Self-organising network management for heterogeneous LTE-advanced networks

This thesis was submitted for the award of Doctor of Philosophy and awarded by Brunel University LondonSince 2004, when the Long Term Evolution (LTE) was first proposed to be publicly available in the year 2009, a plethora of new characteristics, techniques and applications have been constantly enhancing it since its first release, over the past decade. As a result, the research aims for LTE-Advanced (LTE-A) have been released to create a ubiquitous and supportive network for mobile users. The incorporation of heterogeneous networks (HetNets) has been proposed as one of the main enhancements of LTE-A systems over the existing LTE releases, by proposing the deployment of small-cell applications, such as femtocells, to provide more coverage and quality of service (QoS) within the network, whilst also reducing capital expenditure. These principal advantages can be obtained at the cost of new challenges such as inter-cell interference, which occurs when different network applications share the same frequency channel in the network. In this thesis, the main challenges of HetNets in LTE-A platform have been addressed and novel solutions are proposed by using self-organising network (SON) management approaches, which allows the cooperative cellular systems to observe, decide and amend their ongoing operation based on network conditions. The novel SON algorithms are modelled and simulated in OPNET modeler simulation software for the three processes of resource allocation, mobility management and interference coordination in multi-tier macro-femto networks. Different channel allocation methods based on cooperative transmission, frequency reuse and dynamic spectrum access are investigated and a novel SON sub-channel allocation method is proposed based on hybrid fractional frequency reuse (HFFR) scheme to provide dynamic resource allocation between macrocells and femtocells, while avoiding co-tier and cross-tier interference. Mobility management is also addressed as another important issue in HetNets, especially in hand-ins from macrocell to femtocell base stations. The existing research considers a limited number of methods for handover optimisation, such as signal strength and call admission control (CAC) to avoid unnecessary handovers, while our novel SON handover management method implements a comprehensive algorithm that performs sensing process, as well as resource availability and user residence checks to initiate the handover process at the optimal time. In addition to this, the novel femto over macro priority (FoMP) check in this process also gives the femtocell target nodes priority over the congested macrocells in order to improve the QoS at both the network tiers. Inter-cell interference, as the key challenge of HetNets, is also investigated by research on the existing time-domain, frequency-domain and power control methods. A novel SON interference mitigation algorithm is proposed, which is based on enhanced inter-cell interference coordination (eICIC) with power control process. The 3-phase power control algorithm contains signal to interference plus noise ratio (SINR) measurements, channel quality indicator (CQI) mapping and transmission power amendments to avoid the occurrence of interference due to the effects of high transmission power. The results of this research confirm that if heterogeneous systems are backed-up with SON management strategies, not only can improve the network capacity and QoS, but also the new network challenges such as inter-cell interference can also be mitigated in new releases of LTE-A network

