The 3GPP Long Term Evolution (LTE) is considered as a dominant future cellular wireless technology in terms of performance and user experience. With technological advancement of the wireless networks, dependencies and business impact of the mobile network services have increased phenomenally. It is, therefore, crucial to address the issues regarding network infrastructure or service failure. In this thesis, a self-healing solution is presented for the LTE Evolved Packet Core (EPC) with a view to maintaining service continuity in the event of core network elements - the MME and S-GW failures. The core network element failures have significant impact on a larger number of subscribers in comparison to the access network element failures. In the proposed self-healing scheme, the restoration mechanisms and associate failover recovery procedures with regards to service survivability are described in details from the LTE network and protocol perspective. This thesis studies two different self-healing approaches - the centralized active-backup and distributed active-active and conducts simulation for each approach in various failure scenarios. The performances of each of these scenarios are evaluated in terms of service restoration time, throughput, EPS (Evolved Packet System) bearer delay etc. The results show that the proposed self-healing system can ensure service continuity at a certain level if resources are properly provisioned. And in terms of restoration delay, in general, the active-backup configuration performs better than the active-active configuration. The thesis presents analytical and simulation methods to estimate signaling message overhead at the LTE EPC that arises due to the recovery process. It also analyzes the bandwidth requirements of the signaling traffic that is incurred by the other operational procedures of the self-healing scheme and their ramification to the LTE core network. / UOIT

La continuité de service est un élément important dans les communications mobiles. Avec la coexistence de différentes technologies d'accès au réseau et l'émergence de dispositifs mobiles avec plusieurs interfaces réseau, les fournisseurs de services doivent maintenir la communication en cours lorsque les mobiles voyagent entre des réseaux hétérogènes. Des services comme l'IPTV, vidéo à la demande ou la voix sur IP sont largement proposés par les opérateurs pour lesquels la continuité de service doit être garantie. Cette thèse est consacrée à la continuité du service pour des applications temps réel dans des réseaux hétérogènes. Nous abordons ce problème de deux perspectives: la mobilité de session et la mobilité de terminal. Bien que ces deux mécanismes aient le même but qui est d'assurer la continuité de service lors du changement de terminal ou de réseau d'accès, chaque technique a ses propres défis et contraintes. En ce qui concerne la mobilité de session, un nouveau protocole de signalisation a été proposé pour transférer la session entre les différents terminaux d’un utilisateur. Ce protocole a été conçu pour les scénarios de streaming vidéo. Son implémentation a permis la validation du protocole proposé ainsi que son évaluation. En outre, nous traitons le problème de l'adaptation des flux multimédias, notamment la renégociation des paramètres de la qualité de service puisque la session pourrait être transféré à un nouveau terminal avec des capacités différentes que le terminal d’origine. Cette renégociation peut être étendue pour couvrir le cas où certains paramètres internes sont dégradés au cours de la session dans le même terminal. Quand à la mobilité de terminal, nous proposons un mécanisme basé sur l’utilisation de la nouvelle norme IEEE802.21 et du protocole de mobilité FMIPv6. Le but de cette proposition est de réduire le délai du handover et la taille de l’espace mémoire dédiée au niveau des routeurs d'accès. En outre, une optimisation est proposée pour FMIPv6 afin de maximiser la probabilité de son mode prédictive. Dans le même contexte, la mobilité dans l’IP Multimédia Subsystem (IMS) est considéré et une solution adaptée est proposée pour répondre aux exigences de l’IMS. Enfin, nous menons une étude comparative entre les différentes variantes de Mobile IP dans le cas de handover vertical. En se basant sur cette comparaison, nous donnons quelques directives qui devraient aider à choisir le protocole le plus efficace suivant des paramètres spécifiques. Les solutions proposées et les études ont été évaluées avec des méthodes analytiques et/ou en faisant appel à des simulations. / Service continuity is an important component in mobile communications. With the coexistence of different access network technologies and the emergence of multi-interface mobile devices, service providers should maintain the ongoing communication when the mobile travels among heterogeneous networks. Services like IPTV, video on demand or voice over IP are widely proposed by operators for which service continuity should be guaranteed. This thesis is devoted to service continuity of real-time applications in heterogeneous