Opportunistic packet scheduling in body area networks

Significant research efforts are being devoted to Body Area Networks (BAN) due to their potential for revolutionizing healthcare practices. Energy-efficiency and communication reliability are critically important for these networks. In an experimental study with three different mote platforms, we show that changes in human body shadowing as well as those in the relative distance and orientation of nodes caused by the common human body movements can result in significant fluctuations in the received signal strength within a BAN. Furthermore, regular movements, such as walking, typically manifest in approximately periodic variations in signal strength. We present an algorithm that predicts the signal strength peaks and evaluate it on real-world data. We present the design of an opportunistic MAC protocol, named BANMAC, that takes advantage of the periodic fluctuations of the signal strength to achieve high reliability even with low transmission power.

A framework for offloading real-time applications in a distributed environment

This work focuses on highly dynamic distributed systems with Quality of Service (QoS) constraints (most importantly real-time constraints). To that purpose, real-time applications may benefit from code offloading techniques, so that parts of the application can be offloaded and executed, as services, by neighbour nodes, which are willing to cooperate in such computations. These applications explicitly state their QoS requirements, which are translated into resource requirements, in order to evaluate the feasibility of accepting other applications in the system.

POSIX trace based behavioural reflection

Traditional Real-Time Operating Systems (RTOS) are not designed to accommodate application specific requirements. They address a general case and the application must co-exist with any limitations imposed by such design. For modern real-time applications this limits the quality of services offered to the end-user. Research in this field has shown that it is possible to develop dynamic systems where adaptation is the key for success. However, adaptation requires full knowledge of the system state. To overcome this we propose a framework to gather data, and interact with the operating system, extending the traditional POSIX trace model with a partial reflective model. Such combination still preserves the trace mechanism semantics while creating a powerful platform to develop new dynamic systems, with little impact in the system and avoiding complex changes in the kernel source code.

Fixed point transformations in the adaptive control of fractional-order MIMO systems

Though the formal mathematical idea of introducing noninteger order derivatives can be traced from the 17th century in a letter by L’Hospital in which he asked Leibniz what the meaning of D n y if n = 1/2 would be in 1695 [1], it was better outlined only in the 19th century [2, 3, 4]. Due to the lack of clear physical interpretation their first applications in physics appeared only later, in the 20th century, in connection with visco-elastic phenomena [5, 6]. The topic later obtained quite general attention [7, 8, 9], and also found new applications in material science [10], analysis of earth-quake signals [11], control of robots [12], and in the description of diffusion [13], etc.

Collaborative learning in a qeb-accessible workbench

Web-based course management and delivery is regarded by many institutions as a key factor in an increasingly competitive education and training world, but the systems currently available are largely unsatisfactory in terms of supporting collaborative work and access to practical science facilities. These limitations are less important in areas where “pen-and-paper” courseware is the mainstream, but become unacceptably restrictive when student assignments require real-time teamwork and access to laboratory equipment. This paper presents a web-accessible workbench for electronics design and test, which was developed in the scope of an European IST project entitled PEARL, with the aim of supporting two main features: full web access and collaborative learning facilities.

On-line defragmentation for run-time partially reconfigurable FPGAs

Dynamically reconfigurable systems have benefited from a new class of FPGAs recently introduced into the market, which allow partial and dynamic reconfiguration at run-time, enabling multiple independent functions from different applications to share the same device, swapping resources as needed. When the sequence of tasks to be performed is not predictable, resource allocation decisions have to be made on-line, fragmenting the FPGA logic space. A rearrangement may be necessary to get enough contiguous space to efficiently implement incoming functions, to avoid spreading their components and, as a result, degrading their performance. This paper presents a novel active replication mechanism for configurable logic blocks (CLBs), able to implement on-line rearrangements, defragmenting the available FPGA resources without disturbing those functions that are currently running.

A new approach to assess defragmentation strategies in dynamically reconfigurable FPGAs

Fragmentation on dynamically reconfigurable FPGAs is a major obstacle to the efficient management of the logic space in reconfigurable systems. When resource allocation decisions have to be made at run-time a rearrangement may be necessary to release enough contiguous resources to implement incoming functions. The feasibility of run-time relocation depends on the processing time required to set up rearrangements. Moreover, the performance of the relocated functions should not be affected by this process or otherwise the whole system performance, and even its operation, may be at risk. Relocation should take into account not only specific functional issues, but also the FPGA architecture, since these two aspects are normally intertwined. A simple and fast method to assess performance degradation of a function during relocation and to speed up the defragmentation process, based on previous function labelling and on the application of the Euclidian distance concept, is proposed in this paper.

