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On the accuracy of Gaussian approximations in the error analysis of DS-CDMA with OQPSK modulation

IEEE TRANSACTIONS ON COMMUNICATIONS 2002年第12期50卷 2064-2071页

作者： Landolsi, MA Stark, WE King Fahd Univ Petr & Minerals Dept Elect Engn Dhahran 31261 Saudi Arabia Univ Michigan Dept Elect Engn & Comp Sci Ann Arbor MI 48109 USA

This paper considers the bit error probability analysis of direct-sequence code-division multiple access with offset quadrature phase-shift keying (OQPSK) modulation and random signature sequences. A statistical characterization of the decision variable at the output of the correlation receiver is obtained. and several techniques for evaluating the error performance, previously derived for binary phase-shift keying (BPSK)-modulated systems, are then extended to the case of OQPSK. This includes exact bit error evaluation, as wen as various approximation methods based on Gaussian modeling of the multiple-access interference terms. These techniques known as the standard and improved Gaussian approximations, have increasing complexity depending on the level of accuracy required. For BPSK the standard approximation is typically found to be inaccurate, unless the number of users becomes large, and only the improved approximation yields sufficient accuracy in general. But for the case of OQPSK, the relative performance comparison developed in this paper shows that, for all practical purposes, the simple standard approximation is surprisingly very accurate even with a small number of users.

关键词： direct-sequence code-division multiple access (DS-CDMA) Gaussian approximation methods offset quadrature phase-shift keying (OQPSK)

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Capacity of chaos-based asynchronous DS-CDMA systems with exponentially vanishing autocorrelations

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ELECTRONICS LETTERS 2002年第25期38卷 1717-1718页

作者： Mazzini, G Rovatti, R Setti, G Univ Ferrara CEG DI I-44100 Ferrara Italy Univ Bologna CEG ARCES I-40136 Bologna Italy

A receiver for synchronous DS-CDMA systems is proposed with a decision window that is aligned to encompass two half bits of each user. Such a receiver is compared with the classical one in terms of Shannon capacity showing a definite improvement. Based on this, traditional upper bounds and optimality criteria on the capacity of synchronous DS-CDMA systems are revised.

关键词： Autocorrelation direct-sequence code-division multiple access CDMA mobile communications Asynchronous Receivers

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Outage probability throughput and delay analysis of cellular DS CDMA system in the presence of correlated signal and interference

Outage probability throughput and delay analysis of cellular...

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Asia-Pacific Conference on Circuits and Systems

作者： Rattanakoch, W Kimpan, C Pin-Ngern, O Noppanakeepong, S King Mongkuts Inst Technol Fac Engn Bangkok 10520 Thailand

ISBN: (纸本)0780376900

In this paper, to evaluate the performance of cellular DS-CDMA system, by taking into account the correlation between signal and interference, to determined outage probability throughput and delay for the reverse link with power control error. The numerical results show that when the correlation considered the outage probability decreased, the throughput value increased, that is, the performance can be achieved.

关键词： Delay direct-sequence code-division multiple access Interference Multiaccess communication Power control Quality of service Radio link Random variables Signal analysis Throughput

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Narrowband interference suppression in multipath CDMA system

Narrowband interference suppression in multipath CDMA system

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IEEE Conference on Wireless Communications and Networking

作者： O.C. Ugweje Department of Electrical and Computer Engineering University of Akron Akron OH USA

ISBN: (纸本)0780373766

As a means of suppressing interference, this paper analyzes the effect of filtering and diversity on the bit error rate performance of a direct sequence code division multiple access (DS-CDMA) overlay system. The system is analyzed in terms of the interference-to-signal power, ratio of interference bandwidth to spread spectrum bandwidth, order of diversity, multipath intensity profile and number of users. The performance of the system with and without filters is compared. It is shown that the use of filtering and diversity results in performance improvement compared to a system without filtering or system without diversity or both.

