Capacity-maximizing transmitter processing for fading matrix channels

The performance potential of a wireless communications system employing antenna arrays is not fully utilized if equal energy allocation and uncorrelated symbols are used at all transmitters in the multichannel, cross-coupled system. Optimal, in the information-theoretic sense, transmitted signal covariance can be found by maximizing the end-to-end system capacity subject to an energy constraint. Performance evaluation of system outage capacity shows that optimal transmitter processing offers an SNR improvement potential up to several dB. The gains are most notable for systems with low SNR or many transmit antennas.