree of error of the hexagonal and the circular-cell approaches has been investigated indicating the validity of the proposed model. Results have also shown that, in many cases, the two approaches give similar results when the radius of the circle equals to the hexagon inradius. A brief discussion on how the proposed technique may be applied to broadband access networks is finally made.

  19. A Geometrical-Based Model for Cochannel Interference Analysis and Capacity Estimation of CDMA Cellular Systems

    Directory of Open Access Journals (Sweden)

    Baltzis KonstantinosB

    2008-01-01

    Full Text Available Abstract A common assumption in cellular communications is the circular-cell approximation. In this paper, an alternative analysis based on the hexagonal shape of the cells is presented. A geometrical-based stochastic model is proposed to describe the angle of arrival of the interfering signals in the reverse link of a cellular system. Explicit closed form expressions are derived, and simulations performed exhibit the characteristics and validate the accuracy of the proposed model. Applications in the capacity estimation of WCDMA cellular networks are presented. Dependence of system capacity of the sectorization of the cells and the base station antenna radiation pattern is explored. Comparisons with data in literature validate the accuracy of the proposed model. The degree of error of the hexagonal and the circular-cell approaches has been investigated indicating the validity of the proposed model. Results have also shown that, in many cases, the two approaches give similar results when the radius of the circle equals to the hexagon inradius. A brief discussion on how the proposed technique may be applied to broadband access networks is finally made.

  20. How Equalization Techniques Affect the TCP Performance of MC-CDMA Systems in Correlated Fading Channels

    Directory of Open Access Journals (Sweden)

    Giacomo Leonardi

    2007-12-01

    Full Text Available This paper investigates the impact of several equalization techniques for multicarrier code division multiple access systems on the performance at both lower and upper layers (i.e., physical and TCP layers. Classical techniques such as maximal ratio combining, equal gain combining, orthogonality restoring combining, minimum mean square error, as well as a partial equalization (PE are investigated in time- and frequency-correlated fading channels with various numbers of interferers. Their impact on the performance at upper level is then studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user, allowing an investigation of the real gain produced by signal processing techniques at TCP level.

  1. How Equalization Techniques Affect the TCP Performance of MC-CDMA Systems in Correlated Fading Channels

    Directory of Open Access Journals (Sweden)

    Conti Andrea

    2008-01-01

    Full Text Available Abstract This paper investigates the impact of several equalization techniques for multicarrier code division multiple access systems on the performance at both lower and upper layers (i.e., physical and TCP layers. Classical techniques such as maximal ratio combining, equal gain combining, orthogonality restoring combining, minimum mean square error, as well as a partial equalization (PE are investigated in time- and frequency-correlated fading channels with various numbers of interferers. Their impact on the performance at upper level is then studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user, allowing an investigation of the real gain produced by signal processing techniques at TCP level.

  2. A Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Frequency-Selective Fading Channels with Power Control Error

    Directory of Open Access Journals (Sweden)

    Yong-Seok Kim

    2004-08-01

    Full Text Available An improved antenna array (AA has been introduced, in which reverse-link synchronous transmission technique (RLSTT is incorporated to effectively make better an estimation of covariance matrices at a beamformer-RAKE receiver. While RLSTT is effective in the first finger at the RAKE receiver in order to reject multiple-access interference (MAI, the beamformer estimates the desired user's complex weights, enhancing its signal and reducing cochannel interference (CCI from the other directions. In this work, it is attempted to provide a comprehensive analysis of user capacity which reflects several important factors such as the shape of multipath intensity profile (MIP, the number of antennas, and power control error (PCE. Theoretical analysis, confirmed by the simulations, demonstrates that the orthogonality provided by employing RLSTT along with AA may make the DS-CDMA system insensitive to the PCE even with fewer numbers of antennas.

  3. Space-time adaptive decision feedback neural receivers with data selection for high-data-rate users in DS-CDMA systems.

    Science.gov (United States)

    de Lamare, Rodrigo C; Sampaio-Neto, Raimundo

    2008-11-01

    A space-time adaptive decision feedback (DF) receiver using recurrent neural networks (RNNs) is proposed for joint equalization and interference suppression in direct-sequence code-division multiple-access (DS-CDMA) systems equipped with antenna arrays. The proposed receiver structure employs dynamically driven RNNs in the feedforward section for equalization and multiaccess interference (MAI) suppression and a finite impulse response (FIR) linear filter in the feedback section for performing interference cancellation. A data selective gradient algorithm, based upon the set-membership (SM) design framework, is proposed for the estimation of the coefficients of RNN structures and is applied to the estimation of the parameters of the proposed neural receiver structure. Simulation results show that the proposed techniques achieve significant performance gains over existing schemes.

  4. Experimental investigation on the high chip rate of 2D incoherent optical CDMA system

    Science.gov (United States)

    Su, Guorui; Wang, Rong; Pu, Tao; Fang, Tao; Zheng, Jilin; Zhu, Huatao; Wu, Weijiang

    2015-08-01

    An innovative approach to realise high chip rate in OCDMA transmission system is proposed and experimentally investigation, the high chip rate is achieved through a 2-D wavelength-hopping time-spreading en/decoder based on the supercontinuum light source. The source used in the experiment is generated by high nonlinear optical fiber (HNLF), Erbium-doped fiber amplifier (EDFA) which output power is 26 dBm, and distributed feed-back laser diode which works in the gain switch state. The span and the flatness of the light source are 20 nm and 3 dB, respectively, after equalization of wavelength selective switch (WSS). The wavelength-hopping time-spreading coder can be changed 20 nm in the wavelength and 400 ps in the time, is consist of WSS and delay lines. Therefore, the experimental results show that the chip rate can achieve 500 Gchip/s, in the case of 2.5 Gbit/s, while keeping a bit error rate below forward error correction limit after 40 km transmission.

  5. Asynchronized synchronous machines

    CERN Document Server

    Botvinnik, M M

    1964-01-01

    Asynchronized Synchronous Machines focuses on the theoretical research on asynchronized synchronous (AS) machines, which are "hybrids” of synchronous and induction machines that can operate with slip. Topics covered in this book include the initial equations; vector diagram of an AS machine; regulation in cases of deviation from the law of full compensation; parameters of the excitation system; and schematic diagram of an excitation regulator. The possible applications of AS machines and its calculations in certain cases are also discussed. This publication is beneficial for students and indiv

  6. New Optimal Solutions for Real-Time Reconfigurable Periodic Asynchronous Operating System Tasks with Minimizations of Response Time

    OpenAIRE

    Hamza Gharsellaoui; Mohamed Khalgui; Samir Ben Ahmed

    2012-01-01

    Scheduling tasks is an essential requirement in most real-time and embedded systems, but leads to unwanted central processing unit (CPU) overheads. The authors present a real-time schedulability algorithm for preemptable, asynchronous and periodic reconfigurable task systems with arbitrary relative deadlines, scheduled on a uniprocessor by an optimal scheduling algorithm based on the earliest deadline first (EDF) principles and on the dynamic reconfiguration. A reconfiguration scenario is ass...

  7. Can quantization improve error performance in CDMA?

    Energy Technology Data Exchange (ETDEWEB)

    Efraim, Hadar; Yacov, Nadav; Kanter, Ido [Minerva Center and Department of Physics, Bar-Ilan University, Ramat-Gan 52900 (Israel); Shental, Ori [Center for Magnetic Recording Research (CMRR), University of California, San Diego (UCSD), 9500 Gilman Drive, La Jolla, CA 92093 (United States)], E-mail: hadar.efraim@mail.biu.ac.il, E-mail: oshental@ucsd.edu, E-mail: nadav.yacov@mail.biu.ac.il, E-mail: kanter@mail.biu.ac.il

    2008-09-12

    A K-user direct-sequence spread-spectrum code-division multiple-access (CDMA) system with (q << log{sub 2}K)-bit baseband signal quantization at the demodulator is considered. It is shown that additionally quantizing the K + 1 level output signal of the CDMA modulator into q bits improves significantly the average bit-error performance in a non-negligible regime of noise variance, {sigma}{sup 2}, and user load, {beta}, under various system settings, like additive white Gaussian noise (AWGN), Rayleigh fading, single-user detection, multi-user detection, random and orthogonal spreading codes. For the case of single-user detection in random spreading AWGN-CDMA, this regime is identified explicitly as {sigma}<{gamma}(q){radical}{beta}, where {gamma}(q) is a certain pre-factor depending on q, and the associated BER improvement is derived analytically for q = 1, 2. For the other examined system settings, computer simulations are provided, corroborating this interesting behavior.

  8. CDMA2000 Y WCDMA

    Directory of Open Access Journals (Sweden)

    Jaime Sánchez García

    2005-01-01

    Full Text Available Este artículo ofrece un panorama general de los sistemas de comunicaciones móviles celulares de tercera generación (3G que han tenido una mayor aceptación (CDMA2000 y WCDMA en el mercado, y una comparación basada en los puntos principales donde los sistemas difieren que indica las ventajas y desventajas de cada uno. Los sistemas de comunicaciones móviles celulares 3G ofrecen mayores capacidades de transmisión a los de segunda generación (2G, y permiten brindar, además de los tradicionales servicios de telefonía celular, servicios de comunicación de datos a velocidades más altas que los de 2G. Las redes CDMA2000 y WCDMA forman parte del estándar IMT-2000 definido por la Unión Internacional de Telecomunicaciones (ITU para sistemas de comunicaciones inalámbricas de tercera generación; éstas son redes de banda ancha que ofrecen mayores velocidades de transmisión de datos, servicios de internet y aplicaciones multimedia

  9. Why is CDMA the solution for mobile satellite communication

    Science.gov (United States)

    Gilhousen, Klein S.; Jacobs, Irwin M.; Padovani, Roberto; Weaver, Lindsay A.

    1989-01-01

    It is demonstrated that spread spectrum Code Division Multiple Access (CDMA) systems provide an economically superior solution to satellite mobile communications by increasing the system maximum capacity with respect to single channel per carrier Frequency Division Multiple Access (FDMA) systems. Following the comparative analysis of CDMA and FDMA systems, the design of a model that was developed to test the feasibility of the approach and the performance of a spread spectrum system in a mobile environment. Results of extensive computer simulations as well as laboratory and field tests results are presented.

  10. An asynchronous writing method for restart files in the gysela code in prevision of exascale systems*

    Directory of Open Access Journals (Sweden)

    Thomine O.

    2013-12-01

    Full Text Available The present work deals with an optimization procedure developed in the full-f global GYrokinetic SEmi-LAgrangian code (GYSELA. Optimizing the writing of the restart files is necessary to reduce the computing impact of crashes. These files require a very large memory space, and particularly so for very large mesh sizes. The limited bandwidth of the data pipe between the comput- ing nodes and the storage system induces a non-scalable part in the GYSELA code, which increases with the mesh size. Indeed the transfer time of RAM to data depends linearly on the files size. The necessity of non synchronized writing-in-file procedure is therefore crucial. A new GYSELA module has been developed. This asynchronous procedure allows the frequent writ- ing of the restart files, whilst preventing a severe slowing down due to the limited writing bandwidth. This method has been improved to generate a checksum control of the restart files, and automatically rerun the code in case of a crash for any cause.

  11. A bio-inspired asynchronous skin system for crack detection applications

    Science.gov (United States)

    Sharp, Nathan; Kuntz, Alan; Brubaker, Cole; Amos, Stephanie; Gao, Wei; Gupta, Gautum; Mohite, Aditya; Farrar, Charles; Mascareñas, David

    2014-05-01

    In many applications of structural health monitoring (SHM) it is imperative or advantageous to have large sensor arrays in order to properly sense the state of health of the structure. Typically these sensor networks are implemented by placing a large number of sensors over a structure and running individual cables from each sensor back to a central measurement station. Data is then collected from each sensor on the network at a constant sampling rate regardless of the current timescales at which events are acting on the structure. These conventional SHM sensor networks have a number of shortfalls. They tend to have a large number of cables that can represent a single point of failure for each sensor as well as add significant weight and installation costs. The constant sampling rate associated with each sensor very quickly leads to large amounts of data that must be analyzed, stored, and possibly transmitted to a remote user. This leads to increased demands on power consumption, bandwidth, and size. It also taxes our current techniques for managing large amounts of data. For the last decade the goal of the SHM community has been to endow structures with the functionality of a biological nervous system. Despite this goal the community has predominantly ignored the biological nervous system as inspiration for building structural nervous systems, choosing instead to focus on experimental mechanics and simulation techniques. In this work we explore the use of a novel, bio-inspired, SHM skin. This skin makes use of distributed computing and asynchronous communication techniques to alleviate the scale of the data management challenge as well as reduce power. The system also periodically sends a ‘heat beat’ signal to provide state-of-health updates. This conductive skin was implemented using conductive ink resistors as well as with graphene-oxide capacitors.

  12. Contrast research of CDMA and GSM network optimization

    Science.gov (United States)

    Wu, Yanwen; Liu, Zehong; Zhou, Guangyue

    2004-03-01

    With the development of mobile telecommunication network, users of CDMA advanced their request of network service quality. While the operators also change their network management object from signal coverage to performance improvement. In that case, reasonably layout & optimization of mobile telecommunication network, reasonably configuration of network resource, improvement of the service quality, and increase the enterprise's core competition ability, all those have been concerned by the operator companies. This paper firstly looked into the flow of CDMA network optimization. Then it dissertated to some keystones in the CDMA network optimization, like PN code assignment, calculation of soft handover, etc. As GSM is also the similar cellular mobile telecommunication system like CDMA, so this paper also made a contrast research of CDMA and GSM network optimization in details, including the similarity and the different. In conclusion, network optimization is a long time job; it will run through the whole process of network construct. By the adjustment of network hardware (like BTS equipments, RF systems, etc.) and network software (like parameter optimized, configuration optimized, capacity optimized, etc.), network optimization work can improve the performance and service quality of the network.

  13. A Link-Level Simulator of the cdma2000 Reverse-Link Physical Layer.

    Science.gov (United States)

    Gharavi, H; Chin, F; Ban, K; Wyatt-Millington, R

    2003-01-01

    The cdma2000 system is an evolutionary enhancement of the IS-95 standards which support 3G services defined by the International Telecommunications Union (ITU). cdma2000 comes in two phases: 1XRTT and 3XRTT (1X and 3X indicates the number of 1.25 MHz wide radio carrier channels used and RTT stands for Radio Transmission Technology). The cdma2000 1XRTT, which operates within a 1.25 MHz bandwidth, can be utilized in existing IS-95 CDMA channels as it uses the same bandwidth, while 3XRTT requires the commitment of 5 MHz bandwidth to support higher data rates. This paper describes a software model implementation of the cdma2000 reverse link and its application for evaluating the effect of rake receiver design parameters on the system performance under various multipath fading conditions. The cdma2000 models were developed at the National Institute of Standards and Technology (NIST), using SPW (Signal Processing Worksystem) commercial software tools. The model has been developed in a generic manner that includes all the reverse link six radio configurations and their corresponding data rates, according to cdma2000 specifications. After briefly reviewing the traffic channel characteristics of the cdma2000 reverse link (subscriber to base station), the paper discusses the rake receiver implementation including an ideal rake receiver. It then evaluates the performance of each receiver for a Spreading Rate 3 (3XRTT) operation, which is considered as a true "3G" cdma2000 technology. These evaluations are based on the vehicular IMT-2000 (International Mobile Telecommunication 2000) channel model using the link budget defined in cdma2000 specifications for the reverse link.

  14. Improvement of BP-Based CDMA Multiuser Detection by Spatial Coupling

    CERN Document Server

    Takeuchi, Keigo; Kawabata, Tsutomu

    2011-01-01

    Kudekar et al. proved that the belief-propagation (BP) threshold for low-density parity-check (LDPC) codes can be boosted up to the maximum-a-posteriori (MAP) threshold by spatial coupling. In this paper, spatial coupling is applied to randomly-spread code-division multiple-access (CDMA) systems in order to improve the performance of BP-based multiuser detection (MUD). Spatially-coupled CDMA systems can be regarded as multi-code CDMA systems with two transmission phases. The large-system analysis shows that spatial coupling can improve the BP performance, while there is a gap between the BP performance and the optimal performance.

  15. Fast frequency hopping codes applied to SAC optical CDMA network

    Science.gov (United States)

    Tseng, Shin-Pin

    2015-06-01

    This study designed a fast frequency hopping (FFH) code family suitable for application in spectral-amplitude-coding (SAC) optical code-division multiple-access (CDMA) networks. The FFH code family can effectively suppress the effects of multiuser interference and had its origin in the frequency hopping code family. Additional codes were developed as secure codewords for enhancing the security of the network. In considering the system cost and flexibility, simple optical encoders/decoders using fiber Bragg gratings (FBGs) and a set of optical securers using two arrayed-waveguide grating (AWG) demultiplexers (DeMUXs) were also constructed. Based on a Gaussian approximation, expressions for evaluating the bit error rate (BER) and spectral efficiency (SE) of SAC optical CDMA networks are presented. The results indicated that the proposed SAC optical CDMA network exhibited favorable performance.

  16. Lack of promoting effects of chronic exposure to 1.95-GHz W-CDMA signals for IMT-2000 cellular system on development of N-ethylnitrosourea-induced central nervous system tumors in F344 rats.

    Science.gov (United States)

    Shirai, Tomoyuki; Ichihara, Toshio; Wake, Kanako; Watanabe, So-ichi; Yamanaka, Yukio; Kawabe, Mayumi; Taki, Masao; Fujiwara, Osamu; Wang, Jianqing; Takahashi, Satoru; Tamano, Seiko

    2007-10-01

    The present study was performed to evaluate effects of a 2-year exposure to an electromagnetic near-field (EMF) equivalent to that generated by cellular phones on tumor development in the central nervous system (CNS) of rats. For this purpose, pregnant F344 rats were given a single administration of N-ethylnitrosourea (ENU) on gestational day 18. A total of 500 pups were divided into five groups, each composed of 50 males and 50 females: Group 1, untreated controls; Group 2, ENU alone; Groups 3 to 5, ENU + EMF (sham exposure and two exposure levels). A 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is a feature of the International Mobile Telecommunication 2000 (IMT-2000) cellular system was employed for exposure of the rat head starting from 5 weeks of age, 90 min a day, 5 days a week, for 104 weeks. Brain average specific absorption rates (SARs) were designed to be .67 and 2.0 W/kg for low and high exposures, respectively. The incidence and numbers of brain tumors in female rats exposed to 1.95-GHz W-CDMA signals showed tendencies to increase but without statistical significance. Overall, no significant increase in incidences or numbers, either in the males or females, was detected in the EMF-exposed groups. In addition, no clear changes in tumor types in the brain were evident. Thus, under the present experimental conditions, exposure of heads of rats to 1.95-GHz W-CDMA signals for IMT-2000 for a 2-year period was not demonstrated to accelerate or otherwise affect ENU-initiated brain tumorigenesis. (c) 2007 Wiley-Liss, Inc.

  17. Introducing a downsized, open computer system with asynchronous transfer mode in PACS and its effect on image data transfer.

    Science.gov (United States)

    Inoue, T; Koyama, Y; Suzuki, H; Oriuchi, N; Aoyagi, K; Tomaru, Y; Ookoshi, A; Yamamoto, S; Nakajima, T; Aoki, J; Endo, K

    1998-01-01

    To assess the effectiveness of the introduction of a downsized, open computer system and asynchronous transfer mode (ATM) as a network in a medium-sized picture archiving and communication system (PACS), we conducted experiments on image data transmission. The speed of image transfer, including registration in the computers in the new PACS, was four to eleven times faster than that in our first PACS. However, the introduction of ATM did not contribute significantly to the improvement of speed of image transfer because of the use of Ethernet branches between the gateway and display workstation computers. A star architecture without Ethernet branches may be suitable for PACS using an ATM network.

  18. Distributed embedded controller development with petri nets application to globally-asynchronous locally-synchronous systems

    CERN Document Server

    Moutinho, Filipe de Carvalho

    2016-01-01

    This book describes a model-based development approach for globally-asynchronous locally-synchronous distributed embedded controllers.  This approach uses Petri nets as modeling formalism to create platform and network independent models supporting the use of design automation tools.  To support this development approach, the Petri nets class in use is extended with time-domains and asynchronous-channels. The authors’ approach uses models not only providing a better understanding of the distributed controller and improving the communication among the stakeholders, but also to be ready to support the entire lifecycle, including the simulation, the verification (using model-checking tools), the implementation (relying on automatic code generators), and the deployment of the distributed controller into specific platforms. Uses a graphical and intuitive modeling formalism supported by design automation tools; Enables verification, ensuring that the distributed controller was correctly specified; Provides flex...

  19. Performance analysis of CDMA-based wireless communication

    African Journals Online (AJOL)

    systems is geared towards high speed, highly mobile multimedia communication applications. In this paper, the performance of a multi-user DS-CDMA communication system operating in a. Rayleigh fading environment is investigated. Performance expressions are derived and the variation of the performance with various ...

  20. Optimal downlink rate allocation in multicell CDMA networks

    NARCIS (Netherlands)

    Endrayanto, A.I.; Gabor, A.F.; Boucherie, Richardus J.

    2007-01-01

    We study downlink rate allocation for a three cells CDMA system. Based on the discretized cell model, the rate optimization problem that maximizes the total downlink rate allocation is formulated. We propose an approximation procedure for obtaining a rate allocation in three cells case. Via

  1. A combinatorial approximation algorithm for CDMA downlink rate allocation

    NARCIS (Netherlands)

    Boucherie, Richardus J.; Bumb, A.F.; Endrayanto, A.I.; Woeginger, Gerhard; Raghavan, S.; Anandalingam, G.

    2006-01-01

    This paper presents a combinatorial algorithm for downlink rate allocation in Code Division Multiple Access (CDMA) mobile networks. By discretizing the coverage area into small segments, the transmit power requirements are characterized via a matrix representation that separates user and system

  2. A combinatorial approximation algorithm for CDMA downlink rate allocation

    NARCIS (Netherlands)

    Boucherie, Richardus J.; Bumb, A.F.; Endrayanto, A.I.; Woeginger, Gerhard

    2004-01-01

    This paper presents a combinatorial algorithm for downlink rate allocation in Code Division Multiple Access (CDMA) mobile networks. By discretizing the coverage area into small segments, the transmit power requirements are characterized via a matrix representation that separates user and system

  3. Admission control for differentiated services in future generation CDMA networks

    NARCIS (Netherlands)

    Tan, H.-P.; Núñez-Queija, R.; Gabor, A.F.; Boxma, O.J.

    2009-01-01

    Future Generation CDMA wireless systems, e.g., 3G, can simultaneously accommodate flow transmissions of users with widely heterogeneous applications. As radio resources are limited, we propose an admission control rule that protects users with stringent transmission bit-rate requirements ("streaming

  4. Design of a Baseband Transceiver for Multicarrier CDMA Communications

    Directory of Open Access Journals (Sweden)

    Tsai Pei-Yun

    2005-01-01

    Full Text Available Multicarrier systems have become popular for their spectral efficiency and robustness against frequency-selective fading. Multicarrier code-division multiple access (MC-CDMA is a technique that combines the advantage of multicarrier modulation with that of code-division multiple access (CDMA to offer reliable high-data-rate downlink cellular communication services. In this paper, we present the architecture of a downlink baseband transceiver using the MC-CDMA technology under the same bandwidth requirement and channel condition as the third-generation wideband CDMA system. In the transmitter, a scrambling code is applied in order to reduce the peak-to-average power ratio (PAPR of the transmitter output. In the receiver, we use a joint weighted least-squares (WLS synchronization error estimation algorithm and a novel channel estimator. Both algorithms greatly enhance the system error-rate performance, as indicated by functional simulation. Simulation results also verify maximum aggregate coded data rates of Mbps from 32/64 users in mobile/stationary multipath fading channel with a 3/4 convolutional code, respectively.

  5. Experimental demonstration of interference avoidance protocol (transmission scheduling) in O-CDMA networks.

    Science.gov (United States)

    Saghari, Poorya; Kamath, P; Arbab, Vahid R; Haghi, Mahta; Willner, Alan E; Bannister, Joe A; Touch, Joe D

    2007-12-10

    We experimentally demonstrate a transmission scheduling algorithm to avoid congestion collapse in O-CDMA networks. Our result shows that transmission scheduling increases the performance of the system by orders of magnitude.

  6. A Link-Level Simulator of the cdma2000 Reverse-Link Physical Layer

    National Research Council Canada - National Science Library

    Gharavi, H; Chin, F; Ban, K; Wyatt-Millington, R

    2003-01-01

    .... This paper describes a software model implementation of the cdma2000 reverse link and its application for evaluating the effect of rake receiver design parameters on the system performance under...

  7. DESIGN AND IMPLEMENTATION OF A CDMA TRANSMITTER FOR MOBILE CELLULAR COMMUNICATIONS

    Directory of Open Access Journals (Sweden)

    R. Muraoka

    2003-07-01

    Full Text Available In this work we describe the design and implementation of a CDMA transmitter with application on thirdgeneration mobile and personal communication systems. We present several experimental results.

  8. Multicarrier Block-Spread CDMA for Broadband Cellular Downlink

    Directory of Open Access Journals (Sweden)

    Leus Geert

    2004-01-01

    Full Text Available Effective suppression of multiuser interference (MUI and mitigation of frequency-selective fading effects within the complexity constraints of the mobile constitute major challenges for broadband cellular downlink transceiver design. Existing wideband direct-sequence (DS code division multiple access (CDMA transceivers suppress MUI statistically by restoring the orthogonality among users at the receiver. However, they call for receive diversity and multichannel equalization to improve the fading effects caused by deep channel fades. Relying on redundant block spreading and linear precoding, we design a so-called multicarrier block-spread- (MCBS-CDMA transceiver that preserves the orthogonality among users and guarantees symbol detection, regardless of the underlying frequency-selective fading channels. These properties allow for deterministic MUI elimination through low-complexity block despreading and enable full diversity gains, irrespective of the system load. Different options to perform equalization and decoding, either jointly or separately, strike the trade-off between performance and complexity. To improve the performance over multi-input multi-output (MIMO multipath fading channels, our MCBS-CDMA transceiver combines well with space-time block-coding (STBC techniques, to exploit both multiantenna and multipath diversity gains, irrespective of the system load. Simulation results demonstrate the superior performance of MCBS-CDMA compared to competing alternatives.

  9. Synchronization Control of Orthogonal Coding Multi-Carrier CDMA on Reverse link

    OpenAIRE

    渡辺, 壮一; Watanabe, Soichi

    1998-01-01

    This paper applies delay time control for a reverse link of orthogonal coding multi-carrier CDMA system. Orthogonal codoing multi-carrier CDMA is a candidate modulation scheme which can offer large capacity and high speed mobile communication systems under a synchronous condition. To combat the synchronous timing error, the delay time control scheme uses delta function preamble signals and adopts closed loop control. The performance of the delay time control scheme is clarified as expanding t...

  10. Throughput Performance of MC-CDMA HARQ Using ICI Cancellation

    Science.gov (United States)

    Fukuda, Kaoru; Nakajima, Akinori; Adachi, Fumiyuki

    Multi-carrier code division multiple access (MC-CDMA) is a promising wireless access technique for the next generation mobile communications systems, in which broadband packet data services will dominate. Hybrid automatic repeat request (HARQ) is an indispensable error control technique for high quality packet data transmission. The HARQ throughput performance of multi-code MC-CDMA degrades due to the presence of residual inter-code interference (ICI) after frequency-domain equalization (FDE). To reduce the residual ICI and improve the throughput performance, a frequency-domain soft interference cancellation (FDSIC) technique can be applied. An important issue is the generation of accurate residual ICI replica for FDSIC. In this paper, low-density parity-check coded (LDPC-coded) MC-CDMA HARQ is considered. We generate the residual ICI replica from a-posteriori log-likelihood ratio (LLR) of LDPC decoder output and evaluate, by computer simulation, the throughput performance in a frequency-selective Rayleigh fading channel. We show that if the residual ICI is removed, MC-CDMA can provide a throughput performance superior to orthogonal frequency division multiplexing (OFDM).

  11. Multiuser receiver for DS-CDMA signals in multipath channels: an enhanced multisurface method.

    Science.gov (United States)

    Mahendra, Chetan; Puthusserypady, Sadasivan

    2006-11-01

    This paper deals with the problem of multiuser detection in direct-sequence code-division multiple-access (DS-CDMA) systems in multipath environments. The existing multiuser detectors can be divided into two categories: (1) low-complexity poor-performance linear detectors and (2) high-complexity good-performance nonlinear detectors. In particular, in channels where the orthogonality of the code sequences is destroyed by multipath, detectors with linear complexity perform much worse than the nonlinear detectors. In this paper, we propose an enhanced multisurface method (EMSM) for multiuser detection in multipath channels. EMSM is an intermediate piecewise linear detection scheme with a run-time complexity linear in the number of users. Its bit error rate performance is compared with existing linear detectors, a nonlinear radial basis function detector trained by the new support vector learning algorithm, and Verdu's optimal detector. Simulations in multipath channels, for both synchronous and asynchronous cases, indicate that it always outperforms all other linear detectors, performing nearly as well as nonlinear detectors.

  12. Space-Time Coded MC-CDMA: Blind Channel Estimation, Identifiability, and Receiver Design

    Directory of Open Access Journals (Sweden)

    Li Hongbin

    2002-01-01

    Full Text Available Integrating the strengths of multicarrier (MC modulation and code division multiple access (CDMA, MC-CDMA systems are of great interest for future broadband transmissions. This paper considers the problem of channel identification and signal combining/detection schemes for MC-CDMA systems equipped with multiple transmit antennas and space-time (ST coding. In particular, a subspace based blind channel identification algorithm is presented. Identifiability conditions are examined and specified which guarantee unique and perfect (up to a scalar channel estimation when knowledge of the noise subspace is available. Several popular single-user based signal combining schemes, namely the maximum ratio combining (MRC and the equal gain combining (EGC, which are often utilized in conventional single-transmit-antenna based MC-CDMA systems, are extended to the current ST-coded MC-CDMA (STC-MC-CDMA system to perform joint combining and decoding. In addition, a linear multiuser minimum mean-squared error (MMSE detection scheme is also presented, which is shown to outperform the MRC and EGC at some increased computational complexity. Numerical examples are presented to evaluate and compare the proposed channel identification and signal detection/combining techniques.

  13. Relay-Assisted Partial Packet Recovery with IDMA Method in CDMA Wireless Network

    CERN Document Server

    Luo, Zhifeng; Wong, Albert Kai-sun; Qiu, Shuisheng

    2010-01-01

    Automatic Repeat Request (ARQ) is an effective technique for reliable transmission of packets in wireless networks. In ARQ, however, only a few erroneous bits in a packet will cause the entire packet to be discarded at the receiver. In this case, it's wasteful to retransmit the correct bit in the received packet. The partial packet recovery only retransmits the unreliable decoded bits in order to increase the throughput of network. In addition, the cooperative transmission based on Interleave-division multiple-access (IDMA) can obtain diversity gains with multiple relays with different locations for multiple sources simultaneously. By exploring the diversity from the channel between relay and destination, we propose a relay-assisted partial packet recovery in CDMA wireless network to improve the performance of throughput. In the proposed scheme, asynchronous IDMA iterative chip-by-chip multiuser detection is utilized as a method of multiple partial recovery, which can be a complementarity in a current CDMA ne...

  14. Asynchronous broadcast for ordered delivery between compute nodes in a parallel computing system where packet header space is limited

    Science.gov (United States)

    Kumar, Sameer

    2010-06-15

    Disclosed is a mechanism on receiving processors in a parallel computing system for providing order to data packets received from a broadcast call and to distinguish data packets received at nodes from several incoming asynchronous broadcast messages where header space is limited. In the present invention, processors at lower leafs of a tree do not need to obtain a broadcast message by directly accessing the data in a root processor's buffer. Instead, each subsequent intermediate node's rank id information is squeezed into the software header of packet headers. In turn, the entire broadcast message is not transferred from the root processor to each processor in a communicator but instead is replicated on several intermediate nodes which then replicated the message to nodes in lower leafs. Hence, the intermediate compute nodes become "virtual root compute nodes" for the purpose of replicating the broadcast message to lower levels of a tree.

  15. The Parallel Asynchronous Differential Evolution Method as a Tool to Analyze Synchrotron Scattering Experimental Data from Vesicular Systems*

    Directory of Open Access Journals (Sweden)

    Zhabitskaya Evgeniya

    2016-01-01

    Full Text Available In this work we use an Asynchronous Differential Evolution (ADE method to estimate parameters of the Separated Form Factor (SFF model which is used to investigate a structure of drug delivery Phospholipid Transport Nano System (PTNS unilamellar vesicles by experimental small angle synchrotron X-ray scattering spectra (SAXS. We compare the efficiency of different optimizing procedures (OP for the search for the SFF-model parameters. It is shown that the probability to find the global solution of this problem by ADE-methods is significantly higher than that by either Nelder-Mead method or a Quasi-Newton method with Davidon-Fletcher-Powell formula. The parallel realization of ADE accelerates the calculations significantly. The speed-up obtained by the parallel realization of ADE and results of the model are presented.

  16. Performance Analysis of New Binary User Codes for DS-CDMA Communication

    Science.gov (United States)

    Usha, Kamle; Jaya Sankar, Kottareddygari

    2016-03-01

    This paper analyzes new binary spreading codes through correlation properties and also presents their performance over additive white Gaussian noise (AWGN) channel. The proposed codes are constructed using gray and inverse gray codes. In this paper, a n-bit gray code appended by its n-bit inverse gray code to construct the 2n-length binary user codes are discussed. Like Walsh codes, these binary user codes are available in sizes of power of two and additionally code sets of length 6 and their even multiples are also available. The simple construction technique and generation of code sets of different sizes are the salient features of the proposed codes. Walsh codes and gold codes are considered for comparison in this paper as these are popularly used for synchronous and asynchronous multi user communications respectively. In the current work the auto and cross correlation properties of the proposed codes are compared with those of Walsh codes and gold codes. Performance of the proposed binary user codes for both synchronous and asynchronous direct sequence CDMA communication over AWGN channel is also discussed in this paper. The proposed binary user codes are found to be suitable for both synchronous and asynchronous DS-CDMA communication.

  17. Pilot-Assisted Adaptive Channel Estimation for Coded MC-CDMA with ICI Cancellation

    Science.gov (United States)

    Yui, Tatsunori; Tomeba, Hiromichi; Adachi, Fumiyuki

    One of the promising wireless access techniques for the next generation mobile communications systems is multi-carrier code division multiple access (MC-CDMA). MC-CDMA can provide good transmission performance owing to the frequency diversity effect in a severe frequency-selective fading channel. However, the bit error rate (BER) performance of coded MC-CDMA is inferior to that of orthogonal frequency division multiplexing (OFDM) due to the residual inter-code interference (ICI) after frequency-domain equalization (FDE). Recently, we proposed a frequency-domain soft interference cancellation (FDSIC) to reduce the residual ICI and confirmed by computer simulation that the MC-CDMA with FDSIC provides better BER performance than OFDM. However, ideal channel estimation was assumed. In this paper, we propose adaptive decision-feedback channel estimation (ADFCE) and evaluate by computer simulation the average BER and throughput performances of turbo-coded MC-CDMA with FDSIC. We show that even if a practical channel estimation is used, MC-CDMA with FDSIC can still provide better performance than OFDM.

  18. SocialRAD: an infrastructure for a secure, cooperative, asynchronous teleradiology system.

    Science.gov (United States)

    Figueiredo, João Filho Matos; Motta, Gustavo Henrique Matos Bezerra

    2013-01-01

    The popularity of teleradiology services has enabled a major advance in the provision of health services to areas with difficult geographical access. However, this potential has also brought with it a number of challenges: the large volume of data, characteristic of imaging tests, and security requirements designed to ensure confidentiality and integrity. Moreover, there is also a number of ethical questions involving the dominant model on the market, whereby this service is outsourced to private companies, and is not directly undertaken by professional radiologists. Therefore, the present paper proposes a cooperative model of teleradiology, where health professionals interact directly with the hospitals providing patient care. This has involved the integration of a wide range of technologies, such as the interconnection models Peer-to-Peer, Cloud Computing, Dynamic DNS, RESTful Web Services, as well as security and interoperability standards, with the aim of promoting a secure, collaborative asynchronous environment. The developed model is currently being used on an experimental basis, providing teleradiology support to cities in the north-eastern hinterland of Brazil, and is fulfilling all expectations.

  19. Direct torque control of an asynchronous machine: observation structures: application to multi-machine/multi-converter systems; Commande directe en couple d'une machine asynchrone: structures d'observations: application aux systemes multimachines-multiconvertisseurs

    Energy Technology Data Exchange (ETDEWEB)

    Belhadj, J.

