Constructions of cyclic constant dimension codes

Subspace codes and particularly constant dimension codes have attracted much attention in recent years due to their applications in random network coding. As a particular subclass of subspace codes, cyclic subspace codes have additional properties that can be applied efficiently in encoding and decoding algorithms. It is desirable to find cyclic constant dimension codes such that both the code sizes and the minimum distances are as large as possible. In this paper, we explore the ideas of constructing cyclic constant dimension codes proposed in Ben-Sasson et al. (IEEE Trans Inf Theory 62(3):1157–1165, 2016) and Otal and Özbudak (Des Codes Cryptogr, doi: 10.1007/s10623-016-0297-1, 2016) to obtain further results. Consequently, new code constructions are provided and several previously known results in [2] and [17] are extended.     

常维码的一个构造性下界

推广了Etzion和Vardy关于常维码的结论（Etzion T,Vardy A.Error-correcting codes in projective space.IEEE Transactions on Information Theory,2011,57（2）：1165-1173）,给出了一般情况下常维码的一个构造性下界.     

A family of linear codes from constant dimension subspace codes

Designs, Codes and Cryptography - Linear codes with good parameters have wide applications in secret sharing schemes, authentication codes, association schemes, consumer electronics and...     

Johnson type bounds on constant dimension codes

Very recently, an operator channel was defined by Koetter and Kschischang when they studied random network coding. They also introduced constant dimension codes and demonstrated that these codes can be employed to correct errors and/or erasures over the operator channel. Constant dimension codes are equivalent to the so-called linear authentication codes introduced by Wang, Xing and Safavi-Naini when constructing distributed authentication systems in 2003. In this paper, we study constant dimension codes. It is shown that Steiner structures are optimal constant dimension codes achieving the Wang-Xing-Safavi-Naini bound. Furthermore, we show that constant dimension codes achieve the Wang-Xing-Safavi-Naini bound if and only if they are certain Steiner structures. Then, we derive two Johnson type upper bounds, say I and II, on constant dimension codes. The Johnson type bound II slightly improves on the Wang-Xing-Safavi-Naini bound. Finally, we point out that a family of known Steiner structures is actually a family of optimal constant dimension codes achieving both the Johnson type bounds I and II.      

On constant composition codes

A constant composition code over a k-ary alphabet has the property that the numbers of occurrences of the k symbols within a codeword is the same for each codeword. These specialize to constant weight codes in the binary case, and permutation codes in the case that each symbol occurs exactly once. Constant composition codes arise in powerline communication and balanced scheduling, and are used in the construction of permutation codes. In this paper, direct and recursive methods are developed for the construction of constant composition codes.     

On the binary projective codes with dimension 6

All binary projective codes of dimension up to 6 are classified. Information about the number of the codes with different minimum distances and automorphism group orders is given.     

On the extendability of code isometries

A block codeC F ⁿ is calledmetrically rigid, if every isometry: CF ⁿ with respect to theHamming metric is extendable to an isometry of the whole spaceF ⁿ . The metrical rigidity of some classes of codes is discussed.Dedicated to Helmut Karzel on the occasion of his 70th birthdayResearch supported by the Russian Foundation of Fundamental Research (Grant no. 97-01-01104)Research supported by the Russian Foundation of Fundamental Research (Grants no. 96-01-01800, 97-01-01075)     

On the extendability of steiner t-designs

Necessary and sufficient conditions for the extendability of residual designs of Steiner systems S(t,t + 1,v) are studied. In particular, it is shown that a residual design with respect to a single point is uniquely extendable, and the extendability of a residual design with respect to a pair of points is equivalent to a bipartition of the block graph of a related design. © 1993 John Wiley & Sons, Inc.     

Some new results on dimension and Bose distance for various classes of BCH codes

In this paper, we give the dimension and the minimum distance of two subclasses of narrow-sense primitive BCH codes over ${\mathbb{F}}_q$ with designed distance $\delta =a{q}^{m-1}-1(\text{resp. }\delta =a\frac{q^m-1}{q-1})$ for all $1\le a\le q-1$, where q is a prime power and $m>1$ is a positive integer. As a consequence, we obtain an affirmative answer to two conjectures proposed by C. Ding in 2015. Furthermore, using the previous part, we extend some results of Yue and Hu [16], and we give the dimension and, in some cases, the Bose distance for a large designed distance in the range $[a\frac{q^m-1}{q-1},a\frac{q^m-1}{q-1}+T]$ for $0\le a\le q-2$, where $T=q^{\frac{m+1}{2}}-1$ if m is odd, and $T=2q^{\frac{m}{2}}-1$ if m is even.     

On the minimum average distance of binary constant weight codes

Let β(n,M,w) denote the minimum average Hamming distance of a binary constant weight code with length n, size M and weight w. In this paper, we study the problem of determining β(n,M,w). Using the methods from coding theory and linear programming, we derive several lower bounds on the average Hamming distance of a binary constant weight code. These lower bounds enable us to determine the exact value for β(n,M,w) in several cases.     

On the second greedy weight for linear codes of dimension 3

The difference g₂−d₂ for a q-ary linear [n,3,d] code C is studied. Here d₂ is the second generalized Hamming weight, that is, the smallest size of the support of a 2-dimensional subcode of C; and g₂ is the second greedy weight, that is, the smallest size of the support of a 2-dimensional subcode of C which contains a codeword of weight d. For codes of dimension 3, it is shown that the problem is essentially equivalent to finding certain weighting of the points in the projective plane, and weighting which give the maximal value of g₂−d₂ are determined in almost all cases. In particular max(g₂−d₂) is determined in all cases for q⩽9.     

On wedge extendability of CR-meromorphic functions

In this article, we consider metrically thin singularities E of the solutions of the tangential Cauchy-Riemann operators on a -smooth embedded Cauchy-Riemann generic manifold M (CR functions on ) and more generally, we consider holomorphic functions defined in wedgelike domains attached to . Our main result establishes the wedge- and the L¹-removability of E under the hypothesis that the -dimensional Hausdorff volume of E is zero and that M and are globally minimal. As an application, we deduce that there exists a wedgelike domain attached to an everywhere locally minimal M to which every CR-meromorphic function on M extends meromorphically. Received: 7 September 2000; in final form: 20 December 2001 / Published online: 6 August 2002