Proactive Eavesdropping Scheme Design In UAV-Aided Communications

The rapid proliferation of infrastructure-free wireless communication networks(e.g.,device-to-device communications and unmanned aerial vehicle-enabled communications)has brought new challenges to public safety.The suspicious users may misuse these communication networks to engage in illegal activities such as terrorist attacks and theft of commercial secrets.Therefore,it is increasingly necessary for the government and authorized parties to monitor suspicious communication links effectively,so as to complete the intelligence collection,crime prevention and investigation.This thesis focuses on the proactive eavesdropping scheme design in UAV-aided communication systems,the details are as follows:(1)A jamming scheme to maximize the achievable eavesdropping rate is proposed in a UAV-aided suspicious transmitter communication scenario.The UAV-aided suspicious transmitter automatically adjusts its location to maximize the minimum suspicious rate of all suspicious receivers.By using the characteristic of the suspicious system,the legitimate monitor optimizes the jamming power to maximize the effective eavesdropping rate.In order to solve the original non-convex optimization problem,a successive convex approximation based iterative algorithm is first developed.Based on this result,the optimal jamming power is obtained by the one-dimensional search method.In addition,this paper also studies the special case of two suspicious receivers for gaining more useful insights on designing the optimal jamming transmission strategy.Numerical results show that the proposed proactive jamming approach can significantly enhance the achievable eavesdropping rate.(2)The jamming power allocation schemes to maximize the average eavesdropping rate are proposed in a UAV-aided suspicious relay communication scenario.We consider two relaying protocols commonly used by the UAV-aided relay,namely,amplify-and-forward and decode-and-forward.For each relaying protocol,the corresponding optimization problem is formulated.To tackle these two problems,we first verify that the two optimization problems satisfy the time-sharing property,thus guaranteeing a zero duality gap.Next,the Lagrange dual method is used to attain the optimal solutions 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.(3)A jamming scheme to maximize the sum effective eavesdropping rate is proposed in a UAV-aided legitimate monitor communication scenario,where the monitor eavesdrops on multiple suspicious links.Subject to the power constraint,the UAV-aided legitimate monitor optimizes the location and jamming power to maximize the sum eavesdropping rate.By using the mobility of the UAV,the legitimate monitor can not only degrade the SINRs at suspicious receivers,but also change the location for the effective eavesdropping.