    2001-07-15

    The aim of this work is the development of an observation structure of the direct torque control (DTC) variables of an asynchronous machine. This structure has to solve the dilemma between its robustness and a minimum calculation time. The control law obtained will be used for the control of multi-machine/multi-converter systems. The new control laws based on direct stator flux control and electromagnetic torque control are studied first, in particular the DTC and the principles of flux and torque adjustment and the associated switching logic. Then, three observation structures are developed: the full order state observer, the sliding mode observer, and the decoupled observer. A comparative study between these three structures and the classical estimator shows that the decoupled observer is an interesting structure which answers the problem of very low-speed operation. In the case of the multi-machine application, two systems are studied: the single inverter/dual-machine system and the dual-inverter/dual-machine system. The control is performed with the DTC and the vectorial control. The DTC gives interesting results for the control of multi-machine systems. In the last part, an architecture is defined for the mono- and multi-machine validation. It consists in a pseudo-experimental validation of the control law associated to the observation structure developed. This validation is performed with a mixed analog/numerical simulation. (J.S.)

  20. Improved Algorithm for Throughput Maximization in MC-CDMA

    OpenAIRE

    Hema Kale; C.G. Dethe; M.M. Mushrif

    2012-01-01

    The Multi-Carrier Code Division Multiple Access (MC-CDMA) is becoming a very significant downlink multiple access technique for high-rate data transmission in the fourth generation wireless communication systems. By means of efficient resource allocation higher data rate i.e. throughput can be achieved. This paper evaluates the performance of criteria used for group (subchannel) allocation employed in downlink transmission, which results in throughput maximization. Proposed algorithm gives th...

  1. MC CDMA PAPR Reduction Techniques using Discrete Transforms and Companding

    OpenAIRE

    Sarala, B.; S Venkateswarulu

    2011-01-01

    High Peak to Average Power Ratio (PAPR) of the transmitted signal is a serious problem in multicarrier modulation systems. In this paper a new technique for reduction in PAPR of the Multicarrier Code Division Multiple Access (MC CDMA) signals based on combining the Discrete Transform either Discrete Cosine Transform (DCT) or multi-resolution Discrete Wavelet Transform (DWT) with companding is proposed. It is analyzed and implemented using MATLAB. Simulation results of reduction in PAPR and po...

  2. 4x4 optical packet switching of asynchronous burst optical packets with a prototype, 4x4 label processing and switching sub-system.

    Science.gov (United States)

    Urata, Ryohei; Nakahara, Tatsushi; Takenouchi, Hirokazu; Segawa, Toru; Ishikawa, Hiroshi; Ohki, Akira; Sugiyama, Hiroki; Nishihara, Susumu; Takahashi, Ryo

    2010-07-19

    We report a prototype, 4x4 (4 input/4 output) label processing and switching sub-system for 10-Gb/s asynchronous burst variable-length optical packets. With the prototype, we perform a 4x4 optical packet switching demonstration, achieving error-free (BERswitching operation for all possible input/output combinations (16 switching paths) simultaneously. Power consumption and latency of the entire, self-contained sub-system is 83 W (includes fan power) and 300 ns, respectively.

  3. A Novel 2-D OFDM-DS-CDMA Receiver with Frequency-Time Spreading

    Science.gov (United States)

    Chen, Joy Iong-Zong

    This paper presents a novel 2-D (2-dimension) receiver that adopts the reception scheme to promote OFDM-DS-CDMA (orthogonal frequency division multiplexing multi-carrier coded-division multiple-access) system performance. The system model includes spread coding and a system block diagram of the 2-D receiver shown graphically with 3-D (three dimensions) plots. The analytical calculation of system performance for an OFDM-DS-CDMA system combined with the proposed receiver equipment is investigated. To evaluate the results from the channel fading effect is considered over the correlated fading environments. The correlated-Nakagami-m statistical distribution is taken into account in the evaluation. The results show that the number of users, the number of subcarriers and the fading channel correlation generally affect OFDM-DS-CDMA systems. The system is also influenced by the Doppler shift and the signal propagation environment (fading parameter).

  4. Full-Duplex Underwater Networking Using CDMA

    National Research Council Canada - National Science Library

    Bektas, Kurtulus

    2004-01-01

    Establishing a full-duplex underwater network, researching and applying a CDMA protocol to the network, providing a recommendation for a full-duplex underwater network and providing recommendations...

  5. Crest Factor Reduction in MC-CDMA Employing Carrier Interferometry Codes

    Directory of Open Access Journals (Sweden)

    Natarajan Balasubramaniam

    2004-01-01

    Full Text Available This paper addresses signal compactness issues in MC-CDMA employing carrier interferometry codes using the measure of crest factor (CF. Carrier interferometry codes, applied to N -carrier MC-CDMA systems, enable 2N users to simultaneously share the system bandwidth with minimal degradation in performance (relative to the N -orthogonal-user case. First, for a fully loaded ( K=N and K=2N users MC-CDMA system with practical values of N , it is shown that the CF in downlink transmission demonstrates desirable properties of low mean and low variance. The downlink CF degrades when the number of users in the system decreases. Next, the high CF observed in the uplink is characterized and the poor CF in a partially loaded downlink as well as uplink is effectively combated using Schroeder's analytical CF reduction techniques.

  6. Effect of whole-body exposure to the 848.5 MHz code division multiple access (CDMA) electromagnetic field on adult neurogenesis in the young, healthy rat brain.

    Science.gov (United States)

    Kim, Hye Sun; Kim, Yeon Ju; Lee, Yu Hee; Lee, Yun-Sil; Choi, Hyung Do; Pack, Jeong-Ki; Kim, Nam; Ahn, Young Hwan

    2015-04-01

    Whether exposure to the 848.5 MHz code division multiple access (CDMA) signal affects adult neurogenesis is unclear. An animal experiment was performed with a reverberation chamber designed as a whole-body CDMA exposure system. Male Sprague-Dawley rats were assigned to three groups (n = 6 per group): Cage-control, sham-exposed, and CDMA-exposed groups. Rats in the CDMA-exposed group were exposed to the CDMA signal at a 2 W/kg whole-body specific absorption rate (SAR) for 1 or 8 h daily, 5 days per week, for 2 weeks. Rats received a single intraperitoneal injection of Bromodeoxyuridine (BrdU) to label proliferative cells daily for the last five consecutive days of CDMA signal exposure. An unbiased stereological method was used to estimate the number of BrdU(+) cells in the subventricular zone (SVZ) and dentate gyrus (DG). We found no significant changes in the number of BrdU(+) cells in the SVZ or DG in the CDMA-exposed rats, compared with rats in the cage-control and sham-exposed groups (p > 0.05). Our results suggest that exposure to the CDMA signal does not affect neurogenesis in the adult rat brain, at least under our experimental conditions.

  7. Direct sequence spread spectrum CDMA in shared spectrum applications

    Science.gov (United States)

    Schilling, Donald L.; Milstein, Laurence B.; Pickholtz, Raymond L.; Miller, Frank

    1991-01-01

    Personal Communication Network (PCN) is an entirely wireless communication system with the capability of assessing the wired telephone system to reach anyone processing only a wired telephone. It is expected to compete with the existing mobile cellular system which connects directly to the wired telephone system. While many PCN systems employ TDMA technology, the PCN system described here uses Broadband CDMA (BCDMA(sup SM)) which is capable of sharing the spectrum with other users and which is extremely resistant to fading caused by multipath.

  8. Influence of the braking power control of the traction asynchronous machine in the voltage vector control system under DC

    Directory of Open Access Journals (Sweden)

    Юлія Олександрівна Слободенюк

    2016-11-01

    Full Text Available At braking the traction motors are transferred to generator mode and produce electrical energy which passes to the contact mains or storage device in the DC mains for further use. Such braking is called regenerative. The resulting electrical energy can be spent by trains in traction mode. Regenerative braking reduces the consumption of electric power for traction. In electric railways of our country more than 3% of the consumed electrical energy is given back to contact mains annually. As this takes place there arises the task to control the braking of the traction motors with minimal impact on electric power quality and maintaining proper braking performance. Based on the analysis of the characteristics of the brake traction of an electric locomotive with asynchronous electric machines the main braking modes have been chosen: at a constant sliding speed and the stator constant voltage; at constant braking power and the stator constant voltage; at a power value more than the nominal braking power; at a constant load torque; at a constant frequency of the stator. The vector control system with the formation of the reactive component of the stator current and the EMF regulator was chosen, basing on the working conditions characteristics in the electric braking mode (recuperation; namely, that the characteristics are defined by the laws regulating the frequency and voltage across the stator windings. This control system can fully reproduce any predetermined trajectory of traction and braking performance and adjust braking power. The offered system with recuperation can be used as a means of compensation in emergency situations with a power failure

  9. Modeling radio link performance in UMTS W-CDMA network simulations

    DEFF Research Database (Denmark)

    Klingenbrunn, Thomas; Mogensen, Preben Elgaard

    2000-01-01

    This article presents a method to model the W-CDMA radio receiver performance, which is usable in network simulation tools for third generation mobile cellular systems. The method represents a technique to combine link level simulations with network level simulations. The method is derived from [1......], which defines a stochastic mapping function from a Signal-to-Interference Ratio into a Bit-Error-Rate for a TDMA system. However, in order to work in a W-CDMA based system, the fact that the Multiple-Access Interference in downlink consists of both Gaussian inter-cell interference and orthogonal intra...

  10. Control of frequency converters for wind power systems with doubly fed asynchronous generators; Regelung von Frequenzumrichtern fuer Windenergieanlagen mit doppelt gespeistem Asynchrongenerator

    Energy Technology Data Exchange (ETDEWEB)

    Engelhardt, Stephan [Woodward SEG GmbH und Co. KG, Kempen (Germany)

    2007-07-01

    Modern wind energy systems are characterized by an extensive use of power electronics. Using complex converter systems is technically and commercially very attractive as it allows an optimized operation of the wind turbine in regard to efficiency, reduced stress to the drive train due to variable speed and feeding wind power with high quality into the grid. For some years wind energy systems with frequency converter and doubly fed asynchronous generator have the biggest market share. The main requirements from grid codes regarding fault ride through operation will be summarized and enhanced control algorithms for this special type of system will be presented. (orig.)

  11. Blind Synchronization in Asynchronous UWB Networks Based on the Transmit-Reference Scheme

    Directory of Open Access Journals (Sweden)

    Leus Geert

    2006-01-01

    Full Text Available Ultra-wideband (UWB wireless communication systems are based on the transmission of extremely narrow pulses, with a duration inferior to a nanosecond. The application of transmit reference (TR to UWB systems allows to side-step channel estimation at the receiver, with a tradeoff of the effective transmission bandwidth, which is reduced by the usage of a reference pulse. Similar to CDMA systems, different users can share the same available bandwidth by means of different spreading codes. This allows the receiver to separate users, and to recover the timing information of the transmitted data packets. The nature of UWB transmissions—short, burst-like packets—requires a fast synchronization algorithm, that can accommodate several asynchronous users. Exploiting the fact that a shift in time corresponds to a phase rotation in the frequency domain, a blind and computationally effcient synchronization algorithm that takes advantage of the shift invariance structure in the frequency domain is proposed in this paper. Integer and fractional delay estimations are considered, along with a subsequent symbol estimation step. This results in a collision-avoiding multiuser algorithm, readily applicable to a fast acquisition procedure in a UWB ad hoc network.

  12. Design and implementation of an all-digital timing recovery system for asynchronous communication

    OpenAIRE

    José Jaime Valenciano-Rojas; Renato Rímolo-Donadio

    2015-01-01

    This work addresses the design and implementation of a timing recovery unit for a communication system with parallel reception, 4-PAM modulation, raised cosine filtering and a nominal sampling frequency of 1,1 GHz. The design of the building blocks within the system, as well as simulation results and the physical implementation in FPGA are discussed.

  13. DPLL implementation in carrier acquisition and tracking for burst DS-CDMA receivers.

    Science.gov (United States)

    Guan, Yun-feng; Zhang, Zhao-yang; Lai, Li-feng

    2003-01-01

    This paper presents the architectures, algorithms, and implementation considerations of the digital phase locked loop (DPLL) used for burst-mode packet DS-CDMA receivers. As we know, carrier offset is a rather challenging problem in CDMA system. According to different applications, different DPLL forms should be adopted to correct different maximum carrier offset in CDMA systems. One classical DPLL and two novel DPLL forms are discussed in the paper. The acquisition range of carrier offset can be widened by using the two novel DPLL forms without any performance degradation such as longer acquisition time or larger variance of the phase error. The maximum acquisition range is 1/(4T), where T is the symbol period. The design can be implemented by FPGA directly.

  14. Demonstration of high-speed multi-user multi-carrier CDMA visible light communication

    Science.gov (United States)

    Yang, Chao; Wang, Yuanquan; Wang, Yiguang; Huang, Xingxing; Chi, Nan

    2015-02-01

    We experimentally demonstrated a high-speed multi-user multi-carrier code-division multiple access (MC-CDMA) visible light communication (VLC) system. By employing a commercially available red light emitting diode (LED) and an avalanche photo diode (APD), we achieved a 16-user VLC system enabled by MC-CDMA, pre- and post-equalization, with an overall bit rate of 750 Mb/s over 1.5 m free-space transmission. The measured bit error ratio (BER) of each user is below the 7% pre-forward-error-correction (pre-FEC) threshold of 3.8×10-3.

  15. Enhancing the Performance of Random Access Networks with Random Packet CDMA and Joint Detection

    Directory of Open Access Journals (Sweden)

    Behrouz Farhang-Boroujeny

    2008-09-01

    Full Text Available Random packet CDMA (RP-CDMA is a recently proposed random transmission scheme which has been designed from the beginning as a cross-layer method to overcome the restrictive nature of the Aloha protocol. Herein, we more precisely model its performance and investigate throughput and network stability. In contrast to previous works, we adopt the spread Aloha model for header transmission, and the performance of different joint detection methods for the payload data is investigated. Furthermore, we introduce performance measures for multiple access systems based on the diagonal elements of a modified multipacket reception matrix, and show that our measures describe the upper limit of the vector of stable arrival rates for a finite number of users. Finally, we simulate queue sizes and throughput characteristics of RP-CDMA with various receiver structures and compare them to spread Aloha.

  16. A performance analysis of DS-CDMA and SCPC VSAT networks

    Science.gov (United States)

    Hayes, David P.; Ha, Tri T.

    1990-01-01

    Spread-spectrum and single-channel-per-carrier (SCPC) transmission techniques work well in very small aperture terminal (VSAT) networks for multiple-access purposes while allowing the earth station antennas to remain small. Direct-sequence code-division multiple-access (DS-CDMA) is the simplest spread-spectrum technique to use in a VSAT network since a frequency synthesizer is not required for each terminal. An examination is made of the DS-CDMA and SCPC Ku-band VSAT satellite systems for low-density (64-kb/s or less) communications. A method for improving the standardf link analysis of DS-CDMA satellite-switched networks by including certain losses is developed. The performance of 50-channel full mesh and star network architectures is analyzed. The selection of operating conditions producing optimum performance is demonstrated.

  17. Enhancing the Performance of Random Access Networks with Random Packet CDMA and Joint Detection

    Science.gov (United States)

    Kempter, Roland; Amini, Peiman; Farhang-Boroujeny, Behrouz

    2008-12-01

    Random packet CDMA (RP-CDMA) is a recently proposed random transmission scheme which has been designed from the beginning as a cross-layer method to overcome the restrictive nature of the Aloha protocol. Herein, we more precisely model its performance and investigate throughput and network stability. In contrast to previous works, we adopt the spread Aloha model for header transmission, and the performance of different joint detection methods for the payload data is investigated. Furthermore, we introduce performance measures for multiple access systems based on the diagonal elements of a modified multipacket reception matrix, and show that our measures describe the upper limit of the vector of stable arrival rates for a finite number of users. Finally, we simulate queue sizes and throughput characteristics of RP-CDMA with various receiver structures and compare them to spread Aloha.

  18. A mobile and asynchronous electronic data capture system for epidemiologic studies.

    Science.gov (United States)

    Meyer, Jens; Fredrich, Daniel; Piegsa, Jens; Habes, Mohamad; van den Berg, Neeltje; Hoffmann, Wolfgang

    2013-06-01

    A Central Data Management (CDM) system based on electronic data capture (EDC) software and study specific databases is an essential component for assessment and management of large data volumes in epidemiologic studies. Conventional CDM systems using web applications for data capture depend on permanent access to a network. However, in many study settings permanent network access cannot be guaranteed, e.g. when participants/patients are visited in their homes. In such cases a different concept for data capture is needed. The utilized EDC software must be able to ensure data capture as stand-alone instance and to synchronize captured data with the server at a later point in time. This article describes the design of the mobile information capture (MInCa) system an EDC software meeting these requirements. In particular, we focus on client and server design, data synchronization, and data privacy as well as data security measures. The MInCa software has already proven its efficiency in epidemiologic studies revealing strengths and weaknesses concerning both concept and practical application which will be addressed in this article. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  19. Communication and Agreement Abstractions for Fault-Tolerant Asynchronous Distributed Systems

    CERN Document Server

    Raynal, Michel

    2010-01-01

    Understanding distributed computing is not an easy task. This is due to the many facets of uncertainty one has to cope with and master in order to produce correct distributed software. Considering the uncertainty created by asynchrony and process crash failures in the context of message-passing systems, the book focuses on the main abstractions that one has to understand and master in order to be able to produce software with guaranteed properties. These fundamental abstractions are communication abstractions that allow the processes to communicate consistently (namely the register abstraction

  20. Comparison of FDMA and CDMA for second generation land-mobile satellite communications

    Science.gov (United States)

    Yongacoglu, A.; Lyons, R. G.; Mazur, B. A.

    1990-01-01

    Code Division Multiple Access (CDMA) and Frequency Division Multiple Access (FDMA) (both analog and digital) systems capacities are compared on the basis of identical link availabilities and physical propagation models. Parameters are optimized for a bandwidth limited, multibeam environment. For CDMA, the benefits of voice activated carriers, antenna discrimination, polarization reuse, return link power control and multipath suppression are included in the analysis. For FDMA, the advantages of bandwidth efficient modulation/coding combinations, voice activated carriers, polarization reuse, beam placement, and frequency staggering were taken into account.

  1. Spectral Efficiency of Random Time-Hopping CDMA

    OpenAIRE

    Ferrante, Guido Carlo; Di Benedetto, Maria-Gabriella

    2013-01-01

    Traditionally paired with impulsive communications, Time-Hopping CDMA (TH-CDMA) is a multiple access technique that separates users in time by coding their transmissions into pulses occupying a subset of $N_\\mathsf{s}$ chips out of the total $N$ included in a symbol period, in contrast with traditional Direct-Sequence CDMA (DS-CDMA) where $N_\\mathsf{s}=N$. This work analyzes TH-CDMA with random spreading, by determining whether peculiar theoretical limits are identifiable, with both optimal a...

  2. An analytical model for CDMA downlink rate optimization taking into account uplink coverage restrictions

    NARCIS (Netherlands)

    Endrayanto, A.I.; van den Berg, Hans Leo; Boucherie, Richardus J.

    2005-01-01

    This paper models and analyzes downlink and uplink power assignment in code division multiple access (CDMA) mobile networks. By discretizing the area into small segments, the power requirements are characterized via a matrix representation that separates user and system characteristics. We obtain a

  3. A multiple-choice knapsack based algorithm for CDMA downlink rate differentiation under uplink coverage restrictions

    NARCIS (Netherlands)

    Endrayanto, A.I.; Bumb, A.F.; Boucherie, Richardus J.

    2004-01-01

    This paper presents an analytical model for downlink rate allocation in Code Division Multiple Access (CDMA) mobile networks. By discretizing the coverage area into small segments, the transmit power requirements are characterized via a matrix representation that separates user and system

  4. An analytical model for CDMA downlink rate optimization taking into account uplink coverage restriction

    NARCIS (Netherlands)

    Endrayanto, A.I.; van den Berg, Hans Leo; Boucherie, Richardus J.

    2003-01-01

    This paper models and analyzes downlink and uplink power assignment in Code Division Multiple Access (CDMA) mobile networks. By discretizing the area into small segments, the power requirements are characterized via a matrix representation that separates user and system characteristics. We obtain a

  5. Asynchronous Multiparty Computation

    DEFF Research Database (Denmark)

    Damgård, Ivan Bjerre; Geisler, Martin; Krøigaard, Mikkel

    2009-01-01

    less than n/3 players. We also present a software framework for implementation of asynchronous protocols called VIFF (Virtual Ideal Functionality Framework), which allows automatic parallelization of primitive operations such as secure multiplications, without having to resort to complicated...

  6. User satisfaction with asynchronous telemedicine: a study of users of Santa Catarina's system of telemedicine and telehealth.

    Science.gov (United States)

    von Wangenheim, Aldo; de Souza Nobre, Luiz Felipe; Tognoli, Heitor; Nassar, Silvia Modesto; Ho, Kendall

    2012-06-01

    User satisfaction analyses in synchronous telemedicine and teleconsultation environments have been widely performed and generally show satisfied users. In the field of asynchronous telemedicine, however, satisfaction studies were performed only in one single location or with a restricted set of users. With the aim of offering an exemplar evaluation of the impact of the statewide use of a large-scale asynchronous telemedicine network on the satisfaction of the involved users, this study presents the results obtained from a survey of the perceived quality of the service by both patients and healthcare staff. For this purpose, a survey with satisfaction questionnaires was performed with 564 patients from seven upstate municipalities and 56 healthcare professionals from 46 municipalities, using a methodology from the process improvement field. The collected data were quantified and underwent statistical analysis, which showed a clear perception of the improvement in the quality of service by both patients and healthcare professionals. The present findings also showed that both patients and healthcare professionals felt that introducing these new technologies was a positive step, even in upstate areas and when they involved great changes in the usual processes of primary care.

  7. Cross-layer optimization for video transmission over multirate GMC-CDMA wireless links.

    Science.gov (United States)

    Bandyopadhyay, Saurav K; Partasides, George; Kondi, Lisimachos P

    2008-06-01

    In this paper, we consider the problem of video transmission over wireless generalized multicarrier code division multiple access (GMC-CDMA) systems. Such systems offer deterministic elimination of multiple access interference. A scalable video source codec is used and a multirate setup is assumed, i.e., each video user is allowed to occupy more than one GMC-CDMA channels. Furthermore, each of these channels can utilize a different number of subcarriers. We propose a cross-layer optimization method to select the source coding rate, channel coding rate, number of subcarriers per GMC-CDMA channel and transmission power per GMC-CDMA channel given a maximum transmission power for each video user and an available chip rate. Universal rate distortion characteristics (URDC) are used to approximate the expected distortion at the receiver. The proposed algorithm is optimal in the operational rate distortion sense, subject to the specific setup used and the approximation caused by the use of the URDC. Experimental results are presented and conclusions are drawn.

  8. Average Likelihood Methods for Code Division Multiple Access (CDMA)

    Science.gov (United States)

    2014-05-01

    AVERAGE LIKELIHOOD METHODS FOR CODE DIVISION MULTIPLE ACCESS ( CDMA ) MAY 2014 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE; DISTRIBUTION...REPORT 3. DATES COVERED (From - To) OCT 2011 – OCT 2013 4. TITLE AND SUBTITLE AVERAGE LIKELIHOOD METHODS FOR CODE DIVISION MULTIPLE ACCESS ( CDMA ) 5a...precision parameter from the joint probability of the code matrix. For a full loaded CDMA signal, the average likelihood depends exclusively on feature

  9. Multiparty Asynchronous Session Types

    DEFF Research Database (Denmark)

    Honda, Kohei; Yoshida, Nobuko; Carbone, Marco

    2016-01-01

    . This work extends the foregoing theories of binary session types to multiparty, asynchronous sessions, which often arise in practical communication-centered applications. Presented as a typed calculus for mobile processes, the theory introduces a new notion of types in which interactions involving multiple......Communication is a central elements in software development. As a potential typed foundation for structured communication-centered programming, session types have been studied over the past decade for a wide range of process calculi and programming languages, focusing on binary (two-party) sessions...... peers are directly abstracted as a global scenario. Global types retain the friendly type syntax of binary session types while specifying dependencies and capturing complex causal chains of multiparty asynchronous interactions. A global type plays the role of a shared agreement among communication peers...

  10. Contribution à l’étude des performances et limitations d’une liaison CDMA optique haut débit

    OpenAIRE

    BOUDAOUD, Radhwane

    2010-01-01

    La technique de CDMA optique permet le partage des ressources et données dans les réseaux de télécommunications optiques de manière simultanée et asynchrone. L’intérêt de la CMDA optique réside dans l’utilisation d’une large bande passante sur le support de transmission qui est la fibre optique. La transmission des données dans une liaison de CDMA optique peut introduire plusieurs limitations, comme l’interférence d’accès multiple (IAM). Ce dernier est dû aux produits d’inte...

  11. Asynchronous parallel search in global optimization problems

    Energy Technology Data Exchange (ETDEWEB)

    Archetti, F.; Schoen, F.

    1982-01-01

    A class of asynchronous parallel search methods is proposed in order to solve the global optimization problem on a multiprocessor system, consisting of several processors which can communicate through a set of global variables contained in a memory shared by all processors. The speed-up ratio and memory contension effects are experimentally analyzed for some algorithms of this class. 6 references.

  12. Dynamic Performances of Asynchronous Machines | Ubeku ...

    African Journals Online (AJOL)

    The dynamic performance of electrical machines is affected by low and unbalanced voltages, frequency variations in its supply systems and pulsating load torques. In this paper the d-q axis model in the synchronous reference frame is used in the dynamic analysis on the performance of an asynchronous machine working ...

  13. CDMA and TDMA based neural nets.

    Science.gov (United States)

    Herrero, J C

    2001-06-01

    CDMA and TDMA telecommunication techniques were established long time ago, but they have acquired a renewed presence due to the rapidly increasing mobile phones demand. In this paper, we are going to see they are suitable for neural nets, if we leave the concept "connection" between processing units and we adopt the concept "messages" exchanged between them. This may open the door to neural nets with a higher number of processing units and flexible configuration.

  14. High-Performance Wireless via the Merger of CI Chip-Shaped DS-CDMA and Oscillating-Beam Smart Antenna Arrays

    Directory of Open Access Journals (Sweden)

    Nassar Carl R

    2004-01-01

    Full Text Available We introduce a novel merger of direct sequence code division multiple access (DS-CDMA and smart antenna arrays. With regard to the DS-CDMA scheme, we employ carrier interferometry DS-CDMA (CI/DS-CDMA, a novel implementation of DS-CDMA where chips are decomposable into narrowband frequency components. With regard to the antenna array, we deploy the oscillating-beam smart array. Here, applying proper time-varying phases to the array elements, we create small movement (oscillation in the antenna array's pattern, while steering the antenna pattern main lobe to the position of the intended user. The oscillating antenna pattern creates a time-varying channel with a controllable coherence time. This, in turn, provides transmit diversity in the form of a time diversity gain at the mobile receiver side. At the receiver, three stages of combining are available: combining time components of the received signal within symbol duration (each experiencing a different fade to enhance performance via time diversity; combining frequency components which make up the CI/DS-CDMA chip to enhance the performance via frequency diversity; and combining across chips to eliminate the interfering users on the system. Merging CI/DS-CDMA with the oscillating-beam smart antenna at the base station, we achieve very high capacity via the merger of SDMA (available through directionality of the antenna array and code division multiple access (inherent in CI/DS-CDMA, and very high performance via the construction of receivers that exploit both transmit diversity and frequency diversity. We present the performance gains of the proposed merger.

  15. Adaptive wavefront control with asynchronous stochastic parallel gradient descent clusters.

    Science.gov (United States)

    Vorontsov, Mikhail A; Carhart, Gary W

    2006-10-01

    A scalable adaptive optics (AO) control system architecture composed of asynchronous control clusters based on the stochastic parallel gradient descent (SPGD) optimization technique is discussed. It is shown that subdivision of the control channels into asynchronous SPGD clusters improves the AO system performance by better utilizing individual and/or group characteristics of adaptive system components. Results of numerical simulations are presented for two different adaptive receiver systems based on asynchronous SPGD clusters-one with a single deformable mirror with Zernike response functions and a second with tip-tilt and segmented wavefront correctors. We also discuss adaptive wavefront control based on asynchronous parallel optimization of several local performance metrics-a control architecture referred to as distributed adaptive optics (DAO). Analysis of the DAO system architecture demonstrated the potential for significant increase of the adaptation process convergence rate that occurs due to partial decoupling of the system control clusters optimizing individual performance metrics.

  16. First satellite mobile communication trials using BLQS-CDMA

    Science.gov (United States)

    Luzdemateo, Maria; Johns, Simon; Dothey, Michel; Vanhimbeeck, Carl; Deman, Ivan; Wery, Bruno

    1993-01-01

    In this paper, technical results obtained in the first MSBN Land mobile technical trial are reported. MSBN (Mobile Satellite Business Network) is a new program undertaken by the European Space Agency (ESA) to promote mobile satellite communication in Europe, in particular voice capability. The first phase of the MSBN system implementation plan is an experimental phase. Its purpose is to evaluate through field experiments the performance of the MSBN system prior to finalization of its specifications. Particularly, the objective is to verify in the field and possibly improve the performance of the novel satellite access technique BLQS-CDMA (Band Limited Quasi-Synchronous-Code Division Multiple Access), which is proposed as baseline for the MSBN.

  17. Super-Orthogonal Space-Time Turbo Transmit Diversity for CDMA

    Directory of Open Access Journals (Sweden)

    Pieter G. W. van Rooyen

    2005-05-01

    Full Text Available Studies have shown that transmit and receive diversity employing a combination of multiple transmit-receive antennas (given ideal channel state information (CSI and independent fading between antenna pairs will potentially yield maximum achievable system capacity. In this paper, the concept of a layered super-orthogonal turbo transmit diversity (SOTTD for downlink direct-sequence code-division multiple-access (CDMA systems is explored. This open-loop transmit diversity technique improves the downlink performance by using a small number of antenna elements at the base station and a single antenna at the handset. In the proposed technique, low-rate super-orthogonal code-spread CDMA is married with code-division transmit diversity (CDTD. At the mobile receiver, space-time (ST RAKE CDTD processing is combined with iterative turbo code-spread decoding to yield large ST gains. The performance of the SOTTD system is compared with single- and multiantenna turbo-coded (TC CDTD systems evaluated over a frequency-selective Rayleigh fading channel. The evaluation is done both by means of analysis and computer simulations. The performance results illustrate the superior performance of SOTTD compared to TC CDTD systems over practically the complete useful capacity range of CDMA. It is shown that the performance degradation characteristic of TC CDTD at low system loads (due to the inherent TC error floor is alleviated by the SOTTD system.

  18. A Review on Successive Interference Cancellation Scheme Based on Optical CDMA Network

    Science.gov (United States)

    Alsowaidi, N.; Eltaif, T.; Mokhtar, M. R.

    2014-12-01

    Due to various desirable features of optical code division multiple access (OCDMA), it is believed this technique once developed and commercially available will be an integral part of optical access networks. Optical CDMA system suffers from a problem called multiple access interference (MAI) which limits the number of active users, it occurs when number of active users share the same carriers. The aim of this paper is to review successive interference cancellation (SIC) scheme based on optical CDMA system. The paper also reviews the system performance in presence of shot noise, thermal noise, and phase-induced intensity noise (PIIN). A comprehensive review on the mathematical model of SIC scheme using direct detection (DS) and spectral amplitude coding (SAC) were presented in this article.

  19. A Block-Asynchronous Relaxation Method for Graphics Processing Units

    Energy Technology Data Exchange (ETDEWEB)

    Antz, Hartwig [Karlsruhe Inst. of Technology (KIT) (Germany); Tomov, Stanimire [Univ. of Tennessee, Knoxville, TN (United States); Dongarra, Jack [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Manchester (United Kingdom); Heuveline, Vincent [Karlsruhe Inst. of Technology (KIT) (Germany)

    2011-11-30

    In this paper, we analyze the potential of asynchronous relaxation methods on Graphics Processing Units (GPUs). For this purpose, we developed a set of asynchronous iteration algorithms in CUDA and compared them with a parallel implementation of synchronous relaxation methods on CPU-based systems. For a set of test matrices taken from the University of Florida Matrix Collection we monitor the convergence behavior, the average iteration time and the total time-to-solution time. Analyzing the results, we observe that even for our most basic asynchronous relaxation scheme, despite its lower convergence rate compared to the Gauss-Seidel relaxation (that we expected), the asynchronous iteration running on GPUs is still able to provide solution approximations of certain accuracy in considerably shorter time then Gauss- Seidel running on CPUs. Hence, it overcompensates for the slower convergence by exploiting the scalability and the good fit of the asynchronous schemes for the highly parallel GPU architectures. Further, enhancing the most basic asynchronous approach with hybrid schemes – using multiple iterations within the ”subdomain” handled by a GPU thread block and Jacobi-like asynchronous updates across the ”boundaries”, subject to tuning various parameters – we manage to not only recover the loss of global convergence but often accelerate convergence of up to two times (compared to the effective but difficult to parallelize Gauss-Seidel type of schemes), while keeping the execution time of a global iteration practically the same. This shows the high potential of the asynchronous methods not only as a stand alone numerical solver for linear systems of equations fulfilling certain convergence conditions but more importantly as a smoother in multigrid methods. Due to the explosion of parallelism in todays architecture designs, the significance and the need for asynchronous methods, as the ones described in this work, is expected to grow.

  20. Approximate equiangular tight frames for compressed sensing and CDMA applications

    Science.gov (United States)

    Tsiligianni, Evaggelia; Kondi, Lisimachos P.; Katsaggelos, Aggelos K.

    2017-12-01

    Performance guarantees for recovery algorithms employed in sparse representations, and compressed sensing highlights the importance of incoherence. Optimal bounds of incoherence are attained by equiangular unit norm tight frames (ETFs). Although ETFs are important in many applications, they do not exist for all dimensions, while their construction has been proven extremely difficult. In this paper, we construct frames that are close to ETFs. According to results from frame and graph theory, the existence of an ETF depends on the existence of its signature matrix, that is, a symmetric matrix with certain structure and spectrum consisting of two distinct eigenvalues. We view the construction of a signature matrix as an inverse eigenvalue problem and propose a method that produces frames of any dimensions that are close to ETFs. Due to the achieved equiangularity property, the so obtained frames can be employed as spreading sequences in synchronous code-division multiple access (s-CDMA) systems, besides compressed sensing.

  1. Effects of electromagnetic fields emitted from W-CDMA-like mobile phones on sleep in humans.

    Science.gov (United States)

    Nakatani-Enomoto, Setsu; Furubayashi, Toshiaki; Ushiyama, Akira; Groiss, Stefan Jun; Ueshima, Kazumune; Sokejima, Shigeru; Simba, Ally Y; Wake, Kanako; Watanabe, So-ichi; Nishikawa, Masami; Miyawaki, Kaori; Taki, Masao; Ugawa, Yoshikazu

    2013-12-01

    In this study, we investigated subjective and objective effects of mobile phones using a Wideband Code Division Multiple Access (W-CDMA)-like system on human sleep. Subjects were 19 volunteers. Real or sham electromagnetic field (EMF) exposures for 3 h were performed before their usual sleep time on 3 consecutive days. They were exposed to real EMF on the second or third experimental day in a double-blind design. Sleepiness and sleep insufficiency were evaluated the next morning. Polysomnograms were recorded for analyses of the sleep variables and power spectra of electroencephalograms (EEG). No significant differences were observed between the two conditions in subjective feelings. Sleep parameters including sleep stage percentages and EEG power spectra did not differ significantly between real and sham exposures. We conclude that continuous wave EMF exposure for 3 h from a W-CDMA-like system has no detectable effects on human sleep. © 2013 Wiley Periodicals, Inc.

  2. TCDQ-TCT retraction and losses during asynchronous beam dump

    CERN Document Server

    Bracco, Chiara; Quaranta, Elena; CERN. Geneva. ATS Department

    2016-01-01

    The protection provided by the TCDQs in case of asynchronous beam dump depends strongly on their correct setup. They have to respect the strict hierarchy of the full collimation system and shield the tertiary collimators in the experimental regions. This MD aimed at performing asynchronous beam dump tests with different configurations, in order to assess the minimum allowed retraction between TCTs and TCDQs and, as a consequence, on the The protection provided by the TCDQs in case of asynchronous beam dump depends strongly on their correct setup. They have to respect the strict hierarchy of the full collimation system and shield the tertiary collimators in the experimental regions. This MD aimed at performing asynchronous beam dump tests with different configurations, in order to assess the minimum allowed retraction between TCTs and TCDQs and, as a consequence, on the β* reach.

  3. Pro asynchronous programming with .NET

    CERN Document Server

    Blewett, Richard; Ltd, Rock Solid Knowledge

    2014-01-01

    Pro Asynchronous Programming with .NET teaches the essential skill of asynchronous programming in .NET. It answers critical questions in .NET application development, such as: how do I keep my program responding at all times to keep my users happy how do I make the most of the available hardware how can I improve performanceIn the modern world, users expect more and more from their applications and devices, and multi-core hardware has the potential to provide it. But it takes carefully crafted code to turn that potential into responsive, scalable applications.With Pro Asynchronous Programming

  4. BER Performance Analysis of MC-CDMA with Overlap-FDE

    Science.gov (United States)

    Tomeba, Hiromichi; Takeda, Kazuaki; Adachi, Fumiyuki

    Recently, multi-carrier code division multiple access (MC-CDMA) has been attracting much attention as a broadband wireless access technique for the next generation mobile communication systems. Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can take advantage of the channel frequency-selectivity and improve the average bit error rate (BER) performance due to frequency-diversity gain. The conventional FDE requires the insertion of the guard interval (GI) to avoid the inter-block interference (IBI), resulting in the transmission efficiency loss. In this paper, an overlap FDE technique, which requires no GI insertion, is presented for MC-CDMA transmission. An expression for the conditional BER is derived for the given set of channel gains. The average BER performance in a frequency-selective Rayleigh fading channel is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation of the signal transmission.

