Grâce à l'évolution des outils d'automatisation et d'intelligence artificielle, les réseauxmobiles sont devenus de plus en plus dépendants de la machine. De nos jours, une grandepartie des tâches de gestion de réseaux est exécutée d'une façon autonome, sans interventionhumaine. Dans cette thèse, nous avons focalisé sur l'utilisation des techniques d'analyse dedonnées dans le but d'automatiser et de consolider le processus de résolution de défaillancesdans les réseaux. Pour ce faire, nous avons défini deux objectifs principaux : la détectiond'anomalies et le diagnostic des causes racines de ces anomalies. Le premier objectif consiste àdétecter automatiquement les anomalies dans les réseaux sans faire appel aux connaissancesdes experts. Pour atteindre cet objectif, nous avons proposé un algorithme, Watchmen AnomalyDetection (WAD), basé sur le concept de la reconnaissance de formes (pattern recognition). Cetalgorithme apprend le modèle du trafic réseau à partir de séries temporelles périodiques etdétecte des distorsions par rapport à ce modèle dans le flux de nouvelles données. Le secondobjectif a pour objet la détermination des causes racines des problèmes réseau sans aucuneconnaissance préalable sur l'architecture du réseau et des différents services. Pour ceci, nousavons conçu un algorithme, Automatic Root Cause Diagnosis (ARCD), qui permet de localiser lessources d'inefficacité dans le réseau. ARCD est composé de deux processus indépendants :l'identification des contributeurs majeurs à l'inefficacité globale du réseau et la détection desincompatibilités. WAD et ARCD ont fait preuve d'efficacité. Cependant, il est possible d'améliorerces algorithmes sur plusieurs aspects. / With the evolution of automation and artificial intelligence tools, mobile networks havebecome more and more machine reliant. Today, a large part of their management tasks runs inan autonomous way, without human intervention. In this thesis, we have focused on takingadvantage of the data analysis tools to automate the troubleshooting task and carry it to a deeperlevel. To do so, we have defined two main objectives: anomaly detection and root causediagnosis. The first objective is about detecting issues in the network automatically withoutincluding expert knowledge. To meet this objective, we have proposed an algorithm, WatchmenAnomaly Detection (WAD), based on pattern recognition. It learns patterns from periodic timeseries and detect distortions in the flow of new data. The second objective aims at identifying theroot cause of issues without any prior knowledge about the network topology and services. Toaddress this question, we have designed an algorithm, Automatic Root Cause Diagnosis (ARCD)that identifies the roots of network issues. ARCD is composed of two independent threads: MajorContributor identification and Incompatibility detection. WAD and ARCD have been proven to beeffective. However, many improvements of these algorithms are possible.

The cognitive radio (CR) concept is expected to be adopted along with many technologies to meet the requirements of the next generation of wireless and mobile systems, the 5G. Consequently, it is important to determine the performance of the CR systems with respect to these requirements. In this thesis, after briefly describing the 5G requirements, we present three main directions in which we aim to enhance the CR performance. The first direction is the reliability. We study the achievable rate of a multiple-input multiple-output (MIMO) relay-assisted CR under two scenarios; an unmanned aerial vehicle (UAV) one-way relaying (OWR) and a fixed two-way relaying (TWR). We propose special linear precoding schemes that enable the secondary user (SU) to take advantage of the primary-free channel eigenmodes. We study the SU rate sensitivity to the relay power, the relay gain, the UAV altitude, the number of antennas and the line of sight availability. The second direction is the scalability. We first study a multiple access channel (MAC) with multiple SUs scenario. We propose a particular linear precoding and SUs selection scheme maximizing their sum-rate. We show that the proposed scheme provides a significant sum-rate improvement as the number of SUs increases. Secondly, we expand our scalability study to cognitive cellular networks. We propose a low-complexity algorithm for base station activation/deactivation and dynamic spectrum management maximizing the profits of primary and secondary networks subject to green constraints. We show that our proposed algorithms achieve performance close to those obtained with the exhaustive search method. The third direction is the energy efficiency (EE). We present a novel power allocation scheme based on maximizing the EE of both single-input and single-output (SISO) and MIMO systems. We solve a non-convex problem and derive explicit expressions of the corresponding optimal power. When the instantaneous channel is not available, we present a simple sub-optimal power that achieves a near-optimal EE. The simulations show that the sub-optimal solution is very close to the optimal one. In the MIMO case, we show that adopting more antennas is more energy efficient.

