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IEEE Conference on Vehicular Technology (VTC)

作者： M.J. Klok G. Hooghiemstra T. Ojanpera R. Prasad Centre for Wireless Personal Communications IRCTR Netherlands Faculty of Information Technology and Systems Delft University of Technnology Delft Netherlands Nokia Group Nokia Telecommunications Finland Centre for Wireless Personal Communications IRCTR

Considering the importance of DS-CDMA for the third generation mobile communication systems, evaluating the performance of DS-CDMA systems is crucial. Several techniques have been developed to evaluate DS-CDMA system performance, each with its (dis)advantages. In this paper a novel technique is presented, which is accurate and simple. Furthermore, a range of scenarios can be captured in one formula.

关键词： Multiaccess communication System performance Gaussian approximation AWGN Frequency synchronization Power system modeling Wireless communication Information technology direct-sequence code-division multiple access 3G mobile communication

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Impact of timing error on the performance of multiuser detection in multirate CDMA systems

Impact of timing error on the performance of multiuser detec...

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IEEE International Conference on Personal Wireless Communication

作者： M. Alam T. Ojanpera R. Prasad Siemens The Hague Netherlands Nokia Nokia Group Finland CEWPC Delft University of Technology Delft Netherlands

This paper presents the impact of timing error on the performance of multirate direct sequence code division multiple access (DS-CDMA) systems based on variable spreading factor (VSF) using multiuser detection techniques such as the parallel interference cancellation (PIC) detector. The performance is evaluated for a single-rate and a three-rate system using Monte-Carlo simulation in the additive white Gaussian noise (AWGN) channel without multipath fading. The bit error probability (BEP) of the matched filter (MF) and the PIC detector with and without timing errors are compared.

关键词： Timing Multiuser detection AWGN Detectors direct-sequence code-division multiple access Multiaccess communication Interference cancellation Additive white noise Fading Error probability

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Soft-decoder feedback aided space-time processing in multiuser interference suppression

Soft-decoder feedback aided space-time processing in multius...

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IEEE Conference on Wireless Communications and Networking

作者： J. Thomas E. Geraniotis Department of Electrical and Computer Engineering and Institute for Systems Research University of Maryland College Park MD USA

This work presents a soft iterative minimum mean square error (MMSE) multiuser interference suppressor for coded direct sequence code division multiple access (CDMA) uplink channels that employ space-time processing at both the mobile transmitters and the base station receiver. With a new equivalent discrete-time synchronous model for randomly spread asynchronous multiuser CDMA channels, we develop an iterative scheme that exchanges soft information between an MMSE multiuser demodulator (that also concurrently performs subtractive interference cancellation) and a bank of single-user decoders. It performs well both at low and high received signal powers, and displays the successive cancellation property across iterations, exhibiting good near-far resistance. Introducing multisensor arrays at the receiver relaxes the limitations imposed by the inherent suboptimality of MMSE multiuser demodulation, in so far as it enhances interuser separation, now in the spatial sense, and thereby allows significant overload capability. Further, this work explores new territory by studying multisensor transmission in multiuser channels. A new multisensor block modulation scheme called space-time spreading, for mobile transmitters is proposed; it is observed to provide significant benefits especially when the spatial separation afforded by the use of multisensor receiver arrays, is otherwise limited.

关键词： Feedback Multiaccess communication Transmitters Demodulation Mean square error methods Interference suppression direct-sequence code-division multiple access Base stations Interference cancellation Iterative decoding

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An adaptive pilot symbol-aided MMSE receiver in fading channels

An adaptive pilot symbol-aided MMSE receiver in fading chann...

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IEEE International Conference on Communications (ICC)

作者： Seong Rag Kim Young Gyun Jeong In-Kyeong Choi Seoyoung Lee Radio & Broadcasting Technology Laboratory Electronics and Telecommunications Research Institute Taejon South Korea

Realistic direct sequence code division multiple access (DS/CDMA) channels are severely time-varying. Standard minimum mean squared error (MMSE) receivers have various problems in tracking the rapidly changing channel characteristics in fading environments. In addition, they require a training sequence for their adaptation. This paper presents a constrained MMSE receiver with a modified MMSE criterion. The constrained MMSE receiver is adaptively implemented using the orthogonal decomposition-based least mean square (LMS) algorithm. In order to improve the accuracy of the reference signal and channel estimates, a pilot symbol-aided scheme is employed. It also makes the proposed MMSE receiver not require any separate training sequence. The simulation results show that the proposed MMSE receiver provides significant performance improvements in bit error rate (BER) over the conventional matched filter (MF) receiver and the currently available MMSE receivers, and is insensitive to the speed of Rayleigh fading.

关键词： Fading Receivers Adaptive filters Multiaccess communication Bit error rate Signal to noise ratio direct-sequence code-division multiple access Least squares approximation Matched filters Binary phase shift keying

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Multi-carrier DS-CDMA using frequency spread coding

Multi-carrier DS-CDMA using frequency spread coding

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IEEE International Conference on Personal Wireless Communication

作者： H. Matsutani M. Nakagawa Department of Electrical Engineering Faculty of Science and Technology Keio University Kanagawa Japan

A multi-carrier direct sequence code division multiple access (MC-DS-CDMA) system combined with frequency spread coding is proposed and investigated for the downlink. The proposed system exploits frequency diversity without additional redundancy by using frequency spread coding in a frequency-selective fading channel. Computer simulation results show its effectiveness in terms of average bit error rate and bandwidth efficiency. Furthermore, the proposed system is compared with a multi-carrier (MC)-CDMA system and a single-carrier (SC)-DS-CDMA system using a RAKE receiver.

