Optimum combining with correlated interference

We analyze the problem of optimum combining with a single spatially correlated interferer in white Gaussian noise and Rayleigh fading by focussing on the conditional characteristic function (c.f.) of the combiner output signal-to-interference-plus-noise ratio, given the interference propagation vector. Unconditioning of this c.f. using the interference statistics, along with a finite-range integration, results in the symbol error probability (SEP) integral, which is a common integral factor to most digital-modulation schemes. We obtain an exact expression, partly in closed form, for the SEP integral. For the case of large values of average signal-to-noise ratio and signal-to-interference ratio per antenna element, we obtain closed-form asymptotic formulas for the SEP integral. Using the SEP integral, we can easily evaluate the symbol error performance of various modulation schemes. The correctness of our analytical results are verified by some numerical examples.