Closed-Form Performance of MFSK Signals with Diversity Reception Over Non-Identical Fading Channels

This paper provides a comprehensive study on the error performance of noncoherent orthogonal M-ary frequency-shift-keying (FSK) signals with various diversity combining schemes over fading channels. The diversity branches are assumed to be independent and non-identically distributed (i.n.d) Rayleigh fading. Closed-form expressions for the symbol error probability with an arbitrary diversity order and any modulation level are obtained for optimal combining (OC), equal gain combining (EGC) and log-likelihood ratio based selection combining (SC-LLR). Our analytical results show that EGC performs closely to OC over slightly unbalanced channels, whereas for highly unbalanced channels SC-LLR performs more closely to OC than EGC.