Research On The Physical Layer Security Transmission Scheme Of Dual-Hop OMA And NOMA Systems

The arrival of the fifth generation of mobile communication(5G)era has increased the demand for high-speed mobile wireless networks.At the same time,with the vigorous development of the Internet of Things and the popularization and application of intelligent terminals,multi-hop relay transmission of information is very common,and there is a risk of information being eavesdropped,which has caused the problem of the safe transmission of new business information between mass communication devices.extensive attention.The introduction of key encryption technology can improve the security of the communication system to a certain extent,but the continuous enhancement of computer computing power and the emergence of quantum computing make the security of wireless mobile communications face more serious challenges.In this context,the physical layer security technology can use its own unique wireless channel characteristics to achieve safe and reliable transmission of information,effectively overcome the traditional security technology's shortcomings that rely on eavesdroppers' limited computing power,and at the same time meet the reliability and security of wireless communication Requirements,and thus received extensive and in-depth research.From the perspective of secure transmission at the physical layer,this paper studies the secure transmission of orthogonal multiple access(OMA)and non-orthogonal multiple access(NOMA)in a two-hop relay system to maximize the security rate.The contents are as follows:(1)The representative time division multiple access(TDMA)protocol in OMA technology is selected,and the safe transmission problem of the relay system under the TDMA protocol is proposed.The optimization problem of the system is modeled under the two situations of uniform transmission slot allocation and optimal allocation.Since the optimization problem is not convex,this paper uses the(Minorization-Maximization,MM)method to solve the optimization problem,and gives the power optimization solutions respectively.And the approximate optimal solution of the joint time slot and power optimization scheme,the simulation part analyzes and compares the safety performance of the two optimization schemes.(2)Considering a double-hop relay system based on NOMA protocol,the source node transmits information to the relay node through broadcasting,and the relay node forwards the information to the destination node through the multi-access link.In order to maximize the safe transmission rate of the system,this paper models the optimization problem of the information transmission power distribution coefficient of the source node and the relay node.Because the optimization problem is non-convex optimization,it is difficult to solve it directly using traditional methods.This paper proposes an iterative optimization algorithm based on the MM method,which approximates the non-convex problem to a convex problem.In each iteration,the Lagrange dual algorithm gives A closed solution is used,and a convex optimization toolbox is used to obtain the optimized power distribution coefficient to maximize the secrecy rate of the NOMA double-hop relay system.In order to verify the performance advantages of the NOMA protocol,the simulation part compares the optimized solution under the NOMA protocol with the safety rate of the relay system under the traditional TDMA protocol,and proves that the NOMA optimized power allocation scheme proposed in this paper can be significantly compared to the traditional TDMA protocol Improve the secure transmission performance of information in the double-hop relay system.