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: Fine-Granularity Loading Schemes Using Adaptive Reed-Solomon Coding for xDSL-DMT Systems | Hindawi Publishing Corporation EURASIP Journal on Applied Signal Processing Volume 2006 Article ID 65716 Pages 1-13 DOI ASP 2006 65716 Fine-Granularity Loading Schemes Using Adaptive Reed-Solomon Coding for xDSL-DMT Systems Saswat Panigrahi and Tho Le-Ngoc Department of Electrical and Computer Engineering McGill University 3480 University Street Montreal QC Canada H3A 2A7 Received 29 November 2004 Revised 9 May 2005 Accepted 22 July 2005 While most existing loading algorithms for xDSL-DMT systems strive for the optimal energy distribution to maximize their rate the amounts of bits loaded to subcarriers are constrained to be integers and the associated granularity losses can represent a significant percentage of the achievable data rate especially in the presence of the peak-power constraint. To recover these losses we propose a fine-granularity loading scheme using joint optimization of adaptive modulation and flexible coding parameters based on programmable Reed-Solomon RS codes and bit-error probability criterion. Illustrative examples of applications to VDSL-DMT systems indicate that the proposed scheme can offer a rate increase of about 20 in most cases as compared to various existing integer-bit-loading algorithms. This improvement is in good agreement with the theoretical estimates developed to quantify the granularity loss. Copyright 2006 Hindawi Publishing Corporation. All rights reserved. 1. INTRODUCTION Discrete multitone DMT modulation 1 has been widely used in xDSL applications such as asymmetric DSL ADSL 2 by the American National Standards Institute ANSI and the European Telecommunications Standard Institute ETSI and more recently for VDSL 3 by ANSI. Loading strategy is used for dynamic subcarrier rate and power allocation for given channel conditions system constraints and performance requirements. For a multichannel total-power constrained problem the optimal power distribution has long been known to be the water-filling distribution 4 . .
