CMAC

Abstract

Low duty cycle operation is critical to conserve energy in wireless sensor networks. Traditional wake-up scheduling approaches either require periodic synchronization messages or incur high packet delivery latency due to the lack of any synchronization. To simultaneously achieve the seemingly contradictory goals of energy efficiency and low latency, the design of a new low duty-cycle MAC layer protocol called Convergent MAC (CMAC) is presented. CMAC avoids synchronization overhead while supporting low latency. By using zero communication when there is no traffic, CMAC allows sensor nodes to operate at very low duty cycles. When carrying traffic, CMAC first uses anycast to wake up forwarding nodes, and then converges gradually from route-suboptimal anycast with unsynchronized duty cycling to route-optimal unicast with synchronized scheduling. To validate our design and provide a usable module for the research community, CMAC has been implemented in TinyOS and evaluated on the Kansei testbed consisting of 105 XSM nodes. The results show that CMAC at 1% duty cycle significantly outperforms BMAC at 1% in terms of latency, throughput and energy efficiency. The performance of CMAC is also compared with other protocols using simulations, in which the results show for 1% and lower duty cycles, CMAC exhibits similar throughput and latency as CSMA/CA using much less energy, and outperforms SMAC, DMAC and GeRaF in almost all aspects.