A formação de redes colaborativas é uma importante forma das organizações estimularem a inovação, reduzirem custos e transferir conhecimentos. Uma forma particular de rede colaborativa, as redes auto-organizadas, demonstram grande capacidade de promover o aprendizado dos envolvidos, sistematizar o conhecimento e promover a inovação. Já os programas Seis Sigma, adotados por diversas organizações, possuem como objetivo principal a redução da variabilidade de um processo, resultando na redução de custos e melhoria da qualidade. A literatura sobre redes auto-organizadas pouco apresenta sobre a formação destas redes e a literatura sobre Seis Sigma é voltada a métodos estatísticos. Desta forma, o objetivo desta pesquisa é identificar os elementos para um modelo de referência baseado no programa Seis Sigma para a formação e gerência de redes de inovação auto-organizadas. Foram realizados cinco estudos de caso em diferentes organizações. Os programas Seis Sigma destas organizações foram modelos com o uso da metodologia Enterprise Knowledge Development (EKD). Com base na literatura estudada foram identificas as necessidades de mudanças que viabilizariam a formação de redes de inovação auto-organizadas. Como resultado tem-se os elementos para o modelo de referência para formação e gerência de redes de inovação auto-organizadas baseado no programa Seis Sigma. / The formation of collaborative networks is an important way for organizations to stimulate innovation, reduce costs and transfer knowledge. A particular form of collaborative network, the self-organized networks have shown great capability to promote the learning of those involved, systematize knowledge and lead to innovation. The Six Sigma programs, adopted by several organizations, have as main objective the process variability reduction, resulting in lower costs and quality improvement. The literature on self-organized networks presents little about the formation of these kind of networks and literature on Six Sigma is focused on statistical methods. Thus, the objective of this research is to identify the elements for a reference model based on the Six Sigma program for setting up and management of innovation selforganized networks. Five case studies were conducted in different organizations. The Six Sigma programs of these organizations were modeled using the Enterprise Knowledge Development (EKD) methodology. Based on the studied literature the needs for changes that enables the formation of innovation self-organized networks were identified. As a result there are the elements of the reference model for the formation and management of innovation self-organized networks based on the Six Sigma program.

A formação de redes colaborativas é uma importante forma das organizações estimularem a inovação, reduzirem custos e transferir conhecimentos. Uma forma particular de rede colaborativa, as redes auto-organizadas, demonstram grande capacidade de promover o aprendizado dos envolvidos, sistematizar o conhecimento e promover a inovação. Já os programas Seis Sigma, adotados por diversas organizações, possuem como objetivo principal a redução da variabilidade de um processo, resultando na redução de custos e melhoria da qualidade. A literatura sobre redes auto-organizadas pouco apresenta sobre a formação destas redes e a literatura sobre Seis Sigma é voltada a métodos estatísticos. Desta forma, o objetivo desta pesquisa é identificar os elementos para um modelo de referência baseado no programa Seis Sigma para a formação e gerência de redes de inovação auto-organizadas. Foram realizados cinco estudos de caso em diferentes organizações. Os programas Seis Sigma destas organizações foram modelos com o uso da metodologia Enterprise Knowledge Development (EKD). Com base na literatura estudada foram identificas as necessidades de mudanças que viabilizariam a formação de redes de inovação auto-organizadas. Como resultado tem-se os elementos para o modelo de referência para formação e gerência de redes de inovação auto-organizadas baseado no programa Seis Sigma. / The formation of collaborative networks is an important way for organizations to stimulate innovation, reduce costs and transfer knowledge. A particular form of collaborative network, the self-organized networks have shown great capability to promote the learning of those involved, systematize knowledge and lead to innovation. The Six Sigma programs, adopted by several organizations, have as main objective the process variability reduction, resulting in lower costs and quality improvement. The literature on self-organized networks presents little about the formation of these kind of networks and literature on Six Sigma is focused on statistical methods. Thus, the objective of this research is to identify the elements for a reference model based on the Six Sigma program for setting up and management of innovation selforganized networks. Five case studies were conducted in different organizations. The Six Sigma programs of these organizations were modeled using the Enterprise Knowledge Development (EKD) methodology. Based on the studied literature the needs for changes that enables the formation of innovation self-organized networks were identified. As a result there are the elements of the reference model for the formation and management of innovation self-organized networks based on the Six Sigma program.

