Study and simulation of low rate video coding schemes

The semiannual report is included. Topics covered include communication, information science, data compression, remote sensing, color mapped images, robust coding scheme for packet video, recursively indexed differential pulse code modulation, image compression technique for use on token ring networks, and joint source/channel coder design

Methods of Congestion Control for Adaptive Continuous Media

Since the first exchange of data between machines in different locations in early 1960s, computer networks have grown exponentially with millions of people now using the Internet. With this, there has also been a rapid increase in different kinds of services offered over the World Wide Web from simple e-mails to streaming video. It is generally accepted that the commonly used protocol suite TCP/IP alone is not adequate for a number of modern applications with high bandwidth and minimal delay requirements. Many technologies are emerging such as IPv6, Diffserv, Intserv etc, which aim to replace the onesize-fits-all approach of the current lPv4. There is a consensus that the networks will have to be capable of multi-service and will have to isolate different classes of traffic through bandwidth partitioning such that, for example, low priority best-effort traffic does not cause delay for high priority video traffic. However, this research identifies that even within a class there may be delays or losses due to congestion and the problem will require different solutions in different classes. The focus of this research is on the requirements of the adaptive continuous media class. These are traffic flows that require a good Quality of Service but are also able to adapt to the network conditions by accepting some degradation in quality. It is potentially the most flexible traffic class and therefore, one of the most useful types for an increasing number of applications. This thesis discusses the QoS requirements of adaptive continuous media and identifies an ideal feedback based control system that would be suitable for this class. A number of current methods of congestion control have been investigated and two methods that have been shown to be successful with data traffic have been evaluated to ascertain if they could be adapted for adaptive continuous media. A novel method of control based on percentile monitoring of the queue occupancy is then proposed and developed. Simulation results demonstrate that the percentile monitoring based method is more appropriate to this type of flow. The problem of congestion control at aggregating nodes of the network hierarchy, where thousands of adaptive flows may be aggregated to a single flow, is then considered. A unique method of pricing mean and variance is developed such that each individual flow is charged fairly for its contribution to the congestion

Simulation and analytical performance studies of generic atm switch fabrics.

As technology improves exciting new services such as video phone become possible and economically viable but their deployment is hampered by the inability of the present networks to carry them. The long term vision is to have a single network able to carry all present and future services. Asynchronous Transfer Mode, ATM, is the versatile new packet -based switching and multiplexing technique proposed for the single network. Interest in ATM is currently high as both industrial and academic institutions strive to understand more about the technique. Using both simulation and analysis, this research has investigated how the performance of ATM switches is affected by architectural variations in the switch fabric design and how the stochastic nature of ATM affects the timing of constant bit rate services. As a result the research has contributed new ATM switch performance data, a general purpose ATM switch simulator and analytic models that further research may utilise and has uncovered a significant timing problem of the ATM technique. The thesis will also be of interest and assistance to anyone planning on using simulation as a research tool to model an ATM switch

A review of connection admission control algorithms for ATM networks

The emergence of high-speed networks such as those with ATM integrates large numbers of services with a wide range of characteristics. Admission control is a prime instrument for controlling congestion in the network. As part of connection services to an ATM system, the Connection Admission Control (CAC) algorithm decides if another call or connection can be admitted to the Broadband Network. The main task of the CAC is to ensure that the broadband resources will not saturate or overflow within a very small probability. It limits the connections and guarantees Quality of Service for the new connection. The algorithm for connection admission is crucial in determining bandwidth utilisation efficiency. With statistical multiplexing more calls can be allocated on a network link, while still maintaining the Quality of Service specified by the connection with traffic parameters and type of service. A number of algorithms for admission control for Broadband Services with ATM Networks are described and compared for performance under different traffic loads. There is a general description of the ATM Network as an introduction. Issues to do with source distributions and traffic models are explored in Chapter 2. Chapter 3 provides an extensive presentation of the CAC algorithms for ATM Broadband Networks. The ideas about the Effective Bandwidth are reviewed in Chapter 4, and a different approach to admission control using online measurement is presented in Chapter 5. Chapter 6 has the numerical evaluation of four of the key algorithms, with simulations. Finally Chapter 7 has conclusions of the findings and explores some possibilities for further work