Wireless communication systems have evolved substantially over the last two decades. The explosive growth of the wireless communications market is expected to continue in the future, as the demand for all types of wireless services is increasing. Beside providing higher data rates, next generation wireless networks (NGWN) are expected to have advanced capabilities such as interoperability, efficient spectrum utilization along with a wide variety of applications over different domains (e.g., public safety and military, aeronautical networks, femtocells, and so on) to the mobile users while serving as many users as possible. However, these advanced capabilities and services must be achieved under the constraint of limited available resources such as electromagnetic spectrum and power. In addition, NGWNs (and nodes within) need to modify themselves under rapidly changing conditions such as wireless propagation channel characteristics, traffic load, and so on. Moreover, NGWNs are expected to optimize their parameters by evaluating their experiences in the past. All of these characteristics imply that NGWNs should be equipped with cognitive capabilities including sensing, awareness, adaptation and responding to changing conditions along with learning about the past experiences. In this dissertation, environment, channel, and interference awareness are investigated in detail for NGWN. Methods for being aware of environment, channel, and interference are provided along with some possible ways of adapting several design parameters of NGWNs. In addition, cross-layer optimization issues are addressed from the perspective of both recently emerging technology called cognitive radio (CR) and NGWN.

Global mobile data traffic has more than doubled in the past four years, and will only increase throughout the upcoming years. Modern cellular systems are striving to enable communications at high data rates over wide geographical areas to meet the surge in data demand. This requires advanced technologies to mitigate fundamental effects of wireless communications like path-loss, shadowing, small-scale fading, and interference. Two of such technologies are: i) deploying multiple antennas at the transmitter and receiver, and ii) employing an extra radio, called the relay, to forward messages from the transmitter to the receiver. The advantages of both technologies can be leveraged by using multiple antennas at the relay, transmitter, and receiver. Multiple-antenna relay-assisted communication is emerging as one promising technique for expanding the overall capacity of cellular networks. Taking full advantage of multiple-antenna relay-assisted cellular systems requires transmission strategies for jointly configuring the transmitters and receivers based on knowledge of the wireless propagation medium. This dissertation proposes such transmission strategies for wireless multiple-antenna relay-assisted systems. Two popular types of relays are considered: i) amplify-and-forward relays (the relays simply apply linear signal processing to their observed signals before retransmitting) and ii) decode-and-forward relays (the relays decode their observed signals and then re-encode before retransmitting). The first part of this dissertation considers the three-node multiple-antenna amplify-and-forward relay channel. Algorithms for adaptively selecting the number of data streams and subsets of transmit antennas at the transmitter and relay to provide reliable transmission at a guaranteed rate are proposed. Expressions for extracting spatial characteristics of the end-to-end multiple-antenna relay channel are derived. The second part of the dissertation presents interference management strategies that are developed specifically for two models of multiple-antenna relay interference channels where a number of relays assist multiple transmitters to communicate with multiple receivers. One model uses amplify-and-forward relays while the other uses decode-and-forward relays. Based on the idea of interference alignment, these strategies aim at maximizing the sum of achievable end-to-end rates. Simulation results show that the proposed transmission strategies with multiple-antenna relays achieve higher capacity and reliability than both those without relays and those with single-antenna relays. / text

