When Cellular Meets WiFi in Wireless Small Cell Networks

The deployment of small cell base stations(SCBSs) overlaid on existing macro-cellular systems is seen as a key solution for offloading traffic, optimizing coverage, and boosting the capacity of future cellular wireless systems. The next-generation of SCBSs is envisioned to be multi-mode, i.e., capable of transmitting simultaneously on both licensed and unlicensed bands. This constitutes a cost-effective integration of both WiFi and cellular radio access technologies (RATs) that can efficiently cope with peak wireless data traffic and heterogeneous quality-of-service requirements. To leverage the advantage of such multi-mode SCBSs, we discuss the novel proposed paradigm of cross-system learning by means of which SCBSs self-organize and autonomously steer their traffic flows across different RATs. Cross-system learning allows the SCBSs to leverage the advantage of both the WiFi and cellular worlds. For example, the SCBSs can offload delay-tolerant data traffic to WiFi, while simultaneously learning the probability distribution function of their transmission strategy over the licensed cellular band. This article will first introduce the basic building blocks of cross-system learning and then provide preliminary performance evaluation in a Long-Term Evolution (LTE) simulator overlaid with WiFi hotspots. Remarkably, it is shown that the proposed cross-system learning approach significantly outperforms a number of benchmark traffic steering policies

In-Building Capacity Enhancement using Small Cells in Mobile Networks: An Overview

In this paper, we give an overview of the state-of-the-art research studies to present the potential of small cells to address the high capacity demands of in-building users in mobile networks. In doing so, we discuss relevant theoretical backgrounds and carry out performance evaluations of key enabling technologies along with three major directions toward improving the network capacity, including spectrum accessibility, Spectral Efficiency (SE) improvement, and network densification. For the spectrum accessibility, numerous types of Small Cell Base Station (SBS) architectures of a Mobile Network Operator (MNO) are evaluated. For the SE improvement, cognitive radio techniques are evaluated for the Dynamic Spectrum Sharing (DSS) among multiple MNOs in a country. For the network densification, the spectrum reuse is evaluated at both intra-and inter-building levels for a given Co-Channel Interference (CCI) constraint. It is shown that multi-band multi-transceiver enabled small cells operating in the high-frequency millimeter-wave licensed or unlicensed spectrum to realize DSS techniques by exploiting SBS architectures for the spectrum accessibility, a hybrid interweave-underlay spectrum access in Cognitive Radio Networks for the spectral efficiency improvement, and both vertical and horizontal spectrum reuse in small cells deployed densely within buildings for the network densification can address high capacity demand in indoor mobile networks

The co-existence of Femtocell with WiFi (in case of unlicensed spectrum splitting & sharing)

Les femtocellules et le WiFi sont souvent présentés comme étant deux technologies concurrentes. Cependant, la réalité dit totalement l'inverse; ces technologies sont supposées jouer des rôles complémentaires dans le but d'accompagner la croissance fulgurante du trafic mobile. De plus, elles sont souvent implémentées dans un même et unique équipement d'accès. Les équipements mobiles pourront ainsi choisir l'utilisation de la technologie qui représente la meilleure option. Le déploiement des femtocellules dans les hotspots WiFi permettra aux opérateurs de donner aux usagers la possibilité d'utiliser les technologies 3G. Par conséquent, grâce à ces deux technologies, la qualité de l'expérience de la communication pendant la mobilité sera sans doute meilleure. Toutefois, cette coexistence présente de nouveaux défis en vue de l'amélioration de performances en termes des débits de transmission et de qualité de service des usagers. Ainsi, nous croyons qu'un partitionnement efficace des ressources spectrales accompagné d'un réglage minutieux des paramètres de transmission permettra de maximiser les performances des deux technologies. Dans ce mémoire, nous nous intéressons à la coexistence des technologies femtocellule et WiFi : (i) Dans un premier lieu, nous proposons une technique de partage des bandes spectrales ouvertes entre le réseau WiFi et le réseau femtocellule. La technique proposée assure une qualité de service et une équité entre les transmissions concurrentes. En se basant sur plusieurs simulations, nous démontrons que la technique proposée assure un partage équitable du spectre. (ii) Dans un second lieu, nous proposons un Framework ayant pour objectif l'amélioration du débit total du réseau des femtocellules lorsque ces dernières utilisent simultanément des bandes de spectres ouvertes et d'autres sous licences. Le système étudié, comprenant le réseau WiFi et le réseau des femtocellules, a été modélisé analytiquement et ses performances ont été évaluées par plusieurs simulations. Ces dernières ont permis de quantifier l'effet de plusieurs paramètres de la technologie WiFi sur les performances du système étudié.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : Femtocellule, WiFi, allocation de spectre, qualité de service, équité, capacité, spectre sans licence, modèle de back-off

Energy and throughput efficient strategies for heterogeneous future communication networks

As a result of the proliferation of wireless-enabled user equipment and data-hungry applications, mobile data traffic has exponentially increased in recent years.This in-crease has not only forced mobile networks to compete on the scarce wireless spectrum but also to intensify their power consumption to serve an ever-increasing number of user devices. The Heterogeneous Network (HetNet) concept, where mixed types of low-power base stations coexist with large macro base stations, has emerged as a potential solution to address power consumption and spectrum scarcity challenges. However, as a consequence of their inflexible, constrained, and hardware-based configurations, HetNets have major limitations in adapting to fluctuating traffic patterns. Moreover, for large mobile networks, the number of low-power base stations (BSs) may increase dramatically leading to sever power consumption. This can easily overwhelm the benefits of the HetNet concept. This thesis exploits the adaptive nature of Software-defined Radio (SDR) technology to design novel and optimal communication strategies. These strategies have been designed to leverage the spectrum-based cell zooming technique, the long-term evolution licensed assisted access (LTE-LAA) concept, and green energy, in order to introduce a novel communication framework that endeavors to minimize overall network on-grid power consumption and to maximize aggregated throughput, which brings significant benefits for both network operators and their customers. The proposed strategies take into consideration user data demands, BS loads, BS power consumption, and available spectrum to model the research questions as optimization problems. In addition, this thesis leverages the opportunistic nature of the cognitive radio (CR) technique and the adaptive nature of the SDR to introduce a CR-based communication strategy. This proposed CR-based strategy alleviates the power consumption of the CR technique and enhances its security measures according to the confidentiality level of the data being sent. Furthermore, the introduced strategy takes into account user-related factors, such as user battery levels and user data types, and network-related factors, such as the number of unutilized bands and vulnerability level, and then models the research question as a constrained optimization problem. Considering the time complexity of the optimum solutions for the above-mentioned strategies, heuristic solutions were proposed and examined against existing solutions. The obtained results show that the proposed strategies can save energy consumption up to 18%, increase user throughput up to 23%, and achieve better spectrum utilization. Therefore, the proposed strategies offer substantial benefits for both network operators and users