Partition-balanced families of codes and asymptotic enumeration in coding theory

JOURNAL OF COMBINATORIAL THEORY SERIES A

卷:171

Article

Byrne, Eimear¹  Ravagnani, Alberto¹ 

[1] Univ Coll Dublin, Sch Math & Stat, Belfield, Ireland

关键词: Asymptotic enumeration;    Partition-balanced family;    Error-correcting code;    Density function;    Hamming metric;    Rank metric;    MDS code;    MRD code;   

DOI  :  10.1016/j.jcta.2019.105169

来源: Elsevier

【 摘 要 】

We introduce the class of partition-balanced families of codes, and show how to exploit their combinatorial invariants to obtain upper and lower bounds on the number of codes that have a prescribed property. In particular, we derive precise asymptotic estimates on the density functions of several classes of codes that are extremal with respect to minimum distance, covering radius, and maximality. The techniques developed in this paper apply to various distance functions, including the Hamming and the rank metric distances. Applications of our results show that, unlike the F-qm-linear MRD codes, the F-q-linear MRD codes are not dense in the family of codes of the same dimension. More precisely, we show that the density of F-q-linear MRD codes in F-q(nxm) in the set of all matrix codes of the same dimension is asymptotically at most 1/2, both as q -> +infinity and as m -> +infinity. We also prove that MDS and F-qm-linear MRD codes are dense in the family of maximal codes. Although there does not exist a direct analogue of the redundancy bound for the covering radius of Fq-linear rank metric codes, we show that a similar bound is satisfied by a uniformly random matrix code with high probability. In particular, we prove that codes meeting this bound are dense. Finally, we compute the average weight distribution of linear codes in the rank metric, and other parameters that generalize the total weight of a linear code. (C) 2019 Published by Elsevier Inc.

【 授权许可】

Free