Subject: [manet] New Approach to Multicast

From: Mike Christman <[email-masked]>
Date: Tue, 27 Aug 2002 13:43:16 -0400 (EDT)

Hello all,

I just wanted to present a master's thesis on a new approach/algorithm to 
multicast in MANETs done at Virginia Tech.  This approach attempts to 
create efficient multicast trees in order to reduce DATA overhead.  That is, 
we try to reduce the number of redundent data rebroadcasts in the multicast 
tree.  The protocol is called XMMAN: Extensions for Multicast in Mobile Ad-hoc
Networks, and the link to the entire document is 

http://scholar.lib.vt.edu/theses/available/etd-08142002-131727/

For those who are interested, the Protocol section reads like anan Internet 
Draft.  A protoype implementation (not a simulation) was developed to test the 
protocol and MAY be available for release.

I have included the Abstract in the body of this message.  Thanks for your 
interest!

Mike Christman

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Extensions for Multicast in Mobile Ad-hoc Networks (XMMAN): The Reduction 
of Data Overhead in Wireless Multicast Trees 

Michael Edward Christman 

Dr. Scott F. Midkiff, Chair 

Electrical Engineering 

(ABSTRACT) 

Mobile Ad hoc Network (MANET) routing protocols are designed to provide 
connectivity between wireless mobile nodes that do not have access to 
high-speed backbone networks. While many unicast MANET protocols have been 
explored, research involving multicast protocols has been limited. 
Existing multicast algorithms attempt to reduce routing overhead, but few, 
if any, attempt to reduce data overhead. 

The broadcast nature of wireless communication creates a unique 
environment in which overlaps in coverage are common. When designed 
properly, a multicast algorithm can take advantage of these overlaps and 
reduce data overhead. Unlike a unicast route, in which there is one path 
between a sender and receiver, a multicast tree can have multiple branches 
between the sender and its multiple receivers. Some of these paths can be 
combined to reduce redundant data rebroadcasts. 

The extensions presented in this thesis are a combination of existing and 
original routing techniques that were designed to reduce data rebroadcasts 
by aggregating multicast data flows. One such optimization takes advantage 
of the multipoint relay (MPR) nodes used by the Optimized Link State 
Routing (OLSR) unicast protocol. These nodes are used in unicast routing 
to reduce network broadcast, but can be used to help create efficient 
multicast data flows. Additionally, by listening to routing messages meant 
for other nodes, a host can learn a bit about its network and may be able 
to make routing changes that improve the multicast tree. 

This protocol was implemented as a software router in Linux. It should be 
emphasized that this is a real implementation and not a simulation. 
Experiments showed that the number of data packets in the network could be 
reduced by as much as 19 percent. These improvements were accomplished 
while using only a small amount of routing overhead. 

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