Online Power and Time Allocation in MIMO Uplink Transmissions Powered by RF Wireless Energy Transfer

摘要

Wireless energy transfer (WET) has been audpromising technology to tackle the lifetime bottlenecks ofudenergy-limited wireless devices in recent years. In thisudpaper, we study a WET enabled multiple input multipleudoutput (MIMO) system including a base station (BS) anduda user equipment (UE), which has a finite battery capacity.udWe consider slotted transmissions, where each slot includesudtwo phases, namely downlink (DL) WET phase and uplinkud(UL) wireless information transmission (WIT) phase. Inudthe WET phase (a fraction τ of a slot), the BS transfersudenergy and the UE stores the received energy in the battery.udIn the WIT phase (a fraction 1 − τ of a slot), the UEudtransmits information to the BS by using the energy in theudbattery. Considering the power sensitivity α of the radioudfrequency (RF) to direct current (DC) conversion circuits,udthe BS transfers energy only if the UE received powerudis larger than α, and the downlink WET is formulatedudas a Bernoulli process. Based on the formulation, weudpropose an online power and time allocation algorithmudto maximize the average data rate of uplink WIT. We alsoudextend the proposed algorithm to multiple user systems.udThe numerical results show that the proposed algorithmudoutperforms the existing schemes in terms of average dataudrate, energy efficiency and outage probability.