An upper bound on the ergodic mutual information in Rician fading MIMO channels

We consider Rician fading multiple-input multiple-output (MIMO) channels where the transmitted signal has complex Gaussian distribution, iid across the transmit antennas. Based on expected values of elementary symmetric functions of complex noncentral Wishart matrices, we derive an upper bound on the average (ergodic) mutual information for arbitrary SNR, arbitrary rank of the deterministic line-of-sight matrix, and arbitrary number of transmit/receive antennas. The Rayleigh fading signal component is allowed to have spatial correlation at one end of the link. Upper bounds for the cases of rank-1 line-of-sight component and pure Rayleigh fading emerge as special instances of the general result