Active Reconfigurable Intelligent Surface Aided Secure ISAC System

This paper investigates an active reconfigurable intelligent surface (RIS) aided integrated sensing and communication system, in which a multi-antenna base station, a single antenna communication user, eavesdropper (Eve) as well as a flying target are considered. In this system, the active RIS is deployed to assist the communication and also create a virtual line-of-sight link for target sensing. Due to broadcast nature of wireless channels, the confidential user's information can be leaked to the eavesdropper as well as the target when performing communication and sensing. To combat eavesdropping attack, we formulate a power minimization problem of base station subject to quality of service constraint at the user, maximum eavesdropping signal-to-interference ratio (SINR) constraint at Target, minimum SINR constraint of the echo signal, RIS amplification factor constraint as well as secrecy outage probability constraint at Eve given imperfect Eve's channel state information. An efficient alternating optimization (AO) combined with semi-definite relaxation algorithm and successive convex approximation is proposed to solve this problem. Simulation results show the performance of proposed algorithm achieve better performance than the benchmark schemes.