Research On Relay Selection For The Secure NOMA Transmission

As an emerging technology,Physical Layer Security(PLS)is widely used in traditional wireless transmission scenarios,it uses the physical characteristics of wireless channels to achieve information confidentiality.Non-orthogonal multiple access(NOMA)technology became one of the most important research techniques in the next generation communication network.the transmitter uses superposition encoding method to transmit signals,and the receivers use successive interference cancelation(SIC)to eliminate the interference,and also use multiple access technology to improve the spectrum efficiency at the same time block.In this paper,we combine PLS and NOMA technology to study the problem of relay selection for NOMA Wireless Network.The existing researches mainly focus on the assumption that the base station knows the perfect Channel State Information(CSI)of the eavesdropping Channel,and the PLS technology is used to guarantee the safe transmission of information.In this paper,PLS problem based on NOMA scenario is studied,where additional jamming nodes are added to send artificial noise(AN),and multiple relayes are used for cooperating base stations to transmit secure signals.In the previous scenario where PLS and NOMA technologies were combined,the influence of AF relay and DF relay on the safety performance of the system was studied.In this paper,in the case of ICSI of eavesdropping users,where multiple intermediate nodes cooperate with the base station to transmit signals using DF technology,AN is used to weaken the eavesdropping of eavesdropping users.Select one node from the intermediate nodes as the relay node to maximize the secure transmission rate of NOMA users at the near end while ensuring the quality of service of NOMA users at the far end.It can effectively ensure the fairness and reliability of the system.Under the constraint of appropriate security transmission thresholds,this article uses the security outage probability(SOP)as performance index,and finally get the closed solution expression of the system.The influence of power distribution factor,interference power and the number of intermediate nodes on system performance is further studied.Asymptotic analysis of the system shows that SOP tends to be a constant at high SNR.Finally,by comparing the montecarlo simulation and the theoretical value,the results show that the proposed scheme can ensure fairness and effectively improve the security transmission rate of NOMA system,the right set of the interference power and power allocation factor,can effectively improve the performance of the system,compared with the traditional relay coordination schemes,this scheme can effectively improve the safety performance of NOMA system.