Partitioning-Based IRS-Assisted Co-operative NOMA Networks with Mode Switching and Energy Harvesting Enabled Near User

This paper investigates the performance of a partition-enabled intelligent reflecting surface (IRS)-assisted cooperative non-orthogonal multiple access (C-NOMA) framework. In this setup, the source communicates with wireless powered near user (NU) directly as well as via the IRS, and with the far user (FU) solely through the IRS. Since the harvested energy is typically small, use of the IRS is explored (for the first time in literature) in the second phase of C-NOMA transmission to boost the FU performance. The system opportunistically switches between NOMA and C-NOMA modes using a feedback-based strategy to enhance user fairness. When operating in C-NOMA mode, the NU harvests energy for relaying information to the FU, which ensures that the NU does not have to expend its own energy for relaying, and also improves the overall energy efficiency (EE) due to use of the IRS in the second phase of C-NOMA transmission. Closed-form expressions for NU and FU throughputs, as well as EE are derived for the first time while considering wireless power transfer (WPT), as well as IRS partitioning and mode switching. These expressions are validated through Monte Carlo simulations.