On the Interaction of Charging-Aware Mobility and Wireless Communications

Abstract

Today's mobile battery-powered communication devices require that users access chargers via wired and, recently, wireless recharging facilities. For a device departing from a location with a given energy ``budget'', a plausible strategy is to seek a charger location once the energy is exhausted. We present a set of charging-aware mobility models that capture the paths followed by the nodes with depleted energy seeking, possibly via a detour, to reach a charger. Firstly, for a 1-dimensional space, we derive the location-dependent mobile node density distribution, using it to express the location-dependent congestion of a wireless network whose capacity is used by the mobile nodes. The boundaries, and the relative placement of the charger, create intriguing discontinuities in the probability density function of the nodes across space. We find that chargers are not always ``hotspots'' in terms of node density, and that the energy budget of the nodes determines the hotspot. For a 2-dimensional space, the analysis shows asymmetrically spiked node density in the locality of the charger, which, counterintuitively, is encircled by relative dips in node density. We extend the probability density function derived for one-charger deployment to approximate that under multiple chargers, observing high accuracy for sparse deployment. We also study the performance of charging-aware mobiles that conduct ad hoc communication in a grid. The results show that the recharging behavior can improve energy supply and communication opportunities. The simulation further demonstrates the advantages and implications of deploying multiple distributed chargers.