Antenna selection for space-time communication with covariance feedback

We consider space-time communication for a cellular downlink in which the base station (BS) transmitter has multiple antennas, while the mobile receiver has one or two. Only a subset of the available antennas at the BS are used for transmission, thus reducing the number of RF chains and the complexity of the baseband signal processing. It is assumed that the BS does not know the instantaneous downlink channel realization, but has estimates of the covariance of the space-time channel: covariance information can be easily obtained in wideband systems by averaging uplink channel measurements over frequency. Based on the optimization of a lower bound for capacity, we are able to provide rules of thumb for antenna selection as a function of the physical channel characteristics and the number of receive antennas. This procedure is shown to be optimal or near-optimal (relative to exhaustive computation of the best antenna subset) at moderate SNR.