  5. Asynchronous Communication Scheme For Hypercube Computer

    Science.gov (United States)

    Madan, Herb S.

    1988-01-01

    Scheme devised for asynchronous-message communication system for Mark III hypercube concurrent-processor network. Network consists of up to 1,024 processing elements connected electrically as though were at corners of 10-dimensional cube. Each node contains two Motorola 68020 processors along with Motorola 68881 floating-point processor utilizing up to 4 megabytes of shared dynamic random-access memory. Scheme intended to support applications requiring passage of both polled or solicited and unsolicited messages.

  6. Reducing energy with asynchronous circuits

    OpenAIRE

    Rivas Barragan, Daniel

    2012-01-01

    Reducing energy consumption using asynchronous circuits. The elastic clocks approach has been implemented along with a closed-feedback loop in order to achieve a lower energy consumption along with more reliability in integrated circuits.

  7. SOFT AND SOFTER HANDOVER PERFORMANCE OF CDMA

    Directory of Open Access Journals (Sweden)

    Lina wati

    2010-12-01

    Full Text Available One of telecommunication providers in Indonesia applies CDMA2000 1x technology. The technology hasmany advantages such as larger channel capacity of BTS (Base Transceiver Station. On the other hand, thecapacity depends on user’s density. Therefore to guarantee voice connection when user or mobile station (MS isalways moving from one cell to others, handover technique is needed. However the technique can be failed for manyreasons. Therefore impact of call attempt on softer and soft handover performance is investigated. Hence the paperexamined soft – softer handover performance of CDMA in BTS (Base Transceiver Station, BSC, and Sectors inboth sub-urban and rural areas in Denpasar, Bali with area code of 0361.The research has been done in rural and suburban area with call area code ‘0361’. The analyses includedregression and simple linear correlation applications. The results showed that number of call attempts affected thefailure of soft and softer handover technique dominantly. Generally, average level of success both handover in bothrural and suburban area were about 99% which are above KPI (Key Performance Indicator reference at 98.50%.However in rural area, other factors such as blocking called attempt and error called number have caused the softerhandover failure.

  8. Adaptive Transmitter Precoding for Time Division Duplex CDMA in Fading Multipath Channels: Strategy and Analysis

    Directory of Open Access Journals (Sweden)

    Daryl Reynolds

    2003-01-01

    Full Text Available The recently developed blind adaptive techniques for multiuser detection in code division multiple access (CDMA systems offer an attractive compromise of performance and complexity. However, the desire to further reduce complexity at the mobile unit has led to the investigation of techniques that move signal processing from the mobile unit to the base station. In this paper, we investigate transmitter precoding for downlink time division duplex (TDD code division multiple access (CDMA communications. In particular, we develop a linear minimum mean square error precoding strategy using blind channel estimation for fading multipath channels that allows for simple matched filtering at the mobile unit and is easy to make adaptive. We also present a performance analysis using tools developed for the analysis of conventional (receiver-based linear blind multiuser detection in unknown channels. We compare the analytical and simulation results to traditional receiver-based blind multiuser detection. It is seen that transmitter precoding offers a reasonable alternative for TDD-mode CDMA when minimizing computational complexity at the mobile unit is a priority.

  9. Totally Asynchronous Interference Channels

    CERN Document Server

    Moshksar, Kamyar

    2010-01-01

    This paper addresses an interference channel consisting of $\\mathbf{n}$ active users sharing $u$ frequency sub-bands. Users are asynchronous meaning there exists a mutual delay between their transmitted codes. A stationary model for interference is considered by assuming the starting point of an interferer's data is uniformly distributed along the codeword of any user. The spectrum is divided to private and common bands each containing $v_{\\mathrm{p}}$ and $v_{\\mathrm{c}}$ frequency sub-bands respectively. We consider a scenario where all transmitters are unaware of the number of active users and the channel gains. The optimum $v_{\\mathrm{p}}$ and $v_{\\mathrm{c}}$ are obtained such that the so-called outage capacity per user is maximized. If $\\Pr\\{\\mathbf{n}\\leq 2\\}=1$, upper and lower bounds on the mutual information between the input and output of the channel for each user are derived using a genie-aided technique. The proposed bounds meet each other as the code length grows to infinity yielding a closed ex...

  10. BACKGROUNDS OF EXPERIMENTAL INVESTIGATION OF ELECTROMAGNETIC COMPATIBILITY OF TRACTION ASYNCHRONOUS ELECTRIC DRIVES IN THE STRUCTURE OF DC TRACTION POWER SUPPLY SYSTEM

    Directory of Open Access Journals (Sweden)

    YU. S. Bondarenko

    2014-04-01

    Full Text Available Purpose. Application of physical modeling as a tool for research of any events or systems is becoming more widespread, including the field of railway transport. At the same time the adequacy of results that can be obtained, depends largely on the similarity degree of the physical model to real system. From the standpoint of the traction asynchronous electric drive (TAED research together with the traction power supply system research, the similarity can not be determined by the direct proportion of the parameters, because the processes nature accompanying the operation of these systems is non-linear. These features should be taken into account in the experimental setup, the basis for constructing of which is establishing of the system similarity that defines the purpose of this paper. Methodology. At the heart of the experimental setup creation laid reproduction of processes of energy transformation in the system of the DC traction power supply. Determination of the similarity degree of the proposed facility to the real system was carried out using the basic theorems of the similarity theory, their additional provisions on the complexity and nonlinear systems, as well as elements of mathematical analysis. Findings. According to the results of work: 1 The block diagram, the energy conversion mechanism of which is similar to the real system was received. This scheme is the basis of experimental setup, built in the future for the study of electromagnetic compatibility of TAED in the structure of DC traction electric power supply system. 2 Similarity of obtained structural scheme with the real system with the mechanism definition of calculating the scaling relations was established. Originality. In the process of establishing the similarity a simplified method for determining the scaling relations for nonlinear systems was suggested. They are identical in their structure components, but have different capacities. Practical value. Experimental

  11. Neurological abnormalities associated with CDMA exposure.

    Science.gov (United States)

    Hocking, B; Westerman, R

    2001-09-01

    Dysaesthesiae of the scalp and neurological abnormality after mobile phone use have been reported previously, but the roles of the phone per se or the radiations in causing these findings have been questioned. We report finding a neurological abnormality in a patient after accidental exposure of the left side of the face to mobile phone radiation [code division multiple access (CDMA)] from a down-powered mobile phone base station antenna. He had headaches, unilateral left blurred vision and pupil constriction, unilateral altered sensation on the forehead, and abnormalities of current perception thresholds on testing the left trigeminal ophthalmic nerve. His nerve function recovered during 6 months follow-up. His exposure was 0.015-0.06 mW/cm(2) over 1-2 h. The implications regarding health effects of radiofrequency radiation are discussed.

  12. ASCERTAINMENT OF THE EQUIVALENT CIRCUIT PARAMETERS OF THE ASYNCHRONOUS MACHINE

    Directory of Open Access Journals (Sweden)

    V. S. Safaryan

    2015-01-01

    Full Text Available The article considers experimental and analytical determination of the asynchronous machine equivalent-circuit parameters with application of the reference data. Transient processes investigation of the asynchronous machines necessitates the equivalent circuit parameters (resistance impedance, inductances and coefficient of the stator-rotor contours mutual inductance that help form the transitory-process mathematical simulation model. The reference books do not provide those parameters; they instead give the rated ones (active power, voltage, slide, coefficient of performance and capacity coefficient as well as the ratio of starting and nominal currents and torques. The noted studies on the asynchronous machine equivalent-circuits parametrization fail to solve the problems ad finem or solve them with admissions. The paper presents experimental and analytical determinations of the asynchronous machine equivalent-circuit parameters: the experimental one based on the results of two measurements and the analytical one where the problem boils down to solving a system of nonlineal algebraic equations. The authors investigate the equivalent asynchronous machine input-resistance properties and adduce the dependence curvatures of the input-resistances on the slide. They present a symbolic model for analytical parameterization of the asynchronous machine equivalent-circuit that represents a system of nonlineal equations and requires one of the rotor-parameters arbitrary assignment. The article demonstrates that for the asynchronous machine equivalent-circuit experimental parameterization the measures are to be conducted of the stator-circuit voltage, current and active power with two different slides and arbitrary assignment of one of the rotor parameters. The paper substantiates the fact that additional measurement does not discard the rotor-parameter choice arbitrariness. The authors establish that in motoring mode there is a critical slide by which the

  13. Alternative multiple-access techniques for mobile satellite systems

    Science.gov (United States)

    Smith, Patrick O.; Geraniotis, Evaggelos

    1989-01-01

    The use of Code Division Multiple Access (CDMA) to satisfy the diverse requirements of a generic (land, maritime, aeronautical) mobile satellite system (MSS) network design is discussed. Comparisons between CDMA and Frequency Division Multiple Access (FDMA) show that a CDMA network design can support significantly more voice channel allocations than FDMA when relatively simple CDMA correlation receivers are employed, provided that there is sufficient space segment equivalent isotropically radiated power (EIRP). The use of more advanced CDMA receivers can improve the spectral and power efficiency. Although the use of CDMA may not gain immediate and widespread support in the international MSS community, provision for the use of CDMA for a domestic system in the U.S., and possibly for a regional system throughout North America, is likely.

  14. Comparison of systems of synchronous/asynchronous drive for electric cars; Systemvergleich Synchron-/Asynchronantrieb fuer Elektroautos

    Energy Technology Data Exchange (ETDEWEB)

    Greubel, K.; Brandes, J.

    1995-12-31

    Drives for electric vehicles will develop into a new growth market for electric motors if the policy outline conditions for keeping the air in inner cities clean are made more stringent. Therefore various motor principles are at present being examined for their suitability for electric cars in comparative studies. The requirements for the drive system are determined by the driving behaviour of the electric car and by the characteristic data of the energy store. Therefore, different drive solutions will succeed, depending on the type of vehicle and the battery concept. (orig.) [Deutsch] Antriebe fuer Elektrofahrzeuge werden sich fuer elektrische Motoren zu einem neuen Wachstumsmarkt entwickeln, wenn die politischen Rahmenbedingungen zur Reinhaltung der Luft in Innenstaedten verschaerft werden. Deshalb werden derzeit in vergleichenden Studien verschiedene Motorprinzipien auf ihre Eignung im Elektroauto untersucht. Die Anforderungen an das Antriebssystem werden durch das Fahrverhalten des Elektroautos und durch die Kenndaten des Energiespeichers bestimmt. Deshalb werden sich in Abhaengigkeit von Fahrzeugtyp und Batteriekonzept unterschiedliche Antriebsloesungen durchsetzen. (orig.)

  15. Two-Stage Maximum Likelihood Estimation (TSMLE for MT-CDMA Signals in the Indoor Environment

    Directory of Open Access Journals (Sweden)

    Sesay Abu B

    2004-01-01

    Full Text Available This paper proposes a two-stage maximum likelihood estimation (TSMLE technique suited for multitone code division multiple access (MT-CDMA system. Here, an analytical framework is presented in the indoor environment for determining the average bit error rate (BER of the system, over Rayleigh and Ricean fading channels. The analytical model is derived for quadrature phase shift keying (QPSK modulation technique by taking into account the number of tones, signal bandwidth (BW, bit rate, and transmission power. Numerical results are presented to validate the analysis, and to justify the approximations made therein. Moreover, these results are shown to agree completely with those obtained by simulation.

  16. Combined Effect of Random Transmit Power Control and Inter-Path Interference Cancellation on DS-CDMA Packet Mobile Communications

    Science.gov (United States)

    Kudoh, Eisuke; Ito, Haruki; Wang, Zhisen; Adachi, Fumiyuki

    In mobile communication systems, high speed packet data services are demanded. In the high speed data transmission, throughput degrades severely due to severe inter-path interference (IPI). Recently, we proposed a random transmit power control (TPC) to increase the uplink throughput of DS-CDMA packet mobile communications. In this paper, we apply IPI cancellation in addition to the random TPC. We derive the numerical expression of the received signal-to-interference plus noise power ratio (SINR) and introduce IPI cancellation factor. We also derive the numerical expression of system throughput when IPI is cancelled ideally to compare with the Monte Carlo numerically evaluated system throughput. Then we evaluate, by Monte-Carlo numerical computation method, the combined effect of random TPC and IPI cancellation on the uplink throughput of DS-CDMA packet mobile communications.

  17. Asynchronous Message Service Reference Implementation

    Science.gov (United States)

    Burleigh, Scott C.

    2011-01-01

    This software provides a library of middleware functions with a simple application programming interface, enabling implementation of distributed applications in conformance with the CCSDS AMS (Consultative Committee for Space Data Systems Asynchronous Message Service) specification. The AMS service, and its protocols, implement an architectural concept under which the modules of mission systems may be designed as if they were to operate in isolation, each one producing and consuming mission information without explicit awareness of which other modules are currently operating. Communication relationships among such modules are self-configuring; this tends to minimize complexity in the development and operations of modular data systems. A system built on this model is a society of generally autonomous, inter-operating modules that may fluctuate freely over time in response to changing mission objectives, modules functional upgrades, and recovery from individual module failure. The purpose of AMS, then, is to reduce mission cost and risk by providing standard, reusable infrastructure for the exchange of information among data system modules in a manner that is simple to use, highly automated, flexible, robust, scalable, and efficient. The implementation is designed to spawn multiple threads of AMS functionality under the control of an AMS application program. These threads enable all members of an AMS-based, distributed application to discover one another in real time, subscribe to messages on specific topics, and to publish messages on specific topics. The query/reply (client/server) communication model is also supported. Message exchange is optionally subject to encryption (to support confidentiality) and authorization. Fault tolerance measures in the discovery protocol minimize the likelihood of overall application failure due to any single operational error anywhere in the system. The multi-threaded design simplifies processing while enabling application nodes to

  18. Wind power systems in the MW range. Part 2. Digital control of a double-fed asynchronous generator without position control; Windkraftanlagen fuer den Megawatt-Bereich. Teil 2. Digitale Steuerung eines doppelt gespeisten Asynchrongenerators ohne Lagegeber

    Energy Technology Data Exchange (ETDEWEB)

    Ehrenberg, J. [sci-worx GmbH, Braunschweig (Germany); Andresen, B.; Rebsdorf, A.V. [Vestas Wind Systems A/S (Denmark)

    2001-09-18

    While the first part investigated the characteristics of synchronous and asynchronous generators for wind power system development and presented theoretical fundamentals, part 2 discusses practical problems of synchronisation with the network and interpretation of measurements as illustrated by a prototype 2 MW wind power plant. [German] Nach einem Vergleich der Eignung von Synchron- und Asynchrongeneratoren fuer die Konzeption von Windkraftanlagen und einer Darstellung der Theoretischen Grundlagen im Teil 1 widmet sich der zweite Teil des Beitrages den praktischen Fragen der Synchronisation zum Netz und der Interpretation der Messergebnisse an dem Prototyp einer 2-MW-Windkraftanlage. (org.)

  19. OFDM and MC-CDMA for broadband multi-user communications WLANs and broadcasting

    CERN Document Server

    2003-01-01

    "OFDM systems have experienced increased attention in recent years and have found applications in a number of diverse areas including telephone-line based ADSL links, digital audio and video broadcasting systems, and wireless local area networks. OFDM is being considered for the next-generation of wireless systems both with and without direct sequence spreading and the resultant spreading-based multi-carrier CDMA systems have numerous attractive properties. This volume provides the reader with a broad overview of the research on OFDM systems during their 40-year history. Part I commences with an easy to read conceptual, rather than mathematical, treatment of the basic design issues of OFDM systems. The discussions gradually deepen to include adaptive single and multi-user OFDM systems invoking adaptive turbo coding. Part II introduces the taxonomy of multi-carrier CDMA systems and deals with the design of their spreading codes and the objective of minimising their crest factors. This part also compares the be...

  20. Mutual Interference Models for CDMA Mobile Communication Networks

    Directory of Open Access Journals (Sweden)

    K. Hrudkay

    2002-12-01

    Full Text Available Nowadays we are witnesses of a huge development one of the mostprogressive communication technology - mobile networks. The mainproblem in these networks is an elimination of the mutual interference,which, mainly in non-orthogonal CDMA networks, is the principalobstacle for reaching high transmission rates The aim of thiscontribution is to give simplified view to mutual interference modelsfor orthogonal and non-orthogonal CDMA networks. The contribution isintended mainly for PhD. students to help them to obtain an orientationin such a complicated areas, as the interference models for CDMAnetworks are.

  1. Simple nonlinear interferometer-based all-optical thresholder and its applications for optical CDMA.

    Science.gov (United States)

    Kravtsov, Konstantin; Prucnal, Paul R; Bubnov, Mikhail M

    2007-10-01

    We present an experimental demonstration of an ultrafast all-optical thresholder based on a nonlinear Sagnac interferometer. The proposed design is intended for operation at very small nonlinear phase shifts. Therefore, it requires an in-loop nonlinearity lower than for the classical nonlinear loop mirror scheme. Only 15 meters of conventional (non-holey) silica-based fiber is used as a nonlinear element. The proposed thresholder is polarization insensitive and is good for multi-wavelength operation, meeting all the requirements for autocorrelation detection in various optical CDMA communication systems. The observed cubic transfer function is superior to the quadratic transfer function of second harmonic generation-based thresholders.

  2. Ultrasonic array for obstacle detection based on CDMA with Kasami codes.

    Science.gov (United States)

    Diego, Cristina; Hernández, Alvaro; Jiménez, Ana; Alvarez, Fernando J; Sanz, Rebeca; Aparicio, Joaquín

    2011-01-01

    This paper raises the design of an ultrasonic array for obstacle detection based on Phased Array (PA) techniques, which steers the acoustic beam through the environment by electronics rather than mechanical means. The transmission of every element in the array has been encoded, according to Code Division for Multiple Access (CDMA), which allows multiple beams to be transmitted simultaneously. All these features together enable a parallel scanning system which does not only improve the image rate but also achieves longer inspection distances in comparison with conventional PA techniques.

  3. Improving Multi Access Interference Suppression in Optical CDMA by using all-Optical Signal Processing

    Directory of Open Access Journals (Sweden)

    T. B. Osadola

    2013-06-01

    Full Text Available This paper presents the study of a novel all-optical method for processing optical CDMA signals towards improving suppression of multi access interference. The main focus is on incoherent OCDMA systems using multiwavelength 2D-WH/TS codes generated using FBG based encoders and decoders. The MAI suppression capabilities based on its ability to eliminate selective wavelength pulse processing have been shown. A novel transmitter architecture that achieves up to 3dB power saving was also presented. As a result of hardware savings, processing cost will be significantly reduced and power budget improvement resulted in improved performance.

  4. A Binary Array Asynchronous Sorting Algorithm with Using Petri Nets

    Science.gov (United States)

    Voevoda, A. A.; Romannikov, D. O.

    2017-01-01

    Nowadays the tasks of computations speed-up and/or their optimization are actual. Among the approaches on how to solve these tasks, a method applying approaches of parallelization and asynchronization to a sorting algorithm is considered in the paper. The sorting methods are ones of elementary methods and they are used in a huge amount of different applications. In the paper, we offer a method of an array sorting that based on a division into a set of independent adjacent pairs of numbers and their parallel and asynchronous comparison. And this one distinguishes the offered method from the traditional sorting algorithms (like quick sorting, merge sorting, insertion sorting and others). The algorithm is implemented with the use of Petri nets, like the most suitable tool for an asynchronous systems description.

  5. Asynchronous machines. Direct torque control; Machines asynchrones. Commande par controle direct de couple

    Energy Technology Data Exchange (ETDEWEB)

    Fornel, B. de [Institut National Polytechnique, 31 - Toulouse (France)

    2006-05-15

    The asynchronous machine, with its low cost and robustness, is today the most widely used motor to make speed variators. However, its main drawback is that the same current generates both the magnetic flux and the torque, and thus any torque variation creates a flux variation. Such a coupling gives to the asynchronous machine a nonlinear behaviour which makes its control much more complex. The direct self control (DSC) method has been developed to improve the low efficiency of the scalar control method and for the specific railway drive application. The direct torque control (DTC) method is derived from the DSC method but corresponds to other type of applications. The DSC and DTC algorithms for asynchronous motors are presented in this article: 1 - direct control of the stator flux (DSC): principle, flux control, torque control, switching frequency of the inverter, speed estimation; 2 - direct torque control (DTC): principle, electromagnetic torque derivative, signals shape and switching frequency, some results, DTC speed variator without speed sensor, DTC application to multi-machine multi-converter systems; 3 - conclusion. (J.S.)

  6. DESIGN METHODOLOGY OF SELF-EXCITED ASYNCHRONOUS GENERATOR

    Directory of Open Access Journals (Sweden)

    Berzan V.

    2012-04-01

    Full Text Available The paper sets out the methodology of designing an asynchronous generator with capacitive self-excitation. It is known that its design is possible on the basis of serial synchronous motor with squirrel cage rotor. With this approach, the design reworked only the stator winding of electrical machines, making it cost-effectively implement the creation of the generator. Therefore, the methodology for the design, optimization calculations, the development scheme and the stator winding excitation system gain, not only of practical interest, and may also be useful for specialists in the field of electrical machines in the design of asynchronous generators.

  7. Effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic field on immune functions in rats.

    Science.gov (United States)

    Jin, Yeung Bae; Pyun, Bo-Jeong; Jin, Hee; Choi, Hyung-Do; Pack, Jeong-Ki; Kim, Nam; Lee, Yun-Sil

    2012-11-01

    Despite the importance of the immune system in defending the body against infection and cancer, little research on the possible effects of radiofrequency electromagnetic field (RF-EMF) signals on immune functions exists, and, in the case of simultaneous combined exposure of RF-EMF, to the best of our knowledge no work has been done. The aim of this study was to assess the effect of simultaneous exposure to two types of RF-EMF signals, single code division multiple access (CDMA) and wideband code division multiple access (WCDMA) signals on the immune system of rats. Male Sprague-Dawley rats were exposed to RF-EMF for 45 min/day, 5 days/week for up to 8 weeks. The whole body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg. Every 2 weeks after the experiment began, 20 rats were autopsied. Blood hematology, subtype population of splenocytes and cytokine production or mRNA expressions, interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-1β, interferon (IFN)-γ and transforming growth factor (TGF)-β from the splenocytes or IL-6, TNF-α, and immunoglobulin (Ig) of IgG and IgM from blood serum, were examined. The results suggest that 8-week exposure to CDMA (849 MHz) and WCDMA (1.95 GHz) RF simultaneously at 2.0 W/kg each for 45-min RF-EMF exposure (total, 4 W/kg) did not affect these immune parameters. The present experiments suggest that simultaneous combined exposure of CDMA and WCDMA with total SAR dose of 4.0 W/kg for 45 min/day for 8 weeks, which is a relatively high SAR level compared to the exposure levels for the human system recommended by International Commission on Non-Ionizing Radiation Protection (ICNIRP, 0.4W/kg for whole body exposure levels and 2.0 W/kg for local exposure levels of general public), did not have any detectable effects on immune function in rats.

  8. Downlink power control in multi-code CDMA for mobile medicine.

    Science.gov (United States)

    Lin, Chin-Feng; Chang, Wen-Thong; Lee, Hsin-Wang; Hung, Shih-Ii

    2006-05-01

    In this paper, we propose a downlink power-control mechanism to be applied in a multi-code code division multiple access (CDMA) mobile medicine system. The mobile medicine system can provide (i) measured blood pressure and body temperature, (ii) medical signals measured by the electrocardiogram (ECG) device, (iii) mobile patient's history, (iv) G.729 audio signals, (v) Joint Photographic Experts Group 2000 Medical images and Moving Picture Experts Group 4 charge-coupled device sensor video signals. By utilizing a multi-code CDMA spread spectrum communication system with downlink power-control strategy, it is possible for this system to meet the quality of service requirements of a mobile medicine network. In addition, such a system can maximize the resource utilization. For different messages to be sent, the power is controlled according to the requisite bit error rate (BER). Higher transmission power is given to the media with lower BER requirement. Numerical analysis shows that the ratios of transmission power for voice, video, and data virtual channels is approximately 1:2:13 when the BERs for voice, video, and data are 10(wedge)(- 3), 10(wedge)(- 4), and 10(wedge)(- 7), respectively. This power ratio is similar to the ratio of signal-to-noise plus interference power ratio for voice, video, and data during transmission. For the purpose of verifying the proposed argument, a simulation has been done and the results match the derivation very well.

  9. Analysis of Jammer Resistant, Spread Spectrum, VSAT Communication Scheme for Maritime Platform Using DS-CDMA

    Science.gov (United States)

    Aras, Ersin

    2002-09-01

    In this thesis, a new VSAT (Very Small Aperture Terminal) Communication system is developed using Direct Sequence Code Division Multiple Access (DS-CDMA) for multiple maritime mobile users in the footprints of national communication satellites. The Forward Error Correction (FEC) is implemented by applying convolution encoding with soft decision decoding. The worst case scenario is always considered by placing VSAT system and different types of jammers on the footprint where the minimum signal- to-noise ratio is possible. Using this assumption, the performance of the system is analyzed for different convolution code rates, for a different number of users and for the different jammer powers. The Walsh codes are used to establish an orthogonal cover between CDMA channels in a VSAT. Additionally, spread spectrum is included by PN sequences to ensure as much orthogonal coverage as possible between the VSATs. Also, that spreading is the key to minimizing these hostile jammers effects. After analyzing VSAT system for possible scenario elements, optimum system parameters are introduced for military and civilian applications.

  10. Effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic fields on serum hormone levels in rats.

    Science.gov (United States)

    Jin, Yeung Bae; Choi, Hyung-Do; Kim, Byung Chan; Pack, Jeong-Ki; Kim, Nam; Lee, Yun-Sil

    2013-05-01

    Despite more than a decade of research on the endocrine system, there have been no published studies about the effects of concurrent exposure of radiofrequency electromagnetic fields (RF-EMF) on this system. The present study investigated the several parameters of the endocrine system including melatonin, thyroid stimulating hormone, stress hormone and sex hormone after code division multiple access (CDMA, 849 MHz) and wideband code division multiple access (WCDMA, 1.95 GHz) signals for simultaneous exposure in rats. Sprague-Dawley rats were exposed to RF-EMF signals for 45 min/day, 5 days/week for up to 8 weeks. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg (total 4.0 W/kg). At 4 and 8 weeks after the experiment began, each experimental group's 40 rats (male 20, female 20) were autopsied. Exposure for 8 weeks to simultaneous CDMA and WCDMA RF did not affect serum levels in rats of melatonin, thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxin (T4), adrenocorticotropic hormone (ACTH) and sex hormones (testosterone and estrogen) as assessed by the ELISA method.

  11. Developing asynchronous online interprofessional education.

    Science.gov (United States)

    Sanborn, Heidi

    2016-09-01

    For many health programmes, developing interprofessional education (IPE) has been a challenge. Evidence on the best method for design and implementation of IPE has been slow to emerge, with little research on how to best incorporate IPE in the asynchronous online learning environment. This leaves online programmes with no clear guidance when embarking upon an initiative to integrate IPE into the curriculum. One tool that can be effective at guiding the incorporation of IPE across all learning platforms is the Interprofessional Education Collaborative (IPEC) competencies. A project was designed to integrate the nationally defined IPEC competencies throughout an asynchronous, online baccalaureate nursing completion programme. A programme-wide review led to targeted revision of course and unit-level objectives, learning experiences, and assessments based on the IPEC framework. As a result of this effort, the programme curriculum now provides interprofessional learning activities across all courses. This report provides a method for using the IPEC competencies to incorporate IPE within various asynchronous learning assessments, assuring students learn about, with, and from other professions.

  12. GLONASS CDMA L3 ambiguity resolution and positioning

    NARCIS (Netherlands)

    Zaminpardaz, Safoora; Teunissen, P.J.G.; Nadarajah, Nandakumaran

    2016-01-01

    A first assessment of GLONASS CDMA L3 ambiguity resolution and positioning performance is provided. Our analyses are based on GLONASS L3 data from the satellite pair SVNs 755-801, received by two JAVAD receivers at Curtin University, Perth, Australia. In our analyses, four different versions of

  13. Selective particle capture by asynchronously beating cilia

    Science.gov (United States)

    Ding, Yang; Kanso, Eva

    2015-12-01

    Selective particle filtration is fundamental in many engineering and biological systems. For example, many aquatic microorganisms use filter feeding to capture food particles from the surrounding fluid, using motile cilia. One of the capture strategies is to use the same cilia to generate feeding currents and to intercept particles when the particles are on the downstream side of the cilia. Here, we develop a 3D computational model of ciliary bands interacting with flow suspended particles and calculate particle trajectories for a range of particle sizes. Consistent with experimental observations, we find optimal particle sizes that maximize capture rate. The optimal size depends nonlinearly on cilia spacing and cilia coordination, synchronous vs. asynchronous. These parameters affect the cilia-generated flow field, which in turn affects particle trajectories. The low capture rate of smaller particles is due to the particles' inability to cross the flow streamlines of neighboring cilia. Meanwhile, large particles have difficulty entering the sub-ciliary region once advected downstream, also resulting in low capture rates. The optimal range of particle sizes is enhanced when cilia beat asynchronously. These findings have potentially important implications on the design and use of biomimetic cilia in processes such as particle sorting in microfluidic devices.

  14. Phase Space Invertible Asynchronous Cellular Automata

    Directory of Open Access Journals (Sweden)

    Simon Wacker

    2012-08-01

    Full Text Available While for synchronous deterministic cellular automata there is an accepted definition of reversibility, the situation is less clear for asynchronous cellular automata. We first discuss a few possibilities and then investigate what we call phase space invertible asynchronous cellular automata in more detail. We will show that for each Turing machine there is such a cellular automaton simulating it, and that it is decidable whether an asynchronous cellular automaton has this property or not, even in higher dimensions.

  15. Demonstration of the CDMA-mode CAOS smart camera.

    Science.gov (United States)

    Riza, Nabeel A; Mazhar, Mohsin A

    2017-12-11

    Demonstrated is the code division multiple access (CDMA)-mode coded access optical sensor (CAOS) smart camera suited for bright target scenarios. Deploying a silicon CMOS sensor and a silicon point detector within a digital micro-mirror device (DMD)-based spatially isolating hybrid camera design, this smart imager first engages the DMD starring mode with a controlled factor of 200 high optical attenuation of the scene irradiance to provide a classic unsaturated CMOS sensor-based image for target intelligence gathering. Next, this CMOS sensor provided image data is used to acquire a focused zone more robust un-attenuated true target image using the time-modulated CDMA-mode of the CAOS camera. Using four different bright light test target scenes, successfully demonstrated is a proof-of-concept visible band CAOS smart camera operating in the CDMA-mode using up-to 4096 bits length Walsh design CAOS pixel codes with a maximum 10 KHz code bit rate giving a 0.4096 seconds CAOS frame acquisition time. A 16-bit analog-to-digital converter (ADC) with time domain correlation digital signal processing (DSP) generates the CDMA-mode images with a 3600 CAOS pixel count and a best spatial resolution of one micro-mirror square pixel size of 13.68 μm side. The CDMA-mode of the CAOS smart camera is suited for applications where robust high dynamic range (DR) imaging is needed for un-attenuated un-spoiled bright light spectrally diverse targets.

  16. Blind Adaptive Decorrelating RAKE (DRAKE Downlink Receiver for Space-Time Block Coded Multipath CDMA

    Directory of Open Access Journals (Sweden)

    Jayaweera Sudharman K

    2002-01-01

    Full Text Available A downlink receiver is proposed for space-time block coded CDMA systems operating in multipath channels. By combining the powerful RAKE receiver concept for a frequency selective channel with space-time decoding, it is shown that the performance of mobile receivers operating in the presence of channel fading can be improved significantly. The proposed receiver consists of a bank of decorrelating filters designed to suppress the multiple access interference embedded in the received signal before the space-time decoding. The new receiver performs the space-time decoding along each resolvable multipath component and then the outputs are diversity combined to obtain the final decision statistic. The proposed receiver relies on a key constraint imposed on the output of each filter in the bank of decorrelating filters in order to maintain the space-time block code structure embedded in the signal. The proposed receiver can easily be adapted blindly, requiring only the desired user′s signature sequence, which is also attractive in the context of wireless mobile communications. Simulation results are provided to confirm the effectiveness of the proposed receiver in multipath CDMA systems.

  17. Methodology and Implementation on DSP of Heuristic Multiuser DS/CDMA Detectors

    Directory of Open Access Journals (Sweden)

    Alex Miyamoto Mussi

    2010-12-01

    Full Text Available The growing number of users of mobile communications networks and the scarcity of the electromagnetic spectrum make the use of diversity techniques and detection/decoding efficient, such as the use of multiple antennas at the transmitter and/or receiver, multiuser detection (MuD – Multiuser Detection, among others, have an increasingly prominent role in the telecommunications landscape. This paper presents a design methodology based on digital signal processors (DSP – Digital Signal Processor with a view to the implementation of multiuser heuristics detectors in systems DS/CDMA (Direct Sequence Code Division Multiple Access. Heuristics detection techniques result in near-optimal performance in order to approach the performance of maximum-likelihood (ML. In this work, was employed the DSP development platform called the C6713 DSK, which is based in Texas TMS320C6713 processor. The heuristics techniques proposed are based on well established algorithms in the literature. The efficiency of the algorithms implemented in DSP has been evaluated numerically by computing the measure of bit error rate (BER. Finally, the feasibility of implementation in DSP could then be verified by comparing results from multiple Monte-Carlo simulation in Matlab, with those obtained from implementation on DSP. It also demonstrates the effective increase in performance and system capacity of DS/CDMA with the use of heuristic multiuser detection techniques, implemented directly in the DSP.

  18. Average Likelihood Methods of Classification of Code Division Multiple Access (CDMA)

    Science.gov (United States)

    2016-05-01

    AVERAGE LIKELIHOOD METHODS OF CLASSIFICATION OF CODE DIVISION MULTIPLE ACCESS ( CDMA ) MAY 2016 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE...ACCESS ( CDMA ) 5a. CONTRACT NUMBER IN-HOUSE / R193 5b. GRANT NUMBER N/A 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Alfredo Vega Irizarry 5d...ABSTRACT This final report summarizes the most significant findings under the in-house effort titled “Average Likelihood For CDMA ”. The effort included

  19. ZTE Becomes Global Leader in CDMA Base Station Market with 33% Share

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    ZTE Corporation announced on November 3, 2011 that it has become the global leader in the CDMA base station market, with a 32.6 percent share in first half 2011. According to a recent IDC analytical report on the global CDMA market, ZTE has increased its shipments of CDMA base stations steadily in recent years. As of the end of first half of 2011, the company's shipment of base-stations had exceeded 320 thousand units, pushing it to the top spot in the global CDMA base station market.

  20. Effects of 1950 MHz W-CDMA-like signal on human spermatozoa.

    Science.gov (United States)

    Nakatani-Enomoto, Setsu; Okutsu, Miho; Suzuki, Satoshi; Suganuma, Ryota; Groiss, Stefan Jun; Kadowaki, Suguru; Enomoto, Hiroyuki; Fujimori, Keiya; Ugawa, Yoshikazu

    2016-09-01

    There are growing concerns about how electromagnetic waves (EMW) emitted from mobile phones affect human spermatozoa. Several experiments have suggested harmful effects of EMW on human sperm quality, motility, velocity, or the deoxyribonucleic acid (DNA) of spermatozoa. In this study, we analyzed the effects on human spermatozoa (sperm motility and kinetic variables) induced by 1 h of exposure to 1950 MHz Wideband Code Division Multiple Access (W-CDMA)-like EMW with specific absorption rates of either 2.0 or 6.0 W/kg, using a computer-assisted sperm analyzer system. We also measured the percentage of 8-hydroxy-2'-deoxyguanosine (8-OHdG) positive spermatozoa with flow cytometry to evaluate damage to DNA. No significant differences were observed between the EMW exposure and the sham exposure in sperm motility, kinetic variables, or 8-OHdG levels. We conclude that W-CDMA-like exposure for 1 h under temperature-controlled conditions has no detectable effect on normal human spermatozoa. Differences in exposure conditions, humidity, temperature control, baseline sperm characteristics, and age of donors may explain inconsistency of our results with several previous studies. Bioelectromagnetics. 37:373-381, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  1. DS-CDMA satellite diversity reception for personal satellite communication: Downlink performance analysis

    Science.gov (United States)

    DeGaudenzi, Riccardo; Giannetti, Filippo

    1995-01-01

    The downlink of a satellite-mobile personal communication system employing power-controlled Direct Sequence Code Division Multiple Access (DS-CDMA) and exploiting satellite-diversity is analyzed and its performance compared with a more traditional communication system utilizing single satellite reception. The analytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. It is shown how the capacity gain provided by diversity reception shrinks considerably in the presence of increasing traffic or in the case of light shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to intra-system interference, no more than two satellites shall be active over the same region. To achieve higher system capacity, differently from terrestrial cellular systems, Multi-User Detection (MUD) techniques are likely to be required in the mobile user terminal, thus considerably increasing its complexity.