Descentralização da gestão da mobilidade IP nas redes do futuro

Doutoramento em Engenharia ElectrotécnicaThe massive adoption of sophisticated mobile devices and applications led to the increase of mobile data in the last decade, which it is expected to continue. This increase of mobile data negatively impacts the network planning and dimension, since core networks are heavy centralized. Mobile operators are investigating atten network architectures that distribute the responsibility of providing connectivity and mobility, in order to improve the network scalability and performance. Moreover, service providers are moving the content servers closer to the user, in order to ensure high availability and performance of content delivery. Besides the e orts to overcome the explosion of mobile data, current mobility management models are heavy centralized to ensure reachability and session continuity to the users connected to the network. Nowadays, deployed architectures have a small number of centralized mobility anchors managing the mobile data and the mobility context of millions of users, which introduces issues related to performance and scalability that require costly network mechanisms. The mobility management needs to be rethought out-of-the box to cope with atten network architectures and distributed content servers closer to the user, which is the purpose of the work developed in this Thesis. The Thesis starts with a characterization of mobility management into well-de ned functional blocks, their interaction and potential grouping. The decentralized mobility management is studied through analytical models and simulations, in which di erent mobility approaches distinctly distribute the mobility management functionalities through the network. The outcome of this study showed that decentralized mobility management brings advantages. Hence, it was proposed a novel distributed and dynamic mobility management approach, which is exhaustively evaluated through analytical models, simulations and testbed experiments. The proposed approach is also integrated with seamless horizontal handover mechanisms, as well as evaluated in vehicular environments. The mobility mechanisms are also speci ed for multihomed scenarios, in order to provide data o oading with IP mobility from cellular to other access networks. In the pursuing of the optimized mobile routing path, a novel network-based strategy for localized mobility is addressed, in which a replication binding system is deployed in the mobility anchors distributed through the access routers and gateways. Finally, we go further in the mobility anchoring subject, presenting a context-aware adaptive IP mobility anchoring model that dynamically assigns the mobility anchors that provide the optimized routing path to a session, based on the user and network context. The integration of dynamic and distributed concepts in the mobility management, such as context-aware adaptive mobility anchoring and dynamic mobility support, allow the optimization of network resources and the improvement of user experience. The overall outcome demonstrates that decentralized mobility management is a promising direction, hence, its ideas should be taken into account by mobile operators in the deployment of future networks.Na última década verificou-se uma massificação dos dispositivos móveis e das suas aplicações, o que tem vindo a aumentar o consumo de dados móveis. Este aumento dificulta o planeamento e dimensionamento das redes devido principalmente aos modelos extremamente centralizados adoptados por estas. Os operadores móveis têm vindo a estudar modelos mais até para as redes, os quais distribuem a responsabilidade de fornecer conectividade e mobilidade, no sentido de melhorar a escalabilidade e desempenho da rede. Além disso, de forma a garantir um desempenho elevado na entrega dos conteúdos, os fornecedores de serviço têm vindo a mover os servidores de conteúdos para locais mais próximos do utilizador. Apesar do esforço na procura de soluções para o crescente consumo de dados móveis, os modelos atuais de gestão de mobilidade são demasiado centralizados para conseguir assegurar a continuidade de sessão aos utilizadores conectados à rede. As arquiteturas implementadas têm um número muito reduzido de âncoras móveis centralizadas que gerem todos os dados móveis e a informação de contexto da mobilidade, o que leva a uma diminuição de desempenho e escalabilidade, solucionadas através de mecanismos de rede dispendiosos. A gestão da mobilidade precisa de ser repensada de forma a poder lidar com arquiteturas de rede até com a distribuição dos servidores de conteúdos para nós mais próximos dos utilizadores, que é o objectivo principal da Tese apresentada. Primeiro, é apresentada a caracterização da gestão de mobilidade em blocos funcionais, a interação entre eles e potenciais agrupamentos dos mesmos. A gestão da mobilidade descentralizada é estudada através de modelos analíticos e simulações, em que diferentes abordagens distribuem as funcionalidades da mobilidade pela rede. Como resultado deste estudo verificou-se que a descentralização da mobilidade traz vantagens claras. Com base nestes resultados foi proposta uma nova abordagem de gestão de mobilidade distribuída e dinâmica, que é exaustivamente avaliada através de modelos analíticos, simulações e experiências numa bancada de testes. A abordagem proposta é também integrada com mecanismos de handovers horizontais transparentes, assim como é avaliada em ambientes veiculares. Os mecanismos de mobilidade da abordagem proposta são também especificados para cenários de multihoming, de forma a proporcionar o offloading de dados com suporte de mobilidade das redes celulares para outras redes de acesso. Com o objectivo de optimizar o encaminhamento de dados móveis, foi criada uma nova estratégia para o suporte da mobilidade localizada, em que um sistema de replicação de bindings é integrado nas âncoras de mobilidade distribuídas através dos routers de acesso e dos gateways. Finalmente apresenta-se um modelo de ancoramento adaptativo para a mobilidade com base em contexto, o qual dinamicamente determina as âncoras de mobilidade que oferecem a melhor rota para uma dada sessão, baseado na informação do utilizador e da rede. A integração de conceitos de dinamismo e de distribuição na gestão da mobilidade, como o ancoramento adaptativo e o suporte dinâmico da mobilidade, permitem a optimização dos recursos da rede e uma melhor experiência por parte do utilizador. Os resultados demonstram, de uma forma geral, que a gestão descentralizada da mobilidade é um caminho promissor, logo este deve ser tomado em consideração pelas operadoras móveis aquando do desenvolvimento das redes do futuro

