Optimum linear diversity receivers in digital cellular radio

The paper analyzes and quantifies the performance of a space diversity combining receiver operating in a digital cellular radio environment with quaternary phase shift keying (QPSK), frequency-selective Rayleigh multipath fading, and co-channel interference (CCI). The receiver has an infinite length filter in each branch of the diversity combiner, and the filters are jointly optimized according to the minimum mean-square error (MMSE) criterion. The link bit-error-rate (BER) is accurately estimated using Metzger´s algorithm (Metzger, 1987) which approximates the probability density function of the combined intersymbol interference (ISI) and CCI. The authors present numerical performance results showing the influence of the diversity order, the number of dominant co-channel interferers, the multipath channel´s delay spectrum, and the root-mean square delay spread. The results show that, under certain conditions, the optimum linear receiver can almost completely eliminate all ISI and dominant CCI while providing near-optimum noise filtering