NOMA系统中基于协作干扰的物理层安全方案

针对NOMA系统中的信息安全传输问题，提出基于协作干扰的物理层安全方案，该方案利用外部协作节点发送干扰信号恶化窃听者的接收性能。本文首先利用泊松点过程对协作节点和窃听者的位置进行安全建模，然后推导了随机协作干扰方案下系统保密中断概率的闭式解，但随机协作干扰方案会同时恶化合法用户的接收信号，性能有限，因此提出一种信道增益受限的协作干扰方案，该方案选择到近端用户和远端用户的瑞利信道因子均小于一定阈值的协作节点发送干扰信号，会对窃听者造成更严重的影响。仿真结果表明，在NOMA系统中采用受限的协作干扰方案能够有效提升系统安全性能。 

Physical Layer Security Schemes based on Cooperative Jamming for Non-Orthogonal Multiple Access System

Aiming at the secure transmission problem in downlink channel of non-orthogonal multiple access system, this paper proposes a secure scheme aided by cooperative jamming. In this scheme, the base cooperates with external nodes to send the jamming signals to worsen the receiving performance of eavesdroppers. Firstly, we use the Poisson point process to model the location of the cooperative nodes and the eavesdroppers. Then, we derive closed-form solution of the system outage probability under stochastic cooperative jamming scheme. But this scheme with limited performance gain which can affect both the legal users and eavesdroppers. Under this consideration, we further proposed a cooperative jamming scheme based on limited channel gain, this scheme chooses the cooperative nodes which the Rayleigh coefficient is less than a certain threshold, so it will cause more serious impact on the eavesdroppers. Simulation results demonstrate that the limited-cooperative jamming scheme can significantly improve the security performance of the system.