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两种新的对数似然比简化算法及其在LDPC码上的应用
引用本文:徐昌庆,胡震宇,宋文涛. 两种新的对数似然比简化算法及其在LDPC码上的应用[J]. 上海交通大学学报, 2006, 40(1): 46-49
作者姓名:徐昌庆  胡震宇  宋文涛
作者单位:上海交通大学,电子工程系,上海,200030;上海交通大学,电子工程系,上海,200030;上海交通大学,电子工程系,上海,200030
摘    要:通常用取最小绝对值方法对若干比特模二和的对数似然比(LLR)进行简化,该方法存在误差积累问题,因而不是最有效的.为此,提出了两种新的LLR简化算法:正比例函数拟和修正法和逐点平均值曲线修正法,并用这两种算法替代了低密度奇偶校验(LDPC)码归一化最有效可信传播(UMP-BP)译码中的LLR计算,使其在降低译码复杂度的情况下误码率更低.仿真结果表明,对于码长1 024 bits的LDPC码,采用所提出的LLR简化算法后性能较UMP-BP译码方法有0.4 dB提高,并与最优的可信传播算法接近,计算复杂度也有明显下降.

关 键 词:信道编码  低密度奇偶校验码  对数似然比  可信传播算法  迭代译码
文章编号:1006-2467(2006)01-0046-04
收稿时间:2004-12-25
修稿时间:2004-12-25

Two Novel Simplified Logarithm Likelihood Ratio Calculating Algorithms and Their Application in LDPC Codes
XU Chang-qing,HU Zhen-yu,SONG Wen-tao. Two Novel Simplified Logarithm Likelihood Ratio Calculating Algorithms and Their Application in LDPC Codes[J]. Journal of Shanghai Jiaotong University, 2006, 40(1): 46-49
Authors:XU Chang-qing  HU Zhen-yu  SONG Wen-tao
Affiliation:Dept. of Electronic Eng. , Shanghai Jiaotong Univ. , Shanghai 200030,China
Abstract:The method of taking minimum absolute value is generally used to simplify logarithm likelihood ratio(LLR) of modulo 2 sum of several bits.However,this method is not very effective because of that accumulates errors.Two novel simplified LLR calculating algorithms,the direct proportion approximation as well as the each dot approximation,were proposed and applied on uniformly most powerful-belief propagation(UMP-BP) algorithm,a decoding algorithm of low density parity check(LDPC) codes,to reduce the complexity and improve the BER performance.The simulation results show that,for an LDPC code of length 1 024 bits, the proposed method improves 0.4 dB in performance over the UMP-BP,and performs almost the same as the optimum belief propagation(BP) decoding algorithm.
Keywords:channel coding  low density parity check(LDPC) codes  logarithm likelihood ratio(LLR)  belief propagation(BP) decoding algorithm  iterative decoding  
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