Linear Codes over Galois Ring $GR(p^2,r)$ Related to Gauss sums

TL;DR

This paper studies linear codes over Galois rings, deriving formulas for codeword weights using Gauss sums, and constructs nonlinear codes over finite fields with specific Hamming distances.

Contribution

It introduces new formulas for codeword weights over Galois rings and determines weight distributions and distances for certain classes of codes.

Findings

Derived formulas for N_beta(a) using Gauss sums.

Determined the complete Hamming weight distribution of C(G).

Constructed nonlinear codes over finite fields with two Hamming distances.

Abstract

Linear codes over finite rings become one of hot topics in coding theory after Hommons et al.([4], 1994) discovered that several remarkable nonlinear binary codes with some linear-like properties are the images of Gray map of linear codes over $Z_4$. In this paper we consider two series of linear codes $C(G)$ and $\widetilde{C}(G)$ over Galois ring $R=GR(p^2,r)$, where $G$ is a subgroup of $R^{(s)^*}$ and $R^{(s)}=GR(p^2,rs)$. We present a general formula on $N_\beta(a)$ in terms of Gauss sums on $R^{(s)}$ for each $a\in R$, where $N_\beta(a)$ is the number of a-component of the codeword $c_\beta\in C(G) (\beta\in R^{(s)})$ (Theorem 3.1). We have determined the complete Hamming weight distribution of $C(G)$ and the minimum Hamming distance of $\widetilde{C}(G)$ for some special G (Theorem 3.3 and 3.4). We show a general formula on homogeneous weight of codewords in $C(G)$ and $\widetilde{C}(G)$ (Theorem 4.5) for the special $G$ given in Theorem 3.4. Finally we obtained series of nonlinear codes over $\mathbb{F}_{q} \ (q=p^r)$ with two Hamming distance by using Gray map (Corollary 4.6).