Symbol error probability of non-coherent M-ary frequency shift keying with postdetection selection and switched combining over Hoyt fading channel

For mitigating the deleterious effects caused by time-varying multipath fading, most of the modern digital wireless systems employ some sort of diversity combining. Combining of the different diversity branches, however, may be performed either before demodulation (predetection combining), or after it (postdetection combining). It has been shown earlier that postdetection schemes outperform their predetection counterparts for Rayleigh and less-severe-than Rayleigh (e. g. Rician)-fading channels. In this study, the authors consider Hoyt fading that characterises wireless environments experiencing more-severe-than Rayleigh fading, and compare error performance of postdetection combining with the results available for predetection combining. In particular, two of the combining variants namely selection combining and switched combining are investigated, and symbol error probability of a non-coherent M-ary frequency shift keying receiver is derived for independent but not necessarily identical diversity branches. The comparison reveals that postdetection schemes perform better than predetection combiners when the average branch signal-to-noise ratio (SNR) exceeds some crossover SNR.