30-01-2013, 12:22 PM
A Model-Based Approach to Evaluation of the Efficacy of FEC Coding in Combating Network Packet Losses
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Abstract
We propose a model-based analytic approach for
evaluating the overall efficacy of FEC coding combined with interleaving
in combating packet losses in IP networks. We study both single-session and multiple-session scenarios, and provide a simple algorithm for the more complicated multiple-session scenario. We show that the
unified approach provides an integrated framework for exploring
the tradeoffs between the key coding parameters; specifically,
interleaving depths, channel coding rates and block lengths. The
approach facilitates the selection of optimal coding strategies for
different multimedia applications with various user quality-of-service
(QoS) requirements and system constraints. We also provide
an information-theoretic bound on the performance achievable
with FEC coding in IP networks.
INTRODUCTION
THE packet transport service provided by representative
packet-switched networks, including IP networks, is not
reliable and the quality-of-service (QoS) cannot be guaranteed.
Packets may be lost due to buffer overflow in switching nodes,
be discarded due to excessive bit errors and failure to pass
the cyclic redundancy check (CRC) at the link layer, or be
discarded by network control mechanisms as a response to
congestion somewhere in the network. Forward error correction
(FEC) coding has often been proposed for end-to-end recovery
from such packet losses. However, the use of FEC in this
application provides a double-edged sword.
FEC With Block Interleaving
FEC performance is often limited by the bursty nature of typical
packet-loss processes, and block interleaving techniques are
frequently used to reduce the burstiness of the packet-loss processes
in networks [4], thereby improving FEC performance.
In this section, we analyze the efficacy of interleaving in reducing
the burstiness of network packet-loss processes and in
improving the FEC performance.