Adaptive Noncoherent Linear Minimum ISI Equalization for MDAPSK Signals

In this paper, a novel noncoherent linear equalization scheme is introduced and analyzed. The proposed scheme is not only applicable for M-ary differential phase-shift keying (MDPSK) but also for M-ary differential amplitude/phase-shift keying (MDAPSK) and minimizes the variance of intersymbol interference (ISI) in the equalizer output signal. The optimum equalizer coefficients may be calculated directly from an eigenvalue problem. For an efficient recursive adaptation of the equalizer coecients, a modified least-mean-square (LMS) algorithm is proposed. Simulations confirm the good performance of the considered noncoherent equalization scheme and its robustness against frequency offset