tailieunhanh - báo cáo hóa học:" Research Article Random Bit Flipping and EXIT Charts for Nonuniform Binary Sources and Joint Source-Channel Turbo Systems"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Random Bit Flipping and EXIT Charts for Nonuniform Binary Sources and Joint Source-Channel Turbo Systems | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2009 Article ID 354107 6 pages doi 2009 354107 Research Article Random Bit Flipping and EXIT Charts for Nonuniform Binary Sources and Joint Source-Channel Turbo Systems Xavier Jaspar1 and Luc Vandendorpe2 1Laborelec Rodestraat 125 B-1630 Linkebeek Belgium 2 Communications and Remote Sensing Laboratory Universite catholique de Louvain Place du Levant 2 B-1348 Louvain-la-Neuve Belgium Correspondence should be addressed to Xavier Jaspar Received 29 January 2009 Revised 7 June 2009 Accepted 7 August 2009 Recommended by Athanasios Rontogiannis Joint source-channel turbo techniques have recently been explored a lot in literature as one promising possibility to lower the end-to-end distortion with fixed length codes variable length codes and quasi arithmetic codes. Still many issues remain to be clarified before production use. This short contribution clarifies very concisely several issues that arise with EXIT charts and nonuniform binary sources a nonuniform binary source can be the result of a nonbinary source followed by a binary source code . We propose two histogram-based methods to estimate the charts and discuss their equivalence. The first one is a mathematical generalization of the original EXIT charts to nonuniform bits. The second one uses a random bit flipping to make the bits virtually uniform and has two interesting advantages 1 it handles straightforwardly outer codes with an entropy varying with the bit position and 2 it provides a chart for the inner code that is independent of the outer code. Copyright 2009 X. Jaspar and L. Vandendorpe. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. 1. Introduction Consider the generic system in Figure 1. It involves a serial concatenation