Date Added: Sep 2012
Wireless sensor network is special types of ad-hoc network which contain very tiny nodes in size and their cost is also not very high. They are deployed in any geographical region in a random fashion. During the process of data sensing, data gathering and data transmission, the charge of the power unit associated with any node gets low, after certain time, i.e., each node has its life time. The life time of nodes directly affects the life time of the sensor network. As each node is very low in cost, it is unnecessary and difficult too, to recharge them once their energies are exhausted.