  2. Asynchronous Parallelization of a CFD Solver

    Directory of Open Access Journals (Sweden)

    Daniel S. Abdi

    2015-01-01

    Full Text Available A Navier-Stokes equations solver is parallelized to run on a cluster of computers using the domain decomposition method. Two approaches of communication and computation are investigated, namely, synchronous and asynchronous methods. Asynchronous communication between subdomains is not commonly used in CFD codes; however, it has a potential to alleviate scaling bottlenecks incurred due to processors having to wait for each other at designated synchronization points. A common way to avoid this idle time is to overlap asynchronous communication with computation. For this to work, however, there must be something useful and independent a processor can do while waiting for messages to arrive. We investigate an alternative approach of computation, namely, conducting asynchronous iterations to improve local subdomain solution while communication is in progress. An in-house CFD code is parallelized using message passing interface (MPI, and scalability tests are conducted that suggest asynchronous iterations are a viable way of parallelizing CFD code.

  3. Asynchronous Sensor fuSion for Improved Safety of air Traffic (ASSIST) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — SSCI proposes to develop, implement and test a collision detection system for unmanned aerial vehicles (UAV), referred to as the Asynchronous Sensor fuSion for...

  4. Asynchronous parallel pattern search for nonlinear optimization

    Energy Technology Data Exchange (ETDEWEB)

    P. D. Hough; T. G. Kolda; V. J. Torczon

    2000-01-01

    Parallel pattern search (PPS) can be quite useful for engineering optimization problems characterized by a small number of variables (say 10--50) and by expensive objective function evaluations such as complex simulations that take from minutes to hours to run. However, PPS, which was originally designed for execution on homogeneous and tightly-coupled parallel machine, is not well suited to the more heterogeneous, loosely-coupled, and even fault-prone parallel systems available today. Specifically, PPS is hindered by synchronization penalties and cannot recover in the event of a failure. The authors introduce a new asynchronous and fault tolerant parallel pattern search (AAPS) method and demonstrate its effectiveness on both simple test problems as well as some engineering optimization problems

  5. Cdma blind channel equalization: a weighted subsface a proach

    OpenAIRE

    Ruiz Feliu, Rafael; Cabrera Beán, Margarita Asuncion

    1999-01-01

    This paper considers the problem of blind demodulation of multiuser information symbols in a direct-sequence code-division multiple access (DS-CDMA) environment. Channel estimation and symbol detection in the presence of both multiple access interference (MAI) and intersymbol interference (ISI) is carried out with second order statistics methods from the received data. This problem is similar to direction of arrival (DOA) estimation, where many solutions like the MUSIC algorithm or Peer Re...

  6. Enhancing Discussions in the Asynchronous Online Classroom: The Lack of Face-to-Face Interaction Does Not Lessen the Lesson

    Science.gov (United States)

    Comer, Debra R.; Lenaghan, Janet A.

    2013-01-01

    This article addresses educators' concerns about using asynchronous online discussions in lieu of face-to-face discussions. Drawing from research on asynchronous online education and Bloom's taxonomy, the authors introduce the system of "original examples" and "value-added comments" that they have developed to promote engaging and meaningful…

  7. Performance analysis for a QoS-aware hybrid token-CDMA MAC protocol

    CSIR Research Space (South Africa)

    Liu, YS

    2007-09-01

    Full Text Available This paper presents the performance analysis of a hybrid Token-CDMA MAC protocol. The protocol is based on a token passing scheme with the incorporation of code division multiple access (CDMA). The protocol provides both QoS guarantee and high...

  8. Burst-Mode Asynchronous Controllers on FPGA

    Directory of Open Access Journals (Sweden)

    Duarte L. Oliveira

    2008-01-01

    Full Text Available FPGAs have been mainly used to design synchronous circuits. Asynchronous design on FPGAs is difficult because the resulting circuit may suffer from hazard problems. We propose a method that implements a popular class of asynchronous circuits, known as burst mode, on FPGAs based on look-up table architectures. We present two conditions that, if satisfied, guarantee essential hazard-free implementation on any LUT-based FPGA. By doing that, besides all the intrinsic advantages of asynchronous over synchronous circuits, they also take advantage of the shorter design time and lower cost associated with FPGA designs.

  9. Violation of the equivalence principle for stressed bodies in asynchronous relativity

    Energy Technology Data Exchange (ETDEWEB)

    Andrade Martins, R. de (Centro de Logica, Epistemologia e Historia da Ciencia, Campinas (Brazil))

    1983-12-11

    In the recently developed asynchronous formulation of the relativistic theory of extended bodies, the inertial mass of a body does not explicitly depend on its pressure or stress. The detailed analysis of the weight of a box filled with a gas and placed in a weak gravitational field shows that this feature of asynchronous relativity implies a breakdown of the equivalence between inertial and passive gravitational mass for stressed systems.

  10. Performance analysis of a handoff scheme for two-tier cellular CDMA networks

    Directory of Open Access Journals (Sweden)

    Ahmed Hamad

    2011-07-01

    Full Text Available A two-tier model is used in cellular networks to improve the Quality of Service (QoS, namely to reduce the blocking probability of new calls and the forced termination probability of ongoing calls. One tier, the microcells, is used for slow or stationary users, and the other, the macrocell, is used for high speed users. In Code-Division Multiple-Access (CDMA cellular systems, soft handoffs are supported, which provides ways for further QoS improvement. In this paper, we introduce such a way; namely, a channel borrowing scheme used in conjunction with a First-In-First-Out (FIFO queue in the macrocell tier. A multidimensional Markov chain to model the resulting system is established, and an iterative technique to find the steady-state probability distribution is utilized. This distribution is then used to find the performance measures of interest: new call blocking probability, and forced termination probability.

  11. Downlink Multihop Transmission Technique for Asymmetric Traffic Accommodation in DS-CDMA/FDD Cellular Communications

    Science.gov (United States)

    Mori, Kazuo; Naito, Katsuhiro; Kobayashi, Hideo

    This paper proposes an asymmetric traffic accommodation scheme using a multihop transmission technique for CDMA/FDD cellular communication systems. The proposed scheme exploits the multihop transmission to downlink packet transmissions, which require the large transmission power at their single-hop transmissions, in order to increase the downlink capacity. In these multihop transmissions, vacant uplink band is used for the transmissions from relay stations to destination mobile stations, and this leads more capacity enhancement in the downlink communications. The relay route selection method and power control method for the multihop transmissions are also investigated in the proposed scheme. The proposed scheme is evaluated by computer simulation and the results show that the proposed scheme can achieve better system performance.

  12. IDENTIFICATION AND CONTROL OF AN ASYNCHRONOUS MACHINE USING NEURAL NETWORKS

    Directory of Open Access Journals (Sweden)

    A ZERGAOUI

    2000-06-01

    Full Text Available In this work, we present the application of artificial neural networks to the identification and control of the asynchronous motor, which is a complex nonlinear system with variable internal dynamics.  We show that neural networks can be applied to control the stator currents of the induction motor.  The results of the different simulations are presented to evaluate the performance of the neural controller proposed.

  13. Separación ciega de fuentes y su aplicación a receptores de comunicaciones digitales: CDMA, OFDM y MC-CDMA

    OpenAIRE

    Boloix Tortosa, Rafael

    2005-01-01

    La Tesis está dividida en dos partes. En la primera parte se realiza un estudio de las técnicas de separación ciega de fuentes (BSS), mientras que en la segunda se estudia la aplicación de tales técnicas a los sistemas de comunicaciones digitales, en concreto a CDMA, OFDM, y MC-CDMA.

  14. Equalization of Multiuser Wireless CDMA Downlink Considering Transmitter Nonlinearity Using Walsh Codes

    Directory of Open Access Journals (Sweden)

    Stephen Z. Pinter

    2007-02-01

    Full Text Available Transmitter nonlinearity has been a major issue in many scenarios: cellular wireless systems have high power RF amplifier (HPA nonlinearity at the base station; satellite downlinks have nonlinear TWT amplifiers in the satellite transponder and multipath conditions in the ground station; and radio-over-fiber (ROF systems consist of a nonlinear optical link followed by a wireless channel. In many cases, the nonlinearity is simply ignored if there is no out-of-band emission. This results in poor BER performance. In this paper we propose a new technique to estimate the linear part of the wireless downlink in the presence of a nonlinearity using Walsh codes; Walsh codes are commonly used in CDMA downlinks. Furthermore, we show that equalizer performance is significantly improved by taking into account the presence of the nonlinearity during channel estimation. This is shown by using a regular decision feedback equalizer (DFE with both wireless and RF amplifier noise. We perform estimation in a multiuser CDMA communication system where all users transmit their signal simultaneously. Correlation analysis is applied to identify the channel impulse response (CIR and the derivation of key correlation relationships is shown. A difficulty with using Walsh codes in terms of their correlations (compared to PN sequences is then presented, as well as a discussion on how to overcome it. Numerical evaluations show a good estimation of the linear system with 54 users in the downlink and a signal-to-noise ratio (SNR of 25 dB. Bit error rate (BER simulations of the proposed identification and equalization algorithms show a BER of 10−6 achieved at an SNR of ∼25 dB.

  15. Equalization of Multiuser Wireless CDMA Downlink Considering Transmitter Nonlinearity Using Walsh Codes

    Directory of Open Access Journals (Sweden)

    Pinter Stephen Z

    2007-01-01

    Full Text Available Transmitter nonlinearity has been a major issue in many scenarios: cellular wireless systems have high power RF amplifier (HPA nonlinearity at the base station; satellite downlinks have nonlinear TWT amplifiers in the satellite transponder and multipath conditions in the ground station; and radio-over-fiber (ROF systems consist of a nonlinear optical link followed by a wireless channel. In many cases, the nonlinearity is simply ignored if there is no out-of-band emission. This results in poor BER performance. In this paper we propose a new technique to estimate the linear part of the wireless downlink in the presence of a nonlinearity using Walsh codes; Walsh codes are commonly used in CDMA downlinks. Furthermore, we show that equalizer performance is significantly improved by taking into account the presence of the nonlinearity during channel estimation. This is shown by using a regular decision feedback equalizer (DFE with both wireless and RF amplifier noise. We perform estimation in a multiuser CDMA communication system where all users transmit their signal simultaneously. Correlation analysis is applied to identify the channel impulse response (CIR and the derivation of key correlation relationships is shown. A difficulty with using Walsh codes in terms of their correlations (compared to PN sequences is then presented, as well as a discussion on how to overcome it. Numerical evaluations show a good estimation of the linear system with 54 users in the downlink and a signal-to-noise ratio (SNR of 25 dB. Bit error rate (BER simulations of the proposed identification and equalization algorithms show a BER of achieved at an SNR of dB.

  16. Dynamic modeling of an asynchronous squirrel-cage machine; Modelisation dynamique d'une machine asynchrone a cage

    Energy Technology Data Exchange (ETDEWEB)

    Guerette, D.

    2009-07-01

    This document presented a detailed mathematical explanation and validation of the steps leading to the development of an asynchronous squirrel-cage machine. The MatLab/Simulink software was used to model a wind turbine at variable high speeds. The asynchronous squirrel-cage machine is an electromechanical system coupled to a magnetic circuit. The resulting electromagnetic circuit can be represented as a set of resistances, leakage inductances and mutual inductances. Different models were used for a comparison study, including the Munteanu, Boldea, Wind Turbine Blockset, and SimPowerSystem. MatLab/Simulink modeling results were in good agreement with the results from other comparable models. Simulation results were in good agreement with analytical calculations. 6 refs, 2 tabs, 9 figs.

  17. Interpolation algorithm for asynchronous ADC-data

    Science.gov (United States)

    Bramburger, Stefan; Zinke, Benny; Killat, Dirk

    2017-09-01

    This paper presents a modified interpolation algorithm for signals with variable data rate from asynchronous ADCs. The Adaptive weights Conjugate gradient Toeplitz matrix (ACT) algorithm is extended to operate with a continuous data stream. An additional preprocessing of data with constant and linear sections and a weighted overlap of step-by-step into spectral domain transformed signals improve the reconstruction of the asycnhronous ADC signal. The interpolation method can be used if asynchronous ADC data is fed into synchronous digital signal processing.

  18. Secure DS-CDMA spreading codes using fully digital multidimensional multiscroll chaos

    KAUST Repository

    Mansingka, Abhinav S.

    2014-06-18

    This paper introduces a generalized fully digital hardware implementation of 1-D, 2-D and 3-D multiscroll chaos through sawtooth nonlinearities in a 3rd order ODE with the Euler approximation, wherein low-significance bits pass all NIST SP. 800-22 tests. The low-significance bits show good performance as spreading code for multiple-access DS-CDMA in AWGN and multipath environments, equivalent to Gold codes. This system capitalizes on complex nonlinear dynamics afforded by multiscroll chaos to provide higher security than conventional codes with the same BER performance demonstrated experimentally on a Xilinx Virtex 4 FPGA with logic utilization less than 1.25% and throughput up to 10.92 Gbits/s.

  19. A MUSIC-Based Algorithm for Blind User Identification in Multiuser DS-CDMA

    Directory of Open Access Journals (Sweden)

    M. Reza Soleymani

    2005-04-01

    Full Text Available A blind scheme based on multiple-signal classification (MUSIC algorithm for user identification in a synchronous multiuser code-division multiple-access (CDMA system is suggested. The scheme is blind in the sense that it does not require prior knowledge of the spreading codes. Spreading codes and users' power are acquired by the scheme. Eigenvalue decomposition (EVD is performed on the received signal, and then all the valid possible signature sequences are projected onto the subspaces. However, as a result of this process, some false solutions are also produced and the ambiguity seems unresolvable. Our approach is to apply a transformation derived from the results of the subspace decomposition on the received signal and then to inspect their statistics. It is shown that the second-order statistics of the transformed signal provides a reliable means for removing the false solutions.

  20. Wireless Networks with Asynchronous Users

    CERN Document Server

    Moshksar, Kamyar

    2010-01-01

    This paper addresses an interference channel consisting of $\\mathbf{n}$ active users sharing $u$ frequency sub-bands. Users are asynchronous meaning there exists a mutual delay between their transmitted codes. A stationary model for interference is considered by assuming the starting point of an interferer's data is uniformly distributed along the codeword of any user. This model is not ergodic, however, we show that the noise plus interference process satisfies an Asymptotic Equipartition Property (AEP) under certain conditions. This enables us to define achievable rates in the conventional Shannon sense. The spectrum is divided to private and common bands. Each user occupies its assigned private band and the common band upon activation. In a scenario where all transmitters are unaware of the number of active users and the channel gains, the optimum spectrum assignment is obtained such that the so-called outage capacity per user is maximized. If $\\Pr\\{\\mathbf{n}>2\\}>0$, all users follow a locally Randomized ...

  1. Reduced-Rank Chip-Level MMSE Equalization for the 3G CDMA Forward Link with Code-Multiplexed Pilot

    Directory of Open Access Journals (Sweden)

    Goldstein J Scott

    2002-01-01

    Full Text Available This paper deals with synchronous direct-sequence code-division multiple access (CDMA transmission using orthogonal channel codes in frequency selective multipath, motivated by the forward link in 3G CDMA systems. The chip-level minimum mean square error (MMSE estimate of the (multiuser synchronous sum signal transmitted by the base, followed by a correlate and sum, has been shown to perform very well in saturated systems compared to a Rake receiver. In this paper, we present the reduced-rank, chip-level MMSE estimation based on the multistage nested Wiener filter (MSNWF. We show that, for the case of a known channel, only a small number of stages of the MSNWF is needed to achieve near full-rank MSE performance over a practical single-to-noise ratio (SNR range. This holds true even for an edge-of-cell scenario, where two base stations are contributing near equal-power signals, as well as for the single base station case. We then utilize the code-multiplexed pilot channel to train the MSNWF coefficients and show that adaptive MSNWF operating in a very low rank subspace performs slightly better than full-rank recursive least square (RLS and significantly better than least mean square (LMS. An important advantage of the MSNWF is that it can be implemented in a lattice structure, which involves significantly less computation than RLS. We also present structured MMSE equalizers that exploit the estimate of the multipath arrival times and the underlying channel structure to project the data vector onto a much lower dimensional subspace. Specifically, due to the sparseness of high-speed CDMA multipath channels, the channel vector lies in the subspace spanned by a small number of columns of the pulse shaping filter convolution matrix. We demonstrate that the performance of these structured low-rank equalizers is much superior to unstructured equalizers in terms of convergence speed and error rates.

  2. DEPLOYMENT OF ANTENNA ARRAY FOR DATA RETRIEVAL IN CDMA ENVIROMENT

    OpenAIRE

    RICARDO ZELENOVSKY

    2001-01-01

    Este trabalho de tese trata do emprego de arranjos de antenas em ambientes de comunicação móvel,dando-se ênfase ao canal de dados reverso do Sistema IS-95. Propõe-se dois estimadores: um para a direção de chegada dos sinais e outro para outros dados. Inicialmente é apresentado um estudo sobre arranjos de antenas e dos principais detalhes do sistema IS-95,especialmente a multiplicidade de acesso via divisão por códigos (CDMA).Aborda-se em seguida o problema d...

  3. Hypersensitivity to RF fields emitted from CDMA cellular phones: a provocation study.

    Science.gov (United States)

    Nam, Ki Chang; Lee, Ju Hyung; Noh, Hyung Wook; Cha, Eun Jong; Kim, Nam Hyun; Kim, Deok Won

    2009-12-01

    With the number of cellular phone users rapidly increasing, there is a considerable amount of public concern regarding the effects that electromagnetic fields (EMFs) from cellular phones have on health. People with self-attributed electromagnetic hypersensitivity (EHS) complain of subjective symptoms such as headaches, insomnia, and memory loss, and attribute these symptoms to radio frequency (RF) radiation from cellular phones and/or base stations. However, EHS is difficult to diagnose because it relies on a person's subjective judgment. Various provocation studies have been conducted on EHS caused by Global System for Mobile Communications (GSM) phones in which heart rate and blood pressure or subjective symptoms were investigated. However, there have been few sham-controlled provocation studies on EHS with Code Division Multiple Access (CDMA) phones where physiological parameters, subjective symptoms, and perception of RF radiation for EHS and non-EHS groups were simultaneously investigated. In this study, two volunteer groups of 18 self-reported EHS and 19 non-EHS persons were tested for both sham and real RF exposure from CDMA cellular phones with a 300 mW maximum exposure that lasted half an hour. We investigated not only the physiological parameters such as heart rate, respiration rate, and heart rate variability (HRV), but also various subjective symptoms and the perception of EMF. In conclusion, RF exposure did not have any effects on physiological parameters or subjective symptoms in either group. As for EMF perception, there was no evidence that the EHS group better perceived EMF than the non-EHS group.

  4. Remote Asynchronous Message Service Gateway

    Science.gov (United States)

    Wang, Shin-Ywan; Burleigh, Scott C.

    2011-01-01

    The Remote Asynchronous Message Service (RAMS) gateway is a special-purpose AMS application node that enables exchange of AMS messages between nodes residing in different AMS "continua," notionally in different geographical locations. JPL s implementation of RAMS gateway functionality is integrated with the ION (Interplanetary Overlay Network) implementation of the DTN (Delay-Tolerant Networking) bundle protocol, and with JPL s implementation of AMS itself. RAMS protocol data units are encapsulated in ION bundles and are forwarded to the neighboring RAMS gateways identified in the source gateway s AMS management information base. Each RAMS gateway has interfaces in two communication environments: the AMS message space it serves, and the RAMS network - the grid or tree of mutually aware RAMS gateways - that enables AMS messages produced in one message space to be forwarded to other message spaces of the same venture. Each gateway opens persistent, private RAMS network communication channels to the RAMS gateways of other message spaces for the same venture, in other continua. The interconnected RAMS gateways use these communication channels to forward message petition assertions and cancellations among themselves. Each RAMS gateway subscribes locally to all subjects that are of interest in any of the linked message spaces. On receiving its copy of a message on any of these subjects, the RAMS gateway node uses the RAMS network to forward the message to every other RAMS gateway whose message space contains at least one node that has subscribed to messages on that subject. On receiving a message via the RAMS network from some other RAMS gateway, the RAMS gateway node forwards the message to all subscribers in its own message space.

  5. ON THE ISSUE OF VECTOR CONTROL OF THE ASYNCHRONOUS MOTORS

    Directory of Open Access Journals (Sweden)

    B. I. Firago

    2015-01-01

    Full Text Available The paper considers the issue of one of the widespread types of vector control realization for the asynchronous motors with a short-circuited rotor. Of all more than 20 vector control types known presently, the following are applied most frequently: direct vector control with velocity pickup (VP, direct vector control without VP, indirect vector control with VP and indirect vector control without VP. Despite the fact that the asynchronous-motor indirect vector control without VP is the easiest and most spread, the absence of VP does not allow controlling the motor electromagnetic torque at zero velocity. This is the reason why for electric motor drives of such requirements they utilize the vector control with a velocity transducer. The systems of widest dissemination became the direct and indirect vector control systems with X-axis alignment of the synchronously rotating x–y-coordinate frame along the rotor flux-linkage vector inasmuch as this provides the simplest correlations for controlling variables. Although these two types of vector control are well presented in literature, a number of issues concerning their realization and practical application require further elaboration. These include: the block schemes adequate representation as consisted with the modern realization of vector control and clarification of the analytical expressions for evaluating the regulator parameters.The authors present a technique for evaluating the dynamics of an asynchronous electric motor drive with direct vector control and x-axis alignment along the vector of rotor flux linkage. The article offers a generalized structure of this vector control type with detailed description of its principal blocks: controlling system, frequency converter, and the asynchronous motor.The paper presents a direct vector control simulating model developed in the MatLab environment on the grounds of this structure. The authors illustrate the described technique with the results

  6. Performance Analysis of CDMA Wireless Sensor Networks in Shadowed Environment

    Directory of Open Access Journals (Sweden)

    U. DATTA

    2010-07-01

    Full Text Available This paper evaluates the performance of a CDMA based wireless sensor networks (WSN with layered architecture in terms of QoS like outage probability, bit error rate (BER, throughput, and delay, considering correlation amongst interferers in shadowed environment. Energy consumption for successful delivery of information is also evaluated at different channel conditions. Two kinds of interference namely multiple access interference (MAI and node interference (NI are considered and an infinite ARQ is assumed at link layer between a sending node and sink till successful transmission of packetized data. An appropriate analytical model of interference considering correlation amongst interferers, power control error and shadowing is developed for evaluating bit error rate (BER, packet error rate (PER, average number of retransmission for successful delivery of information, throughput, and delay in a single hop communication. A simple energy model is used for evaluating the consumption of energy for successful delivery of information between source and sink. We also evaluate the sink capacity of wireless CDMA sensor networks considering a threshold BER. Sink capacity is defined as the maximum number of sensor nodes transmitting concurrently to the sink and located within one hop layer. The impact of NI on the sink capacity is also indicated. The effects of node density, correlation amongst interferers and power control error (pce on performance of WSN are investigated. Analytical results are supported by simulation results.

  7. Neoplastic transformation in C3H 10T(1/2) cells after exposure to 835.62 MHz FDMA and 847.74 MHz CDMA radiations.

    Science.gov (United States)

    Roti Roti JL; Malyapa, R S; Bisht, K S; Ahern, E W; Moros, E G; Pickard, W F; Straube, W L

    2001-01-01

    The effect of radiofrequency (RF) radiation in the cellular phone communication range (835.62 MHz frequency division multiple access, FDMA; 847.74 MHz code division multiple access, CDMA) on neoplastic transformation frequency was measured using the in vitro C3H 10T(1/2) cell transformation assay system. To determine if 835.62 MHz FDMA or 847.74 MHz CDMA radiations have any genotoxic effects that induce neoplastic transformation, C3H 10T(1/2) cells were exposed at 37 degrees C to either of the above radiations [each at a specific absorption rate (SAR) of 0.6 W/kg] or sham-exposed at the same time for 7 days. After the culture medium was changed, the cultures were transferred to incubators and refed with fresh growth medium every 7 days. After 42 days, the cells were fixed and stained with Giemsa, and transformed foci were scored. To determine if exposure to 835.62 MHz FDMA or 847.74 MHz CDMA radiation has any epigenetic effects that can promote neoplastic transformation, cells were first exposed to 4.5 Gy of X rays to induce the transformation process and then exposed to the above radiations (SAR = 0.6 W/kg) in temperature-controlled irradiators with weekly refeeding for 42 days. After both the 7-day RF exposure and the 42-day RF exposure after X irradiation, no statistically significant differences in the transformation frequencies were observed between incubator controls, the sham-exposed (maintained in irradiators without power to the antenna), and the 835.62 MHz FDMA or 847.74 MHz CDMA-exposed groups.

  8. Handbook of asynchronous machines with variable speed

    CERN Document Server

    Razik, Hubert

    2013-01-01

    This handbook deals with the asynchronous machine in its close environment. It was born from a reflection on this electromagnetic converter whose integration in industrial environments takes a wide part. Previously this type of motor operated at fixed speed, from now on it has been integrated more and more in processes at variable speed. For this reason it seemed useful, or necessary, to write a handbook on the various aspects from the motor in itself, via the control and while finishing by the diagnosis aspect. Indeed, an asynchronous motor is used nowadays in industry where variation speed a

  9. A simple asynchronous replica-exchange implementation

    CERN Document Server

    Bussi, Giovanni

    2008-01-01

    We discuss the possibility of implementing asynchronous replica-exchange (or parallel tempering) molecular dynamics. In our scheme, the exchange attempts are driven by asynchronous messages sent by one of the computing nodes, so that different replicas are allowed to perform a different number of time-steps between subsequent attempts. The implementation is simple and based on the message-passing interface (MPI). We illustrate the advantages of our scheme with respect to the standard synchronous algorithm and we benchmark it for a model Lennard-Jones liquid on an IBM-LS21 blade center cluster.

  10. Gigabit Ethernet Asynchronous Clock Compensation FIFO

    Science.gov (United States)

    Duhachek, Jeff

    2012-01-01

    Clock compensation for Gigabit Ethernet is necessary because the clock recovered from the 1.25 Gb/s serial data stream has the potential to be 200 ppm slower or faster than the system clock. The serial data is converted to 10-bit parallel data at a 125 MHz rate on a clock recovered from the serial data stream. This recovered data needs to be processed by a system clock that is also running at a nominal rate of 125 MHz, but not synchronous to the recovered clock. To cross clock domains, an asynchronous FIFO (first-in-first-out) is used, with the write pointer (wprt) in the recovered clock domain and the read pointer (rptr) in the system clock domain. Because the clocks are generated from separate sources, there is potential for FIFO overflow or underflow. Clock compensation in Gigabit Ethernet is possible by taking advantage of the protocol data stream features. There are two distinct data streams that occur in Gigabit Ethernet where identical data is transmitted for a period of time. The first is configuration, which happens during auto-negotiation. The second is idle, which occurs at the end of auto-negotiation and between every packet. The identical data in the FIFO can be repeated by decrementing the read pointer, thus compensating for a FIFO that is draining too fast. The identical data in the FIFO can also be skipped by incrementing the read pointer, which compensates for a FIFO draining too slowly. The unique and novel features of this FIFO are that it works in both the idle stream and the configuration streams. The increment or decrement of the read pointer is different in the idle and compensation streams to preserve disparity. Another unique feature is that the read pointer to write pointer difference range changes between compensation and idle to minimize FIFO latency during packet transmission.

  11. A transiently chaotic neural-network implementation of the CDMA multiuser detector.

    Science.gov (United States)

    Wang, B; Nie, J; He, Z

    1999-01-01

    The complex dynamics of the chaotic neural networks makes it possible for them to escape from local minimum of the simple gradient descent neurodynamics. In this letter we use a transiently chaotic neural network to detect the CDMA multiuser signals and hence obtain an implementation scheme of the CDMA multiuser detector (TCNN-MD). Computer simulation results show that the proposed detector is clearly superior to Hopfield neural-network-based detector.

  12. Perbandingan Efek Cell Breathing Pada Jaringan Cdma 20001x Evdo Pada Frekuensi Carrier Yang Berbeda

    OpenAIRE

    Ir. Sigit Kusmaryanto, M.Eng., Aindyta Ayu Pradani., Dr. Ir. Sholeh Hadi pramono, MS

    2015-01-01

    Skripsi ini akan membahas perbandingan efekcell breathing pada jaringan CDMA 2000 1x EVDOdengan frekuensi carrier yang berbeda yaitu padafrekuensi 800 MHz dan 1900 MHz. Parameter yangdiamati antara lain MAPL (Maximum Allowedable PathLoss), radius sel, dan jumlah user. Berdasarkan data danhasil perhitungan, efek cell breathing yang terjadi ketikajaringan CDMA 20001X EVDO menggunakan frekuensicarrier yang berbeda menimbulkan efek yang berbeda.Disini perhitungan dilakukan dengan merubahinterfere...

  13. Development of the Average Likelihood Function for Code Division Multiple Access (CDMA) Using BPSK and QPSK Symbols

    Science.gov (United States)

    2015-01-01

    DEVELOPMENT OF THE AVERAGE LIKELIHOOD FUNCTION FOR CODE DIVISION MULTIPLE ACCESS ( CDMA ) USING BPSK AND QPSK SYMBOLS JANUARY 2015...To) OCT 2013 – OCT 2014 4. TITLE AND SUBTITLE DEVELOPMENT OF THE AVERAGE LIKELIHOOD FUNCTION FOR CODE DIVISION MULTIPLE ACCESS ( CDMA ) USING BPSK...effort titled “Average Likelihood Methods for CDMA ”. In this report, we extend the derivation of the average likelihood function for three additional

  14. DEFINITION OF DYNAMIC INDUCTANCES OF THE ASYNCHRONOUS ENGINE WITH REGARD TO PROCESSES OF SATURATION

    Directory of Open Access Journals (Sweden)

    D. O. Kulagin

    2014-07-01

    Full Text Available Development of mathematical model of asynchronous machines in (d, q coordinate system with taking into account the saturation of magnetic circuits is performed. In the paper, we used the method of dynamic inductances, which is connected with the use of a systematic study of motor properties. An analytical model of asynchronous motor magnetic circuit, which is taken into account action of the tangential and radial dynamic inductances is created. On the basis of this the sensor dynamic inductances of rich machine, which was recorded in (d, q coordinate system of equations of rotor and stator circles of asynchronous motor with the saturation were built. The author suggests to use the method of dynamic inductances at construction of asynchronous engine mathematical model, that allows to take into account the saturation of the main magnetic path for the modes with a wide range of changes in the flow of mutual induction between the stator and the rotor, saturation flow path, the scattering modes that are characterized by large current circuits of the machine, induction, due to processes of saturation, between mutually perpendicular to the contours of the machine, as well as the joint saturation worker thread and threads scattering modes that are characterized by the significant size of the workflow and large values of currents contours of the machine. The mathematical model allows to take into account the change of the magnetic state of asynchronous motor as necessity to build adequate systems of control drives and driving

  15. Handoff Triggering and Network Selection Algorithms for Load-Balancing Handoff in CDMA-WLAN Integrated Networks

    Directory of Open Access Journals (Sweden)

    Kim Jang-Sub

    2008-01-01

    Full Text Available This paper proposes a novel vertical handoff algorithm between WLAN and CDMA networks to enable the integration of these networks. The proposed vertical handoff algorithm assumes a handoff decision process (handoff triggering and network selection. The handoff trigger is decided based on the received signal strength (RSS. To reduce the likelihood of unnecessary false handoffs, the distance criterion is also considered. As a network selection mechanism, based on the wireless channel assignment algorithm, this paper proposes a context-based network selection algorithm and the corresponding communication algorithms between WLAN and CDMA networks. This paper focuses on a handoff triggering criterion which uses both the RSS and distance information, and a network selection method which uses context information such as the dropping probability, blocking probability, GoS (grade of service, and number of handoff attempts. As a decision making criterion, the velocity threshold is determined to optimize the system performance. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations using four handoff strategies. The four handoff strategies are evaluated and compared with each other in terms of GOS. Finally, the proposed scheme is validated by computer simulations.

  16. Handoff Triggering and Network Selection Algorithms for Load-Balancing Handoff in CDMA-WLAN Integrated Networks

    Directory of Open Access Journals (Sweden)

    Khalid Qaraqe

    2008-10-01

    Full Text Available This paper proposes a novel vertical handoff algorithm between WLAN and CDMA networks to enable the integration of these networks. The proposed vertical handoff algorithm assumes a handoff decision process (handoff triggering and network selection. The handoff trigger is decided based on the received signal strength (RSS. To reduce the likelihood of unnecessary false handoffs, the distance criterion is also considered. As a network selection mechanism, based on the wireless channel assignment algorithm, this paper proposes a context-based network selection algorithm and the corresponding communication algorithms between WLAN and CDMA networks. This paper focuses on a handoff triggering criterion which uses both the RSS and distance information, and a network selection method which uses context information such as the dropping probability, blocking probability, GoS (grade of service, and number of handoff attempts. As a decision making criterion, the velocity threshold is determined to optimize the system performance. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations using four handoff strategies. The four handoff strategies are evaluated and compared with each other in terms of GOS. Finally, the proposed scheme is validated by computer simulations.

  17. Asynchronous stream processing with S-Net

    NARCIS (Netherlands)

    Grelck, C.; Scholz, S.-B.; Shafarenko, A.

    2010-01-01

    We present the rationale and design of S-Net, a coordination language for asynchronous stream processing. The language achieves a near-complete separation between the application code, written in any conventional programming language, and the coordination/communication code written in S-Net. Our

  18. Increasing Student Engagement Using Asynchronous Learning

    Science.gov (United States)

    Northey, Gavin; Bucic, Tania; Chylinski, Mathew; Govind, Rahul

    2015-01-01

    Student engagement is an ongoing concern for educators because of its positive association with deep learning and educational outcomes. This article tests the use of a social networking site (Facebook) as a tool to facilitate asynchronous learning opportunities that complement face-to-face interactions and thereby enable a stronger learning…

  19. Asynchronous versus Synchronous Learning in Pharmacy Education

    Science.gov (United States)

    Motycka, Carol A.; St. Onge, Erin L.; Williams, Jennifer

    2013-01-01

    Objective: To better understand the technology being used today in pharmacy education through a review of the current methodologies being employed at various institutions. Also, to discuss the benefits and difficulties of asynchronous and synchronous methodologies, which are being utilized at both traditional and distance education campuses.…

  20. Interference subspace rejection in wideband CDMA:

    DEFF Research Database (Denmark)

    Hansen, Henrik; Affes, Sofiene; Mermelstein, Paul

    2001-01-01

    This paper extends our study on a multi-user receiver structure for base-station receivers with antenna arrays in multicellular systems. The receiver employs a beamforming structure with constraints that nulls the signal component in appropriate interference subspaces. Here we introduce a new mod...

  1. a Beat Perioid Observation of the Asynchronous Polar by Cam.

    Science.gov (United States)

    Rainger, Jonathan

    We propose to observe the hard X-ray bright asynchronous polar BY Cam throughout its beat cycle in order to investigate the changes in the magnetic capture of the accretion stream as the secondary star changes in azimuth with respect to the white dwarf. Regular snap-shots of the light curve will reveal the order behind the chaos. Previous observations have been taken in 3 days or less, our monitoring plan over 21 days offers the only real hope of understanding these difficult systems.

  2. Subband Adaptive Array for DS-CDMA Mobile Radio

    Directory of Open Access Journals (Sweden)

    Tran Xuan Nam

    2004-01-01

    Full Text Available We propose a novel scheme of subband adaptive array (SBAA for direct-sequence code division multiple access (DS-CDMA. The scheme exploits the spreading code and pilot signal as the reference signal to estimate the propagation channel. Moreover, instead of combining the array outputs at each output tap using a synthesis filter and then despreading them, we despread directly the array outputs at each output tap by the desired user's code to save the synthesis filter. Although its configuration is far different from that of 2D RAKEs, the proposed scheme exhibits relatively equivalent performance of 2D RAKEs while having less computation load due to utilising adaptive signal processing in subbands. Simulation programs are carried out to explore the performance of the scheme and compare its performance with that of the standard 2D RAKE.

  3. A beamformer for CDMA with enhanced near-far resistance

    DEFF Research Database (Denmark)

    Hansen, Henrik; Affes, S.; Mermelstein, P.

    1999-01-01

    The spatio-temporal array-receiver (STAR) achieves good performance in CDMA with multiple receiving antennas where the interference can be characterized as AWGN uncorrelated with the signal. To enhance its near-far resistance in correlated noise environments, we introduce optimal combining...... of the spatio-temporal components. Nearly as good performance can be obtained with a low complexity adaptive beamformer combination of the antenna and multipath diversity branches. Simulation results indicate that the modified STAR manifests significant gain in near-far resistance over its original version......, more so with more branches. They also suggest that exploiting additional temporal correlation fingers as interference references can further improve near-far resistance in poor diversity situations....

