Secure Transmission via Hybrid Active-Passive RIS Against Eavesdropping and Jamming

Due to the inherent broadcast nature of wireless channels, wireless communication systems are vulnerable to both eavesdropping and jamming attacks. In this letter, a secure communication system aided by the hybrid active-passive reconfigurable intelligent surface (RIS) is considered in the presence of eavesdroppers and jammers, aiming at maximizing the secrecy rate (SR) by jointly optimizing the transmit beamformer at the base station (BS) and the coefficients of the hybrid RIS. To address this non-convex problem, we divide it into two subproblems and adopt the alternate optimization (AO) method to solve them iteratively. Specifically, the subproblem of transmit beamformer optimization is solved by using the semi-definite relaxation (SDR) method. Then, the suboptimal RIS coefficients are obtained through the customized particle swarm optimization (PSO) algorithm. Extensive numerical results demonstrate the effectiveness and superiority of the proposed algorithm compared to the benchmark schemes in terms of improving the SR.