Performance model for MRC receivers with user scheduling and adaptive modulation and coding in Rayleigh fading correlated channels

This paper presents a performance model of a wireless network with one-antenna transmitter scheduling information towards a set of terminals in a time-division fashion. Each terminal is enabled with a multiple-antenna maximum ratio combining (MRC) receiver. The objective of this model is to evaluate the performance of adaptive modulation and coding (AMC) in Rayleigh fading channels under two assumptions: 1) correlation between antennas, and 2) user scheduling based on maximum channel gain. The model is useful for cross-layer design purposes, as it provides a relatively low-complex representation of the physical-layer. Closed-form expressions are here derived of correct packet reception probabilities for different modulation and coding schemes (MCSs) with different values of block error rate (BLER) and spectral efficiency. Analytic expressions are derived with the help of the theory of order statistics, which allows for the study of the statistics of channel-aware scheduling. The results indicate that correlation does not always reduce performance. At low signal-to-noise ratio (SNR), correlation can improve performance rather than reducing it. By contrast, at high SNR, correlation is shown to always reduce the performance of the receiver. This low-SNR behavior is less evident as the number of antennas increases and more evident when the number of users included in the scheduling process increases.