Wireless energy transfer (WET) has been a#R##N#promising technology to tackle the lifetime bottlenecks of#R##N#energy-limited wireless devices in recent years. In this#R##N#paper, we study a WET enabled multiple input multiple#R##N#output (MIMO) system including a base station (BS) and#R##N#a user equipment (UE), which has a finite battery capacity.#R##N#We consider slotted transmissions, where each slot includes#R##N#two phases, namely downlink (DL) WET phase and uplink#R##N#(UL) wireless information transmission (WIT) phase. In#R##N#the WET phase (a fraction τ of a slot), the BS transfers#R##N#energy and the UE stores the received energy in the battery.#R##N#In the WIT phase (a fraction 1 − τ of a slot), the UE#R##N#transmits information to the BS by using the energy in the#R##N#battery. Considering the power sensitivity α of the radio#R##N#frequency (RF) to direct current (DC) conversion circuits,#R##N#the BS transfers energy only if the UE received power#R##N#is larger than α, and the downlink WET is formulated#R##N#as a Bernoulli process. Based on the formulation, we#R##N#propose an online power and time allocation algorithm#R##N#to maximize the average data rate of uplink WIT. We also#R##N#extend the proposed algorithm to multiple user systems.#R##N#The numerical results show that the proposed algorithm#R##N#outperforms the existing schemes in terms of average data#R##N#rate, energy efficiency and outage probability.
['Kai Liang', 'Liqiang Zhao', 'Kun Yang', 'Xiaoli Chu']
Online Power and Time Allocation in MIMO Uplink Transmissions Powered by RF Wireless Energy Transfer