Proactive eavesdropping in UAV-aided mobile relay systems.

This paper studies a new wireless surveillance scenario, where a legitimate monitor attempts to eavesdrop on the dubious messages forwarded by an unmanned aerial vehicle (UAV)-aided suspicious relay. Specifically, we consider two relaying protocols commonly used by the UAV-aided relay, namely, amplify-and-forward (AF) and decode-and-forward (DF). For each relaying protocol, we maximize the average effective eavesdropping rate by optimizing the legitimate monitor’s jamming power allocation, subject to the average power constraint. The optimal jamming power allocation solutions are derived in closed-form for each of the two protocols, respectively. Numerical results show that the proposed proactive eavesdropping approach can noticeably improve the eavesdropping rate compared to the reference schemes.