Performance of binary NCFSK with dual-branch S+N selection combining in Rician and Nakagami-m fading

In traditional selection combining, the branch having the largest signal-to-noise ratio is employed for signal detection. However, many practical systems choose the branch with the largest signal-plus-noise (S + N) at the filter output. Recent work has studied the performance of noncoherent orthogonal frequency shift keying (NCFSK) with S + N selection combining in slow, flat Rayleigh fading channels. In this paper, we consider the performance of NCFSK with dual-branch S + N selection combining in slow, flat Rician and Nakagami-m fading channels. Two S + N receiver structures for NCFSK are examined and analytical expressions for the bit error rate (BER) performances of these receivers are obtained both for Rician and Nakagami-m fading channels. The channel fadings are assumed to be independent, but not necessarily identically distributed. It is shown that both S + N receiver structures considered outperform the traditional selection combiner and their performances are compared to the performances of equal gain and square low combiners.