MAXIMUM-LIKELIHOOD DIFFERENTIAL DETECTION OF UNCODED AND TRELLIS-CODED AMPLITUDE-PHASE MODULATION OVER AWGN AND FADING CHANNELS - METRICS AND PERFORMANCE

This paper derives metrics for maximum-likelihood differential detecti on of uncoded and trellis coded MPSK and QAM transmitted over Rayleigh and Rician fading channels. Receiver structures based on these metric s are proposed and their error probability performance analyzed and/or simulated. The results represent a generalization of the notion of mu ltiple symbol differential detection, previously introduced by the aut hors for MPSK over an AWGN, to the fading channel and other modulation s. For the coded cases, ideal interleaving/deinterleaving is assumed a nd furihermbre the presence or absence of channel state information. A n interesting side result is that for a constant envelope modulation t ransmitted over a fading channel with unknown but rapidly-varying phas e error (the other extreme to the slowly-varying phase error case norm ally assumed for differential detection), under certain practical assu mptions, it is shown that the optimum receiver is of the limiter-discr iminator type.