A Low-Complexity SDMA Grouping Strategy for the Downlink of Multi-User MIMO Systems

In this work, a sub-optimal space division multiple access (SDMA) grouping strategy is proposed for the downlink of multi-user MIMO systems. It uses a new spatial compatibility check metric to estimate the grouping efficiency without needing to compute MIMO filter weights, thus reducing the complexity of SDMA grouping. Moreover, an iterative variant of the block diagonalization for throughput maximization algorithm is proposed, which can be employed to select the number of streams allocated to each user as to increase the sum capacity of the SDMA group. The proposed SDMA strategy is compared through simulation with single-user transmission, random grouping, and exhaustive search, and it is shown to have a good performance-complexity trade-off