Minimum Nodes Deployment for Mixed Energy Replenishment in Rechargeable WSNs

Energy harvesting technology has been applied to power nodes in a wireless sensor networks (WSNs). However, it suffers from the dynamic nature of the ambient energy. Wireless charging, on the contrary, offers an additional choice to charge the sensor nodes (SNs) with a mobile charger (MC) which is often implemented to move within the network. Nevertheless, the energy spent on moving among sensors accounts for a considerable proportion of the whole energy the MC can take. To this end, we consider combining these two sources of energy to carry out the energy neutral operation for the WSNs. In this paper, we formulate the problem of minimizing the number of nodes for perpetual coverage of targets under the constraint of the energy capacity of a MC and the distribution of the energy harvesting rate across the monitoring field which generates great difficulty. We designed two approximation algorithms to tackle this problem. We conduct extensive simulations to evaluate the performance of our proposed algorithms. The results showed performance of these two algorithms with respect to impact of different parameters.