Adaptive noncoherent DFE for MDPSK signals transmitted over ISI channels

In this paper, a novel noncoherent decision{feedback equalization (NDFE) scheme for M{ary di erential phase shift{keying (MDPSK) signals transmitted over intersymbol interference (ISI) channels is presented. A suboptimum version with lower computational complexity and a noncoherent linear equalizer (NLE) are derived from the original NDFE scheme. Furthermore, the relation of the novel NLE to a previously proposed NLE is investigated. In contrast to known NDFE schemes, the novel scheme can approach the performance of coherent minimum mean{squared error (MMSE) DFE. For adaptation of the feedforward (FF) and feedback (FB) lters, eÆcient novel modi ed least{mean{square (LMS) and recursive least{squares (RLS) algorithms are presented. Finally, it is shown that the proposed adaptive NDFE scheme is robust against frequency o set.