Date Added: Aug 2011
The availability of a large variety of sensor devices allows wireless sensor networks to be exploited in different application fields. Applications which rely on 24x7 (continuous) monitoring are required for environmental monitoring, precision agriculture, health-care, security surveillance, and national defense. Wireless sensor network has emerged as a major, inter-disciplinary research area. It is usually expected to operate for an extended period of time but the fundamental constraint on it is the limited energy supplies on sensors. Traditionally, a wireless sensor network consists of a fixed sink (or a base station) and hundreds of thousands of tiny sensors powered by batteries.