Open Access

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

EURASIP Journal on Wireless Communications and Networking20102009:839424

https://doi.org/10.1155/2009/839424

Received: 13 August 2009

Accepted: 25 December 2009

Published: 11 March 2010

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.

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Authors’ Affiliations

(1)
School of Information Technology and Engineering, University of Ottawa, Ottawa, Canada
(2)
Department of Electrical and Computer Engineering, Université du Quebec à Trois-Rivières, Trois-Rivières, Canada

Copyright

© C. D’Amours and A. O. Dahmane. 2009

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.