Improving Performance of STAR-RIS-Based NOMA Systems by Full-Duplex Cooperative-Based SWIPT Mechanism

Abstract

Simultaneous wireless information and power transfer (SWIPT) has become a key enabler for sustaining energy-constrained Internet-of-Things (IoT) devices, while simultaneous transmission and reflection reconfigurable intelligent surfaces (STAR-RIS) provide enhanced coverage and beamforming flexibility by serving users on both sides of the surface. Motivated by these advantages, this paper investigates a STAR-RIS-assisted SWIPT-enabled cooperative non-orthogonal multiple access (CNOMA) network, where the proximate user operates in full-duplex (FD) mode with separate transmit/receive antennas and employs a power-splitting (PS) architecture to harvest energy from the source’s radio-frequency signal. Closed-form expressions for the outage probability (OP) and ergodic capacity (EC) are derived under generalized fading conditions, and asymptotic analyses are conducted to characterize the fundamental performance limits and diversity behavior. The analytical results are validated through Monte Carlo simulations, which demonstrate that the proposed STAR-RIS-enhanced SWIPT-CNOMA system achieves substantial performance gains over conventional half-duplex (HD) and orthogonal multiple access (OMA) baselines. Furthermore, the impacts of key system parameters, including the PS factor, fading severity, and the number of STAR-RIS elements, are quantified to provide practical insights for the design of energy- and spectrum-efficiency in IoT networks.