1.2 Problems in Wireless Sensor Networks
In recent years, the Wireless Sensor Network (WSN) [4] has received signifi-
cant interest from the research community. A sensor network usually consists
of hundreds or thousands of tiny and inexpensive sensor nodes, which are deployed
on the ground, in the air, in vehicles, on bodies, under water and inside
buildings without any sensing infrastructure a priori, providing functions of
data sensing, information processing and communication. Because of its spatial
coverage and multiplicity in sensing aspect and modality, a sensor network
can be used for many military and civil applications, such as environment or
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habitat monitoring, target surveillance and object tracking, tra?±c monitoring
and tra?±c control, and so on [5].
A WSN can be treated as a distributed database system. In such a system
each sensor node operates autonomously with no central node of control. It
can be a data source (producing data) as well as a data sink (consuming data).
Each node will update sensed data to the networks in an e?±cient way (write
operation) so that interested querying nodes are able to get the current copy
of the new data (read operation) as soon as possible. Each of these operations
is based on the node??™s local information.
Several challenges are in front of us for the design and implementation of
such a distributed information system for resource constrained WSNs.
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