L’optimisation de l’opération des réseaux mobiles a toujours été d'un très grand intérêt pour les opérateurs, surtout avec une augmentation rapide du trafic mobile, des attentes qualité de service encore plus élevées des utilisateurs, et l’émergence de nouveaux services requérant des contraintes spécifiques et différentes. Le concept de gestion autonome des réseaux (SON) a été introduit par la 3rd Generation Partnership Project comme étant une solution prometteuse pour simplifier l’opération et la gestion des réseaux complexes. Aujourd’hui, plusieurs fonctions SON sont déjà déployées dans les réseaux. Cependant, les actions conduites par les fonctions SON dans le réseau dépendent de la configuration de l’algorithme même de ces fonctions, et aussi du contexte du réseau et de l’environnement ou cette fonction est déployée. D’autre part, un réseau radio mobile auto-organisant serait idéalement un réseau où toutes les fonctions autonomes (SON) fonctionnent de manière coordonnée et cohérente pour répondre à des objectifs de haut niveau de l’opérateur. L’entité autonome serait donc le réseau capable de s’autogérer pour répondre à une stratégie globale de l’opérateur, exprimée en termes d’objectifs de haut niveau de l’opérateur. A cette fin, nous proposons dans cette thèse une approche qu'on appel « Cognitive Policy Based SON Management » (C-PBSM). Le C-PBSM est capable d’apprendre des configurations optimales des fonctions SON selon les exigences de l’opérateur. Il a également la capacité d’améliorer sa décision au cours du temps en apprenant de son expérience passée, et de s’adapter avec les changements de l’environnement. Nous étudions plusieurs approches pour mettre en place la boucle cognitive en se basant sur l’apprentissage par renforcement (RL). Nous analysons la convergence et la scalabilité de ces approches et proposons des solutions adaptées. Nous prenons en compte la non stationnarité des réseaux, notamment la variation de trafic. Nous proposons également des solutions pour mettre en œuvre un apprentissage collaboratif et un transfert des connaissances. Une architecture SDN (software defined networks) est proposée pour le déploiement des agents d’apprentissage dans le réseau. / The pressure on operators to improve the network management efficiency is constantly growing for many reasons: the user traffic that is increasing very fast, higher end users expectations, emerging services with very specific requirements. Self-Organizing Networks (SON) concept was introduced by the 3rd Generation Partnership Project as a promising solution to simplify the operation and management of complex networks. Many SON modules are already being deployed in today’s networks. Such networks are known as SON enabled networks, and they have proved to be useful in reducing the complexity of network management. However, SON enabled networks are still far from realizing a network that is autonomous and self-managed as a whole. In fact, the behavior of the SON functions depends on the parameters of their algorithm, as well as on the network environment where it is deployed. Besides, SON objectives and actions might be conflicting with each other, leading to incompatible parameter tuning in the network. Each SON function hence still needs to be itself manually configured, depending on the network environment and the objectives of the operator. In this thesis, we propose an approach for an integrated SON management system through a Cognitive Policy Based SON Management (C-PBSM) approach, based on Reinforcement Learning (RL). The C-PBSM translates autonomously high level operator objectives, formulated as target Key Performance Indicators (KPIs), into configurations of the SON functions. Furthermore, through its cognitive capabilities, the C-PBSM is able to build its knowledge by interacting with the real network. It is also capable of adapting with the environment changes. We investigate different RL approaches, we analyze the convergence time and the scalability and propose adapted solutions. We tackle the problem of non-stationarity in the network, notably the traffic variations, as well as the different contexts present in a network. We propose as well an approach for transfer learning and collaborative learning. Practical aspects of deploying RL agents in real networks are also investigated under Software Defined Network (SDN) architecture.

