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Deghel M.,University Paris - Sud | Bastug E.,Large Networks and Systems Group LANEAS | Assaad M.,University Paris - Sud | Debbah M.,University Paris - Sud | Debbah M.,Huawei
IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC | Year: 2015

In this contribution, we jointly investigate the benefits of caching and interference alignment (IA) in multiple-input multiple-output (MIMO) interference channel under limited backhaul capacity. In particular, total average transmission rate is derived as a function of various system parameters such as backhaul link capacity, cache size, number of active transmitter-receiver pairs as well as the quantization bits for channel state information (CSI). Given the fact that base stations are equipped both with caching and IA capabilities and have knowledge of content popularity profile, we then characterize an operational regime where the caching is beneficial. Subsequently, we find the optimal number of transmitter-receiver pairs that maximizes the total average transmission rate. When the popularity profile of requested contents falls into the operational regime, it turns out that caching substantially improves the throughput as it mitigates the backhaul usage and allows IA methods to take benefit of such limited backhaul. © 2015 IEEE. Source

Bastug E.,Large Networks and Systems Group LANEAS | Bennis M.,University of Oulu | Debbah M.,Large Networks and Systems Group LANEAS | Debbah M.,Huawei
2015 13th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, WiOpt 2015 | Year: 2015

Locally caching contents at the network edge constitutes one of the most disruptive approaches in 5G wireless networks. Reaping the benefits of edge caching hinges on solving a myriad of challenges such as how, what and when to strategically cache contents subject to storage constraints, traffic load, unknown spatio-temporal traffic demands and data sparsity. Motivated by this, we propose a novel transfer learning-based caching procedure carried out at each small cell base station. This is done by exploiting the rich contextual information (i.e., users' content viewing history, social ties, etc.) extracted from device-to-device (D2D) interactions, referred to as source domain. This prior information is incorporated in the so-called target domain where the goal is to optimally cache strategic contents at the small cells as a function of storage, estimated content popularity, traffic load and backhaul capacity. It is shown that the proposed approach overcomes the notorious data sparsity and cold-start problems, yielding significant gains in terms of users' quality-of-experience (QoE) and backhaul offloading, with gains reaching up to 22% in a setting consisting of four small cell base stations. © 2015 IFIP. Source

Bastug E.,Large Networks and Systems Group LANEAS | Bennis M.,University of Oulu | Kountouris M.,Large Networks and Systems Group LANEAS | Debbah M.,Large Networks and Systems Group LANEAS | Debbah M.,Huawei
Eurasip Journal on Wireless Communications and Networking | Year: 2015

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. © 2015, Baştuǧet al.; licensee Springer. Source

Deghel M.,CentraleSupelec | Deghel M.,Large Networks and Systems Group LANEAS | Assaad M.,CentraleSupelec | Debbah M.,Large Networks and Systems Group LANEAS | Debbah M.,Huawei
IEEE International Symposium on Information Theory - Proceedings | Year: 2015

This paper characterizes the performance of IA technique taking into account the dynamic traffic pattern and the probing/feedback cost. We consider a TDD system where transmitters acquire their CSI (Channel State Information) by decoding the pilot sequences sent by the receivers. Since global CSI knowledge is required for IA, the transmitters have also to exchange their estimated CSIs over a backhaul of limited capacity. Under this setting, we characterize in this paper the stability region of the system and provide a probing algorithm that achieves the max stability region. In addition, we compare the stability region of IA to the one achieved by a TDMA system where each transmitter applies a simple ZF (Zero Forcing technique). © 2015 IEEE. Source

Perabathini B.,Large Networks and Systems Group LANEAS | Perabathini B.,Alcatel - Lucent | Bastug E.,CentraleSupelec | Kountouris M.,CentraleSupelec | And 3 more authors.
2015 IEEE International Conference on Communication Workshop, ICCW 2015 | Year: 2015

Endowed with context-awareness and proactive capabilities, caching users' content locally at the edge of the network is able to cope with increasing data traffic demand in 5G wireless networks. In this work, we focus on the energy consumption aspects of cache-enabled wireless cellular networks, specifically in terms of area power consumption (APC) and energy efficiency (EE). We assume that both base stations (BSs) and mobile users are distributed according to homogeneous Poisson point processes (PPPs) and we introduce a detailed power model that takes into account caching. We study the conditions under which the area power consumption is minimized with respect to BS transmit power, while ensuring a certain quality of service (QoS) in terms of coverage probability. Furthermore, we provide the optimal BS transmit power that maximizes the area spectral efficiency per unit total power spent. The main takeaway of this paper is that caching seems to be an energy efficient solution. © 2015 IEEE. Source

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