  4. Subband Adaptive Array for DS-CDMA Mobile Radio

    Science.gov (United States)

    Tran, Xuan Nam; Omata, Takanori; Taniguchi, Tetsuki; Karasawa, Yoshio

    2004-12-01

    We propose a novel scheme of subband adaptive array (SBAA) for direct-sequence code division multiple access (DS-CDMA). The scheme exploits the spreading code and pilot signal as the reference signal to estimate the propagation channel. Moreover, instead of combining the array outputs at each output tap using a synthesis filter and then despreading them, we despread directly the array outputs at each output tap by the desired user's code to save the synthesis filter. Although its configuration is far different from that of 2D RAKEs, the proposed scheme exhibits relatively equivalent performance of 2D RAKEs while having less computation load due to utilising adaptive signal processing in subbands. Simulation programs are carried out to explore the performance of the scheme and compare its performance with that of the standard 2D RAKE.

  5. Neurochemical and neuropharmacological aspects of circadian disruptions: an introduction to asynchronization.

    Science.gov (United States)

    Kohyama, Jun

    2011-06-01

    Circadian disruptions are common in modern society, and there is an urgent need for effective treatment strategies. According to standard diagnostic criteria, most adolescents showing both insomnia and daytime sleepiness are diagnosed as having behavioral-induced sleep efficiency syndrome resulting from insomnia due to inadequate sleep hygiene. However, a simple intervention of adequate sleep hygiene often fails to treat them. As a solution to this clinical problem, the present review first overviews the basic neurochemical and neuropharmachological aspects of sleep and circadian rhythm regulation, then explains several circadian disruptions from similar viewpoints, and finally introduces the clinical notion of asynchronization. Asynchronization is designated to explain the pathophysiology/pathogenesis of exhibition of both insomnia and hypersomnia in adolescents, which comprises disturbances in various aspects of biological rhythms. The major triggers for asynchronization are considered to be a combination of light exposure during the night, which disturbs the biological clock and decreases melatonin secretion, as well as a lack of light exposure in the morning, which prohibits normal synchronization of the biological clock to the 24-hour cycle of the earth and decreases the activity of serotonin. In the chronic phase of asynchronization, involvement of both wake- and sleep-promoting systems is suggested. Both conventional and alternative therapeutic approaches for potential treatment of asynchronization are suggested.

  6. A Review on Successive Interference Cancellation-Based Optical PPM-CDMA Signaling

    Science.gov (United States)

    Alsowaidi, Naif; Eltaif, Tawfig; Mokhtar, Mohd Ridzuan

    2017-06-01

    This paper presents a comprehensive review of successive interference cancellation (SIC) scheme using pulse position modulation (PPM) for optical code division multiple access (OCDMA) systems. SIC scheme focuses on high-intensity signal, which will be selected after all users were detected, and then it will be subtracted from the overall received signal, hence, generating a new received signal. This process continues till all users eliminated one by one have been detected. It is shown that the random location of the sequences due to PPM encoding can reduce the probability of concentrated buildup of the pulse overlap in any one-slot time, and support SIC to easily remove the effect of the strongest signal at each stage of the cancellation process. The system bit error rate (BER) performance with modified quadratic congruence (MQC) codes used as signature sequence has been investigated. A detailed theoretical analysis of proposed system taking into account the impact of imperfect interference cancellation, the loss produced from the splitting during encoding and decoding, the channel loss and multiple access interference is presented. Results show that under average effective power constraint optical CDMA system using SIC scheme with M-ary PPM modulation outperforms conventional correlator detector and SIC scheme with on-off keying (OOK) modulation.

  7. Formation of the wide asynchronous binary asteroid population

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, Seth A. [Department of Astrophysical and Planetary Science, UCB 391, University of Colorado, Boulder, CO 80309 (United States); Scheeres, Daniel J.; McMahon, Jay [Department of Aerospace Engineering Sciences, UCB 429, University of Colorado, Boulder, CO 80309 (United States)

    2014-01-01

    We propose and analyze a new mechanism for the formation of the wide asynchronous binary population. These binary asteroids have wide semimajor axes relative to most near-Earth and main belt asteroid systems. Confirmed members have rapidly rotating primaries and satellites that are not tidally locked. Previously suggested formation mechanisms from impact ejecta, from planetary flybys, and directly from rotational fission events cannot satisfy all of the observations. The newly hypothesized mechanism works as follows: (1) these systems are formed from rotational fission, (2) their satellites are tidally locked, (3) their orbits are expanded by the binary Yarkovsky-O'Keefe-Radzievskii-Paddack (BYORP) effect, (4) their satellites desynchronize as a result of the adiabatic invariance between the libration of the secondary and the mutual orbit, and (5) the secondary avoids resynchronization because of the YORP effect. This seemingly complex chain of events is a natural pathway for binaries with satellites that have particular shapes, which define the BYORP effect torque that acts on the system. After detailing the theory, we analyze each of the wide asynchronous binary members and candidates to assess their most likely formation mechanism. Finally, we suggest possible future observations to check and constrain our hypothesis.

  8. THE ROLE OF OFFLINE METALANGUAGE TALK IN ASYNCHRONOUS COMPUTER-MEDIATED COMMUNICATION

    Directory of Open Access Journals (Sweden)

    Keiko Kitade

    2008-02-01

    Full Text Available In order to demonstrate how learners utilize the text-based asynchronous attributes of the Bulletin Board System, this study explored Japanese-as-a-second-language learners' metalanguage episodes (Swain & Lapkin, 1995, 1998 in offline verbal peer speech and online asynchronous discussions with their Japanese key pals. The findings suggest the crucial role of offline collaborative dialogue, the interactional modes in which the episodes occur, and the unique discourse structure of metalanguage episodes concerning online and offline interactions. A high score on the posttest also suggests the high retention of linguistic knowledge constructed through offline peer dialogue. In the offline mode, the learners were able to collaboratively construct knowledge with peers in the stipulated time, while simultaneously focusing on task content in the online interaction. The retrospective interviews and questionnaires reveal the factors that could affect the benefits of the asynchronous computer-mediated communication medium for language learning.

  9. Concerted and asynchronous mechanism of ground state proton transfer in alcohol mediated 7-hydroxyquinoline

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Baotao [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Jang, Du-Jeon [Department of Chemistry, Seoul National University, Seoul 151-742 (Korea, Republic of); Lee, Jin Yong, E-mail: jinylee@skku.edu [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2015-07-29

    Highlights: • Reaction rate constants obtained by DFT agree with experimental ones quite well. • Experimental postulate of concerted and asynchronous GSPT was confirmed. • The GSPT reaction can be decomposed into three asynchronous steps. - Abstract: Alcohols mediated 7-hydroxyquinoline (7-HQ) complex has received enormous attractions on the issue of proton transfer reaction in the ground and excited states. In the present paper, concentrating on the ground state proton transfer (GSPT), density functional theory (DFT) calculations were carried out to investigate the intrinsic insight into the reaction mechanism. We found that the GSPT is concerted and asynchronous process and can be accelerated by more acidic alcohol. Such GSPT was initiated by the proton transfer from alcohol to keto group of 7-HQ and finished by the proton transfer from nitrogen to alcohol. Our findings were in agreement with experimental conclusions quite well. Our results would be helpful to understand the proton transfer reaction for 7-HQ and related systems.

  10. Asynchronous updates can promote the evolution of cooperation on multiplex networks

    Science.gov (United States)

    Allen, James M.; Hoyle, Rebecca B.

    2017-04-01

    We study the importance to the frequency of cooperation of the choice of updating strategies in a game played asynchronously or synchronously across layers in a multiplex network. Updating asynchronously in the public goods game leads to higher frequencies of cooperation compared to synchronous updates. How large this effect is depends on the sensitivity of the game dynamics to changes in the number of cooperators surrounding a player, with the largest effect observed when players payoffs are small. The discovery of this effect enhances understanding of cooperation on multiplex networks, and demonstrates a new way to maintain cooperation in these systems.

  11. Asynchronous teaching of psychomotor skills through VR annotations: evaluation in digital rectal examination.

    Science.gov (United States)

    Rissanen, Mikko J; Kume, Naoto; Kuroda, Yoshihiro; Kuroda, Tomohiro; Yoshimura, Koji; Yoshihara, Hiroyuki

    2008-01-01

    Many VR technology based training systems use expert's motion data as the training aid, but would not provide any short-cut to teaching medical skills that do not depend on exact motions. Earlier we presented Annotated Simulation Records (ASRs), which can be used to encapsulate experts' insight on psychomotor skills. Annotations made to behavioural parameters in training simulators enable asynchronous teaching instead of just motion training in a proactive way to the learner. We evaluated ASRs for asynchronous teaching of Digital Rectal Examination (DRE) with 3 urologists and 8 medical students. The ASRs were found more effective than motion-based training with verbal feedback.

  12. Effects of W-CDMA 1950 MHz EMF emitted by mobile phones on regional cerebral blood flow in humans.

    Science.gov (United States)

    Mizuno, Yoko; Moriguchi, Yoshiya; Hikage, Takashi; Terao, Yasuo; Ohnishi, Takashi; Nojima, Toshio; Ugawa, Yoshikazu

    2009-10-01

    Use of the third generation mobile phone system is increasing worldwide. This is the first study to investigate the effects of the third generation system on regional cerebral blood flow (rCBF) in humans. We compared effects of the electromagnetic field (EMF) emitted from the Wideband Code Division Multiple Access (W-CDMA) cellular system versus sham control exposure on rCBF in humans. Nine healthy male volunteers participated in this study. Positron emission tomography (PET) scans were obtained before, during, and after unilateral 30 min EMF exposure. The subtraction analysis revealed no significant rCBF changes caused by the EMF conditions compared with the sham exposure, suggesting that EMF emitted by a third generation mobile phone does not affect rCBF in humans.

  13. Performance analysis of DS/CDMA with noncoherent M-ary orthogonal modulation in multipath fading channels

    Science.gov (United States)

    Jalloul, Louay M. A.; Holtzman, Jack M.

    1994-06-01

    In this paper, the performance of a DS/CDMA system using M-ary orthogonal modulation with noncoherent demodulation is evaluated. The system operates in a multipath fading channel. A RAKE receiver structure with equal gain combining is used for demodulation. An approximation to the bit error probability is given which depends only on the first- and second-order moments of the multipath energies. The analysis results are compared with the results from computer simulations. It is seen that the approximation is accurate for multipaths energies with realistic coefficient of variation. System performance is also evaluated in terms of the capacity, which is defined as the number of users that can be supported at a given bit error probability. The approximation is used to evaluate the capacity reductions due to power variations caused by multipath fading.

  14. A hybrid path-oriented code assignment CDMA-based MAC protocol for underwater acoustic sensor networks.

    Science.gov (United States)

    Chen, Huifang; Fan, Guangyu; Xie, Lei; Cui, Jun-Hong

    2013-11-04

    Due to the characteristics of underwater acoustic channel, media access control (MAC) protocols designed for underwater acoustic sensor networks (UWASNs) are quite different from those for terrestrial wireless sensor networks. Moreover, in a sink-oriented network with event information generation in a sensor field and message forwarding to the sink hop-by-hop, the sensors near the sink have to transmit more packets than those far from the sink, and then a funneling effect occurs, which leads to packet congestion, collisions and losses, especially in UWASNs with long propagation delays. An improved CDMA-based MAC protocol, named path-oriented code assignment (POCA) CDMA MAC (POCA-CDMA-MAC), is proposed for UWASNs in this paper. In the proposed MAC protocol, both the round-robin method and CDMA technology are adopted to make the sink receive packets from multiple paths simultaneously. Since the number of paths for information gathering is much less than that of nodes, the length of the spreading code used in the POCA-CDMA-MAC protocol is shorter greatly than that used in the CDMA-based protocols with transmitter-oriented code assignment (TOCA) or receiver-oriented code assignment (ROCA). Simulation results show that the proposed POCA-CDMA-MAC protocol achieves a higher network throughput and a lower end-to-end delay compared to other CDMA-based MAC protocols.

  15. SIMULASI TEKNIK POWER CONTROL DAN MULTI USER DETECTION PADA SISTEM KOMUNIKASI DS-CDMA

    Directory of Open Access Journals (Sweden)

    Yuli Christyono

    2012-02-01

    Full Text Available CDMA is interference limited multiple access system. Because all users transmit on the same frequency,internal interference generated by the system is the most significant factor in determining system capacity andcall quality. The transmit power for each user must be reduced to limit interference, however, the power shouldbe enough to maintain the required Eb/No (signal to noise ratio for a satisfactory call quality. Maximumcapacity is achieved when Eb/No of every user is at the minimum level needed for the acceptable channelperformance. As the MS moves around, the RF environment continuously changes due to fast and slow fading,external interference, shadowing , and other factors. The aim of the dynamic power control is to limittransmitted power on both the links while maintaining link quality under all conditions. Additional advantagesare longer mobile battery life and longer life span of BTS power amplifiers.In this research will be made a sumulation of power control and multi user detection to avoid the interferencebetween MS.Observations show that the increasing number of users will decrease the value of Signal to Interfrence Ratio(SIR / SIR below the target. To cope the growing number of users increases can be done by iteration / updatingpower transmit so the convergence computation can be reached and target value SIR can be achieved. Inaddition, to reduce interference can also be done by extending the number of chips.

  16. High Capacity Downlink Transmission with MIMO Interference Subspace Rejection in Multicellular CDMA Networks

    Directory of Open Access Journals (Sweden)

    Hansen Henrik

    2004-01-01

    Full Text Available We proposed recently a new technique for multiuser detection in CDMA networks, denoted by interference subspace rejection (ISR, and evaluated its performance on the uplink. This paper extends its application to the downlink (DL. On the DL, the information about the interference is sparse, for example, spreading factor (SF and modulation of interferers may not be known, which makes the task much more challenging. We present three new ISR variants which require no prior knowledge of interfering users. The new solutions are applicable to MIMO systems and can accommodate any modulation, coding, SF, and connection type. We propose a new code allocation scheme denoted by DACCA which significantly reduces the complexity of our solution at the receiving mobile. We present estimates of user capacities and data rates attainable under practically reasonable conditions regarding interferences identified and suppressed in a multicellular interference-limited system. We show that the system capacity increases linearly with the number of antennas despite the existence of interference. Our new DL multiuser receiver consistently provides an Erlang capacity gain of at least over the single-user detector.

  17. Verification of Building Blocks for Asynchronous Circuits

    Directory of Open Access Journals (Sweden)

    Freek Verbeek

    2013-04-01

    Full Text Available Scalable formal verification constitutes an important challenge for the design of asynchronous circuits. Deadlock freedom is a property that is desired but hard to verify. It is an emergent property that has to be verified monolithically. We present our approach to using ACL2 to verify necessary and sufficient conditions over asynchronous delay-insensitive primitives. These conditions are used to derive SAT/SMT instances from circuits built out of these primitives. These SAT/SMT instances help in establishing absence of deadlocks. Our verification effort consists of building an executable checker in the ACL2 logic tailored for our purpose. We prove that this checker is correct. This approach enables us to prove ACL2 theorems involving defun-sk constructs and free variables fully automatically.

  18. Asynchronous Gossip for Averaging and Spectral Ranking

    Science.gov (United States)

    Borkar, Vivek S.; Makhijani, Rahul; Sundaresan, Rajesh

    2014-08-01

    We consider two variants of the classical gossip algorithm. The first variant is a version of asynchronous stochastic approximation. We highlight a fundamental difficulty associated with the classical asynchronous gossip scheme, viz., that it may not converge to a desired average, and suggest an alternative scheme based on reinforcement learning that has guaranteed convergence to the desired average. We then discuss a potential application to a wireless network setting with simultaneous link activation constraints. The second variant is a gossip algorithm for distributed computation of the Perron-Frobenius eigenvector of a nonnegative matrix. While the first variant draws upon a reinforcement learning algorithm for an average cost controlled Markov decision problem, the second variant draws upon a reinforcement learning algorithm for risk-sensitive control. We then discuss potential applications of the second variant to ranking schemes, reputation networks, and principal component analysis.

  19. Existence test for asynchronous interval iterations

    DEFF Research Database (Denmark)

    Madsen, Kaj; Caprani, O.; Stauning, Ole

    1997-01-01

    In the search for regions that contain fixed points ofa real function of several variables, tests based on interval calculationscan be used to establish existence ornon-existence of fixed points in regions that are examined in the course ofthe search. The search can e.g. be performed...... as a synchronous (sequential) interval iteration:In each iteration step all components of the iterate are calculatedbased on the previous iterate. In this case it is straight forward to base simple interval existence and non-existencetests on the calculations done in each step of the iteration. The search can also...... be performed as an asynchronous (parallel) iteration: Only a few components are changed in each stepand this calculation is in general based on components from differentprevious iterates. For the asynchronous iteration it turns out thatsimple tests of existence and non-existence can be based...

  20. Computing by Temporal Order: Asynchronous Cellular Automata

    Directory of Open Access Journals (Sweden)

    Michael Vielhaber

    2012-08-01

    Full Text Available Our concern is the behaviour of the elementary cellular automata with state set 0,1 over the cell set Z/nZ (one-dimensional finite wrap-around case, under all possible update rules (asynchronicity. Over the torus Z/nZ (n<= 11,we will see that the ECA with Wolfram rule 57 maps any v in F_2^n to any w in F_2^n, varying the update rule. We furthermore show that all even (element of the alternating group bijective functions on the set F_2^n = 0,...,2^n-1, can be computed by ECA57, by iterating it a sufficient number of times with varying update rules, at least for n <= 10. We characterize the non-bijective functions computable by asynchronous rules.

  1. Asynchronous Task-Based Polar Decomposition on Manycore Architectures

    KAUST Repository

    Sukkari, Dalal

    2016-10-25

    This paper introduces the first asynchronous, task-based implementation of the polar decomposition on manycore architectures. Based on a new formulation of the iterative QR dynamically-weighted Halley algorithm (QDWH) for the calculation of the polar decomposition, the proposed implementation replaces the original and hostile LU factorization for the condition number estimator by the more adequate QR factorization to enable software portability across various architectures. Relying on fine-grained computations, the novel task-based implementation is also capable of taking advantage of the identity structure of the matrix involved during the QDWH iterations, which decreases the overall algorithmic complexity. Furthermore, the artifactual synchronization points have been severely weakened compared to previous implementations, unveiling look-ahead opportunities for better hardware occupancy. The overall QDWH-based polar decomposition can then be represented as a directed acyclic graph (DAG), where nodes represent computational tasks and edges define the inter-task data dependencies. The StarPU dynamic runtime system is employed to traverse the DAG, to track the various data dependencies and to asynchronously schedule the computational tasks on the underlying hardware resources, resulting in an out-of-order task scheduling. Benchmarking experiments show significant improvements against existing state-of-the-art high performance implementations (i.e., Intel MKL and Elemental) for the polar decomposition on latest shared-memory vendors\\' systems (i.e., Intel Haswell/Broadwell/Knights Landing, NVIDIA K80/P100 GPUs and IBM Power8), while maintaining high numerical accuracy.

  2. Asynchronous replica exchange software for grid and heterogeneous computing

    Science.gov (United States)

    Gallicchio, Emilio; Xia, Junchao; Flynn, William F.; Zhang, Baofeng; Samlalsingh, Sade; Mentes, Ahmet; Levy, Ronald M.

    2015-11-01

    Parallel replica exchange sampling is an extended ensemble technique often used to accelerate the exploration of the conformational ensemble of atomistic molecular simulations of chemical systems. Inter-process communication and coordination requirements have historically discouraged the deployment of replica exchange on distributed and heterogeneous resources. Here we describe the architecture of a software (named ASyncRE) for performing asynchronous replica exchange molecular simulations on volunteered computing grids and heterogeneous high performance clusters. The asynchronous replica exchange algorithm on which the software is based avoids centralized synchronization steps and the need for direct communication between remote processes. It allows molecular dynamics threads to progress at different rates and enables parameter exchanges among arbitrary sets of replicas independently from other replicas. ASyncRE is written in Python following a modular design conducive to extensions to various replica exchange schemes and molecular dynamics engines. Applications of the software for the modeling of association equilibria of supramolecular and macromolecular complexes on BOINC campus computational grids and on the CPU/MIC heterogeneous hardware of the XSEDE Stampede supercomputer are illustrated. They show the ability of ASyncRE to utilize large grids of desktop computers running the Windows, MacOS, and/or Linux operating systems as well as collections of high performance heterogeneous hardware devices.

  3. Emergence of Asynchronous Local Clocks in Excitable Media.

    Science.gov (United States)

    Gerum, Richard Carl; Fabry, Ben; Metzner, Claus

    2015-01-01

    Excitable media such as the myocardium or the brain consist of arrays of coupled excitable elements, in which the local excitation of a single element can propagate to its neighbors in the form of a non-linear autowave. Since each element has to pass through a refractory period immediately after excitation, the frequency of autowaves is self-limiting. In this work, we consider the case where each element is spontaneously excited at a fixed average rate and thereby initiates a new autowave. Although these spontaneous self-excitation events are modelled as independent Poisson point processes with exponentially distributed waiting times, the travelling autowaves lead collectively to a non-exponential, unimodal waiting time distribution for the individual elements. With increasing system size, a global 'clock' period T emerges as the most probable waiting time for each element, which fluctuates around T with an increasingly small but non-zero variance. This apparent synchronization between asynchronous, temporally uncorrelated point processes differs from synchronization effects between perfect oscillators interacting in a phase-aligning manner. Finally, we demonstrate that asynchronous local clocks also emerge in non-homogeneous systems in which the rates of self-excitation are different for all individuals, suggesting that this novel mechanism can occur in a wide range of excitable media.

  4. Blending Online Asynchronous and Synchronous Learning

    Directory of Open Access Journals (Sweden)

    Lisa C. Yamagata-Lynch

    2014-04-01

    Full Text Available In this article I will share a qualitative self-study about a 15-week blended 100% online graduate level course facilitated through synchronous meetings on Blackboard Collaborate and asynchronous discussions on Blackboard. I taught the course at the University of Tennessee (UT during the spring 2012 semester and the course topic was online learning environments. The primary research question of this study was: How can the designer/instructor optimize learning experiences for students who are studying about online learning environments in a blended online course relying on both synchronous and asynchronous technologies? I relied on student reflections of course activities during the beginning, middle, and the end of the semester as the primary data source to obtain their insights regarding course experiences. Through the experiences involved in designing and teaching the course and engaging in this study I found that there is room in the instructional technology research community to address strategies for facilitating online synchronous learning that complement asynchronous learning. Synchronous online whole class meetings and well-structured small group meetings can help students feel a stronger sense of connection to their peers and instructor and stay engaged with course activities. In order to provide meaningful learning spaces in synchronous learning environments, the instructor/designer needs to balance the tension between embracing the flexibility that the online space affords to users and designing deliberate structures that will help them take advantage of the flexible space.

  5. Amelioration de la qualite d'energie d'un systeme de conversion d'energie eolienne a base de machine asynchrone a double alimentation et connecte au reseau electrique =

    Science.gov (United States)

    Abderrahim, Iheb

    Wind power generation has grown strongly in the last decade. This results in the development of Wind Energy Conversion System WECS at the levels of modeling and electrical control. Modern WECS operate at varying wind speeds and are equipped with synchronous and asynchronous generators. Among these generators, the Doubly-Fed Induction Generator (DFIG) offers several advantages and capabilities of active and reactive power in four quadrants. WECS based DFIG also causes less conversion costs and minimum energy losses compared with a WECS based on a synchronous generator powered entirely by full scale of power converters. The connection of such a system to the electrical distribution network involves bidirectional operation of networks. This is clearly established in sub and super synchronous operating modes of DFIG. The grid provides the active power to the rotor of DFIG in sub synchronous operating mode and receives the active power of the rotor in super synchronous operating mode of DFIG. Energy quality is thus of major importance during the integration of wind power to the grid. Poor wave quality can affect network stability and could even cause major problems and consequences. This is even more critical where non-linear loads such as the switching power supplies and variable speed drives, are connected to the grid. The idea of this research work is how to mitigate the problems associated with the wave quality while ensuring better implementation of DFIG so that the whole of WECS remains insensitive to external disturbances and parametric variations. The Grid Side Converter (GSC) must be able to compensate harmonics, current unbalance and reactive power injected by a nonlinear three-phase unbalanced load connected to the grid. In addition to these innovative features to improve the conditions of operation of the grid, it provides also the power flow during different modes of operation of the DFIG. It is considered a simple, efficient and cost competitive solution

  6. Router Designs for an Asynchronous Time-Division-Multiplexed Network-on-Chip

    DEFF Research Database (Denmark)

    Kasapaki, Evangelia; Sparsø, Jens; Sørensen, Rasmus Bo

    2013-01-01

    In this paper we explore the design of an asynchronous router for a time-division-multiplexed (TDM) network-on-chip (NOC) that is being developed for a multi-processor platform for hard real-time systems. TDM inherently requires a common time reference, and existing TDM-based NOC designs are either...

  7. Credit Hours with No Set Time: A Study of Credit Policies in Asynchronous Online Education

    Science.gov (United States)

    Prasuhn, Frederick Carl

    2014-01-01

    U.S. public university system policies were examined to learn how credit hours were determined for asynchronous online education. Findings indicated that (a) credit hour meaning and use are not consistent, (b) primary responsibility for credit hour decisions was at the local level, and (c) no policies exist to guide credit hour application for…

  8. An Asynchronous P300 BCI With SSVEP-Based Control State Detection

    DEFF Research Database (Denmark)

    Panicker, Rajesh C.; Puthusserypady, Sadasivan; Sun, Ying

    2011-01-01

    In this paper, an asynchronous brain–computer interface (BCI) system combining the P300 and steady-state visually evoked potentials (SSVEPs) paradigms is proposed. The information transfer is accomplished using P300 event-related potential paradigm and the control state (CS) detection is achieved...

  9. Asynchronous Detection of Trials Onset from Raw EEG Signals.

    Science.gov (United States)

    Lopez-Gordo, M A; Grima Murcia, M D; Padilla, Pablo; Pelayo, F; Fernandez, E

    2016-11-01

    Clinical processing of event-related potentials (ERPs) requires a precise synchrony between the stimulation and the acquisition units that are guaranteed by means of a physical link between them. This precise synchrony is needed since temporal misalignments during trial averaging can lead to high deviations of peak times, thus causing error in diagnosis or inefficiency in classification in brain-computer interfaces (BCIs). Out of the laboratory, mobile EEG systems and BCI headsets are not provided with the physical link, thus being inadequate for acquisition of ERPs. In this study, we propose a method for the asynchronous detection of trials onset from raw EEG without physical links. We validate it with a BCI application based on the dichotic listening task. The user goal was to attend the cued auditory message and to report three keywords contained in it while ignoring the other message. The BCI goal was to detect the attended message from the analysis of auditory ERPs. The rate of successful onset detection in both synchronous (using the real onset) and asynchronous (blind detection of trial onset from raw EEG) was 73% with a synchronization error of less than 1[Formula: see text]ms. The level of synchronization provided by this proposal would allow home-based acquisition of ERPs with low cost BCI headsets and any media player unit without physical links between them.

  10. Dynamic Resource Management in MC-CDMA Based Cellular Wireless Networks

    Directory of Open Access Journals (Sweden)

    Bala Jeevitha Vani

    2009-10-01

    Full Text Available Most of the multimedia and Internet services today are asymmetric in nature, and require high data rate support. Allocating equal band width in both uplink and downlink is not prudent solution, as most of the time user requirement is more either in uplink or downlink. The Multi Carrier Code Division Multiple Access (MC-CDMA system with time division duplex mode can easily met this requirement by dynamically declaring traffic direction in TDD slot, and adaptively allocating the sub channels. In this paper, we propose a adaptive slot and sub carrier allocation algorithm, that can be independently implemented in each cell of mobile communication network. Our analytical model is generalization of two cell concept to represent a multi cell model. Based on two cell concept four cases of interference pattern has been considered and simulated separately in presence of Additive White Gaussian Noise (AWGN and Rayleigh Channel. The simulated result suggests the requirement of approximately 9dB of Signal to Noise Ratio (SNR to maintain Bit Error Rate below 10-3. We also analyze the average delay incurred by the proposed algorithm in allocating resources.

  11. Research on the displacement control method of asynchronous modular contactor

    Science.gov (United States)

    He, Gong; Ming, Zong

    2017-01-01

    Ac contactor is a kind of low voltage electrical appliances with large usage and wide application. Because of the frequent operation, contactor life must be long enough to ensure the reliable operation of power system. The electrical life of the contactor, as the key to affect the service life of the contactor, is mainly affected by the arc developed in the breaking and closing course. This paper concentrates on a new type of asynchronous modular contactor. To get the contactor movement characteristics, the dynamic model of the electromagnetic system is established by MATLAB/SIMULINK. Then, according to the displacement curve of contactor, the breaking process and closing process is planned. The thought of closed loop control, by adjusting the parameters of PID controller, enables the contactor to operate as the planning displacement curve. In addition, to achieve no arc or micro arc breaking and no bounce or micro bounce closing , a displacement closed loop control system for contactor is designed.

  12. EPOS for Coordination of Asynchronous Sensor Webs Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop, integrate, and deploy software-based tools to coordinate asynchronous, distributed missions and optimize observation planning spanning simultaneous...

  13. Cross-Layer Quality-of-Service Analysis and Call Admission Control in the Uplink of CDMA Cellular Networks

    Directory of Open Access Journals (Sweden)

    Nie Chun

    2006-01-01

    Full Text Available This paper addresses cross-layer quality-of-service (QoS provisioning in the uplink of CDMA cellular mobile networks. Each mobile can take up to four UMTS traffic classes in our model. At the data link layer and the network layer, the QoS performances are defined in terms of signal-to-interference-plus-noise ratio and outage probability, and packet loss rate and delay, respectively. A call admission control scheme which fulfills these QoS metrics is developed to maximize the system capacity. The novelty of this paper is that the effect of the lengthening of the on-periods of non-real-time traffic classes is investigated by using the Go-Back-N automatic retransmission request mechanism with finite buffer size and limited number of retransmissions in the event of transmission errors. Simulation results for a specific example demonstrate the reasonableness of the analytical formulation.

  14. Throughput performance analysis of multirate, multiclass S-ALOHA OFFH-CDMA packet networks

    DEFF Research Database (Denmark)

    Raddo, Thiago R.; Sanches, Anderson L.; Borges, Ben Hur V

    2015-01-01

    In this paper, we propose a new throughput expression for multirate, multiclass slotted-ALOHA optical fast frequency hopping code-division multiple-access (OFFH-CDMA) packet networks considering a Poisson distribution for packet composite arrivals. We analyze the packet throughput performance...... of a three-class OFFH-CDMA network, where multirate transmissions are achieved via manipulation of the user's code parameters. It is shown that users transmitting at low rates interfere considerably in the performance of high rate users. Finally, we perform a validation procedure to demonstrate...

  15. An Asynchronous Cellular Automata-Based Adaptive Illumination Facility

    Science.gov (United States)

    Bandini, Stefania; Bonomi, Andrea; Vizzari, Giuseppe; Acconci, Vito

    The term Ambient Intelligence refers to electronic environments that are sensitive and responsive to the presence of people; in the described scenario the environment itself is endowed with a set of sensors (to perceive humans or other physical entities such as dogs, bicycles, etc.), interacting with a set of actuators (lights) that choose their actions (i.e. state of illumination) in an attempt improve the overall experience of these users. The model for the interaction and action of sensors and actuators is an asynchronous Cellular Automata (CA) with memory, supporting a self-organization of the system as a response to the presence and movements of people inside it. The paper will introduce the model, as well as an ad hoc user interface for the specification of the relevant parameters of the CA transition rule that determines the overall system behaviour.

  16. Asynchronous machine rotor speed estimation using a tabulated numerical approach

    Science.gov (United States)

    Nguyen, Huu Phuc; De Miras, Jérôme; Charara, Ali; Eltabach, Mario; Bonnet, Stéphane

    2017-12-01

    This paper proposes a new method to estimate the rotor speed of the asynchronous machine by looking at the estimation problem as a nonlinear optimal control problem. The behavior of the nonlinear plant model is approximated off-line as a prediction map using a numerical one-step time discretization obtained from simulations. At each time-step, the speed of the induction machine is selected satisfying the dynamic fitting problem between the plant output and the predicted output, leading the system to adopt its dynamical behavior. Thanks to the limitation of the prediction horizon to a single time-step, the execution time of the algorithm can be completely bounded. It can thus easily be implemented and embedded into a real-time system to observe the speed of the real induction motor. Simulation results show the performance and robustness of the proposed estimator.

  17. Implementing e-Transactions with Asynchronous Replication

    OpenAIRE

    Frolund, Svend; Guerraoui, Rachid

    2000-01-01

    An e-Transaction is one that executes exactly-once despite failures. This paper describes a distributed protocol that implements the abstraction of e-Transactionsin three-tier architectures. Three-tier architectures are typically Internet-oriented architectures, where the end-user interacts with front-end clients (e.g., browsers) that invoke middle-tier application servers (e.g., web servers) to access back-end databases. We implement the e-Transaction abstraction using an asynchronous replic...

  18. A Methodology for the Design and Verification of Globally Asynchronous/Locally Synchronous Architectures

    Science.gov (United States)

    Miller, Steven P.; Whalen, Mike W.; O'Brien, Dan; Heimdahl, Mats P.; Joshi, Anjali

    2005-01-01

    Recent advanced in model-checking have made it practical to formally verify the correctness of many complex synchronous systems (i.e., systems driven by a single clock). However, many computer systems are implemented by asynchronously composing several synchronous components, where each component has its own clock and these clocks are not synchronized. Formal verification of such Globally Asynchronous/Locally Synchronous (GA/LS) architectures is a much more difficult task. In this report, we describe a methodology for developing and reasoning about such systems. This approach allows a developer to start from an ideal system specification and refine it along two axes. Along one axis, the system can be refined one component at a time towards an implementation. Along the other axis, the behavior of the system can be relaxed to produce a more cost effective but still acceptable solution. We illustrate this process by applying it to the synchronization logic of a Dual Fight Guidance System, evolving the system from an ideal case in which the components do not fail and communicate synchronously to one in which the components can fail and communicate asynchronously. For each step, we show how the system requirements have to change if the system is to be implemented and prove that each implementation meets the revised system requirements through modelchecking.

  19. Asynchronous gaze-independent event-related potential-based brain-computer interface.

    Science.gov (United States)

    Aloise, Fabio; Aricò, Pietro; Schettini, Francesca; Salinari, Serenella; Mattia, Donatella; Cincotti, Febo

    2013-10-01

    In this study a gaze independent event related potential (ERP)-based brain computer interface (BCI) for communication purpose was combined with an asynchronous classifier endowed with dynamical stopping feature. The aim was to evaluate if and how the performance of such asynchronous system could be negatively affected in terms of communication efficiency and robustness to false positives during the intentional no-control state. The proposed system was validated with the participation of 9 healthy subjects. A comparison was performed between asynchronous and synchronous classification technique outputs while users were controlling the same gaze independent BCI interface. The performance of both classification techniques were assessed both off-line and on-line by means of the efficiency metric introduced by Bianchi et al. (2007). This latter metric allows to set a different misclassification cost for wrong classifications and abstentions. Robustness was evaluated as the rate of false positives occurring during voluntary no-control states. The asynchronous classifier did not exhibited significantly higher accuracy or lower error rate with respect to the synchronous classifier (accuracy: 74.66% versus 87.96%, error rate: 7.11% versus 12.04% respectively). However, the on-line and off-line analysis revealed that the communication efficiency was significantly improved (pinterface is a promising solution to be further explored in order to increase the general usability of ERP-based BCI systems designed for severely disabled people with an impairment of the voluntary control of eye movements. In fact, the asynchronous classifier can improve communication efficiency automatically adapting the number of stimulus repetitions to the current user's state and suspending the control if he/she does not intend to select an item. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Asynchronous P300-based brain-computer interface to control a virtual environment: initial tests on end users.

    Science.gov (United States)

    Aloise, Fabio; Schettini, Francesca; Aricò, Pietro; Salinari, Serenella; Guger, Christoph; Rinsma, Johanna; Aiello, Marco; Mattia, Donatella; Cincotti, Febo

    2011-10-01

    Motor disability and/or ageing can prevent individuals from fully enjoying home facilities, thus worsening their quality of life. Advances in the field of accessible user interfaces for domotic appliances can represent a valuable way to improve the independence of these persons. An asynchronous P300-based Brain-Computer Interface (BCI) system was recently validated with the participation of healthy young volunteers for environmental control. In this study, the asynchronous P300-based BCI for the interaction with a virtual home environment was tested with the participation of potential end-users (clients of a Frisian home care organization) with limited autonomy due to ageing and/or motor disabilities. System testing revealed that the minimum number of stimulation sequences needed to achieve correct classification had a higher intra-subject variability in potential end-users with respect to what was previously observed in young controls. Here we show that the asynchronous modality performed significantly better as compared to the synchronous mode in continuously adapting its speed to the users' state. Furthermore, the asynchronous system modality confirmed its reliability in avoiding misclassifications and false positives, as previously shown in young healthy subjects. The asynchronous modality may contribute to filling the usability gap between BCI systems and traditional input devices, representing an important step towards their use in the activities of daily living.

