In this thesis, we propose two mechanisms, stream splitting and merging, to fully utilize the bandwidth in a mixed wired and wireless network. The two mechanisms implemented on a SVC Streaming Gateway (SSG) mainly exploit the characteristics of multi-layer SVC (Scalable Video Coding). In the stream splitting mechanism, the available bandwidth can be calculated on SSG, so that an adequate number of layers of a SVC stream can be determined for splitting. In the stream merging mechanism, when the available bandwidth is increased, a stream with more number of enhancement layers can be extracted to merge onto a stream with less number of layers. Additionally, when two streams pass through SSG concurrently, one stream may arrive at SSG faster due to different traffic conditions. If one stream with more SVC layers is faster than the one with less SVC layers, we buffer the packets of the faster stream on SSG, so that the buffered packets can be merged to the top of SVC layers of the slow stream. On the other hand, if one stream with more SVC layers is slower than the one with less SVC layers, to effectively merge the enhancement layers of the slow stream onto the faster stream, SSG will delay the packets of the faster stream to wait for the packets of the slow stream. Finally, we implement these two mechanisms on the Linux platform. In the experiments, we measure buffer delay, queue length, and the number of merged packets to demonstrate that the two proposed mechanisms can effectively improve the picture freeze-up and mosaic phenominon.

No description available.

Internet applications are becoming more and more flexible to support diverge user demands and network conditions. This is reflected by technical concepts, which provide new adaptation mechanisms to allow fine grained adjustment of the application quality and the corresponding bandwidth requirements. For the case of video streaming, the scalable video codec H.264/SVC allows the flexible adaptation of frame rate, video resolution and image quality with respect to the available network resources. In order to guarantee a good user-perceived quality (Quality of Experience, QoE) it is necessary to adjust and optimize the video quality accurately. But not only have the applications of the current Internet changed. Within network and transport, new technologies evolved during the last years providing a more flexible and efficient usage of data transport and network resources. One of the most promising technologies is Network Virtualization (NV) which is seen as an enabler to overcome the ossification of the Internet stack. It provides means to simultaneously operate multiple logical networks which allow for example application-specific addressing, naming and routing, or their individual resource management. New transport mechanisms like multipath transmission on the network and transport layer aim at an efficient usage of available transport resources. However, the simultaneous transmission of data via heterogeneous transport paths and communication technologies inevitably introduces packet reordering. Additional mechanisms and buffers are required to restore the correct packet order and thus to prevent a disturbance of the data transport. A proper buffer dimensioning as well as the classification of the impact of varying path characteristics like bandwidth and delay require appropriate evaluation methods. Additionally, for a path selection mechanism real time evaluation mechanisms are needed. A better application-network interaction and the corresponding exchange of information enable an efficient adaptation of the application to the network conditions and vice versa. This PhD thesis analyzes a video streaming architecture utilizing multipath transmission and scalable video coding and develops the following optimization possibilities and results: Analysis and dimensioning methods for multipath transmission, quantification of the adaptation possibilities to the current network conditions with respect to the QoE for H.264/SVC, and evaluation and optimization of a future video streaming architecture, which allows a better interaction of application and network. / Die Applikationen im Internet passen sich immer besser an unterschiedliche Anforderungen der Nutzer und variierende Netzwerkbedingungen an. Neue Mechanismen ermöglichen die zielgerichtete Anpassung der Anwendungsqualität und damit der benötigten Bandbreite. Im Falle von Videostreaming ermöglicht der skalierbare Videocodec H.264/SVC, die flexible Veränderung der Bildwiederholungsrate, der Auflösung des Videos und der Bildqualität an die vorhandenen Ressourcen im Netzwerk. Um eine gute vom Nutzer erfahrene Dienstgüte (Quality of Experience, QoE) zu garantieren, muss die Videoqualität richtig angepasst und optimiert werden. Aber nicht nur die Anwendungen des heutigen Internets haben sich verändert. Gerade in den letzten Jahren entstanden neue Netzwerk- und Transporttechnologien, welche eine flexiblere und effizientere Nutzung der Kommunikationsnetze erlauben. Eine dieser Techniken ist die Virtualisierung von Netzwerken. Sie erlaubt es auf einem gemeinsamen physikalischen Netz verschiedene logische Netze zu betreiben, die zum Beispiel Anwendungs-abhängige Adressierung unterstützen, eigene Namensgebung erlauben oder ein individuelles Ressourcen Management ermöglichen. Neuartige Transportmechanismen wie Mehrpfadübertragung auf Netzwerk- und Transportebene des ISO/OSI Stacks streben eine effiziente Ausnutzung der zur Verfügung stehenden Übertragungsmöglichkeiten an. Doch die simultane Übertragung von Daten über heterogene Kommunikationspfade und –technologien führt unausweichlich zu einer Veränderung der Reihenfolge, in der die Pakete ankommen. Es werden zusätzliche Mechanismen und Puffer benötigt, um die ursprüngliche Paketreihenfolge wieder herzustellen und so einen störenden Einfluss auf den Datentransport zu verhindern. Die richtige Dimensionierung dieser Puffer sowie die Klassifizierung des Einflusses von variierenden Pfadparametern wie Bandbreite und Verzögerungen setzen passende Evaluierungsmethoden voraus. Darüber hinaus werden für die Auswahl von geeigneten Pfaden aus einer Menge vorhandener Pfade echtzeitfähige Bewertungsmechanismen benötigt. Eine bessere Interaktion zwischen Applikationen und Netzwerk und der damit verbundene Informationsaustausch ermöglicht die effiziente Anpassung der Applikationsqualität an das Netzwerk und umgekehrt. Diese Doktorarbeit analysiert eine auf Mehrpfadübertragung und skalierbarer Videokodierung basierende Videostreaming Architektur und erarbeitet die folgenden Optimierungsmöglichkeiten und Auswertungen: Analyse- und Dimensionierungsmethoden für Mehrpfadübertragung, Quantifizierung der Anpassungsmöglichkeiten von SVC an das Netzwerk unter Berücksichtigung der QoE und Evaluierung und Optimierung einer zukünftigen Videostreaming Architektur, welche eine stärkere Interaktion zwischen Applikation und Netzwerk ermöglicht.

