Wireless Charger Placement and Power Allocation for Maximizing Charging Quality

Wireless power transfer is a promising technology used to extend the lifetime of, and thus enhance the usability of, energy-hungry battery-powered devices. It enables energy to be wirelessly transmitted from power chargers to energy-receiving devices. Existing studies have mainly focused on maximizing network lifetime, optimizing charging efficiency, minimizing charging delay, etc. In this paper, we consider wireless charging service provision in a two-dimensional target area and focus on optimizing charging quality, where the power of each charger is adjustable. We first consider the charger <underline>P</underline>lacement and <underline>P</underline>ower allocation <underline> P</underline>roblem with <underline>S</underline>tationary rechargeable devices (SP<inline-formula> <tex-math notation="LaTeX">$^3$</tex-math><alternatives><inline-graphic xlink:href="zhang-ieq1-2771425.gif"/> </alternatives></inline-formula>): Given a set of stationary devices and a set of candidate locations for placing chargers, find a charger placement and a corresponding power allocation to maximize the charging quality, subject to a power budget. We prove that SP<inline-formula><tex-math notation="LaTeX">$^3$</tex-math><alternatives> <inline-graphic xlink:href="zhang-ieq2-2771425.gif"/></alternatives></inline-formula> is NP-complete, and propose an approximation algorithm. We also show how to deal with mobile devices (MP<inline-formula><tex-math notation="LaTeX"> $^3$</tex-math><alternatives><inline-graphic xlink:href="zhang-ieq3-2771425.gif"/></alternatives></inline-formula>), cost-constrained power reconfiguration (CRP), and optimization with more candidate locations. Extensive simulation results show that, the proposed algorithms perform very closely to the optimum (the gap is no more than 4.5, 4.4, and 5.0 percent of OPT in SP<inline-formula><tex-math notation="LaTeX">$^3$</tex-math><alternatives> <inline-graphic xlink:href="zhang-ieq4-2771425.gif"/></alternatives></inline-formula>, MP<inline-formula> <tex-math notation="LaTeX">$^3$</tex-math><alternatives><inline-graphic xlink:href="zhang-ieq5-2771425.gif"/> </alternatives></inline-formula>, and CRP, respectively), and outperforms the baseline algorithms.