A Phenomenological Study on Threshold Improvement via Spatial Coupling

Keigo TAKEUCHI  Toshiyuki TANAKA  Tsutomu KAWABATA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E95-A   No.5   pp.974-977
Publication Date: 2012/05/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E95.A.974
Print ISSN: 0916-8508
Type of Manuscript: LETTER
Category: Information Theory
spatial coupling,  threshold saturation,  belief propagation (BP),  dynamical systems,  

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Kudekar et al. proved an interesting result in low-density parity-check (LDPC) convolutional codes: The belief-propagation (BP) threshold is boosted to the maximum-a-posteriori (MAP) threshold by spatial coupling. Furthermore, the authors showed that the BP threshold for code-division multiple-access (CDMA) systems is improved up to the optimal one via spatial coupling. In this letter, a phenomenological model for elucidating the essence of these phenomenon, called threshold improvement, is proposed. The main result implies that threshold improvement occurs for spatially-coupled general graphical models.