Direct Beamformer Estimation for Hybrid Architecture in mmWave Dynamic TDD System

Abstract

The problem of weighted sum-rate maximization for hybrid architecture in millimeter wave communications with dynamic time division duplexing is considered. We propose an over the air pilot- aided direct beamforming estimation technique for the considered problem, by exploiting the channel reciprocity. Proper selection of analog precoder/combiner not only suppresses large part of interference, but also ensures that less coordination is required for digital precoder/combiner design. We design analog precoder/combiner for each data stream in such a way that its signal strength is maximized; this strategy also minimizes large part of inter-stream interference that may arise due to the main lobe of analog beamformer. Then we design digital beamformer such that inter-stream interference is further mitigated, maximizing the overall weighted sum-rate of the network.