Resolving the worst-User bottleneck of coded caching: Exploiting finite file sizes

Zhao, Hui; Bazco-Nogueras, Antonio; Elia, Petros
ITW 2020, IEEE International Workshop on Information Theory, April 11-15, 2021, Riva del Garda, Italy (Virtual Conference)

In this work, we address the worst-user bottleneck of coded caching, which is known to diminish any caching gains due to the fundamental requirement that the multicast
transmission rate should be limited by that of the worst channel among the served users. We consider the quasi-static Rayleigh fading Broadcast Channel, for which we first show that the coded caching gain of the XOR-based standard coded-caching scheme
completely vanishes in the low-SNR regime. Yet, we show that this collapse is not intrinsic to coded caching by presenting a novel scheme that can completely recover the caching gains. The scheme exploits an aspect that has remained unexploited: the
shared side information brought about by the file size constraint. The worst-user effect is dramatically ameliorated because it is replaced by the worst-group-of-users effect, where the users within a group have the same side information and the grouping is decided before the channel or the demands are known.

Riva del Garda
Systèmes de Communication
Eurecom Ref:
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