In recent years, mobile communications have become affordable and popular. High cellular capacity in terms of number of users and data-rates is in need. As the available frequency spectrums for mobile communications are limited, the utilization of the radio resources to achieve high capacity without imposing high equipment cost is of utmost importance. Recently, multi-hop cellular networks (MCNs) were introduced. These networks have the potential of enhancing the cell capacity and extending the cell coverage at low extra cost. However, in a cellular network, the cell or system capacity is inversely related to the cell size. In MCNs, the cell size, the network density and topology affect the coverage of source nodes and the total demands that can be served and, thus, the system throughput. Although the cell size is an important factor, it has not been exploited for maximizing throughput. Another major issue in MCNs is the increase in packet delay because multi-hopping is involved. High packet delay affects quality of service provisioning in these networks. In this thesis, we propose the Optimal Cell Size (OCS) and the Optimal Channel Assignment (OCA) schemes to address the cell size and packet delay issues for a time division duplex (TDD) wideband code division multiple access (W-CDMA) MCN. OCS finds the optimal cell sizes to provide an optimal balance of cell capacity and coverage to maximize the system throughput, whereas OCA assigns channels optimally in order to minimize packet relaying delay. Like many optimized schemes, OCS and OCA are computationally expensive and may not be suitable for large real-time problems. Hence, we also propose heuristics for solving the problems. For the cell size problem, we propose two heuristics: Smallest Cell Size First (SCSF) and Highest Throughput Cell Size First (HTCSF). For the channel assignment problem, we propose the Minimum Slot Waiting First (MSWF) heuristic. Simulation results show that OCS achieves high throughput compared to that of conventional (single-hop) cellular networks and OCA achieves low packet delay in MCNs. Results also show that the heuristics, SCSF, HTCSF and MSWF, provide good results compared to the optimal ones provided by OCS and OCA, respectively. / Thesis (Ph.D, Computing) -- Queen's University, 2009-02-02 22:53:41.825

The Internet has grown enormously since the introduction of the World Wide Web in the early 90's. The evolution and wide spread deployment of cellular networks have contributed to make the Internet accessible to more people in more places. The cellular networks of today offer data rates high enough for most Internet services. Even so, the service quality experienced by the users is often lower than in wired networks. The performance of TCP has a large impact on user experience. Therefore, we investigate TCP in cellular networks and propose functionality to improve the situation for TCP. We have studied sources of delay and data loss, such as link layer retransmissions, queuing, and handover. Measurements were conducted in a GSM/GPRS testbed. The results indicate that TCP interact efficiently with the GSM link layer protocol in most cases. From experiments of queuing in GPRS, we conclude that with a smaller buffer delay is reduced significantly, but that TCP throughput is about the same as with a larger buffer. Furthermore, we propose an improved buffer management when a connection loses all its resources to traffic with higher priority. We also propose a scheme for data forwarding to avoid negative impact on TCP during handover for WINNER, a research system that was used to test ideas for LTE. The achievable data rates in cellular networks are limited by inter-cell interference that vary over the cell. Inter-cell interference can be mitigated with Coordinated Multipoint techniques (CoMP), techniques that currently are being standardized for LTE-Advanced. System wide CoMP is, however, not an option, since it would be too resource consuming. In order to limit the required resources for CoMP, we propose an approach to select a subset of users for CoMP that is based on user experience. Simulation results indicate that user experience, represented with application utility,  and fairness are improved compared to if only rate is considered in the user selection. / The Internet has grown enormously since the introduction of the World Wide Web in the early 90's. The evolution and wide spread deployment of cellular networks have contributed to make the Internet accessible to more people in more places. The cellular networks of today offer data rates high enough for most Internet services. Even so, the service quality experienced by the users is often lower than in wired networks. The performance of TCP has a large impact on user experience. Therefore, we investigate TCP in cellular networks and propose functionality to improve the situation for TCP. We have studied sources of delay and data loss, such as link layer retransmissions, queuing, and handover. The achievable data rates in cellular networks are limited by inter-cell interference that vary over the cell area. Inter-cell interference can be mitigated with Coordinated Multipoint techniques (CoMP), techniques that currently are being standardized for LTE-Advanced. System wide CoMP is, however, not an option, since it would be too resource consuming. In order to limit the required resources for CoMP, we propose an approach to select a subset of the users for CoMP that is based on user experience.

