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Multicasting in Long-Term Evolution (LTE) environments poses several challenges if it is to be reliably implemented. Neither retransmission schemes nor Forward Error Correction (FEC), the traditional error correction approaches, can be readily applied to this system of communication if bandwidth and resources are to be used efficiently. A large number of network parameters and topology variables can influence the cost of telecommunication in such a system. These need to be considered when selecting an appropriate error correction technique for a certain LTE multicast deployment. This dissertation develops a cost model to investigate the costs associated with over-the-air LTE multicasting when different error correction techniques are applied. The benefit of this simplified model is an easily implementable and fast method to evaluate the communications costs of different LTE multicast deployments with the application of error correction techniques. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

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Multicasting in Long-Term Evolution (LTE) environments poses several challenges if it is to be reliably implemented. Neither retransmission schemes nor Forward Error Correction (FEC), the traditional error correction approaches, can be readily applied to this system of communication if bandwidth and resources are to be used efficiently. A large number of network parameters and topology variables can influence the cost of telecommunication in such a system. These need to be considered when selecting an appropriate error correction technique for a certain LTE multicast deployment. This dissertation develops a cost model to investigate the costs associated with over-the-air LTE multicasting when different error correction techniques are applied. The benefit of this simplified model is an easily implementable and fast method to evaluate the communications costs of different LTE multicast deployments with the application of error correction techniques. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

The mobile telecommunication industry has experienced a very rapid growth in the recent past. This has resulted in significant technological and architectural evolution in the wireless networks. The expansion and the heterogenity of these networks have made their operational cost more and more important. Typical faults in these networks may be related to equipment breakdown and inappropriate planning and configuration. In this context, automated troubleshooting in wireless networks receives a growing importance, aiming at reducing the operational cost and providing high-quality services for the end-users. Automated troubleshooting can reduce service breakdown time for the clients, resulting in the decrease in client switchover to competing network operators. The Radio Access Network (RAN) of a wireless network constitutes its biggest part. Hence, the automated troubleshooting of RAN of the wireless networks is very important. The troubleshooting comprises the isolation of the faulty cells (fault detection), identifying the causes of the fault (fault diagnosis) and the proposal and deployement of the healing action (solution deployement). First of all, in this thesis, the previous work related to the troubleshooting of the wireless networks has been explored. It turns out that the fault detection and the diagnosis of wireless networks have been well studied in the scientific literature. Surprisingly, no significant references for the research work related to the automated healing of wireless networks have been reported. Thus, the aim of this thesis is to describe my research advances on "Automated healing of LTE wireless networks using statistical learning". We focus on the faults related to Radio Resource Management (RRM) parameters. This thesis explores the use of statistical learning for the automated healing process. In this context, the effectiveness of statistical learning for automated RRM has been investigated. This is achieved by modeling the functional relationships between the RRM parameters and Key Performance Indicators (KPIs). A generic automated RRM architecture has been proposed. This generic architecture has been used to study the application of statistical learning approach to auto-tuning and performance monitoring of the wireless networks. The use of statistical learning in the automated healing of wireless networks introduces two important diculties: Firstly, the KPI measurements obtained from the network are noisy, hence this noise can partially mask the actual behaviour of KPIs. Secondly, these automated healing algorithms are iterative. After each iteration the network performance is typically evaluated over the duration of a day with new network parameter settings. Hence, the iterative algorithms should achieve their QoS objective in a minimum number of iterations. Automated healing methodology developped in this thesis, based on statistical modeling, addresses these two issues. The automated healing algorithms developped are computationaly light and converge in a few number of iterations. This enables the implemenation of these algorithms in the Operation and Maintenance Center (OMC) in the off-line mode. The automated healing methodolgy has been applied to 3G Long Term Evolution (LTE) use cases for healing the mobility and intereference mitigation parameter settings. It has been observed that our healing objective is achieved in a few number of iterations. An automated healing process using the sequential optimization of interference mitigation and packet scheduling parameters has also been investigated. The incorporation of the a priori knowledge into the automated healing process, further reduces the number of iterations required for automated healing. Furthermore, the automated healing process becomes more robust, hence, more feasible and practical for the implementation in the wireless networks.

