Outage performance of cooperative small-cell systems under Rician fading channels

We consider a general class of Rician fading multiple-input multiple-output (MIMO) channels, modeled by a random, non-centered channel matrix with a variance profile, i.e., the independent elements of the matrix are allowed to have each a different mean and variance. This channel model is motivated by the recent interest in cooperative small-cell systems where several densely deployed base stations (BSs) cooperatively serve multiple user terminals (UTs). We study the fluctuations of the mutual information of this channel under the form of a central limit theorem (CLT) and provide an explicit expression of the asymptotic variance. The result can be used to compute an approximation of the outage probability of such channels. Although the derived expressions are only tight in the large system limit, we show by simulations that they provide very accurate approximations for realistic system dimensions.