Performance Improvements for FDDI and CSMA/CD Protocols

The High-Performance Computing Initiative from the White House Office of Science and Technology Policy has defined 20 major challenges in science and engineering which are dependent on the solutions to a number of high-performance computing problems. One of the major areas of focus of this initiative is the development of gigabit rate networks to be used in environments such as the space station or a National Research and Educational Network (NREN). The strategy here is to use existing network designs as building blocks for achieving higher rates, with the ultimate goal being a gigabit rate network. Two strategies which contribute to achieving this goal are examined in detail.1 FDDI2 is a token ring network based on fiber optics capable of a 100 Mbps rate. Both media access (MAC) and physical layer modifications are considered. A method is presented which allows one to determine maximum utilization based on the token-holding timer settings. Simulation results show that employing the second counter-rotating ring in combination with destination removal has a multiplicative effect greater than the effect which either of the factors have individually on performance. Two 100 Mbps rings can handle loads in the range of 400 to 500 Mbps for traffic with a uniform distribution and fixed packet size. Performance is dependent on the number of nodes, improving as the number increases. A wide range of environments are examined to illustrate robustness, and a method of implementation is discussed

Real-time communications over switched Ethernet supporting dynamic QoS management

Doutoramento em Engenharia InformáticaDurante a última década temos assistido a um crescente aumento na utilização de sistemas embutidos para suporte ao controlo de processos, de sistemas robóticos, de sistemas de transportes e veículos e até de sistemas domóticos e eletrodomésticos. Muitas destas aplicações são críticas em termos de segurança de pessoas e bens e requerem um alto nível de determinismo com respeito aos instantes de execução das respectivas tarefas. Além disso, a implantação destes sistemas pode estar sujeita a limitações estruturais, exigindo ou beneficiando de uma configuração distribuída, com vários subsistemas computacionais espacialmente separados. Estes subsistemas, apesar de espacialmente separados, são cooperativos e dependem de uma infraestrutura de comunicação para atingir os objectivos da aplicação e, por consequência, também as transacções efectuadas nesta infraestrutura estão sujeitas às restrições temporais definidas pela aplicação. As aplicações que executam nestes sistemas distribuídos, chamados networked embedded systems (NES), podem ser altamente complexas e heterogéneas, envolvendo diferentes tipos de interacções com diferentes requisitos e propriedades. Um exemplo desta heterogeneidade é o modelo de activação da comunicação entre os subsistemas que pode ser desencadeada periodicamente de acordo com uma base de tempo global (time-triggered), como sejam os fluxos de sistemas de controlo distribuído, ou ainda ser desencadeada como consequência de eventos assíncronos da aplicação (event-triggered). Independentemente das características do tráfego ou do seu modelo de activação, é de extrema importância que a plataforma de comunicações disponibilize as garantias de cumprimento dos requisitos da aplicação ao mesmo tempo que proporciona uma integração simples dos vários tipos de tráfego. Uma outra propriedade que está a emergir e a ganhar importância no seio dos NES é a flexibilidade. Esta propiedade é realçada pela necessidade de reduzir os custos de instalação, manutenção e operação dos sistemas. Neste sentido, o sistema é dotado da capacidade para adaptar o serviço fornecido à aplicação aos respectivos requisitos instantâneos, acompanhando a evolução do sistema e proporcionando uma melhor e mais racional utilização dos recursos disponíveis. No entanto, maior flexibilidade operacional é igualmente sinónimo de maior complexidade derivada da necessidade de efectuar a alocação dinâmica dos recursos, acabando também por consumir recursos adicionais no sistema. A possibilidade de modificar dinâmicamente as caracteristicas do sistema também acarreta uma maior complexidade na fase de desenho e especificação. O aumento do número de graus de liberdade suportados faz aumentar o espaço de estados do sistema, dificultando a uma pre-análise. No sentido de conter o aumento de complexidade são necessários modelos que representem a dinâmica do sistema e proporcionem uma gestão optimizada e justa dos recursos com base em parâmetros de qualidade de serviço (QdS). É nossa tese que as propriedades de flexibilidade, pontualidade e gestão dinâmica de QdS podem ser integradas numa rede switched Ethernet (SE), tirando partido do baixo custo, alta largura de banda e fácil implantação. Nesta dissertação é proposto um protocolo, Flexible Time-Triggered communication over Switched Ethernet (FTT-SE), que suporta as propriedades desejadas e que ultrapassa as limitações das redes SE para aplicações de tempo-real tais como a utilização de filas FIFO, a existência de poucos níveis de prioridade e a pouca capacidade de gestão individualizada dos fluxos. O protocolo baseia-se no paradigma FTT, que genericamente define a arquitectura de uma pilha protocolar sobre o acesso ao meio de uma rede partilhada, impondo desta forma determinismo temporal, juntamente com a capacidade para reconfiguração e adaptação dinâmica da rede. São ainda apresentados vários modelos de distribuição da largura de banda da rede de acordo com o nível de QdS especificado por cada serviço utilizador da rede. Esta dissertação expõe a motivação para a criação do protocolo FTT-SE, apresenta uma descrição do mesmo, bem como a análise de algumas das suas propiedades mais relevantes. São ainda apresentados e comparados modelos de distribuição da QdS. Finalmente, são apresentados dois casos de aplicações que sustentam a validade da tese acima mencionada.During the last decade we have witnessed a massive deployment of embedded systems on a wide applications range, from industrial automation to process control, avionics, cars or even robotics. Many of these applications have an inherently high level of criticality, having to perform tasks within tight temporal constraints. Additionally, the configuration of such systems is often distributed, with several computing nodes that rely on a communication infrastructure to cooperate and achieve the application global goals. Therefore, the communications are also subject to the same temporal constraints set by the application requirements. Many applications relying on such networked embedded systems (NES) are complex and heterogeneous, comprehending different activities with different requirements and properties. For example, the communication between subsystems may follow a strict temporal synchronization with respect to a global time-base (time-triggered), like in a distributed feedback control loop, or it may be issued asynchronously upon the occurrence of events (eventtriggered). Regardless of the traffic characteristics and its activation model, it is of paramount importance having a communication framework that provides seamless integration of heterogeneous traffic sources while guaranteeing the application requirements. Another property that has been emerging as important for NES design and operation is flexibility. The need to reduce installation and operational costs, while facilitating maintenance is promoting a more rational use of the available resources at run-time, exploring the ability to tune service parameters as the system evolves. However, such operational flexibility comes with the cost of increasing the complexity of the system to handle the dynamic resource management, which on the other hand demands the allocation of additional system resources. Moreover, the capacity to dynamically modify the system properties also causes a higher complexity when designing and specifying the system, since the operational state-space increases with the degrees of flexibility of the system. Therefore, in order to bound this complexity appropriate operational models are needed to handle the system dynamics and carry on an efficient and fair resource management strategy based on quality of service (QoS) metrics. This thesis states that the properties of flexibility and timeliness as needed for dynamic QoS management can be provided to switched Ethernet based systems. Switched Ethernet, although initially designed for general purpose Internet access and file transfers, is becoming widely used in NES-based applications. However, COTS switched Ethernet is insufficient regarding the needs for real-time predictability and for supporting the aforementioned properties due the use of FIFO queues too few priority levels and for stream-level management capabilities. In this dissertation we propose a protocol to overcome those limitations, namely the Flexible Time-Triggered communication over Switched Ethernet (FTT-SE). The protocol is based on the FTT paradigm that generically defines a protocol architecture suitable to enforce real-time determinism on a communication network supporting the desired flexibility properties. This dissertation addresses the motivation for FTT-SE, describing the protocol as well as its schedulability analysis. It additionally covers the resource distribution topic, where several distribution models are proposed to manage the resource capacity among the competing services and while considering the QoS level requirements of each service. A couple of application cases are shown that support the aforementioned thesis

