A hybrid approach using mobile element and hierarchical clustering for data collection in WSNs

How to minimize the energy dissipation and extend the lifetime of wireless sensor networks (WSNs) is still an active research topic nowadays. Hierarchical routing based on node clustering is an effective method, while using mobile elements (MEs) to gather data can prevent huge energy consumption of the sensors from long-distance transmission. Considering that both methods have pros and cons, this paper presents a hybrid approach, called Node Density based Clustering and Mobile Collection (NDCM), to combine the hierarchical routing and ME data collection in WSNs. A number of Cluster Heads (CHs) first gather information from the cluster members and then the ME visits these CHs to collect data. A new CH selection scheme based on the node density is proposed. Thus, a node at the center of an area where nodes are densely deployed is more likely to be a CH, which can improve the efficiency of both intra-cluster routing and ME data collection. We also introduce a simple Random Clustering and Mobile Collection (RCM) scheme according to which a number of CHs are selected randomly throughout the network. In addition, the nodes which are covered by the radio range of the ME, called Virtual Heads (VHs), can also send/relay packets directly to the ME. The different mobility schemes are compared through extensive simulations and the results show that the proposed hybrid NDCM scheme leads to remarkable improvement in network lifetime and convenient trade off between the network energy saving and packet latency.