Coding, Multicast, and Cooperation for Cache- Enabled Heterogeneous Small Cell Networks

Jialing Liao,Zhongbin Zheng,Yangyang Zhang,Kun Yang,Kai-Kit Wong

doi:10.1109/twc.2017.2731967

Abstract

Caching at the wireless edge is a promising approach to dealing with massive content delivery in heterogeneous wireless networks, which have high demands on backhaul. In this paper, a typical cache-enabled small cell network under heterogeneous file and network settings is considered using maximum distance separable (MDS) codes for content restructuring. Unlike those in the literature considering online settings with the assumption of perfect user request information, we estimate the joint user requests using the file popularity information and aim to minimize the long-term average backhaul load for fetching content from external storage subject to the overall cache capacity constraint by optimizing the content placement in all the cells jointly. Both multicast-aware caching and cooperative caching schemes with optimal content placement are proposed. In order to combine the advantages of multicast content delivery and cooperative content sharing, a compound caching technique, which is referred to as multicast-aware cooperative caching, is then developed. For this technique, a greedy approach and a multicast-aware in-cluster cooperative approach are proposed for the small-scale networks and large-scale networks, respectively. Mathematical analysis and simulation results are presented to illustrate the advantages of MDS codes, multicast, and cooperation in terms of reducing the backhaul requirements for cache-enabled small cell networks.

Highlights

T HE concept of caching has recently been introduced to the physical layer for wireless content delivery networks (CDNs) to reduce peak-time traffic, latency as well as Manuscript received January 4, 2017; revised May 15, 2017 and July 13, 2017; accepted July 15, 2017
We evaluate that the total number of different π j and Kπ j will be as high as 2K
We evaluate the performances of the proposed coded caching schemes in terms of the average backhaul load as well as the user attrition (UA) cost via computer simulations

Summary

Introduction

T HE concept of caching has recently been introduced to the physical layer for wireless content delivery networks (CDNs) to reduce peak-time traffic, latency as well as Manuscript received January 4, 2017; revised May 15, 2017 and July 13, 2017; accepted July 15, 2017. Date of publication August 4, 2017; date of current version October 9, 2017. The associate editor coordinating the review of this paper and approving it for publication was J. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. The main idea of caching is to pre-fetch popular content at the network edge, either at the base stations (BSs) or/and user terminals (UTs) to bring the content much closer to the users. One needs to address, e.g., where to cache, how to cache, the corresponding transmission policy, and so on

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Conclusion