关键词： Narrowband Interference suppression Multiaccess communication Filtering Bandwidth Performance analysis Bit error rate direct-sequence code-division multiple access Spread spectrum communication Filters

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Chip interleaved turbo codes for DS-CDMA in a Rayleigh fading channel with diversity reception

Chip interleaved turbo codes for DS-CDMA in a Rayleigh fadin...

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IEEE Conference on Vehicular Technology (VTC)

作者： D. Garg F. Adachi Electrical and Communication Engineering Graduate School of Engineering University of Tohoku Sendai Japan

A new channel interleaving method, called chip interleaving, for direct sequence code division multiple access (DS-CDMA) mobile radio is proposed. Chip interleaver scrambles the chips and transforms the transmission channel into a highly time-selective or highly memoryless channel. It was found that the turbo decoding performance which degrades in a fading channel is significantly improved with chip interleaving. It was also found that the bit error rate (BER) performance improves with increasing spreading factor (SF) and increasing frame length. Chip interleaving is effective in the presence of antenna diversity as well, however the improvement decreases with the increase in the number of antennas.

关键词： Turbo codes Multiaccess communication Fading Diversity reception Interleaved codes Bit error rate direct-sequence code-division multiple access Land mobile radio Memoryless systems Decoding

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Capacity and transmission power estimation of two-hop CDMA cellular system

Capacity and transmission power estimation of two-hop CDMA c...

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International Symposium on Wireless Personal Multimedia Communications (WPMC)

作者： K. Yamamato H. Murata S. Yoshida A. Fujiwara T. Otsu Y. Yamao Graduate Sch. of Informatics Kyoto Univ. Japan Graduate School of Informatics Kyoto University Sakyo-ku Kyoto Japan NTT DoCoMo Yokosuka Kanagawa Japan

This paper describes a novel direct sequence code division multiple access (DS-CDMA) cellular system where a relaying function is introduced to mobile terminals. By using a relay, a considerable transmit power reduction might be achieved. Particularly, those terminals located in the shadowing region or in the cell edge are able to reduce the transmit power by asking a nearby terminal with low propagation loss to the base station to relay its signal. For relaying, the same frequency bands that are already allocated are assumed to be reused. This might cause an excessive interference due to the uncoordinated frequency reuse. To clarify these points, a two-hop DS-CDMA cellular system and a conventional DS-CDMA cellular system without relaying are compared in terms of the user capacity and transmit power. Simulation results reveal that the system capacity can be increased by using a sophisticated routing scheme.

关键词： Multiaccess communication Power system relaying direct-sequence code-division multiple access Shadow mapping Propagation losses Base stations Radio spectrum management Interference Frequency Routing

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Blind joint equalization and multiuser detection in dispersive MC-CDMA/MC-DS-CDMA/MT-CDMA channels

Blind joint equalization and multiuser detection in dispersi...

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MILCOM, Military Communications Conference

作者： W. Nabhane H.V. Poor Department of Electrical Engineering Princeton University Princeton NJ USA Department of Electrical Engineering Princeton University Princeton NJ

The problem of demodulation of multiuser orthogonal frequency division multiplex-code division multiple access (OFDM-CDMA) in the presence of both multiple access interference (MAI) and intersymbol interference (ISI) is considered. Three types of OFDM-CDMA are presented: multicarrier code division multiple access (MC-CDMA), multicarrier direct sequence code division multiple access (MC-DS-CDMA) and multi-tone code division multiple access (MT-CDMA). The dispersive OFDM-CDMA channel is first cast into a multiple input multiple output (MIMO) signal framework. Then, using a subspace method, it is shown that each user's channel impulse response can be estimated using the knowledge of the user's signature waveform. It is further shown that, using the user's channel impulse response and the identified signal subspace, a blind linear minimum mean square error (MMSE) detector and a blind zero-forcing decorrelator detector can be constructed in closed form. The proposed detectors are attractive for their higher spectral efficiency, which is achieved by the elimination of cyclic prefix and training sequences. Further a comparison of MC-CDMA/MC-DS-CDMA/MT-CDMA with direct sequence code division multiple access (DS-CDMA) is then presented. The paper's major contribution is the development of the sub-space blind techniques.

