Secure and Robust Beamforming Algorithm for RIS Assisted MISO Systems

To solve the problem of information transmission security caused by wireless channel openness and system transmission performance deterioration caused by channel estimation error, a Charnes-Cooper robust beamforming algorithm is proposed for Reconfigurable Intelligent Surface (RIS) assisted Multiple-Input Single -Output (MISO) systems with eavesdroppers. A bounded channel uncertainty model is established for the eavesdropper, and the base station beamforming and RIS phase shift are jointly optimized to maximize user secrecy rate based on the constraints of maximum transmit power and RIS phase shifts. To solve the non -convex problem, it is first converted to a convex optimization problem by variable substitution, Charnes-Cooper method and S-procedure method, and then the coupling variables are indirectly and alternately optimized to obtain robust beamforming matrix and RIS phase shifts. Simulation results show that the proposed RIS-based joint optimization algorithm has better user confidentiality and robustness.