Throughput Optimization for RIS-assisted SWIPT-IoTs with Hardware Impairments

Abstract

A highly transformative technology termed reconfigurable intelligent surfaces (RISs), with its competence to manipulate the radio communication environment and enhance system performance, has attracted considerable interest in the beyond 5G (B5G)/6G framework. Advent of massive connected Internet-of-Things (IoT) devices demands for higher data rate and energy saving options pertaining to specific application. This apprehension can be tackled by Simultaneous Wireless Information and Power Transfer (SWIPT) technique along with RIS. This paper explores, the power-splitting (PS) based SWIPT architecture deployed at the IoT node with non-linear energy harvesting (EH) model. An analytic phase shift model is used that showcases the variations in reflection amplitude that occur herein based on the phase of the RIS elements. We formulate rate maximization problem for optimal phase shift under Quality-of-Service (QoS) constraints. An iteration based optimization algorithm adopting divide-and-conquer methodology is used to solve the aforementioned problem. Numerical evaluation confers that to have a higher data rate, more RIS elements and its closer placement to base station and user is needed.