LAUSR

This letter studies the proactive eavesdropping with one full-duplex monitor (E) in unmanned aerial vehicle (UAV)-enabled suspicious multiuser communications, which include downlink broadcasting (DB) and uplink multiple access (UMA). Under this setup, E aims to maximize its sum eavesdropping rate by overhearing the messages from the UAV and jamming the ground multiple suspicious users simultaneously (corresponding to DB), or vice versa (corresponding to UMA). However, as the jamming power of E varies, the suspicious UAV and users will adapt their deployment and power allocation patterns concurrently to maintain the benefits of the suspicious system, which will cause certain obstacles for E to grasp its accurate jamming effect. To tackle these challenges, we first fix the jamming behavior of E and accordingly figure out the adaptiveness of the suspicious system, armed with which we further exploit the step characteristic of the eavesdropping rate to determine the optimal (sub-optimal) jamming power of E, and the complexity involved only increases linearly with the number of suspicious users and thus avoiding the tedious exhaustive search. Simulations verify the effectiveness of the proposed schemes compared to conventional benchmarks.