Research On Physical Layer Security Of Performance Of Non-orthogonal Multiple Access System

As the key technology of the fifth generation(5G)mobile communication network,non-orthogonal multiple access(NOMA)technology can effectively improve the spectral efficiency of the system,realize the business requirements of large bandwidth,wide connection and low power consumption,and will be widely used in industry,medical and agricultural fields.However,the wide connection characteristics make the security transmission of device information seriously challenged.How to ensure the secure transmission of information is worthy of in-depth study.Physical layer security(PLS)technology makes use of the random characteristics of wireless channel to ensure the secure transmission of wireless communication information,which has become the focus of the industry.In this paper,the PLS performance of NOMA downlink system with non-ideal hardware condition is studied in depth considering the actual communication system hardware device state.The main research work and achievements are summarized as follows:1.In the actual communication system,there are various types of hardware impairment(RHI)in the transceiver hardware equipment,and the inaccurate estimation of RHI will seriously affect the design of system parameters in practical application.In order to study the impact of RHI on the PLS performance of relay cooperative NOMA system,this paper establishes a single eavesdropping multi relay cooperative NOMA system model based on RHI firstly,and analyzes the PLS performance of the system.Secondly,in order to improve the performance of PLS,a relay transmission scheme is proposed to maximize the target signal-to-noise ratio of the system by considering the signal information of legitimate link and eavesdropping link.The performance of PLS is characterized by secrecy outage probability(SOP).Finally,the SOP under the asymptotic condition is derived to intuitively measure the performance of secrecy outage Simulation results show that compared with the two traditional relay transmission schemes,the proposed relay selection scheme can achieve better performance,and the PLS transmission can be improved by increasing the number of relays.In addition,when there is RHI in the system,it will affect the SOP of the system,and the RHI at different nodes has different impact on the PLS performance of the system.2.In order to further improve the PLS performance of the system under consideration,this paper uses 6G reconfigurable intelligent surface(RIS)technology to adjust the wireless environment,enhance the coverage and capacity,and combines RIS with NOMA technology to improve the transmission performance of the system.Based on this,this paper establishes a single eavesdropping RIS assisted downlink NOMA system model based on RHI,and studies the impact of RHI on the PLS performance of the system.Specifically,based on the model,the approximate closed form expression of user SOP is derived.In order to further study the difference between deploying RIS in orthogonal multiple access(OMA)and deploying RIS in NOMA,the simulation part compares the secrecy outage performance of the two systems.The results show that,compared with traditional NOMA system and RIS assisted OMA system,RIS assisted NOMA system can achieve better security performance.In addition,the influence of RHI on the system performance depends on the signalto-noise ratio,target data rate and the number of reflection units.