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Multi-user adaptive receivers for a multiple-access system based on random permutations on time-varying frequency-selective channels with unknown delays and coefficients

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IET COMMUNICATIONS 2012年第11期6卷 1562-1572页

作者： Coulon, M. Roviras, D. Univ Toulouse INPT ENSEEIHT IRIT Lab F-31071 Toulouse 7 France CNAM Paris LAETITIA Lab F-75003 Paris France

This study deals with a multiple-access transmission scheme based on random permutations, which allows one to obtain both spectrum spreading and time spreading. In particular, one is interested by the multi-user detection when the transmission is achieved in the context of asynchronous frequency-selective and time-varying channels. For this detection, it is assumed that the channel coefficients and delays are unknown at the receiver side. Instead, only rough estimates of the minimum and maximum delays are available. However, it is supposed that the transmitter sends pilot signals, that is, training bit sequences, which allow the receiver to perform an LMS (least-mean-square)-type detection. This study provides theoretical performance results. Moreover, this random permutation-based transmission scheme is compared with the DS-CDMA system, for which a similar LMS receiver is defined, under the same assumptions. It is then shown that, for time-varying channels, the permutation-based system presents lower bit-error rates than the DS-CDMA system, since the former provides time diversity.

关键词： time diversity direct-sequence code-division multiple access Multi access systems adaptive receiver Receivers Channel Coefficient Multiuser detection delay CDMA mobile communications time-varying channels Permutation

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A Novel Spreading sequence and its Performances for code-Diversity in DS/CDMA Communications Systems

A Novel Spreading Sequence and its Performances for Code-Div...

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International Symposium on Information Theory and its Applications (ISITA)

作者： Noguchi, Hayato Tachikawa, Shin'ichi Nagaoka Natl Coll Technol Elect & Mech Syst Engn Adv Course Nagaoka Niigata 9408532 Japan

ISBN: (纸本)9784885522673

This paper proposes a novel spreading sequence for code-diversity in direct sequence/ code division multiple access (DC/CDMA) communication systems. In code-diversity, a composite sequence which is a sum of several branch sequences is adopted. By the proposed sequences, both the composite sequence and the branch sequences can be constructed from digital signal. Therefore, the hardware of the system can be simplified. By evaluations of computer simulations, bit error rate (BER) performance of the system to suppress multiple access interference (MAI) has a little degradation compared with that of the system using a conventional analog composite sequence. However, it can be obtained almost same BER performance of the system using a previous digital composite sequence by analog branch sequences.

关键词： bit error rate performance System performance direct-sequence code-division multiple access spreading sequence Hardware system COMMUNICATION SYSTEMS Computer Simulation Composites branches

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Performance of Multicell Multicarrier DS-CDMA System with Base-Station Cooperation

Performance of Multicell Multicarrier DS-CDMA System with Ba...

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1st International Conference on Connected Vehicles and Expo

作者： Ju, Xiaojie Yang, Lie-Liang Zhang, Youguang Beihang Univ Sch Elect & Informat Engn Beijing Peoples R China Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

ISBN: (纸本)9780769549002;9781467347051

In this contribution, we investigate the error performance of a uplink multicarrier direct-sequence code-division (DS-CDMA) system employing both time (T)-domain and frequency (F)-domain spreading, which is referred to as the TF/MC DS-CDMA system for convenience. A multicell scenario with universal frequency reuse is considered, when the multicarrier signals are transmitted over frequency-selective Rayleigh fading channels. A decentralized multiuser detection (MUD) scheme, which combines the novel receiver multiuser diversity aided multi-stage minimum mean-square error MUD (RMD/MS-MMSE MUD) with the hard-decision data exchanged among the neighboring base-stations (BSs), is proposed and compared with the conventional MUD schemes without BS cooperation. Additionally, detection of several users per stage is considered in the RMD/MS-MMSE MUD to make a tradeoff among the complexity, performance and delay. The impacts of the number of users detected per stage, system load, intercell interference strength, and the spreading factors of both T-domain and F-domain spreading are explored. Our simulation results demonstrate that the proposed scheme significantly outperforms the conventional MUD schemes without BS cooperation, and may constitute a promising multicell processing (MCP) scheme.

关键词： Multicarrier CDMA multicell cooperation mud CDMA mobile communications multicell direct-sequence code-division multiple access BASE STATION frequency reuse error performance Consumers

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Spectral-Efficiency Comparison of Multicell DS-CDMA/SDMA Systems with/without Base-Station Cooperation

Spectral-Efficiency Comparison of Multicell DS-CDMA/SDMA Sys...