Personalized public transportation information

Thesis to obtain the Master of Science Degree in Computer Science and Engineering

Low-cost vibration sensors: tendencies and applications in condition monitoring of machines and structures

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

Argumentation as Distributed Belief Revision: Conflict Resolution in Decentralised Multi-agent Systems

Decentralised co-operative multi-agent systems are computational systems where conflicts are frequent due to the nature of the represented knowledge. Negotiation methodologies, in this case argumentation based negotiation methodologies, were developed and applied to solve unforeseeable and, therefore, unavoidable conflicts. The supporting computational model is a distributed belief revision system where argumentation plays the decisive role of revision. The distributed belief revision system detects, isolates and solves, whenever possible, the identified conflicts. The detection and isolation of the conflicts is automatically performed by the distributed consistency mechanism and the resolution of the conflict, or belief revision, is achieved via argumentation. We propose and describe two argumentation protocols intended to solve different types of identified information conflicts: context dependent and context independent conflicts. While the protocol for context dependent conflicts generates new consensual alternatives, the latter chooses to adopt the soundest, strongest argument presented. The paper shows the suitability of using argumentation as a distributed decentralised belief revision protocol to solve unavoidable conflicts.

Consistency and Context Management in a Multi Agent Belief Revision Testbed

Multi-agent architectures are well suited for complex inherently distributed problem solving domains. From the many challenging aspects that arise within this framework, a crucial one emerges: how to incorporate dynamic and conflicting agent beliefs? While the belief revision activity in a single agent scenario is concentrated on incorporating new information while preserving consistency, in a multi-agent system it also has to deal with possible conflicts between the agents perspectives. To provide an adequate framework, each agent, built as a combination of an assumption based belief revision system and a cooperation layer, was enriched with additional features: a distributed search control mechanism allowing dynamic context management, and a set of different distributed consistency methodologies. As a result, a Distributed Belief Revision Testbed (DiBeRT) was developed. This paper is a preliminary report presenting some of DiBeRT contributions: a concise representation of external beliefs; a simple and innovative methodology to achieve distributed context management; and a reduced inter-agent data exchange format.

Creation and extension of ontologies for describing communications in the context of organizations

Thesis submitted to Faculdade de Ciências e Tecnologia of the Universidade Nova de Lisboa, in partial fulfillment of the requirements for the degree of Master in Computer Science

Multy-dimensional composition by objectives in aspect-oriented requirements analysis

Thesis submitted to Faculdade de Ciências e Tecnologia of Universidade Nova de Lisboa in partial fulfilment of the requirements for the degree of Master in Computer Science

Criador automático de aplicações nativas Android e iOS

Nos últimos anos tem-se verificado um acentuado aumento na utilização de dispositivos moveis a nível internacional, pelo que as aplicações desenvolvidas para este tipo específico de dispositivos, conhecidas por apps, tem vindo a ganhar uma enorme popularidade. São cada vez mais as empresas que procuram estar presentes nos mais diversos sistemas operativos móveis, com o objectivo de suportar e desenvolver o seu negócio, alargando o seu leque de possíveis consumidores. Neste sentido surgiram diversas ferramentas com a função de facilitar o desenvolvimento de aplicações móveis, denominadas frameworks multi-plataforma. Estas frameworks conduziram ao aparecimento de plataformas web, que permitem criar aplicações multi-plataforma sem ser obrigatório ter conhecimentos em programação. Assim, e a partir da análise de vários criadores online de aplicações móveis identificados e das diferentes estratégias de desenvolvimento de aplicações móveis existentes, foi proposta a implementação de uma plataforma web capaz de criar aplicações nativas Android e iOS, dois dos sistemas operativos mais utilizados na actualidade. Apos desenvolvida a plataforma web, designada MobileAppBuilder, foi avaliada a sua Qualidade e as aplicações criadas pela mesma, através do preenchimento de um questionário por parte de 10 indivíduos com formação em Engenharia Informática, resultando numa classificação geral de ”excelente”. De modo a analisar o desempenho das aplicações produzidas pela plataforma desenvolvida, foram realizados testes comparativos entre uma aplicação da MobileAppBuilder e duas homologas de dois dos criadores online estudados, nomeadamente Andromo e Como. Os resultados destes testes revelaram que a MobileAppBuilder gera aplicações menos pesadas, mais rápidas e mais eficientes em alguns aspetos, nomeadamente no arranque.