A code is -quasi-cyclic ( -QC) if there is an integer such that cyclic shift of a codeword by -positions is also a codeword. For = 1, cyclic codes are obtained. A dyadic code is a code which is closed under all dyadic shifts. An -QC dyadic ( -QCD) code is one which is both -QC and dyadic. QCD codes with = 1 give codes that are cyclic and dyadic (CD). In this correspondence, we obtain a simple c...

We completely characterize possible indices of quasi-cyclic subcodes in a cyclic code for a very broad class of cyclic codes. We present enumeration results for quasi-cyclic subcodes of a fixed index and show that the problem of enumeration is equivalent to enumeration of certain vector subspaces in finite fields. In particular, we present enumeration results for quasi-cyclic subcodes of the si...

A parity-check matrix for a q -ary repeated-root cyclic code is derived using the Hasse derivative. Then the min imum distance of a q-ary repeated-root cyclic code C is expressecin terms of the min imum distance of a certain simple-root cyclic code C that is determined by C. With the help of this result, several binary repeated-root cyclic codes of lengths up to n = 62 are shown to contain the ...

Let GF (q) denote the Galois field of q elements, and let V (n, q) denote the vector space of all ordered n-tuples over GF (q). The number of nonzero positions in a vector x ∈ V (n, q) is called the Hamming weight wt(x) of x. The Hamming distance d(x,y) between two vectors x,y ∈ V (n, q) is defined by d(x,y) = wt(x − y). A linear code C of length n and dimension k over GF (q) is a k-dimensional...

LCD codes are linear codes that intersect with their dual trivially. Quasi-cyclic codes that are LCD are characterized and studied by using their concatenated structure. Some asymptotic results are derived. Hermitian LCD codes are introduced to that end and their cyclic subclass is characterized. Constructions of QCCD codes from codes over larger alphabets are given.

Let R = Zq + uZq, where q = p and u = 0. In this paper, some structural properties of cyclic codes and quasi-cyclic (QC) codes over the ring R are considered. A QC code of length ln with index l over R is viewed both as in the conventional row circulant form and also as an R[x]/(x − 1)-submodule of GR(R, l)[x]/(x − 1), where GR(R, l) is the Galois extension ring of degree l over R. A necessary ...

Let R = Zq + uZq, where q = p s and u = 0. In this paper, some structural properties of cyclic codes and quasi-cyclic (QC) codes over the ring R are considered. A QC code of length ln with index l over R is viewed both as in the conventional row circulant form and also as an R[x]/(xn − 1)-submodule of GR(R, l)[x]/(xn − 1), where GR(R, l) is the Galois extension ring of degree l over R. A necess...

A (left) group code of length n is a linear code which is the image of a (left) ideal of a group algebra via an isomorphism FG→ F which maps G to the standard basis of F. Many classical linear codes have been shown to be group codes. In this paper we obtain a criterion to decide when a linear code is a group code in terms of its intrinsical properties in the ambient space F, which does not assu...

A new Gray map between codes over F2 +uF2 +uF2 +uF2 + ....+ uF2 and codes over F2 is defined. It is proved that the Gray image of a linear (1− um)-cyclic code over F2 + uF2 + uF2 + uF2 + .... + uF2 of length n is a binary distance invariant quasi-cylic code of index 2m−1 and length 2mn. It is also proved that if n is odd, then every code of length 2mn over F2 which is the Gray image of a linear...

The punctured binary Reed-Muller code is cyclic and was generalized into the punctured generalized ReedMuller code over GF(q) in the literature. The major objective of this paper is to present another generalization of the punctured binary Reed-Muller code. Another objective is to construct a family of reversible cyclic codes that are related to the newly generalized Reed-Muller codes. Index Te...