Cluster–based Wake–up Control for Top–k Query in Wireless Sensor Networks

This paper focuses on top–k query in cluster–based wireless sensor networks (WSNs) employing wake–up receivers, which aims to grasp the information on top–k data efficiently in terms of energy consumed by sensor nodes. As a wake–up control for top–k query, countdown content–based wake–up (CDCoWu) has been proposed. CDCoWU selectively activates sensor nodes storing data belonging to top–k dataset, and its superiority to a conventional identity–based wake–up (IDWu) has been confirmed for a single–hop network accommodating a large number of nodes. In this paper, we extend these wake–up control to a cluster–based WSN, a common network structure of WSN. The cluster–based WSN contains nodes called cluster heads that relay wake–up signals and data for their cluster members. The proposed cluster–based wake–up control conducts activations and data collections of different clusters sequentially while the results of data collections at a cluster are exploited for reducing unnecessary data transmissions at the other clusters. We also introduce a hybrid mechanism of wake–up control, where a wake–up control employed at each cluster is selected between CDCoWu and IDWu according to its number of cluster members. Our simulation results show that the proposed hybrid wake–up control achieves smaller energy consumption and data collection delay than the control solely employing CDCoWu or IDWu.