QoS em WIMAX – Análise e avaliação de módulos para simulação com o ns-2

Mestrado em Engenharia Electrotécnica e de Computadores

Geração de simuladores de filas para diferentes contextos com estudo de casos para redes de computadores

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ethernet-based systems: contributions to the holistic analysis

A number of characteristics are boosting the eagerness of extending Ethernet to also cover factory-floor distributed real-time applications. Full-duplex links, non-blocking and priority-based switching, bandwidth availability, just to mention a few, are characteristics upon which that eagerness is building up. But, will Ethernet technologies really manage to replace traditional Fieldbus networks? To this question, Fieldbus fundamentalists often argue that the two technologies are not comparable. In fact, Ethernet technology, by itself, does not include features above the lower layers of the OSI communication model. Where are the higher layers that permit building real industrial applications? And, taking for free that they are available, what is the impact of those protocols, mechanisms and application models on the overall performance of Ethernetbased distributed factory-floor applications? In this paper we provide some contributions that may pave the way towards providing some reasonable answers to these issues.

From simulation to statistical analysis: timeliness assessment of ethernet/IP-based distributed systems

A number of characteristics are boosting the eagerness of extending Ethernet to also cover factory-floor distributed real-time applications. Full-duplex links, non-blocking and priority-based switching, bandwidth availability, just to mention a few, are characteristics upon which that eagerness is building up. But, will Ethernet technologies really manage to replace traditional Fieldbus networks? Ethernet technology, by itself, does not include features above the lower layers of the OSI communication model. In the past few years, it is particularly significant the considerable amount of work that has been devoted to the timing analysis of Ethernet-based technologies. It happens, however, that the majority of those works are restricted to the analysis of sub-sets of the overall computing and communication system, thus without addressing timeliness at a holistic level. To this end, we are addressing a few inter-linked research topics with the purpose of setting a framework for the development of tools suitable to extract temporal properties of Commercial-Off-The-Shelf (COTS) Ethernet-based factory-floor distributed systems. This framework is being applied to a specific COTS technology, Ethernet/IP. In this paper, we reason about the modelling and simulation of Ethernet/IP-based systems, and on the use of statistical analysis techniques to provide usable results. Discrete event simulation models of a distributed system can be a powerful tool for the timeliness evaluation of the overall system, but particular care must be taken with the results provided by traditional statistical analysis techniques.

Real-time fieldbus communications using Profibus networks

This paper provides a comprehensive study on how to use Profibus fieldbus networks to support real-time industrial communications, that is, on how to ensure the transmission of real-time messages within a maximum bound time. Profibus is base on a simplified timed token (TT) protocol, which is a well-proved solution for real-time communication systems. However, Profibus differs with respect to the TT protocol, thus preventing the application of the usual TT protocol real-time analysis. In fact, real-time solutions for networks based on the TT protocol rely on the possibility of allocating specific bandwidth for the real-time traffic. This means that a minimum amount of time is always available, at each token visit, to transmit real-time messages, transversely, with the Profibus protocol, in the worst case, only one real-time message is processed per token visit. The authors propose two approaches to guarantee the real-time behavior of the Profibus protocol: (1) an unconstrained low-priority traffic profile; and (2) a constrained low-priority traffic profile. The proposed analysis shows that the first profile is a suitable approach for more responsive systems (tighter deadlines), while the second allows for increased nonreal-time traffic throughput

Wind energy technology

Electricity is regarded as one of the indispensable means to growth of any country’s economy. This source of power is the heartbeat of everything from the huge metropolitans, industries, worldwide computer networks and our global communication systems down to our homes. Electrical energy is the lifeline for any economic and societal development of a region or country. It is central to develop countries for maintaining acquired life styles and essential to developing countries for industrialisation and escaping poverty.

Developing persuasive interfaces

MSCC Dissertation in Computer Engineering

Sistema Multi-Agente de prestação de serviços de seguimento adaptados aos requisitos do utilizador

Mestrado em Engenharia Electrotécnica e de Computadores - Área de Especialização de Telecomunicações

Gestão de Redes Baseada em Agentes Móveis

A gestão das redes informáticas converteu-se num fator vital para as redes operarem de forma eficiente, produtiva e lucrativa. A gestão envolve a monitorização e o controlo dos sistemas para que estes funcionem como o pretendido. Ações de configuração, monitorização e reconfiguração dos componentes, são essenciais para melhorar o desempenho, diminuir o tempo de inatividade, melhor a segurança e efetuar contabilização. A maioria das aplicações de gestão de Redes assenta no paradigma centralizado cliente-servidor, onde um servidor central coleta e analisa dados provenientes dos diferentes elementos dispersos pela rede. Esses dados de gestão estão armazenados em bases de dados de gestão localizadas nos diversos elementos da rede. No entanto, este paradigma não tem conseguido dar resposta às exigências das redes atuais. Surge assim a necessidade de utilizar novos paradigmas para a gestão das redes. Uma alternativa baseada no paradigma dos agentes móveis já foi estudada, proposta e desenvolvida para a gestão da rede do GECAD-ISEP. Neste trabalho pretende-se propor e adicionar novas capacidades aos agentes móveis existentes, assim como novos agentes. Com vista à validação da solução proposta recorre-se à utilização de um simulador de redes.

