Cyclic and some Constacylic Codes Over the Ring Z4[u]/
In this paper, we study cyclic codes and constacyclic codes with shift constant (2 + u) over R = Z4 + uZ4, where u2 = 1. We determine the form of the generators of the cyclic codes over this ring and their spanning sets. Considering their Z4 images, we prove that the Z4-image of a (2 + u)-constacyclic code of odd length is a cyclic code over Z4. We also present many examples of cyclic codes over R whose Z4-images have better parameters than previously best-known Z4-linear codes.
Finite Fields and Their Applications