The hierarchical B picture coding is introduced into the extension of H.264/AVC in order to improve coding performance and provide temporal scalability as well. In general, coding performance is affected by the content variation in each GOP (Group of Picture). Therefore, the ways to determine the size of sun-GOP is a critical problem for video coding. In this thesis, the adaptive GOP structure determination scheme is proposed to select the appropriate sub-GOP size with content complexity consideration. We compute the frame difference by hierarchical B picture structure and use the information to be a basis of sub-GOP decision. Hence, we can get proper combination of sub-GOP. Experimental results show the RD curves that our proposed method compares with the fixed GOP setting in the existing hierarchical B picture coding of SVC.

No description available.

Ingeniero Civil Eléctrico / Los equipos FACTS cada día son más comunes en el mundo gracias al avance de la tecnología en electrónica y semiconductores, permitiendo así operar de manera más holgada los crecientes sistemas eléctricos. En especial, el Compensador Estático de Reactivos (CER), ha tenido gran utilidad en Chile debido a su eficaz control de voltaje en sistemas radiales. Ya se han instalado 5 de estos equipos, los 3 más recietes a partir del año 2000 cuyos nombres son SVC Puerto Montt , SVC Polpaico y SVC Cerro Navia , propiedades de Transelec. Bajo este contexto, el objetivo de este trabajo de título es instruir al lector sobre esta tecnología de compensación que se usa en el país explicando su funcionamiento teórico y práctico. Para eso se diseña y construye un CER a escala para laboratorio basándose en prototipos existentes en la literatura y utilizando un microprocesador vigente. Además el modelo a escala es capaz de operar en una red de comunicaciones bajo el protocolo Modbus. Previo al diseño se revisa el estado de arte de los compensadores estáticos de reactivos tanto a escala como para aplicaciones de potencia, estudiando también su funcionamiento y principales componentes. Se revisa específicamente el modelo del microprocesador a utilizar en el modelo a escala junto con su programación y manejo. El diseño empleado consiste en un banco trifásico de inductancias junto a dos bancos de condensadores, operados por tiristores y relés respectivamente, conectados a la red de baja tensión mediante un transformador trifásico y coordinados por un sistema de control electrónico. Se realiza un algoritmo de adquisición de variables para la medición de la tensión en las líneas mediante conversión análoga digital, además de implementar un algoritmo de disparo en las inductancias para control de potencia. De la construcción final se obtiene un banco de inductancias junto a las placas electrónicas de disparo, adquisición y alimentación que componen el CER a escala. Como desarrollo futuro se propone programar un control PI en el microprocesador y mejorar la interfaz de adquisición de datos realizada en Matlab-Simulink.

