Shannon capacity regions for orthogonally multiplexed MIMO broadcast channels with informed transmitters

This paper considers the Shannon capacity region of a space and time dispersive multiple-input multiple-output (MIMO) broadcast channel with multi-dimensional space-time modulation. We assume no inter-user cooperation and consider a non-fading environment with orthogonally multiplexed users. With the single user capacity being achieved by water-filling power allocation and eigen-beamforming transmission, we investigate the capacity region when each user channel is known at both the transmitter and receiver. Furthermore, the high and low SNR asymptotic behaviour of the capacity region is studied along with the transmit power allocation that maximizes the sum capacity. Numerical results show that the capacity region expands with the number of signal propagation paths, and also with the number of antennas. The effect of space-time modulation is also pointed out.