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

A new technique is proposed to improve the performance of differential dete ction (DD) of M-ary differential phase-shift keying (MDPSK) significantly, applying sequence estimation. In order to obtain an appropriate representat ion of the received signal, a nonlinear time-variant finite impulse respons e or infinite impulse response prediction-error filter is used. For both fi lter structures the optimum coefficients are derived, assuming transmission ol er an additive white Gaussian noise (AWGN) channel. Delayed decision-fe edback sequence estimation (DDFSE) is employed to estimate the transmitted symbol sequence. It is shown by simulations that even for decision-feedback equalization, which is a simple special case of DDFSE, a significant perfo rmance improvement of conventional DD under AWGN conditions results. In con trast to other noncoherent low-complexity receivers proposed in literature, this receiver is very robust under flat fading (Rayleigh and Ricean) condi tions.