In this Thesis, we propose a mechanism to dynamically adjust the video bit rates through the segmentation and the reassembly of SVC (Scalable Video Coding) segments in a P2P network. At the transmitter, an SVC film is segmented into a number of segments with different sizes. Each segment is further chopped into Torrents according to three scalabilities of SVC (Temporal, Quality, and Spatial). The Torrents with three scalabilities are referred to as 3D-Torrents. At the receiver, we present three approaches of grabbing Torrents (Temporal-First, Quality-First and Interleaving) form P2P networks to validate that the proposed 3D-Torrent reassembly can adapt to different bandwidths and to fit different hardware equipments so that any possible video freeze-up time can be avoided. To demonstrate how the proposed 3D-Torrent reassembly affect video bit rates in the P2P video streaming environment, we implement the segmentation, grabbing, and reassembly of Torrents on a Linux platform. In the P2P network built by Hadoop, we study (i) the video freeze-up time with/without adopting 3D-Torrent reassembly, (ii) video quality under different grabbing approaches using two different types of video, static and active background. To compare the video quality at the transmitter to that at the receiver, we modify the conventional PSNR equation. Two new dimensions, Temporal and Spatial, are included in the new PSNR3D equation to compare the video quality between the transmitter and the receiver. From the experimental results, we observe that the freeze-up time approaches zero using the 3D-Torrent reassembly and video bit rates can be dynamically adjusted according to the available bandwidth.

This thesis proposes a strategy for enhancing the efficiency of scalable H.264/AVC video transmission over multi-input multi-output (MIMO) and cooperative communication systems. For scalable video coding (SVC) transmission over MIMO wireless systems, a channel selection algorithm is used to enhance transmission rate. The proposed algorithm allows SVC layers to select channels individually in wireless MIMO systems based on channel state information for transmission rate enhancement. Here, this difficult problem is converted into a mathematical optimization problem to improve SVC performance during video transmission. Experimental results show that the proposed method achieves a higher transmission rate over MIMO systems compared to the existing scheme. For SVC transmission over cooperative communication systems, the algorithm allows each SVC layer to choose an appropriate relay based on channel conditions and SVC layer priority. Thus, SVC data is protected effectively. Experimental results show that video quality obtained by the algorithm exceeds that of non-cooperative systems.

Scalable video coding (SVC) supports full scalability by extracting a partial bitstream to adapt to transmission and display requirements in multimedia applications. Most conventional video content is stored in non-scalable format, e.g., H.264/AVC, necessitating the development of an efficient video transcoding from a conventional format to a scalable one. This work describes a fast video transcoding architecture that overcomes the complexity of different coding structures between H.264/AVC and SVC. The proposed algorithm simplifies the mode decision process in SVC owing to its heavy computations. The current mode in SVC is selected by the highest conditional probability of SVC¡¦s mode given the H.264/AVC¡¦s mode. Exactly when an error prediction occurs is then detected using Bayesian theorem, followed by its refinement using the Markov model. Experimental results indicate that the proposed algorithm saves on average 75.28% of coding time with 0.13 dB PSNR loss over that when using a cascaded pixel domain transcoder.

This investigates the voltage flicker problem of a large steel plant and presents the mitigation strategy by applying the static var compensator (SVC) and cogenerator. The fluctuation of real power and reactive power consumption by an arc furnace has been measured and recorded during the steel production process. The dynamic load model of the A/C arc furnace is derived based on the actual field data and has been included in the computer simulation by the CYME software package for load flow analysis. The block diagrams of SVC controller and the excitation system of cogenerators are considered to solve the response of reactive power compensation according to the voltage fluctuation of the control bus. To maintain the electric service reliability of arc furnace when an external utility fault occurs, the tie line tripping and load shedding is implemented to prevent the tripping of cogenerator after system disturbance. It is found that the dynamic load behavior of arc furnace in the isolated industrial power system can be well compensated by the cogenerator with adaptive control of exciter and governor to generate proper reactive power and real power according to the fluctuation of bus voltage and system frequency respectively.