Performance of optimum combining with imperfect channel estimates

This paper studies the impact of imperfect estimation of the desired user´s channel as well as the interfering users´ channels on the performance of optimum combining for space diversity reception with multiple interferers in a flat Rayleigh fading environment. The probability density function (PDF) of the signal-to-interference ratio (SIR) at the output of the optimum combiner is derived in prior work, assuming Gaussian channel estimation errors. We utilize this PDF expression to derive analytical expressions for some important measures of performance such as the moments of SIR, the outage probability and the average bit error probability for binary differential phase-shift keying and non-coherent frequency-shift keying modulations. These expressions are used to evaluate the performance of the optimum combiner in the presence of channel estimation errors, and are convenient substitutes for time-consuming simulations. The analytical results are verified by Monte Carlo simulations