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1st International Conference on Connected Vehicles and Expo

作者： Ju, Xiaojie Yang, Lie-Liang Zhang, Shuo Zhang, Youguang Beihang Univ Sch Elect & Informat Engn Beijing Peoples R China Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

ISBN: (纸本)9780769549002;9781467347051

In this contribution, we study the spectral-efficiency of uplink direct-sequence code-division multiple-access (DS-CDMA) and space-division multiple-access (SDMA) systems, which are operated in a double-cell scenario experiencing inter-cell interference. Our focus is on comparison of the achievable spectral-efficiency, when various base-station (BS) cooperation strategies and detection schemes are employed. Specifically, three BS operational schemes are considered, namely the ideal BS cooperation, data exchange only and no BS cooperation, in conjunction with four multiuser detection (MUD) schemes, including the optimum MUD (OMUD), OMUD with parallel interference cancellation (OMUD-PIC), linear minimum mean-square error MUD (MMSE-MUD) and the MMSE-based successive interference cancellation (MMSE-SIC). The impacts of system load, signal-to-noise ratio (SNR) and intercell interference strength on the achievable spectral-efficiency of the DS-CDMA and SDMA systems employing the above-mentioned BS cooperation and MUD schemes are investigated. Considering the trade-off between complexity and performance, our studies show that the MMSE-SIC aided by data exchange between BSs may constitute a promising multicell processing (MCP) scheme.

关键词： Multicell cooperation cooperative communication spectral efficiency spectral efficiency cooperative communication direct-sequence code-division multiple access Bahamas mud inter-cell interference BASE STATION multicell signal to noise ratios Space division multiple access

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DS-CDMA with M-ary Orthogonal Modulation for Wireless Sensor Networks Simultaneously Monitoring multiple Events

DS-CDMA with <i>M</i>-ary Orthogonal Modulation for Wireless...

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IEEE 75th Vehicular Technology Conference (VTC Spring)

作者： Sim, Ee How Yang, Lie-Liang Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

ISBN: (纸本)9781467309905;9781467309882

In this paper, we propose a novel WSN framework for one fusion center to monitor simultaneously multiple source events (SEs), each of which has multiple states. In the proposed WSN, every SE is observed by a range of local sensors, which convey their observations to the fusion center in the principles of direct-sequence code-division multiple-access (DS-CDMA) associated with M-ary orthogonal modulation (MOM). Therefore, the proposed WSN is referred to as the MOM DS-CDMA WSN. In the MOM DS-CDMA WSN, the local sensors monitoring the same SE transmit their signals to the fusion center in the principles of time-division multiple-access (TDMA), while the local sensors serving different SEs communicate with the fusion center in the principles of DS-CDMA. By making use of the advantages of MOM, the fusion center detects the SEs' states either coherently based on the maximal ratio combing (MRC) fusion rule, or non-coherently based on the equal gain combining (EGC) fusion rule. The detection performance of the fusion center is investigated by simulations. Specifically, the impacts of the number of SEs, the number of local sensors per SE, the observation reliability of local sensors, the reliability of the channels from local sensors to fusion center, etc., on the fusion detection performance are addressed.

关键词： direct-sequence code-division multiple access FUSION Sensors

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A Novel Synchronization Method for DS-CDMA Systems

A Novel Synchronization Method for DS-CDMA Systems

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8th IEEE International Wireless Communications and Mobile Computing Conference (IWCMC)

作者： Wan, Yi Chen, Zhongping Lanzhou Univ Inst Signals & Informat Proc Lanzhou 730000 Peoples R China

ISBN: (纸本)9781457713798

code division multiple access (CDMA) has been proven to be a promising spread-spectrum multiple access technique due to its advantages such as anti-interference capability and implementation versatility. However, the problem of the receiver side synchronization at the sub-chip scale can significantly increase the decoding error rate, just as the carrier frequency offset (CFO) problem does to the OFDM systems. So far the use of faster sampling clock at the receiver analog-to-digital converter (ADC) is generally thought to improve the receiving performance and has been implemented in practical communication hardware such as the STEL-2000A CDMA chip. In this paper we show that the traditional use of such scheme can introduce inter-chip interference that causes an error floor irrespective of the sampling rate. We further propose a novel synchronization method that uses a digital filter bank to automatically seek out the best synchronization solution. Simulation results show that the proposed method performs almost as good as the case of perfect synchronization and far better than when there is a clock disparity. The proposed algorithm is also implemented in field programmable gate array (FPGA) and compared with the traditional approach to pave the way for its practical chip-level implementation.

关键词： CDMA mobile communications code division multiple access Field programmable gate arrays error floor carrier frequency offset direct-sequence code-division multiple access sampling rate

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Robust blind multiuser detection in DS-CDMA systems over Nakagami-m fading channels with impulsive noise including MRC receive diversity

Robust blind multiuser detection in DS-CDMA systems over Nak...

