Optimum receive antenna selection minimizing error probability

The optimum receive antenna selection combining rule that minimizes the bit error probability is presented. It is derived from a general relationship between the bit error probability and the log-likelihood ratio (LLR), and selects the receive antenna providing the largest LLR magnitude. The optimum selection combining rule is applied to single transmit (Tx) antenna and space-time block code (STBC) systems, with N_R receive (Rx) antennas, and the bit error probability is derived for BPSK signaling in Rayleigh flat fading channels. A suboptimum selection combining rule based on noncoherent envelope detection is also presented and analyzed. For STBC systems, the optimum generalized selection combining in which M(≤ N_R) Rx antennas providing the largest LLR magnitude are selected and combined is presented.