A survey on wireless sensor network databases

In recent years, the use of wireless sensors has increased drastically in most fields. Wireless Sensor Networks (WSNs) have attracted the interest of industries and they have been used in several application areas (military, health, transportation, agriculture). WSNs are ad-hoc networks, composed of sensor nodes, which are deployed in an area of interest, in order to monitor and to return information requested by users. Sensor data is transmitted to users over a central station, named base station. Data collection becomes more difficult when the number of sensors increases. Since about a decade, intensive research has started in order to deal with these problems. Many researchers suggested to structure the sensor data in the form of a database and reduce the number of communications and energy consumption in the network. They have often considered the network as a large database and the sensor node as a virtual table. In this article, the existing sensor database approaches in WSNs are studied. Firstly, we will provide the definition of sensor databases, then we will present their architecture and their characteristics. Thereafter, we will present and compare existing sensor database systems. Finally, we will conclude this paper with a discussion of some research issues in the field of sensor databases.