Constacyclic and cyclic codes over finite chain tings

The problem of Gray image of constacyclic code over finite chain ring is studied. A Gray map between codes over a finite chain ring and a finite field is defined. The Gray image of a linear constacyclic code over the finite chain ring is proved to be a distance invariant quasi-cyclic code over the finite field. It is shown that every code over the finite field, which is the Gray image of a cyclic code over the finite chain ring, is equivalent to a quasi-cyclic code.     

Constacyclic and cyclic codes over finite chain rings

The problem of Gray image of constacyclic code over finite chain ring is studied. A Gray map between codes over a finite chain ring and a finite field is defined. The Gray image of a linear constacyclic code over the finite chain ring is proved to be a distance invariant quasi-cyclic code over the finite field. It is shown that every code over the finite field, which is the Gray image of a cyclic code over the finite chain ring, is equivalent to a quasi-cyclic code.     

有限非链环上的自对偶常循环码及其应用

纠错码是提高信息传输效率与可靠性的重要手段.构造性能良好的线性码类是纠错码研究中的一个基本问题.本文主要讨论了有限非链环F_q[v]/（v^m－v）上自对偶常循环码的代数结构,包括Euclidean自对偶常循环码、Hermitian自对偶常循环码以及Hermitian自对偶常循环码的极大距离可分（MDS）码.本文给出了环F_q[v]/（v^m－v）上常循环码是Euclidean自对偶码的充分条件,以及是Hermitian自对偶码的充要条件,并利用Gray映射构造了有限域F_q上一些参数较好的自对偶码.特别地,本文得到了有限域F_19²上一个新的参数为[16,8,6]的Hermitian自对偶码.     

On the algebraic structure of quasi-cyclic codes .I. Finite fields

A new algebraic approach to quasi-cyclic codes is introduced. The key idea is to regard a quasi-cyclic code over a field as a linear code over an auxiliary ring. By the use of the Chinese remainder theorem (CRT), or of the discrete Fourier transform (DFT), that ring can be decomposed into a direct product of fields. That ring decomposition in turn yields a code construction from codes of lower lengths which turns out to be in some cases the celebrated squaring and cubing constructions and in other cases the (u+υ|u-υ) and Vandermonde constructions. All binary extended quadratic residue codes of length a multiple of three are shown to be attainable by the cubing construction. Quinting and septing constructions are introduced. Other results made possible by the ring decomposition are a characterization of self-dual quasi-cyclic codes, and a trace representation that generalizes that of cyclic codes     

有限域上最优码的一种新的构造方法

基于域F_p^m上一类特殊的矩阵,定义了环R(_p^m,k)=F_p^m[u]/k>到F_p^p_mj的一个新的Gray映射,其中u^k=0、p为素数、j为正整数且p^j－1+1≤k≤p^j.得到了环R(_p^m,k)上码长为任意长度N的(1+u)常循环码的Gray象是F_p^m上长为p^jN的保距线性循环码,并给出了Gray象的生成多项式,构造了F₃,F₅和F₇上的一些最优线性循环码.     

环F2+uF2+vF2+uvF2上(1+uv)-循环码

该文定义了有限非链环R=F2+uF2+vF2+uvF2上(1+uv)-循环码的相关概念,讨论了其与该环上循环码的关系,证明了此环上(1+uv)-循环码在关于齐次重量的等距Gray映射hom下的二元象是一个长为8n的4-准循环码, 并由此映射得到了一些好的二元线性准循环码。     

环F2+uF2+…+uk-1F2上常循环自对偶码

最近,剩余类环上的常循环码及常循环自对偶码引起了编码学者的极大关注.本文首先利用一些相关的线性码,建立了一类特殊有限链环上长为N的常循环自对偶码的一般理论,利用其结果给出了该环上长为N的(1+uλ)-常循环自对偶码存在的充分条件,得到了该环上长为N的一些常循环自对偶码,并给出了其生成多项式.     

Constacyclic codes of arbitrary lengths over ring Z_{p^m } + vZ_{p^m }

By constructing a Gray map, constacyclic codes of arbitrary lengths over ring R = Zpm ＋ vZpm are studied, where v2 = v. The structure of constacyclic codes over R and their dual codes are obtained. A necessary and sufficient condition for a linear code to be self-dual constacyclic is given. In particular, （1 ＋ （v ＋ 1）αp）-constacyclic codes over R are classified in terms of generator polynomial, where α is a unit of Zpm.     

形式幂级数环中的循环码

研究了形式幂级数环与有限链环上的循环码与负循环码,利用环同构与交换图技术得到这2类环上循环码与负循环码,以及Dougherty等得到的形式幂级数环上的循环码的投影码也是循环码的结果,给出了形式幂级数环上码为循环码的一个充要条件。借助这一条件,得到了含有形式幂级数环的中国积中循环码的投影码的循环性。     

环Z4上自对偶码的构造

利用有限环Z₄+vZ₄（其中v²=1）上自对偶码,给出了一种构造Z₄上自对偶码的方法.引入了（Z₄+vZ₄）ⁿ到Z₄²ⁿ的保距Gray映射,给出了Z₄+vZ₄上自对偶码的性质,证明了Z₄+vZ₄上长为n的自对偶码的Gray像是Z₄上长为2n的自对偶码,由此构造了Z₄上一些极优的类型I与类型Ⅱ自对偶码.     

