@article{Forney2001CodesOG,
title={Codes on graphs: Normal realizations},
author={G. David Forney},
journal={IEEE Trans. Information Theory},
year={2001},
volume={47},
pages={520-548}
}

A generalized state realization of the Wiberg type is called normal if symbol variables have degree1 and state variables have degree2. A natural graphical model of such a realization has leaf edges representing symbols, ordinary edges representing states, and vertices representing local constraints. Such a graph can be decoded by any version of the sum-product algorithm. Any state realization of a code can be put into normal form without essential change in the corresponding graph or in its… CONTINUE READING