Mobile Intelligence

24.1 INTRODUCTION

Wireless sensor networks (WSNs) have a wide range of potential applications, including environment monitoring, military, smart house, and remote medical system. A WSN comprises a sink node and an extremely large of sensor node that communicates with each other in order to perform a broader sensing task. Sensor node is a tiny device with capabilities of sensing, data processing and storing, and communication but is constraint in energy. The sink node is a control center that typically initiates a request demand for collecting interested information. Linked by a wireless medium, the sensor nodes perform distributed sensing tasks and store particular sensing information for query. The WSN can be virtually treated as a database system that provides sensing and data-storing functions for all active sensor nodes and provides query function for the sink nodes. One critical problem in sensor networks is how to make the effective use of the vast amount of data, providing sink and sensor nodes with efficient data retrieving and storing, respectively. Previous solutions to this problem can be classified into three categories: local storage (LS), external storage (ES), and data-centric storage (DCS).

In local storage mechanism, the data are stored in sensor nodes local memory when the event is detected. Since the sink node does not know which sensor nodes store the interested data, it typically executes the blind flooding over the whole WSN for sending a query packet that ...