Considere um sistema de comunicação em que um equipamento transmissor envia pacotes de dados, de tamanho fixo e a uma taxa uniforme, a um equipamento receptor. Considere também que esses equipamentos estejam conectados por uma rede de comutação de pacotes, que introduz um atraso aleatório a cada pacote que trafega na rede. Nesta tese, é proposto um modelo de recuperação adaptativa de relógio capaz de sincronizar as frequências e as fases desses dispositivos, dentro de certos limites especificados de precisão. Esse método para atingir sincronização de frequência e de fase é baseado em medições dos tempos de chegada dos pacotes ao receptor, que são usados para controlar a dinâmica de um phase-locked loop (PLL) digital. O desempenho desse modelo é avaliado através de simulações numéricas realizadas considerando valores de parâmetros realistas. Os resultados indicam que esse esquema tem potencial para ser usado em aplicações práticas. / Consider a communication system in which a transmitter equipment sends fixed-size packets of data at a uniform rate to a receiver equipment. Consider also that these equipments are connected by a packet-switched network, which introduces a random delay to each packet. In this thesis, we propose an adaptive clock recovery scheme capable of synchronizing the frequencies and the phases of these devices, within specified limits of precision. This scheme for achieving frequency and phase synchronization is based on measurements of the packet arrival times at the receiver, which are used to control the dynamics of a digital phase-locked loop (PLL). The scheme performance is evaluated via numerical simulations performed by using realistic parameter values. The results suggest that this scheme has potential to be used in practical applications.

Para poder satisfacer la demanda de mayores anchos de banda y los requisitos de los nuevos servicios, se espera que se produzca una evolución de las redes ópticas hacia arquitecturas reconfigurables dinámicamente. Esta evolución subraya la importancia de ofrecer soluciones en la que la escalabilidad y la flexibilidad sean las principales directrices. De acuerdo a estas características, las redes ópticas de conmutación de paquetes (OPS) proporcionan altas capacidades de transmisión, eficiencia en ancho de banda y excelente flexibilidad, además de permitir el procesado de los paquetes directamente en la capa óptica. En este escenario, la solución all-optical label switching (AOLS) resuelve el cuello de botella impuesto por los nodos que realizan el procesado en el dominio eléctrico. A pesar de los progresos en el campo del networking óptico, las redes totalmente ópticas todavía se consideran una solución lejana . Por tanto, es importante desarrollar un escenario de migración factible y gradual desde las actuales redes ópticas basadas en la conmutación de circuitos (OCS). Uno de los objetivos de esta tesis se centra en la propuesta de escenarios de migración basados en redes híbridas que combinan diferentes tecnologías de conmutación. Además, se analiza la arquitectura de una red OPS compuesta de nodos que incorporan nuevas funcionalidades relacionadas con labores de monitorización y esquemas de recuperación. Las redes ópticas permiten mejorar la transparencia de la red, pero a costa de aumentar la complejidad de las tareas de gesión. En este escenario, la monitorización óptica de prestaciones (OPM) surge como una tecnología capaz de facilitar la administración de las redes OPS, en las que cada paquete sigue su propia ruta en la red y sufre un diferente nivel de degradación al llegar a su destino. Aquí reside la importancia de OPM para garantizar los requisitos de calidad de cada paquete. / Vilar Mateo, R. (2010). Optical performance monitoring in optical packet-switched networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8926 / Palancia

The goal of this thesis was to design two complex scenarios with focus on different kinds of transmission in packet-switched networks. First scenario is about ARQ (Automatic Repeat Request) protocols. It consists of introduction to Stop-and-Wait, Go Back N and Selective Repeat protocols and their comparison. Second scenario compares unicast, multicast, broadcast and anycast transmission methods. Both scenarios use applications which can simulate particular methods or protocols. These applications along with virtual environments are used for demonstration of characteristics of these methods/protocols.

