Optimum combining systems in the presence of Rician facing: SINR and capacity analysis

This paper analyzes the performance of adaptive antenna arrays employing linear combining techniques designed to maximize the SINR. In the communications literature, these systems are referred to as optimum combining (OC) systems. We consider the practical case where the desired signal undergoes Rician fading, and is corrupted by Rayleigh-faded interfering signals and noise. We first propose new closed-form gamma approximations for the SINR distribution at the output of the OC combiner, which we show to be remarkably accurate. We then employ these approximations to derive new closed-form expressions for the ergodic capacity and simplified expressions for the high-SNR regime. These results reveal that the capacity improves monotonically with Rician K-factor.