Symbol error rates of MPSK and MDPSK for optimum combining with multiple interferers in a Rayleigh fading channel

In this paper, the performance of M-ary signals for optimum combining with multiple co-channel interferers is analyzed in a flat Rayleigh fading channel. The closed-form expressions of average symbol error rates of M-ary phase shift keying and M-ary differential phase shift keying are derived by using the moment generating function-based approach and the orthogonal approximation which is employed to evaluate the eigenvalues of the covariance matrix of the received interference-plus-noise. This analysis is a convenient way of evaluating the performance of optimum combining and comparing it with that of maximal-ratio combining. In the cases of single and multiple interferer(s), the accuracy of the approximation is assessed through computer simulations.