Design and Analysis of a Propagation Delay Tolerant ALOHA Protocol for Underwater Networks

Joon Ahn, Affan Syed, Bhaskar Krishnamachari, and John Heidemann
USC/Information Sciences Institute

Abstract

Acoustic underwater wireless sensor networks (UWSN) have recently gained attention as a topic of research. Such networks are characterized by increased uncertainty in medium access due not only to when data is sent, but also due to significantly different propagation latencies from spatially diverse transmitters--together, we call these space-time uncertainty. We find that the throughput of slotted ALOHA degrades to pure ALOHA in such an environment with varying delay. We therefore propose handling this spatial uncertainty by adding guard times to slotted ALOHA, forming Propagation Delay Tolerant (PDT-)ALOHA. We show that PDT-ALOHA increases throughput by 17-100% compared to simple slotted ALOHA in underwater settings. We analyze the protocol's performance both mathematically and via extensive simulations. We find that the throughput capacity decreases as the maximum propagation delay increases, and identify protocol parameter values that realize optimal throughput. Our results suggest that shorter hops improve throughput in UWSNs.

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Reference

Ahn10b

Joon Ahn, Affan Syed, Bhaskar Krishnamachari, and John Heidemann. Design and Analysis of a Propagation Delay Tolerant ALOHA Protocol for Underwater Networks. Technical Report ISI-TR-2010-668, USC/Information Sciences Institute, September, 2010. This technical report is a draft preprint of a paper to appear in Elsevier Ad Hoc Networks Journal. Please access and cite that version if possible. <http://www.isi.edu/~johnh/PAPERS/Ahn10b.html>.

@techreport{Ahn10b,
	author = "Joon Ahn and Affan Syed and Bhaskar
 Krishnamachari and John Heidemann",
	title = "Design and Analysis of a Propagation Delay Tolerant
    ALOHA Protocol for Underwater Networks",
	institution = "USC/Information Sciences Institute",
	year = "2010",
	number = "ISI-TR-2010-668",
	month = "September",
	note = "This technical report is a draft preprint of a
                  paper to appear in Elsevier Ad Hoc Networks Journal.
		Please access and cite that version if possible.",
	keywords = "aloha, underwater networks, analysis, simulation",
	url = "http://www.isi.edu/~johnh/PAPERS/Ahn10b.html",
	pdfurl = "http://www.isi.edu/~johnh/PAPERS/Ahn10b.pdf",
	copyrightholder = "authors",
}

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