Bounded CSI Error-Based Robust Beamforming Design for IOS-Assisted Multi-User MISO System

Reasonable robust beamforming design has been identified as a promising approach to enhance the adaptability, transmission efficiency and anti-interference capacity of the communication system. In this paper, we propose a beamforming design aimed at maximizing the sum-rate of communication in an intelligent omni-surface (IOS)-assisted multi-user multiple-input single-output (MISO) downlink communication system. Specifically, the presented scheme resolves the transmission rate optimization problem while considering constraints such as transmission power limitation at the base station (BS) and discrete phase shifts at the IOS. Additionally, we investigate S-Procedure to transform the produced semi-infinite objective function for addressing the non-convex problem due to the infinite inequality constraints. Then, we decompose the transformed problem into two subproblems to tackle the deep coupling between variables. Finally, a novel success convex approximation (SCA) algorithm is presented based on semi-definite programming (SDP) technology, branch and bound method to solve two subproblems iteratively until convergence. Simulation results demonstrate that our robust beamforming scheme can effectively mitigate the communication sum-rate degradation caused by channel state information (CSI) error and enhance the downlink transmission robustness of the IOS-assisted communication system.