Enhancing User-Centric mmWave Communication with Cooperative IRSs: Joint User Association and Beamforming

In order to fully explore the potential of intelligent reflecting surfaces (IRSs) in millimeter-wave (mmWave) communication systems and maximize system sum-rate performance within a user-centric framework, this paper investigates the joint optimization problem of user multiple association, transmit beamforming, and cooperative IRS passive beamforming. Meanwhile, the impact of IRS location on user association is also studied. Due to the deep coupling of multiple variables, the modeled problem is a complex non-convex optimization problem. To address it, an efficient alternating iterative optimization algorithm based on the Lagrangian dual decomposition and fractional programming techniques is proposed. Simulation results show that compared with traditional methods, the proposed algorithm significantly improves the system sum rate, validating its effectiveness.