关键词： Blind equalizers Multiuser detection Dispersion Multicarrier code division multiple access Detectors multiple access interference Intersymbol interference direct-sequence code-division multiple access Multiaccess communication MIMO

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Minimizing deviation from service curve in forward link of DS-CDMA network

Minimizing deviation from service curve in forward link of D...

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IEEE Conference on Vehicular Technology (VTC)

作者： P. Ramanathan Lun Tong Department of Electrical and Computer Engineering University of Wisconsin Madison USA

In a direct sequence code division multiple access (DS-CDMA) based cellular network, meeting the diverse quality of service (QoS) needs of mobile hosts (MHs) is a challenge because of the fluctuations in the quality of the wireless channel. The QoS needs of the MHs application are modelled using a service curve. Furthermore, a notion of deviation is introduced as a measure of meeting the service curve. The paper describes a forward link scheme whose primary objective is to minimize system deviation from the service curve and the secondary objective is to maximize the system throughput. The solution includes constraints on the transmit power of the base station (BS), number of spreading codes and target signal-to-interference-plus-noise ratio (SINR) for the MHs.

关键词： Intelligent networks Multiaccess communication Quality of service Throughput Signal to noise ratio Wireless networks direct-sequence code-division multiple access Land mobile radio cellular systems Fluctuations Base stations

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Recursive algorithms for multiuser detection over DS/CDMA channels

Recursive algorithms for multiuser detection over DS/CDMA ch...

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IEEE International Symposium on Spread Spectrum Techniques and Applications

作者： A. De Maio R. Episcopo M. Lops A. Pauciullo Universita di NapoliE2809CFcdcrico 11E2809D Napoli Italy Universita degli Studi di Cassino Cassino Frosinone Italy

We consider the problem of reduced-complexity detection for the synchronous Gaussian direct-sequence code-division multiple access (DS/CDMA) channel. This interest stems from the high computational complexity connected with the implementation of the optimum maximum likelihood (ML) multiuser receiver and from the very poor resistance of the linear receivers to overloaded scenarios, especially in the presence of imperfect power control. We introduce a new family of iterative receivers which yields a very fast convergence with an affordable computational complexity. Moreover the performance assessment conducted via Monte Carlo techniques shows that the novel receivers outperform the linear detectors and achieve a bit error rate close to the optimum even when the number of users approaches the processing gain.

关键词： Multiuser detection Multiaccess communication Computational complexity direct-sequence code-division multiple access Maximum likelihood detection Power control Convergence Monte Carlo methods Detectors Bit error rate

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A power control scheme using turbo partial parallel interference cancellation for DS-CDMA wireless communications

A power control scheme using turbo partial parallel interfer...

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IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： Kuo-Ming Wu Chin-Liang Wang Department of Electrical Engineering National Tsing Hua University Hsinchu Taiwan

ISBN: (纸本)0780376323

A low-complexity power control scheme for direct-sequence code-division multiple access systems is presented. In the proposed structure, we exploit the interference cancellation capability of the turbo partial parallel interference cancellation (TPPIC) algorithm presented by Wu and Wang (see Proc. 2001 IEEE Global Telecommun. Conf (Globecom 2001), San Antonio, TX, Nov. 2001, p.244-248). A new method for parameter estimation is also presented and is integrated with the powerful TPPIC in power control algorithm design. Computer simulation results show that this new approach significantly outperforms the previous scheme using conventional parallel interference cancellation, where both involve the same order of complexity. As compared to the more complicated power control methods using minimum mean-squared error (MMSE) filtering, the proposed approach still provides better performance but involves much less complexity.

关键词： Power control Interference cancellation Multiaccess communication Wireless communication direct-sequence code-division multiple access Telecommunications Parameter estimation Algorithm design and analysis Computer simulation

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