Efficient charging schedules in a rechargeable wireless sensor network with multiple chargers

In a wireless sensor network (WSN) when a node’s battery drains out it becomes a dead node. Due to the recent advancement of mobile power transfer technology, it is feasible to charge the nodes of WSN by single or multiple mobile chargers (MC) of finite capacity thereby extending the network lifetime. It introduces a new paradigm of WSN namely rechargeable wireless sensor networks (RWSN), where the energy of nodes lying below a predefined threshold value is replenished to full capacity by the MCs. The determination of an MC charging schedule resembles a constrained traveling salesman problem (TSP) which is NP-complete. So here we propose for RWSN with multiple MCs two recharging heuristics MEWLST_C and MEWLST_NC for clustered and non-clustered environments respectively based on the concept of the latest start time (lst) to charge a requesting node. A node is chargeable when an MC reaches before it dies out and charges it to full capacity. The MC should have sufficient energy to return to the base station (BS) after charging the node, a condition called MC’s reachability. Our proposals ensure an accepted request is chargeable and the corresponding MC satisfies the reachability criteria. Extensive simulation studies reveal that our method maximizes overall node survival ratio ( \(\delta\) $\delta$ ), while maintaining the almost same or moderately improved Moving Energy Ratio of the MCs ( \(\gamma\) $\gamma$ ) compared with the recent state of the art.