Good Linear Codes from Quadratic Residue Codes over a Finite Non-Chain Ring

This paper is devoted to the study of quadratics residue codes and their extended codes over a finite non-chain ring. A class of Gray maps preserving the self-duality from the ring to the finite field are introduced. Some structural properties of quadratic residue codes and their extended codes are given. As an interesting applica-tion of these families of codes, some good linear codes are obtained by a special Gray map.     

Skew Cyclic Codes over a Non-chain Ring

We study skew cyclic codes over a non-chain ring, which generalizes our previous results in IEICE Trans. on Fundamentals of Electronic Communications and Computer Sciences, 2015. We describe generator polynomi-als of skew cyclic codes over this ring and investigate the structural properties of skew cyclic codes over the ring by a decomposition theorem. The generator polynomial of the dual code of a skew cyclic code are obtained. Moreover, the idempotent generators of skew cyclic codes are consid-ered. Some examples are also presented to illustrate the discussed results.     

环 F_2+uF_2+…+u~(κ-1)F_2上长为2~s的(1+u)-常循环码的距离分布

研究码字的距离分布是编码理论的一个重要研究方向。该文定义了环R=F2+uF2++uk-1F2上的Homogeneous重量,研究了环R上长为2s的(1+u)-常循环码的Hamming距离和Homogeneous距离。使用了有限环和域的理论,给出了环R上长为2s的(1+u)-常循环码和循环自对偶码的结构和码字个数。并利用该常循环码的结构,确定了环R上长为2s的(1+u)-常循环码的Hamming距离和Homogeneous距离分布。     

非主理想环F_p+vF_p上线性码的MacWilliams恒等式

研究了环F-p+vF_p上线性码的结构,证明了互为对偶的线性码的Gray象仍是互为对偶的线性码.定义了环F_p+vF_p上码的Lee重量、Hamming重量和广义对称重量分布计数器的概念,利用域F_p上线性码和对偶码重量分布的关系及Gray映射的性质,给出了该环上线性码及其对偶码之间的各种重量分布的Macwilliam...     

A novel construction of quantum ldpc codes based on cyclic classes of lines in euclidean geometries

The dual-containing (or self-orthogonal) formalism of Calderbank-Shor-Steane (CSS) codes provides a universal connection between a classical linear code and a Quantum Error-Correcting Code (QECC). We propose a novel class of quantum Low Density Parity Check (LDPC) codes constructed from cyclic classes of lines in Euclidean Geometry (EG). The corresponding constructed parity check matrix has quasi-cyclic structure that can be encoded flexibility, and satisfies the requirement of dual-containing quantum code. Taking the advantage of quasi-cyclic structure, we use a structured approach to construct Generalized Parity Check Matrix (GPCM). This new class of quantum codes has higher code rate, more sparse check matrix, and exactly one four-cycle in each pair of two rows. Experimental results show that the proposed quantum codes, such as EG(2,q)II-QECC, EG(3,q)II-QECC, have better performance than that of other methods based on EG, over the depolarizing channel and decoded with iterative decoding based on the sum-product decoding algorithm.     

环F4+uF4上线性码及其对偶码的Gray象

研究了环F4+uF4与域F4上的线性码,利用环F4+uF4上码C的Gray重量wG,Gray距离d G和(F4+uF4)n到F4 2n的Gray映射φ,证明了环F4+uF4上线性码C及其对偶码的Gray像φ(C)为F4上的线性码和对偶且dH G(φ(C))dG(C)。同时,给出了F4+uF4上循环码C的Gray像φ(C)为F4上的2-拟循环码。     

Algebraic lower bounds on the free distance of convolutional codes

A new module structure for convolutional codes is introduced and used to establish further links with quasi-cyclic and cyclic codes. The set of finite weight codewords of an (n,k) convolutional code over F_q is shown to be isomorphic to an F_q[x]-submodule of F_q ⁿ[x], where F_q ⁿ[x] is the ring of polynomials in indeterminate x over F_q ⁿ, an extension field of F_q. Such a module can then be associated with a quasi-cyclic code of index n and block length nL viewed as an F_q[x]-submodule of F_q ⁿ[x]/langx^L-1rang, for any positive integer L. Using this new module approach algebraic lower bounds on the free distance of a convolutional code are derived which can be read directly from the choice of polynomial generators. Links between convolutional codes and cyclic codes over the field extension F_q ⁿ are also developed and Bose-Chaudhuri-Hocquenghem (BCH)-type results are easily established in this setting. Techniques to find the optimal choice of the parameter L are outlined     

F4m上厄米特自正交常循环码

有限域上常循环码具有丰富的代数结构,其编译码电路容易实现,因而在信息传输实践中具有重要的应用.该文研究了一类有限域上任意长度的厄米特自正交常循环码的结构,给出了此类有限域上厄米特自正交常循环码的生成多项式与存在条件,确立了此类有限域上厄米特自正交常循环码的计数公式,并且利用此类有限域上偶长度的厄米特自正交常循环码构造了最优的量子码.     

环Fq+uFq++uk-1Fq上一类重根常循环码

记R=Fq+uFq++uk-1Fq,G=R[x]/,且是R中可逆元。定义了从Gn到Rtn的新的Gray映射,证明了J是G上长为n的线性的x-常循环码当且仅当(J)是R上长为tn的线性的-常循环码。使用有限环理论,获得了环R上长为pe的所有的(u-1)-常循环码的结构及其码字个数。特别地,获得了环F2m+uF上长为2e的(u-1)-常循环码的对偶码的结构及其码字个数。推广了环Z2a根负循环码的若干结果。