Backhaul-Based Cooperative Caching in 5G Small Cell Network

Abstract

As mobile devices become more and more ubiquitous mobile traffic demands are exponentially increasing It is forecasted that worldwide mobile data traffic would increase 7-fold between 2016 and 2021 To deal with such challenge caching is considered as an effective way to reduce redundant transmission With popular contents stored at base stations in mobile networks the requested contents can be directly delivered to users without fetching from remote servers and thus the end-to-end latency is shortened However the cache gain is limited by cache capacity Hence the idea of cooperative caching is coming up Cooperative caching allows the cache storage to be used more efficiently and increases cache hit rate to further reduce the downloading latency Recent researches assume that a mobile user can be served by multiple small cell base stations (SBSs) simultaneously yet this hypothesis requires costly re-design of the infrastructure’s physical layer Besides spectral efficiency inevitably degrades due to larger transmission distances between mobile users and SBSs In this thesis we propose a backhaul-based cooperative caching scheme by grouping several SBSs into a cluster and cooperating through wired interfaces By utilizing backhaul facilities the proposed scheme does not degrade the spectral efficiency and needs no additional nodes We first formulate a delay minimization problem for cooperative caching and then propose a greedy algorithm to obtain the near-optimal content placement The proposed scheme can reduce downloading delay by 16 2% compared to non-cooperative caching at SBSs and by 9 6% compared with cooperative caching at SBSs in existing works We also explore the impact on end-to-end latency under different simulation parameters such as SBSs distribution density cluster size and the skewness of the popularities of requested contents

Date of Award	2018 Apr 24
Original language	English
Supervisor	Meng-Hsun Tsai (Supervisor)