Outage Probability Analysis and Transmit Power Optimization for Blind-Reconfigurable Intelligent Surface-Assisted Non-Orthogonal Multiple Access Uplink

Abstract

Fifth-generation (5G) advancements improve transmitter and receiver functionalities, but the propagation environment remains uncontrolled. By changing the phase of impinging waves, reconfigurable intelligent surfaces (RIS) have the potential to regulate radio propagation environments. RIS-assisted non-orthogonal multiple access (NOMA) improves spectrum efficiency while enabling massive connectivity. The uplink outage probability expressions for blind-RIS-NOMA are derived in this work using RIS as a smart reflector (SR) and RIS as an access point (AP). Extensive Monte-Carlo simulations are performed to validate the derived closed-form expressions. The optimal powers to be allocated to the users are also derived in order to maximize the uplink sum capacity. In comparison to the sub-optimal power allocation, the optimal power allocation enhances the sum capacity. In terms of sum capacity for 20 dB signal-to-noise ratio (SNR) and 32 reflecting elements, it is demonstrated that the blind-RIS-NOMA surpasses the conventional NOMA by ≈38%. The sum capacity and outage performances are enhanced by the addition of RIS elements.