UAV-Assisted Covert Communication Systems: A Game Theory Approach

Covert wireless communication (CWC) is an emerging technology expected to revolutionize communication security via transmitting confidential messages to avoid being detected by wardens. Thanks to the rapid deployment of unmanned aerial vehicles (UAVs), UAV-aided CWC systems can be widely used in many complex communication scenarios, such as mountainous areas and cities with tall buildings. However, the critically low data rate of the CWC channel especially interfered with by malicious users, significantly challenges the design of CWC systems. In this paper, we propose a UAV-assisted CWC system with a Poisson interference field (PIF), where the UAV performs as a relaying node to forward messages and jams the communication channel between the transmitter and the warden. To maximize the covert rate, we propose a Bayesian Nash game model for the proposed CWC system, where the transmitter and the warden both adopt their optimal strategies. By using the stochastic geometry theory, we derive the probability density function (PDF) of aggregate interference in the PIF. Accordingly, the existence of a Bayesian Nash equilibrium (BNE) is proven with the derived expression for the outage probability of UAV-relayed wireless channel under Rayleigh fading. Numerical results show that the proposed CWC system can achieve the optimal covert rate when the transmitter and the warden adopt the optimal strategies and the proposed game model reaches the BNE.