Tanner码不存在四环的充要条件  

Necessary and sufficient condition for Tanner codes without girth 4

作　　者：赵莹[1] 肖扬[1] 

机构地区：[1]北京交通大学信息科学研究所,北京100044

出　　处：《系统工程与电子技术》2009年第2期300-304,共5页Systems Engineering and Electronics

基　　金：国家自然科学基金(60572093)资助课题

摘　　要：现有准循环LDPC码(QC LDPC码)的设计未考虑如何避免短环(四环)问题,而短环的存在导致QCLDPC码的误码率性能远低于随机LDPC码。为解决这一问题,提出在一类重要的准循环LDPC码—Tanner码中避免四环的定理,这些定理可作为构造Tanner码的约束条件。根据提出的定理调整校验矩阵中循环矩阵的维数和移位因子,可以构造无四环的QC LDPC码,同时扩展了Tanner码的定义。最后以实例验证了所提定理,仿真结果表明设计的Tanner码具有良好的误码率性能。To solve the problem of the girth 4 which will lead to a serious decrease in the performance of quasi-cyclic low-density parity-check （QC LDPC） codes, this paper presents the necessary and sufficient conditions of Tanner codes without girth 4 in the form of several theorems. These theorems can be used as the con- straint conditions for the construction of Tanner codes. To construct the Tanner codes without girth 4 needs to adjust the dimension and the shift factors of the circulant matrices of the given sparse parity-check matrices ac- cording to the proposed theorems. Examples are provided to verify the theorems, and computer simulation re- sults show that the Tanner codes obtained by proposed constructions achieve good BER performance compared with that of randomly constructed LDPC codes.

关 键 词：信道编码 循环矩阵 低密度校验码 准循环码 

分 类 号：TN911.2[电子电信—通信与信息系统] TN911.5[电子电信—信息与通信工程]