Secure Integrated Sensing and Communication Systems Assisted by Active RIS

In this paper, we investigate secure transmission in active reconfigurable intelligent surface (RIS)-assisted integrated sensing and communication (ISAC) systems. The dual-function base station communicates with the legitimate user and detects the sensing target simultaneously via active RIS, while the communication signal is intercepted by a potential eavesdropper (Eve). To achieve secure transmission, a novel successive interference cancellation scheme is proposed, where the sensing signal can disrupt the potential eavesdropping while keeping the legitimate user link intact. Then, the secure rate maximization problem is proposed, where the active beamforming of the RIS, the legitimate user's transmit beamforming, the Eve's transmit beamforming, and the radar receive beamforming are jointly optimized. However, the secure rate expression is non-convex, an iteration optimization algorithm based on majorization-minimization method and semi-definite programming are proposed to decompose the original problem into three sub-problems. Simulation results illustrate that the secrecy performance of the proposed scheme outperforms the passive RIS-assisted ISAC systems and the traditional cellular networks aided by active RIS.