围长为8的较大列重准循环低密度奇偶校验码的行重普适代数构造

Row-weight Universal Algebraic Constructions of Girth-8 Quasi-Cyclic Low-Density Parity-Check Codes with Large Column Weights

适合于任意行重(即行重普适(RWU))的无小环准循环(QC)低密度奇偶校验(LDPC)短码,对于LDPC码的理论研究和工程应用具有重要意义。具有行重普适特性且消除4环6环的现有构造方法,只能针对列重为3和4的情况提供QC-LDPC短码。该文在最大公约数(GCD)框架的基础上,对于列重为5和6的情况,提出了3种具有行重普适特性且消除4环6环的构造方法。与现有的行重普适方法相比,新方法提供的码长从目前的与行重呈4次方关系锐减至与行重呈3次方关系,因而可以为QC-LDPC码的复合构造和高级优化等需要较大列重基础码的场合提供行重普适的无4环无6环短码。此外,与基于计算机搜索的对称结构QC-LDPC码相比,新码不仅无需搜索、描述复杂度更低,而且具有更好的译码性能。

Short Quasi-Cyclic(QC)Low-Density Parity-Check(LDPC)codes without small cycles suitable for an arbitrary row weight(i.e.,Row-Weight Universal(RWU)),are of great significance for both theoretical research and engineering application.Existing methods having RWU property and guaranteeing the nonexistence of 4-cycles and 6-cycles,can only offer short QC-LDPC codes for the column weights of 3 and 4.Based on the Greatest Common Divisor(GCD)framework,three new methods are proposed in this paper for the column weights of 5 and 6,which can possess RWU property and at the same time remove all 4-cycles and 6-cycles.Compared with existing methods with RWU property,the code lengths of the novel methods are sharply reduced from the fourth power of row weight to the third power of row weight.Therefore,the new methods can provide short RWU QC-LDPC codes without 4-cycles and 6-cycles for occasions where base codes with large column weights are required,such as composite constructions and advanced optimization pertaining to QC-LDPC codes.Moreover,compared with the search-based symmetric QC-LDPC codes,the new codes need no search,have lower description complexity,and exhibit better decoding performance.