Optimization Strategy for RIS-Assisted SWIPT-IoTs with Non-Linear Energy Harvesting.

Reconfigurable Intelligent Surfaces (RIS) are an upcoming paradigm being considered for the next generation wireless communications with their controllable, energy efficient and near-passive features. Simultaneous wireless information and power transfer (SWIPT) along with RIS, can facilitate power-deprived and data-intensive demands of Internet-of-Things (IoT) applications. This paper examines an IoT system that utilizes time-switching (TS) for SWIPT with non-linear energy harvesting (EH) technology, which receives concurrent information and energy from the concerned base station via RIS. We formulate three problems to optimize the independent objectives of rate, EH and transmit power respectively, under various sets of constraints. Subsequently, we propose suitable alternating optimization based algorithm by leveraging the divide-and-conquer approach to solve the aforementioned problems. A comparison with joint parameter optimization and baseline solution highlights the proficiency of the algorithm. Our numerical findings ratify the necessity to have large number of RIS elements and to have their placement closer to the base station and the user, for the SWIPT-IoT system to reap maximum benefits.