Optimal Time-Switching for Simultaneous Wireless Information and Power Transfer

Abstract

The receiver is an important part of a simultaneous wireless information and power transfer (SWIPT) system. A single receiver that can simultaneously decode and harvest power from the same signal has yet to be developed, so practical schemes utilizing multiple co-located receivers have been utilized instead. Time-switching is one such scheme in which a receiver either performs information decoding or power harvesting, the durations of which are determined by the time-switching ratio. Existing methods to optimize the time-switching ratio either exploit problem convexity or reformulate it into a form that can utilize the Lambert W function. However, these techniques do not easily lend themselves for use with more complicated non-convex problem formulations. As an alternative, this paper examines the geometrical relationship between the optimal time-switching ratio and the weights used to solve the resource allocation problem when framed as a weighted sum. A simple relation is derived that will form the basis for an optimization algorithm in future works.