A hybrid mode user-location-aware network MIMO with limited feedback for cellular downlink

MIMO downlink with base station coordination in a cellular network is considered. In centralized coordinated transmission from a cluster of base stations, the channel state information (CSI) of users needs to be sent to a central processor for precoding and resource allocation. Real time CSI feedback from the users to their home base station and from the base stations to the central processor is a serious challenge from a practical point of view. A hybrid mode transmission scheme with reduced feedback requirement exploiting user location information and cell sectorization is proposed, in which some users are served using single-cell multiuser MIMO (MU-MIMO) approach and some using the network MIMO approach. Using a virtual MIMO downlink channel model the feedback requirement, complexity of user scheduling and precoding/power allocation with most multiuser MIMO precoding techniques is substantially reduced compared to the corresponding case using full CSI. Dirty paper coding (DPC) and zero forcing beamforming (ZFBF) precoding techniques are used to demonstrate the performance of the hybrid mode network MIMO technique.