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: A Systematic Approach to Modified BCJR MAP Algorithms for Convolutional Codes | Hindawi Publishing Corporation EURASIP Journal on Applied Signal Processing Volume 2006 Article ID 95360 Pages 1-15 DOI ASP 2006 95360 A Systematic Approach to Modified BCJR MAP Algorithms for Convolutional Codes Sichun Wang1 and Francois Patenaude2 1 Defence Research and Development Canada - Ottawa Ottawa ON Canada K1A 0Z4 2 Communications Research Centre Canada Ottawa ON Canada K2H8S2 Received 19 November 2004 Revised 19 July 2005 Accepted 12 September 2005 Recommended for Publication by Vincent Poor Since Berrou Glavieux and Thitimajshima published their landmark paper in 1993 different modified BCJR MAP algorithms have appeared in the literature. The existence of a relatively large number of similar but different modified BCJR MAP algorithms derived using the Markov chain properties of convolutional codes naturally leads to the following questions. What is the relationship among the different modified BCJR MAP algorithms What are their relative performance computational complexities and memory requirements In this paper we answer these questions. We derive systematically four major modified BCJR MAP algorithms from the BCJR MAP algorithm using simple mathematical transformations. The connections between the original and the four modified BCJR MAP algorithms are established. A detailed analysis of the different modified BCJR MAP algorithms shows that they have identical computational complexities and memory requirements. Computer simulations demonstrate that the four modified BCJR MAP algorithms all have identical performance to the BCJR MAP algorithm. Copyright 2006 S. Wang and F. Patenaude. 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 In 1993 Berrou et al. 1 introduced new types of codes called turbo codes which have demonstrated performance close to the theoretical limit .
