Exact error probability for MMSE combining and comparison with maximal ratio combining for digital radio with cochannel interference

The exact performance analysis of MMSE (minimum-mean-square-error) combining for space diversity reception is studied in the presence of a single and multiple cochannel interference (CCI) sources, and compared to maximum-ratio combining (MRC). This paper considers digital cellular mobile radio systems with quadrature amplitude modulation (QAM) transmission and two diversity antennas in flat and quasi-static fading channels. Our analysis accounts for pulse waveform and modulation of the desired signal, as well as cochannel interference (CCI). The phase and symbol timing offsets between the desired signal and CCI, which can result in ISI caused by CCI, are taken into account. The desired signal channel is assumed Rayleigh or nonfading, as well as the CCI sources. The error probability for each fading channel is estimated fast and accurately by using Gauss quadrature rules (GQR) which can approximate the probability density function (pdf) of the ISI-like CCI in each fading channel.