Joint Users' Secrecy Rate and Target's Sensing SNR Maximization for a Secure Cell-Free ISAC System

This letter considers a secure cell-free integrated sensing and communication (ISAC) system, where distributed access points collaboratively serve communication users (UEs) and sense the target in the presence of multiple eavesdroppers (EVs). We propose an efficient approach for the joint optimization of communication and sensing beamforming vectors, aiming to maximize both the secrecy rate (SR) of all UEs and the sensing signal-to-noise-ratio (SNR) of the target. To solve this non-convex problem, we propose an efficient iterative optimization algorithm based on quadratic programming. Our extensive simulation results demonstrate that the proposed algorithm achieves the best sensing SNR and SR performance compared to various benchmarks, even in challenging scenarios where EVs are positioned very close to UEs. Furthermore, the proposed algorithm achieves a superior SR at a lower computational complexity, when compared to the state-of-the-art solution.