Intelligent Reflecting Surface-Aided MU-MISO Communication Systems with Constructive Interference Precoding.

This paper studies precoding optimization for intelligent reflecting surface (IRS)-assisted multi-user multiple-input single-output (MU-MISO) communication systems. By introducing the concept of constructive interference (CI), multi-user interference is converted into useful signal power. We aim to jointly design the precoding matrix of the base station and the phase shift matrix of the IRS to maximize the minimum signal-to-interference-plus-noise ratio of the user. Due to the non-convexity of constraints, a two-stage algorithm is proposed. Specifically, the phase shift of the IRS is optimized in the first stage to maximize the weighted effective channel gain, and the semi-definite relaxation algorithm is employed to solve the constant envelope constraint of the IRS phase shifter. Simulation results show that employing constructive interference precoding can significantly improve the performance of the IRS-assisted MU-MISO system.