Avoiding radiation of on-demand multi-node energy charging with multiple mobile chargers

Abstract Wireless rechargeable sensor networks (WRSN) exploit wireless energy transfer techniques to replenish sensor batteries using chargers. Compared to non-rechargeable networks, WRSNs offer controllable and predictable energy replenishment and prolong the network lifetime. While previous mobile charging protocols in WRSNs consider multi-node energy transfer or the use of several chargers, in this work, we propose combining the two approaches. Our solution leverages simultaneous energy transfer to multiple nodes, with the aim of maximizing the number of nodes that are charged at each stop to reduce the charging delay. Moreover, it considers multiple chargers to serve more requesting nodes, which is expected to limit the number of node failures. Furthermore, we guarantee that there is no aggregated electromagnetic radiation (EMR), which can occur when two nearby chargers are simultaneously charging. This has not yet been considered in a mobile environment. To address these challenges, we introduce a new clustering algorithm to group demanding nodes, and we compute charging tours by iteratively solving a Traveling Salesman Problem with Multiple Time Windows problem (TSPMTW). The simulation results demonstrate that our approach reduces node failures in dynamic networks.