Empowering Reconfigurable Intelligent Surfaces for Security of Downlink NOMA

Abstract

Reconfigurable intelligent surfaces (RIS) and non-orthogonal multiple access (NOMA) are promising techniques to develop next-generation wireless systems. While RIS has huge potential to create massive device connectivity, NOMA exhibits its spectrum efficient communication among multiple access approaches. RIS is a passive device made up of low-cost meta-surfaces which can control the propagation of radio waves, and it is easily deployable in lots of applications in the Internet of Things. The full-duplex nature of RIS has also been a major reason for its consideration of major emerging and trending technologies. In this paper, we aim to investigate the secrecy performance of the RIS-NOMA-assisted Internet of Things (IoT) systems in the presence of two legitimate users who belong to a cluster, and those devices are associated with the existence of an eavesdropper situated close to such a cluster. This paper considers the devices in the presence of RIS and an eavesdropper. As main performance metrics, the closed-form expressions for secrecy outage probability (SOP) and strictly positive secrecy capacity (SPSC) are derived to evaluate the performance of legitimate users. Simulations are performed in support of the Monte-Carlo method, and the obtained results show that in most of the cases, the number of meta-surfaces in RIS and signal-to-noise ratio (SNR) levels at the source also plays a pivotal role in influencing the secure performance of the system.