A framework for using real data with distributed low cost sensors

Currently, due to the widespread use of computers and the internet, students are trading libraries for the World Wide Web and laboratories with simulation programs. In most courses, simulators are made available to students and can be used to proof theoretical results or to test a developing hardware/product. Although this is an interesting solution: low cost, easy and fast way to perform some courses work, it has indeed major disadvantages. As everything is currently being done with/in a computer, the students are loosing the “feel” of the real values of the magnitudes. For instance in engineering studies, and mainly in the first years, students need to learn electronics, algorithmic, mathematics and physics. All of these areas can use numerical analysis software, simulation software or spreadsheets and in the majority of the cases data used is either simulated or random numbers, but real data could be used instead. For example, if a course uses numerical analysis software and needs a dataset, the students can learn to manipulate arrays. Also, when using the spreadsheets to build graphics, instead of using a random table, students could use a real dataset based, for instance, in the room temperature and its variation across the day. In this work we present a framework which uses a simple interface allowing it to be used by different courses where the computers are the teaching/learning process in order to give a more realistic feeling to students by using real data. A framework is proposed based on a set of low cost sensors for different physical magnitudes, e.g. temperature, light, wind speed, which are connected to a central server, that the students have access with an Ethernet protocol or are connected directly to the student computer/laptop. These sensors use the communication ports available such as: serial ports, parallel ports, Ethernet or Universal Serial Bus (USB). Since a central server is used, the students are encouraged to use sensor values results in their different courses and consequently in different types of software such as: numerical analysis tools, spreadsheets or simply inside any programming language when a dataset is needed. In order to do this, small pieces of hardware were developed containing at least one sensor using different types of computer communication. As long as the sensors are attached in a server connected to the internet, these tools can also be shared between different schools. This allows sensors that aren't available in a determined school to be used by getting the values from other places that are sharing them. Another remark is that students in the more advanced years and (theoretically) more know how, can use the courses that have some affinities with electronic development to build new sensor pieces and expand the framework further. The final solution provided is very interesting, low cost, simple to develop, allowing flexibility of resources by using the same materials in several courses bringing real world data into the students computer works.

Old cellulose for new multifunctional networks

Dissertação para obtenção do Grau de Doutor em Ciência e Engenharia de Materiais

"Virar a Sala de Aula”: centrar a aprendizagem no aluno recorrendo a ferramentas cognitivas

Relatório de projeto de mestrado em Ensino de Informática

Model-based diagnosis system: application to constructed wetlands

Report for the scientific sojourn carried out at the Model-based Systems and Qualitative Reasoning Group (Technical University of Munich), from September until December 2005. Constructed wetlands (CWs), or modified natural wetlands, are used all over the world as wastewater treatment systems for small communities because they can provide high treatment efficiency with low energy consumption and low construction, operation and maintenance costs. Their treatment process is very complex because it includes physical, chemical and biological mechanisms like microorganism oxidation, microorganism reduction, filtration, sedimentation and chemical precipitation. Besides, these processes can be influenced by different factors. In order to guarantee the performance of CWs, an operation and maintenance program must be defined for each Wastewater Treatment Plant (WWTP). The main objective of this project is to provide a computer support to the definition of the most appropriate operation and maintenance protocols to guarantee the correct performance of CWs. To reach them, the definition of models which represent the knowledge about CW has been proposed: components involved in the sanitation process, relation among these units and processes to remove pollutants. Horizontal Subsurface Flow CWs are chosen as a case study and the filtration process is selected as first modelling-process application. However, the goal is to represent the process knowledge in such a way that it can be reused for other types of WWTP.

Desenvolupament d'una aplicació Android per a Moodle

L'evolució que la tecnologia de les comunicacions sense fils ha experimentat en els darrers anys permet que avui en dia els dispositius mòbils proporcionin una resposta més que acceptable. Ja s'han superat molts dels problemes de mobilitat, d'infraestructura i d'ample de banda que fins ara dificultaven l'ús d'aquests dispositius. Aquest fet ha fomentat l'expansió de diferents sistemes dels que es pot destacar Android, iPhone OS i Windows Mobile/Windows Phone 7. Els dos primers són els que actualment es disputen el lideratge del mercat dels dispositius i aplicacions mòbils i és Android el que ha experimentat el major creixement els darrers anys. Paral·lelament, la constant introducció de programari d'e-learning destinat a activitats de formació no presencial basades en Internet ha permès arribar a milions d'usuaris en diferents àmbits, com ara universitats, empreses i institucions d'arreu del món. D'aquest conjunt de programari destaca Moodle, suite de codi obert que permet crear llocs web de formació en línia de forma senzilla i eficaç.Aquest Projecte de Final de Carrera, emmarcat en l'àrea de Xarxes de Computadors, conjugaaquests tres conceptes mitjançant el desenvolupament d'una aplicació per a dispositius mòbils Android que connecta a un servidor Moodle. La comunicació entre ells utilitza intensivament les xarxes sense fils i fa crides als serveis que aquest ofereix gràcies als Web Services, mètode de comunicacions composat d'un conjunt de protocols i de programari que permet la comunicació entre dos dispositius a través de la xarxa.