Ultra-low duty cycle MAC with scheduled channel polling

Abstract

Energy is a critical resource in sensor networks. MAC protocols such as S-MAC and T-MAC coordinate sleep schedules to reduce energy consumption. Recently, lowpower listening (LPL) approaches such as WiseMAC and B-MAC exploit very brief polling of channel activity combined with long preambles before each transmission, saving energy particularly during low network utilization. Synchronization cost, either explicitly in scheduling, or implicitly in long preambles, limits all these protocols to duty cycles of 1-2%. We demonstrate that ultra-low duty cycles of 0.1% and below are possible with a new MAC protocol called scheduled channel polling (SCP). This work prompts three new contributions: First, we establish optimal configurations for both LPL and SCP under fixed conditions, developing a lower bound of energy consumption. Under these conditions, SCP can extend lifetime of a network by a factor of 3-6 times over LPL. Second, SCP is designed to adapt well to variable traffic. LPL is optimized for known, periodic traffic, and long preambles become very costly when traffic varies. In one experiment, SCP reduces energy consumption by a factor of 10 under bursty traffic. We also show how SCP adapts to heavy traffic and streams data in multi-hop networks, reducing latency by 85% and energy by 95% at 9 hops. Finally, we show that SCP can operate effectively on recent hardware such as 802.15.4 radios. In fact, power consumption of SCP decreases with faster radios, but that of LPL increases.

Sleep in the Dins: Insomnia therapy for duty-cycled sensor networks

“…In synchronous duty-cycling protocols [3] [4] [5], the sender and receiver are synchronized, which enables the sender transmit packets right after the receiver wakes up. Synchronous dutycycling protocols require time synchronization [6] with extra overhead and hence are not flexible and efficient [4].…”

Y-MAC: An Energy-Efficient Multi-channel MAC Protocol for Dense Wireless Sensor Networks

“…To address this issue, Funneling-MAC [10] and Z-MAC [11] propose hybrid approaches, combining the advantages of contention-based protocols and time-slotted protocols. SCP-MAC [12] suggests not only synchronous channel polling to reduce energy wastage, but also a multi-hop streaming scheme to handle bursty traffic towards base stations.…”

Energy Efficient Network Structure for Synchronous Preamble Sampling in Wireless Sensor Networks

“…In Synchronous Preamble Sampling, nodes coordinate their wake-up instants to have a common schedule-they sleep during the same interval to save energy and then wake up to exchange data frames [4]. To maintain a common schedule, each node needs to periodically broadcast a SYNC control frame to make up for clock drifts.…”

“…Scheduled Channel Polling (SCP) [4] has shown that explicit transmissions of SYNC frames do not reduce the overall energy savings, because the benefits of using short preambles lead to more energy savings in the end. SCP maintains a common schedule throughout the network to save broadcast communications the need of using long preambles.…”