Eletrónica e Telecomunicações

Editorial

Augusto Silva — 2012-01-01

Na senda da edição anterior este número da Revista do DETI abre com um artigo de natureza biográfica sobre uma proeminente personalidade nas áreas das ciências e tecnologias: Oliver Heaviside. No cruzamento dos séculos XIX e XX são inúmeras e fundamentais as contribuições de Heaviside para as engenharias, nomeadamente aquelas que são a razão de ser do nosso Departamento. Como muito bem descreve no referido artigo o nosso colega Francisco Vaz, Heaviside é lembrado pela função que adoptou o seu nome e normalmente citado pela introdução do cálculo operacional para a resolução por métodos algébricos de equações diferenciais. É sistematicamente esquecido no que respeita à contribuição muito importante que deu à teoria do eletromagnetismo de Maxwell e à sua aplicação para explicar com rigor a transmissão de sinais eléctricos em linhas e cabos então usados em telegrafia e telefonia. Apesar de pessoalmemte controverso é certamente uma figura inspiradora na área da electrotecnia.

Heaviside, 1850-1925

Francisco Vaz — 2012-01-01

This paper presents a biography of the mathematical physicist Oliver Heaviside and brief introductions to some of his main contributions to science and technology.

A questão da incerteza tempo/frequência na Transformada de Fourier

Francisco Vaz — 2012-01-01

Assuming uncertanty for a signal as the mean square value of its energy, it is shown a simple demonstration of the relation standing for time and frequncy incertitudes. Some results for standard signals used in signal processing are also presented.

Face recognition using principal component analysis

Javier de Alfonso Miñambres — 2012-01-01

This paper discusses the application of Principal Component Analysis (PCA) in face recognition systems. PCA subspace models are commonly used to perform image dimensionreduction before the input of the classifier. More recently, PCA subspace models are estimated for one face and the comparison of models via a subspace distance allows face identification. Both strategies of applying PCA were compared for a repository of faces of famous people in uncontrolled poses.

Aplicação de técnicas de aprendizagem automática para classificação de emoções humanas com sinais de EEG

Nelson Filipe Capela — 2012-01-01

Este artigo apresenta um estudo referente a várias técnicas de Aprendizagem Automática (MachineLearning) e a sua aplicação para discriminar dois tipos de emoções humanas - valência emocional positiva e negativa, baseado em dados de eletroencefalografia (EEG).Numa primeira fase foi efetuada uma abordagem introdutória das técnicas mais típicas de Aprendizagem Automática, nomeadamente k-NearestNeighbor (K-NN), NaiveBayes, Support Vector Machine (SVM), Artificial Neural Networks (ANN), DecisionTree. Na segunda fase, as mesmas técnicas foram aplicadas para a classificação das emoções humanas com sinais de EEG.

Natural language generation in the context of multimodal interaction in Portuguese

José Casimiro Pereira — 2012-01-01

In many situations, systems and people have to interact and share information. With demographic ageing a group of users that deserves special attention are the older adults. Multimodal interaction aims to improve the interaction between human users and electronic devices. A key technology for the output part of a Multimodal system is conversion of the concepts handled by systems into readable text or audible speech output, area with almost no work for Portuguese. As a starting point for the development of output generation modules for use in multimodal interaction contexts, we developed, as proof of concept, a prototype of a NLG module to support transmission of information on drugs to older adults based on a data-driven translation approach. First sample results of the generation are presented.

Implementação e avaliação de extensões à visualização de pedigrees baseada no Layout H-Tree

João Miguel Santos — 2012-01-01

The constant growth of available genealogicalinformation has encouraged the research of visualization techniques capable of representing the corresponding largeamount of data. An H-Tree Layout has been recently proposed to represent pedigree data as a way to overcome some of the limitations of traditional representations.However, this new technique has its own limitations which may hinder its adoption. In this paper, we propose some enhancements to the H-Tree Layout pedigree visualization technique in order to overcome some of the identified limitations. An implementation of the proposed enhancements and results of a preliminary evaluation are also provided.

Performance study of filtered back-projection algorithms implemented on GPUs

Bruno Faria — 2012-01-01

In recent years the use of graphical processing units (GPUs) in the diverse fields of science has increase dramatically. This increase is not only due to the GPU tremendous computational power, but also because they are relatively cheap when compared to clusters. In this work we explore the use of the GPU to reduce the computational time of the filtered back projection algorithm on computed tomography. To address the computational gain of the GPU implementation, two CPU implementations have been developed: single-core and multi-core. Both CPU implementations are benchmarked against the GPU implementation. In either case the GPU implementation proved to be a faster alternative. When compared to the CPU implementations the GPU was 273 times faster than the single-core CPU implementation and 34 times than the multi-core implementation.

