Abstract
A wireless sensor network consisting of a large number of battery-powered nodes have been witnessed a variety of applications, ranging from military surveillance to health care to environmental monitoring. In a wireless sensor network, the technique of periodic sleep and wake up is usually utilized to save energy and prolong lifetime. However, existing relevant work is not suitable for all kinds of network environments and usually sacrifices latency for energy savings. The reason is that it is hard to decide a perfect duty cycle for nodes to follow since the sensing events or the traffic is not happening regularly and thus is unknown beforehand. In cases when applications have constraint on the end-to-end delay of the data packets, it is even harder to decide a perfect duty cycle for nodes to preserve as much energy as possible, while maintaining the delay constraint. To this end, we propose CBA-EX MAC, an adaptive energy-efficient MAC protocol based on economics and statistics. CBA-MAC achieves significant energy savings while maintaining delay constraint. The key is to change the schedule and duty cycle of nodes dynamically. In CBA-EX MAC, each node takes both network traffic and delay constraint into consideration to get a suitable schedule for nodes to preserve as much energy while maintaining the delay constraint. In addition, each node in CBA-MAC can change its duty cycle to reduce more energy consumption dynamically. The results of our simulation confirm that CBA-MAC can reduce more energy consumption comparing to other existing adaptive or fixed duty cycle MAC protocols, while maintaining different kinds of delay constraint.