关键词： Multiaccess communication Frequency diversity direct-sequence code-division multiple access Frequency conversion Downlink Redundancy Frequency-selective fading channels Computer simulation Bit error rate Bandwidth

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An analysis on the effect of the number of phases in multipath fading DS-CDMA signature sequences

An analysis on the effect of the number of phases in multipa...

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MILCOM, Military Communications Conference

作者： So Ryoung Park Iickho Song Seokho Yoon Jooshik Lee Seong Ro Lee Department of Electrical Engineering Korea Advanced Institute of Science and Technology Daejeon South Korea Department of Electronics Engineering Mokpo슠National University Mokpo Jeollanam South Korea

direct sequence code division multiple access (DS-CDMA) communication systems using random polyphase sequences with coherent reception in multipath fading channels are considered. By examining the asymptotic characteristics of the multiple access interference and multipath interference, we show that the DS-CDMA system performance with random m/sub p/-phase sequences of m/sub p//spl ges/3 is better than that with random binary sequences in multipath fading environment.

关键词： Fading Multiaccess communication Random variables AWGN Interference Frequency Binary sequences direct-sequence code-division multiple access Random sequences Performance analysis

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Extended MMSE receiver for multiuser interference rejection in multipath DS-CDMA channels

Extended MMSE receiver for multiuser interference rejection ...

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IEEE Conference on Vehicular Technology (VTC)

作者： F. Petre M. Engels A. Bourdoux B. Gyselinckx M. Moonen H. De Man Inter University Micro Electronics Center Heverlee Belgium E.E. Department ESAT/SISTA FWO Leuven Belgium IMEC Leuven Belgium

The conventional minimum mean squared error (MMSE) receiver which actively suppresses multiuser interference (MUI), outperforms the RAKE receiver for direct sequence code division multiple access (DS-CDMA) in multipath slow fading channels. However the performance gap between the conventional MMSE receiver and the theoretical bound is still large. We therefore propose an extended MMSE receiver which spans three symbol intervals the desired symbol interval as well as the previous and the next symbol interval. The extended MMSE receiver outperforms the conventional MMSE receiver especially for large system load and large number of propagation paths in the channel. Its computational complexity is approximately three times the complexity of the conventional MMSE receiver but still independent of the number of active users and the number of paths in the channel. As a consequence the extended MMSE receiver allows a low-complexity low-power implementation in the mobile user-terminal for communication over multipath slow fading channels in the forward link.

关键词： Multiaccess communication Fading Multipath channels RAKE receivers Delay Interference suppression Computational complexity Mobile communication direct-sequence code-division multiple access Cellular networks

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Performance of narrowband interference suppression filters in a direct sequence code division multiple access system

Performance of narrowband interference suppression filters i...

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International Conference on Universal Personal Communications

作者： Youngkwon Cho Jae Hong Lee School of Electrical Engineering Seoul National University Seoul South Korea

Narrowband interference (NBI) suppression filters can substantially improve the interference suppression capability of direct sequence code division multiple access (DS/CDMA) systems under the frequency overlay situation. Analytical expressions for the performance of NBI suppression filters are derived and evaluated. A one-sided predictor with decision feedback improves the interference suppression capability much more than a linear two-sided interpolator without decision feedback and its performance is nearly independent of the number of code division multiple access (CDMA) users.

关键词： Narrowband Interference suppression Filters Multiaccess communication Feedback direct-sequence code-division multiple access Frequency conversion Performance analysis

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Adaptive receiver for DS/CDMA communications over impulsive noise channels

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ELECTRONICS LETTERS 1998年第5期34卷 425-427页

作者： Hwang, HC Wei, CH Natl Chiao Tung Univ Dept Elect Engn Hsinchu 30050 Taiwan Natl Chiao Tung Univ Ctr Telecommun Res Hsinchu 30050 Taiwan

A new adaptive algorithm is proposed for training soft-limiter based correlation receiver in which the direct sequence code division multiple access signals corrupted by impulsive symmetric a-stable noise are demodulated. The new adaptation algorithm allows simpler implementation and faster convergence speed in comparison with the traditional adaptive stochastic gradient-based algorithms.

关键词： direct-sequence code-division multiple access adaptive receiver Communication Research Impulse noise coherent receiver

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Wideband DS-CDMA for next-generation mobile communications systems

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IEEE COMMUNICATIONS MAGAZINE 1998年第9期36卷 56-69页

作者： Adachi, F Sawahashi, M Suda, H NTT Mobile Commun Network Inc Yokosuka Kanagawa Japan

Wideband wireless access based on direct sequence code division multiple access aimed at third-generation mobile communications systems is reviewed. W-CDMA is designed to flexibly offer wideband services which cannot be provided by present cellular systems, with various data rates as high as 2 Mb/s. The important concept of W-CDMA is the introduction of intercell asynchronous operation and the pilot channel associated with individual data channels. Intercell asynchronous operation facilitates continuous system deployment from outdoors to indoors. Other technical features of W-CDMA include fast cell search under intercell asynchronous operation, fast transmit power control, coherent spreading code tracking, a coherent Rake receiver, orthogonal multispreading factor forward link, and variable-rate transmission with blind rate detection. The introduction of the data-channel-associated pilot channel allows W-CDMA to support interference cancellation and adaptive antenna array techniques that can significantly increase the link capacity and coverage. This article presents radio link performance evaluated by computer simulation. Field experiment radio link performance results are also presented.

关键词： Wideband Multiaccess communication Mobile communication Adaptive arrays Radio link direct-sequence code-division multiple access Continuous time systems Power control Fading Multipath channels

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