Dual-Diversity Square-Law Combining with Deterministic Weights in Correlated Rayleigh Fading

When a multi-branch diversity receiver has information on the channel statistics instead of the instantaneous channel state information and noncoherent reception is employed, a deterministically weighted square-law combining scheme can be used to improve the error performance over conventional square-law combining when the average branch signal-to-noise ratios are not equal. We consider such a scheme for a dual-diversity system with orthogonal signaling in correlated Rayleigh fading. The square-law output of each branch is multiplied by a deterministic weight and the weighted outputs are additively combined. The weights are chosen so as to minimize the symbol error probability (SEP). The SEP in terms of these weights is derived in closed form, and from it a method for computing the weights is obtained. The merit of this scheme when compared with conventional square-law combining is demonstrated through numerical examples.