networks. We tackle this problem from two perspectives: session mobility and terminal mobility. Although these two mechanisms have the same purpose which is ensuring service continuity when changing the terminal or the access network, each technique has its own challenges and constraints. As far as session mobility is concerned, a new signaling protocol has been proposed to transfer the session between different terminals. This protocol has been implemented in video streaming scenarios and evaluated in a testbed. Moreover, we address the problem of media adaptation, especially renegotiation of QoS parameters since session might be transferred to a new terminal with different capabilities than the original one. QoS renegotiation can be extended to cover the case where some internal parameters are degraded during the session in the same terminal. For terminal mobility, we propose a new handover mechanism using IEEE802.21 with Fast handover for Mobile IPv6. The purpose of this proposal is to reduce the handover delay and the dedicated buffer in access routers. In addition, an optimization is proposed for Fast handovers for Mobile IPv6 in order to maximize the probability of its predictive mode. In the same context, mobility in IMS is considered and an appropriate solution is proposed to answer IMS requirements. Finally, we conduct a comparison study between different mobile IP variants in the case of vertical handover. Based on this comparison, we give some guidelines that should help in choosing the most efficient protocol following specific parameters. The proposed solutions and studies have been evaluated analytically or/and using a simulation tool.

Edge Computation aims to bring the functionality of hyperscale datacenters closer to the end-user as to offer reliable low-latency communication through distributed compute power. With the ongoing rise of 5G standalone promis-ing low latency and high capacity, the possibility of running user real-time applications in a distributed setting has never been closer. The focus of this master’s thesis is to analyze and evaluate the limitation and solution alternatives for application state migration, whilst maintaining service continuity. By employing migration strategies and custom application specific methods, this thesis proposes avenues of minimizing application state divergence and viable, distributed Edge Compute specific, modifications of an orchestration system applicable without breaking core functionality.

京都大学 / 新制・課程博士 / 博士(情報学) / 甲第25511号 / 情博第884号 / 新制||情||148(附属図書館) / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 大木 英司, 教授 原田 博司, 教授 山下 信雄 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

The wide-spread presence of wireless networks and the availability of mobile devices has enabled the development of mobile applications that take us a step closer to accomplishing Weiser’s vision of ubiquitous computing (Weiser, 1991). Unfortunately however, network connectivity is still not given anywhere and at any time. To increase the benefit of mobile applications, the next logical step is to provide support for an offline modethat allows to continuously work with an application, even when the device is not connected to a network. In this paper typical problems of replicating data are explained, possible solutions are discussed and two architectural patterns that could be used to implement hybrid support are illustrated.

This thesis is concerned about Business Continuity Management with the focus on determination of the RTO and RPO parameters. The work is divided into two main parts. The first section briefly describes theoretical issues of Business Continuity Management in conjunction with IT Service Continuity Management. Then there are described various technologies that are currently used to ensure continuity and recovery of IT systems. In conclusion of the theoretical part, the work focuses on the process of Business Impact Analysis. This thesis thus offers a comprehensive view of main principles and benefits that these concepts have for company and how they should be integrated with each other. It provides an overview of various technologies, their link to RTO and RPO parameters and also the definition of steps of disaster recovery procedure. The work also briefly defines the basic procedure for determination of the RTO and RPO parameters, subsequent steps needed to design recovery solutions and analyzes various aspects which need to be considered when defining the parameters of continuity. The second practical part is based on the previous theoretically defined procedure and its aim is to analyze the data acquired during the questionnaire investigation in chosen company to determine the parameters of continuity for the applications in use and then suggest appropriate ways of addressing their backup and recovery. The result of this thesis is therefore a description of the analysis and practical application of methods for setting the parameters for continuity of information systems and the subsequent establishment of necessary measures.

