Outage performance analysis of ZF receiver for rate-adaptive MIMO systems with N antennas in the presence of imperfect CSI

In this paper, we analyze the effects of imperfect channel state information (CSI) on the outage performance of linear zero-forcing (ZF) receiver in time-varying multiple-input multiple-output (MIMO) fading channels. Accurate CSI is an essential condition to improve the overall performance of the rate-adaptive MIMO system. However, acquiring perfect CSI at transceivers is impossible due to feedback delay and channel estimation error. To investigate imperfect CSI environments, therefore, the outage probability is approximated by deriving the probability density function of the output signal-to-noise ratio (SNR) of the ZF receiver, based on temporal MIMO channel correlation. Since the exact distribution of the ZF-output SNR is yet unknown, we apply a Gaussian approximation to obtain mathematical expressions for the outage probability with the assumption of a square MIMO channel. Simulation results shows that our approximation is close to the actual outage probability.