Scheduling for Multiuser MIMO Downlink with Linear Processing

Block diagonalization (BD) combined with coordinated transmitter-receiver processing and scheduling between users is a simple and straightforward linear method to utilize the available spatial degrees of freedom in downlink multi-user multiple-input multiple-output (MIMO) channel for increasing the system throughput. In this paper, an efficient scheduling algorithm is proposed to maximize the downlink spectral efficiency of the BD method for any number of users and antennas at both the transmitter and the receivers. The performance is compared to the spectral efficiency available with several other scheduling algorithms and to the sum-rate capacity. It is shown that the performance of the BD method with the proposed scheduling approaches the sum rate capacity at high signal-to-noise ratio (SNR) as the number of users increases. It is also noticed that due to the inherent noise amplification problem with linear BD method, the maximum spectral efficiency is often achieved by transmitting to less users/beams than the spatial dimensions available, especially, at low SNR region with a high number of transmit antennas and with a low number of users