Nowadays, with a worldwide market penetration of over 50% in the mobile telecommunications sector, there is also an unrelenting demand from the subscribers for ever increasing transmission rates and availability of broadband-like experience on the handset. Due to this, research in next-generation networks is rife. Such systems are expected to achieve peak data rates of up to 1 Gbps through the use of innovative technologies such as multiple-input and multipleoutput (MIMO) and orthogonal frequency division multiple access (OFDMA). Two more ways of boosting capacity have also been identified: shrinking cell sizes and greater reuse of resources in the same area. This forms the foundation of the research presented in this thesis. For operators, the costs involved with planning and deploying additional network infrastructure to provide a dense coverage of small, high capacity cells cannot be justified. Femto-cells, however, promise to fulfil this function. These are user-deployed mini base stations (BSs), known as home evolved NodeBs (HeNBs), which are envisaged to be commonplace in homes and offices in the coming years. Since they drastically reduce communication distances to user equipments (UEs) and reuse the resources already utilised in the macro-cell, they help boost the system capacity significantly. However, there are issues to be addressed with the deployment of femto-cells, such as increased interference to the system and methods of access. These and other problems are discussed and analysed in this thesis. One of the first steps towards femtocell research has been the study of the time division duplex (TDD) underlay concept, whereby an indoor UE acts as a relay between the evolved NodeB (eNB) and other indoor UEs. In order to gain a deeper understanding of how and under what conditions such a self-organising network can be deployed, a mathematical analysis of the distribution of path losses in a network of uniformly distributed nodes has been performed. In connection with this, research has also been done in the identification of well connected nodes in such networks. Next, extensive simulations on traditional cellular networks with embedded femto-cells have been carried out in order to demonstrate the benefits of femto-cell deployment. This research has shown that femto-cells can cause severe downlink (DL) interference to badly placed macro UEs. Finally, a novel interference avoiding technique that addresses this problem is investigated.

Ingeniero Civil Electricista / Las redes móviles de tercera generación (3G) brindan servicios de voz y datos en forma separada mediante conmutación de circuitos y conmutación de paquetes, en una misma tecnología. En cambio, una red Long Term Evolution (LTE) presenta un enfoque exclusivo al uso de datos de manera All IP (todo con Internet Protocol), de modo que las llamadas deben ser cursadas mediante Voz sobre IP (VoIP) en una red de conmutación de paquetes. Esto se logra haciendo uso de un núcleo de paquetes IP Multimedia Subsystem (IMS), a través de servidores Session Initiation Protocol (SIP). De esta manera, se heredan los problemas de un servicio ofrecido por mejor esfuerzo mediante IP, surgiendo la gran necesidad de establecer Calidad de Servicio (QoS), mecanismo que establece prioridad de tráfico según las aplicaciones a las cuales acceden los usuarios. Así, resulta obligatorio monitorear el correcto funcionamiento de este mecanismo para cumplir con los acuerdos de nivel de servicio establecidos con el usuario. En este escenario, las mediciones de Calidad de Experiencia (QoE), son clave. El presente trabajo de título tiene como objetivo general diseñar e implementar una metodología para medir indicadores de QoE y QoS en aplicaciones multimedia Over The Top (OTT), en una red de laboratorio LTE/IMS. Para esto, se implementa un IMS Open Source en una red de área local (LAN), lo que sirve como prototipo de verificación para el correcto desempeño de los servicios y herramientas de medición, así como también para tener un punto de comparación de los valores logrados por la metodología en el caso LTE/IMS. El resultado del trabajo es una metodología compuesta por 5 pruebas de concepto, las cuales miden un indicador específico de calidad de acuerdo al servicio y a la modalidad de acceso (Internet, o vía operador). Dichas pruebas son verificadas en dos escenarios de tráfico: (i) el óptimo, que consiste en no establecer más de una sesión multimedia en la red; y (ii) el congestionado, que emula el comportamiento de una red con tráfico. Se logra obtener indicadores de calidad en las redes LAN/IMS y LTE/IMS. De lo anterior, se obtienen herramientas docentes para realizar capacitaciones y cursos de LTE e IMS orientados al estudio de QoS y QoE en la Universidad de Chile. Este trabajo constituye, por un lado, un acercamiento práctico a la medición y monitoreo de QoE aplicable a una red móvil LTE; y, por otro, a nivel docente, entrega una plataforma de medición y de estudio para las nuevas arquitecturas móviles. Esto último permite proponer como trabajos futuros los siguientes temas: estudio del impacto de la movilidad y de las políticas de control de recursos en el QoE, en servicios sobre LTE; implementación de la interconexión de LTE a la telefonía fija a través de IMS y una Central Telefónica IP tipo Asterisk; y, por último, un estudio del sincronismo audio-video en un servicio de videostreaming montado sobre LTE haciendo uso de herramientas de medición de QoE.

