A Balanced SLNR-based Tomlinson-Harashima Precoder for Downlink MU-MIMO Systems

The signal-to-leakage-and-noise ratio (SLNR) based precoding is a promising linear precoding scheme in multiuser (MU) downlink multiple-input-multiple-output (MIMO) communications. It gains its popularity recently as it nicely decouples the design problem and allows for a closed-form solution. In this paper, we extend the idea to nonlinear precoding and propose a closed-form SLNR-based Tomlinson-Harashima precoder. The proposed design is derived from a more general form of the simultaneous diagonalization conditions, allowing the the effective SINR among received streams of the same user to be more balanced. A new user-ordering algorithm is also developed for the proposed design based on the max-min SINR criterion to further improve the average error rate performance and the fairness among users. The performance advantages of the proposed design are quantified through extensive computer simulations.