Charging wireless rechargeable sensor networks with directional antenna exploiting clustering and energy trading

Abstract

Providing energy to wireless sensor networks is crucial to their sustainable operation. Sensor nodes are typically equipped with batteries as their operating energy source. 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 omni-directional antenna, is more energy-efficient because of smaller proportion of off-target radiation. Also, with 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 it reduces the pathloss of charging signal due to smaller distances. In this study, we propose a hybrid charging scheme that combines charging by a mobile charger with a directional and omnidirectional antenna, and energy trading, e.g., transferring and harvesting, between neighboring sensor nodes. The proposed scheme is compared with other charging schemes. Simulations demonstrate that the proposed hybrid charging scheme achieves a significant reduction in the total charging time required for all sensor nodes to reach a target energy level.