Hybrid charging scheduling schemes for three-dimensional underwater wireless rechargeable sensor networks

Recent breakthrough in wireless power transfer provides a new paradigm for enabling wireless energy replenishment for wireless rechargeable sensor networks, especially in the underwater environment. In this paper, we first propose the concept of UWRSNs (underwater wireless rechargeable sensor networks) and then develop a series of 3D charging schemes for enhancing charging efficiency, using underwater charging robot mules in three-dimensional charging scenarios. Through constructing the architecture of UWRSNs, we develop a basic charging scheme SCS (Shortest-path Charging Scheme), which minimizes the traveling cost for the charging mules in the 3D underwater environment. Then, ECS (Emergency Charging Scheme) is proposed, which concentrates on serving emergency nodes. After that, a charging algorithm that combines ECS and SCS to collaboratively solve the charging problem, namely, HOCS (Hybrid Optimal Charging Scheme) is developed. At last, experimental simulations are conducted to show the outperformed merits of the proposed scheme. Experimental results demonstrate that our schemes not only save energy and time, but also ensure effective utilization of resources.