Low complexity user selection algorithms for multi-user MIMO systems

The combined Block Diagonalization and Geometric Mean Decomposition(BD-GMD) is a precoding scheme that is asymptotically optimal for(moderately) high Signal-to-Noise Ratio(SNR) in terms of both channel throughput and the Symbol Error Rate(SER) performance in downlink Multi-User Multiple-Input-Multiple-Output(MU-MIMO) systems.The number of simultaneously supportable users 1with BD-GMD is limited by the number of transmitting and receiving antennas.In a downlink MU-MIMO system with a large number of users,the basestation may select a subset of users to serve in order to maximize the total throughput.The brute-force search for the optimal user set,however,is computationally prohibitive.We propose a low complexity suboptimal user selection algorithm for downlink MU-MIMO systems with BD-GMD.We show that the proposed algorithm has linear complexity in the number of users and achieves around 95% of the total throughput of the complete search method in simulations.