Η παρούσα διατριβή κινείται στο χώρο των Ασύρματα Δικτυωμένων Συστημάτων και έχει ως αντικείμενο τη μελέτη και τη σύνθεση μηχανισμών που βελτιώνουν τη λειτουργία τους. Ο όρος Ασύρματα Δικτυωμένα Συστήματα αναφέρεται στα συστήματα των οποίων τα δομικά στοιχεία συνδέονται μέσω ασύρματων δικτύων, με την έμφαση να δίνεται στα αυτό-οργανωμένα δίκτυα και στα δίκτυα αισθητήρων. Η βελτιστοποίηση και ο έλεγχος ενός Ασύρματα Δικτυωμένου Συστήματος γίνεται με γνώμονα την Ποιότητα των παρεχόμενων Υπηρεσιών του δικτύου, η οποία χρησιμοποιείται ως μέτρο αξιολόγησης και επαναπροσδιορισμού των παραμέτρων λειτουργίας αυτού. Προσεγγίζοντας το θέμα από την οπτική γωνία του δικτύου, οι μηχανισμοί που είναι υπεύθυνοι για τη βελτιστοποίηση της λειτουργίας των Ασύρματα Δικτυωμένων Συστημάτων, αποστασιοποιούνται από την ανάπτυξη νέων πρωτοκόλλων για τα διάφορα επίπεδα του μοντέλου αναφοράς Ανοιχτής Διασύνδεσης Συστημάτων. Για τον λόγο αυτό, αναφορικά με το μοντέλο αναφοράς Ανοιχτής Διασύνδεσης Συστημάτων, το ζήτημα της βελτιστοποίησης της λειτουργίας των Ασύρματα Δικτυωμένων Συστημάτων προσεγγίζεται από τα ακραία επίπεδα της στοίβας πρωτοκόλλων, και συγκεκριμένα από την οπτική γωνία του Επιπέδου Εφαρμογής και του Φυσικού Επιπέδου. Στο Επίπεδο Εφαρμογής το ενδιαφέρον επικεντρώνεται στην διασφάλιση των περιθωρίων ευστάθειας για τα Ασύρματα Δικτυωμένα Συστήματα Ελέγχου. Η διασφάλιση της ομαλής λειτουργίας του συστήματος κλειστού βρόχου βασίζεται σε διακοπτικές δομές ελέγχου, των οποίων οι παράμετροι λειτουργίας καθορίζονται από την Ποιότητα Υπηρεσίας του δικτύου, και συγκεκριμένα από το ποσοστό των επιτυχώς ληφθέντων πακέτων. Στο Φυσικό Επίπεδο εξετάζεται αρχικά το πρόβλημα αποκατάστασης της συνδεσιμότητας μεταξύ των μελών ενός Ασύρματα Δικτυωμένου Συστήματος και στην συνέχεια το πρόβλημα επαναπροσδιορισμού της ποιότητας των ασύρματων ζεύξεων. Οι κεντρικοποιημένοι και κατανεμημένοι μηχανισμοί που αναπτύσσονται για τη βελτιστοποίηση των παραμέτρων της Ποιότητας Υπηρεσίας των Ασύρματα Δικτυωμένων Συστημάτων στο Φυσικό Επίπεδο βασίζονται σε εργαλεία της Υπολογιστικής Γεωμετρίας, συνδυάζοντας τα χωρικά χαρακτηριστικά ενός Ασύρματα Δικτυωμένου Συστήματος με δημοφιλή μοντέλα διάδοσης μεγάλης κλίμακας. Τέλος, η αξιολόγηση των μεθόδων ελέγχου και βελτιστοποίησης της λειτουργίας των Ασύρματα Δικτυωμένων Συστημάτων πραγματοποιείται με την εφαρμογή τους σε κατάλληλες πειραματικές διατάξεις και σε ένα καθορισμένο σύνολο σεναρίων εξομοίωσης. / The primary objective of the present PhD thesis is the analysis and the synthesis of mechanisms and algorithms that optimize the operation of Wireless Networked Systems. The term Wireless Networked Systems is used to describe the distributed systems, whose components are interconnected over wireless networks. Referring to wireless networking, the emphasis is given at the self-organized Ad-hoc and Sensor Networks. The effort made is focused on the reconfiguration of the Quality of Service of the underlying network. From such a perspective, the mechanisms responsible for improving the Quality of Service differentiate from the design of novel, specialized communication protocols. More specifically, with respect to the Open Systems Interconnection Reference Model (OSI-RM), the optimization issues of the Wireless Networked Systems’ operation are examined at the Application and Physical Layer. At the Application Layer, problems related to the guarantee of the stability margins for Wireless Networked Controlled Systems are studied. More precisely, the assurance of the desired performance for the closed-loop controlled system is based on switching control techniques. The optimization decision variables are determined by the network’s Quality of Service parameters. At the Physical Layer the objective is twofold: (a) to establish the physical connectivity among the members of the Wireless Networked System and (b) to optimize of the wireless link’s quality. Based on the combination of the spatial characteristics of the Wireless Networked Systems with large-scale radio propagation models, the centralized and distributed mechanisms, synthesized for the optimization of the network’s Quality of Service at the Physical Layer, exploit effectively concepts adopted by the Computational Geometry. Finally, properly developed experimental testbeds and network simulation scenaria are utilized to examine the efficiency of the synthesized mechanisms for the control and optimization of the operation of Wireless Networked Systems at the Application and Physical Layer.

