Enable sustainable sensor networks with non-contact charging: efficient deployment of energy hubs

The lifetime of a wireless sensor network WSN imposes a limitation on its practical usage when sensor nodes are battery powered. Besides energy-harvesting, non-contact recharging of node battery, such as wireless charging and light-reflection charging, is a promising technique to obtain sustainable functioning for WSNs. To achieve that, the current research along this direction has mainly suggested two kinds of methods: by traversing all sensor nodes using mobile chargers, or by deploying fixed chargers in the network. For both methods, negligible charging time is often assumed. In this paper, we consider to achieve non-contact recharging of sensor nodes using fixed chargers, also called energy hubs. In particular, we consider non-negligible charging time and propose a heuristic method to find the minimum number of energy hubs to be deployed in the network such that all sensor nodes are guaranteed to stay operational. Extensive simulations are performed to verify the effectiveness of the proposed solution.