Performance of Optimal Combining versus Maximal RatioCombining

In this work, for a CDMA communication, the per user carrier-to-interference ratio (CINR) enhancement in the Reverse Link (mobile to base station) is analyzed using different antenna array spatial combining algorithms: Optimal Combining (OC) Versus Maximal Ratio Combining (MRC) in a multi-rate (combined voice and data users) multi-antenna scenario. The ratio of the CINR for OC vs. MRC is directly analyzed, i.e. Z=CINROC/CINRMRC. Exact solutions are derived for the statistics of a per user CINROC/CINRMRC improvement, as a function of the high-level interference power to background noise, the gain ratio CINROC/CINRMRC is evaluated in a flat Rayleigh fading communications system with multiple interferers, when the number of interferences L is no less than the number of antenna elements M (L M). The gain ratio is derived providing a simple means to determine when OC will exhibit significant gains over MRC. simulations are done to find out the BER performance of optimum combining diversity in correlated Nakagami-m channels and compare with the BER performance of MRC and the influence of interference for MRC and OC are analyzed and discussed