Optimum selection diversity for BPSK signals in Rayleigh fading channels

We propose a new selection diversity scheme that selects the branch providing the largest magnitude of the log-likelihood ratio (LLR). The LLR for BPSK signals in fading channels is found to be proportional to the product of the fading amplitude and the matched filter output. The proposed selection diversity scheme is shown to minimize the bit error rate (BER), and outperform existing selection diversity schemes. It is shown that the proposed scheme provides the same BER provided by the maximal ratio combining (MRC) scheme for a dual diversity system, and is only 0.3 dB inferior to the MRC when the number of branches is four, in Rayleigh fading channels.