Cache-enabled small cell networks: modeling and tradeoffs.

Ejder Baştuǧ,Marios Kountouris,Mehdi Bennis,Mérouane Debbah

doi:10.1186/s13638-015-0250-4

Abstract

We consider a network model where small base stations (SBSs) have caching capabilities as a means to alleviate the backhaul load and satisfy users’ demand. The SBSs are stochastically distributed over the plane according to a Poisson point process (PPP) and serve their users either (i) by bringing the content from the Internet through a finite rate backhaul or (ii) by serving them from the local caches. We derive closed-form expressions for the outage probability and the average delivery rate as a function of the signal-to-interference-plus-noise ratio (SINR), SBS density, target file bitrate, storage size, file length, and file popularity. We then analyze the impact of key operating parameters on the system performance. It is shown that a certain outage probability can be achieved either by increasing the number of base stations or the total storage size. Our results and analysis provide key insights into the deployment of cache-enabled small cell networks (SCNs), which are seen as a promising solution for future heterogeneous cellular networks.

Highlights

Increasing traffic demand from mobile users due to the rich media applications, video streaming, and social networks [1] is pushing mobile operators to make their mobile cellular networks evolve continuously. small cell network [3,4] and their integration with WiFi [5], heterogeneous network [6], together with many other ideas from both industry and academia, have started being deployed and integrated in current cellular networks
By coupling the caching problem with a physical layer in this way and relying on recent results from [24], we show that a certain outage probability can be achieved either by 1) increasing number of small base station while the total storage size budged is fixed or 2) increasing the total storage size while the number of small base station is fixed
If a requested file is in the cache of the serving small base station and if the downlink rate is higher than the file bitrate T, we expect the outage probability to be close to zero

Summary

Introduction

Increasing traffic demand from mobile users due to the rich media applications, video streaming, and social networks [1] is pushing mobile operators to make their mobile cellular networks evolve continuously (see longterm evolution [2]). small cell network [3,4] and their integration with WiFi [5], heterogeneous network [6], together with many other ideas from both industry and academia, have started being deployed and integrated in current cellular networks. If a requested file is in the cache of the serving small base station (the limited backhaul is not used) and if the downlink rate is higher than the file bitrate T (the user does not observe any interruption during the playback of the file), we expect the outage probability to be close to zero Given this explanation and the assumptions made, we state the following theorem for outage probability. If the downlink rate is higher than T but the requested file does not exist in the local cache of the tagged small base station, the delivery rate will be limited by the backhaul link capacity C(λ), for which we assume that C(λ) < T Given this definition for the delivery rate, we state the following theorem. Interference is Rayleigh fading, which in turn gi ∼ Exponential(μ)

The capacity of backhaul links is given by:

Conclusions

D Proof of Proposition 2