This research has public technological higher education institutes as a case study, which proposes an IT risk management model to guarantee the continuity of the service in its main processes, where 3 public institutes were analyzed to determine the current state of the processes of those institutes, obtaining as results that the IT areas have not identified the risks to which the institutions are exposed and they do not have a strategic IT plan, which generates that within the institutes there is no improvement in their organizational processes. The model is based on the harmonization of standards or frameworks that refer to risk management, which were analyzed in a general way to determine the impact on IT risk management to guarantee the service continuity in the organizational processes, of which only 3 were selected from a list of 6. The model was validated through expert judgment, which was based on the indicators of sufficiency, clarity, coherence and relevance to give the validity and acceptance of the proposed model. Finally, the model was applied in an institute which allowed it to improve IT risk management and guarantee the continuity of the service of its organizational processes, through compliance with the CBC licensing requirements. / Esta investigación tiene como caso de estudio a los institutos de educación superior tecnológicos públicos, la cual propone un modelo de gestión de riesgos de TI para garantizar la continuidad del servicio en sus principales procesos, en donde se analizó a 3 institutos públicos para poder determinar el estado actual de los procesos de dichos institutos, obteniendo como resultados que las áreas de TI no tienen identificado los riesgos a los que están expuestas las instituciones y no cuentan con un plan estratégico de TI, lo que genera que dentro de los institutos no exista una mejora en sus procesos organizacionales. El modelo se basa en la armonización de estándares o marcos de trabajo que tienen referencia a la gestión de riesgos, los cuales se analizaron de forma general para determinar la afectación en la gestión de riesgos de TI para garantizar la continuidad del servicio en los procesos organizacionales, de los cuales se seleccionaron solo 3 de una lista de 6. El modelo fue validado por juicio de expertos, los cuales se basaron en los indicadores de suficiencia, claridad, coherencia y relevancia para dar la valides y aceptación del modelo propuesto. Finalmente, el modelo fue aplicado en un instituto el cual permitió mejorar la gestión de riesgos de TI y garantizar la continuidad del servicio de sus procesos organizacionales, a través del cumplimiento de los requisitos de la CBC de licenciamientos.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O uso de dispositivos multi-interface, tais como smart phones, tem crescido ao mesmo tempo que as demandas por melhores serviÃos de mobilidade em redes heterogÃneas. Neste cenÃrio, a ideia da continuidade de serviÃos tornou-se um requisito crucial. Para atender essas demandas, esquemas eficientes de handover devem ser desenvolvidos com o objetivo de alcanÃar o chamado Handover Transparente, que significa a mudanÃa de domÃnios de rede de uma forma transparente e sem a descontinuidade dos serviÃos para o usuÃrio final. Atualmente, existem diferentes esquemas de handover e alguns deles podem envolver diferentes tecnologias de acesso (Handover Vertical). Entretanto, o tempo de interrupÃÃo do serviÃo ainda à um problema a ser resolvido. A principal proposta deste trabalho à uma melhoria para Handovers Verticais utilizando mobilidade IP, objetivando o tÃo desejado Handover Transparente. Neste trabalho, fez-se uso do framework MIH (Media Independent Handover) fornecido pelo padrÃo IEEE 802.21 para habilitar o handover vertical em redes heterogÃneas. AlÃm disso, propÃe-se uma extensÃo do protocolo FMIPv6 (Fast Handovers for Mobile IPv6), o FaHMA (Fast Handovers using Multicast Addressing), utilizando endereÃamento multicast para gerenciar a mobilidade nesses tipos de rede. Para fazer a anÃlise de desempenho, simulaÃÃes foram utilizadas considerando-se mÃtricas tais com o atraso do handover e a perda de pacotes como os critÃrios mais importantes para avaliar a efetividade da soluÃÃo. Os resultados destas simulaÃÃes mostraram que o FaHMA obtÃm melhores resultados que o FMIPv6, inclusive em relaÃÃo aos fatores que determinam a qualidade do funcionamento de aplicaÃÃes multimÃdias em rede. / The use of multi-interface devices such as smart phones has grown at the same time as the demands for efficient mobility services in heterogeneous networks. In this scenario, the idea of service continuity has become a crucial requirement. To achieve these demands, efficient handover schemes should be developed aiming to achieve Seamless Handover, which means the change of network domains in a transparent way and without services discontinuity to the end user. Currently, there are different schemes for handover and some of them may be used between different access technologies (Vertical Handover). However, the service time disruption is still a major problem to be