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  • Research Article
  • Open Access

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

EURASIP Journal on Advances in Signal Processing20052005:178541

  • Received: 1 October 2003
  • Published:


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.

Keywords and phrases:

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

Authors’ Affiliations

Institute of Communication Systems and Data Processing, Aachen University of Technology (RWTH), Aachen, 52056, Germany


© M. Adrat and P. Vary 2005

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.