Joint Beamforming Design for Active RIS Aided Integrated Sensing and Communication System

This paper investigates the secure communication of an active RIS (Reconfigurable Intelligent Surfaces)-assisted Integrated Sensing and Communication (ISAC) system. The base station aims to transmit messages to legitimate users with the help of an active RIS while detecting a trusted target in the presence of an eavesdropper. A joint optimization of the base station beamforming and the active RIS beamforming is formulated to maximize the sum secrecy rate for multiple users. To solve the nonconvex optimization problem, techniques such as Successive Convex Approximation, Semi-Definite Relaxation, and Alternating Optimization are employed to transform the original problem into a convex one. Simulation results show that the system can provide effective target detection while ensuring a predefined signal-to-interference-plus-noise ratio (SINR) threshold and secure communication. This demonstrates the advantages of deploying an active RIS in an ISAC system, as well as the superiority of an active RIS in achieving these objectives compared to passive RIS in ISAC.