Subject: [manet] broadcast with 802.11 MAC

From: "#XIE JIAWEI#" <[email-masked]>
Date: Wed, 11 Feb 2004 10:33:49 +0800

Dear all,

I am doing some research work concerning reducing the probability of collision while performing broadcast with IEEE 802.11 MAC. I am also interested in reliable broadcast with 802.11 MAC. Could anybody guide on these two issues?

Thank you very much!

Best regards,

Jiawei

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From: Nael Abu-Ghazaleh <[email-masked]>
Date: Tue, 10 Feb 2004 23:23:59 -0500 (EST)

Hi,

I am aware of the following related work to this problem and would be
interested in hearing others.

Tang and Gerla at UCLA had a couple of papers on modifying 802.11
broadcast to improve reliability.  The primary idea in one of them is 
to require acknowledgements for broadcasts, but to treat collisions
when a broadcast happens as an acknowledgement (by detecting noise on 
the channel).  This makes sure at least one node receives the
broadcast successfully.  A followup paper keeps track of sequence
numbers of broadcasts and NACKs missing sequence numbers.  

Ghandi et al had a mobihoc 2003 paper with a CDS approach to broadcast
that also times rebroadcasts to eliminate collisions among packets of
the same broadcast (using two hop neighbor knowledge per CDS).  However,
this does not prevent losses due to other interfering traffic.

We have a tech report and a paper under review that characterize the
effect of MAC unreliability on network wide broadcast operations.  We also
investigate selectively rebroadcasting packets to improve reliability.
Under high interference, and for sparse networks, network wide broadcast
protocols really break down (flooding as well as other protocols that rely
on MAC level broadcast).  

We looked at several heuristics for generating the
additional rebroadcast based on factors such as the local interference
level and the number of redundant rebroadcasts heard.  Of course, this
does not guarantee full coverage, but it improves it significantly.  I
would be happy to send you a copy of our tech report.

best regards,
-nael
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Dr. Nael Abu-Ghazaleh
Assistant Professor -- CS Dept. 
State University of New York
Binghamton, NY 13902--6000
(607) 777 4748 (Phone)
(607) 777 4729 (Fax)
[email-masked]