Frugal channel tracking for transmit beamforming

Channel state feedback is a serious burden for transmit beamforming systems with many antennas in FDD mode. Instead of estimating the channel at the receiver and feeding back quantized beamformer information, a different approach that exploits the spatio-temporal correlation of the channel is proposed. The transmitter periodically sends a beamformed pilot signal, while the receiver feeds back the quantized innovation derived from either a Kalman filtering or a MAP tracking loop. Simulations show that close to optimum performance can be attained with only 2 bits per channel dwell, clearing a hurdle for transmit beamforming with many antennas in FDD mode.