Redes Definidas por Software ajudam a simplificar a programabilidade da rede ao desacoplar o plano de controle dos dispositivos de encaminhamento, e implementá-lo em um controlador logicamente centralizado. Apesar de permitir uma separação de conceitos mais clara, essa característica cria também uma relação de dependência entre controlador e dispositivos. Falhas no plano de controle prejudicam a visibilidade do estado da rede no controlador e podem tornar a rede inutilizável caso os dispositivos de encaminhamento sejam isolados. A relevância deste problema motivou uma série de propostas, incluindo a distribuição física de instâncias de controle e a delegação de tarefas aos dispositivos de encaminhamento. Esta dissertação contém a proposta e a avaliação de uma arquitetura que usa redes celulares de dados (4G) como enlaces reservas para o plano de controle. Nenhum trabalho anterior explorou esta ideia, apesar da pesquisa recente envolvendo Redes Definidas por Software e redes sem fio. A avaliação experimental permite uma melhor compreensão ao responder três perguntas: (i) Como o comportamento do tráfego do plano de controle é afetado pelas características de enlaces celulares, (ii) quão rapidamente o plano de controle é migrado para o enlace reserva quando uma falha ocorre e (iii) como funções de rede que dependem do estado da rede em um instante se comportam em tal arquitetura. Apesar da já esperada maior latência dos enlaces celulares, esta arquitetura mantém o funcionamento parcial de tarefas que dependem de visão global da rede quando falhas ocorrem nos enlaces primários, de maneira simples e com custo acessível. O grau de manutenção de tais tarefas é diretamente relacionado com sua dependência da rapidez de reação do plano de controle a eventos de rede. O principal benefício de prevenir a partição do plano de controle é a manutenção de uma visão global consistente da rede. / Software Defined Networks simplify network programmability by detaching the control plane from forwarding devices and deploying it into a logically centralized controller. While this allows a clearer separation of concerns, it also creates a dependency between them. Failures in the control plane break the controller view of the network state and could render the network unusable if forwarding devices cannot be reached. The relevance of this problem has led to a range of proposals, including physical distribution of controller instances and delegation of concerns to forwarding devices. This dissertation features the proposal and evaluation of an architecture that leverages cellular data networks (4G) as control plane backup links. No previous work has explored this idea, despite the recent research intersecting SDN and wireless networks. The experimental evaluation provides insights towards answering three research questions: (i) How is the behavior of control plane traffic affected by the characteristics of cellular links, (ii) how quickly is the control plane handed over to the backup link when a failure occurs and (iii) how well do network functions that rely on a snapshot of the network state behave on such an architecture. Despite the expected higher latency of cellular links, this architecture maintains partial functionality of tasks that depend on global network awareness when failures occur in primary control links in a simple, affordable fashion. The degree to which the functionality of these tasks is maintained is directly related to its dependency on the timeliness of control plane reaction to network events. The main benefit of preventing control plane partition is to maintain a consistent global view of the network.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2015. / Submitted by Fernanda Percia França (fernandafranca@bce.unb.br) on 2015-12-01T17:09:19Z No. of bitstreams: 1 2015_SamirKolawoléAkanniLandou.pdf: 2034280 bytes, checksum: e8c84ed0e5485fb56994f5d26d16cb7b (MD5) / Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2016-05-13T18:15:09Z (GMT) No. of bitstreams: 1 2015_SamirKolawoléAkanniLandou.pdf: 2034280 bytes, checksum: e8c84ed0e5485fb56994f5d26d16cb7b (MD5) / Made available in DSpace on 2016-05-13T18:15:09Z (GMT). No. of bitstreams: 1 2015_SamirKolawoléAkanniLandou.pdf: 2034280 bytes, checksum: e8c84ed0e5485fb56994f5d26d16cb7b (MD5) / Com o crescimento das redes celulares e com o surgimento de novas tecnologias, o consumo de energia e a eficiência energética das redes celulares se tornaram mais importantes. Recentemente, as comunicações verdes têm recebido muita atenção, a fim de reduzir o consumo de energia e minimizar as emissões de dióxido de carbono (CO2). Neste trabalho, estamos interessados em métodos de eficiência energética que otimizam a redução do consumo de energia das redes celulares, especialmente alterando a potência transmitida de estações de base. Investigamos algumas soluções encontradas na literatura, a saber, o sleep mode e o cell zooming. Nós investigamos também o uso do Coordinated Multi-Point (CoMP), uma tecnologia de rádio de transmissão coordenada, a fim de melhorar a qualidade da rede. _______________________________________________________________________________________________ ABSTRACT / With the growth of cellular networks and emergence of new technologies, the