W-MAC: Supporting Ultra Low Duty Cycle in Wireless Sensor Networks

The duty cycle of a wireless sensor node is a key factor that determines the life time of a wireless sensor network. In general, sensor medium access control protocols reduce the duty cycle to achieve longer lifetime. However, we found out that their performance improvements substantially decrease under extremely low duty cycles (<0.1%). Our proposed W-MAC protocol targets achieving low energy consumption under extremely low duty cycle as well as low duty cycle (>0.1%). It is with estimation of the relative clock speed between the sender and the receiver, and uses it to minimize energy consumption. It saves energy significantly well compared to the existing schemes in an order of ten times, and the performance gap increases with lowering the duty cycle.