[pt] A chegada da tecnologia 4G acontece simultaneamente com a tecnologia que hoje temos (2G e 3G). Deste modo, uma pergunta natural é se elas vão conseguir coexistir ou se, no futuro, apresentarão problemas de coexistência. Para responder a estas perguntas, é preciso pesquisar para podermos predizer se, de alguma maneira, há possibilidade de falhas no futuro. E é assim que poderíamos explicar interferência, que é um problema que sempre existe e que se opõe à boa qualidade de serviço. No Brasil, já se discute o uso da frequência de 2.5 GHz, para serviços de 4a geração, por atender melhor as necessidades dos usuários. Isto que acontecerá também se, de alguma maneira, usarmos outras frequências como no caso de 900 MHz, que é considerada uma banda muito disputada na Europa. Existem operadoras que começaram a fazer testes com esta banda, e isso nos faz pensar que, de qualquer forma, teremos que conviver com a mesma banda em diferentes tecnologias. Assim, este trabalho apresenta um estudo de simulação de diversos casos de interferência e como cada um deles irá afetar o desempenho dos sistemas 4G coexistindo com sistemas mais antigos. / [en] The arrival of 4G technology takes place simultaneously with the technology we have today (2G and 3G). Thus, a natural question is whether they will be able to coexist in the future or will present problems of coexistence. In order to answer these questions, it is necessary to search predicting if there is possibility of failure in the future. And that s how we explain interference, which is a problem that always exists and precludes good quality of service. In Brazil there is discussion about the use of 2.5 GHz frequency for 4G to better meet the users’needs. This will happened if in some way we use other frequencies as the case of 900 MHz band which is considered a hard fought in Europe. There are carriers that have begun to experiment with this band, and this makes us think that in any way we will live with different technologies in the same band. Thus, this work presents a simulation study of several cases of interference, in which each will affect the performance of 4G systems coexisting with older systems.

As a result of the constant efforts to improve mobile system performance and spectral efficiency, the 3GPP standardization forum is currently defining new architectural and functional requirements that hope to ensure long-term evolution (specifically defined as the “Long-Term Evolution (LTE) concept”) and general future competitiveness of the 2G and 3G radio access technologies. Previous discussions on LTE efficiency have been focused on general assumptions on signaling overhead and overall system capacity, based on experience from existing mobile systems. However, as 3GPP standardization has become more mature (although not yet settled), there is a need to investigate how different potential LTE services will be affected by the use of available overhead information and basic scheduling algorithms. This thesis investigates the lower protocol layers’ overhead impacts on the downlink for different packet switched services, in an LTE radio access network (RAN). Results show that the use of RTP/TCP/IP header compression (ROHC) is the single most important factor to reduce payload overhead, for packet sizes of ~1kB or smaller. However, for packets larger than ~1 kB, the use of ROHC becomes insignificant. Protocol headers – including the AMR frame header, RLC/MAC headers, and CRC where applicable – remain the largest part of payload overhead regardless of packet size and header compression (ROHC). For VoIP over the UDP protocol (with ROHC), RLC/MAC headers constitute the largest part of protocol headers. For TCP/IP applications (without ROHC), TCP/IP headers are predominant. Services that require packet sizes beyond ~1 kB will require about the same power per payload bit regardless of percentage of payload overhead. / Som ett resultat av ständiga ansträngningar att förbättra såväl prestanda som spektrumeffektivitet för mobila system, definierar 3GPPs standardiseringsforum nya krav på arkitektur och funktionalitet. Dessa är avsedda att säkerställa långsiktig utveckling (explicit definierat som konceptet “Long-Term Evolution (LTE)”, samt framtida konkurrenskraft för både 2G och 3G som radioaccess-teknologier. Tidigare diskussioner rörande effektivitet inom LTE har fokuserat på allmänna antaganden vad gäller kontrolldata för signallering och övergripande systemprestanda. Dessa har i sin tur baserats på erfarenheter från existerande mobilsystem. När standardiseringen inom 3GPP mognar uppstår nu ett behov av att undersöka hur olika tjänster inom LTE påverkas, av såväl hur man använder den kontrollinformation som finns tillgänglig, som av basala algoritmer for schemaläggning av resurser. Denna rapport undersöker påverkan från lägre protokoll-lagers kontrollinformation på nerlänken hos olika paket-kopplade tjänster inom ett radioaccessnät för LTE. Resultaten visar att användandet av ROHC (som packar kontrollinformation för protokollen RTP/TCP/IP), är det ensamt viktigaste bidraget till minskad kontrollinformation i relation till informationsbitar för paketstorlekar upp till c:a 1kB. För större paket är vinsten med ROHC dock försumbar. Kontrollinformation för protokoll – inkluderat data avsett för AMR-tal-ramen, RLC/MAC-protokollen, samt CRC – utgör för övrigt en stor del av kontrollinformationen relativt informationsbitar, oavsett paketstorlek och packning av kontrolldata. Tjänster som kräver paketstorlekar på över c:a 1 kB kräver uppskattningsvis samma mängd energi per informationsbit, oavsett andelen kontrollinformation.