  1. An efficient algorithm for computing attractors of synchronous and asynchronous Boolean networks.

    Science.gov (United States)

    Zheng, Desheng; Yang, Guowu; Li, Xiaoyu; Wang, Zhicai; Liu, Feng; He, Lei

    2013-01-01

    Biological networks, such as genetic regulatory networks, often contain positive and negative feedback loops that settle down to dynamically stable patterns. Identifying these patterns, the so-called attractors, can provide important insights for biologists to understand the molecular mechanisms underlying many coordinated cellular processes such as cellular division, differentiation, and homeostasis. Both synchronous and asynchronous Boolean networks have been used to simulate genetic regulatory networks and identify their attractors. The common methods of computing attractors are that start with a randomly selected initial state and finish with exhaustive search of the state space of a network. However, the time complexity of these methods grows exponentially with respect to the number and length of attractors. Here, we build two algorithms to achieve the computation of attractors in synchronous and asynchronous Boolean networks. For the synchronous scenario, combing with iterative methods and reduced order binary decision diagrams (ROBDD), we propose an improved algorithm to compute attractors. For another algorithm, the attractors of synchronous Boolean networks are utilized in asynchronous Boolean translation functions to derive attractors of asynchronous scenario. The proposed algorithms are implemented in a procedure called geneFAtt. Compared to existing tools such as genYsis, geneFAtt is significantly [Formula: see text] faster in computing attractors for empirical experimental systems. The software package is available at https://sites.google.com/site/desheng619/download.

  2. Characterization and synthesis of a 32-bit asynchronous microprocessor in synchronous reconfigurable devices

    Directory of Open Access Journals (Sweden)

    Adrian Pedroza de la Crúz

    2015-10-01

    Full Text Available This paper presents the design, implementation, and experimental results of 32-bit asynchronous microprocessor developed in a synchronous reconfigurable device (FPGA, taking advantage of a hard macro. It has support for floating point operations, such as addition, subtraction, and multiplication, and is based on the IEEE 754-2008 standard with 32-bit simple precision. This work describes the different blocks of the microprocessors as delay modules, needed to implement a Self-Timed (ST protocol in a synchronous system, and the operational analysis of the asynchronous central unit, according to the developed occupations and speeds. The ST control is based on a micropipeline used as a centralized generator of activation signals that permit the performance of the operations in the microprocessor without the need of a global clock. This work compares the asynchronous microprocessor with a synchronous version. The parameters evaluated are power consumption, area, and speed. Both circuits were designed and implemented in an FPGA Virtex 5. The performance obtained was 4 MIPS for the asynchronous microprocessor against 1.6 MIPS for the synchronous.

  3. Two Studies Examining Argumentation in Asynchronous Computer Mediated Communication

    Science.gov (United States)

    Joiner, Richard; Jones, Sarah; Doherty, John

    2008-01-01

    Asynchronous computer mediated communication (CMC) would seem to be an ideal medium for supporting development in student argumentation. This paper investigates this assumption through two studies. The first study compared asynchronous CMC with face-to-face discussions. The transactional and strategic level of the argumentation (i.e. measures of…

  4. Considerations regarding asynchronous motor rotor parameters determination by FEM

    Directory of Open Access Journals (Sweden)

    Olivian Chiver

    2010-12-01

    Full Text Available The paper presents some considerations about asynchronous motor rotor parameters determination, using software based on finite elements method (FEM. For this, 2D magnetostatic and time harmonic analysis will be realized, at different frequencies, in case of a three phase asynchronous motor.

  5. Integrating Asynchronous Digital Design Into the Computer Engineering Curriculum

    Science.gov (United States)

    Smith, S. C.; Al-Assadi, W. K.; Di, J.

    2010-01-01

    As demand increases for circuits with higher performance, higher complexity, and decreased feature size, asynchronous (clockless) paradigms will become more widely used in the semiconductor industry, as evidenced by the International Technology Roadmap for Semiconductors' (ITRS) prediction of a likely shift from synchronous to asynchronous design…

  6. Designing Asynchronous Circuits for Low Power: An IFIR Filter

    DEFF Research Database (Denmark)

    Nielsen, Lars Skovby; Sparsø, Jens

    1999-01-01

    This paper addresses the design of asynchronous circuits for low power through an example: a filter bank for a digital hearing aid. The asynchronous design re-implements an existing synchronous circuit which is used in a commercial product. For comparison, both designs have been fabricated...

  7. Multilevel LDPC Codes Design for Multimedia Communication CDMA System

    Directory of Open Access Journals (Sweden)

    Hou Jia

    2004-01-01

    Full Text Available We design multilevel coding (MLC with a semi-bit interleaved coded modulation (BICM scheme based on low density parity check (LDPC codes. Different from the traditional designs, we joined the MLC and BICM together by using the Gray mapping, which is suitable to transmit the data over several equivalent channels with different code rates. To perform well at signal-to-noise ratio (SNR to be very close to the capacity of the additive white Gaussian noise (AWGN channel, random regular LDPC code and a simple semialgebra LDPC (SA-LDPC code are discussed in MLC with parallel independent decoding (PID. The numerical results demonstrate that the proposed scheme could achieve both power and bandwidth efficiency.

  8. Speech coding technology in CDMA mobile system and its implementation

    Science.gov (United States)

    Liu, Lan; Wu, Wei

    2004-03-01

    The fundamental of QCELP speech coding technology is introduced. According to the features of TMS320C54X family DSP of TI Inc., the implementation approach of QCELP speech coding with fixed-point DSP (digital signal processor) is presented.

  9. A newly proposed disease condition produced by light exposure during night: asynchronization.

    Science.gov (United States)

    Kohyama, Jun

    2009-04-01

    The bedtime of preschoolers/pupils/students in Japan has become progressively later with the result sleep duration has become progressively shorter. With these changes, more than half of the preschoolers/pupils/students in Japan recently have complained of daytime sleepiness, while approximately one quarter of junior and senior high school students in Japan reportedly suffer from insomnia. These preschoolers/pupils/students may be suffering from behaviorally induced insufficient sleep syndrome due to inadequate sleep hygiene. If this diagnosis is correct, they should be free from these complaints after obtaining sufficient sleep by avoiding inadequate sleep hygiene. However, such a therapeutic approach often fails. Although social factors are often involved in these sleep disturbances, a novel clinical notion--asynchronization--can further a deeper understanding of the pathophysiology of these disturbances. The essence of asynchronization is a disturbance in various aspects (e.g., cycle, amplitude, phase and interrelationship) of the biological rhythms that normally exhibit circadian oscillation, presumably involving decreased activity of the serotonergic system. The major trigger of asynchronization is hypothesized to be a combination of light exposure during the night and a lack of light exposure in the morning. In addition to basic principles of morning light and an avoidance of nocturnal light exposure, presumable potential therapeutic approaches for asynchronization involve both conventional ones (light therapy, medications (hypnotics, antidepressants, melatonin, vitamin B12), physical activation, chronotherapy) and alternative ones (kampo, pulse therapy, direct contact, control of the autonomic nervous system, respiration (qigong, tanden breathing), chewing, crawling). A morning-type behavioral preference is described in several of the traditional textbooks for good health. The author recommends a morning-type behavioral lifestyle as a way to reduce

  10. A parallel asynchronous decomposition for on-line contingency planning

    Energy Technology Data Exchange (ETDEWEB)

    Ramesh, V.C. [Illinois Inst. of Tech., Chicago, IL (United States). Electrical and Computer Engineering Dept.; Talukdar, S.N. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Engineering Design Research Center

    1995-12-31

    Traditional formulations of security-constrained-optimal-power-flows represent contingencies by hard constraints. The disadvantages are four-fold. First, the conflicts among contingencies must be arbitrated apriori, before their effects are known. Second, the feasible region shrinks with increase in the number of contingencies. Third, computational time increases with the number of contingencies. Fourth, hard constraints provide poor models of fuzzy quantities such as equipment ratings and operating guidelines. This paper develops a modeling framework without these disadvantages. Specifically, it allows for soft constraints and always has feasible solutions. The effects of conflicts among contingencies are displayed so system operators can arbitrate them in an informed manner. Moreover, each contingency can be handled asynchronously and in parallel. In other words, the computational time, for handling an arbitrarily large number of contingencies, remains the same as for performing an optimal power flow without any contingencies (provided that a computer is dedicated to each contingency).

  11. A parallel asynchronous decomposition for on-line contingency planning

    Energy Technology Data Exchange (ETDEWEB)

    Ramesh, V.C. [Illinois Inst. of Tech., Chicago, IL (United States). Electrical and Computer Engineering Dept.; Talukdar, S.N. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Engineering Design Research Center

    1996-02-01

    Traditional formulations of security-constrained-optimal-power-flows represent contingencies by hard constraints. The disadvantages are four-fold. First, the conflicts among contingencies must be arbitrated a priori, before their effects are known. Second, the feasible region shrinks with increase in the number of contingencies. Third, computational time increases with the number of contingencies. Fourth, hard constraints provide poor models of fuzzy quantities such as equipment ratings and operating guidelines. This paper develops a modeling framework without these disadvantages. Specifically, it allows for soft constraints and always has feasible solutions. The effects of conflicts among contingencies are displayed so system operators can arbitrate them in an informed manner. Moreover, each contingency can be handled asynchronously and in parallel. In other words, the computational time, for handling an arbitrarily large number of contingencies, remains the same as for performing an optimal power flow without any contingencies (provided that a computer is dedicated to each contingency).

  12. Sideband-Harmonic Instability of Paralleled Inverters with Asynchronous Carriers

    DEFF Research Database (Denmark)

    Yang, Dongsheng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Paralleled inverters with asynchronous carriers are increasingly emerging into renewable power plants and other power-electronic-based power systems. The sideband harmonics resulting from the pulse width modulation tend to be different from one inverter to another, which may trigger sideband-harmonic...... resonances among the paralleled inverters. To address the sideband-harmonic instability, the nonlinearity of the digital pulse width modulator is analyzed first in this paper based on the harmonic balance principle. It is revealed that the dynamic sideband components corresponding to a given small......-signal perturbation can be far below the Nyquist frequency, and they may not be effectively attenuated by anti-aliasing filters. A multi-frequency impedance model is then developed for the inverter, which characterizes the dynamic coupling between the perturbed frequency component and the sideband frequency component...

  13. Indoor Positioning for Smartphones Using Asynchronous Ultrasound Trilateration

    Directory of Open Access Journals (Sweden)

    James D. Carswell

    2013-06-01

    Full Text Available Modern smartphones are a great platform for Location Based Services (LBS. While outdoor LBS for smartphones has proven to be very successful, indoor LBS for smartphones has not yet fully developed due to the lack of an accurate positioning technology. In this paper we present an accurate indoor positioning approach for commercial off-the-shelf (COTS smartphones that uses the innate ability of mobile phones to produce ultrasound, combined with Time-Difference-of-Arrival (TDOA asynchronous trilateration. We evaluate our indoor positioning approach by describing its strengths and weaknesses, and determine its absolute accuracy. This is accomplished through a range of experiments that involve variables such as position of control point microphones, position of phone within the room, direction speaker is facing and presence of user in the signal path. Test results show that our Lok8 (locate mobile positioning system can achieve accuracies better than 10 cm in a real-world environment.

  14. Realization of station for testing asynchronous three-phase motors

    Science.gov (United States)

    Wróbel, A.; Surma, W.

    2016-08-01

    Nowadays, you cannot imagine the construction and operation of machines without the use of electric motors [13-15]. The proposed position is designed to allow testing of asynchronous three-phase motors. The position consists of a tested engine and the engine running as a load, both engines combined with a mechanical clutch [2]. The value of the load is recorded by measuring shaft created with Strain Gauge Bridge. This concept will allow to study the basic parameters of the engines, visualization motor parameters both vector and scalar controlled, during varying load drive system. In addition, registration during the variable physical parameters of the working electric motor, controlled by a frequency converter or controlled by a contactor will be possible. Position is designed as a teaching and research position to characterize the engines. It will be also possible selection of inverter parameters.

  15. Vector control structure of an asynchronous motor at maximum torque

    Science.gov (United States)

    Chioncel, C. P.; Tirian, G. O.; Gillich, N.; Raduca, E.

    2016-02-01

    Vector control methods offer the possibility to gain high performance, being widely used. Certain applications require an optimum control in limit operating conditions, as, at maximum torque, that is not always satisfied. The paper presents how the voltage and the frequency for an asynchronous machine (ASM) operating at variable speed are determinate, with an accent on the method that keeps the rotor flux constant. The simulation analyses consider three load types: variable torque and speed, variable torque and constant speed, constant torque and variable speed. The final values of frequency and voltage are obtained through the proposed control schemes with one controller using the simulation language based on the Maple module. The dynamic analysis of the system is done for the case with P and PI controller and allows conclusions on the proposed method, which can have different applications, as the ASM in wind turbines.

  16. Multirate IP traffic transmission in flexible access networks based on optical FFH-CDMA

    DEFF Research Database (Denmark)

    Raddo, Thiago R.; Sanches, Anderson L.; Tafur Monroy, Idelfonso

    2016-01-01

    In this paper, we propose a new IP transmission architecture over optical fast frequency hopping code-division multiple-access (OFFH-CDMA) network capable of supporting multirate transmissions for applications in flexible optical access networks. The proposed network architecture is independent...

  17. Low Complexity Iterative Joint Channel Estimation and Multiuser Detection for DS-CDMA

    DEFF Research Database (Denmark)

    Christensen, Søren Skovgård; Kocian, Alexander; Fleury, Bernard Henri

    2004-01-01

    Previously the SAGE algorithm was applied to sub-optimal yet efficient Joint data Detection and channel Estimation (JDE) for DS-CDMA of moderate time complexity. Modifying the expectation and maximization steps of the SAGE-JDE scheme, it is possible to obtain an efficient receiver architecture...

  18. Load control strategies in 2G mobile network for W-CDMA radio ...

    African Journals Online (AJOL)

    Network planning requires a faithful analysis of each individual cell's capacity. In this paper, we examine load control equations as a resource allocation tool to analyse cell capacity for the uplink and downlink of Wideband Code Division Multiple Access (W-CDMA) networks. In the uplink, the noise rise is a parameter of ...

  19. Frog: Asynchronous Graph Processing on GPU with Hybrid Coloring Model

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Xuanhua; Luo, Xuan; Liang, Junling; Zhao, Peng; Di, Sheng; He, Bingsheng; Jin, Hai

    2018-01-01

    GPUs have been increasingly used to accelerate graph processing for complicated computational problems regarding graph theory. Many parallel graph algorithms adopt the asynchronous computing model to accelerate the iterative convergence. Unfortunately, the consistent asynchronous computing requires locking or atomic operations, leading to significant penalties/overheads when implemented on GPUs. As such, coloring algorithm is adopted to separate the vertices with potential updating conflicts, guaranteeing the consistency/correctness of the parallel processing. Common coloring algorithms, however, may suffer from low parallelism because of a large number of colors generally required for processing a large-scale graph with billions of vertices. We propose a light-weight asynchronous processing framework called Frog with a preprocessing/hybrid coloring model. The fundamental idea is based on Pareto principle (or 80-20 rule) about coloring algorithms as we observed through masses of realworld graph coloring cases. We find that a majority of vertices (about 80%) are colored with only a few colors, such that they can be read and updated in a very high degree of parallelism without violating the sequential consistency. Accordingly, our solution separates the processing of the vertices based on the distribution of colors. In this work, we mainly answer three questions: (1) how to partition the vertices in a sparse graph with maximized parallelism, (2) how to process large-scale graphs that cannot fit into GPU memory, and (3) how to reduce the overhead of data transfers on PCIe while processing each partition. We conduct experiments on real-world data (Amazon, DBLP, YouTube, RoadNet-CA, WikiTalk and Twitter) to evaluate our approach and make comparisons with well-known non-preprocessed (such as Totem, Medusa, MapGraph and Gunrock) and preprocessed (Cusha) approaches, by testing four classical algorithms (BFS, PageRank, SSSP and CC). On all the tested applications and

  20. An Asynchronous Low Power and High Performance VLSI Architecture for Viterbi Decoder Implemented with Quasi Delay Insensitive Templates.

    Science.gov (United States)

    Devi, T Kalavathi; Palaniappan, Sakthivel

    2015-01-01

    Convolutional codes are comprehensively used as Forward Error Correction (FEC) codes in digital communication systems. For decoding of convolutional codes at the receiver end, Viterbi decoder is often used to have high priority. This decoder meets the demand of high speed and low power. At present, the design of a competent system in Very Large Scale Integration (VLSI) technology requires these VLSI parameters to be finely defined. The proposed asynchronous method focuses on reducing the power consumption of Viterbi decoder for various constraint lengths using asynchronous modules. The asynchronous designs are based on commonly used Quasi Delay Insensitive (QDI) templates, namely, Precharge Half Buffer (PCHB) and Weak Conditioned Half Buffer (WCHB). The functionality of the proposed asynchronous design is simulated and verified using Tanner Spice (TSPICE) in 0.25 µm, 65 nm, and 180 nm technologies of Taiwan Semiconductor Manufacture Company (TSMC). The simulation result illustrates that the asynchronous design techniques have 25.21% of power reduction compared to synchronous design and work at a speed of 475 MHz.

  1. An Asynchronous Low Power and High Performance VLSI Architecture for Viterbi Decoder Implemented with Quasi Delay Insensitive Templates

    Directory of Open Access Journals (Sweden)

    T. Kalavathi Devi

    2015-01-01

    Full Text Available Convolutional codes are comprehensively used as Forward Error Correction (FEC codes in digital communication systems. For decoding of convolutional codes at the receiver end, Viterbi decoder is often used to have high priority. This decoder meets the demand of high speed and low power. At present, the design of a competent system in Very Large Scale Integration (VLSI technology requires these VLSI parameters to be finely defined. The proposed asynchronous method focuses on reducing the power consumption of Viterbi decoder for various constraint lengths using asynchronous modules. The asynchronous designs are based on commonly used Quasi Delay Insensitive (QDI templates, namely, Precharge Half Buffer (PCHB and Weak Conditioned Half Buffer (WCHB. The functionality of the proposed asynchronous design is simulated and verified using Tanner Spice (TSPICE in 0.25 µm, 65 nm, and 180 nm technologies of Taiwan Semiconductor Manufacture Company (TSMC. The simulation result illustrates that the asynchronous design techniques have 25.21% of power reduction compared to synchronous design and work at a speed of 475 MHz.

  2. DNA strand breaks are not induced in human cells exposed to 2.1425 GHz band CW and W-CDMA modulated radiofrequency fields allocated to mobile radio base stations.

    Science.gov (United States)

    Sakuma, N; Komatsubara, Y; Takeda, H; Hirose, H; Sekijima, M; Nojima, T; Miyakoshi, J

    2006-01-01

    We conducted a large-scale in vitro study focused on the effects of low level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system in order to test the hypothesis that modulated RF fields may act as a DNA damaging agent. First, we evaluated the responses of human cells to microwave exposure at a specific absorption rate (SAR) of 80 mW/kg, which corresponds to the limit of the average whole body SAR for general public exposure defined as a basic restriction in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Second, we investigated whether continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) modulated signal RF fields at 2.1425 GHz induced different levels of DNA damage. Human glioblastoma A172 cells and normal human IMR-90 fibroblasts from fetal lungs were exposed to mobile communication frequency radiation to investigate whether such exposure produced DNA strand breaks in cell culture. A172 cells were exposed to W-CDMA radiation at SARs of 80, 250, and 800 mW/kg and CW radiation at 80 mW/kg for 2 and 24 h, while IMR-90 cells were exposed to both W-CDMA and CW radiations at a SAR of 80 mW/kg for the same time periods. Under the same RF field exposure conditions, no significant differences in the DNA strand breaks were observed between the test groups exposed to W-CDMA or CW radiation and the sham exposed negative controls, as evaluated immediately after the exposure periods by alkaline comet assays. Our results confirm that low level exposures do not act as a genotoxicant up to a SAR of 800 mW/kg.

  3. A cost-effective differential mobility analyzer (cDMA) for multiple DMA column applications

    Energy Technology Data Exchange (ETDEWEB)

    Mei, F.; Fu, H.; Chen, D.-R.

    2011-05-04

    In aerosol research and applications, a differential mobility analyzer (DMA) is now considered the standard tool for sizing and classifying monodisperse particles in the sub-micrometer and nanometer size ranges. However, DMA application at the pilot or industrial production scale remains infeasible because of the low mass throughput. A simple way to scale up DMA operation is to use multiple DMA columns. The manufacture and maintenance costs of existing DMAs, however, limit such a scale-up. A cost-effective DMA column (named cDMA) has thus been developed in this work to address the above issue. To reduce its manufacturing cost, the prototype was constructed using parts requiring little machining. The cDMA column was also designed for easy maintenance and easy variation of the classification length for any application-specified size range. In this study, prototypes with two particle classification lengths, 1.75 and 4.50 cm, were constructed and their performance was experimentally evaluated at sheath-to-aerosol flowrate ratios of 5:1, 10:1, and 15:1 via the tandem DMA (TDMA) technique. It was concluded that both prototype cDMAs, operated at a sheath/aerosol flowrate ratio less than 15:1 and with a polydisperse aerosol flowrate of 1.0 lpm, achieved sizing resolution comparable to that offered by Nano-DMA. The longer cDMA had comparable transmission efficiency to that of Nano-DMA, and the shorter cDMA exceeded the performance of Nano-DMA. Hence, the cDMA with the shorter (1.75 cm) classification length is better suited for the characterization of macromolecular samples.

  4. Dynamic quality of service differentiation using fixed code weight in optical CDMA networks

    Science.gov (United States)

    Kakaee, Majid H.; Essa, Shawnim I.; Abd, Thanaa H.; Seyedzadeh, Saleh

    2015-11-01

    The emergence of network-driven applications, such as internet, video conferencing, and online gaming, brings in the need for a network the environments with capability of providing diverse Quality of Services (QoS). In this paper, a new code family of novel spreading sequences, called a Multi-Service (MS) code, has been constructed to support multiple services in Optical- Code Division Multiple Access (CDMA) system. The proposed method uses fixed weight for all services, however reducing the interfering codewords for the users requiring higher QoS. The performance of the proposed code is demonstrated using mathematical analysis. It shown that the total number of served users with satisfactory BER of 10-9 using NB=2 is 82, while they are only 36 and 10 when NB=3 and 4 respectively. The developed MS code is compared with variable-weight codes such as Variable Weight-Khazani Syed (VW-KS) and Multi-Weight-Random Diagonal (MW-RD). Different numbers of basic users (NB) are used to support triple-play services (audio, data and video) with different QoS requirements. Furthermore, reference to the BER of 10-12, 10-9, and 10-3 for video, data and audio, respectively, the system can support up to 45 total users. Hence, results show that the technique can clearly provide a relative QoS differentiation with lower value of basic users can support larger number of subscribers as well as better performance in terms of acceptable BER of 10-9 at fixed code weight.

  5. Error characterization for asynchronous computations: Proxy equation approach

    Science.gov (United States)

    Sallai, Gabriella; Mittal, Ankita; Girimaji, Sharath

    2017-11-01

    Numerical techniques for asynchronous fluid flow simulations are currently under development to enable efficient utilization of massively parallel computers. These numerical approaches attempt to accurately solve time evolution of transport equations using spatial information at different time levels. The truncation error of asynchronous methods can be divided into two parts: delay dependent (EA) or asynchronous error and delay independent (ES) or synchronous error. The focus of this study is a specific asynchronous error mitigation technique called proxy-equation approach. The aim of this study is to examine these errors as a function of the characteristic wavelength of the solution. Mitigation of asynchronous effects requires that the asynchronous error be smaller than synchronous truncation error. For a simple convection-diffusion equation, proxy-equation error analysis identifies critical initial wave-number, λc. At smaller wave numbers, synchronous error are larger than asynchronous errors. We examine various approaches to increase the value of λc in order to improve the range of applicability of proxy-equation approach.

  6. Commande adaptive d'une machine asynchrone

    OpenAIRE

    Slama-Belkhodja, I.; De Fornel, B.

    1996-01-01

    Cat article décrit une stratégie de commande adaptive indirecte à Placement de Pôles (PP), appliquée à la commande en vitesse d'une machine asynchrone alimentée par un ensemble hacheur-filtre-onduleur de tension. L'algorithme des Moindres Carrés Récursifs (MCR) est utilisé pour l'identification des modèles de comportement type entrées/sorties. Un intérêt particulier est porté à la mise en oeuvre de cet algorithme et à la discussion de ses résultats, tenant compte des erreurs de modélisation e...

  7. Delay-bounded semi-reliable vital sign transmission protocol for mobile telemedicine over a CDMA 1x EV-DO network.

    Science.gov (United States)

    Lee, Tong H; Yoo, Sun K

    2008-04-01

    The reliable and instant transmission of vital signs is important for remote time-critical patient care through a telemedicine system. However, sometimes the reliability and instantaneity conditions cannot be satisfied simultaneously under a high-noise mobile network, because they are reciprocal to each other. In this paper, the vital sign transmission protocol (VSTP) running over a CDMA 1x EVDO (Code Division Multiple Access 1x Evolution Data Only) mobile network is proposed to comply with both the reliability and instantaneity requirements. The switching buffer management scheme is combined with a hybrid error control scheme, consisting of forward error correction (FEC) and automatic repeat request (ARQ). The CDMA 1x EVDO mobile network is modeled by two states using the Markov wireless channel model to test transmission performance under diverse network conditions. Throughout the noisy environment simulation, the performance of the VSTP is compared with the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) to demonstrate its efficacy over error-prone mobile network.

  8. Asynchronous Magnetic Bead Rotation (AMBR Microviscometer for Label-Free DNA Analysis

    Directory of Open Access Journals (Sweden)

    Yunzi Li

    2014-03-01

    Full Text Available We have developed a label-free viscosity-based DNA detection system, using paramagnetic beads as an asynchronous magnetic bead rotation (AMBR microviscometer. We have demonstrated experimentally that the bead rotation period is linearly proportional to the viscosity of a DNA solution surrounding the paramagnetic bead, as expected theoretically. Simple optical measurement of asynchronous microbead motion determines solution viscosity precisely in microscale volumes, thus allowing an estimate of DNA concentration or average fragment length. The response of the AMBR microviscometer yields reproducible measurement of DNA solutions, enzymatic digestion reactions, and PCR systems at template concentrations across a 5000-fold range. The results demonstrate the feasibility of viscosity-based DNA detection using AMBR in microscale aqueous volumes.

  9. Synchronous and asynchronous detection of ultra-law light levels using CMOS-compatible semiconductor technologies

    OpenAIRE

    Lotto, Christian; Seitz, Peter; Charbon, Edoardo; Enz, Christian; Farine, Pierre-André

    2011-01-01

    This work presents significant improvements of noise performance in synchronous CMOS image sensors and in asynchronous energy-sensitive singlephoton X-ray imaging systems. A detailed analysis of synchronous CMOS low-noise image sensors using conventional architectures reveals room for potential noise performance improvements, namely noise in switched-capacitor column-parallel amplifiers as well as imperfections in the low-pass filtering properties provided by such switched-capacitor amplifier...

  10. Verification and Planning for Stochastic Processes with Asynchronous Events

    National Research Council Canada - National Science Library

    Younes, Hakan L

    2005-01-01

    .... The most common assumption is that of history-independence: the Markov assumption. In this thesis, the author considers the problems of verification and planning for stochastic processes with asynchronous events, without relying on the Markov assumption...

  11. Control of asynchronous motors. Volume 1. Modeling, vectorial control and direct torque control; Commande des moteurs asynchrones. Volume 1. Modelisation, controle vectoriel et DTC

    Energy Technology Data Exchange (ETDEWEB)

    Canudas de Wit, C. [Ecole Nationale Superieure d' Ingenieurs de Genie Chimique, ENSIGC, 31 - Toulouse (France)

    2000-07-01

    This first volume deals with the problems of control of asynchronous motors in industrial environments: industrial environment, variable speed, asynchronous motors and power supplies, modeling, direct torque control laws, control by controlled limit cycles under frequency constraints. (J.S.)

  12. Experimental 3D Asynchronous Field Programmable Gate Array (FPGA)

    Science.gov (United States)

    2015-03-01

    EXPERIMENTAL 3D ASYNCHRONOUS FIELD PROGRAMMABLE GATE ARRAY ( FPGA ) CORNELL UNIVERSITY MARCH 2015 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC...From - To) OCT 2011 – OCT 2014 4. TITLE AND SUBTITLE EXPERIMENTAL 3D ASYNCHRONOUS FIELD PROGRAMMABLE GATE ARRAY ( FPGA ) 5a. CONTRACT NUMBER...in collaboration with Albany’s College of Nanoscale Science and Engineering. 15. SUBJECT TERMS 3D Technology, vertical interconnects, AFPGA, FPGA

  13. A Scalable Multicore Architecture With Heterogeneous Memory Structures for Dynamic Neuromorphic Asynchronous Processors (DYNAPs).

    Science.gov (United States)

    Moradi, Saber; Qiao, Ning; Stefanini, Fabio; Indiveri, Giacomo

    2018-02-01

    Neuromorphic computing systems comprise networks of neurons that use asynchronous events for both computation and communication. This type of representation offers several advantages in terms of bandwidth and power consumption in neuromorphic electronic systems. However, managing the traffic of asynchronous events in large scale systems is a daunting task, both in terms of circuit complexity and memory requirements. Here, we present a novel routing methodology that employs both hierarchical and mesh routing strategies and combines heterogeneous memory structures for minimizing both memory requirements and latency, while maximizing programming flexibility to support a wide range of event-based neural network architectures, through parameter configuration. We validated the proposed scheme in a prototype multicore neuromorphic processor chip that employs hybrid analog/digital circuits for emulating synapse and neuron dynamics together with asynchronous digital circuits for managing the address-event traffic. We present a theoretical analysis of the proposed connectivity scheme, describe the methods and circuits used to implement such scheme, and characterize the prototype chip. Finally, we demonstrate the use of the neuromorphic processor with a convolutional neural network for the real-time classification of visual symbols being flashed to a dynamic vision sensor (DVS) at high speed.

  14. Application of Artificial Intelligence Techniques for the Control of the Asynchronous Machine

    Directory of Open Access Journals (Sweden)

    F. Khammar

    2016-01-01

    Full Text Available The induction machine is experiencing a growing success for two decades by gradually replacing the DC machines and synchronous in many industrial applications. This paper is devoted to the study of advanced methods applied to the command of the asynchronous machine in order to obtain a system of control of high performance. While the criteria for response time, overtaking, and static error can be assured by the techniques of conventional control, the criterion of robustness remains a challenge for researchers. This criterion can be satisfied only by applying advanced techniques of command. After mathematical modeling of the asynchronous machine, it defines the control strategies based on the orientation of the rotor flux. The results of the different simulation tests highlight the properties of robustness of algorithms proposed and suggested to compare the different control strategies.

  15. An Asynchronous Multi-Sensor Micro Control Unit for Wireless Body Sensor Networks (WBSNs

    Directory of Open Access Journals (Sweden)

    Ching-Hsing Luo

    2011-07-01

    Full Text Available In this work, an asynchronous multi-sensor micro control unit (MCU core is proposed for wireless body sensor networks (WBSNs. It consists of asynchronous interfaces, a power management unit, a multi-sensor controller, a data encoder (DE, and an error correct coder (ECC. To improve the system performance and expansion abilities, the asynchronous interface is created for handshaking different clock domains between ADC and RF with MCU. To increase the use time of the WBSN system, a power management technique is developed for reducing power consumption. In addition, the multi-sensor controller is designed for detecting various biomedical signals. To prevent loss error from wireless transmission, use of an error correct coding technique is important in biomedical applications. The data encoder is added for lossless compression of various biomedical signals with a compression ratio of almost three. This design is successfully tested on a FPGA board. The VLSI architecture of this work contains 2.68-K gate counts and consumes power 496-μW at 133-MHz processing rate by using TSMC 0.13-μm CMOS process. Compared with the previous techniques, this work offers higher performance, more functions, and lower hardware cost than other micro controller designs.

  16. Blind Identification of the Scrambling Code of a Reverse Link CDMA2000 Transmission

    OpenAIRE

    Des Noes, Mathieu; Savin, Valentin; Brossier, Jean-Marc; Ros, Laurent

    2013-01-01

    International audience; Interference between macro and femtocells is an important issue for the development of CDMA2000 femtocell networks. More specifically, the reverse link signal of a macro UserEquipment may generate an unacceptable level of interference at the femto Base Station. To avoid this situation, interference mitigation techniques could be implemented. All the proposed techniques require to know the state of the scrambling code of the interferer in the reverse link. Unfortunately...

  17. Rapid, generalized adaptation to asynchronous audiovisual speech.

    Science.gov (United States)

    Van der Burg, Erik; Goodbourn, Patrick T

    2015-04-07

    The brain is adaptive. The speed of propagation through air, and of low-level sensory processing, differs markedly between auditory and visual stimuli; yet the brain can adapt to compensate for the resulting cross-modal delays. Studies investigating temporal recalibration to audiovisual speech have used prolonged adaptation procedures, suggesting that adaptation is sluggish. Here, we show that adaptation to asynchronous audiovisual speech occurs rapidly. Participants viewed a brief clip of an actor pronouncing a single syllable. The voice was either advanced or delayed relative to the corresponding lip movements, and participants were asked to make a synchrony judgement. Although we did not use an explicit adaptation procedure, we demonstrate rapid recalibration based on a single audiovisual event. We find that the point of subjective simultaneity on each trial is highly contingent upon the modality order of the preceding trial. We find compelling evidence that rapid recalibration generalizes across different stimuli, and different actors. Finally, we demonstrate that rapid recalibration occurs even when auditory and visual events clearly belong to different actors. These results suggest that rapid temporal recalibration to audiovisual speech is primarily mediated by basic temporal factors, rather than higher-order factors such as perceived simultaneity and source identity. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  18. Managing Asynchronous Data in ATLAS's Concurrent Framework

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00100895; The ATLAS collaboration; Baines, John; Bold, Tomasz; Calafiura, Paolo; Cranshaw, Jack; Dotti, Andrea; Farrell, Steven; Malon, David; Stewart, Graeme; Snyder, Scott; van Gemmeren, Peter; Tsulaia, Vakhtang; Wynne, Benjamin

    2016-01-01

    In order to be able to make effective use of emerging hardware, where the amount of memory available to any CPU is rapidly decreasing as the core count continues to rise, ATLAS has begun a migration to a concurrent, multi-threaded software framework, known as AthenaMT. Significant progress has been made in implementing AthenaMT - we can currently run realistic Geant4 simulations on massively concurrent machines. the migration of realistic prototypes of reconstruction workflows is more difficult, given the large amounts of legacy code and the complexity and challenges of reconstruction software. These types of workflows, however, are the types that will most benefit from the memory reduction features of a multi-threaded framework. One of the challenges that we will report on in this paper is the re-design and implementation of several key asynchronous technologies whose behaviour is radically different in a concurrent environment than in a serial one, namely the management of Conditions data and the Detector D...

  19. Asynchronous Forums in EAP: Assessment Issues

    Directory of Open Access Journals (Sweden)

    Sara Kol

    2008-06-01

    Full Text Available This paper reports on a pilot and a subsequent study that focused on the assessment of student writing in asynchronous text-stimulated forum discussions. The study, which was conducted in advanced English for Academic Purposes (EAP courses, aimed at determining suitable assessment criteria for written academic discussions. In addition, the study tapped student attitudes toward forums, checked the effect of forum participation on student writing, and characterized the text-stimulated forum discussions.Based on a content analysis of the pilot data, the constructs of reflection and interaction were selected as assessment criteria to be evaluated in the main study. These criteria were found to be usable but insufficient for student assessment in the EAP courses. A questionnaire showed that the student attitudes were positive and that most students felt that their writing improved, even though an analysis of language complexity showed no significant improvement. A qualitative analysis of the transcripts revealed deep student involvement with the content and with their peers as well as an academic register interspersed with conversational interactions.

  20. Lack of teratogenicity after combined exposure of pregnant mice to CDMA and WCDMA radiofrequency electromagnetic fields.

    Science.gov (United States)

    Lee, Hae-June; Lee, Jae-Seon; Pack, Jeong-Ki; Choi, Hyung-Do; Kim, Nam; Kim, Sung-Ho; Lee, Yun-Sil

    2009-11-01

    Concern about the possible adverse effects of radiofrequency (RF)-field exposure on public health has increased because of the extensive use of wireless mobile phones and other telecommunication devices in daily life. The murine fetus is a very sensitive indicator of the effects of stress or stimuli in the environment. Therefore, we investigated the teratogenic effects of multi-signal radiofrequency electromagnetic fields (RF EMFs) on mouse fetuses. Pregnant mice were simultaneously exposed to two types of RF signals, single code division multiple access (CDMA) and wideband code division multiple access (WCDMA). Mice received two 45-min RF-field exposures, separated by a 15-min interval, daily throughout the entire gestation period. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg. The animals were killed humanely on the 18th day of gestation and fetuses were examined for mortality, growth retardation, changes in head size and other morphological abnormalities. From the results, we report for the first time that simultaneous experimental exposure to CDMA and WCDMA RF EMFs did not cause any observable adverse effects on mouse fetuses.

