Modelling and Optimisation of GSM and UMTS Radio Access Networks

The size and complexity of mobile communication networks have increased in the last years making network management a very complicated task. GSM/EDGE Radio Access Network (GERAN) systems are in a mature state now. Thus, non-optimal performance does not come from typical network start-up problems, but, more likely, from the mismatching between traffic, network or propagation models used for network planning, and their real counterparts. Such differences cause network congestion problems both in signalling and data channels. With the aim of maximising the financial benefits on their mature networks, operators do not solve anymore congestion problems by adding new radio resources, as they usually did. Alternatively, two main strategies can be adopted, a) a better assignment of radio resources through a re-planning approach, and/or b) the automatic configuration (optimisation, in a wide sense) of network parameters. Both techniques aim to adapt the network to the actual traffic and propagation conditions. Moreover, a new heterogenous scenario, where several services and Radio Access Technologies (RATs) coexist in the same area, is now common, causing new unbalanced traffic scenarios and congestion problems. In this thesis, several optimisation and modelling methods are proposed to solve congestion problems in data and signalling channels for single- and multi-RAT scenarios

Performance analysis of cellular networks.

Thesis (Ph.D.)-University of Natal, Durban, 2000.Performance analysis in cellular networks is the determination of customer orientated grade-of-service parameters, such as call blocking and dropping probabilities, using the methods of stochastic theory. This stochastic theory analysis is built on certain assumptions regarding the arrival and service processes of user-offered calls in a network. In the past, cellular networks were analysed using the classical assumptions, Poisson call arrivals and negative exponential channel holding times, borrowed from earlier fixed network analysis. However, cellular networks are markedly different from fixed networks, in that, they afford the user a unique opportunity: the ability to communicate while on the move. User mobility and various other cellular network characteristics, such as customer-billing, cell· layout and hand·off mechanisms, generally invalidate the use of Poisson arrivals and negative exponential holding times. Recent measurements on live networks substantiate this view. Consequently, over the past few years, there has been a noticeable shift towards using more generalised arrival and service distributions in the performance analysis of cellular networks. However, two shortcomings with the resulting models are that they suffer from state space explosion and / or they represent hand off traffic as a state dependent mean arrival rate (thus ignoring the higher moments of the hand-off arrival process). This thesis's contribution to cellular network analysis is a moment-based approach that avoids full state space description but ensures that the hand-off arrival process is modelled beyond the first moment. The thesis considers a performance analysis model that is based on Poisson new call arrivals, generalised hand-off call arrivals and a variety of channel holding times. The thesis shows that the performance analysis of a cellular network may be loosely decomposed into three parts, a generic cell traffic characterising model, a generic cell traffic blocking model and a quality of service evaluation model. The cell traffic characterising model is employed to determine the mean and variance of hand-off traffic offered by a cell to its neighbour. The cell traffic-blocking model is used to detennine the blocking experienced by the various traffic streams offered to each cell. The quality of service evaluation part is essentially afued-point iteration of the cell traffic characterising and cell traffic blocking parts to determine customer orientated grade-of-service parameters such as blocking and dropping probabilities. The thesis also presents detailed mathematical models for user mobility modelling. Finally, the thesis provides extensive results to validate the proposed analysis and to illustrate the accuracy of the proposed analysis when compared to existing methods

Räumlich differenzierte indexbasierte Bewertung von Sturzflut-Potenzial bei geringer Datenverfügbarkeit