solved. The main purpose of this study is to propose an improvement for Vertical Handovers using IP mobility, aiming at Seamless Handover. In this work, the framework provided by the MIH (Media Independent Handover) IEEE 802.21 is used to enable vertical handover in heterogeneous networks, and propose an extension of FMIPv6 (Fast Handovers for Mobile IPv6) called FaHMA (Fast Handovers using Multicast Addressing), using multicast in order to manage mobility in these types of networks. To make the performance analysis, we decided for simulations and we considerered metrics such as the handover delay and packet loss as the most important criteria for evaluating the effectiveness of our proposal. Simulation results have shown that FaHMA achieve better results than FMIPv6, including factors that determine the quality of operation in networked multimedia applications.

[pt] Os segmentos de geração, transmissão e distribuição constituem a cadeia produtiva do setor elétrico, sendo o consumidor ou carga o último elo que deve ser atendido pelas distribuidoras. A percepção de qualidade, e consequentemente a satisfação do cliente, está intrinsecamente relacionada, entre outros fatores, à continuidade do fornecimento assegurada pelas concessionárias. No Brasil, a Agência Nacional de Energia Elétrica (ANEEL) é responsável por regular o setor de distribuição e estabelecer indicadores de referência com o objetivo de avaliar a eficiência das concessionárias em termos de confiabilidade e qualidade do serviço prestado. Diversos fatores podem impactar a continuidade da distribuição de energia, sendo alguns mais conhecidos e gerenciáveis pelas empresas, como quedas de objetos na rede ou sobrecarga de equipamentos. No entanto, outros fatores, como restrições de acesso a determinadas áreas devido à violência e ao controle territorial por grupos criminosos, apresentam desafios complexos e de gerenciabilidade inexistente por parte das distribuidoras. Essas limitações dificultam a pronta recomposição do serviço em situações emergenciais, resultando em tempos de falha mais longos e afetando negativamente os indicadores de continuidade monitorados pela ANEEL, bem como a satisfação do consumidor. Neste contexto, a presente dissertação propõe uma metodologia focada em identificar os ativos da distribuidora localizados em áreas com evidências de violência, o que implica em acesso limitado pelas equipes de campo. É utilizada a base de dados geográfica da distribuidora (BDGD) para identificar as unidades transformadoras em áreas com evidências de violência, também delineadas por plataformas de dados públicos. Técnicas de clusterização e testes estatísticos são então utilizados para aferir se os índices de continuidade nessas áreas são significativamente diferentes e superiores aos de locais em que não se observa registros de violência. Sistemas de distribuição dos estados do Rio de Janeiro e Pernambuco são utilizados para testar a eficácia da metodologia proposta. Diversos testes são realizados e os resultados obtidos são plenamente discutidos. / [en] The segments of generation, transmission and distribution constitute the production chain of the electricity sector, with the consumer or load being the last link that must be served by the distributors. The perception of quality, and consequently customer satisfaction, is intrinsically related, among other factors, to the continuity of supply ensured by the concessionaires. In Brazil, the National Electric Energy Agency (ANEEL) is responsible for regulating the distribution sector and establishing benchmarks in order to assess the efficiency of concessionaires in terms of reliability and quality of service provided. Several factors can impact the continuity of energy distribution, some of which are better known and manageable by companies, such as falling objects on the network or overloading equipment. However, other factors, such as access restrictions to certain areas due to violence and territorial control by criminal groups, present complex challenges and non-existent manageability on the part of the distributors. These limitations make it difficult to promptly restore the service in emergency situations, resulting in longer failure durations and negatively affecting the continuity indicators monitored by ANEEL, as well as consumer satisfaction. In this context, this dissertation proposes a methodology focused on identifying the distributor s assets located in areas with evidence of violence, which implies limited access by field service teams. The distribution company s geographic database (BDGD) is used to identify transforming units in areas with evidence of violence, also delineated by public data platforms. Clustering techniques and statistical tests are then used to assess whether the continuity indices in these areas are significantly different and higher than those in places where there are no records of violence. Distribution systems in the states of Rio de Janeiro and Pernambuco are used to test the effectiveness of the proposed methodology. Several tests are carried out and the results obtained are fully discussed.

