Asym-MAC: A MAC Protocol for Low-Power Duty-Cycled Wireless Sensor Networks with Asymmetric Links

Duty-cycling is a primary technique significantly improving the energy efficiency of Wireless Sensor Networks (WSNs). Thus, a large number of MAC protocols have been developed for duty-cycled WSNs. Especially, recently proposed receiver-initiated MAC protocols are well suited for extremely low duty-cycled WSNs. However, as it is shown in this paper, they perform poorly when highly asymmetric links are present. In this paper, a hybrid MAC protocol called Asym-MAC is proposed which takes advantage of both receiver-initiated and sender-initiated MAC protocols to combat performance degradation due to asymmetric links. Experimental results demonstrate that Asym-MAC has up to 2.8X higher packet reception ratio and up to 66.7% smaller packet transmission delay compared with A-MAC, the state-of-the-art receiver-initiated MAC protocol.