A Systematic Approach to Carrier Recovery and Detection of Digitally Phase Modulated Signals on Fading Channels

Abstract

Carrier phase synchronization is a major problem for coherent data communication over frequency-nonselective fading channels due to the rapid phase fluctuations on these channels. This paper examines the problem of optimal carrier recovery and detection in the following way. First, the optimal receiver is derived for digitally phase modulated signals when transmitted over a frequency-nonselective fading channel with memory. The memory results from the fact that usually the coherence time of the channel is larger than the symbol period. Symbols adjacent in time cannot be detected independently and therefore the wellknown quadratic receiver is not optimal in this case. The MAP detector derived in this paper explicitly exploits the channel memory for carrier recovery. The derivation shows that the optimal carrier recovery is, under certain conditions, a Kalman filter. Some attractive properties of this carrier recovery unit (one of them is the absence of “hangup”) are discussed. Then the error rate of several digital modulation schemes is calculated taking the performance of the filter into account. The differences in susceptibility of the modulation schemes to carrier phase jitter are specified. © 1989 IEEE