Space-time transmit diversity in spatially correlated frequency-selective fading channels

Space-time block coding (STBC) creates transmit diversity in a communication link with multiple antennas at each end. To apply STBC in a multi-user environment such as wideband code division multiple access (WCDMA), space-time transmit diversity (STTD) has been proposed. Both STBC and STTD work best with independent fading over all spatial channels. However, correlated fading is a practically inevitable. This paper examines the performance of STTD in spatially correlated frequency-selective fading and introduces an optimal linear transformation of STBC code matrices based on channel correlation knowledge. We show that STTD performance is degraded in spatially correlated fading, but the proposed method recovers most of that performance degradation