Flash flood hazard maps provide an essential support to mitigate flash flood risk. In the literature, various approaches have been proposed to estimate degrees of flash flood hazard. Most of them were developed in where large inventories of historic flash floods are available. However, none of them is proved to deliver a most suitable solution for flash flood hazard assessment in ungauged basins. Owing to unfavorable data conditions, it is difficult to prove which approach is more suitable than another one. This dissertation fills this gap by introducing a new spatial index-based approach to map potential flash flood hazard areas at high spatial resolutions preferably for ungauged basins but also for any basin, which needs a quick assessment of its flash flood potential. For comparison purposes, an integrated hydrologic-hydrodynamic approach was applied to model the upper Nan River basin in Thailand. With this model approach, the spatial distributions of flash flood hazard of the upper Nan was estimated and served as a reference for the development of the new approach. On the basis of the new index-based approach, physiographic variables of the study sub-basins were computed from available digital elevation models. These variables were linearly combined and automatically weighted by means of principal component analysis (PCA) to determine flash flood potential indices (FFPI). The FFPI values based on the sub-basins could be described well by a generalized extreme value (GEV) probability distribution. The 98th percentile of the GEV probability distribution (so-called "regional" lowest classifier) was found to be suitable for identifying flash flood extents in the sub-basins by comparison to results of the integrated modeling approach. In addition, the index-based approach was applied to the upper Ping River basin in order to test the transferability of the regional lowest classifier. The identified flood hazard areas were smaller than historic inundated areas extracted from the Landsat-7 satellite imagery and the classifier was adapted. It can be stated that the new spatial index-based approach is an effective procedure for flash flood hazard assessment in any basin including ungauged basins. Future work should focus on developing an analytical routing equation to transfer rainfall information in order to extend the approach towards a (real-time) forecast.Sturzflut-Gefahrenkarten bieten eine wesentliche Unterstützung, um Schäden durch Sturzfluten zu verringern. In der Literatur werden verschiedene Ansätze vorgeschlagen, um Sturzflutgefahr abzuschätzen. Die meisten Ansätze wurden für eine gute Datenlage bezüglich historischer Sturzflutereignisse entwickelt. Keine der recherchierten Ansätze wurde jedoch als eine geeignete Lösung für den Einsatz in nicht bepegelten Einzugsgebieten angesehen. Die vorliegende Dissertation füllt diese Lücke durch die Einführung eines neu entwickelten, räumlich differenzierten, indexbasierten Ansatzes, um potenzielle Gefahrengebiete mit hoher räumlicher Auflösung auch für unbepegelte Einzugsgebiete zu adressieren. Zu Vergleichszwecken wurde ein integrierter hydrologischen-hydrodynamischer Ansatz zur Modellierung des oberen Nan-Einzugsgebiets in Thailand verwendet. Mit diesem Modellansatz wurde die räumliche Verteilung der Sturzflutgefahr des oberen Nan bestimmt und diente als Referenz für den neuen Ansatz. Grundlage des indexbasierten Ansatzes ist die Ermittlung von physiogeographischen Variablen aus digitalen Höhenmodellen. Diese Variablen wurden linear kombiniert und automatisch mittels einer Hauptkomponentenanalyse gewichtet, um räumlich differenzierte Indices des Sturzflut-Potenzials (FFPI) zu ermitteln. Die FFPI-Werte aus den Teileinzugsgebieten konnten durch die allgemeine Extremwertverteilungsfunktion gut beschrieben werden. Das 98% Perzentil dieser Extremwertverteilung (als niedrigster Klassifizierer) erwies sich durch Vergleich mit Ergebnissen des Modellierungsansatzes als gut geeignet, um die räumliche Ausdehnungen historischer Sturzfluten zu beschreiben. Zusätzlich wurde der indexbasierte Ansatz auf das obere Ping-Einzugsgebiet angewendet zur Überprüfung der Übertragbarkeit des niedrigsten Klassifizierers. Die dadurch ermittelten Gefahrengebiete waren kleiner als die historischen Überschwemmungsgebiete, die aus Satellitenbildern des Landsat-7 extrahiert wurden und der Klassifizierer wurde adaptiert. Es lässt sich festhalten, dass der neue Ansatz ein effizientes und aussagekräftiges Verfahren für die Sturzflut-Gefährdungsanalyse in beliebigen Einzugsgebieten ist. Zukünftige Arbeiten sollten sich auf die Entwicklung einer analytischen Routing-Gleichung zur Übertragung von Niederschlagsinformationen konzentrieren, um den Ansatz als Sturzflutvorhersage zu erweitern