power consumption and energy efficiency of cellular networks have become more important. Recently, green communications have received much attention in order to reduce the energy consumption and minimize the carbon dioxide (CO2) emission. In this work, we are interested in power efficiency methods which optimize the energy saving of the cellular networks especially altering the transmitted power of base stations. We investigate some solutions found in the literature, namely sleep mode and cell zooming techniques. We also investigate the use of Coordinated Multi-Point (CoMP) transmission radio technology in order to improve the quality of the network. _______________________________________________________________________________________________ RÉSUMÉ / Avec la croissance des réseaux cellulaires et l'émergence de nouvelles technologies, la consommation d'énergie et l'efficacité énergétique des réseaux cellulaires sont devenues plus importantes. Récemment, les communications vertes ont reçu beaucoup d'attention dans le but de réduire la consommation d'énergie et de réduire les émissions de dioxyde de carbone (CO2). Dans ce travail, nous nous intéressons à des méthodes d'efficacité de puissance qui optimisent l’économie d'énergie des réseaux cellulaires en altérant particulièrement la puissance transmise des stations de base. Nous avons étudié des solutions trouvées dans la littérature, à savoir le sleep mode et le cell zooming. Nous avons étudié également l'utilisation de Coordinated Multi-Point (COMP), une technologie de radio de transmission coordonnée, afin d'améliorer la qualité du réseau.

Redes Definidas por Software ajudam a simplificar a programabilidade da rede ao desacoplar o plano de controle dos dispositivos de encaminhamento, e implementá-lo em um controlador logicamente centralizado. Apesar de permitir uma separação de conceitos mais clara, essa característica cria também uma relação de dependência entre controlador e dispositivos. Falhas no plano de controle prejudicam a visibilidade do estado da rede no controlador e podem tornar a rede inutilizável caso os dispositivos de encaminhamento sejam isolados. A relevância deste problema motivou uma série de propostas, incluindo a distribuição física de instâncias de controle e a delegação de tarefas aos dispositivos de encaminhamento. Esta dissertação contém a proposta e a avaliação de uma arquitetura que usa redes celulares de dados (4G) como enlaces reservas para o plano de controle. Nenhum trabalho anterior explorou esta ideia, apesar da pesquisa recente envolvendo Redes Definidas por Software e redes sem fio. A avaliação experimental permite uma melhor compreensão ao responder três perguntas: (i) Como o comportamento do tráfego do plano de controle é afetado pelas características de enlaces celulares, (ii) quão rapidamente o plano de controle é migrado para o enlace reserva quando uma falha ocorre e (iii) como funções de rede que dependem do estado da rede em um instante se comportam em tal arquitetura. Apesar da já esperada maior latência dos enlaces celulares, esta arquitetura mantém o funcionamento parcial de tarefas que dependem de visão global da rede quando falhas ocorrem nos enlaces primários, de maneira simples e com custo acessível. O grau de manutenção de tais tarefas é diretamente relacionado com sua dependência da rapidez de reação do plano de controle a eventos de rede. O principal benefício de prevenir a partição do plano de controle é a manutenção de uma visão global consistente da rede. / Software Defined Networks simplify network programmability by detaching the control plane from forwarding devices and deploying it into a logically centralized controller. While this allows a clearer separation of concerns, it also creates a dependency between them. Failures in the control plane break the controller view of the network state and could render the network unusable if forwarding devices cannot be reached. The relevance of this problem has led to a range of proposals, including physical distribution of controller instances and delegation of concerns to forwarding devices. This dissertation features the proposal and evaluation of an architecture that leverages cellular data networks (4G) as control plane backup links. No previous work has explored this idea, despite the recent research intersecting SDN and wireless networks. The experimental evaluation provides insights towards answering three research questions: (i) How is the behavior of control plane traffic affected by the characteristics of cellular links, (ii) how quickly is the control plane handed over to the backup link when a failure occurs and (iii) how well do network functions that rely on a snapshot of the network state behave on such an architecture. Despite the expected higher latency of cellular links, this architecture maintains partial functionality of tasks that depend on global network awareness when failures occur in primary control links in a simple, affordable fashion. The degree to which the functionality of these tasks is maintained is directly related to its dependency on the timeliness of control plane reaction to network events. The main benefit of preventing control plane partition is to maintain a consistent global view of the network.