<p>Network on Chip is a scalable and flexible communication infrastructure for the design of core based System on Chip. Communication performance of a NoC depends heavily on the routing algorithm. Deterministic and adaptive distributed routing algorithms have been advocated in all the current NoC architectural proposals. In this thesis we make a case for the use of source routing for NoCs, especially for regular topologies like mesh. The advantages of source routing include in-order packet delivery; faster and simpler router design; and possibility of mixing non-minimal paths in a mainly minimal routing. We propose a method to compute paths for various communications in such a way that traffic congestion is avoided while ensuring deadlock free routing. We also propose an efficient scheme to encode the paths.</p><p>We developed a tool in Matlab that computes paths for source routing for both general and application specific communications. Depending upon the type of traffic, this tool computes paths for source routing by selecting best routing algorithm out of many routing algorithms. The tool uses a constructive path improvement algorithm to compute paths that give more uniform link load distribution. It also generates different types of traffics. We also developed a simulator capable of simulating source routing for mesh topology NoC. The experiments and simulations which we performed were successful and the results show that the advantages of source routing especially lower packet latency more than compensate its disadvantages. The results also demonstrate that source routing can be a good routing candidate for practical core based SoCs design using network on chip communication infrastructure.</p>

The telecommunication market is growing at a very fast pace with the evolution of new technologies to support high speed throughput and the availability of a wide range of services and applications in the mobile networks. This has led to a need for communication service providers (CSPs) to shift their focus from network elements monitoring towards services monitoring and subscribers’ satisfaction by introducing the service quality management (SQM) and the customer experience management (CEM) that require fast responses to reduce the time to find and solve network problems, to ensure efficiency and proactive maintenance, to improve the quality of service (QoS) and the quality of experience (QoE) of the subscribers. While both the SQM and the CEM demand multiple information from different interfaces, managing multiple data sources adds an extra layer of complexity with the collection of data. While several studies and researches have been conducted for data analytics in mobile networks, most of them did not consider analytics based on the four dimensions involved in the mobile networks environment which are the subscriber, the handset, the service and the network element with multiple interface correlation. The main objective of this research was to develop mobile network analytics models applied to the 3G packet-switched domain by analysing data from the radio network with the Iub interface and the core network with the Gn interface to provide a fast root cause analysis (RCA) approach considering the four dimensions involved in the mobile networks. This was achieved by using the latest computer engineering advancements which are Big Data platforms and data mining techniques through machine learning algorithms. / Electrical and Mining Engineering / M. Tech. (Electrical Engineering)

<p>This dissertation considers packet-switched wireless networks for transmission of variable-rate layered hybrid video streams. Target applications are video streaming and broadcasting services. The work can be divided into two main parts.</p><p>In the first part, a novel quality-scalable scheme based on coefficient refinement and encoder quality constraints is developed as a possible extension to the video coding standard H.264. After a technical introduction to the coding tools of H.264 with the main focus on error resilience features, various quality scalability schemes in previous research are reviewed. Based on this discussion, an encoder decoder framework is designed for an arbitrary number of quality layers, hereby also enabling region-of-interest coding. After that, the performance of the new system is exhaustively tested, showing that the bit rate increase typically encountered with scalable hybrid coding schemes is, for certain coding parameters, only small to moderate. The double- and triple-layer constellations of the framework are shown to perform superior to other systems.</p><p>The second part considers layered code streams as generated by the scheme of the first part. Various error propagation issues in hybrid streams are discussed, which leads to the definition of a decoder quality constraint and a segmentation of the code stream to transmit. A packetization scheme based on successive source rate consumption is drafted, followed by the formulation of the channel code rate optimization problem for an optimum assignment of available codes to the channel packets. Proper MSE-based error metrics are derived, incorporating the properties of the source signal, a terminate-on-error decoding strategy, error concealment, inter-packet dependencies, and the channel conditions. The Viterbi algorithm is presented as a low-complexity solution to the optimization problem, showing a great adaptivity of the joint source channel coding scheme to the channel conditions. An almost constant image qualiity is achieved, also in mismatch situations, while the overall channel code rate decreases only as little as necessary as the channel quality deteriorates. It is further shown that the variance of code distributions is only small, and that the codes are assigned irregularly to all channel packets.</p><p>A double-layer constellation of the framework clearly outperforms other schemes with a substantial margin. </p><p>Keywords — Digital lossy video compression, visual communication, variable bit rate (VBR), SNR scalability, layered image processing, quality layer, hybrid code stream, predictive coding, progressive bit stream, joint source channel coding, fidelity constraint, channel error robustness, resilience, concealment, packet-switched, mobile and wireless ATM, noisy transmission, packet loss, binary symmetric channel, streaming, broadcasting, satellite and radio links, H.264, MPEG-4 AVC, Viterbi, trellis, unequal error protection</p>

