Rank-metric codes over arbitrary Galois extensions and rank analogues of Reed-Muller codes

TL;DR

This paper develops a framework for rank-metric codes over arbitrary Galois extensions, introduces rank analogues of Reed-Muller codes, and provides decoding algorithms and bounds for these codes.

Contribution

It extends rank-metric code theory to arbitrary Galois extensions, introduces rank Reed-Muller codes, and establishes bounds and decoding methods for these codes.

Findings

Bound on the dimension of zeroes of multivariate skew polynomials

Construction of rank Reed-Muller codes and their parameters

Connection between rank Reed-Muller codes and classical Reed-Muller codes in Kummer extensions

Abstract

This paper extends the study of rank-metric codes in extension fields $\mathbb{L}$ equipped with an arbitrary Galois group $G = \mathrm{Gal}(\mathbb{L}/\mathbb{K})$. We propose a framework for studying these codes as subspaces of the group algebra $\mathbb{L}[G]$, and we relate this point of view with usual notions of rank-metric codes in $\mathbb{L}^N$ or in $\mathbb{K}^{N\times N}$, where $N = [\mathbb{L} : \mathbb{K}]$. We then adapt the notion of error-correcting pairs to this context, in order to provide a non-trivial decoding algorithm for these codes. We then focus on the case where $G$ is abelian, which leads us to see codewords as elements of a multivariate skew polynomial ring. We prove that we can bound the dimension of the vector space of zeroes of these polynomials, depending of their degree. This result can be seen as an analogue of Alon-F\"uredi theorem -- and by means, of Schwartz-Zippel lemma -- in the rank metric. Finally, we construct the counterparts of Reed-Muller codes in the rank metric, and we give their parameters. We also show the connection between these codes and classical Reed-Muller codes in the case where $\mathbb{L}$ is a Kummer extension.