An Adaptive Hybrid Beamforming Scheme for Time-Varying Wideband Massive MIMO Channels

In this paper, adaptive hybrid beamforming methods are proposed for millimeter-wave range massive MIMO systems considering single carrier wideband transmission in uplink data mode. A statistical analog beamformer is adaptively constructed in slow-time, while the channel is time-varying and erroneously estimated. Proposed recursive filtering approach is shown to bring a remarkable robustness against estimation errors. Then, analytical modifications are applied on an analog beamformer design method and approximated expressions are obtained for channel covariance matrices that decouple angular spread and center angle of multipath components. Resultant adaptive construction methods use only the estimated power levels on angular patches and they are shown to be very efficient such that they reduce computational complexity significantly while the performance remains almost the same.