Covert Communication in Multi-User ISAC Systems: Joint Beamforming and Jamming Optimization

This paper investigates covert communication in multi-user integrated sensing and communication (ISAC) systems, where a base station (BS) detects target and secretly transmits confidential signals to multiple users under the surveillance of an adversarial warden (Willie), and a mobile friendly jammer is deployed to transmit jamming signals to enhance covertness. The closed-form expression of Willie's detection error probability (DEP) is derived as a metric of covertness performance, and the joint beamforming and jamming power optimization problem is formulated to balance sensing performance and average covert transmission rate. Considering both perfect and imperfect channel state information (CSI) scenarios, a two-step algorithm composed of Rayleigh quotient derivation and successive convex approximation (SCA) is proposed to solve the non-convex multi-variable problem. Numerical simulations validate the theoretical analysis, and demonstrate the benefits of a jammer to the covertness of the ISAC system compared with max ratio transmission (MRT) and zero-forcing (ZF) methods.