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International Conference on Signal Processing and Communication Systems, ICSPCS

作者： Vinay Kumar Pamula Srinivasa Rao Vempati Habibulla Khan Anil Kumar Tipparti Department of ECE MIC College of Technology Kanchikacherla India Department of ECE Anurag Engineering College Kodad India Department of ECE KL University Vaddeswaram India Department of ECE Anurag College of Engineering Ghatkesar India

ISBN: (纸本)9781467323925

This paper presents robust blind multiuser detection in direct sequence-code division multiple access systems (DS-CDMA) over Nakagami-m fading channels with impulsive noise including maximal-ratio combining diversity. An M-estimator based structure for non-coherent demodulation of differentially phase shift keyed (DPSK) signals transmitted over a synchronous CDMA flat-fading Nakagami channels with impulsive noise is studied and analyzed. A new M-estimator is proposed for robustifying the detector and an approximate expression for average probability of error of non-coherent DPSK signals is derived using an approximation to generalized Marcum-Q function over single-path Nakagami-m fading channels. Simulation results are presented to evaluate the performance of the proposed robust blind multiuser detector in comparison with the linear decorrelating detector, Huber and Hampel estimator based detectors.

关键词： blind multiuser detection CDMA impulsive noise influence function maximal ratio combiner M-estimator Nakagami-m distribution probability of error. Impulse noise Multiuser detection influence function direct-sequence code-division multiple access code division multiple access CDMA mobile communications average probability Fading channels MAINTENANCE REQUIREMENT CARD diversity reception Blind

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Performance Evaluation and Comparison between Iterative DS-CDMA and NDMA

Performance Evaluation and Comparison between Iterative DS-C...

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IEEE Vehicular Technology Conference

作者： Francisco Ganhao Rui Dinis Luis Bernardo Rodolfo Oliveira IT Instituto de Telecomunicacoes Portugal CTS Uninova Dep. de Eng Electrotecnica Faculdade de Ciencias e Tecnologia FCT Universidade Nova de Lisboa CTS Uninova Dep. de Eng ElectrotecnicaFaculdade de Ciencias e Tecnologia FCT Universidade Nova de Lisboa

ISBN: (纸本)9781467318808

Multipacket Reception (MPR) techniques employing either direct sequence code division multiple access (DS-CDMA) or Network Diversity multiple access (NDMA) have great potential to deal with packet collisions from multiple Mobile Terminals (MTs). However, their performance evaluation in practical systems is difficult because lengthy simulations are needed to obtain the packet error rates for specific channel conditions. This paper considers MPR receivers based on the Iterative Block Decision Feedback Equalization (IB-DFE) concept. An analytical tool that computes the Bit Error Rate (BER) and Packet Error Rate (PER) for DS-CDMA is proposed, where its theoretical results have a good accuracy. This analytical approach, that provides a simple and relatively fast way to compute the BER and PER performance for DS-CDMA, is then employed for a comparison with NDMA. '

关键词： SC-FDE D3-DFE Multipacket Detection Analytical Performance DS-CDMA NDMA ARQ direct-sequence code-division multiple access Bit error rate Error analysis Performance Evaluation Shortcuts Packet Iterative

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BEP and Throughput Analysis of Incremental Selective Relaying in DS-CDMA Systems

BEP and Throughput Analysis of Incremental Selective Relayin...

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IEEE Vehicular Technology Conference

作者： Hela Hakim Hatem Boujemaa Wessam Ajib Carthage University Higher School of Communication of Tunis Department of Computer Sciences Universite de Quebec a Montreal

ISBN: (纸本)9781467318808

In this paper, we derive exact form expressions for the Bit Error Probability (BEP) and throughput of cooperative direct sequence-code division multiple access (DS-CDMA) systems using incremental selective relaying which combines selective relaying with incremental relaying protocols in the presence of multipath propagation. The derived results are valid for any multipath intensity profile of the channel and any path delays. They also consider the correlation of the multipath gains. Simulation results along with analytical studies of BEP and throughput prove that the combination of incremental relaying with selective relaying in cooperative DS-CDMA systems improve significantly the throughput performance and can achieve the maximum possible spatial diversity when it is required by destination.

关键词： CDMA mobile communications direct-sequence code-division multiple access relaying Throughput selective relay Incremental Multipath propagation

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IBI Cancellation and Circular Property Restoration for Broadband DS-CDMA Using FDE without CP Insertion

IBI Cancellation and Circular Property Restoration for Broad...

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IEEE Vehicular Technology Conference

作者： Min Zheng Wei Peng Fumiyuki Adachi Dept. of Electrical and Communication Engineering Graduate School of Engineering Tohoku University

ISBN: (纸本)9781467318808

In broadband DS-CDMA uplink transmission using frequency-domain equalization (FDE) without cyclic prefix (CP) insertion, the transmission performance degrades due to inter block interference (IBI) and circular property loss. In this paper, IBI cancellation and circular property restoration is proposed and the performance improvement is evaluated by computer simulation. It is shown that IBI cancellation & circular property restoration can improve the bit error rate (BER) performance in a frequency-selective Rayleigh fading channel. It is also shown that circular property restoration is more powerful than the IBI cancellation.

关键词： DS-CDMA MMSE-FDE IBI cacekllation Circular property restoration CANCELLATIONS direct-sequence code-division multiple access restoration performance boost circular Transmission Characteristics broadband

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