Linear space-time transmitter and receiver processing and scheduling for the MIMO broadcast channel

We consider a MIMO broadcast channel where the transmitter and the receivers are equipped with multiple antennas. We propose a new scheme using linear processing at the transmitter and at the receivers to jointly diagonalize the channel so that two users can receive data simultaneously. It is also applicable when the users are equipped with different numbers of antennas, and it is able to take advantage of all the spatial degrees of freedom as long as the overall number of all receive antennas is greater than or equal to the number of transmit antennas. We show that the maximum throughput achievable with our scheme is larger than the maximum throughput achievable by transmitting to a single user at a time and by transmitting to several users simultaneously with receiver processing only. The proposed strategy achieves a large portion of the two-user sum-capacity when the base station has two transmit antennas. We provide an asymptotic analysis and simulation results to illustrate our analysis.