On Differential Detection of M-ary DPSK with Intersymbol Interference and Noise Correlation

In this paper we study differential detection of Mary differential phase-shift-keyed (DPSK) signals with intersymbol interference and noise correlation. With these impairments there can be a wide variation in the error rate of the individual symbols, with this variation increasing with M. However, by adding a phase shift offset and adjusting the decision boundaries in the detector, this variation can be reduced and the average symbol error rate can be decreased. For example, for quaternary DPSK with a signal to adjacent (from the previous and next Paper approved by the Editor for Data Communications and Modulation of the IEEE Communications Society. Manuscript received July 30, 1985; revised August 8. 1986. This paper was presented at the IEEE International Conference on Communications, Amsterdam, The Netherlands, May 1984. The author is with AT&T Bell Laboratories, Holmdel, NJ 07733. IEEE Log Number 861 1693. symbols) intersymbol interference power ratio of 17 dB, these methods can reduce the variation in symbol error rates by more than two orders of magnitude and decrease the required signal-to-thermal noise ratio for a symbol error rate by more than 2 dB.