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The Research and Application of LDPC Codes Decoding Algorithm

Author: WangDongMei
Tutor: WangXiuFang
School: Daqing Petroleum Institute
Course: Communication and Information System
Keywords: LDPC codes Probability domain BP algorithm LLR-BP algorithm Orthogonal Frequency Division Multiplexing
CLC: TN911.2
Type: Master's thesis
Year: 2008
Downloads: 116
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Abstract


LDPC code is a linear block code close to the Shannon limit , excellent BER performance even under very low signal-to-noise ratio environment , has become one of today's most watched channel coding areas of research focus has been as key technologies of the fourth generation mobile communication system has a good prospect in the future high-speed broadband wireless communication . The main work of this paper include : First, in the analysis of the Tanner graph representation of LDPC code , description code length , the columns weight and the number of iterations of LDPC codes BER performance by computer simulation and theoretical analysis on the basis of the basic theory of the structure and coding methods the impact . Then, for the decoding of the check node update process based on the the Tanh rule and the LLR-BP algorithm , based on Gallager programs exist caused by the hyperbolic tangent function to calculate the complex issues , from reducing the computational complexity of the viewpoint , the hyperbolic tangent function piecewise linear approximation proposed decoding algorithm based on the improvement of the the the Tanh law and the LLR-BP algorithm based on Gallager program . Theoretical analysis and simulation results show improved decoding algorithm with the original LLR-BP algorithm compared to the superiority of computational complexity and performance . Finally, build the OFDM system simulation model based LDPC codes , will be based on the the Tanh law LLR-BP algorithm and its improved OFDM system based on LDPC code decoding algorithm applied to the corrected . Preliminary simulation based on the IEEE 802.11a standard , additive white Gaussian noise channel , OFDM system performance based on LDPC codes , the simulation results show that : LDPC code can be improved to a certain extent, the performance of the OFDM system ; 2PSK, QPSK 16QAM modulation mode , based LDPC codes ( multi- level modulation ) based the Tanh law LLR-BP algorithm improved algorithm for decoding LDPC coded OFDM system performance slightly better than the (multi- level modulation ) Tanh rule LLR-BP decoding algorithm performance .

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Communicate > Communication theory > Information Theory
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