Charging Distributed Sensor Nodes Exploiting Clustering and Energy Trading

One of the main issues on wireless sensor networks is the sustainability of network operation. Sensor nodes typically acquire their energy from batteries. However, they are often deployed in hard-to-reach places, so replacing their batteries incurs substantial increase in operational cost. Therefore, energy harvesting by sensor nodes can be more cost-efficient for sustainable network operation. The harvested energy should be transmitted from a single or multiple chargers. This paper deals with a charging scheme for distributed sensors nodes. The charging scheme consists of two stages: charging by a mobile charger and charging undercharged sensor nodes by overcharged ones. The second stage is considered energy trading between seller nodes and buyer nodes. For charging in the first stage, all the sensor nodes are classified into clusters. To this end, the concept of inclusion circle is devised. By the clustering based on the inclusion circle, a sensor node, which is located around the center of grouped sensor nodes is highly likely selected as a cluster head. Charging path of the mobile charger in the first stage is determined according to the locations of cluster heads. The energy trading in the second stage is to achieve energy balancing of the sensor nodes. When the proposed two-stage charging is finished, every sensor node is charged over the target level. The proposed scheme is compared with the existing charging schemes. As a result, the total amount of charging energy and the total charging time can be significantly reduced.