Performance of Maximal Ratio and Optimum Combining with Channel Estimation Errors and Multiple Interferers in Rayleigh Fading Channels

This paper analyzes the performance of maximal ratio combining (MRC) and compares it with the performance of optimum combining (OC) in the presence of channel estimation errors and multiple interferers in a flat Rayleigh fading environment. The probability density function (PDF) of the signal-to-interference-plus-noise ratio at the output of the maximal ratio combiner has been derived in prior work, assuming Gaussian channel estimation errors. We use that PDF to derive analytical expressions for a number of important performance measures such as the outage probability and the average bit error probability for different modulation formats in interference-limited systems. These expressions are used to show that the simpler MRC method can outperform the more complex OC receiver when the channel estimator performs poorly, and quantify the threshold of correlation between the true and estimated channels at which the cross-over occurs.