Date Added: Nov 2012
Wireless sensor networks are designed to be deployed in the physical environment to monitor a wide variety of real-world phenomena. These networks are composed of various small sensor nodes deposited in a given area. In these networks, the battery replacement is unfeasible and thus the energy is a critical resource that must be considered by all protocols. In order to reduce the energy consumption, protocols for MAC layer use techniques that turn off the radio of sensor nodes. However, in many protocols, all sensor nodes operate on the same static schedule in which they wake up periodically at the same fixed interval of time. This scheme might not be appropriate in dynamic scenarios in which the traffic varies.