  1. Performance evaluation of wavelet-based ECG compression algorithms for telecardiology application over CDMA network.

    Science.gov (United States)

    Kim, Byung S; Yoo, Sun K

    2007-09-01

    The use of wireless networks bears great practical importance in instantaneous transmission of ECG signals during movement. In this paper, three typical wavelet-based ECG compression algorithms, Rajoub (RA), Embedded Zerotree Wavelet (EZ), and Wavelet Transform Higher-Order Statistics Coding (WH), were evaluated to find an appropriate ECG compression algorithm for scalable and reliable wireless tele-cardiology applications, particularly over a CDMA network. The short-term and long-term performance characteristics of the three algorithms were analyzed using normal, abnormal, and measurement noise-contaminated ECG signals from the MIT-BIH database. In addition to the processing delay measurement, compression efficiency and reconstruction sensitivity to error were also evaluated via simulation models including the noise-free channel model, random noise channel model, and CDMA channel model, as well as over an actual CDMA network currently operating in Korea. This study found that the EZ algorithm achieves the best compression efficiency within a low-noise environment, and that the WH algorithm is competitive for use in high-error environments with degraded short-term performance with abnormal or contaminated ECG signals.

  2. The effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic fields on rat testicular function.

    Science.gov (United States)

    Lee, Hae-June; Jin, Yeung Bae; Kim, Tae-Hong; Pack, Jeong-Ki; Kim, Nam; Choi, Hyung-Do; Lee, Jae-Seon; Lee, Yun-Sil

    2012-05-01

    Wireless mobile phones and other telecommunication devices are used extensively in daily life. We therefore examined the effects of combined exposure to radiofrequency electromagnetic fields (RF-EMF) on rat testicular function, specifically with respect to sensitive processes such as spermatogenesis. Male rats were exposed to single code division multiple access (CDMA) and wideband code division multiple access (WCDMA) RF signals for 12 weeks. The RF exposure schedule comprised 45 min/day, 5 days/week for a total of 12 weeks. The whole-body average specific absorption rate (SAR) of CDMA and WCDMA was 2.0 W/kg each or 4.0 W/kg in total. We then investigated the correlates of testicular function such as sperm count in the cauda epididymis, testosterone concentration in the blood serum, malondialdehyde concentrations in the testes and epididymis, frequency of spermatogenesis stages, and appearance of apoptotic cells in the testes. We also immunoblotted for p53, bcl2, GADD45, cyclin G, and HSP70 in the testes of sham- and combined RF-exposed animals. Based on the results, we concluded that simultaneous exposure to CDMA and WCDMA RF-EMFs at 4.0 W/kg SAR did not have any observable adverse effects on rat spermatogenesis. Copyright © 2011 Wiley Periodicals, Inc.

  3. Robust transmission of packet-based H.264/AVC video with data partitioning over DS-CDMA wireless channels

    Science.gov (United States)

    Mantravadi, Anand V. S.; Bansal, Manu; Kondi, Lisimachos P.

    2006-01-01

    In this paper, we address the problem of robust transmission of packet based H.264/AVC video over direct sequence-code division multiple access (DS-CDMA) channels. H.264 based data partitioning is used to produce video packets of unequal importance with regards to their need in terms of the decoded video quality. In the proposed transmission system, the data partitioned video packets are packetized as per IP/UDP/RTP protocol stack and are sorted into different levels for giving unequal error protection (UEP) using Rate Compatible Punctured Convolutional (RCPC) codes. Constant size framing is done at the link layer and Cyclic Redundancy Check header (CRC) is attached for error detection. Link layer buffering and packet interleaving schemes are proposed to improve the efficiency of the system. A multipath Rayleigh fading channel with Additive White Gaussian Noise (AWGN) and interference from other users is considered at the physical layer. The link layer frames are channel encoded, spread and transmitted over the channel. The received data is despread/demodulated using the Auxiliary Vector (AV) filter or RAKE matched filter (RAKE-MF) receiver and subsequently channel and source decoded. Our experimental results show the effectiveness of using data partitioning for wireless transmissions when compared to the system not using data partitioning. Also the superior interference mitigation capabilities of AV receiver is shown in comparison to the RAKE-MF receiver.

  4. Synaptotagmin-7 is an asynchronous calcium sensor for synaptic transmission in neurons expressing SNAP-23.

    Science.gov (United States)

    Weber, Jens P; Toft-Bertelsen, Trine L; Mohrmann, Ralf; Delgado-Martinez, Ignacio; Sørensen, Jakob B

    2014-01-01

    Synchronization of neurotransmitter release with the presynaptic action potential is essential for maintaining fidelity of information transfer in the central nervous system. However, synchronous release is frequently accompanied by an asynchronous release component that builds up during repetitive stimulation, and can even play a dominant role in some synapses. Here, we show that substitution of SNAP-23 for SNAP-25 in mouse autaptic glutamatergic hippocampal neurons results in asynchronous release and a higher frequency of spontaneous release events (mEPSCs). Use of neurons from double-knock-out (SNAP-25, synaptotagmin-7) mice in combination with viral transduction showed that SNAP-23-driven release is triggered by endogenous synaptotagmin-7. In the absence of synaptotagmin-7 release became even more asynchronous, and the spontaneous release rate increased even more, indicating that synaptotagmin-7 acts to synchronize release and suppress spontaneous release. However, compared to synaptotagmin-1, synaptotagmin-7 is a both leaky and asynchronous calcium sensor. In the presence of SNAP-25, consequences of the elimination of synaptotagmin-7 were small or absent, indicating that the protein pairs SNAP-25/synaptotagmin-1 and SNAP-23/synaptotagmin-7 might act as mutually exclusive calcium sensors. Expression of fusion proteins between pHluorin (pH-sensitive GFP) and synaptotagmin-1 or -7 showed that vesicles that fuse using the SNAP-23/synaptotagmin-7 combination contained synaptotagmin-1, while synaptotagmin-7 barely displayed activity-dependent trafficking between vesicle and plasma membrane, implying that it acts as a plasma membrane calcium sensor. Overall, these findings support the idea of alternative syt∶SNARE combinations driving release with different kinetics and fidelity.

  5. Two-Particle Asynchronous Quantum Correlation: Wavefunction Collapse Acting as a Beamsplitter

    Science.gov (United States)

    Kowalski, F. V.; Browne, R. S.

    2016-03-01

    A two-body quantum correlation is calculated for a particle reflecting from a moving mirror. Correlated interference results when the incident and reflected particle substates and their associated mirror substates overlap. Using the Copenhagen interpretation of measurement, an asynchronous joint probability density (PDF), which is a function both of the different positions and different times at which the particle and mirror are measured, is derived assuming that no interaction occurs between each measurement. Measurement of the particle first, in the correlated interference region, results in a splitting of the mirror substate into ones which have and have not reflected the particle. An analog of the interference from the Doppler effect for only measurements of the particle (a marginal PDF), in this two-body system, is shown to be a consequence of the asynchronous measurement. The simplification obtained for a microscopic particle reflecting from a mesoscopic or macroscopic mirror is used to illustrate asynchronous correlation interferometry. In this case, the small displacement between these mirror states can yield negligible environmental decoherence times. In addition, interference of these mirror states does not vanish in the limit of large mirror mass due to the small momentum exchange in reflecting a microscopic particle.

  6. DIRECT FREQUENCY CONVERTER WITH ARTIFICIAL AND NATURAL COMMUTATION FOR BRUSHLESS ASYNCHRONIZED MACHINES

    Directory of Open Access Journals (Sweden)

    А.М. Galynovskiy

    2015-11-01

    Full Text Available The comparative analysis of direct frequency converters with artificial and natural- switching term of the cyclical control algorithm is presented; the recommendations for their using in brushless asynchronized machines with three-phase winding are developed. Converters with a limited number of full-controlled valves have large losses in safety circuits of gates, they can be used in system of automatic excitation control. The best quality of voltage and current load are provided by converters with natural commutation using modulated input voltage, the combined potential compounds windings supply and the combined method of thyristor controlling. When the load is divided into two three-phase groups, an even number of phases of the power supply for single phase of the load are applied the bridge converter circuit. Regulation of the load current is carried out by the excitation current of field exciters and by the control angle of thyristor. Converters can be used in high-power asynchronized motors and generators. In asynchronized compensators it is possible to use diode-thyristor converters without transmitting the control signals to the rotating part. The frequency converters without modulation of input voltage have the smallest increase in rated capacity of power supply. However, they have a low quality form of the output voltage at high power factor of load.

  7. IHadoop: Asynchronous iterations for MapReduce

    KAUST Repository

    Elnikety, Eslam Mohamed Ibrahim

    2011-11-01

    MapReduce is a distributed programming frame-work designed to ease the development of scalable data-intensive applications for large clusters of commodity machines. Most machine learning and data mining applications involve iterative computations over large datasets, such as the Web hyperlink structures and social network graphs. Yet, the MapReduce model does not efficiently support this important class of applications. The architecture of MapReduce, most critically its dataflow techniques and task scheduling, is completely unaware of the nature of iterative applications; tasks are scheduled according to a policy that optimizes the execution for a single iteration which wastes bandwidth, I/O, and CPU cycles when compared with an optimal execution for a consecutive set of iterations. This work presents iHadoop, a modified MapReduce model, and an associated implementation, optimized for iterative computations. The iHadoop model schedules iterations asynchronously. It connects the output of one iteration to the next, allowing both to process their data concurrently. iHadoop\\'s task scheduler exploits inter-iteration data locality by scheduling tasks that exhibit a producer/consumer relation on the same physical machine allowing a fast local data transfer. For those iterative applications that require satisfying certain criteria before termination, iHadoop runs the check concurrently during the execution of the subsequent iteration to further reduce the application\\'s latency. This paper also describes our implementation of the iHadoop model, and evaluates its performance against Hadoop, the widely used open source implementation of MapReduce. Experiments using different data analysis applications over real-world and synthetic datasets show that iHadoop performs better than Hadoop for iterative algorithms, reducing execution time of iterative applications by 25% on average. Furthermore, integrating iHadoop with HaLoop, a variant Hadoop implementation that caches

  8. Kalai-Smorodinsky bargaining solution for optimal resource allocation over wireless DS-CDMA visual sensor networks

    Science.gov (United States)

    Pandremmenou, Katerina; Kondi, Lisimachos P.; Parsopoulos, Konstantinos E.

    2012-01-01

    Surveillance applications usually require high levels of video quality, resulting in high power consumption. The existence of a well-behaved scheme to balance video quality and power consumption is crucial for the system's performance. In the present work, we adopt the game-theoretic approach of Kalai-Smorodinsky Bargaining Solution (KSBS) to deal with the problem of optimal resource allocation in a multi-node wireless visual sensor network (VSN). In our setting, the Direct Sequence Code Division Multiple Access (DS-CDMA) method is used for channel access, while a cross-layer optimization design, which employs a central processing server, accounts for the overall system efficacy through all network layers. The task assigned to the central server is the communication with the nodes and the joint determination of their transmission parameters. The KSBS is applied to non-convex utility spaces, efficiently distributing the source coding rate, channel coding rate and transmission powers among the nodes. In the underlying model, the transmission powers assume continuous values, whereas the source and channel coding rates can take only discrete values. Experimental results are reported and discussed to demonstrate the merits of KSBS over competing policies.

  9. Photonic analog-to-digital converter via asynchronous oversampling

    Science.gov (United States)

    Carver, Spencer; Reeves, Erin; Siahmakoun, Azad; Granieri, Sergio

    2012-06-01

    This paper presents a hybrid opto-electronic asynchronous delta-sigma modulator, implemented in the form of a fiber-optic Analog-to-Digital converter (ADC). This architecture was chosen for its independence of an external clock and ease of demodulation through a single low-pass filter stage. The fiber-optic prototype consists of an input laser (wavelength λ1) which is modulated with an input RF signal, a high-speed comparator circuit working as bi-stable quantizer, and a fiber-optic loop that includes a SOA and a band-pass filter that act as a leaky integrator. The fiber-optic loop acts as a fiber-ring resonator (FRR), and defines the resonance wavelength λ2 of the system. The gain within this loop is modified through cross-gain modulation (XGM) by the input wavelength λ1, and thus achieves the desired modulation effect. The proposed architecture has been constructed and characterized at a sampling rate of 15.4 MS/s processing input analog signals in the range of dc-3 MHz with a signal-to-noise ratio of 36 dB and an effective number of bits of 5.7.

  10. Obstacle avoidance in social groups: new insights from asynchronous models.

    Science.gov (United States)

    Croft, Simon; Budgey, Richard; Pitchford, Jonathan W; Wood, A Jamie

    2015-05-06

    For moving animals, the successful avoidance of hazardous obstacles is an important capability. Despite this, few models of collective motion have addressed the relationship between behavioural and social features and obstacle avoidance. We develop an asynchronous individual-based model for social movement which allows social structure within groups to be included. We assess the dynamics of group navigation and resulting collision risk in the context of information transfer through the system. In agreement with previous work, we find that group size has a nonlinear effect on collision risk. We implement examples of possible network structures to explore the impact social preferences have on collision risk. We show that any social heterogeneity induces greater obstacle avoidance with further improvements corresponding to groups containing fewer influential individuals. The model provides a platform for both further theoretical investigation and practical application. In particular, we argue that the role of social structures within bird flocks may have an important role to play in assessing the risk of collisions with wind turbines, but that new methods of data analysis are needed to identify these social structures. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  11. Performance Studies for Protection Against Asynchronous Dumps in the LHC

    CERN Document Server

    Kramer, T; Bracco, C; Goddard, B; Meddahi, M

    2010-01-01

    The LHC beam dump system has to safely dispose all beams in a wide energy range of 450 GeV to 7 TeV. A 3 ms abort gap in the beam structure for the switch-on of the extraction kicker field ideally allows a loss-free extraction under normal operating conditions. However, a low number of asynchronous beam aborts is to be expected from reliability calculations and from the first year's operational experience with the beam dump kickers. For such cases, MAD-X simulations including all optics and alignment errors have been performed to determine loss patterns around the LHC as a function of the position of the main protection elements in interaction region six. Special attention was paid to the beam load on the tungsten collimators which protect the triplets in the LHC experimental insertions, and the tracking results compared with semi-analytical numerical estimates. The simulations are also compared to the results of beam commissioning of these protection devices.

  12. Renewal Approach to the Analysis of the Asynchronous State for Coupled Noisy Oscillators

    CERN Document Server

    Farkhooi, Farzad

    2015-01-01

    We develop a framework in which the activity of nonlinear pulse-coupled oscillators is posed within the renewal theory. In this approach, the evolution of inter-event density allows for a self-consistent calculation that determines the asynchronous state and its stability. This framework, can readily be extended to the analysis of systems with more state variables. To exhibit this, we study a nonlinear pulse-coupled system, where couplings are dynamic and activity dependent. We investigate stability of this system and we show it undergoes a super-critical Hopf bifurcation to collective synchronization.

  13. Molecular mechanisms for synchronous, asynchronous, and spontaneous neurotransmitter release.

    Science.gov (United States)

    Kaeser, Pascal S; Regehr, Wade G

    2014-01-01

    Most neuronal communication relies upon the synchronous release of neurotransmitters, which occurs through synaptic vesicle exocytosis triggered by action potential invasion of a presynaptic bouton. However, neurotransmitters are also released asynchronously with a longer, variable delay following an action potential or spontaneously in the absence of action potentials. A compelling body of research has identified roles and mechanisms for synchronous release, but asynchronous release and spontaneous release are less well understood. In this review, we analyze how the mechanisms of the three release modes overlap and what molecular pathways underlie asynchronous and spontaneous release. We conclude that the modes of release have key fusion processes in common but may differ in the source of and necessity for Ca(2+) to trigger release and in the identity of the Ca(2+) sensor for release.

  14. A Loosely Synchronizing Asynchronous Router for TDM-Scheduled NOCs

    DEFF Research Database (Denmark)

    Kotleas, Ioannis; Humphreys, Dean; Sørensen, Rasmus Bo

    2014-01-01

    This paper presents an asynchronous router design for use in time-division-multiplexed (TDM) networks-on-chip. Unlike existing synchronous, mesochronous and asynchronous router designs with similar functionality, the router is able to silently skip over cycles/TDM-slots where no traffic...... is scheduled and hence avoid all switching activity in the idle links and router ports. In this way switching activity is reduced to the minimum possible amount. The fact that this relaxed synchronization is sufficient to implement TDM scheduling represents a contribution at the conceptual level. The idea can...... only be implemented using asynchronous circuit techniques. To this end, the paper explores the use of “click-element” templates. Click-element templates use only flipflops and conventional gates, and this greatly simplifies the design process when using conventional EDA tools and standard cell...

  15. Control algorithms for single inverter dual induction motor system applied to railway traction; Commande algorithmique d'un systeme mono-onduleur bimachine asynchrone destine a la traction ferroviaire

    Energy Technology Data Exchange (ETDEWEB)

    Pena Eguiluz, R.

    2002-11-15

    The goal of this work concerns the modelling and the behaviour characterisation of a single inverter dual induction motor system applied to a railway traction bogie (BB36000) in order to concept its control. First part of this job is dedicated to the detailed description of overall system. The influence analysis of the internal perturbations (motor parameters variation) and, external perturbations (pantograph detachment, adherence loss, stick-slip) of the system have made considering the field oriented control applied to each motor of the bogie (classical traction structure). vi In a second part, a novel propulsion structure is proposed. It is composed by a single pulse-width modulated two level voltage source inverter. It supplies two parallel connected induction motors, which generate the transmitted traction force to the bogie wheels. The locomotive case represents the common load for the two motors. Several co-operative control strategies (CS) are studied. They are: the mean CS, the double mean CS, the master - slave switched CS and, the mean differential CS. In addition, an appropriated electric modes observer structure for these different controls has studied. These controls have validated applying the perturbations to the models using the solver SABER. This special approach is equivalent to quasi-experimentation, because the mechanical and the electrical system components have modelled using MAST language and, the sample control has created by a C code programme in the SABER environment. Third part is dedicated to the mechanical sensor suppression and, its adaptation in the cooperative control strategies. The partial speed reconstruction methods are: the fundamental frequency relation, the mechanical Kalman filter, the variable structure observer and the MRAS. Finally, the hardware system configuration of the experimental realisation is described. (author)

  16. Spectral Subtraction Approach for Interference Reduction of MIMO Channel Wireless Systems

    Directory of Open Access Journals (Sweden)

    Tomohiro Ono

    2005-08-01

    Full Text Available In this paper, a generalized spectral subtraction approach for reducing additive impulsive noise, narrowband signals, white Gaussian noise and DS-CDMA interferences in MIMO channel DS-CDMA wireless communication systems is investigated. The interference noise reduction or suppression is essential problem in wireless mobile communication systems to improve the quality of communication. The spectrum subtraction scheme is applied to the interference noise reduction problems for noisy MIMO channel systems. The interferences in space and time domain signals can effectively be suppressed by selecting threshold values, and the computational load with the FFT is not large. Further, the fading effects of channel are compensated by spectral modification with the spectral subtraction process. In the simulations, the effectiveness of the proposed methods for the MIMO channel DS-CDMA is shown to compare with the conventional MIMO channel DS-CDMA.

  17. Asynchronous glaciations in arid continental climate

    Science.gov (United States)

    Batbaatar, Jigjidsurengiin; Gillespie, Alan R.; Fink, David; Matmon, Ari; Fujioka, Toshiyuki

    2018-02-01

    Mountain glaciers at ∼26-19 ka, during the global Last Glacial Maximum near the end of the last 105 yr glacial cycle, are commonly considered on the basis of dating and field mapping in several well-studied areas to have been the largest of the late Quaternary and to have advanced synchronously from region to region. However, a numerical sensitivity model (Rupper and Roe, 2008) predicts that the fraction of ablation due to melting varies across Central Asia in proportion to the annual precipitation. The equilibrium-line altitude of glaciers across this region likely varies accordingly: in high altitude, cold and arid regions sublimation can ablate most of the ice, whereas glaciers fed by high precipitation cannot ablate completely due to sublimation alone, but extend downhill until higher temperatures there cause them to melt. We have conducted field studies and 10Be dating at five glaciated sites along a precipitation gradient in Mongolia to test the Rupper/Roe model. The sites are located in nearby 1.875 × 1.875° cells of the Rupper/Roe model, each with a different melt fraction, in this little-studied region. The modern environment of the sites ranges from dry subhumid in the north (47.7° N) to arid in the south (45° N). Our findings show that the maximum local advances in the dry subhumid conditions predated the global Last Glacial Maximum and were likely from MIS 3. However, we also found that at ∼8-7 ka a cirque glacier in one mountain range of the arid Gobi desert grew to a magnitude comparable to that of the local maximum extent. This Holocene maximum occurred during a regional pluvial period thousands of years after the retreat of the Pleistocene glaciers globally. This asynchronous behavior is not predicted by the prevailing and generally correct presumption that glacier advances are dominantly driven by temperature, although precipitation also plays a role. Our findings are consistent with and support the Rupper/Roe model, which calls for

  18. Design issues in the semantics and scheduling of asynchronous tasks.

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, Stephen L.

    2013-07-01

    The asynchronous task model serves as a useful vehicle for shared memory parallel programming, particularly on multicore and manycore processors. As adoption of model among programmers has increased, support has emerged for the integration of task parallel language constructs into mainstream programming languages, e.g., C and C++. This paper examines some of the design decisions in Cilk and OpenMP concerning semantics and scheduling of asynchronous tasks with the aim of informing the efforts of committees considering language integration, as well as developers of new task parallel languages and libraries.

  19. On the theoretical gap between synchronous and asynchronous MPC protocols

    DEFF Research Database (Denmark)

    Beerliová-Trubíniová, Zuzana; Hirt, Martin; Nielsen, Jesper Buus

    2010-01-01

    that in the cryptographic setting (with setup), the sole reason for it is the distribution of inputs: given an oracle for input distribution, cryptographically-secure asynchronous MPC is possible with the very same condition as synchronous MPC, namely t ..., we show that such an input-distribution oracle can be reduced to an oracle that allows each party to synchronously broadcast one single message. This means that when one single round of synchronous broadcast is available, then asynchronous MPC is possible at the same condition as synchronous MPC...

  20. Procjena smjera dolaska vala primjenom neuralnih mreža za sustave D-CDMA s preklapanjem snopa

    OpenAIRE

    Gotsis, Konstantinos; Kaifas, Theodoros N.; Siakavara, Katherine; Sahalos, John N.

    2008-01-01

    Prikazana je metodologija procjene smjera dolaska signala željenog pokretnog korisnika uz primjenu neuralnih mreža za sustave s višestrukim pristupom po kodnoj osnovi s asinkronom izravnom sekvencijom (DS-CDMA). U sustavima DS-CDMA, valja procijeniti smjer dolaska signala željenog korisnika u nazočnosti više korisnika koji stvaraju interferencije (smetnje) što vodi do interferencije višestrukog pristupa. U ovom se radu rabi algoritam neuralnih mreža za potiskivanje interferencije uz primjenu ...

  1. THE ASYNCHRONOUS MACHINE WITH THE MASSIVE FERROMAGNETIC ROTOR AND CAPACITOR EXCITATION

    Directory of Open Access Journals (Sweden)

    Birladean A.A.

    2010-04-01

    Full Text Available An asynchronous machine with a massive ferromagnetic rotor of the various designs, improving its energy indicators is considered. Elaboration and experimental tests results of the asynchronous machine working in a generating mode at the lowered speed of rotation of a massive ferromagnetic rotor are presented. Conditions and possibilities of the asynchronous generator creation with capacitor excitation on the basis of the asynchronous machine with a massive rotor are shown as well.

  2. ANALISIS PERILAKU KONSUMEN DALAM MEMILIH JASA LAYANAN OPERATOR MOBILE PHONE YANG BERBASIS CDMA DAN GSM

    Directory of Open Access Journals (Sweden)

    Demitri Marvin Kadhaffi

    2012-05-01

    Full Text Available ABSTRAKS Tujuan penelitian ini adalah (1 menganalisis faktor-faktor yang dipertimbangkan konsumen dalam memilih suatu jasa layanan operator mobile phone (baik CDMA maupun GSM, (2 menganalsis variabel dominan yang mempengaruhi perilaku konsumen dalam memilih jasa layanan operator Jenis penelitian ini adalah applied research dengan metode penelitian studi kausal. Penelitian ini ditujukan pada segmen pelajar dan mahasiswa di Kota Malang yang termasuk kelompok Net Generations (yang lahir antara tahun 1977-1997 dengan batas minimal umur untuk responden adalah 17 tahun.  Kerangka Sampel untuk penelitian ini adalah pengguna kartu CDMA dan GSM sebanyak 175 responden. Tehnik Sampling yang digunakan adalah desain sampel non probability dengan metode purposive sample yang kedua yaitu quota sampling. Metode analisa data yang digunakan adalah analisa faktor dan analisa diskriminan Hasil analisa faktor terhadap 34 variabel diperoleh  7 faktor baru, yang diberi label sebagai berikut : (1 faktor citra produk (2 faktor pelayanan, (3 faktor pengaruh lingkungan, (4 faktor promosi,(5 faktor individual, (6 faktor harga, dan (7 faktor proses. Dari analisa diskriminan diperoleh hasil yang bertentangan dengan hipotesis yaitu ternyata variabel harga bukan merupakan variabel yang dominan dalam membedakan perilaku pelanggan operator CDMA dengan GSM. Mereka lebih sensitif terhadap proses produk. Hal ini mengarahkan pelanggan untuk kalangan pelajar dan mahasiswa sebagai kelompok smart. Hasil penelitian menyimpulkan bahwa untuk membangun keunggulan bersaing operator harus meraih keunggulan posisional melalui diferensiasi “content” jasa yang dihasilkan yaitu berupa proses, sebagai hasil dari aplikasi  positioning produk.   Kata kunci: perilaku konsumen, jasa layanan, mobile phone   ABSTRACT Objective of this research are (1 to identify factors that customer consider in choosing mobile phone operator service (whether CDMA and GSM, (2 to identify dominant variable that

  3. One-year, simultaneous combined exposure of CDMA and WCDMA radiofrequency electromagnetic fields to rats.

    Science.gov (United States)

    Jin, Yeung-Bae; Lee, Hae-June; Seon Lee, Jae; Pack, Jeong-Ki; Kim, Nam; Lee, Yun-Sil

    2011-04-01

    We investigated whether one-year, long-term, simultaneous exposure to code division multiple access (CDMA; 849 MHz) and wideband code division multiple access (WCDMA; 1.95 GHz) radiofrequencies (RF) would induce chronic illness in Sprague-Dawley (SD) rats. Two groups of 40 SD rats (50% males and females in sham and exposed groups) were exposed to CDMA and WCDMA RF simultaneously at 2.0 W/kg for 45 min/day (total 4.0 W/kg), 5 days per week for a total of one year. Body and organ weight measurements, urinalysis, haematological and blood biochemical analysis, and histopathological evaluations were performed. The mortality patterns in male and female rats exposed to RF were compared with those found in gender-matched sham control animals. No significant alteration in body weight was observed with the simultaneous combined RF exposure. Most RF-exposed rats showed no significant alteration, based on urinalysis, haematology, blood biochemistry, or histopathology. However, some altered parameters of the complete blood count and serum chemistry were seen in RF-exposed rats. The total tumour incidence was not different between sham-exposed and RF-exposed animals. Our results suggest that one-year chronic exposure to CDMA (849 MHz) and WCDMA (1.95 GHz) RF simultaneously at 2.0 W/kg for 45-min RF exposure periods (total, 4 W/kg) did not increase chronic illness in rats, although there were some altered parameters in the complete blood count and serum chemistry.

  4. Magnetoencephalography demonstrates multiple asynchronous generators during human sleep spindles.

    Science.gov (United States)

    Dehghani, Nima; Cash, Sydney S; Rossetti, Andrea O; Chen, Chih Chuan; Halgren, Eric

    2010-07-01

    Sleep spindles are approximately 1 s bursts of 10-16 Hz activity that occur during stage 2 sleep. Spindles are highly synchronous across the cortex and thalamus in animals, and across the scalp in humans, implying correspondingly widespread and synchronized cortical generators. However, prior studies have noted occasional dissociations of the magnetoencephalogram (MEG) from the EEG during spindles, although detailed studies of this phenomenon have been lacking. We systematically compared high-density MEG and EEG recordings during naturally occurring spindles in healthy humans. As expected, EEG was highly coherent across the scalp, with consistent topography across spindles. In contrast, the simultaneously recorded MEG was not synchronous, but varied strongly in amplitude and phase across locations and spindles. Overall, average coherence between pairs of EEG sensors was approximately 0.7, whereas MEG coherence was approximately 0.3 during spindles. Whereas 2 principle components explained approximately 50% of EEG spindle variance, >15 were required for MEG. Each PCA component for MEG typically involved several widely distributed locations, which were relatively coherent with each other. These results show that, in contrast to current models based on animal experiments, multiple asynchronous neural generators are active during normal human sleep spindles and are visible to MEG. It is possible that these multiple sources may overlap sufficiently in different EEG sensors to appear synchronous. Alternatively, EEG recordings may reflect diffusely distributed synchronous generators that are less visible to MEG. An intriguing possibility is that MEG preferentially records from the focal core thalamocortical system during spindles, and EEG from the distributed matrix system.

  5. Emprego de antenas adaptativas para a estimação de dados em ambiente CDMA

    OpenAIRE

    Puttini, Saulo Benigno

    2010-01-01

    Este trabalho fundamenta-se em propor e avaliar o desempenho de um modelo receptor adaptativo, com utilização de arranjo de sensores, a ser empregado em meios de multiplicidade de acesso via divisão por códigos (CDMA) para fins de estimação de dados. Inicialmente é apresentado um estudo sobre arranjos de antenas, desenvolvendo-se o equacionamento de um arranjo linear e uniforme (ULA). Enfatiza-se o emprego deste para fins de separação espacial de usuários, sendo relatadas e ilustradas algumas...

  6. Linear CDMA Detection Algorithm Based on Statistical Neurodynamics and Belief Propagation and the Stability Conditions

    Science.gov (United States)

    Shojiguchi, A.; Tanaka, T.; Okada, M.

    Recently a modified algorithm of code-division multiple-access (CDMA) parallel interference canceler (PIC) has been proposed by Tanaka based on statistical neurodynamics. In this paper we apply the modified algorithm to the linear PIC (LPIC) and investigate its stability. We show that the stable (unstable) fixed points of the modified algorithm correspond to the stable (unstable) replica symmetry solutions with the Gaussian prior. We also show the modified algorithm is a special case of Kabashima's belief-propagation algorithm with Gaussian prior.

  7. Adaptive Transmit Window Control for Channel State Based CDMA Downlink Packet Communications

    Science.gov (United States)

    Mori, Kazuo; Naito, Katsuhiro; Kobayashi, Hideo

    This paper proposes adaptive transmit window control based on both location of mobile stations and traffic load for channel state based packet transmissions in CDMA cellular downlink communications. The proposed scheme constrains downlink packet transmissions by employing a transmit window individually given to each mobile station. The transmit window size is adjusted by using the optimum threshold value, which is selected with regard to both the mobile locations and the traffic load. The simulation results show that the proposed scheme improved the transmission delay and fairness of service compared with the conventional scheme.

  8. Redes celulares de tercera generación: CDMA2000 Y WCDMA

    OpenAIRE

    Jaime Sánchez García; Myriam Meza Múgica

    2005-01-01

    Este artículo ofrece un panorama general de los sistemas de comunicaciones móviles celulares de tercera generación (3G) que han tenido una mayor aceptación (CDMA2000 y WCDMA) en el mercado, y una comparación basada en los puntos principales donde los sistemas difieren que indica las ventajas y desventajas de cada uno. Los sistemas de comunicaciones móviles celulares 3G ofrecen mayores capacidades de transmisión a los de segunda generación (2G), y permiten brindar, además de los tr...

  9. Promoting and Scaffolding Argumentation through Reflective Asynchronous Discussions

    Science.gov (United States)

    Lin, Huann-shyang; Hong, Zuway-R.; Lawrenz, Frances

    2012-01-01

    The purpose of this quasi-experimental study was to explore the impact of asynchronous discussion on the quality and complexity of college students' arguments. Three different cohorts of students registered in a physical science course in 2009 Fall, 2010 Spring, and 2010 Fall semesters were briefly supported with scaffolding in class and then…

  10. Asynchronous online foresight panels: the case of wildfire management

    Science.gov (United States)

    David N. Bengston; Robert L. Olson

    2015-01-01

    Text-based asynchronous online conferencing involves structured online discussion and deliberation among multiple participants from multiple sites in which there is a delay in interaction between contributors. This method has been widely used for a variety of purposes in higher education and other settings, but has not been commonly used in futures research. This paper...

  11. Numerical simulation of three phase asynchronous motor to ...

    African Journals Online (AJOL)

    Numerical simulation of three phase asynchronous motor to diagnose precisely the stator unbalanced voltage anomaly. ... First, the stator currents data pattern is used as a preliminary diagnosis. ... This similarity leads to uncertainty in the detection of the fault, which makes imperative the use of complementary technique.

  12. Selective distortion of body image by asynchronous visuotactile stimulation.

    Science.gov (United States)

    Perez-Marcos, Daniel; Martini, Matteo; Fuentes, Christina T; Bellido Rivas, Anna I; Haggard, Patrick; Sanchez-Vives, Maria V

    2017-12-18

    In the rubber hand illusion (RHI), a rubber hand is felt as being part of one's body. This illusion is evoked by providing synchronous visuotactile stimulation to the fake and real hands. Asynchronous visuotactile stimulation is known not to produce such an illusion of ownership, being commonly used as the control condition. Here we explored the impact of synchronous and asynchronous visuotactile stimulation on the body image. We combined the induction of the RHI with a quantitative test for the internal representation of body metrics (i.e., the positions of key fiducial points on the body relative to each other). We found a significant recalibration of the upper/lower arm lengths following asynchronous visuotactile stimulation. In particular, we observed a selective elongation of the lower arm, a distortion typical of deafferentation. Conversely, synchronous visuotactile stimulation did not alter the estimation of the arm segments' length. Our findings are consistent with a dynamic internal representation of body image that is continuously updated based on incoming multisensory information. Furthermore, the use of asynchronous multisensory stimulation as a neutral condition should be reconsidered since it introduces changes in the body image. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Study of a centrifugal pump, asynchronous motor and inverter, using ...

    African Journals Online (AJOL)

    ... concept to the study of a three-phase inverter, asynchronous motor and centrifugal pump. It presents the realization of the rectangular control using a micro controller (ATMEGA 168). The signals generated by the micro controller have been used to program the parallel port of a computer. By reading the recorded bits of the ...

  14. Student Moderators in Asynchronous Online Discussion: A Question of Questions

    Science.gov (United States)

    Zingaro, Daniel

    2012-01-01

    Much current research exalts the benefits of having students facilitate weekly discussions in asynchronous online courses. This study seeks to add to what is known about student moderation through an analysis of the types of questions students use to spur each discussion. Prior experimental work has demonstrated that the types of questions posed…

  15. Asynchronous updating of threshold-coupled chaotic neurons

    Indian Academy of Sciences (India)

    Abstract. We study a network of chaotic model neurons incorporating threshold- activated coupling. We obtain a wide range of spatiotemporal patterns under varying degrees of asynchronicity in the evolution of the neuronal components. For instance, we find that sequential updating of threshold-coupled chaotic neurons ...

  16. Asynchronous updating of threshold-coupled chaotic neurons

    Indian Academy of Sciences (India)

    We study a network of chaotic model neurons incorporating threshold activated coupling. We obtain a wide range of spatiotemporal patterns under varying degrees of asynchronicity in the evolution of the neuronal components. For instance, we find that sequential updating of threshold-coupled chaotic neurons can yield ...

  17. Designing Communities of Learners for Asynchronous Distance Education.

    Science.gov (United States)

    Moller, Leslie

    1998-01-01

    Describes the need for learning communities within the context of asynchronous distance education. Highlights include the relationship of community and distance learners; community as social reinforcement and as information exchange; and types of communities, including academic support communities, intellectual support communities, and…

  18. Cyber Asynchronous versus Blended Cyber Approach in Distance English Learning

    Science.gov (United States)

    Ge, Zi-Gang

    2012-01-01

    This study aims to compare the single cyber asynchronous learning approach with the blended cyber learning approach in distance English education. Two classes of 70 students participated in this study, which lasted one semester of about four months, with one class using the blended approach for their English study and the other only using the…

  19. Asynchronous Assessment in a Large Lecture Marketing Course

    Science.gov (United States)

    Downey, W. Scott; Schetzsle, Stacey

    2012-01-01

    Asynchronous assessment, which includes quizzes or exams online or outside class, offers marketing educators an opportunity to make more efficient use of class time and to enhance students' learning experiences by giving them more flexibility and choice in their assessment environment. In this paper, we examine the performance difference between…

  20. Designing a Web-Based Asynchronous Innovation/Entrepreneurism Course

    Science.gov (United States)

    Ghandforoush, Parviz

    2017-01-01

    Teaching an online fully asynchronous information technology course that requires students to ideate, build an e-commerce website, and develop an effective business plan involves a well-developed and highly engaging course design. This paper describes the design, development, and implementation of such a course and presents information on…

  1. Numerical simulation of three phase asynchronous motor to ...

    African Journals Online (AJOL)

    Simulation numérique du moteur asynchrone triphasé pour diagnostiquer précisément le défaut du déséquilibre de ..... carrying more energy [9]. This severity index assumes values ..... its spectrum in normal circumstance. It was theoretically predicted that in this condition, the EPVA signature would be free from any spectral.

