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COMBINED ADAPTIVE RAKE DIVERSITY (ARD) AND CODING FOR DPSK DS CDMA MOBILE RADIO

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1993年第7期11卷 1076-1084页

作者： HIGASHI, A MATSUMOTO, T NIPPON TELEGRAPH & TEL PUBL CORP MOBILE COMMUN NETWORK INC YOKOSUKA JAPAN KEIO UNIV TOKYO 108 JAPAN

A new diversity combining scheme, adaptive RAKE diversity (ARD), is proposed for differential PSK direct sequence code division multiple access (DS/CDMA) mobile communications system. The ARD scheme aims to minimize the mean squared errors in the diversity combiner output. This suppresses the effects of the interference only paths in the time window for path diversity combining. Bit error rate (BER) performances with the proposed ARD and conventional equal gain combining (EGC) schemes are evaluated through laboratory experiments and compared. Block error rate (BKER) performance with the ARD scheme is also evaluated experimentally. Based upon the BKER evaluation results, a new error correction scheme is proposed that is suitable for error occurrence characteristics of ARD output.

关键词： Differential quadrature phase shift keying Multiaccess communication Diversity reception Bit error rate Performance evaluation Error correction Differential phase shift keying direct-sequence code-division multiple access Mobile communication Interference suppression

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direct-sequence CDMA POWER-CONTROL, INTERLEAVING, AND CODING

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1993年第7期11卷 1085-1095页

作者： SIMPSON, F HOLTZMAN, JM RUTGERS UNIV DEPT ELECT & COMP ENGN WINLAB PISCATAWAY NJ 08855 USA

We develop and analyze models of power control working with other aspects of CDMA systems, such as interleaving and coding on the land/mobile radio channel. Our orientation is that a power control scheme is keeping the received powers at the base station ''almost equal,'' and we will be quantifying the performance degradation incurred if the powers are not exactly equal. In doing so, we consider the performance implications of control latency and a maximum speech delay constraint. It turns out that because of positive correlations between the fading channel amplitudes, the effectiveness of the combination of interleaving and coding in combating the effects of power variations due to slow Rayleigh fading is reduced. It is shown however, that power control and interleaving/coding are most effective in complementary parameter regions, thus providing a degree of robustness for both fast and slow Rayleigh fading.

关键词： BASE STATION Equal direct-sequence code-division multiple access Power control Rayleigh fading code division multiple access degradation of performance land mobile radio coding

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On channel coding and multiuser detection for DS-CDMA

On channel coding and multiuser detection for DS-CDMA

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International Conference on Universal Personal Communications

作者： P. Hoeher Institute for Communications Technology German Aerospace Research Establishment (DLR) Oberpfaffenhofen Germany AT and T Bell Laboratories Inc. Murray Hill NJ USA

Two issues concerning direct-sequence code-division multiple access (DS-CDMA) multiuser detection are addressed: Reliability estimation (i.e., soft-output detection), and a complexity reduction technique to simplify the optimum (maximum-likelihood) multiuser detector. The soft-outputs are not only suitable for improving the performance of a next stage (in this study an outer soft-decision Viterbi decoder), but also for reducing the complexity of the multiuser detector itself. In this way, a family of suboptimum multiuser detectors with adjustable performance/complexity tradeoff is obtained in a structured manner from the optimum multiuser detector. Reliability generation is applied by post-processing hard decisions of an auxiliary (single or multiuser) detector delivering tentative decisions given matched filter outputs. Reduced-complexity multiuser detection is based on exhaustively searching only in a subset of unreliable decisions given the reliability estimates. A decision-feedback mechanism is shown to be included. In particular it is indicated that the decision-feedback multiuser detector is outperformed on a Gaussian channel, and that almost all multiuser interference is cancelled out in a coded multiuser system in Rayleigh fading, i.e., in a severe near-far situation. The latter result corresponds to a gain on the order of 4 dB at a bit error rate of 10 compared to conventional detection, or a loss of only about 1 dB compared to single user system.

