Multiuser MIMO Downlink with Limited Feedback Using Transmit-Beam Matching

The multiuser multiple-input multiple-output (MIMO) broadcast channel uses multiple antennas at the transmitter to simultaneously deliver information to multiple users. Despite the theoretical capacity gains, the actual throughput of the system with limited feedback of channel state information suffers due to interspatial stream interference caused by quantization errors. This paper introduces a new method to mitigate the interference: transmit-beam matching. Using multiple receive antennas, transmit-beam matching minimizes the inter-spatial stream interference by each user´s effective channel to the transmit-beam. It is evaluated based on a recent MIMO broadcast channel technique with limited feedback, per-user unitary rate control (PU2RC) and shown to effectively mitigate the interference.