BER Performance of MIMO-SM with Zero-Forcing in Spatially Correlated Ricean Fading

The probability of bit error of multiple-input multiple-output spatial multiplexing (MIMO-SM) systems employing linear zero-forcing (ZF) receivers is addressed. In this paper, we first present a near exact approximation for the average bit error rate (BER) of each substream with quaternary phase-shift keying (QPSK) in spatially correlated Ricean distributed channels. Then a closed-form expression for the optimal transmit correlation coefficient of two-input two-output spatial multiplexing (TITO-SM) systems is derived. Extensive simulations are presented to validate the accuracy of the analytical results.