Research On Physical Layer Security Technology Based On IRS Backscatter

With the rapid development of mobile communication technology,wireless networks have brought convenience to people’s lives but also face increasingly serious security threats.Specifically,due to the broadcast nature of wireless channels,transmitted data is susceptible to malicious attacks such as jamming,eavesdropping,and tampering.Additionally,criminals may exploit wireless communications to transmit illegal information and engage in conspiracy activities.Therefore,ensuring secure data transmission and monitoring suspicious entities are critical concerns in wireless networks.To achieve secure communication,physical layer security(PLS)leverages the characteristics of wireless channel without requiring complex encryption algorithms,key distribution and security protocols.However,PLS also faces some challenges such as high hardware costs,computational complexity,and increased transmit power due to the deployment of friendly jammers and relays.To tackle these issues,intelligent reflecting surface(IRS)backscatter has been proposed.As a promising technique,IRS backscatter enables IRS to function not only as a passive relay but also as a passive transmitter,which may bring new opportunities to PLS.Therefore,this dissertation focuses on the study of PLS technology based on IRS backscatter and designs a series of efficient solutions to resist eavesdropping and jamming attacks,and monitor suspicious communication.The security performance of wireless network is then analyzed and optimized using convex optimization tools.Moreover,to explore the potential applications of IRS backscatter,this dissertation proposes the use of aerial IRS backscatter technique to facilitate smart and secure vehicle-to-everything(V2X)communications.The main contributions of this dissertation include:1.This dissertation proposes an IRS backscatter enhancing strategy to defend against both eavesdropping and malicious jamming attacks.In this strategy,jamming signal is modulated into desired signal and reflected to the legitimate user to increase the received power.The aim is to maximize the secrecy rate in multiple-input multiple-output(MIMO)communication networks.To solve this non-convex optimization problem,the weighted minimum meansquare error(WMMSE)method is used to transform it into three subproblems,which are then solved using the block coordinate descent(BCD)algorithm.Specifically,the active beamforming at the base station(BS)is optimized using the Lagrange multiplier method,while the backscatter coefficient matrix of the IRS is optimized using the majorization-minimization(MM)algorithm.The experimental results demonstrate that the proposed strategy has significant advantages in enhancing system security performance compared to conventional IRS based PLS strategy and IRS backscatter based artificial noise(AN)strategy.Moreover,even when considering channel estimation errors,the proposed strategy exhibits good robustness.2.This dissertation studies an IRS backscatter assisted surveillance system.In this system,the IRS can improve the monitoring link quality by passively reflecting the incident signal to the monitor,while also backscattering the incident signal into AN to interfere with the suspicious receiver.This dissertation jointly designs the IRS reflection coefficients,position,and allocation of different functional IRS elements to maximize the effective eavesdropping rate.Firstly,three IRS strategies are proposed,including Enhancing-Strategy,Jamming-Strategy and Hybrid-Strategy,based on the given IRS position.Then,an IRS placement algorithm based on simulated annealing(SA)is designed for optimizing the IRS deployment.The experimental results indicate that the proposed strategies can significantly improve the effective eavesdropping rate of the system and outperforms both the No IRS and relay strategies.3.This dissertation studies a double-IRS assisted surveillance system where the direct link from the suspicious source to the monitor is blocked.To maximize the effective eavesdropping rate,this dissertation proposes two double-IRS strategies: Double-IRS Enhancing Strategy and Double-IRS Enhancing-Jamming Strategy.In the former strategy,both cooperative IRSs reflect the incident signal passively.In the latter strategy,one IRS performs passive reflection while another IRS performs backscatter to modulate the incident signal into AN to deteriorate the suspicious link.Based on these two strategies,the semidefinite relaxation(SDR)technique and the bisection search method are applied to optimize the reflection coefficients at two IRSs.The experimental results show that the proposed strategies have greater advantages in improving system performance compared to deploying a single IRS and active relay.4.Upon the above mentioned research work,this dissertation introduces an aerial IRS backscatter technique to facilitate V2 X communication.Specifically,IRS is deployed on the unmanned aerial vehicle(UAV)for flexible deployment in three-dimensional space,resulting in an aerial passive relay and transmitter.This dissertation further elaborates the design of an aerial IRS backscatter assisted vehicular network architecture,and explores potential application scenarios for smart and secure V2 X communication.Finally,this dissertation proposes an aerial IRS backscatter based anti-jamming road perception strategy.In this strategy,the IRS transmits its perceived road information to a vehicle by modulating the jamming signal from the jammer and interfering signal from the BS into information signal.Experimental results confirm the superiority of the proposed strategy over ground-based stationary IRS strategy and UAV-carried active antennas strategy.In conclusion,this dissertation studies the use of IRS backscatter to resist eavesdropping and jamming attacks,and monitor the suspicious communication in wireless networks.A series of PLS strategies are proposed including IRS backscatter enhancing strategy,single-and double-IRS assisted monitoring strategies,and an aerial IRS backscatter based anti-jamming road perception strategy.This dissertation offers valuable insights for the design of security schemes based on IRS backscatter in future wireless communication scenarios.