I. Introduction
A wireless sensor network (WSN) consists of an array of sensors, of diverse types, interconnected by a wireless communication network. Sensor data is shared between these sensor nodes and used as input to a distributed estimation system whose function is to extract the relevant information from the available data. Fundamental design objectives of sensor networks include reliability, accuracy, effectiveness, flexibility. Each node has one or more sensing unit, an embedded processor, and low-power radios. The nodes act as information sources, sensing and collecting data samples. They perform routing functions, creating multi-hop wireless network fabric that conveys data samples to other sensor nodes. Nodes can also act as information sinks, receiving dynamic configuration information from other nodes or external entities. The rapid deployment, self organization and fault tolerance characteristics for WSN make them promising for a number of military and civilian applications.[1]