UAV Covert Communications in Interweave Cognitive Radio Network

The security issues of the secondary network in the interweave cognitive radio network (CRN) enabled by covert communication techniques are limited by the fixed position of the secondary transmitter and the flexible deployment of Wardens. In this article, we consider a interweave aerial CRN covert communication system, where the mobility of the unmanned aerial vehicle (UAV) could improve the security of CRN. A cooperative jamming scheme is also considered by the full-duplex mode of the secondary receiver (SR) to disturb the surveillance of Warden. We deduce the close-form expression of Warden’s minimal detection error probability under the uncertainty of the channel gain and noise variance. The covert rate of the secondary network is maximized by joint optimization of the transmit power and the location of UAV, the sensing time ratio, and the jamming power of SR. To solve the complex non-convex problem, an iterative algorithm based on successive convex approximation, the bisection search, and block coordinate descent techniques is proposed. Furthermore, the impact of each optimization variable on the covert rate is analyzed. Simulation results reveal that the covert rate of the proposed algorithm outperforms the other schemes in single-Warden and multi-Warden scenarios. Moreover, compared to the fixed position base station, the UAV could significantly improve the CRN covert communication in the single-Warden and multi-Warden scenarios.