ISAC-Enabled Covert Communication Leveraging a Dual-Functional Uncrewed Aerial Vehicle

Abstract

Covert communication has attracted increasing attention, especially in applications requiring a high level of security, such as military, emergency services, and privacy protection. In existing studies, most friendly-jamming-based schemes rely on fixed or ground jammers, which may result in a significant degradation of covertness in non-line-of-sight (NLoS) environments. Moreover, the mobile eavesdropper poses a great challenge to achieving covert communication. To overcome these drawbacks, we propose a covert communication framework enabled by integrated sensing and communication (ISAC), where a dual-functional uncrewed aerial vehicle (DF-UAV) first tracks the motion states of an eavesdropper using the Unscented Kalman Filter (UKF) and then actively jams its detection capability, thereby enhancing the covertness of data transmission. Within this framework, we consider a multi-user downlink covert communication system aided by the DF-UAV, and the minimum detection error probability (DEP) of the mobile eavesdropper is derived to evaluate covert performance under compounded fading channels that incorporate both Rician and Nakagami-m effects. By jointly considering the system’s sensing, transmission, and covertness requirements, we formulate an optimization problem over the base station (BS) transmit beamforming, the DF-UAV jamming power, and the DF-UAV trajectory, with the goal of maximizing the eavesdroppers’ minimum DEP. To solve this non-convex problem, we develop an alternating optimization (AO) approach that decomposes it into three subproblems. Each subproblem is reformulated as a convex problem, and the algorithm solves them alternately until convergence. Simulation results demonstrate that the proposed scheme outperforms the benchmarks. Specifically, compared with the baseline schemes, the UKF reduces the estimation error by 5.26% to 36.40% in average. Moreover, the proposed DF-UAV model achieves an average covertness improvement of 22.94% over the fixed-jammer model. The simulation results further reveal the trade-off between transmission performance and covertness as well as the impact of the BS antenna array size on both metrics.