Secure Integrated Sensing and Communication for Conventional and ISAC-dedicated Receivers

This paper focuses on physical layer security issues in a multiple-user-multiple-input-multiple-output dual-functional radar-communication system (MU-MIMO-DFRC), which communicates with multiple downlink communication users (CUs) whilst detecting multiple targets, who are passive eavesdroppers that could intercept the confidential message. To establish secure integrated sensing and communication (ISAC) against numerous eavesdroppers, we use artificial noise (AN) for conventional receivers (Type-I). In the case of ISAC-dedicated receivers (Type-II), instead of AN, we employ sensing signals to confuse the eavesdroppers. We proposed secure ISAC beamforming designs for conventional and ISAC-dedicated receivers. For conventional receivers, we aim to minimise the summation of all eavesdroppers' SNR. The optimisation problem is a fractional programming problem solved iteratively. For ISAC-dedicated receivers, we optimise the radar beam pattern towards the eavesdroppers, followed by a least-square minimisation between the ISAC beam pattern and the obtained radar beam pattern. The proposed design for ISAC-dedicated receivers is computationally efficient since the optimal solution is determined non-iteratively. The simulation results demonstrate that our design is able to find a compromise between sensing targets and communicating with the CUs while ensuring information confidentiality for both types of receivers.