  2. Development of speech glimpsing in synchronously and asynchronously modulated noise.

    Science.gov (United States)

    Hall, Joseph W; Buss, Emily; Grose, John H

    2014-06-01

    This study investigated development of the ability to integrate glimpses of speech in modulated noise. Noise was modulated synchronously across frequency or asynchronously such that when noise below 1300 Hz was "off," noise above 1300 Hz was "on," and vice versa. Asynchronous masking was used to examine the ability of listeners to integrate speech glimpses separated across time and frequency. The study used the Word Intelligibility by Picture Identification (WIPI) test and included adults, older children (age 8-10 yr) and younger children (5-7 yr). Results showed poorer masking release for the children than the adults for synchronous modulation but not for asynchronous modulation. It is possible that children can integrate cues relatively well when all intervals provide at least partial speech information (asynchronous modulation) but less well when some intervals provide little or no information (synchronous modulation). Control conditions indicated that children appeared to derive less benefit than adults from speech cues below 1300 Hz. This frequency effect was supported by supplementary conditions where the noise was unmodulated and the speech was low- or high-pass filtered. Possible sources of the developmental frequency effect include differences in frequency weighting, effective speech bandwidth, and the signal-to-noise ratio in the unmodulated noise condition.

  3. Reconceptualising Moderation in Asynchronous Online Discussions Using Grounded Theory

    Science.gov (United States)

    Vlachopoulos, Panos; Cowan, John

    2010-01-01

    This article reports a grounded theory study of the moderation of asynchronous online discussions, to explore the processes by which tutors in higher education decide when and how to moderate. It aims to construct a theory of e-moderation based on some key factors which appear to influence e-moderation. It discusses previous research on the…

  4. Adding the Human Touch to Asynchronous Online Learning

    Science.gov (United States)

    Glenn, Cynthia Wheatley

    2018-01-01

    For learners to actively accept responsibility in a virtual classroom platform, it is necessary to provide special motivation extending across the traditional classroom setting into asynchronous online learning. This article explores specific ways to do this that bridge the gap between ground and online students' learning experiences, and how…

  5. Miscellany of Students' Satisfaction in an Asynchronous Learning Environment

    Science.gov (United States)

    Larbi-Siaw, Otu; Owusu-Agyeman, Yaw

    2017-01-01

    This study investigates the determinants of students' satisfaction in an asynchronous learning environment using seven key considerations: the e-learning environment, student-content interaction, student and student interaction, student-teacher interaction, group cohesion and timely participation, knowledge of Internet usage, and satisfaction. The…

  6. An improved modelling of asynchronous machine with skin-effect ...

    African Journals Online (AJOL)

    The conventional method of analysis of Asynchronous machine fails to give accurate results especially when the machine is operated under high rotor frequency. At high rotor frequency, skin-effect dominates causing the rotor impedance to be frequency dependant. This paper therefore presents an improved method of ...

  7. Asynchronous spread spectrum communication paradigm for use in low-power applications: description and simulation results

    Science.gov (United States)

    Welch, E. B.; Holmes, David R., III; Coker, Jonathan D.; Schaefer, Timothy M.; Gilbert, Barry K.; Daniel, Erik S.

    2005-06-01

    Contemporary wireless communication strategies focus on efficient use of bandwidth in order to allow more users to exploit the RF spectrum through techniques like Frequency-hopping spread spectrum (SS) and Direct-sequence SS. In many real-world applications, these methods are implemented for synchronous communication systems. To achieve synchronous communication, two-way handshaking that requires overhead circuitry is performed between the sender and receiver. In order to use spread spectrum methods for certain unconstrained and low-power applications, such as implantable and remote monitoring devices, it is necessary to refine these methods to support asynchronous communication. We have designed and modeled a SS system, which could be integrated with a custom integrated circuit that would provide elementary multi-user communication. The SS logic generates a gold-code based on address and data bits that is then modulated with a carrier to transmit the information. Because the system is asynchronous, we treat each transmitted code as an independent piece of information. The receiver decodes the information using a full correlation with the ideal known gold-codes. For efficiency purposes, the filter is applied in the frequency domain. A threshold is applied to the output of the filter to determine if a particular code is transmitted as well as the point in time/space from which the signal was sent. The method was simulated and evaluated under several scenarios including different carrier frequencies, multiple targets, and various positions relative to the receiver from the simulated receiver. The results demonstrate the utility of asynchronous SS under many different conditions.

  8. An Asynchronous Low Power and High Performance VLSI Architecture for Viterbi Decoder Implemented with Quasi Delay Insensitive Templates

    OpenAIRE

    T. Kalavathi Devi; Sakthivel Palaniappan

    2015-01-01

    Convolutional codes are comprehensively used as Forward Error Correction (FEC) codes in digital communication systems. For decoding of convolutional codes at the receiver end, Viterbi decoder is often used to have high priority. This decoder meets the demand of high speed and low power. At present, the design of a competent system in Very Large Scale Integration (VLSI) technology requires these VLSI parameters to be finely defined. The proposed asynchronous method focuses on reducing the powe...

  9. Commande optimale à flux libre des machines asynchrones

    Science.gov (United States)

    Biedinger, J. M.; Poullain, S.; Yvon, J. P.

    1992-01-01

    The subject of this paper is the optimal control with unconstrained flux of an induction motor being considered as a distributed parameter system described by a nonlinear diffusion equation. This approach allows to describe the electrodynamic state of the motor by taking into account, in a natural way, the influence of saturation and eddy-currents, as well as the nonlinearities due to the variable flux operation. Equations are approximated via a finite element formulation which leads to a finite dimensional dynamical system to which the techniques of optimal control may be applied. The generality of the methodology allows to treat various criteria. The objective aimed in this paper is to force the motor torque to follow a given input, especially under initially demagnetized conditions and with, naturally, constraints on the currents. For this purpose the criterion will be chosen as a norm of the difference between the electromagnetic torque and a given reference torque. Numerical simulations are presented for the case of a squirrel-cage rotor and for a solid iron rotor. Results are compared with those deduced from strategies based on lumped-parameter models. Torque responses obtained with field-oriented control method adapted to the case of flux-variable operation are also presented. Finally a modification of the criterion is proposed for identifying the command which allows to obtain the larger torque during transient states. Dans cet article on traite le problème du contrôle optimal à flux libre d'un moteur asynchrone considéré comme un système à paramètres répartis gouverné par une équation de diffusion non linéaire. Cette approche permet de décrire l'état électrodynamique de la machine en prenant naturellement en compte les effets de la saturation et des courants induits, ainsi que les non-linéarités liées au fonctionnement à flux variable. La formulation éléments finis est utilisée pour traduire le problème continu sous la forme d

  10. Exploring effectiveness of team communication: Balancing synchronous and asynchronous communication in design teams

    DEFF Research Database (Denmark)

    den Otter, Ad; Emmitt, Stephen

    2007-01-01

    Effective teams use a balance of synchronous and asynchronous communication. Team communication is dependent on the communication acts of team members and the ability of managers to facilitate, stimulate and motivate them. Team members from organizations using different information systems tend...... to have different understanding, opinions, and rates of adoption and skills levels regarding specific IT tools. The purpose of this paper is to explore the effective use of tools for communication in design teams and the strategies for the use of specific tools....

  11. Survey is based on Synchronized and Asynchronized Approach of MAC Protocols in WSN

    Directory of Open Access Journals (Sweden)

    Soni Chaurasia

    2010-07-01

    Full Text Available A wireless network is made of spatially distributed autonomous devices. These devices are called sensors. The sensor is used for monitoring physical or environmental conditions. The potential application of wireless sensor network is environmental monitoring, healthcare applications and tactical systems. In this paper focus is on the MAC protocol for WSN. Wireless sensor network is deployed for wide range to send and receive data with the help of medium. Here literature survey of MAC protocol based on the synchronized and asynchronized approach is described which is used to meet different objective like access a medium, statistical channel allocation, spectrum utilization

  12. Asynchronous Task-Based Parallelization of Algebraic Multigrid

    KAUST Repository

    AlOnazi, Amani A.

    2017-06-23

    As processor clock rates become more dynamic and workloads become more adaptive, the vulnerability to global synchronization that already complicates programming for performance in today\\'s petascale environment will be exacerbated. Algebraic multigrid (AMG), the solver of choice in many large-scale PDE-based simulations, scales well in the weak sense, with fixed problem size per node, on tightly coupled systems when loads are well balanced and core performance is reliable. However, its strong scaling to many cores within a node is challenging. Reducing synchronization and increasing concurrency are vital adaptations of AMG to hybrid architectures. Recent communication-reducing improvements to classical additive AMG by Vassilevski and Yang improve concurrency and increase communication-computation overlap, while retaining convergence properties close to those of standard multiplicative AMG, but remain bulk synchronous.We extend the Vassilevski and Yang additive AMG to asynchronous task-based parallelism using a hybrid MPI+OmpSs (from the Barcelona Supercomputer Center) within a node, along with MPI for internode communications. We implement a tiling approach to decompose the grid hierarchy into parallel units within task containers. We compare against the MPI-only BoomerAMG and the Auxiliary-space Maxwell Solver (AMS) in the hypre library for the 3D Laplacian operator and the electromagnetic diffusion, respectively. In time to solution for a full solve an MPI-OmpSs hybrid improves over an all-MPI approach in strong scaling at full core count (32 threads per single Haswell node of the Cray XC40) and maintains this per node advantage as both weak scale to thousands of cores, with MPI between nodes.

  13. The probability estimate of the defects of the asynchronous motors based on the complex method of diagnostics

    Science.gov (United States)

    Zhukovskiy, Yu L.; Korolev, N. A.; Babanova, I. S.; Boikov, A. V.

    2017-10-01

    This article is devoted to the development of a method for probability estimate of failure of an asynchronous motor as a part of electric drive with a frequency converter. The proposed method is based on a comprehensive method of diagnostics of vibration and electrical characteristics that take into account the quality of the supply network and the operating conditions. The developed diagnostic system allows to increase the accuracy and quality of diagnoses by determining the probability of failure-free operation of the electromechanical equipment, when the parameters deviate from the norm. This system uses an artificial neural networks (ANNs). The results of the system for estimator the technical condition are probability diagrams of the technical state and quantitative evaluation of the defects of the asynchronous motor and its components.

  14. Space-Time Chip Equalization for Maximum Diversity Space-Time Block Coded DS-CDMA Downlink Transmission

    NARCIS (Netherlands)

    Leus, G.; Petré, F.; Moonen, M.

    2004-01-01

    In the downlink of DS-CDMA, frequency-selectivity destroys the orthogonality of the user signals and introduces multiuser interference (MUI). Space-time chip equalization is an efficient tool to restore the orthogonality of the user signals and suppress the MUI. Furthermore, multiple-input

  15. Fast Simulation of Mechanical Heterogeneity in the Electrically Asynchronous Heart Using the MultiPatch Module.

    Directory of Open Access Journals (Sweden)

    John Walmsley

    2015-07-01

    Full Text Available Cardiac electrical asynchrony occurs as a result of cardiac pacing or conduction disorders such as left bundle-branch block (LBBB. Electrically asynchronous activation causes myocardial contraction heterogeneity that can be detrimental for cardiac function. Computational models provide a tool for understanding pathological consequences of dyssynchronous contraction. Simulations of mechanical dyssynchrony within the heart are typically performed using the finite element method, whose computational intensity may present an obstacle to clinical deployment of patient-specific models. We present an alternative based on the CircAdapt lumped-parameter model of the heart and circulatory system, called the MultiPatch module. Cardiac walls are subdivided into an arbitrary number of patches of homogeneous tissue. Tissue properties and activation time can differ between patches. All patches within a wall share a common wall tension and curvature. Consequently, spatial location within the wall is not required to calculate deformation in a patch. We test the hypothesis that activation time is more important than tissue location for determining mechanical deformation in asynchronous hearts. We perform simulations representing an experimental study of myocardial deformation induced by ventricular pacing, and a patient with LBBB and heart failure using endocardial recordings of electrical activation, wall volumes, and end-diastolic volumes. Direct comparison between simulated and experimental strain patterns shows both qualitative and quantitative agreement between model fibre strain and experimental circumferential strain in terms of shortening and rebound stretch during ejection. Local myofibre strain in the patient simulation shows qualitative agreement with circumferential strain patterns observed in the patient using tagged MRI. We conclude that the MultiPatch module produces realistic regional deformation patterns in the asynchronous heart and that

  16. Effects of RF exposure of teenagers and adults by CDMA cellular phones.

    Science.gov (United States)

    Nam, Ki Chang; Kim, Sung Woo; Kim, Soo Chan; Kim, Deok Won

    2006-10-01

    Many cellular phone provocation studies have been conducted since the question of increased health risk from extended usage of cellular phones became a social issue. Internationally, most studies have been conducted regarding the effects of GSM cellular phones on blood pressure and heart rate of adult volunteers. On the other hand, very few provocation studies have been conducted regarding the physiological effects of CDMA phones on teenagers. In this study, two volunteer groups consisting of 21 teenagers and 21 adults were exposed to 300 mW of radio frequency (RF) electromagnetic field emitted by a CDMA cellular phone for half an hour. Physiological parameters such as systolic and diastolic blood pressures, heart rate, respiration rate, and skin resistance were simultaneously measured. All the parameters for both groups were unaffected during the exposure except for decreased skin resistance of the teenager group (P < .0001). For the regrouped 23 male and 19 female subjects, all the parameters for both groups were unaffected during the exposure except for decreased skin resistance of the male subjects (P = .0026). Those resistances at 10 min after the terminated exposure returned to the resistances at rest regardless of the different groups of age and sex.

  17. Combinative exposure effect of radio frequency signals from CDMA mobile phones and aphidicolin on DNA integrity.

    Science.gov (United States)

    Tiwari, R; Lakshmi, N K; Surender, V; Rajesh, A D V; Bhargava, S C; Ahuja, Y R

    2008-01-01

    The aim of present study is to assess DNA integrity on the effect of exposure to a radio frequency (RF) signal from Code Division Multiple Access (CDMA) mobile phones. Whole blood samples from six healthy male individuals were exposed for RF signals from a CDMA mobile phone for 1 h. Alkaline comet assay was performed to assess the DNA damage. The combinative exposure effect of the RF signals and APC at two concentrations on DNA integrity was studied. DNA repair efficiency of the samples was also studied after 2 h of exposure. The RF signals and APC (0.2 microg/ml) alone or in synergism did not have any significant DNA damage as compared to sham exposed. However, univariate analysis showed that DNA damage was significantly different among combinative exposure of RF signals and APC at 0.2 microg/ml (p < 0.05) and at 2 microg/ml (p < 0.02). APC at 2 microg/ml concentration also showed significant damage levels (p < 0.05) when compared to sham exposed. DNA repair efficiency also varied in a significant way in combinative exposure sets (p < 0.05). From these results, it appears that the repair inhibitor APC enhances DNA breaks at 2 microg/ml concentration and that the damage is possibly repairable. Thus, it can be inferred that the in vitro exposure to RF signals induces reversible DNA damage in synergism with APC.

  18. Waveform Design and Diversity for Advanced Space-Time Adaptive Processing and Multiple Input Multiple Output Systems

    Science.gov (United States)

    2012-08-01

    and P.-C. Ching, “Quasi-Maximum-Likelihood Multiuser Detection Using Semi-Definite Relaxation With Application to Synchronous CDMA ”, IEEE Transactions...86] J.C. Liberti Jr. and T.S. Rappaport, “Analytical results for capacity im- provements in CDMA ,” IEEE Transaction on Vehicular Technology, Vol. 43...no. 3, pp. 680 - 690, Aug. 1994. [87] S. Anderson, M. Millnert, M. Viberg, and B. Wahlberg, “An adaptive ar- ray for mobile communication systems

  19. Participation in asynchronous online discussion forums does improve student learning of gross anatomy.

    Science.gov (United States)

    Green, Rodney A; Farchione, Davide; Hughes, Diane L; Chan, Siew-Pang

    2014-01-01

    Asynchronous online discussion forums are common in blended learning models and are popular with students. A previous report has suggested that participation in these forums may assist student learning in a gross anatomy subject but it was unclear as to whether more academically able students post more often or whether participation led to improved learning outcomes. This study used a path model to analyze the contribution of forum participation, previous academic ability, and student campus of enrolment to final marks in a multicampus gross anatomy course for physiotherapy students. The course has a substantial online learning management system (LMS) that incorporates asynchronous forums as a learning tool, particularly to answer learning objectives. Students were encouraged to post new threads and answer queries in threads started by others. The forums were moderated weekly by staff. Discussion forums were the most used feature of the LMS site with 31,920 hits. Forty-eight percent of the students posted at least once with 186 threads initiated by students and a total of 608 posts. The total number of posts made a significant direct contribution to final mark (P = 0.008) as did previous academic ability (P = 0.002). Although campus did not contribute to final mark, there was a trend for students at the campus where the course coordinator was situated to post more often than those at the other campus (P = 0.073). These results indicate that asynchronous online discussion forums can be an effective tool for improving student learning outcomes as evidenced by final marks in gross anatomy teaching. Copyright © 2013 American Association of Anatomists.

  20. Website creation and resource management: developing collaborative strategies for asynchronous interaction with library users.

    Science.gov (United States)

    Hopkins, Mark E; Summers-Ables, Joy E; Clifton, Shari C; Coffman, Michael A

    2011-06-01

    To make electronic resources available to library users while effectively harnessing intellectual capital within the library, ultimately fostering the library's use of technology to interact asynchronously with its patrons (users). The methods used in the project included: (1) developing a new library website to facilitate the creation, management, accessibility, maintenance and dissemination of library resources; and (2) establishing ownership by those who participated in the project, while creating effective work allocation strategies through the implementation of a content management system that allowed the library to manage cost, complexity and interoperability. Preliminary results indicate that contributors to the system benefit from an increased understanding of the library's resources and add content valuable to library patrons. These strategies have helped promote the manageable creation and maintenance of electronic content in accomplishing the library's goal of interacting with its patrons. Establishment of a contributive system for adding to the library's electronic resources and electronic content has been successful. Further work will look at improving asynchronous interaction, particularly highlighting accessibility of electronic content and resources. © 2010 The authors. Health Information and Libraries Journal © 2010 Health Libraries Group.

  1. A BMI-based occupational therapy assist suit: asynchronous control by SSVEP

    Directory of Open Access Journals (Sweden)

    Takeshi eSakurada

    2013-09-01

    Full Text Available A brain-machine interface (BMI is an interface technology that uses neurophysiological signals from the brain to control external machines. Recent invasive BMI technologies have succeeded in the asynchronous control of robot arms for a useful series of actions, such as reaching and grasping. In this study, we developed non-invasive BMI technologies aiming to make such useful movements using the subject's own hands by preparing a BMI-based occupational therapy assist suit (BOTAS. We prepared a pre-recorded series of useful actionsa grasping-a-ball movement and a carrying-the-ball movementand added asynchronous control using steady-state visual evoked potential (SSVEP signals. A SSVEP signal was used to trigger the grasping-a-ball movement and another SSVEP signal was used to trigger the carrying-the-ball movement. A support vector machine was used to classify EEG signals recorded from the visual cortex (Oz in real time. Untrained, able-bodied participants (n = 12 operated the system successfully. Classification accuracy and time required for SSVEP detection were approximately 88% and 3 s, respectively. We further recruited three patients with upper cervical spinal cord injuries; they also succeeded in operating the system without training. These data suggest that our BOTAS system is potentially useful in terms of rehabilitation of patients with upper limb disabilities.

  2. Asynchronous single-shot characterization of high-repetition-rate ultrafast waveforms using a time-lens-based temporal magnifier.

    Science.gov (United States)

    Okawachi, Yoshitomo; Salem, Reza; Johnson, Adrea R; Saha, Kasturi; Levy, Jacob S; Lipson, Michal; Gaeta, Alexander L

    2012-12-01

    We demonstrate asynchronous, single-shot characterization of an ultrafast, high-repetition-rate pulse source using a time-lens-based temporal magnifier. We measure a 225 GHz repetition-rate pulse train from a microresonator-based frequency comb. In addition, we show that such a system can be used as a frequency compressor for real-time, high-speed RF spectral characterization.

  3. Analisis Faktor-Faktor Yang Mempengaruhi Perilaku Konsumen Terhadap Keputusan Menggunakan Dua Ponsel (GSM dan CDMA) Pada Mahasiswa Departemen Manajemen Fakultas Ekonomi USU.

    OpenAIRE

    Hutagalung, Raja Bongsu; Aisha, Novi

    2010-01-01

    The purpose of this research is to find out and to analysis culture factor, social factor, personal factor, and psychology factor have influence on the decision of using two handphone (GSM and CDMA). The result of research indicate that the factors of influence consumer behaviour which is consist of culture factor, social factor, personal factor, and psychology factor are together have significant effect toward decision of using two handphone (GSM and CDMA). The result also indicates that cul...

  4. Pre-synthesis Optimization for Asynchronous Circuits Using Compiler Techniques

    Science.gov (United States)

    Zamanzadeh, Sharareh; Najibi, Mehrdad; Pedram, Hossein

    The effectiveness of traditional compiler techniques employed in high-level synthesis of synchronous circuits aiming to present a generic code is studied for asynchronous synthesis by considering the special features of these circuits. The compiler methods can be used innovatively to improve the synthesis results in both power consumption and area. The compiler methods like speculation, loop invariant code motion and condition expansion are applicable in decreasing mass of handshaking circuits and intermediate modules. Moreover, they eliminate conditional access to variables and ports and reducing the amount of completion detection circuits. The approach is superimposed on to Persia synthesis toolset as a presynthesis source-to-source transformation phase, and results shows on average 22% improvement in terms of area and 24 % in power consumption for asynchronous benchmarks.

  5. Asynchronous Task-Based Polar Decomposition on Single Node Manycore Architectures

    KAUST Repository

    Sukkari, Dalal E.

    2017-09-29

    This paper introduces the first asynchronous, task-based formulation of the polar decomposition and its corresponding implementation on manycore architectures. Based on a formulation of the iterative QR dynamically-weighted Halley algorithm (QDWH) for the calculation of the polar decomposition, the proposed implementation replaces the original LU factorization for the condition number estimator by the more adequate QR factorization to enable software portability across various architectures. Relying on fine-grained computations, the novel task-based implementation is capable of taking advantage of the identity structure of the matrix involved during the QDWH iterations, which decreases the overall algorithmic complexity. Furthermore, the artifactual synchronization points have been weakened compared to previous implementations, unveiling look-ahead opportunities for better hardware occupancy. The overall QDWH-based polar decomposition can then be represented as a directed acyclic graph (DAG), where nodes represent computational tasks and edges define the inter-task data dependencies. The StarPU dynamic runtime system is employed to traverse the DAG, to track the various data dependencies and to asynchronously schedule the computational tasks on the underlying hardware resources, resulting in an out-of-order task scheduling. Benchmarking experiments show significant improvements against existing state-of-the-art high performance implementations for the polar decomposition on latest shared-memory vendors\\' systems, while maintaining numerical accuracy.

  6. Mixing rich and asynchronous communication for new service development performance

    OpenAIRE

    Storey, Chris; Perks, Helen

    2015-01-01

    This article explores the nature of relationships between internal communication modes, new service development (NSD) competencies (specifically learning and development competencies) and NSD performance. To do so, it draws on and advances communication theory by comparing and contrasting the contingent approach, favoured by media richness theory and media synchronicity theory, with the multiplicative manner of dual coding theory. Antecedent roles of rich and asynchronous communication modes ...

  7. Asynchronous Multi-Party Computation with Quadratic Communication

    DEFF Research Database (Denmark)

    Hirt, Martin; Nielsen, Jesper Buus; Przydatek, Bartosz

    2008-01-01

    We present an efficient protocol for secure multi-party computation in the asynchronous model with optimal resilience. For n parties, up to t < n/3 of them being corrupted, and security parameter κ, a circuit with c gates can be securely computed with communication complexity O(cn^2k) bits, which...... circuit randomization due to Beaver (Crypto’91), and an abstraction of certificates, which can be of independent interest....

  8. Marine Forces Reserve: Accelerating Knowledge Flow through Asynchronous Learning Technologies

    Science.gov (United States)

    2014-12-19

    Substantial evidence indicates that—with informed instruction design and appropriate pedagogy —the efficacy of online education and training is...efficacy of online education and training is at least 3 comparable to that of classroom teaching. Indeed, the educational psychology literature is...learning in an education environment, and we adapt such highly effective asynchronous learning techniques and technologies to the I-I training task

  9. Psychophysiological effects of synchronous versus asynchronous music during cycling.

    Science.gov (United States)

    Lim, Harry B T; Karageorghis, Costas I; Romer, Lee M; Bishop, Daniel T

    2014-02-01

    Synchronizing movement to a musical beat may reduce the metabolic cost of exercise, but findings to date have been equivocal. Our aim was to examine the degree to which the synchronous application of music moderates the metabolic demands of a cycle ergometer task. Twenty-three recreationally active men made two laboratory visits. During the first visit, participants completed a maximal incremental ramp test on a cycle ergometer. At the second visit, they completed four randomized 6-min cycling bouts at 90% of ventilatory threshold (control, metronome, synchronous music, and asynchronous music). Main outcome variables were oxygen uptake, HR, ratings of dyspnea and limb discomfort, affective valence, and arousal. No significant differences were evident for oxygen uptake. HR was lower under the metronome condition (122 ± 15 bpm) compared to asynchronous music (124 ± 17 bpm) and control (125 ± 16 bpm). Limb discomfort was lower while listening to the metronome (2.5 ± 1.2) and synchronous music (2.3 ± 1.1) compared to control (3.0 ± 1.5). Both music conditions, synchronous (1.9 ± 1.2) and asynchronous (2.1 ± 1.3), elicited more positive affective valence compared to metronome (1.2 ± 1.4) and control (1.2 ± 1.2), while arousal was higher with synchronous music (3.4 ± 0.9) compared to metronome (2.8 ± 1.0) and control (2.8 ± 0.9). Synchronizing movement to a rhythmic stimulus does not reduce metabolic cost but may lower limb discomfort. Moreover, synchronous music has a stronger effect on limb discomfort and arousal when compared to asynchronous music.

  10. A New Aloha Anti-Collision Algorithm Based on CDMA

    Science.gov (United States)

    Bai, Enjian; Feng, Zhu

    The tags' collision is a common problem in RFID (radio frequency identification) system. The problem has affected the integrity of the data transmission during the process of communication in the RFID system. Based on analysis of the existing anti-collision algorithm, a novel anti-collision algorithm is presented. The new algorithm combines the group dynamic frame slotted Aloha algorithm with code division multiple access technology. The algorithm can effectively reduce the collision probability between tags. Under the same number of tags, the algorithm is effective in reducing the reader recognition time and improve overall system throughput rate.

  11. Clonal expansion and linear genome evolution through breast cancer progression from pre-invasive stages to asynchronous metastasis

    DEFF Research Database (Denmark)

    Krøigård, Anne Bruun; Larsen, Martin Jakob; Lænkholm, Anne-Vibeke

    2015-01-01

    Evolution of the breast cancer genome from pre-invasive stages to asynchronous metastasis is complex and mostly unexplored, but highly demanded as it may provide novel markers for and mechanistic insights in cancer progression. The increasing use of personalized therapy of breast cancer...... necessitates knowledge of the degree of genomic concordance between different steps of malignant progression as primary tumors often are used as surrogates of systemic disease. Based on exome sequencing we performed copy number profiling and point mutation detection on successive steps of breast cancer...... progression from one breast cancer patient, including two different regions of Ductal Carcinoma In Situ (DCIS), primary tumor and an asynchronous metastasis. We identify a remarkable landscape of somatic mutations, retained throughout breast cancer progression and with new mutational events emerging at each...

  12. A novel asynchronous access method with binary interfaces

    Directory of Open Access Journals (Sweden)

    Torres-Solis Jorge

    2008-10-01

    Full Text Available Abstract Background Traditionally synchronous access strategies require users to comply with one or more time constraints in order to communicate intent with a binary human-machine interface (e.g., mechanical, gestural or neural switches. Asynchronous access methods are preferable, but have not been used with binary interfaces in the control of devices that require more than two commands to be successfully operated. Methods We present the mathematical development and evaluation of a novel asynchronous access method that may be used to translate sporadic activations of binary interfaces into distinct outcomes for the control of devices requiring an arbitrary number of commands to be controlled. With this method, users are required to activate their interfaces only when the device under control behaves erroneously. Then, a recursive algorithm, incorporating contextual assumptions relevant to all possible outcomes, is used to obtain an informed estimate of user intention. We evaluate this method by simulating a control task requiring a series of target commands to be tracked by a model user. Results When compared to a random selection, the proposed asynchronous access method offers a significant reduction in the number of interface activations required from the user. Conclusion This novel access method offers a variety of advantages over traditionally synchronous access strategies and may be adapted to a wide variety of contexts, with primary relevance to applications involving direct object manipulation.

  13. Renewal Approach to the Analysis of the Asynchronous State for Coupled Noisy Oscillators.

    Science.gov (United States)

    Farkhooi, Farzad; van Vreeswijk, Carl

    2015-07-17

    We develop a framework in which the activity of nonlinear pulse-coupled oscillators is posed within the renewal theory. In this approach, the evolution of the interevent density allows for a self-consistent calculation that determines the asynchronous state and its stability. This framework can readily be extended to the analysis of systems with more state variables and provides a population density treatment to evolve them in their thermodynamical limits. To demonstrate this we study a nonlinear pulse-coupled system, where couplings are dynamic and activity dependent. We investigate its stability and numerically study the nonequilibrium behavior of the system after the bifurcation. We show that this system undergoes a supercritical Hopf bifurcation to collective synchronization.

  14. Pharmacists' perception of synchronous versus asynchronous distance learning for continuing education programs.

    Science.gov (United States)

    Buxton, Eric C

    2014-02-12

    To evaluate and compare pharmacists' satisfaction with the content and learning environment of a continuing education program series offered as either synchronous or asynchronous webinars. An 8-lecture series of online presentations on the topic of new drug therapies was offered to pharmacists in synchronous and asynchronous webinar formats. Participants completed a 50-question online survey at the end of the program series to evaluate their perceptions of the distance learning experience. Eighty-two participants completed the survey instrument (41 participants from the live webinar series and 41 participants from the asynchronous webinar series.) Responses indicated that while both groups were satisfied with the program content, the asynchronous group showed greater satisfaction with many aspects of the learning environment. The synchronous and asynchronous webinar participants responded positively regarding the quality of the programming and the method of delivery, but asynchronous participants rated their experience more positively overall.

  15. Scalability of Several Asynchronous Many-Task Models for In Situ Statistical Analysis.

    Energy Technology Data Exchange (ETDEWEB)

    Pebay, Philippe Pierre [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Bennett, Janine Camille [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Kolla, Hemanth [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Borghesi, Giulio [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2017-05-01

    This report is a sequel to [PB16], in which we provided a first progress report on research and development towards a scalable, asynchronous many-task, in situ statistical analysis engine using the Legion runtime system. This earlier work included a prototype implementation of a proposed solution, using a proxy mini-application as a surrogate for a full-scale scientific simulation code. The first scalability studies were conducted with the above on modestly-sized experimental clusters. In contrast, in the current work we have integrated our in situ analysis engines with a full-size scientific application (S3D, using the Legion-SPMD model), and have conducted nu- merical tests on the largest computational platform currently available for DOE science ap- plications. We also provide details regarding the design and development of a light-weight asynchronous collectives library. We describe how this library is utilized within our SPMD- Legion S3D workflow, and compare the data aggregation technique deployed herein to the approach taken within our previous work.

  16. An Autonomous Wireless Sensor Node With Asynchronous ECG Monitoring in 0.18 μ m CMOS.

    Science.gov (United States)

    Mansano, Andre L; Li, Yongjia; Bagga, Sumit; Serdijn, Wouter A

    2016-06-01

    The design of a 13.56 MHz/402 MHz autonomous wireless sensor node with asynchronous ECG monitoring for near field communication is presented. The sensor node consists of an RF energy harvester (RFEH), a power management unit, an ECG readout, a data encoder and an RF backscattering transmitter. The energy harvester supplies the system with 1.25 V and offers a power conversion efficiency of 19% from a -13 dBm RF source at 13.56 MHz. The power management unit regulates the output voltage of the RFEH to supply the ECG readout with VECG = 0.95 V and the data encoder with VDE = 0.65 V . The ECG readout comprises an analog front-end (low noise amplifier and programmable voltage to current converter) and an asynchronous level crossing ADC with 8 bits resolution. The ADC output is encoded by a pulse generator that drives a backscattering transmitter at 402 MHz. The total power consumption of the sensor node circuitry is 9.7 μ W for a data rate of 90 kb/s and a heart rate of 70 bpm. The chip has been designed in a 0.18 μm CMOS process and shows superior RF input power sensitivity and lower power consumption when compared to previous works.

  17. Significance of microbial asynchronous anabolism to soil carbon dynamics driven by litter inputs

    Science.gov (United States)

    Fan, Zhaosheng; Liang, Chao

    2015-04-01

    Soil organic carbon (SOC) plays an important role in the global carbon cycle. However, it remains largely unknown how plant litter inputs impact magnitude, composition and source configuration of the SOC stocks over long term through microbial catabolism and anabolism, mostly due to uncoupled research on litter decomposition and SOC formation. This limits our ability to predict soil system responses to changes in land-use and climate. Here, we examine how microbes act as a valve controlling carbon sequestrated from plant litters versus released to the atmosphere in natural ecosystems amended with plant litters varying in quantity and quality. We find that litter quality - not quantity - regulates long-term SOC dynamics under different plausible scenarios. Long-term changes in bulk SOC stock occur only when the quality of carbon inputs causes asynchronous change in a microbial physiological trait, defined as ``microbial biosynthesis acceleration'' (MBA). This is the first theoretical demonstration that the response of the SOC stocks to litter inputs is critically determined by the microbial physiology. Our work suggests that total SOC at an equilibrium state may be an intrinsic property of a given ecosystem, which ultimately is controlled by the asynchronous MBA between microbial functional groups.

  18. CMOS high linearity PA driver with an on-chip transformer for W-CDMA application

    Science.gov (United States)

    Jian, Fu; Niansong, Mei; Yumei, Huang; Zhiliang, Hong

    2011-09-01

    A fully integrated high linearity differential power amplifier driver with an on-chip transformer in a standard 0.13-μm CMOS process for W-CDMA application is presented. The transformer not only accomplishes output impedance matching, but also acts as a balun for converting differential signals to single-ended ones. Under a supply voltage of 3.3 V, the measured maximum power is larger than 17 dBm with a peak power efficiency of 21%. The output power at the 1-dB compression point and the power gain are 12.7 dBm and 13.2 dB, respectively. The die size is 0.91 × 1.12 mm2.

  19. DOA estimation for local scattered CDMA signals by particle swarm optimization.

    Science.gov (United States)

    Chang, Jhih-Chung

    2012-01-01

    This paper deals with the direction-of-arrival (DOA) estimation of local scattered code-division multiple access (CDMA) signals based on a particle swarm optimization (PSO) search. For conventional spectral searching estimators with local scattering, the searching complexity and estimating accuracy strictly depend on the number of search grids used during the search. In order to obtain high-resolution and accurate DOA estimation, a smaller grid size is needed. This is time consuming and it is unclear how to determine the required number of search grids. In this paper, a modified PSO is presented to reduce the required search grids for the conventional spectral searching estimator with the effects of local scattering. Finally, several computer simulations are provided for illustration and comparison.

  20. A self-learning call admission control scheme for CDMA cellular networks.

    Science.gov (United States)

    Liu, Derong; Zhang, Yi; Zhang, Huaguang

    2005-09-01

    In the present paper, a call admission control scheme that can learn from the network environment and user behavior is developed for code division multiple access (CDMA) cellular networks that handle both voice and data services. The idea is built upon a novel learning control architecture with only a single module instead of two or three modules in adaptive critic designs (ACDs). The use of adaptive critic approach for call admission control in wireless cellular networks is new. The call admission controller can perform learning in real-time as well as in offline environments and the controller improves its performance as it gains more experience. Another important contribution in the present work is the choice of utility function for the present self-learning control approach which makes the present learning process much more efficient than existing learning control methods. The performance of our algorithm will be shown through computer simulation and compared with existing algorithms.