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Evaluating the Importance of Concurrent Packet Communication in Wireless Networks

Dongjin Son, Bhaskar Krishnamachari, and John Heidemann
USC/Information Sciences Institute

Abstract

Nearly all wireless media-access (MAC) protocols are designed today with the very conservative assumption that concurrent transmissions should be prevented, because sender-receiver pairs within radio range sending on the same channel will corrupt each other's communication. While recent work has suggested that channel capture effects can be significant in reality, this paper presents the first systematic study to quantify the impact of these effects on the ability to have concurrent communications among two sender-receiver pairs that are within range of each other. We first derive a simple decision rule to determine when such concurrent communication is possible while minimizing transmission power. Through a comprehensive set of realistic simulations, we then systematically quantify the feasibility of concurrent communication with and without transmission power control as many radio and environmental parameters vary, including node position, mean and variance of path loss, signal-to-interference-plus-noise-ratio threshold ($SINR_\theta$) for packet reception, granularity and range of transmission power control. Our simulations show that often, 40-75% of the time depending primarily on distance and location, two pairs of nodes can communicate concurrently without loss even if both transmitters are within the radio sensing range of both receivers. We can observe large CTXable region with fixed transmit power, but dynamic power control significantly improves concurrent communications. Finally, at least one transmitter can almost always capture the channel in the event of concurrent transmissions, so the cost of failed attempts to CTX are minimal. We validate our simulations with testbed experiments using MicaZ motes, confirming that concurrent communication is possible to a very significant extent in real systems. These results suggest that CSMA with RTS/CTS is overly conservative and there are often gains to be realized by abandoning it.

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

Son07a: Dongjin Son, Bhaskar Krishnamachari, and John Heidemann. Evaluating the Importance of Concurrent Packet Communication in Wireless Networks. Technical Report ISI-TR-639, USC/Information Sciences Institute, April, 2007. <http://www.isi.edu/~johnh/PAPERS/Son07a.html>.

@techreport{Son07a,
	author = "Dongjin Son and Bhaskar Krishnamachari and John Heidemann",
	title = "Evaluating the Importance of Concurrent Packet Communication in Wireless Networks",
	institution = "USC/Information Sciences Institute",
	year = "2007",
	number = "ISI-TR-639",
	month = "April",
	keywords = "sensornets, 802.11, rts-cts, concurrent
                         packet transmission",
	url = "http://www.isi.edu/~johnh/PAPERS/Son07a.html",
	pdfurl = "http://www.isi.edu/~johnh/PAPERS/Son07a.pdf",
}

Copyright

This paper is copyright © 2007 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.