Perception of Reverberation in Domestic and Automotive Environments

nrpages: 227status: publishe

Diseño centrado en calidad para la difusión Peer-to-Peer de video en vivo

El uso de redes Peer-to-Peer (P2P) es una forma escalable para ofrecer servicios de video sobre Internet. Este documento hace foco en la definición, desarrollo y evaluación de una arquitectura P2P para distribuir video en vivo. El diseño global de la red es guiado por la calidad de experiencia (Quality of Experience - QoE), cuyo principal componente en este caso es la calidad del video percibida por los usuarios finales, en lugar del tradicional diseño basado en la calidad de servicio (Quality of Service - QoE) de la mayoría de los sistemas. Para medir la calidad percibida del video, en tiempo real y automáticamente, extendimos la recientemente propuesta metodología Pseudo-Subjective Quality Assessment (PSQA). Dos grandes líneas de investigación son desarrolladas. Primero, proponemos una técnica de distribución de video desde múltiples fuentes con las características de poder ser optimizada para maximizar la calidad percibida en contextos de muchas fallas y de poseer muy baja señalización (a diferencia de los sistemas existentes). Desarrollamos una metodología, basada en PSQA, que nos permite un control fino sobre la forma en que la señal de video es dividida en partes y la cantidad de redundancia agregada, como una función de la dinámica de los usuarios de la red. De esta forma es posible mejorar la robustez del sistema tanto como sea deseado, contemplando el límite de capacidad en la comunicación. En segundo lugar, presentamos un mecanismo estructurado para controlar la topología de la red. La selección de que usuarios servirán a que otros es importante para la robustez de la red, especialmente cuando los usuarios son heterogéneos en sus capacidades y en sus tiempos de conexión.Nuestro diseño maximiza la calidad global esperada (evaluada usando PSQA), seleccionado una topología que mejora la robustez del sistema. Además estudiamos como extender la red con dos servicios complementarios: el video bajo demanda (Video on Demand - VoD) y el servicio MyTV. El desafío en estos servicios es como realizar búsquedas eficientes sobre la librería de videos, dado al alto dinamismo del contenido. Presentamos una estrategia de "caching" para las búsquedas en estos servicios, que maximiza el número total de respuestas correctas a las consultas, considerando una dinámica particular en los contenidos y restricciones de ancho de banda. Nuestro diseño global considera escenarios reales, donde los casos de prueba y los parámetros de configuración surgen de datos reales de un servicio de referencia en producción. Nuestro prototipo es completamente funcional, de uso gratuito, y basado en tecnologías bien probadas de código abierto

Proceedings of the Fifth International Mobile Satellite Conference 1997

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments

Information Technologies and Social Media: New Scientific Methods for the Anthropocene

The development of technology during the Anthropocene has affected science and the ways of “doing science”. Nowadays, new technologies help scientists of several disciplines by facilitating knowledge and how to manage it, but also allow for collaborative science, the so-called “Social Science”, where everyone can be a scientist and be involved in providing data and knowledge by using a computer or a smartphone without being a specialist. But is it really that simple? Actually, the daily and integrated use of different digital technologies and sharing platforms, such as social media, requires important reflections. Such reflections can lead to a rethinking of epistemologies and scientific paradigms, both in human geography and social sciences. This volume titled “Information Technologies and Social Media: New Scientific Methods for the Anthropocene” includes 10 chapters exploring some changes related to the way to do science with a multidisciplinary approach. From classroom experiences to the use of Citizen Science, from Artificial Intelligence use to how Social Media can help researchers, the book reflects on the ICT influence during the last few decades, exploring different cases, complementary perspectives and point of views