Spatially Correlated Content Caching for Device-to-Device Communications

TL;DR

This paper introduces a novel spatially correlated caching strategy for D2D networks, optimizing content placement to significantly improve cache hit probability under realistic constraints.

Contribution

The paper proposes the hard-core placement strategy inspired by Matérn point processes, optimizing exclusion radii for better content distribution in D2D networks.

Findings

HCP outperforms independent placement in cache hit probability.

HCP is especially effective for small cache sizes and communication ranges.

Optimized exclusion radii significantly improve content availability.

Abstract

We study optimal geographic content placement for device-to-device (D2D) networks in which each file's popularity follows the Zipf distribution. The locations of the D2D users (caches) are modeled by a Poisson point process (PPP) and have limited communication range and finite storage. Inspired by the Mat\'{e}rn hard-core (type II) point process that captures pairwise interactions between nodes, we devise a novel spatially correlated caching strategy called {\em hard-core placement} (HCP) such that the D2D nodes caching the same file are never closer to each other than the {\em exclusion radius}. The exclusion radius plays the role of a substitute for caching probability. We derive and optimize the exclusion radii to maximize the {\em hit probability}, which is the probability that a given D2D node can find a desired file at another node's cache within its communication range. Contrasting it with independent content placement, which is used in most prior work, our HCP strategy often yields a significantly higher cache hit probability. We further demonstrate that the HCP strategy is effective for small cache sizes and a small communication radius, which are likely conditions for D2D.