On the number of $q$-ary quasi-perfect codes with covering radius 2

TL;DR

This paper constructs a large family of nonlinear $q$-ary quasi-perfect codes with covering radius 2, demonstrating an exponential growth in the number of nonequivalent codes as length increases.

Contribution

It introduces a new family of nonlinear quasi-perfect codes with specific parameters and proves the existence of an exponentially large number of such codes for large lengths.

Findings

More than $q^{q^{cn}}$ nonequivalent codes exist for large $n$

Codes have length $n = q^m$ and size $q^{n - m - 1}$

Results hold for all sufficiently large $n$ and prime power $q \

Abstract

In this paper we present a family of $q$-ary nonlinear quasi-perfect codes with covering radius 2. The codes have length $n = q^m$ and size $ M = q^{n - m - 1}$ where $q$ is a prime power, $q \geq 3$, $m$ is an integer, $m \geq 2$. We prove that there are more than $q^{q^{cn}}$ nonequivalent such codes of length $n$, for all sufficiently large $n$ and a constant $c = \frac{1}{q} - \varepsilon$.