Distribuição de vídeo para grupos de utilizadores em redes móveis heterogéneas19

The evolutions veri ed in mobile devices capabilities (storage capacity, screen resolution, processor, etc.) over the last years led to a signi cant change in mobile user behavior, with the consumption and creation of multimedia content becoming more common, in particular video tra c. Consequently, mobile operator networks, despite being the target of architectural evolutions and improvements over several parameters (such as capacity, transmission and reception performance, amongst others), also increasingly become more frequently challenged by performance aspects associated to the nature of video tra c, whether by the demanding requirements associated to that service, or by its volume increase in such networks. This Thesis proposes modi cations to the mobile architecture towards a more e cient video broadcasting, de ning and developing mechanisms applicable to the network, or to the mobile terminal. Particularly, heterogeneous networks multicast IP mobility supported scenarios are focused, emphasizing their application over di erent access technologies. The suggested changes are applicable to mobile or static user scenarios, whether it performs the role of receiver or source of the video tra c. Similarly, the de ned mechanisms propose solutions targeting operators with di erent video broadcasting goals, or whose networks have di erent characteristics. The pursued methodology combined an experimental evaluation executed over physical testbeds, with the mathematical evaluation using network simulation, allowing the veri cation of its impact on the optimization of video reception in mobile terminalsA evolução veri cada nas características dos dispositivos moveis (capacidade de armazenamento, resolução do ecrã, processador, etc.) durante os últimos anos levou a uma alteração signi cativa nos comportamentos dos utilizadores, sendo agora comum o consumo e produção de conteúdos multimédia envolvendo terminais móveis, em particular o tráfego vídeo. Consequentemente, as redes de operador móvel, embora tendo também sido alvo constante de evoluções arquitecturais e melhorias em vários parâmetros (tais como capacidade, ritmo de transmissão/recepção, entre outros), vêemse cada vez mais frequentemente desa adas por aspectos de desempenho associados à natureza do tráfego de vídeo, seja pela exigência de requisitos associados a esse serviço, quer pelo aumento do volume do mesmo nesse tipo de redes. Esta Tese propôe alterações à arquitetura móvel para a disseminação de vídeo mais e ciente, de nindo e desenvolvendo mecanismos aplicáveis à rede, ou ao utilizador móvel. Em particular, são focados cenários suportados por IP multicast em redes móveis heterogéneas, isto é, com ênfase na aplicação destes mecanismos sobre diferentes tecnologias de acesso. As alterações sugeridas aplicam-se a cenários de utilizador estático ou móvel, sendo este a fonte ou receptor do tráfego vídeo. Da mesma forma, são propostas soluções tendo em vista operadores com diferentes objectivos de disseminação de vídeo, ou cujas redes têm diferentes características. A metodologia utilizada combinou a avaliação experimental em testbeds físicas com a avaliação matemática em simulações de redes, e permitiu veri car o impacto sobre a optimização da recepção de vídeo em terminais móveisPrograma Doutoral em Telecomunicaçõe

Voice traffic bicasting enhancements in mobile HSPA network

This paper discusses methods for improving the effectiveness of delivering voice traffic over High-Speed Downlink Packet Access (HSDPA) network by employing transmission diversity with Single-Frequency Dual-Cell (SF-DC) Aggregation that is part of the Multiflow specification. SF-DC Aggregation allows the user to be served at the same time by two different cells. The enhancements discussed in the paper capitalize strongly on the availability of the composed Channel Quality Indication (CQI) feedback at both serving cells. According to the results obtained from the network simulations, the ability to select the better channel for each voice transmission significantly decreases the required transmission power of the cell, thus also improving the residual cell capacity available for best effort (BE) traffic. The required updates are completely software-based and are applied only in the access network, making them transparent to user terminal.peerReviewe