关键词： Channel coding Multiuser detection Multiaccess communication Detectors direct-sequence code-division multiple access Maximum likelihood detection Maximum likelihood estimation Viterbi algorithm Maximum likelihood decoding Matched filters

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On the optimum DS-CDMA channel bandwidth for personal communication systems

On the optimum DS-CDMA channel bandwidth for personal commun...

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IEEE Conference on Vehicular Technology (VTC)

作者： S.A. Allpress M.A. Beach J.P. McGeehan Centre for Communications Research (CCR) University of Bristol Bristol UK

The authors discuss some of the issues concerning the optimum spread spectrum bandwidth for use in proposed third-generation direct sequence code division multiple access (DS-CDMA) systems, such as the European Universal Mobile Telecommunications System (UMTS), based upon recent system-specific wideband channel sounding measurements in the city of Bristol combined with results from computer simulation of a RAKE receiver architecture.

关键词： Multiaccess communication Bandwidth Spread spectrum communication direct-sequence code-division multiple access Mobile computing 3G mobile communication Wideband Cities and towns Computer simulation Fading

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RAKE decorrelation as an alternative to rapid power control in DS-CDMA mobile radio

RAKE decorrelation as an alternative to rapid power control ...

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IEEE Conference on Vehicular Technology (VTC)

作者： S.S.H. Wijayasuriya J.P. McGeehan G. Norton Centre for Communications Research University of Bristol Bristol UK

The sliding window decorrelating algorithm (SLWA) for asynchronous multi-user DS-CDMA (direct sequence code division multiple access) systems has previously been proposed. In mobile radio networks, the feasibility of overcoming the near-far problem using power control strategies is questionable at practical vehicle speeds. An alternative to rapid power control is proposed which incorporates both the RAKE diversity reception concept and the SLWA. Decorrelation is thus achieved between individual users and their significant multi-paths. A mathematical model is presented for the receiver in conjunction with simulation and numerical results which show capacity enhancements over the conventional linear correlation receiver (CLCR) and lead to ideas on a positioning strategy for decorrelating solutions in DS-CDMA mobile radio.

关键词： Decorrelation Power control Multiaccess communication Land mobile radio RAKE receivers direct-sequence code-division multiple access Vehicles Diversity reception Mathematical model Numerical simulation

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DS-CDMA/polling transmission protocol for personal communication networks

DS-CDMA/polling transmission protocol for personal communica...

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International Conference on Universal Personal Communications

作者： C. Trabelsi A. Yongacoglu Department of Electrical Engineering University of Ottawa Ottawa ONT Canada Ottawa University Ottawa KS US Dept. of Electr. Eng. Ottawa Univ. Ont. Canada

In this paper an efficient direct sequence code division multiple access (DS-CDMA) transmission protocol is proposed for centralized packet radio networks. This protocol reduces the central station complexity while maintaining the throughput at an acceptable level. First the authors propose a partial DS-CDMA protocol which reduces the number of receivers required at the central station. The central station complexity reduction is usually obtained at the price of throughput reduction. Then to mitigate the problem of throughput reduction, a new protocol which uses DS-CDMA in conjunction with polling is proposed to increase the throughput while maintaining the complexity reduction of the central station.

关键词： Multiaccess communication Personal communication networks Throughput access protocols Traffic control Receivers Packet radio networks direct-sequence code-division multiple access Viterbi algorithm Spread spectrum communication

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A Comparison of Cdma and Frequency Hopping in a Cellular Environment

A Comparison of Cdma and Frequency Hopping in a Cellular Env...

