Reducing Subpacketization in Device-to-Device Coded Caching via Heterogeneous File Splitting

TL;DR

This paper introduces a heterogeneous subpacketization framework for device-to-device coded caching, optimizing packet sizes to reduce subpacketization levels while maintaining optimal communication rates.

Contribution

It extends the packet type framework to heterogeneous packet sizes, enabling new caching schemes with significantly lower subpacketization in specific parameter regimes.

Findings

Achieves constant-factor reduction in subpacketization compared to existing schemes.

Constructs new D2D caching schemes for specific user and cache configurations.

Preserves optimal communication rate while reducing complexity.

Abstract

The packet type (PT)-based framework~\cite{zhang2026taming} provides a systematic and principled approach to designing device-to-device (D2D) coded caching schemes that achieve reduced \sbp while preserving the optimal communication rate. However, existing PT designs rely exclusively on homogeneous \sbp, where all packets have an identical size regardless of their types. This restriction limits the achievable \sbp reduction in certain parameter regimes. In this paper, we extend the PT framework to \emph{heterogeneous} \sbp, allowing packet sizes to vary across types under a refined type classification. The packet sizes, in conjunction with user grouping and multicast transmitter selection, are jointly optimized to minimize the overall \sbp level while preserving the optimal rate. Based on the heterogeneous PT framework, we construct a new class of D2D coded caching schemes for $(K, KM/N)=(2q+1, 2r)$ with $q,r \in \mathbb{N}_+$, where $K,N$ and $M$ denote the number of users, files and cache memory size, respectively. The proposed construction achieves a constant-factor reduction in \sbp compared to the Ji-Caire-Molisch (JCM) caching scheme~\cite{ji2016fundamental} and complements existing PT designs that are not applicable in this parameter regime.