In this paper, we study the physical layer security (PLS) of a radio frequency energy harvesting (RF EH) non-orthogonal multiple access (NOMA) relaying network where relay-user selection scheme and secrecy performance optimization are investigated. Specifically, we consider a scenario, where the energy-constrained users from two different user clusters harvest RF energy from the selected relay to transmit their messages to a destination with the help of a relay cluster in the presence of a passive eavesdropper. To enhance the PLS performance of the considered system, we propose a relay and user selection scheme and an optimal algorithm to find the best system parameter set including time switching ratio and power allocation ratio, which can bring the best secrecy performance for the system. Accordingly, to evaluate the secrecy performance, the closed-form expressions of secrecy outage probability are derived. Moreover, the impacts of the network parameters on the secrecy performance are investigated to achieve more insight into the behavior of NOMA relaying network with RF EH. Finally, the accuracy of our analysis is verified by Monte-Carlo simulation results.

在本文中，我们研究了射频能量收集 (RF EH) 非正交多址 (NOMA) 中继网络的物理层安全 (PLS)，其中研究了中继用户选择方案和保密性能优化。具体来说，我们考虑一个场景，其中来自两个不同用户集群的能量受限用户从选定的中继收集射频能量，以在存在被动窃听者的情况下借助中继集群将其消息传输到目的地。为了提高所考虑系统的PLS性能，我们提出了一种中继和用户选择方案以及一种最优算法，以找到包括时间切换比和功率分配比在内的最佳系统参数集，从而为系统带来最佳保密性能。因此，为了评估保密性能，导出了保密中断概率的闭式表达式。此外，研究了网络参数对保密性能的影响，以更深入地了解具有 RF EH 的 NOMA 中继网络的行为。最后，通过蒙特卡罗模拟结果验证了我们分析的准确性。