Date Added: Sep 2012
In recent years a lot of work has been done on Wireless Sensor Network (WSN) as it find its application in many applications including environmental monitoring and military field surveillance. In these applications tiny sensor nodes are deployed across the application regions. Data gathered by the sensor nodes are periodically collected by the base stations. As the nodes are deployed and left unattended for a long time it becomes quite difficult to recharge the node batteries. Several WSN applications require only an aggregate value to be reported to the base station. In this case sensors in different regions of the field can collaborate to aggregate their data and provide more accurate reports about their local regions.