Some constructions of linearly optimal group codes

We continue here the research on (quasi)group codes over (quasi)group rings. We give some constructions of [n,n-3,3]_q-codes over F_q for n=2q and n=3q. These codes are linearly optimal, i.e. have maximal dimension among linear codes having a given length and distance. Although codes with such parameters are known, our main results state that we can construct such codes as (left) group codes. In the paper we use a construction of Reed-Solomon codes as ideals of the group ring F_qG where G is an elementary abelian group of order q.     

On the construction of perfect deletion-correcting codes using design theory

We consider a way to construct perfect codes capable of correcting 2 or more deletions using design-theory. As a starting point we use an (ordered) block design to construct a perfect deletion correcting code. Using this code we are able to construct more perfect deletion correcting codes over smaller or larger alphabets by removing or adding symbols in a smart way.In this way we are able to find all perfect 2-deletion correcting codes of length 4, and all perfect 3-deletion correcting codes of length 5 with different coordinates. The perfect 3-deletion correcting codes of length 5 with repeated symbols can be constructed for almost all possible alphabet sizesv, except forv=13, 14, 15, and 16, and forv7, 8 (mod 10),v17. For these values ofv we are neither able to prove the existence, nor the non-existence of perfect 3-deletion correcting codes of length 5 over an alphabet of sizev.     

Campopiano-type bounds in non-Hamming array coding

Campopiano [C.N. Campopiano, Bounds on burst error correcting codes, IRE Trans. IT-8 (1962) 257-259] obtained an upper bound for burst error correction in classical coding systems where codes are subsets/subspaces of the space , the space of all n-tuples with entries from a finite field F_q equipped with the Hamming metric. In [S. Jain, Bursts in m-metric array codes, Linear Algebra Appl., in press], the author introduced the notion of burst errors for m-metric array coding systems where m-metric array codes are subsets/subspaces of the space Mat_m×s(F_q), the linear space of all m × s matrices with entries from a finite field F_q, endowed with a non-Hamming metric and obtained some lower bounds for burst error correction. In this paper, we obtain various construction upper bounds on the parameters of m-metric array codes for the detection and correction of burst errors.     

On 2-dimensional insertion-deletion Reed-Solomon codes with optimal asymptotic error-correcting capability

Reed-Solomon codes have gained a lot of interest due to its encoding simplicity, well structuredness and list-decoding capability [6] in the classical setting. This interest also translates to other metric setting, including the insertion and deletion (insdel for short) setting which is used to model synchronization errors caused by positional information loss in communication systems. Such interest is supported by the construction of a deletion correcting algorithm of insdel Reed-Solomon code in [22] which is based on the Guruswami-Sudan decoding algorithm [6]. Nevertheless, there have been few studies [3] on the insdel error-correcting capability of Reed-Solomon codes.In this paper, we discuss a criterion for a 2-dimensional insdel Reed-Solomon codes to have optimal asymptotic error-correcting capabilities, which are up to their respective lengths. Then we provide explicit constructions of 2-dimensional insdel Reed-Solomon codes that satisfy the established criteria. The family of such constructed codes can then be shown to extend the family of codes with asymptotic error-correcting capability reaching their respective lengths provided in [3, Theorem 2] which provide larger error-correcting capability compared to those defined in [25].     

Maximal order codes over number fields

We present constructions of codes obtained from maximal orders over number fields. Particular cases include codes from algebraic number fields by Lenstra and Guruswami, codes from units of the ring of integers of number fields, and codes from both additive and multiplicative structures of maximal orders in central simple division algebras. The parameters of interest are the code rate and the minimum Hamming distance. An asymptotic study reveals several families of asymptotically good codes.     

Classes of optical orthogonal codes from arcs in root subspaces

We present new constructions for (n,w,λ) optical orthogonal codes (OOC) using techniques from finite projective geometry. In one case codewords correspond to (q-1)-arcs contained in Baer subspaces (and, in general, kth-root subspaces) of a projective space. In the other construction, we use sublines isomorphic to PG(2,q) lying in a projective plane isomorphic to PG(2,q^k), k>1. Our construction yields for each λ>1 an infinite family of OOCs which, in many cases, are asymptotically optimal with respect to the Johnson bound.     

New constructions for perfect hash families and related structures using combinatorial designs and codes

In this paper, we consider explicit constructions of perfect hash families using combinatorial methods. We provide several direct constructions from combinatorial structures related to orthogonal arrays. We also simplify and generalize a recursive construction due to Atici, Magliversas, Stinson and Wei [3]. Using similar methods, we also obtain efficient constructions for separating hash families which result in improved existence results for structures such as separating systems, key distribution patterns, group testing algorithms, cover‐free families and secure frameproof codes. © 2000 John Wiley & Sons, Inc. J Combin Designs 8:189–200, 2000     

Construction of deletion correcting codes using generalized Reed–Solomon codes and their subcodes

A code is n-deletion correcting if it is possible to correct any n deletion of symbols having occurred in transmission of codewords. In this paper, we present explicit constructions of n-deletion correcting codes for arbitrary values of n using generalized Reed–Solomon codes and their subcodes.      

Quantum twisted codes

A major contribution of [1] is a reduction of the problem of correcting errors in quantum computations to the construction of codes in binary symplectic spaces. This mechanism is known as the additive or stabilizer construction. We consider an obvious generalization of these quantum codes in the symplectic geometry setting and obtain general constructions using our theory of twisted BCH‐codes (also known as Reed–Solomon subspace subcodes). This leads to families of quantum codes with good parameters. Moreover, the generator matrices of these codes can be described in a canonical way. © 2000 John Wiley & Sons, Inc. J Combin Designs 8: 174–188, 2000     

Determining all indecomposable codes over some Hopf algebras

We determine all indecomposable codes over a class of Hopf algebras named Taft Algebras. We calculate dual codes and tensor products of these indecomposable codes and give applications of them.     

