Exact Bit Error Rate of MIMO MRC Systems with Cochannel Interference and Rayleigh Fading

In this paper, we present a new method for deriving exact expressions for the average bit error rate (BER) of multiple-input multiple-output (MIMO) wireless systems with transmit beamforming and maximal ratio combining (MRC) reception, known as MIMO MRC, in the presence of cochannel interference. It is assumed that both the desired user and interferers are subject to independent flat Rayleigh fading. The conventional method for deriving the average BER expressions of MIMO MRC systems relies on finding the probability density function of the output signal-to-interference-plus-noise ratio. The presented method, however, is based on using the decision variable at the output of the maximal ratio combiner conditioned only on the fading channel of the desired user. An exact closed-form expression is derived for the average BER of MIMO MRC systems with two receive antennas and multiple transmit antennas. The analytical result is verified by Monte Carlo simulations.