Cognitive Jamming-Aided UAV Multi-User Covert Communication

Introducing friendly jammer to unmanned aerial vehicle (UAV) covert communication could further enhance the covert performance. However, due to the additional communication overhead required for information synchronization (IS) among cooperating parties, the security risk is further elevated. It is noteworthy that cognitive jamming (CJ) could sense the cooperating node signals without IS links. Therefore, in this paper, we propose the cooperative UAVs covert communication scheme assisted by the CJ that maximize the minimum average covert rate (MACR). Specifically, the UAV (Alice) tries to transmit its private message to legitimate users under the surveillance of the Wardens. Since the Warden is in passive surveillance, the practical location uncertainty of the Warden is considered, and we further analyze the worst-case situation that derives the minimal detection error probability of the Wardens. Moreover, we maximize the MACR by alternatively optimizing the sense time ratio and trajectory of CJ, the transmit power and trajectory of the Alice. To expedite algorithmic convergence, we further introduce a principled initialization scheme. The simulation results reveal that the covert performance of the proposed algorithm outperforms the other schemes, especially, in the multi-warden scenario. Furthermore, compared with the full-time jammer and probabilistic jammer, the CJ can not only achieve a higher covert rate with less average jamming power, but also require no information synchronization link with Alice based on spectrum sensing, which promises considerable application prospects in real-world systems.