Conditions for Multi-Antenna Selection to be Optimal Given Channel Amplitude Information

Transmitter designs based on partial channel state information (CSI) have become increasingly attractive in multi-antenna wireless communication systems. To capture partial CSI statistics at the transmitter, we rely on a channel amplitude information (CAI) model, based on which we aim for maximizing the random channel's average mutual information. Due to the high computational complexity required for such optimal transmissions, we resort to reduced complexity practical schemes and derive necessary and sufficient conditions for these alternatives to achieve maximal average mutual information