Distributed Sensor Nodes Charged by Mobile Charger with Directional Antenna and by Energy Trading for Balancing

Abstract

Provision of energy to wireless sensor networks is crucial for their sustainable operation. Sensor nodes are typically equipped with batteries as their operating energy sources. However, when the sensor nodes are sited in almost inaccessible locations, replacing their batteries incurs high maintenance cost. Under such conditions, wireless charging of sensor nodes by a mobile charger with an antenna can be an efficient solution. When charging distributed sensor nodes, a directional antenna, rather than an omnidirectional antenna, is more energy-efficient because of smaller proportion of off-target radiation. In addition, for densely distributed sensor nodes, it can be more effective for some undercharged sensor nodes to harvest energy from neighboring overcharged sensor nodes than from the remote mobile charger, because this reduces the pathloss of charging signal due to smaller distances. In this paper, we propose a hybrid charging scheme that combines charging by a mobile charger with a directional antenna, and energy trading, e.g., transferring and harvesting, between neighboring sensor nodes. The proposed scheme is compared with other charging scheme. Simulations demonstrate that the hybrid charging scheme with a directional antenna achieves a significant reduction in the total charging time required for all sensor nodes to reach a target energy level.

Optimizing Charging Efficiency and Maintaining Sensor Network Perpetually in Mobile Directional Charging

“…However, a directional antenna provides significant enhancement over the omnidirectional antenna in terms of direction beam [21]. Moreover, when charging distributed sensor nodes, a directional antenna, rather than an omnidirectional antenna, is more energy-efficient because of the smaller proportion of off-target radiation [22]. Inspired by the research issues in the literature on mobile omnidirectional wireless charging scheduling [13,14,15,16,17], and directional charger’s deployment [9,18,19,20], we propose the directional wireless charging optimization problem in this paper.…”

Evolutionary Beamforming Optimization for Radio Frequency Charging in Wireless Rechargeable Sensor Networks

“…RF chargers can be applied to simultaneously charge many devices equipped with RF energy harvesters to make device sustainable. Typical devices to be charged include wearable and implanted healthcare gadgets in wireless body area networks (WBANs) [ 4 ], and sensor nodes in wireless rechargeable sensor networks (WRSNs) [ 5 , 6 , 7 , 8 , 9 , 10 ].…”

“…Typical energy sources include solar power, thermal power, wind power, and RF power. Several studies [ 5 , 6 , 7 , 8 , 9 , 10 ] assume that a WRSN sensor node is equipped with an RF energy harvester to harvest the energy emitted by RF chargers. The studies in [ 5 , 6 , 7 ] focus on the deployment optimization of RF chargers equipped with directional antennas.…”

“…The studies in [ 5 , 6 , 7 ] focus on the deployment optimization of RF chargers equipped with directional antennas. The studies in [ 8 , 9 , 10 ] investigate how to minimize the total time to charge all sensor nodes with mobile chargers equipped with directional or omni-directional antennas.…”

“…On the contrary, the antenna array can be used to swiftly adjust the effective charging region by the beamforming technology without moving the antenna. The existing research results [ 5 , 6 , 7 , 8 , 9 , 10 ] assume RF chargers are attached with either directional antennas or omnidirectional antennas. To the best of our knowledge, no research has yet investigated applying antenna arrays to RF chargers for charging WRSN sensor nodes.…”