Hierarchical Coded Caching in High Memory Regime with Coded Placement

TL;DR

This paper introduces two novel hierarchical coded caching schemes with coded placement that outperform existing methods at specific memory points, especially in high memory regimes, by optimizing bandwidth usage in a two-layer network.

Contribution

The paper proposes two new coded caching schemes based on coded placement tailored for high memory regimes in hierarchical networks, improving bandwidth efficiency at certain memory configurations.

Findings

Proposed schemes outperform existing schemes at specific memory points.

The schemes are effective in high memory regimes with coded placement.

Comparison using composite rate shows bandwidth improvements.

Abstract

We consider a two-layer hierarchical coded caching network where a server with a library of $N$ files is connected to $K_1$ mirrors, each having a cache memory of size $M_1$. Each mirror is further connected to $K_2$ users, each equipped with a dedicated cache of size $M_2$. In this paper, we propose two distinct coded caching schemes based on coded placement, corresponding to two distinct memory pairs, \( (M_1, M_2) \). We show that the proposed schemes outperform the existing schemes at these memory points given by the proposed schemes for smaller values of $K_2$. In setups where mirrors are positioned near each other, avoiding signal interference is crucial. This can be ensured by having all mirrors transmit using orthogonal carrier frequencies. To compare our schemes with existing ones, we used the composite rate metric, which accurately represents the total bandwidth utilized in such setups. The composite rate is given by $\overline{R} = R_1 + K_1 R_2$, where $R_1$ is the rate from the server to the mirrors, and $R_2$ is the rate from the mirrors to the users, with respect to $M_1$ and $M_2$.