RF-Based Charger Placement for Duty Cycle Guarantee in Battery-Free Sensor Networks

TL;DR

This paper addresses the challenge of optimally placing RF-based chargers in battery-free sensor networks to ensure continuous operation by maintaining a specific duty cycle, using a new recharge model and optimization techniques.

Contribution

It introduces a novel wireless recharge model and formulates the charger placement as a constrained optimization problem, proposing heuristics and a PSO-based approach for effective solutions.

Findings

PSO-based approach reduces the number of chargers needed

Proposed heuristics outperform greedy methods in simulations

Effective energy harvesting ensures duty cycle guarantees

Abstract

Battery-free sensor networks have emerged as a promising solution to conquer the lifetime limitation of battery-powered systems. In this paper, we study a sensor network built from battery-free sensor nodes which harvest energy from radio frequency (RF) signals transmitted by RF-based chargers, e.g., radio frequency identification (RFID) readers. Due to the insufficiency of harvested energy, the sensor nodes have to work in duty cycles to harvest enough energy before turning active and performing tasks. One fundamental issue in this kind of network design is how to deploy the chargers to ensure that the battery-free nodes can maintain a designated duty cycle for continuous operation. Based on a new wireless recharge model, we formulate the charger placement problem for node's duty cycle guarantee as a constrained optimization problem. We develop both greedy and efficient heuristics for solving the problem and validate our solutions through extensive simulations. The simulation results show that the proposed particle swarm optimization (PSO)-based divide-and-conquer approach can effectively reduce the number of chargers compared with the greedy approach.