Decentralized Hierarchical Coded Caching Over Heterogeneous Wireless Networks with Multi-level Popularity Content

Abstract

Decentralized hierarchical coded caching is studied with two layers of caches which users receive their demands through intermediate helpers from a main server. Coded caching in hierarchical model reduces rates in both layers and this scheme has been shown to be order-optimal when all contents are uniformly popular and there is no tension between the rates in each of two layers. We consider two-layer coded caching over heterogeneous wireless networks which can reduce the rates more effectively in both layers. The contents in our work are multi-level, based on the different levels of popularity. We use two different approaches in our hierarchical model: when the coded caching is provided within each layer and when it is provided across multiple layers. We consider combination of these two approaches and then optimize the proportion of using each approach to minimize the rates of the first layer and the second layer. We show that the rates in our scheme are much lower than the traditional hierarchical model. Moreover, common-memory method is introduced in two-layer network and is compared with the other schemes. It can be observed that the rates of common-memory method are lower than the previous hierarchical model but are higher than our proposed multi-level scheme. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.