Analysis of Ricean MIMO channels based on a virtual channel representation

The ergodic capacity of Ricean MIMO (multiple-input multiple-output) fading channels is investigated in this paper, based on a virtual (Fourier) channel representation. Coherent reception is assumed at the receiver. The Ricean statistics are due to a line-of-sight (LOS) path joining the transmitter and receiver. In the virtual domain, this LOS path corresponds to a single entry in the virtual channel matrix. The optimal input distribution of the correlated Ricean MIMO channel in the virtual domain has a diagonal covariance matrix structure, the same as in the Rayleigh fading MIMO case. Our method is used to get a tight lower bound and upper bound on the ergodic capacity. Further, the same analysis is used to obtain an approximate optimal input distribution analytically, in place of the usual Monte Carlo based numerical optimization methods.