Cyclic and some constacyclic codes over the ring Z(4)[u]/< u(2)-1 >

Abstract

In this paper, we study cyclic codes and constacyclic codes with shift constant (2 + u) over R = Z(4) + uZ(4), where u(2) = 1. We determine the form of the generators of the cyclic codes over this ring and their spanning sets. Considering their Z(4) images, we prove that the Z(4)-image of a (2 + u)-constacyclic code of odd length is a cyclic code over Z(4). We also present many examples of cyclic codes over R whose Z(4)-images have better parameters than previously best-known Z(4)-linear codes. (C) 2015 Elsevier Inc. All rights reserved.