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

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.

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Correspondence to Auguste Venkiah.

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Open Access This article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Venkiah, A., Poulliat, C. & Declercq, D. Jointly Decoded Raptor Codes: Analysis and Design for the BIAWGN Channel. J Wireless Com Network 2009, 657970 (2009). https://doi.org/10.1155/2009/657970

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

Keywords

  • Degree Distribution
  • Channel Capacity
  • Length Code
  • Asymptotic Convergence
  • Soft Information