Optimised power allocation for a power beacon-assisted SWIPT system with a power-splitting receiver

ABSTRACT This article studies a power beacon (PB)-assisted simultaneous wireless information and power transfer (SWIPT) system, where a base station (BS) sends information, and a PB transfers radio frequency energy to a receiver equipped with a power-splitting (PS) structure to decode information and harvest energy simultaneously. First, we jointly design the transmit power of the PB and the PS ratio, to formulate the minimum transmit power at the PB problem under the constraints of minimum energy harvesting and the minimum signal-to-interference-plus-noise ratio. Unfortunately, the problem is not always feasible, and thus, we provide the conditions to guarantee the feasibility of the problem and derive the analytical optimal solution by the Lagrange method and Karush–Kuhn–Tucker optimality conditions. Second, we consider a receiver with the capability of cancelling the interference from the PB, and we obtain the optimal solution to the minimum PB transmit power problem. Next, we consider the transmission power at the BS as another optimisation variable and solve the minimisation problem with an objective function represented by the transmit power at the BS plus the transmit power at the PB. Finally, numerical results verify the optimality of the proposed approaches in comparison with three benchmark schemes.