Simulation of FEC-based error control for packet audio on theInternet
Podolsky, M.; Romer, C.; McCanne, S.
INFOCOM apos;98. Seventeenth Annual Joint Conference of the IEEE Computer and Communications Societies. Proceedings. IEEE
Volume 2, Issue , 29 Mar-2 Apr 1998 Page(s):505 - 515 vol.2
Digital Object Identifier 10.1109/INFCOM.1998.665068
Summary:Real-time audio over a best-effort network, such as the Internet,
frequently suffers from packet loss. To mitigate the impact of such
packet loss, several research efforts and implementation studies
advocate the use of forward error correction (FEC) coding. Although
these prior works have pioneered promising and novel applications of FEC
to Internet audio, they do not definitively demonstrate the advantages
of FEC because they do not evaluate aggregate performance that results
from multiplexing many like flows. We build on previous landmark works
with a systematic study of FEC for packet audio that characterizes the
aggregate performance across all audio sources in the network. We refine
the novel but ad hoc coding techniques proposed by Hardman, Sasse,
Handley and Watson (see Proc. INET, 1995) into a formal framework that
we call “signal processing-based FEC” (SFEC) and use our
framework to more rigorously evaluate the relative merits of this
approach. Through extensive simulation, we evaluate the
“scalability” of SFEC for packet audio-i.e., the ability for
a coding algorithm to improve aggregate performance when used by all
sources in the network-and find that optimal signal quality is achieved
when sources react to network congestion not by blindly adding FEC, but
rather by adding FEC in a controlled fashion that simultaneously
constrains the source-coding rate. As a result, packet loss is mitigated
without introducing more congestion, thus admitting a more scalable and
effective approach than successively adding redundancy to a constant
bit-rate source. While this result may seem intuitive, it has not been
previously suggested in the context of Internet audio, and until now,
has not been systematically studied
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