Multi-symbol detection of M-DPSK

The authors discuss optimal and suboptimal detection methods for improving the error performance when M-ary DPSK (differential phase shift keying) modulation is employed. All procedures use a block of N+1 measurements to produce N data decisions. The motivation is to lessen the energy penalty associated with classical DPSK detection and to approach the performance of fully-coherent detection, but without complicated feedback phase-tracking circuitry and the associated phase-acquisition time. The authors formulate optimal (block) detection under the assumption of unknown carrier phase. Performance analysis and simulation show significant improvement with increasing blocklength, but complexity increases exponentially in blocklength. Suboptimal methods are then proposed which have far less complexity, but retain the improvement over standard DPSK. The primary applications of the present work are in fast-acquisition TDMA (time-division multiple-access) systems with PSK modulation and in frequency-hopping systems using DPSK