Coded Caching Does Not Generally Benefit From Selfish Caching

TL;DR

This paper investigates how selfish caching, where users cache only content of personal interest, impacts the efficiency of coded caching, revealing that it generally results in worse performance than standard caching.

Contribution

The paper introduces a new information-theoretic converse for symmetric selfish coded caching, showing it typically underperforms compared to standard coded caching.

Findings

Selfish caching leads to higher load than standard caching.

Symmetric FDS structures influence caching performance.

Selfish caching does not generally benefit from coded caching techniques.

Abstract

In typical coded caching scenarios, the content of a central library is assumed to be of interest to all receiving users. However, in a realistic scenario the users may have diverging interests which may intersect to various degrees. What happens for example if each file is of potential interest to, say, $40\,\%$ of the users and each user has potential interest in $40\,\%$ of the library? What if then each user caches selfishly only from content of potential interest? In this work, we formulate the symmetric selfish coded caching problem, where each user naturally makes requests from a subset of the library, which defines its own file demand set (FDS), and caches selfishly only contents from its own FDS. For the scenario where the different FDSs symmetrically overlap to some extent, we propose a novel information-theoretic converse that reveals, for such general setting of symmetric FDS structures, that selfish coded caching yields a load performance which is strictly worse than that in standard coded caching.