Frequency-domain receiver design for doubly-selective channels

This work is devoted to the broadband wireless transmission techniques, which are serious candidates to be implemented in future broadband wireless and cellular systems, aiming at providing high and reliable data transmission and concomitantly high mobility. In order to cope with doubly-selective channels, receiver structures based on OFDM and SC-FDE block transmission techniques, are proposed, which allow cost-effective implementations, using FFT-based signal processing. The first subject to be addressed is the impact of the number of multipath components, and the diversity order, on the asymptotic performance of OFDM and SC-FDE, in uncoded and for different channel coding schemes. The obtained results show that the number of relevant separable multipath components is a key element that influences the performance of OFDM and SC-FDE schemes. Then, the improved estimation and detection performance of OFDM-based broadcasting systems, is introduced employing SFN (Single Frequency Network) operation. An initial coarse channel is obtained with resort to low-power training sequences estimation, and an iterative receiver with joint detection and channel estimation is presented. The achieved results have shown very good performance, close to that with perfect channel estimation. The next topic is related to SFN systems, devoting special attention to time-distortion effects inherent to these networks. Typically, the SFN broadcast wireless systems employ OFDM schemes to cope with severely time-dispersive channels. However, frequency errors, due to CFO, compromises the orthogonality between subcarriers. As an alternative approach, the possibility of using SC-FDE schemes (characterized by reduced envelope fluctuations and higher robustness to carrier frequency errors) is evaluated, and a technique, employing joint CFO estimation and compensation over the severe time-distortion effects, is proposed. Finally, broadband mobile wireless systems, in which the relative motion between the transmitter and receiver induces Doppler shift which is different or each propagation path, is considered, depending on the angle of incidence of that path in relation to the direction of travel. This represents a severe impairment in wireless digital communications systems, since that multipath propagation combined with the Doppler effects, lead to drastic and unpredictable fluctuations of the envelope of the received signal, severely affecting the detection performance. The channel variations due this effect are very difficult to estimate and compensate. In this work we propose a set of SC-FDE iterative receivers implementing efficient estimation and tracking techniques. The performance results show that the proposed receivers have very good performance, even in the presence of significant Doppler spread between the different groups of multipath components.

Ultrasound velocity profile (UVP) measurements in shallow open-channel flows

1st European IAHR Congress, 6-4 May, Edinburgh, Scotland

Experimental study of proton induced nuclear reactions in 6,7 Li

This work presents the results of the experimental study of proton induced nuclear reactions in lithium, namely the 7Li(p,��) 4He, 6Li(p,��) 3He and 7Li(p,p)7Li reactions. The amount of 7Li and 6Li identified as primordial and observed in very old stars of the Milky Way galactic halo strongly deviates from the predictions of primordial nucleosynthesis and stellar evolution models which depend, among other factors, on the cross sections of reactions like 7Li(p,��) 4He and 6Li(p,��) 3He. These discrepancies have triggered a large amount of research in the fields of stellar evolution, cosmology, pre-galactic evolution and low energy nuclear reactions. Focusing on nuclear reactions, this work has measured the 7Li(p,��) 4He and 6Li(p,��) 3He reactions cross sections (expressed in terms of the astrophysical S -factor) with higher accuracy, and the electron screening effects in these reactions for different environments (insulators and metallic targets). The 7Li(p,��) 4He angular distributions were also measured. These measurementstook place in two laboratory facilities, in the framework of the LUNA (Laboratory for Undergroud Nuclear Astrophysics) international collaboration, namely the Laboratorio �� de Feixe de Ioes �� in ITN (Instituto Tecnologico �� e Nuclear) Sacavem, �� Portugal, and the Dynamitron-TandemLaboratorium in Ruhr-Universitat�� Bochum, Germany. The ITN target chamber was modified to measure these nuclear reactions, with the design and construction of new components, the addition of one turbomolecular pump and a cold finger. The 7Li(p,��) 4He and 6Li(p,��) 3He reactions were measured concurrently with seven and four targets, respectively. These targets were produced in order to obtain adequate and stable lithium depth profiles. In metallic environments, the measured electron screening potential energies are much higher than the predictions of atomic-physics models. The Debye screening model applied to the metallic conduction electrons is able to explain these high values. It is a simple model, but also very robust. Concerning primordial nucleosynthesis and stellar evolution models, these results are very important as they show that laboratory measurements are well controlled, and the model inputs from these cross sections are therefore correct. In this work the 7Li(p,p)7Li differential cross section was also measured, which is useful to describe the 7Li(p,��) 4He entrance channel.

