Improving differential detection of MDPSK by nonlinear noise prediction and sequence estimation

A new technique is proposed to improve the performance of di erential detection of MDPSK (M{ary di erential phase{shift keying) signi cantly, applying sequence estimation. In order to obtain an appropriate representation of the received signal, a nonlinear time{variant FIR or IIR prediction{error lter is used. For both lter structures the optimum coe cients are derived, assuming transmission over an additive white Gaussian noise (AWGN) channel. Delayed decision{feedback sequence estimation (DDFSE) is employed to estimate the transmitted symbol sequence. It is shown by simulations that even for decision{feedback equalization (DFE), which is a simple special case of DDFSE, a signi cant performance improvement of conventional di erential detection under AWGN conditions results. In contrast to other noncoherent low complexity receivers proposed in literature this receiver is very robust under at fading (Rayleigh and Ricean) conditions.