Spatial Concentration of Caching in Wireless Heterogeneous Networks

TL;DR

This paper introduces a decentralized caching scheme called {b3}-exclusion cache placement (GEC) for wireless heterogeneous networks, which reduces cache size variance and improves efficiency by controlling content redundancy based on spatial interactions.

Contribution

The paper presents GEC, a novel caching policy that leverages pairwise interactions and negative dependence to achieve spatially balanced caching with reduced storage variance.

Findings

GEC guarantees reduced variance in cache storage size compared to existing methods.

GEC achieves approximately 3x and 2x reduction in cache size for uniform traffic.

GEC performs even better under realistic non-uniform urban traffic scenarios.

Abstract

We propose a decentralized caching policy for wireless heterogeneous networks that makes content placement decisions based on pairwise interactions between cache nodes. We call our proposed scheme {\gamma}-exclusion cache placement (GEC), where a parameter {\gamma} controls an exclusion radius that discourages nearby caches from storing redundant content. GEC takes into account item popularity and the nodes' caching priorities and leverages negative dependence to relax the classic 0-1 knapsack problem to yield spatially balanced sampling across caches. We show that GEC guarantees a better concentration (reduced variance) of the required cache storage size than the state of the art, and that the cache size constraints can be satisfied with high probability. Given a cache hit probability target, we compare the 95\% confidence intervals of the required cache sizes for three caching schemes: (i) independent placement, (ii) hard exclusion caching (HEC), and (iii) the proposed GEC approach. For uniform spatial traffic, we demonstrate that GEC provides approximately a 3x and 2x reduction in required cache size over (i) and (ii), respectively. For non-uniform spatial traffic based on realistic peak-hour variations in urban scenarios, the gains are even greater.