Maximum Likelihood-Based Space-Time Transmit Diversity Receiver Scheme for WCDMA

Multiuser data communication over time-dispersive channels leads to the appearance of inter-symbol interference (ISI) and multiple-access interference (MAI) which significantly limit the downlink capacity of a DS-CDMA system. In (G. E. Bottomley et al., 2000), a generalized RAKE (G-RAKE) receiver based on maximum likelihood (ML) approach has been proposed for interference suppression and multipath mitigation. On the other hand, transmit diversity is a promising technique to combat channel fading. In this paper, a ML-based space-time transmit diversity (STTD) receiver is proposed which is extension of G-RAKE for diversity reception. Analytic expressions and simulation results reveal that the proposed ML-STTD decoder considerably outperforms the standard STTD receiver for both fixed and Rayleigh fading channels.