Scheduling Approach for MIMO with Tomlinson-Harashima Precoding

We consider the downlink of a wireless network, where Tomlinson-Harashima precoding (THP) is applied as a MIMO spatial multiplexing method. THP facilitates a point-to-multipoint transmission strategy, in which a subset of mobile stations receives data packets over parallel subchannels formed by preceding. In this paper, we propose a low-complexity scheduling algorithm that determines the best subset of stations to maximize the system capacity. TH preceding is based on the QR factorization of the channel matrix H, and the proposed scheduling algorithm here makes use of incremental implementation for QR factorization with Gram-Schmidt algorithm. We show that significant reduction in complexity can be obtained over classical exhaustive search, while providing the same maximum capacity