Le développement de commandes en boucle fermée pour des entraînements électriques nécessite l'installation de capteurs pour avoir l'information de la rétroaction. Cependant, un éventuel défaut survenant sur l'un des capteurs installés (de courant, de vitesse/position,…) implique un disfonctionnement de la commande conduisant dans la plupart du temps à la mise hors service du système. Ces conséquences sont contraires aux exigences des industriels qui demandent des degrés de fiabilité du système de plus en plus élevés. Des statistiques montrent que le défaut capteur est fréquent. Il est donc impératif de trouver des solutions pour assurer la continuité de service des systèmes électriques dans le cas de présence de ce type de défaut. Tout d'abord, l'étude présentée dans ce manuscrit présente les technologies des différents capteurs installés et ce pour comprendre les raisons et le type de pannes qui pourraient survenir. Ensuite, le système sur lequel la validation des algorithmes développés est décrit. Il s'agit d'un entraînement électrique basé sur une machine à Double Alimentation (MADA) fonctionnant en mode moteur et connectée au réseau via deux convertisseurs. La commande associée est une Commande Directe de Couple (CDC). Elle est validée en mode sain aussi bien par simulation qu'expérimentalement. Après, les études réalisées prennent en considération les défauts capteurs de courants alternatifs et de vitesse/position. Les algorithmes développés, permettant une continuité de service, utilisent une redondance analytique et sont basés sur l'estimation et aussi sur la Détection et l'Isolation d'un éventuel Défaut (DID). Ils sont caractérisés par leur simplicité. Aussi, ils ne sont pas gourmands en termes de consommation en ressources matérielles et leur temps d'exécution est très court. Enfin, la validation expérimentale de ces algorithmes montre bien leur efficacité en cas de défaut, vu que le système s'avère insensible au défaut et continue à fonctionner sans interruption. La commande obtenue est alors tolérante aux défauts capteurs. / The development of closed loop controls for electrical drives requires the sensor installations in order to get feed back information. Nevertheless, any occurred sensor fault (current sensor,speed/position sensor,…) shows an operation system deterioration which leads in most cases to its shut down. This consequence is in contrast to industrial expectations especially concerning the system high accuracy that they are asking for. Statistic studies point out the sensor faults as frequent. So, it is necessary to find out solutions ensuring the system service continuity in case of any sensor fault. Firstly, the study presented in this work shows the used sensor technologies in order to understand both of the reason and the kind of occurred faults. Secondly, the studied system is presented which is an electrical drive based on a Doubly Fed Induction Machine (DFIM) operating in motor mode and connected to the grid by two inverters. The control developed is a Direct Torque Control (DTC). The control validation, in healthy operating mode, is realised throw simulation and experimentally. After, a study considering alternative current sensor and speed/position sensor faults are achieved. The developed algorithms are based on signal estimation, on a Fault Detection Isolation (FDI) and reconfiguration algorithms. In fact, they are simple to carry out, they don't need much hardware resources for implementation and their execution time is short. Finally, the experimental validation of the developed algorithms shows their efficiency. The system continues working even in presence of a sensor fault. Thus, the obtained control becomes a fault tolerant control thanks to these algorithms.