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Tones for Real: Managing Multipath in Underwater Acoustic Wakeup

Affan A. Syed and John Heidemann
USC/Information Sciences Institute

Abstract

The principles of sensor networks--low-power, wireless, in-situ sensing with many inexpensive sensors--are only recently penetrating into underwater research. Acoustic communication is best suited for underwater communication, since other methods (optical and radio) attenuate very quickly. Yet acoustic propagation is five orders-of-magnitude slower than RF, so propagation times stretch to hundreds of milliseconds. A new generation of underwater acoustic modems have added low-power wakeup tones that combat the energy consumption acoustic modems would waste on idle listening. Recently, these tones have been used as an integral part of application layer and MAC protocols. While all wireless data-networks suffer from multipath interference of received data, in this paper, we show that due to large acoustic propagation delay tone echoes cause a unique interference, tone self-multipath, for tone-based protocols. To address this interference we introduce \emphSelf-Reflection Tone Learning (SRTL), a novel approach where nodes use Bayesian techniques to discriminate self-reflections from noise and communication from other nodes. We present detailed experiments using an acoustic modem in two physical environments to show that SRTL's knowledge corresponds to physical-world predictions, that it can cope with reasonable levels of noise, and that it can track a changing multi-path environment. Simulations confirm that these real-world experiments generalize over a wide range of conditions.

Availability

This paper is available in several formats: abstract web page with pointers and cites, PDF, paper copies can be obtained by mail to the authors. Copyright terms for this paper appear below.

Reference

Syed09b: Affan A. Syed and John Heidemann. Tones for Real: Managing Multipath in Underwater Acoustic Wakeup. Technical Report ISI-TR-2009-659, USC/Information Sciences Institute, April, 2009. <http://www.isi.edu/~johnh/PAPERS/Syed09b.html>.

@techreport{Syed09b,
	author = "Affan A. Syed and John Heidemann",
	title = "Tones for Real: Managing Multipath in Underwater Acoustic Wakeup",
	institution = "USC/Information Sciences Institute",
	year = "2009",
	number = "ISI-TR-2009-659",
	month = "April",
	keywords = "underwater MAC, self-reflection",
	myorganization = "USC/Information Sciences Institute",
	copyrightholder = "authors",
	url = "http://www.isi.edu/~johnh/PAPERS/Syed09b.html",
	pdfurl = "http://www.isi.edu/~johnh/PAPERS/Syed09b.pdf",
}

Copyright

This paper is copyright © 2009 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.

To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission of the authors.