Date Added: Apr 2013
A Wireless Sensor Network (WSN) consists of a large number of sensor nodes deployed over a geographical area for monitoring physical phenomena like temperature, humidity, vibrations, seismic events, and so on. WSNs have broad applications like environment monitoring, target tracking and surveillance. The unique characteristics of WSNs such as limited bandwidth, computing capacity, data delivery delay and severe energy constraints make their design more challenging. A critical issue in wireless sensor networks is the limited availability of energy and many researches are carried out to for optimizing energy. The best way to improve the network lifetime is by developing energy efficient protocols and this paper provides a survey on different energy efficient protocols for improving the lifetime of the wireless sensor node.