Redes Definidas por Software ajudam a simplificar a programabilidade da rede ao desacoplar o plano de controle dos dispositivos de encaminhamento, e implementá-lo em um controlador logicamente centralizado. Apesar de permitir uma separação de conceitos mais clara, essa característica cria também uma relação de dependência entre controlador e dispositivos. Falhas no plano de controle prejudicam a visibilidade do estado da rede no controlador e podem tornar a rede inutilizável caso os dispositivos de encaminhamento sejam isolados. A relevância deste problema motivou uma série de propostas, incluindo a distribuição física de instâncias de controle e a delegação de tarefas aos dispositivos de encaminhamento. Esta dissertação contém a proposta e a avaliação de uma arquitetura que usa redes celulares de dados (4G) como enlaces reservas para o plano de controle. Nenhum trabalho anterior explorou esta ideia, apesar da pesquisa recente envolvendo Redes Definidas por Software e redes sem fio. A avaliação experimental permite uma melhor compreensão ao responder três perguntas: (i) Como o comportamento do tráfego do plano de controle é afetado pelas características de enlaces celulares, (ii) quão rapidamente o plano de controle é migrado para o enlace reserva quando uma falha ocorre e (iii) como funções de rede que dependem do estado da rede em um instante se comportam em tal arquitetura. Apesar da já esperada maior latência dos enlaces celulares, esta arquitetura mantém o funcionamento parcial de tarefas que dependem de visão global da rede quando falhas ocorrem nos enlaces primários, de maneira simples e com custo acessível. O grau de manutenção de tais tarefas é diretamente relacionado com sua dependência da rapidez de reação do plano de controle a eventos de rede. O principal benefício de prevenir a partição do plano de controle é a manutenção de uma visão global consistente da rede. / Software Defined Networks simplify network programmability by detaching the control plane from forwarding devices and deploying it into a logically centralized controller. While this allows a clearer separation of concerns, it also creates a dependency between them. Failures in the control plane break the controller view of the network state and could render the network unusable if forwarding devices cannot be reached. The relevance of this problem has led to a range of proposals, including physical distribution of controller instances and delegation of concerns to forwarding devices. This dissertation features the proposal and evaluation of an architecture that leverages cellular data networks (4G) as control plane backup links. No previous work has explored this idea, despite the recent research intersecting SDN and wireless networks. The experimental evaluation provides insights towards answering three research questions: (i) How is the behavior of control plane traffic affected by the characteristics of cellular links, (ii) how quickly is the control plane handed over to the backup link when a failure occurs and (iii) how well do network functions that rely on a snapshot of the network state behave on such an architecture. Despite the expected higher latency of cellular links, this architecture maintains partial functionality of tasks that depend on global network awareness when failures occur in primary control links in a simple, affordable fashion. The degree to which the functionality of these tasks is maintained is directly related to its dependency on the timeliness of control plane reaction to network events. The main benefit of preventing control plane partition is to maintain a consistent global view of the network.