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Open Access

Jointly Decoded Raptor Codes: Analysis and Design for the BIAWGN Channel

EURASIP Journal on Wireless Communications and Networking20092009:657970

https://doi.org/10.1155/2009/657970

Received: 6 August 2008

Accepted: 6 June 2009

Published: 19 July 2009

Abstract

We are interested in the analysis and optimization of Raptor codes under a joint decoding framework, that is, when the precode and the fountain code exchange soft information iteratively. We develop an analytical asymptotic convergence analysis of the joint decoder, derive an optimization method for the design of efficient output degree distributions, and show that the new optimized distributions outperform the existing ones, both at long and moderate lengths. We also show that jointly decoded Raptor codes are robust to channel variation: they perform reasonably well over a wide range of channel capacities. This robustness property was already known for the erasure channel but not for the Gaussian channel. Finally, we discuss some finite length code design issues. Contrary to what is commonly believed, we show by simulations that using a relatively low rate for the precode , we can improve greatly the error floor performance of the Raptor code.

Keywords

Degree DistributionChannel CapacityLength CodeAsymptotic ConvergenceSoft Information

Publisher note

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Authors’ Affiliations

(1)
ETIS, CNRS, ENSEA, Cergy-Pontoise University, Cergy-Pontoise Cedex, France

Copyright

© Auguste Venkiah et al. 2009

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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