Optimal and reduced complexity receivers for MISO antenna systems

MISO antenna systems employing feedback of the downlink channel state are attractive for achieving diversity in the downlink of cellular systems. In this paper we consider a particular MISO transmit diversity scheme with rich feedback (TDRF), and derive the optimal receiver structure taking into account intersymbol interference, colored noise, and the self-interference from pilot signals used for downlink channel estimation. We then compare the bound on performance established by the optimal receiver with the performance of a low complexity alternative consisting of a fixed receive filter followed by a sampler. Our results show that the application of TDRF to the WCDMA downlink gives substantial gains compared to a single antenna system, even when the extremely simple sampler receiver is used at the mobile terminal.