Satellite Networks: Architectures, Applications, and Technologies

Since global satellite networks are moving to the forefront in enhancing the national and global information infrastructures due to communication satellites' unique networking characteristics, a workshop was organized to assess the progress made to date and chart the future. This workshop provided the forum to assess the current state-of-the-art, identify key issues, and highlight the emerging trends in the next-generation architectures, data protocol development, communication interoperability, and applications. Presentations on overview, state-of-the-art in research, development, deployment and applications and future trends on satellite networks are assembled

Cellular, Wide-Area, and Non-Terrestrial IoT: A Survey on 5G Advances and the Road Towards 6G

The next wave of wireless technologies is proliferating in connecting things among themselves as well as to humans. In the era of the Internet of things (IoT), billions of sensors, machines, vehicles, drones, and robots will be connected, making the world around us smarter. The IoT will encompass devices that must wirelessly communicate a diverse set of data gathered from the environment for myriad new applications. The ultimate goal is to extract insights from this data and develop solutions that improve quality of life and generate new revenue. Providing large-scale, long-lasting, reliable, and near real-time connectivity is the major challenge in enabling a smart connected world. This paper provides a comprehensive survey on existing and emerging communication solutions for serving IoT applications in the context of cellular, wide-area, as well as non-terrestrial networks. Specifically, wireless technology enhancements for providing IoT access in fifth-generation (5G) and beyond cellular networks, and communication networks over the unlicensed spectrum are presented. Aligned with the main key performance indicators of 5G and beyond 5G networks, we investigate solutions and standards that enable energy efficiency, reliability, low latency, and scalability (connection density) of current and future IoT networks. The solutions include grant-free access and channel coding for short-packet communications, non-orthogonal multiple access, and on-device intelligence. Further, a vision of new paradigm shifts in communication networks in the 2030s is provided, and the integration of the associated new technologies like artificial intelligence, non-terrestrial networks, and new spectra is elaborated. Finally, future research directions toward beyond 5G IoT networks are pointed out.Comment: Submitted for review to IEEE CS&

Moving In Time: Neurons, Clocks, and Rhythmic Movements

Beek, P.J. [Promotor]Daffertshofer, A. [Copromotor