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La préservation de l’environnement et des ressources naturelles pour les prochaines générations est aujourd’hui considérée comme un des axes les plus prioritaires dans presque tous les secteurs économiques. Le secteur des Technologies de l’Information et de la Communication est loin d’être épargné de cette tendance écologique. Nous considérons dans cette thèse la problématique de la conservation d’énergie dans le contexte technologique actuel caractérisé par: • La coexistence d’une multitude de technologies d’accès sans fil offrant un environnement riche et dynamique • Des terminaux mobiles multimodaux • Limitations persistantes des sources d’énergie sur les terminaux mobiles. Dans ce contexte très riche, les possibilités offertes aux usagers sont à double tranchant. D’un côté, elles peuvent très bien améliorer la QoS en offrant toujours la meilleure connectivité en fonction du contexte de l’utilisateur. D’un autre côté, et sans une bonne optimisation de la consommation d’énergie sur le terminal, la disponibilité de celui-ci peut vite diminuer et donc faire baisser la QoE à cause de l’énergie nécessaire pour gérer plusieurs interfaces radio en parallèle. Nous considérons essentiellement les liens entre les stations de base (ou les point d’accès) et les terminaux mobiles. Notre objectif étant d’analyser la consommation d’énergie sur ces liens pour ensuite proposer des contributions permettant de mieux la maitriser. Nous focalisons essentiellement sur l’exploitation des multiples interfaces et du multi-flux pour étudier, analyser et proposer des solutions dynamiques et adaptatives d’ordonnancement, de sélection et de gestion d’interfaces minimisant la consommation d’énergie / Since the last decades, environmental issues are becoming among the major concerns for most human activities, including the Information and Communication Technologies sector. This will surely influence upcoming networking technologies, architectures and usage practices. New approaches and methodologies are required in order to evaluate and to reduce the Carbon Footprint toward what is commonly denoted as Green Networks. Within the ICT sector, the main efforts are related to energy saving techniques. These efforts started in early stages within wireless technologies, mainly because of energy limitations on mobile devices such as mobile phones and wireless sensors. Additionally, because of health considerations, standardization bodies and government had set stringent policies and limits on electromagnetic radiation levels that can be emitted by radio stations. For these reasons, many academic and industrial research and development activities had led to a number of relatively energy efficient solutions. In this thesis, we consider energy efficiency in the context of Heterogeneous Wireless Access Networks. These are composed of multi-standards wireless network solutions, with non uniform topologies and cell sizes and Multi-Modal mobile terminals able to manage simultaneously different connections. The main contributions of our studies include the proposal of new optimization solutions regarding user association and scheduling techniques at both flow and packet levels for multi-homed mobile terminals. An overall context-based solution is also proposed in order to provide end-to-end energy efficient networking solutions