| Conference Paper |
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| Title |
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FairCast: Fair Multi-Media Streaming in Ad Hoc Networks through Local Congestion Control
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| Abstract |
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Multicast streaming is gaining increasing importance
in wireless ad hoc networks, in part because ad
hoc scenarios often include team activities and the requirement
for distribution of audio, video and situation awareness
to the members. At the network level, techniques for
routing the multimedia streams are quite mature. Much
more challenging is the allocation of resources, the fair
sharing among streams and the control of congestion.
While in rate adaptive UNICAST streams congestion
control and fair sharing are accomplished with end-to-end
feedback techniques inspired to TCP, the feedback does
not scale well in MULTICAST. In fact, it leads to the
well knows ACK/NAK “implosion” problem and unfair
penalties for heterogeneous receivers.
These limitations can be overcome using backpressure
from congestion points to the sources - but this approach
suffers of latency and cannot rapidly adjust to changes
in traffic. Another solution is multilayer adaptive coding.
Namely, the encoding adaptation is done locally by dropping
layers. It does not require end-to-end feedback nor
changes in input rates. Multi-resolution codes are now
becoming attractive due to the progress in technology;
we expect these to become the prevalent techniques in
large scale media distribution. One issue, however, that
still remains to be local resolved is the fair sharing among
competing multicast streams.
In this paper we address the congestion control AND
fair sharing in a multilayer multicast scenario. We show
that lack of proper fairness provisions in the “local adjustments”
can lead to serious “capture” situations, especially
in heterogeneous traffic mixes (e.g. voice and video). We then propose a FAIR local adjustment that targets a fair
dropping of packets in each interference domain. We
show that the scheme can be interpreted as a distributed
implementation of a utility function minimization, where
the utility is the packet loss subject to fairness bounds
across flows. This formulation guarantees stability and
convergence of the distributed algorithm.
The main contributions of this paper are the low overhead
design of the local fairness enforcement algorithm,
the utility function framework and the demonstration of
convergence via simulation in representative scenarios.
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| Download |
Paper: PDF file of paper
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| Information & Date |
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MSWiM, Vancouver, British Columbia, Canada, October. 2008
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| Authors |
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Gustavo Marfia
Paolo Lutterotti
Stephan Eidenbenz
Giovanni Pau
Mario Gerla
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