Sudoku em FPGA

Tiago Vallejo — 2012-01-01

This paper describes the implementation ofaSudoku solver, developed in the context of reconfigurable systems. Thus, three solvers were developed: Simple, only able to solve simple puzzles, Trial and Error, whichimplements a Breadth-First Search algorithm, being able to solve more complex puzzles, and, finally, Trial and Error solver with the possibility of parallel processing. For theimplementation and test an FPGA of the Xilinx Spartan-3E family was used, using for the purpose a prototyping board from Digilent. The results were compared between the threeimplementations as well as with other state-of-the-art solvers. The project was developed within the Master Thesis “Sudoku em FPGA”.

Supporting mobility mechanisms in NovelContent centric networks

Daniel Corujo — 2012-01-01

There is a large set of efforts on the definition of new Internet architectures. One of the currently more relevant is the CCN, content-centric networking, architectural concept. This type of architectures is focused on file transferral and fail to address real time multimedia communications in mobile environments. This paper discusses the mobility mechanisms to improve the design of CCNs for interactive mobile systems, presenting three different architectural approaches.

Analysis and design of a limit-cycle envelope amplifier for wireless transmitters

Manuel J. Duarte — 2012-01-01

Limit-cycle or self-oscillating power amplifiers (SOPAs) are seen as a compact option to achieve efficient yet linear amplification of either complete RF signals or only their base-band envelopes. This paper summarizes the work carried out in the Master Thesis of the author, which consisted on the analysis and design of a limit-cycle amplifier, taking into account the propagation delay of the relay. For that, the theory of its working principle is discussed, and a prototype is built. During the work, a method to increase the self oscillation frequency for a fixed propagation delay and loop filter was proposed, which consists on replacing the relay with one that exhibits a novel kind of hysteresis. To validate the concept, simulations are carried out to compare the behavior of existing types of SOPA with the proposed one.

Simulador de sistemas de comunicações óticas: OSIP 2012

Bruno Pereira — 2012-01-01

This paper presents the potential of the new version of OSIP, OSIP 2012. considering the application in research and for teaching purposes. Also, the coherent systems are introduced and some of the concepts related with channel impairments. At last using the new features of the simulator, the performance of an optical coherent system will be assessed.

All-optical integrated system for 2D data wavelet transform and compression

Giorgia Parca — 2012-01-01

Optical transform is considered as a powerful tool for optical signal/image handling. Efficient schemes for data compression at the speed of light can be implemented, enabling lower processing requirements, energy efficiency, lower latency (transmission time), reduced memory usage. The goal is the development of parallel processing systems for 2D optical data maintaining functionalities in the optical domain. In this paper we present an all-optical integrated system for wavelet based decomposition and compression of 2D optical data.

3D interferometric integrated structure for all-optical wavelet transform

Giorgia Parca — 2012-01-01

In this paper, we present the design of a 3Dinterferometric structure based on a planar waveguides network, able to optically perform the wavelet decomposition of two dimensional input data, such as image pixels. The possibility to implement a system that could offer potential in terms of integrability and robustness is explored. This idea is supported by the existence of methods and optical architectures, based on interferometric structures, for the implementation of the optical wavelet transform. They enable parallel processing on one dimension of the input data and they can be enhanced with the development of structures able to parallelize the processing on two dimensional data.

Coherent fiber communications analyzer

Ricardo M. Ferreira — 2012-01-01

This paper addresses an coherent fiber communication analyzer with digital signal processing (DSP). First we make an overview of the investigations that are being conducted at Instituto de Telecomunicações (IT) in the coherent communications area and then introduce the coherent receiver used in the IT laboratory. We also present an interface developed in GUI of Matlab to analyze coherent signals.

PON Upstream traffic coexistence in a Stacked-PON environment

Tiago Mendes — 2012-01-01

A stacked-PON scenario using todays most deployed standards over the same fiber span was proposed and a coexistence upstream traffic scenario was simulated an experimentally evaluated.

Crosstalk de Raman em serviços de vídeo sobre redes óticas passivas de próxima geração (NG-PON2)

S. Brandão — 2012-01-01

Neste trabalho é avaliado o impacto causado pelo efeito de Raman sobre um sistema de vídeo overlay (1550nm) na evolução rumo à próxima geração de redes de acesso óticas passivas (NG-PON2). Em primeiro lugar é estudado o impacto causado por um sinal modulado e de seguida é analisado um sistema multi-comprimento DWDM.