Algebraic geometric codes on anticanonical surfaces

Algebraic geometric codes (or AG codes) provide a way to correct errors that occur during the transmission of digital information. AG codes on curves have been studied extensively, but much less work has been done for AG codes on higher dimensional varieties. In particular, we seek good bounds for the minimum distance.We study AG codes on anticanonical surfaces coming from blow-ups of P² at points on a line and points on the union of two lines. We can compute the dimension of such codes exactly due to known results. For certain families of these codes, we prove an exact result on the minimum distance. For other families, we obtain lower bounds on the minimum distance.     

A class of group divisible 3‐designs and their applications

In this article, we first show that a group divisible 3‐design with block sizes from {4, 6}, index unity and group‐type 2^m exists for every integer m≥ 4 with the exception of m = 5. Such group divisible 3‐designs play an important role in our subsequent complete solution to the existence problem for directed H‐designs DH_λ(m, r, 4, 3)s. We also consider a way to construct optimal codes capable of correcting one deletion or insertion using the directed H‐designs. In this way, the optimal single‐deletion/insertion‐correcting codes of length 4 can be constructed for all even alphabet sizes. © 2008 Wiley Periodicals, Inc. J Combin Designs 17: 136–146, 2009     

Characterizations of pseudo-codewords of (low-density) parity-check codes

An important property of low-density parity-check codes is the existence of highly efficient algorithms for their decoding. Many of the most efficient, recent graph-based algorithms, e.g. message-passing iterative decoding and linear programming decoding, crucially depend on the efficient representation of a code in a graphical model. In order to understand the performance of these algorithms, we argue for the characterization of codes in terms of a so-called fundamental cone in Euclidean space. This cone depends upon a given parity-check matrix of a code, rather than on the code itself. We give a number of properties of this fundamental cone derived from its connection to unramified covers of the graphical models on which the decoding algorithms operate. For the class of cycle codes, these developments naturally lead to a characterization of the fundamental cone as the Newton polyhedron of the Hashimoto edge zeta function of the underlying graph.     

Fully Ramified Characters and Clifford Codes

In this article we study relations between groups and quantum error correcting codes. Groups of central type are used to construct quantum error correcting codes. Both stabilizer and Clifford codes can be derived from a construction involving this kind of groups. A more general construction of Clifford codes will be given and their correcting properties will be examined using group theoretical techniques.     

Riemann-Roch spaces of the Hermitian function field with applications to algebraic geometry codes and low-discrepancy sequences

This paper is concerned with two applications of bases of Riemann-Roch spaces. In the first application, we define the floor of a divisor and obtain improved bounds on the parameters of algebraic geometry codes. These bounds apply to a larger class of codes than that of Homma and Kim (J. Pure Appl. Algebra 162 (2001) 273). Then we determine explicit bases for large classes of Riemann-Roch spaces of the Hermitian function field. These bases give better estimates on the parameters of a large class of m-point Hermitian codes. In the second application, these bases are used for fast implementation of Xing and Niederreiter's method (Acta. Arith. 72 (1995) 281) for the construction of low-discrepancy sequences.     

ON THE CONSTRUCTION OF AUTHENTICATION CODES THAT PERMIT ARBITRATION OVER PROJECTIVE SPACES

A family of authentication codes with arbitration are constructed over projective spaces, the parameters and the probabilities of deceptions of the codes are also computed. In a special case, a perfect authentication code with arbitration is obtained.     

Quaternion orthogonal designs from complex companion designs

The success of applying generalized complex orthogonal designs as space-time block codes recently motivated the definition of quaternion orthogonal designs as potential building blocks for space-time-polarization block codes. This paper offers techniques for constructing quaternion orthogonal designs via combinations of specially chosen complex orthogonal designs. One technique is used to build quaternion orthogonal designs on complex variables for any even number of columns. A second related technique is applied to maximum rate complex orthogonal designs to generate an infinite family of quaternion orthogonal designs on complex variables such that the resulting designs have no zero entries. This second technique is also used to generate an infinite family of quaternion orthogonal designs defined over quaternion variables that display a regular redundancy. The proposed constructions are theoretically important because they provide the first known direct techniques for building infinite families of orthogonal designs over quaternion variables for any number of columns.     

A number theoretic formula and asymptotic optimality of cardinalities of BAD correcting codes

This paper presents a formula for the cardinality of a class of non-linear error correcting codes for Balanced Adjacent Deletions that are provided as an extension of standard deletion from the point of the view of Weyl groups. Furthermore, we show that the cardinality is approximately optimal over any single BAD correcting codes. In other words, the ratio of the cardinality of the code and that of maximum cardinality BAD correcting code converges to 1 for sufficiently large length.     

Existence of Perfect 3-Deletion-Correcting Codes

Bours [4] recently showed some constructions for perfect 2 and 3-deletion-correcting codes from combinatorial designs. He settled existence of perfect 2-deletion-correcting codes with words of length 4. However, the existence of perfect 3-deletion-correcting codes with words of length 5, or T^*(2, 5, v), remained unsettled for v 7, 8 (mod 10) and v = 13, 14, 15, 16. In this paper we provide new constructions for these codes from combinatorial designs, and show that a T^*(2, 5, v) exists for all v.     

Three Constructions of Authentication Codes with Perfect Secrecy

In this paper, we present three algebraic constructions of authentication codes with secrecy. The first and the third class are optimal. Some of the codes in the second class are optimal, and others in the second class are asymptotically optimal. All authentication codes in the three classes provide perfect secrecy.