4,707 research outputs found
On the equivalence of cyclic and quasi-cyclic codes over finite fields
This paper studies the equivalence problem for cyclic codes of length and quasi-cyclic codes of length . In particular, we generalize the results of Huffman, Job, and Pless (J. Combin. Theory. A, 62, 183--215, 1993), who considered the special case . This is achieved by explicitly giving the permutations by which two cyclic codes of prime power length are equivalent. This allows us to obtain an algorithm which solves the problem of equivalency for cyclic codes of length in polynomial time. Further, we characterize the set by which two quasi-cyclic codes of length can be equivalent, and prove that the affine group is one of its subsets
Construction of quasi-cyclic self-dual codes
There is a one-to-one correspondence between -quasi-cyclic codes over a
finite field and linear codes over a ring . Using this correspondence, we prove that every
-quasi-cyclic self-dual code of length over a finite field
can be obtained by the {\it building-up} construction, provided
that char or , is a prime , and
is a primitive element of . We determine possible weight
enumerators of a binary -quasi-cyclic self-dual code of length
(with a prime) in terms of divisibility by . We improve the result of
[3] by constructing new binary cubic (i.e., -quasi-cyclic codes of length
) optimal self-dual codes of lengths (Type I), 54 and
66. We also find quasi-cyclic optimal self-dual codes of lengths 40, 50, and
60. When , we obtain a new 8-quasi-cyclic self-dual code
over and a new 6-quasi-cyclic self-dual code over
. When , we find a new 4-quasi-cyclic self-dual
code over and a new 6-quasi-cyclic self-dual code
over .Comment: 25 pages, 2 tables; Finite Fields and Their Applications, 201
One-Generator Quasi-Abelian Codes Revisited
The class of 1-generator quasi-abelian codes over finite fields is revisited.
Alternative and explicit characterization and enumeration of such codes are
given. An algorithm to find all 1-generator quasi-abelian codes is provided.
Two 1-generator quasi-abelian codes whose minimum distances are improved from
Grassl's online table are presented
The Permutation Groups and the Equivalence of Cyclic and Quasi-Cyclic Codes
We give the class of finite groups which arise as the permutation groups of
cyclic codes over finite fields. Furthermore, we extend the results of Brand
and Huffman et al. and we find the properties of the set of permutations by
which two cyclic codes of length p^r can be equivalent. We also find the set of
permutations by which two quasi-cyclic codes can be equivalent
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