Iterative Decoding of Compound Codes by Probability Propagation in Graphical Models

Abstract—We present a unified graphical model framework for describing compound codes and deriving iterative decoding algorithms. After reviewing a variety of graphical models (Markov random fields, Tanner graphs, and Bayesian networks), we derive a general distributed marginalization algorithm for functions described by factor graphs. From this general algorithm, Pearl’s belief propagation algorithm is easily derived as a special case. We point out that recently developed iterative decoding algorithms for various codes, including “turbo decoding” of parallelconcatenated convolutional codes, may be viewed as probability propagation in a graphical model of the code. We focus on Bayesian network descriptions of codes, which give a natural input/state/output/channel description of a code and channel, and we indicate how iterative decoders can be developed for parallel- and serially-concatenated coding systems, product codes, and low-density parity-check codes.

• Type: Journal
• Year: 1998
• Where: JSAC
• Authors: Frank R. Kschischang, Brendan J. Frey
• Keywords: Bayesian Network, Graphical Model, Iterative Decoding Algorithms, JSAC 1998