Optimizing Sum-Rate in RIS-Assisted Multi-User OFDMA Systems with Time Switching-based Non-Linear Energy Harvesting

A highly promising technology proposed for wireless communications beyond $5 \mathrm{G}(\mathrm{B} 5 \mathrm{G}) / 6 \mathrm{G}$ is coined in the form of Reconfigurable Intelligent Surfaces (RIS). This technology is characterized by its spectral efficiency, battery savings, and environmental controllability. Simultaneous Wireless Information and Power Transfer (SWIPT) along with RIS can assist powerneedy and data demand in Internet-of-Things (IoT) applications. This research examines the allocation of resources in multiuser Orthogonal Frequency Division Multiple Access (OFDMA) wireless networks with single-RIS assistance. It implements the Time Switching (TS) technique for SWIPT with Non-Linear Energy Harvesting (NL-EH) at the IoT nodes/users. We aim to maximize the entire system’s sum-data rate while adhering to Quality-of-Service (QoS) constraints by optimizing the time switching factor, sub-carrier assignment matrix, and power allocation to sub-carriers. An iterative-based alternating optimization utilizing a divide-and-conquer mechanism is employed to solve the aforementioned problem. From our simulation results, it is evident that an increased number of RIS elements and sub-carriers is necessary to obtain a higher sum data rate.