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IEEE International Symposium on Information Theory

作者： M.I. Mandell R.J. McEliece California Institute of Technology Pasadena CA USA

This paper compares the performances of direct sequence code division multiple access (CDMA) and Frequency Hopping (FH) schemes in a cellular multiuser environment. Our multiuser channel model incorporates the effects of propagation, frequency selective fading, and interference among users in the presence of a constrained system bandwidth. The CDMA and FH systems are compared using BPSK modulation. The main point of contrast between these systems is that the orthogonal hopping patterns in a FH system result in a decreased additive interference power, however the frequency spreading nature of CDMA results in the ability to combat fading. An information theoretic analysis is presented, which shows that system capacity is larger for CDMA than for FH. Hence, for this channel, with sufficient coding the CDMA system can achieve a higher level of performance than the FH system. However, it is unclear what level of complexity would be required to achieve such performance, and what effect such complexity would have on the practicality of the system.

关键词： Multiaccess communication Interference Fading Frequency conversion Delay effects Interleaved codes Performance evaluation Communication system traffic control direct-sequence code-division multiple access Multiuser channels

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Coexistence of cellular CDMA and FSM: interference suppression using filtered PN sequences

Coexistence of cellular CDMA and FSM: interference suppressi...

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Proceedings of GLOBECOM '93. IEEE Global Telecommunications Conference

作者： K.G. Filis S.C. Gupta Electrical Engineering Dept Southern Methodist University Dallas TX USA

The spectrum sharing between a direct sequence code division multiple access personal communications network (DS CDMA PCN) and the fixed service microwave (FSM) radio links in the 1850 to 1990 MHz band is investigated. The spectrum coexistence of the two systems will improve spectral efficiency, but it will cause interference to both systems. To reduce the interference, the spread spectrum (SS) technique is used in the PCN. In addition a CDMA PCN transmitter is designed, employing filtered pseudonoise (PN) sequences, that reduce the interference to the FSM systems. The performance of the FSM under the overlaid filtered PCN is studied. Next, a CDMA PCN receiver is designed, employing filtered PN sequences, and the performance of the filtered PCN, under FSM interference, is evaluated in terms of the CDMA capacity reduction.< >

关键词： Multiaccess communication Interference suppression Personal communication networks Radio link Microwave filters Mobile antennas direct-sequence code-division multiple access Microwave theory and techniques Spread spectrum communication Radio transmitters

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Digital cellular over the cable television fiber-optic plant

Digital cellular over the cable television fiber-optic plant

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International Conference on Universal Personal Communications

作者： V. O'Byrne GTE Laboratories Inc. Waltham MA USA

The author addresses some of the issues in transporting wireless communication signals over the cable television network from a systems point of view. It is shown that direct sequence code division multiple access (DS-CDMA) requires relatively inexpensive lasers, costing less than one quarter the price of those required for time division multiple access (TDMA) and the present analog cellular systems. CDMA type systems are also less sensitive to optical reflections and thus they require less additional system engineering when employed over the CATV fiber optic plant, thus reducing the overall system complexity.< >

关键词： Cable TV Optical fiber cables Multiaccess communication Time division multiple access Optical fiber communication Wireless communication direct-sequence code-division multiple access Fiber lasers Costing Optical reflection

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A comparison of CDMA and frequency hopping in a cellular environment

A comparison of CDMA and frequency hopping in a cellular env...

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International Conference on Universal Personal Communications

作者： M.I. Mandell R.J. McEliece California Institute of Technology Pasadena CA USA

This paper compares the performances of direct sequence code division multiple access (CDMA) and frequency hopping (FH) schemes in a cellular multiuser environment. The multiuser channel model incorporates the effects of propagation, frequency selective fading, and interference among users in the presence of a constrained system bandwidth. This channel model is applicable for cellular mobile communications, as well as other forms of personal communications. The CDMA and FH systems are compared using BPSK modulation. The main point of contrast between these systems is that the orthogonal hopping patterns in a FH system result in a decreased additive interference power, however the frequency spreading nature of CDMA results in the ability to combat fading. An information theoretic analysis is presented, which shows that system capacities are far above the performances achieved using simple coding schemes.< >

关键词： Multiaccess communication Fading direct-sequence code-division multiple access Frequency conversion Spread spectrum communication Multiuser channels Interference constraints Bandwidth Power system modeling Mobile communication

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