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 Construction and Iterative Decoding of LDPC Codes Over Rings for Phase-Noisy Channels | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008 Article ID 385421 9 pages doi 2008 385421 Research Article Construction and Iterative Decoding of LDPC Codes Over Rings for Phase-Noisy Channels Sridhar Karuppasami and William G. Cowley Institute for Telecommunications Research University of South Australia Mawson Lakes SA 5095 Australia Correspondence should be addressed to Sridhar Karuppasami Received 1 November 2007 Revised 7 March 2008 Accepted 27 March 2008 Recommended by Branka Vucetic This paper presents the construction and iterative decoding of low-density parity-check LDPC codes for channels affected by phase noise. The LDPC code is based on integer rings and designed to converge under phase-noisy channels. We assume that phase variations are small over short blocks of adjacent symbols. A part of the constructed code is inherently built with this knowledge and hence able to withstand a phase rotation of 2n M radians where M is the number of phase symmetries in the signal set that occur at different observation intervals. Another part of the code estimates the phase ambiguity present in every observation interval. The code makes use of simple blind or turbo phase estimators to provide phase estimates over every observation interval. We propose an iterative decoding schedule to apply the sum-product algorithm SPA on the factor graph of the code for its convergence. To illustrate the new method we present the performance results of an LDPC code constructed over Z4 with quadrature phase shift keying QPSK modulated signals transmitted over a static channel but affected by phase noise which is modeled by the Wiener random-walk process. The results show that the code can withstand phase noise of 2 standard deviation per symbol with small loss. Copyright 2008 S. Karuppasami and W. G. Cowley. This is an open access article distributed under the Creative Commons .
