Performance Analysis of Energy Harvesting NOMA Systems with IOT Relay Selection and Untrusted User Presence

Internet of Things (IOT) is a promising technology has been proliferated in modern communication systems. Besides, most of the IOT devices are energy constrained and need an external energy source to recharge their batteries. In this study, our aim is to study a non-orthogonal multiple access (NOMA) network with multiple energy constrained IOT relays, in which the source node wants to communicate with its own destination through one of the energy constrained IOT relays. Meanwhile, the destination for the source message (far NOMA user), plays the role of an untrusted user and wants to eavesdrop the IOT relay message. We evaluate the impact of relay selection and the presence of untrusted user on the performance of the system considering the outage probability (OP) and the secrecy outage probability (SOP) metrics. We validate our analytical results via providing simulation results that also show the effect of various system parameters on the considered network performance and the superiority of NOMA scheme over OMA scheme.