Physical Layer Security Transmission For UAV Networks

With the rapid development of the unmanned aerial vehicle(UAV)industry,UAV communication will become a new technology in wireless communication in the future,which can be exploited to expand wireless communication coverage and enhance communication capabilities.Meanwhile,the application of UAVs also brings many new problems to wireless communication,and the most challenging issue is secure transmission.Physical layer security(PLS)transmission technology utilizes the difference between legitimate and eavesdropping channels to design signal transmission and processing mechanisms to ensure the UAV networks’ information transmission safety.In addition,an intelligent reflecting surface(IRS)can adjust the reflection phase shift and amplitude of the passive reflecting elements,aiming to reshape the wireless propagation environment,thereby significantly improving the performance of the wireless communication system.Moreover,how to realize the design of the UAV network physical layer security transmission scheme has become a fundamental challenge to be solved urgently.This paper will research the joint optimization of UAV position,trajectory,beamforming,and IRS reflection beamforming and position.The main objective is to ensure the security of UAV communication physical layer security transmission technology.The main contributions are summarized as follows:(1)Physical layer security transmission of UAV networks based on power allocation:For the secure transmission problem of UAV mobile relay networks where the channel state information of eavesdroppers is partially known,physical layer security transmission technology is used to ensure the security of information transmission.We put forward the secrecy rate maximization problem by optimizing the source/relay transmission power.The objective function and constraints are non-convex.We convert the non-convex problem into convex by introducing the difference-of-convex(DC)programming and slack variables.The simulation results show that the security rate of the proposed communication scheme is improved by about 12.7 times and is close to the security rate based on the perfect location information scheme,and the minimum gap between the two is 0.3%.(2)Physical layer security transmission of UAV networks based on path planning:For the secure transmission problem of UAV mobile relay networks,based on the previous research,an eavesdropper imperfect channel model is considered,and the UAV trajectory and power allocation are further jointly designed.The original optimization problem is decomposed into two independent sub-problems,power allocation optimization for fixed UAV trajectory and UAV trajectory optimization for fixed power allocation.The DC algorithm is exploited to obtain the optimal power allocation,and the successive convex optimization method is exploited to obtain the optimal trajectory.Finally,the joint design of the UAV trajectory and power allocation is realized by the alternate iterative optimization algorithm.The simulation results show that the security rate improves by 31.1%with the joint optimization scheme proposed in this paper.(3)IRS assisted physical layer security transmission of UAV networks:For the secure transmission of UAV and IRS assisted mm Wave networks,the elevation angle-dependent probabilistic LoS air-to-ground channel model is exploited,and artificial noise is exploited to prevent eavesdroppers from receiving confidential information.It is proposed to maximize the security rate by jointly designing the UAV position,beamforming,IRS position,and passive beamforming.The original optimization problem is non-convex and has highly coupled high-dimensional variables.Thus the original problem needs to be decomposed into two sub-problems:design UAV-BS and IRS positions and design UAV-BS and IRS beamforming.An ideal beamforming model is proposed to find near-optimal positions for UAV-BS and IRS.Then,the semi-definite relaxation(SDR)is exploited to deal with highly coupled and high-dimensional variable vectors.Finally,we obtain a sub-optimal solution by an efficient and lowcomplexity alternating optimization algorithm.The simulation results show that the security rate is improved by about.two times by jointly designing the UAV-BS and the IRS position.The security is improved by 3.4 times compared with the random beamforming scheme.(4)Multi-IRS jointly assisted physical layer security transmission of UAV networks:For the challenge of communication security and energy limitation of multiple IoT devices,a SWIPT scheme is designed.The UAV and multi-IRS enhance the physical layer security transmission and extend the SWIPT operating range.It is proposed to send information and energy to multiple singleantenna information users and energy receivers through the UAV base station(UAV-BS)and deploy IRSs to assist SWIPT.Furthermore,we jointly design the position,transmit beamforming of UAV-BS,and the passive beamforming of multi-IRS with the minimum total transmit power at UAV-BS.At the same time,the security transmission requirements of the networks are met.To solve this non-convex problem with high coupling and high-dimensional variables,an ideal beamforming model is proposed to decouple the position variables and the beamforming vectors.The novel penalty-based algorithm(PBA)and block coordinate descent(BCD)are exploited to design transmission and passive beamforming jointly.The simulation results show that the transmit power requirement is reduced by 58%,and the range of SWIPT is extended by 1.7 times with the proposed scheme.