SA-RI-MAC: Sender-Assisted Receiver-Initiated Asynchronous Duty Cycle MAC Protocol for Dynamic Traffic Loads in Wireless Sensor Networks

Duty cycling is an efficient mechanism to conserve energy in wireless sensor networks. Several existing duty cycling techniques have been proposed to conserve energy, but they are not able to handle the contention under dynamic traffic loads. In this paper we propose a protocol called Sender-Assisted-Receiver-Initiated MAC (SA-RI-MAC) which solves this problem without sacrificing the energy efficiency. SA-RI-MAC employs the receiver initiated transmissions mechanism of RI-MAC with a sender assisted approach to handle the contention at the receiver. Senders tend to cooperate with each other to resolve the contention dynamically based on the contention level at the receiver. A further improvement is achieved by prioritizing the sender transmissions which has been starved long for the channel occupancy. Our simulation results in ns-2 show that SA-RI-MAC achieves significant improvement in conserving energy over RI-MAC. It can handle traffic contention much more efficiently than RI-MAC; thus improving end to end delivery ratio with a reduction in the latency. Under light traffic load, the performance of SA-RI-MAC is comparable with RI-MAC in terms of end to end delivery ratio, latency and energy efficiency.