Abstract
This paper studies the fluctuations of the post-processing SNR at the output of the linear MMSE receiver in (receive) correlated multiple input multiple output (MIMO) systems. Although it is known that asymptotically, the SNR behaves like a Gaussian random variable, this approximation may yield to inaccurate estimates for small dimension. In order to circumvent this, we use Gamma and Generalized Gamma distributions to approximate the probability distribution of the SINR. The first three asymptotic moments of the SNR are computed and are used to adjust Gamma and Generalized Gamma distributions and to accurately approximate the Bit Error Rate (BER) and its outage probability. We provide simulations which strongly support the Gamma approximation, even for a small number of emitting/receive antennas.