Optimal wireless power transfer scheduling for delay minimization

Wireless power transfer (WPT) technique enables wireless charging/recharging, thus is a promising way to power wireless devices' transmissions. Because current WPT technique requires a wireless device to stop transmitting data when receiving power, and also because the received power in this way is limited, careful scheduling is needed to decide when the device should receive power and when it should transmit such that data can be efficiently transmitted. This paper assumes the most fundamental point-to-point White Gaussian Noise channel is used for data transmission and attempts to obtain an optimal scheduling such that a sequence of data packets can be transmitted with the minimum delay. It is discovered that, for all (energy receiving, data transmitting) cycles, except the last one, the optimal transmission rate should be a constant which is called the wOPT rate. Based on this discovery, this paper optimally solves the offline delay minimization problem. Then, an online heuristic scheduling algorithm is proposed, which either receives energy or transmits at the wOPT rate. Simulations have demonstrated its efficiency. The discovery of the wOPT rate reveals an essential property of WPT, thus is expected to make significant impact in the field of WPT.