Adaptive phase diversity for MDPSK reception

Adaptive phase diversity reception that uses only differentially detected phase information is proposed for the differential phase detection (DPD) of Rayleigh faded M-ary differentially encoded phase shift keying (MDPSK) signals. An M-state Viterbi algorithm (VA) is used both for MDPSK phase detection and adaptive estimation of the phase error variance of each diversity branch. The phase error variance is estimated along the surviving path in the trellis, where each state in the trellis represents one MDPSK phase, and its inverse is used as the diversity combining weight. Simple yet efficient MDPSK phase detection based on a decision feedback algorithm (DFA) is also presented. Since there is no need to measure the received instantaneous power for diversity combining, the proposed diversity reception scheme is considered to be very practical. The average bit error rate (BER) performance in the presence of additive white Gaussian noise (AWGN), Doppler spread, multipath delay spread and cochannel interference (CCI) is evaluated by computer simulations for 4DPSK signal transmission in Rayleigh fading channels