Multiset Deletion-Correcting Codes: Bounds and Constructions

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Main Authors: Kreindel, Avraham, Essayag, Isaac Barouch, Zabokritskiy, Aryeh Lev
Format: Preprint
Published: 2026
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author Kreindel, Avraham
Essayag, Isaac Barouch
Zabokritskiy, Aryeh Lev
author_facet Kreindel, Avraham
Essayag, Isaac Barouch
Zabokritskiy, Aryeh Lev
contents We study error-correcting codes in the space $\mathcal{S}_{n,q}$ of length-$n$ multisets over a $q$-ary alphabet, motivated by permutation channels in which ordering is completely lost and errors act solely by deletions of symbols, i.e., by reducing symbol multiplicities. Our focus is on the \emph{extremal deletion regime}, where the channel output contains $k=n-t$ symbols. In this regime, we establish tight or near-tight bounds on the maximum code size. In particular, we determine the exact optimal code sizes for $t=n-1$ and for $t=n-2$, develop a refined analysis for $t=n-3$, and derive a general recursive puncturing upper bound for $t=n-k$ via a reduction from parameters $(n,k)$ to $(n-1,k-1)$. On the constructive side, we completely resolve the binary multiset model: for all $t\ge1$ we determine $S_2(n,t)$ exactly and give an explicit optimal congruence-based construction. We then study single-deletion codes beyond the binary case, presenting general $q$-ary constructions and showing, via explicit small-parameter examples, that the natural modular construction need not be optimal for $q\ge3$. Finally, we present an explicit cyclic Sidon-type linear construction for general $(q,t)$ based on a single congruence constraint, with redundancy $\log_q\!\bigl(t(t+1)^{q-2}+1\bigr)$ and encoding and decoding complexity linear in the blocklength $n$.
format Preprint
id arxiv_https___arxiv_org_abs_2601_05636
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Multiset Deletion-Correcting Codes: Bounds and Constructions
Kreindel, Avraham
Essayag, Isaac Barouch
Zabokritskiy, Aryeh Lev
Information Theory
We study error-correcting codes in the space $\mathcal{S}_{n,q}$ of length-$n$ multisets over a $q$-ary alphabet, motivated by permutation channels in which ordering is completely lost and errors act solely by deletions of symbols, i.e., by reducing symbol multiplicities. Our focus is on the \emph{extremal deletion regime}, where the channel output contains $k=n-t$ symbols. In this regime, we establish tight or near-tight bounds on the maximum code size. In particular, we determine the exact optimal code sizes for $t=n-1$ and for $t=n-2$, develop a refined analysis for $t=n-3$, and derive a general recursive puncturing upper bound for $t=n-k$ via a reduction from parameters $(n,k)$ to $(n-1,k-1)$. On the constructive side, we completely resolve the binary multiset model: for all $t\ge1$ we determine $S_2(n,t)$ exactly and give an explicit optimal congruence-based construction. We then study single-deletion codes beyond the binary case, presenting general $q$-ary constructions and showing, via explicit small-parameter examples, that the natural modular construction need not be optimal for $q\ge3$. Finally, we present an explicit cyclic Sidon-type linear construction for general $(q,t)$ based on a single congruence constraint, with redundancy $\log_q\!\bigl(t(t+1)^{q-2}+1\bigr)$ and encoding and decoding complexity linear in the blocklength $n$.
title Multiset Deletion-Correcting Codes: Bounds and Constructions
topic Information Theory
url https://arxiv.org/abs/2601.05636