Performance Comparison of Delay Transmit Diversity and Frequency-Domain Space-Time Coded Transmit Diversity for Orthogonal Multicode DS-CDMA Signal Reception Using Frequency-Domain Equalization

Takeshi ITAGAKI  Kazuaki TAKEDA  Fumiyuki ADACHI  

IEICE TRANSACTIONS on Communications   Vol.E87-B   No.9   pp.2719-2728
Publication Date: 2004/09/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
multicode DS-CDMA,  frequency-domain equalization,  MMSE,  transmit diversity,  

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In a severe frequency-selective fading channel, the bit error rate (BER) performance of orthogonal multicode DS-CDMA is severely degraded since the orthogonality property of spreading codes is partially lost. The frequency-selectivity of a fading channel can be exploited by using frequency-domain equalization to improve the BER performance. Further performance improvement can be obtained by using transmit diversity. In this paper, joint transmit diversity and frequency-domain equalization is presented for the reception of orthogonal multicode DS-CDMA signals in a frequency-selective fading channel. As for transmit diversity, delay transmit diversity (DTD) and frequency-domain space-time transmit diversity (STTD) are considered. The achievable BER performance of multicode DS-CDMA in a frequency-selective Rayleigh fading channel is evaluated by computer simulation. It is shown that the frequency-domain STTD significantly improves the BER performance irrespective of the degree of the channel frequency-selectivity while DTD is useful only for a weak frequency-selective channel.