Improved nonlinear multiuser precoding using lattice reduction

Daofeng Xu, Yongming Huang, Luxi Yang

Abstract: Recent theoretical results show that multiuser techniques such as Spatial Division Multiple Access can significantly improve system capacity. In order to achieve this end, lots of precoding methods have been proposed, among which Vector Perturbation precoding has the best Symbol Error Rate performance but with the hugest complexity in searching for the optimal perturbation vector. In this paper, we propose a low complexity, near optimal multiuser precoding method by utilizing lattice reduction of the channel matrix. The perturbation vector is composed of an integer part and a non-integer part, which are designed to simultaneously improve power efficiency and minimize the mean squared error MSE. The integer perturbation vector is calculated implicitly with modulo operation, and the non-integer perturbation can be solved in closed form under MSE minimization criterion. Simulation results demonstrate the effectiveness of the proposed methods.