Arquitectura de red de acceso móvil de cuarta generación : mobile-IP RAN

Esta tesis aborda el problema de las arquitecturas de acceso radio, en el ámbito de las redes móviles de cuarta generación definidas en entornos de movilidad IP. Uno de los principales beneficios del uso estas propuestas es la simplificación de la red móvil, haciéndola menos dependiente de la tecnología de acceso radio, y por ende permitiendo el uso de una red troncal común a las diferentes tecnologías radio existentes. En estas redes, la movilidad del terminal, la infraestructura de red y la seguridad son los aspectos más importantes que se han tomado en consideración en su diseño. A pesar de los avances en la investigación y estandarización de los mecanismos de movilidad basados en IP, existen aún limitaciones en la funcionalidad ofrecida por las redes de acceso radio propuestas. Estas limitaciones se refieren a servicios de la red de acceso radio, que no son específicos al nivel de red (IP), pero que deben ofrecerse por la red para el correcto funcionamiento de los servicios generales de la red móvil, e incluyen los servicios de gestión de los recursos radio, movilidad (handover), sincronización de usuario y red, descubrimiento de servicios y cálculo de la posición del móvil. El objetivo principal de esta tesis es la definición de una red de acceso radio basada en IP móvil que integre las principales funciones de las redes de acceso móvil de tercera generación y aquellas consideradas de cuarta generación. Esta nueva arquitectura permite compartir la infraestructura de acceso radio entre las distintas tecnologías radio existentes, simplificando la red y los costos asociados. Asimismo, los proveedores de servicios móviles podrán incorporar de forma integrada nuevas tecnologías radio, sin necesidad de añadir más infraestructura que la equivalente a las estaciones base. Las aportaciones principales de esta tesis, dentro del objetivo general, se pueden resumir de la siguiente manera. En primer lugar, se definen los requisitos que debe cumplir la red de acceso móvil de cuarta generación, en cuanto a los servicios de red y usuario proporcionados. La segunda aportación, y considerada la aportación principal, es la definición de una arquitectura de red de acceso basada en IPv6 móvil, denominada Mobile-IP RAN, que incluye la definición de los elementos de red que la componen, así como sus interfaces y protocolos, que permite ofrecer los servicios de acceso a la red, movilidad de usuario, transferencia de datos, sincronización y localización de usuarios. Como parte de la arquitectura, se define, a través de diagramas de secuencia de mensajes, el comportamiento dinámico de las principales funciones proporcionadas por la red de acceso propuesta. Por último, se lleva a cabo la evaluación de los modelos de movilidad, de determinación de la posición (como parte del servicio de localización de usuario) y de sincronización propuestos, analizando sus parámetros fundamentales que permitan optimizar el desempeño de estos modelos, así como su aplicabilidad en las distintas redes de acceso radio. ______________________________________________This thesis approaches the architecture of radio access networks in the context of fourth generation mobile networks, these being defined in IP mobility environments. One of the main benefits of these proposals is the simplification of the mobile network, now less dependent of the radio access technologies, and allowing the use of a common core network for all existing radio technologies. On these proposals, user mobility, network infrastructure and security are main aspects considered on the design. In spite of the advances on research and standardization of the IP-based mobility mechanisms, there are still limitations in the features offered by the proposed radio access networks. These limitations refers to radio access network service features, not specific to the (IP) network layer, but necessary for the correct operation of the general network and user services, that includes radio resource management, mobility (e.g. handover), network and user synchronization, service discovery and user position calculation. The main objective of this thesis is the definition of a radio access network architecture based on Mobile IPv6 that integrates the main features of the third-generation mobile access networks and those of the fourth generation. This architecture allows the use of the radio access infrastructure among the different existing radio access technologies, simplifying the network and its associated costs. Moreover, with this architecture, mobile service providers may incorporate new radio technologies in a seamless way, without adding more infrastructure than the base stations. The main contributions of this work can be summarized as follows. First, we define the requirements of the fourth-generation radio access networks related to the network and user services provided. Second, and considered the main contribution of this thesis, is the definition of a Mobile-IPv6 based radio access network architecture, named Mobile-IP RAN, that includes the definition of its network elements, as well as its network interfaces and protocols, that allow services including network access, user mobility, user data transfer, synchronization and location services. As part of the architecture, and through the use of Message Sequence Charts, we define the dynamic behavior of the main features offered by the proposed access network. Last, we perform the evaluation of the proposed mobility, position determination and synchronization models, analyzing their main parameters as well as their applicability in different radio access networks