Active RIS-Assisted Secure Communications Against Simultaneous Jamming and Eavesdropping

Due to the broadcasting characteristics of wireless channels, both jammers and eavesdroppers pose a serious threat to wireless communications. In this letter, we propose a scheme using active reconfigurable intelligent surface (RIS) to assist secure communication and prevent simultaneous jamming and eavesdropping. In this scheme, we assume that the jammer only interferes with the legitimate user, due to the potential cooperation between the eavesdropper and the jammer. To maximize the secrecy rate, a design problem of joint optimization of base station beamforming, and amplification factor and phase shifts matrices at the active RIS is proposed. Due to the non-convexity and coupling variables of this problem, we propose to use alternating optimization and semidefinite relaxation techniques to solve this optimization problem. Simulation results show that active RIS leads to a higher system secrecy rate compared to existing schemes in the presence of both jamming and eavesdropping.