A Multiuser Beamforming Scheme for Downlink Spatial Multiplexing MIMO

In this paper, a method based on max SINR criterion is proposed to mitigate the interuser interference for downlink multiuser spatial multiplexing MIMO systems. Unlike Zero Forcing (ZF) scheme in which the SNR is decreased when the interference is eliminated completely, max SINR method makes a compromise between noise and interuser interference. When the number of substreams is larger than the difference between the number of base station antennas and the sum of interference mobile station antennas, the ZF is infeasible. An existing Coordinated tx-rx Block Diagonalization(COOR BD) method uses a preprocessing at receiver to cancel the interuser interference. However it cannot obtain more receive diversity gain due to the preprocessing. Analysis and simulation show that the max SINR scheme has better performance than the ZF method. Moreover when the ZF is infeasible, the max SINR scheme can obtain more receive diversity gain than COOR BD in two users case.