Multiple Error Performance of PSK Systems with Cochannel Interference and Noise

The multiple error performance of a phase-shift-keyed (PSK) communications system, when both cochannel interference (due possibly to other cochannel angle-modulated systems) and Gaussian noise additively perturb the transmitted signals, is considered. The results are fairly general: the main requirement is that the interference be circularly symmetric. All of our findings are also applicable to the case when only noise is present. The results indicate that one cannot approximate well the effect of interference on the performance of a PSK system by treating it as additional Gaussian noise. First, we derive the probability density function f
A
of the phase angle of a cosinusoid plus interference and Gaussian noise. We then obtain readily computable expressions (in terms of f
A
) for the probability of any number of consecutive errors in an
m
-phase system when either coherent or differential detection is utilized. For numerical results, the interference is assumed to be due to other cochannel angle-modulated communications systems, and the double error probability and conditional probability of error are given for 2- and 4-phase systems.