Multi-RIS Aided Multicell Wireless Networks: Joint Beamforming Design Combined With Selection Strategy

Wireless communication technology is one of the key technologies to achieve the key requirements of high reliability, low latency and mass connectivity in the Internet of Things (IoT). To meet these requirements, we apply the reconfigurable intelligent surface (RIS) in the wireless IoT networks. Specifically, we study a scheme that combines the joint beamforming design with RIS selection strategy for multi-RIS aided multi-cell wireless networks. In the joint beamforming design, we propose the control mode of “each base station (BS) controls its local RISs” for non-free propagation scenarios in wireless IoT networks, such as smart city and intelligent transportation system. Specifically, we give the details of algorithm for this control mode, and prove that it can achieve the performance comparable to the “all BSs jointly control all RISs” mode in the non-free propagation scenario, with lower algorithm complexity and control signaling overhead. Moreover, based on the joint beamforming design, we further propose a genetic algorithm-based RIS selection strategy to maximize the sum-rate under the constraint of limited RIS deployment. Finally, simulation results show that the proposed RIS selection strategy is effective and outperforms the existing schemes.