New decoder for space-time block coded multiuser system over flat and time-selective fading channels

The conventional zero forcing (ZF) and minimum mean squared error (MMSE) decoders are constructed based on the assumption that the channels are flat fading (FF) and quasi-static fading (QSF). The two decoders exhibit intersymbol interference (ISI) once the channels are time-selective fading (TSF) when decoding one user´s signals. We propose a new decoder design scheme applicable to the existing transceiver structure for a space-time block coded (STBC) multiuser (MU) communication system over FF and TSF channels. We analyze the impact of channel time variations on the two known ZF and MMSE decoders; then, the analytical bit error rate (BER) expressions of these decoders are presented. Simulation results indicate significant performance gains of our new decoder compared with the conventional ZF and MMSE decoders, especially at high SNR for various values of α.