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Iterative Source-Channel Decoding: Improved System Design Using EXIT Charts

Abstract

The error robustness of digital communication systems using source and channel coding can be improved by iterative source-channel decoding (ISCD). The turbo-like evaluation of natural residual source redundancy and of artificial channel coding redundancy makes step-wise quality gains possible by several iterations. The maximum number of profitable iterations is predictable by an EXIT chart analysis. In this contribution, we exploit the EXIT chart representation to improve the error correcting/concealing capabilities of ISCD schemes. We propose new design guidelines to select appropriate bit mappings and to design the channel coding component. A parametric source coding scheme with some residual redundancy is assumed. Applying both innovations, the new EXIT-optimized index assignment as well as the appropriately designed recursive nonsystematic convolutional (RNSC) code, allows to outperform known approaches to ISCD by far in the most relevant channel conditions.

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Correspondence to Marc Adrat.

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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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Adrat, M., Vary, P. Iterative Source-Channel Decoding: Improved System Design Using EXIT Charts. EURASIP J. Adv. Signal Process. 2005, 178541 (2005). https://doi.org/10.1155/ASP.2005.928

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Keywords and phrases:

  • iterative source-channel decoding
  • turbo principle
  • soft-input/soft-output decoding
  • softbit source decoding
  • extrinsic information
  • EXIT charts