Performance analysis of diversity reception for M-QAM with cochannel interference and Rayleigh fading

This paper analyzes the performance of optimal and maximum-ratio (MRC) diversity combining schemes in the presence of ISI due to cochannel interference (CCI) in flat fading environments. For cellular mobile radio systems, if the effect of fading is non-frequency-selective, no ISI exists in the desired signal with the use of the band-limited shaping filter. However, even in flat fading environments, ISI can be generated by cochannel interferers due to the random symbol timing and phase offsets between the desired signal and the cochannel interferers. With these two random-valued offsets, an optimal diversity combining scheme is derived. Several fading conditions experienced by desired and interfering signals are considered. A Gaussian interference model is also considered for a comparison. The accurate error rate is obtained by using the moment method for each time-varying channel in Monte-Carlo simulation.