Shiro Ikeda, Toshiyuki Tanaka, Shun-ichi Amari
The mystery of belief propagation (BP) decoder, especially of the turbo decoding, is studied from information geometrical viewpoint. The loopy belief network (BN) of turbo codes makes it difﬁcult to obtain the true “belief” by BP, and the characteristics of the algorithm and its equilib- rium are not clearly understood. Our study gives an intuitive understand- ing of the mechanism, and a new framework for the analysis. Based on the framework, we reveal basic properties of the turbo decoding.