Wireless Sensor Networks (WSN) consists of a large number of small, batterypowered, inexpensive and wireless sensors which send their data wirelessly. More specically, a WSN consists of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. Typically, data packets are generated by each node and are sent to a Base Station (BS) or a sink. Here the data is aggregated and forwarded to the user. Figure shows the basic architecture of a WSN using sensors to monitor the physical conditions. From the above a WSN has peculiarities such as limited processing power, limited memory, low power, low rate, limited range radio and battery driven sensor nodes.
WSNs are widely used in various kinds of applications, such as military surveillance applications, health applications, and environmental applications . For example, in military applications WSNs can be an integral part of military command, control, communications, computing, intelligence, surveillance, reconnaissance and targeting systems. Besides, these can also be used for target-detection, for monitoring forces and equipment, for detecting nuclear, biological or chemical attacks and for the surveillance of battleelds. Another example is using WSN for health applications, which are providing interfaces for the disabled, integrated patient monitoring, diagnostics and hospital drugs administration. WSN are also used in environmental monitoring where WSN can be used for tracking the movements of the small animals, detecting forest fire and flood detection and environmental monitoring in marine and soil environments. One of the applications is the use of WSN in homes such as home automation. In recent years WSNs are widely used in more elds such as wireless factory, smart (intelligent) buildings and implantable medical sensors which are used for medical applications