Strong Singleton-Like Bounds, Quasi-Perfect Codes and Distance-Optimal Codes in the Sum-Rank Metric
Chao Liu, Hao Chen, Qinqin Ji, Ziyan Xie, Dabin Zheng
TL;DR
This work advances the theory of sum-rank codes by establishing covering-code based constructions that yield new upper bounds on size and block-lengths, and by proving strong Singleton-like bounds that outperform classical bounds for large block lengths. It introduces infinite families of quasi-perfect sum-rank codes, distance-optimal cyclic codes with minimum sum-rank distance four, and almost MSRD codes with larger block lengths, all tied to concrete cyclic/Hamming constructions and BCH-based arguments. Additionally, the paper develops Plotkin-sums for sum-rank codes to produce further distance-optimal instances, including binary constructions with larger block lengths. Collectively, these results deepen the toolkit for designing robust sum-rank codes in multishot network coding, space-time coding, and distributed storage, with practical impact in achieving tight distance and covering properties over diverse matrix sizes.
Abstract
Codes in the sum-rank metric have received many attentions in recent years, since they have wide applications in the multishot network coding, the space-time coding and the distributed storage. In this paper, by constructing covering codes in the sum-rank metric from covering codes in the Hamming metric, we derive new upper bounds on sizes, the covering radii and the block length functions of codes in the sum-rank metric. As applications, we present several strong Singleton-like bounds that are tighter than the classical Singleton-like bound when block lengths are large. In addition, we give the explicit constructions of the distance-optimal sum-rank codes of matrix sizes $s\times s$ and $2\times 2$ with minimum sum-rank distance four respectively by using cyclic codes in the Hamming metric. More importantly, we present an infinite families of quasi-perfect $q$-ary sum-rank codes with matrix sizes $2\times m$. Furthermore, we construct almost MSRD codes with larger block lengths and demonstrate how the Plotkin sum can be used to give more distance-optimal sum-rank codes.
