Prediction error based feedback for downlink transmit beamforming

This paper examines a downlink transmit beamforming scheme we proposed recently (see Nagaraj, S. and Huang, Y.F., Asilomar Conference on Signals, Systems and Computers, 2000). The idea is based on the use of an adaptive channel estimator at the base-station and requires the mobile selectively to feed back the value of the prediction error. This paper proposes a joint maximum-likelihood and set-membership filtering algorithm for adaptive channel estimation that provides robustness against incorrect feedback due to mobile decision errors. The amount of power and bandwidth saving possible with this scheme is quantified via an uplink capacity analysis.