Low-power 6-bit 1-GS/s two-channel pipeline ADC with open-loop amplification using amplifiers with local-feedback

IEEE International Symposium on Circuits and Systems, pp. 2258 ��� 2261, Seattle, EUA

Design and performance evaluation of turbo FDE receivers

Disserta����o apresentada na Faculdade de Ci��ncias e Tecnologia da Universidade Nova de Lisboa para obten����o do Grau de Mestre em Engenharia Electrot��cnica e de Computadores

Stochastic simulation of the morphology of fluvial sand channels reservoirs

Disserta����o para obten����o do Grau de Mestre em Engenharia Geol��gica (Georrecursos)

Linear amplification with multiple nonlinear devices

Disserta����o para obten����o do Grau de Mestre em Engenharia Electrot��cnica e Computadores

Effects of Spatial Pattern of GreenSpace on Land Surface Temperature: A case study on Oasis City Aksu, northwest China

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.

Signal transduction pathways involving the hypertension-related WNK1 and WNK4 protein kinases

Disserta����o apresentada para obten����o do Grau de Doutor em Biologia, na especialidade de Gen��tica Molecular, pela Universidade Nova de Lisboa, Faculdade de Ci��ncias e Tecnologia

Energy-efficient diversity combining for different access schemes in a multi-path dispersive channel

Disserta����o para obten����o do Grau de Doutor em Engenharia Electrot��cnica e Computadores

Wireless triple play system

Disserta����o para obten����o do Grau de Mestre em Engenharia Electrot��cnica e Computadores

High ffficiency transmission techniques for broadband wireless systems

Future broadband wireless systems are expected to cope with severely time dispersive channels, due to multi-path signal propagation between the transmitter and the receiver while having high power and spectral efficiency. Thus, advanced Frequency Domain Equalization techniques are required. The implementation complexity in mobile terminals should be as low as possible to achieve highest possible efficiency. Therefore, most of the signal processing requirements will be shifted to the base station and we will employ signals compatible with an efficient, grossly nonlinear power amplification. For this reason, we will consider offset modulation signals with quasi-constant envelope and develop receivers that will obtain good BER performance. However, these signals require a bandwidth significantly above the Nyquist rate, which can be reduced by an overlap of different frequency channels.

Design, implementation, and performance of a distributed and scalable sensor system for critical distance measurements in the CMS detector at LHC

The ���CMS Safety Closing Sensors System��� (SCSS, or CSS for brevity) is a remote monitoring system design to control safety clearance and tight mechanical movements of parts of the CMS detector, especially during CMS assembly phases. We present the different systems that makes SCSS: its sensor technologies, the readout system, the data acquisition and control software. We also report on calibration and installation details, which determine the resolution and limits of the system. We present as well our experience from the operation of the system and the analysis of the data collected since 2008. Special emphasis is given to study positioning reproducibility during detector assembly and understanding how the magnetic fields influence the detector structure.

A behavioral perspective on the effects of using performance measurement systems in the companies: Evidence from a case study

The effects of PMSs on the people���s behaviour represent a high degree of relevance in the context of an organization performance and success. Thus, motivational and behavioural consequences of performance measurements are far from being totally understood (Franco-Santos et al., 2012). This work project (WP) purposes going further regarding the consequences/effects on people���s behaviour of using PMSs in organizations. The researcher conducted 11 interviews to managers during a nine-month internship as a controller in a Portuguese multi-national company. The evidence from this WP suggests that the way how managers understand a PMS determines a lot the way how they behave. Data also supports that PMSs influences in several ways motivation, perceptions, participation and job-related stress of managers.

Omni-channel retail strategies in the luxury world

It���s impossible to neglect the changes that internet and e-commerce caused in the retail sector, by increasing customers��� expectations and forcing retailers to adapt the business to the new digital era. Internet is characterized by the increase in accessibility to everyone, which can be good or not so. For instance, luxury products rely on the sense of exclusivity, instead of being accessible to everyone. Hence, internet represents a challenge for luxury brands once, although they are able to provide a fullness service to their customers, they need to maintain the exclusiveness in which luxury is sustained. Consequently, the appearance of omni-channel was more than a challenge for the luxury sector, in particular, given the need to provide a full integrated experience through different channels. The aim of this dissertation is to find out how important is omni-channel, even in the luxury industry, and how it���s actually implemented based on the case of one of the most successful companies on luxury fashion e-commerce industry ��� Farfetch. Even though the company started in London, its founder is a Portuguese entrepreneur, and it���s in Portugal where most of its employees work, divided in two offices ��� Guimar��es e Porto. Therefore, a literature review was written on relevant concepts and ideas about luxury, e-commerce and the different channels��� approaches. There were formulated five propositions that were after discussed according to the information gathered about the company and its strategies. In the end, it was possible to identify which propositions are in accordance with theory and which are not, as well as understand which are the most important strategies and trends about omni-channel in the luxury fashion e-commerce sector.