Covert Communication in Dual-UAV-aided ISAC Systems with Collusive Wardens

Integrated sensing and communication (ISAC) enables the efficient utilization of limited spectrum resources to simultaneously support wireless communication and sensing, making it a promising technology for future wireless networks. Uncrewed aerial vehicle (UAV)-enabled ISAC further exploits UAV mobility and favourable air-to-ground line-of-sight links to achieve flexible coverage and enhanced communication and sensing performance. This work investigates the covert performance of a dual-UAV-aided ISAC system in the presence of multiple collusive wardens. In the considered system, an aerial base station UAV conducts covert communications with terrestrial legitimate users while simultaneously sensing the warden region. A friendly UAV transmits auxiliary sensing/interference signals to facilitate cooperative sensing and regulate the wardens’ observation quality. Considering the optimal detection thresholds of the wardens, we maximize the average covert rate by jointly optimizing user scheduling, transmit beamforming, and UAV trajectories, subject to constraints on maximum flight speed, transmit power, propulsion energy consumption, joint sensing requirements, and covertness. To address the non-convexity arising from the strong coupling among multiple variables, the original problem is decomposed into three subproblems. Successive convex approximation is then employed to transform the non-convex subproblems into approximate convex forms, which are solved sequentially using the block coordinate descent technique. Numerical simulation results validate the effectiveness of the proposed algorithm.