Research On Physical Layer Security Of UAV-aided Mobile Relay Network

In recent years,UAV has attracted more attention because of lower costs and flexible deployment.One especially promising application of UAV is UAV-aided mobile relay.It can provide a reliable communication link for two or more users and realize information exchange between multiple users,the coverage of wireless communication is increased.The communication link between the UAV and the ground node is mainly line-of-sight(LOS),but this feature also means that potential eavesdroppers are more likely to eavesdrop.Therefore,ensuring the security of wireless communication has become an important issue.The traditional password-based security scheme cannot guarantee absolute security.The physical layer security technology mainly uses the randomness of wireless channel,the performance of physical layer security depends on whether the quality of legal channel is better than eavesdropping channel,and there is no possibility of being cracked.This thesis investigate a secure communication strategy based on physical layer security due to security challenges in UAV-aided mobile relay.Two typical security models of UAV-aided mobile relays are considered,using physical layer security technology to allocate resources reasonably,and optimizing the trajectory of UAVs.The main research contents of the secure transmission strategy are as follows:(1)Research on UAV-aided mobile relay security strategy.Based on the problem of information leakage caused by potential eavesdroppers,a mobile jammer-aided secure UAV relaying system is studied in this design.An additional cooperative UAV is dispatched to enhance security.One UAV acts as a mobile relay to support the communications between a source node and a destination node,and the other UAV acts as a mobile-friendly jammer,transmitting interference signals to reduce the channel quality of eavesdroppers.Based on the actual situation,this design studies the secrecy rate when the location of the eavesdropper is uncertain.By establishing an active interference model for potential eavesdroppers,using block coordinate descent theory and successive convex approximation method to comprehensively optimize time scheduling,transmission power,and flight trajectory,a reasonable and effective iterative algorithm is designed to maximize the average screcy rate.Simulation results demonstrate the effectiveness of the proposed algorithm compared with benchmark algorithms.(2)Research on UAV-aided two-way relay security strategy.In this design,the security problems in the UAV-aided two-way relay network based on physical layer network coding(PNC)is studied.The UAV is acted as an air mobile relay to communicate with ground users.Due to the risk of eavesdropping,the UAV relay uses its high mobility to improve the security performance.In this design,a friendly jamming UAV is also introduced to further improve the screcy rate.Considering the optimization of the transmission power of different users and UAVs,and combining the design of UAV trajectory to study the problem of maximizing the average screcy rate.An effective algorithm,based on convex optimization theory,transform the non-convex problem into a convex problem and obtian the lagest average secrecy rate.Numerical simulation results demonstrate the effectiveness of the algorithm.