On structure and distances of some classes of repeated-root constacyclic codes over Galois rings

摘要

The structure of lambda-constacyclic codes of length 2(s) over the Galois ring GR(2(a), m) is obtained, for any unit A of the form 4z - 1, z is an element of GR(2a, m). The duals codes and necessary and sufficient conditions for the existence of a self dual lambda-constacyclic code are provided. Among others, this structure is used to establish the Hamming, homogeneous, and Rosenbloom-Tsfasman distances, and Rosenbloom-Tsfasman weight distribution of all such constacyclic codes. (C) 2016 Elsevier Inc. All rights reserved.