Ultra-Low Duty Cycle MAC with Scheduled Channel Polling

Wei Ye and John Heidemann
USC/Information Sciences Institute

Abstract

Radio is a major source of energy consumption in sensor networks. MAC protocols such as S-MAC and T-MAC coordinate sleep schedules to reduce energy consumption. Recently, low-power listening (LPL) approaches such as WiseMAC and B-MAC exploit very inexpensive polling of channel activity combined with long preambles before each transmission, reducing energy consumption particularly during low network utilization. Synchronization cost, either explicitly in scheduling, or implicitly in long preambles, limit 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 (SCP-MAC) by optimally combining scheduled communication with \emphchannel polling. This combination prompts three new contributions: First, we establish optimal configurations for both LPL and SCP under fixed conditions, developing a lower bound of energy consumption. We show that scheduling can typically extend lifetime of a network by a factor of 3-6 times over LPL. Second, we demonstrate that SCP works well even when traffic load varies. While LPL is optimized for known, periodic traffic, long preambles become very costly when traffic varies. In one experiment, SCP reduces energy consumption by a factor of 10 when traffic is bursty. We also show how it can adapt to heavy traffic and stream 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, that of LPL-based approaches increases. To our knowledge, SCP is the first MAC that exploits channel polling on this hardware.

Availability

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Reference

Ye05a

Wei Ye and John Heidemann. Ultra-Low Duty Cycle MAC with Scheduled Channel Polling. Technical Report ISI-TR-2005-604b, USC/Information Sciences Institute, July, 2005. <http://www.isi.edu/~johnh/PAPERS/Ye05a.html>.

@techreport{Ye05a,
	author = "Wei Ye and John Heidemann",
	title = "Ultra-Low Duty Cycle MAC with Scheduled
            Channel Polling",
	institution = "USC/Information Sciences Institute",
	year = "2005",
	number = "ISI-TR-2005-604b",
	month = "July",
	notes = "Originally released July 2005 (available at \url{http:///www.isi.edu/~johnh/PAPERS/Ye05a_200607.pdf}, updated April 2006",
	keywords = "s-mac, scp-mac, b-mac, lpl",
	url = "http://www.isi.edu/~johnh/PAPERS/Ye05a.html",
	pdfurl = "http://www.isi.edu/~johnh/PAPERS/Ye05a.pdf",
	myorganization = "USC/Information Sciences Institute",
	copyrightholder = "authors",
}

Updates

This technical report was originally released July 2005, and then updated April 2006. The original version is available here and on request.

Copyright

This paper is copyright © 2005 by its authors. Permission to make digital or hard copies of part or all of this work for personal use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that new copies bear this notice and the full citation on the first page. Abstracting with credit is permitted.

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