Robust Secure Beamforming for IRS-Aided ISAC via D2D Jamming

A robust secure beamforming scheme for the IRS-aided ISAC with imperfect channel state information (CSI) is investigated in this paper, where a device-to-device (D2D) pair is utilized as a cooperative jammer to interfere with the eavesdropping target. Based on a statistical CSI error model, an optimization problem is formulated to minimize the transmit power by jointly optimizing the transmit beamforming and IRS phase shifts, subject to the constraints on the secrecy rate, the D2D communication rate, and the echo signal-to-noise ratio. To address this non-convex problem, we first utilize the Bernstein-type inequality to convert the robust probabilistic constraints into linear matrix inequality forms. Then, it is decomposed into two subproblems, and an alternating optimization algorithm based on the semi-definite relaxation is developed to solve them iteratively. Numerical results verify the effectiveness and robustness of the proposed scheme for secure ISAC.