Abstract: In a reconfigurable intelligent surface (RIS) assisted secure communication system, to improve the secrecy perfor-mance of the system and overcome the hardware impairments caused by the system transceiver, a design method for optimizing the secrecy performance of RIS assisted secure communication is proposed. Considering a multiple-input single-output scenario with multiple eavesdroppers, the secure communication secrecy rate maximization problem is established by jointly optimizing the base station transmit beamforming and RIS phase shift beamforming under the maximum transmit power of the base station and RIS phase shift unit-mode constraints. For the nonconvexity and coupling of this optimization problem, an efficient algorithm based on alternating optimization and semidefinite re-laxation is proposed to transform the original nonconvex optimization problem into two convex optimization sub-problems and iteratively solve them to obtain the suboptimal solution of this optimization problem. Simulation results show that the proposed scheme in this paper can obtain higher secrecy rate compared with the conventional secure communication beamforming scheme.

Key words: reconfigurable intelligent surface, beamforming, secure communication, hardware impairments