Research On Friendly Jammer Selection-Assisted Physical-Layer Security Under Imperfect Channel State Information

With the widespread use of mobile smart terminals,wireless communication is gradually replacing wired communication with its outstanding convenience,and the requirements for transmission reliability and security of wireless services are constantly increasing.However,the broadcast characteristics of electromagnetic signals make legal information transmission highly susceptible to eavesdropping.In response to this challenge,physical layer security technology exploits the inherent physical characteristics of wireless channels to effectively defend against illegal eavesdroppers.The existing research on physical layer security has mainly considered perfect channel state information and ignored the impact of channel estimation errors on physical layer security performance.In this context,this thesis investigates multi-antenna physical layer security technology based on friendly jammer in imperfect channel environments.The main research content and innovations are as follows:Firstly,a multi-antenna transmission system with joint multiuser scheduling and friendly jammer selection is studied,in which legitimate users transmit its confidential information to the base station,while another legitimate user is selected as the friendly jammer to transmit artificial noise to suppress illegal theft of information transmitted by eavesdroppers to legitimate user.Considering channel estimation errors,the joint multiuser scheduling and random jammer selection(MS-RJS)and joint multiuser scheduling and random jammer selection(MS-OJS)schemes are proposed,while the conventional multiuser scheduling scheme is used as a benchmark,and the approximate closed-form expressions for intercept probability and outage probability of the proposed schemes are derived.The simulation results show that the proposed schemes have security-reliability tradeoff performance than the traditional multiuser scheduling scheme.Secondly,the optimization of the security-reliability tradeoff performance of multi-antenna transmission systems in imperfect channel environments is studied for the power resource allocation problem of scheduled user and friendly jammer.Considering that there are multiple eavesdropping nodes in the system that collaborate to obtain legitimate user transmission information,and with limited total system power,the approximate closed-form expressions for intercept probability and outage probability of MS-RJS and MS-OJS schemes under the scenario of multiple eavesdroppers are derived.With the goal of minimizing the sum of intercept probability and outage probability,an optimal power allocation iterative algorithm based on golden search is designed.The simulation results show that compared to equal power allocation schemes,the MS-RJS and MS-OJS schemes based on optimal power allocation further improve the security-reliability tradeoff performance.Finally,a friendly jammer-assisted multi-node wireless transmission system is studied,in which the source node transmits its confidential information to the destination node and the friendly jammer node is used to emit artificial noise to deteriorate the eavesdropping performance.Considering that multiple eavesdropping nodes obtain legitimate information transmitted by legitimate user through non cooperative means,a friendly jammer assisted transmission scheme for multiple eavesdroppers’ non-collaborative scenarios is proposed.The non friendly jammer-assisted transmission scheme is used as a benchmark,and the closed-form expressions for the strictly positive secrecy capacity of the proposed schemes are derived.The simulation results show that the proposed scheme reduces the probability of the strictly positive secrecy capacity performance compared to the non-friendly jammer scheme.