Downlink transmit beamforming with selective feedback

We consider a novel scheme to facilitate downlink beamforming over fading channels. A new feedback scheme is proposed, the main features of which being significantly reduced feedback. An adaptive set-membership filtering solution to channel estimation is proposed at the base-station, which, by its very formulation, requires only sparse and selective feedback of information from the mobile. Further, information-theoretic downlink capacity analysis shows that such a beamformer is near optimal in terms of capacity.