Multi-stage beamforming for interference coordination in massive MIMO networks

Recently we showed that the joint space division and multiplexing (JSDM) framework for massive MIMO can applied to hybrid beamforming for interference coordination between multiple base station sites. JSDM explicitly distinguishes between pre-beamforming based on long-term channel (covariance) statistics and precoding based on instantaneous channel state information. In this work provide we extend the JSDM framework to multiple base stations and demonstrate that already with a suboptimal solution using a limited set of predefined first-stage precoding vectors a huge portion of the gap between the uncoordinated and single-node case can be closed.