Legitimate Eavesdropping in UAV-Based Relaying System

This letter studies the legitimate eavesdropping with one full-duplex monitor (E) in a suspicious relaying system, where one suspicious transmitter (S) communicates with one suspicious destination (D) with the help of one suspicious unmanned aerial vehicle-based relay (U). Under this setup, E aims to maximize its eavesdropping rate by overhearing the suspicious messages from S/U and optimizing the power of jamming U/D concurrently. However, given specific jamming environment, U could be adaptively deployed to maximize the communication rate of the suspicious system, which brings the fundamental challenge for E to figure out the exact jamming effect. Hence, generally successive convex approximation for determining the corresponding deployment of U and exhaust search over the jamming power is required to achieve the optimal solution. To decrease the high complexity of the optimal strategy, one novel heuristic scheme is further proposed, in which one sub-optimal jamming power is derived immediately. Simulations present the considerable gain of the proposed optimal and heuristic schemes compared to some intuitive schemes.