This dissertation considers packet-switched wireless networks for transmission of variable-rate layered hybrid video streams. Target applications are video streaming and broadcasting services. The work can be divided into two main parts. In the first part, a novel quality-scalable scheme based on coefficient refinement and encoder quality constraints is developed as a possible extension to the video coding standard H.264. After a technical introduction to the coding tools of H.264 with the main focus on error resilience features, various quality scalability schemes in previous research are reviewed. Based on this discussion, an encoder decoder framework is designed for an arbitrary number of quality layers, hereby also enabling region-of-interest coding. After that, the performance of the new system is exhaustively tested, showing that the bit rate increase typically encountered with scalable hybrid coding schemes is, for certain coding parameters, only small to moderate. The double- and triple-layer constellations of the framework are shown to perform superior to other systems. The second part considers layered code streams as generated by the scheme of the first part. Various error propagation issues in hybrid streams are discussed, which leads to the definition of a decoder quality constraint and a segmentation of the code stream to transmit. A packetization scheme based on successive source rate consumption is drafted, followed by the formulation of the channel code rate optimization problem for an optimum assignment of available codes to the channel packets. Proper MSE-based error metrics are derived, incorporating the properties of the source signal, a terminate-on-error decoding strategy, error concealment, inter-packet dependencies, and the channel conditions. The Viterbi algorithm is presented as a low-complexity solution to the optimization problem, showing a great adaptivity of the joint source channel coding scheme to the channel conditions. An almost constant image qualiity is achieved, also in mismatch situations, while the overall channel code rate decreases only as little as necessary as the channel quality deteriorates. It is further shown that the variance of code distributions is only small, and that the codes are assigned irregularly to all channel packets. A double-layer constellation of the framework clearly outperforms other schemes with a substantial margin. Keywords — Digital lossy video compression, visual communication, variable bit rate (VBR), SNR scalability, layered image processing, quality layer, hybrid code stream, predictive coding, progressive bit stream, joint source channel coding, fidelity constraint, channel error robustness, resilience, concealment, packet-switched, mobile and wireless ATM, noisy transmission, packet loss, binary symmetric channel, streaming, broadcasting, satellite and radio links, H.264, MPEG-4 AVC, Viterbi, trellis, unequal error protection

Network on Chip is a scalable and flexible communication infrastructure for the design of core based System on Chip. Communication performance of a NoC depends heavily on the routing algorithm. Deterministic and adaptive distributed routing algorithms have been advocated in all the current NoC architectural proposals. In this thesis we make a case for the use of source routing for NoCs, especially for regular topologies like mesh. The advantages of source routing include in-order packet delivery; faster and simpler router design; and possibility of mixing non-minimal paths in a mainly minimal routing. We propose a method to compute paths for various communications in such a way that traffic congestion is avoided while ensuring deadlock free routing. We also propose an efficient scheme to encode the paths. We developed a tool in Matlab that computes paths for source routing for both general and application specific communications. Depending upon the type of traffic, this tool computes paths for source routing by selecting best routing algorithm out of many routing algorithms. The tool uses a constructive path improvement algorithm to compute paths that give more uniform link load distribution. It also generates different types of traffics. We also developed a simulator capable of simulating source routing for mesh topology NoC. The experiments and simulations which we performed were successful and the results show that the advantages of source routing especially lower packet latency more than compensate its disadvantages. The results also demonstrate that source routing can be a good routing candidate for practical core based SoCs design using network on chip communication infrastructure.