Convergence of non-binary iterative decoding

Mutual information transfer characteristics have been proposed by ten Brink (see IEE Electron. Lett., vol.35, no.10, p.806-9, 1999) as a quasi-analytical tool for the performance analysis of iterative decoding of concatenated codes. Given the individual transfer characteristics of the component codes in a concatenated coding system (obtained by simulation), the convergence region and average decoding trajectory of the concatenated system may be accurately predicted. In this paper, we extend the techniques of ten Brink to non-binary codes. In addition to providing a useful tool for the analysis of non-binary codes, our extension reveals several subtle points concerning the motivation and interpretation of the technique for binary codes. We propose a method for practical implementation of our extension, and apply the technique to the evaluation or non-binary turbo codes and space-time turbo codes