Characterization and modelling of software defined radio front-ends

O presente trabalho tem por objectivo estudar a caracterização e modelação de arquitecturas de rádio frequência para aplicações em rádios definidos por software e rádios cognitivos. O constante aparecimento no mercado de novos padrões e tecnologias para comunicações sem fios têm levantado algumas limitações à implementação de transceptores rádio de banda larga. Para além disso, o uso de sistemas reconfiguráveis e adaptáveis baseados no conceito de rádio definido por software e rádio cognitivo assegurará a evolução para a próxima geração de comunicações sem fios. A ideia base desta tese passa por resolver alguns problemas em aberto e propor avanços relevantes, tirando para isso partido das capacidades providenciadas pelos processadores digitais de sinal de forma a melhorar o desempenho global dos sistemas propostos. Inicialmente, serão abordadas várias estratégias para a implementação e projecto de transceptores rádio, concentrando-se sempre na aplicabilidade específica a sistemas de rádio definido por software e rádio cognitivo. Serão também discutidas soluções actuais de instrumentação capaz de caracterizar um dispositivo que opere simultaneamente nos domínios analógico e digital, bem como, os próximos passos nesta área de caracterização e modelação. Além disso, iremos apresentar novos formatos de modelos comportamentais construídos especificamente para a descrição e caracterização não-linear de receptores de amostragem passa-banda, bem como, para sistemas nãolineares que utilizem sinais multi-portadora. Será apresentada uma nova arquitectura suportada na avaliação estatística dos sinais rádio que permite aumentar a gama dinâmica do receptor em situações de multi-portadora. Da mesma forma, será apresentada uma técnica de maximização da largura de banda de recepção baseada na utilização do receptor de amostragem passa-banda no formato complexo. Finalmente, importa referir que todas as arquitecturas propostas serão acompanhadas por uma introdução teórica e simulações, sempre que possível, sendo após isto validadas experimentalmente por protótipos laboratoriais.

The discursive construction of Portuguese national identity in the media thirty years after the 1974 revolution

Tese dout., Philosophy, Lancaster University, 2010

Radio over fiber broadband access networks architectures based on wavelength division multiplexing techniques

The recent remarkable growth in bandwidth of both wired optical and wireless access networks supports a burst of new high bandwidth Internet applications such as: peer-topeer file sharing, cloud storage, on-line gaming, video streaming, etc. Within this scenario, the convergence of fixed and wireless access networks offers significant opportunities for network operators to satisfy user demands, and simultaneously reduce the cost of implementing and running separated wireless and wired networks. The integration of wired and wireless network can be accomplished within several scenarios and at several levels. In this thesis we will focus on converged radio over fiber architectures, particularly on two application scenarios: converged optical 60 GHz wireless networks and wireless overlay backhauling over bidirectional colorless wavelength division multiplexing passive optical networks (WDM-PONs). In the first application scenario, optical 60 GHz signal generation using external modulation of an optical carrier by means of lithium niobate (LiNbO3) Mach- Zehnder modulators (MZM) is considered. The performance of different optical modulation techniques, robust against fiber dispersion is assessed and dispersion mitigation strategies are identified. The study is extended to 60 GHz carriers digitally modulated with data and to systems employing subcarrier multiplexed (SCM) mm-wave channels. In the second application scenario, the performance of WDM-PONs employing reflective semiconductor optical amplifiers (RSOAs), transmitting an overlay orthogonal frequency-division multiplexing (OFDM) wireless signal is assessed analytically and experimentally, with the relevant system impairments being identified. It is demonstrated that the intermodulation due to the beating of the baseband signal and wireless signal at the receiver can seriously impair the wireless channel. Performance degradation of the wireless channel caused by the RSOA gain modulation owing to the downstream baseband data is also assessed, and system design guidelines are provided.

Radio Frequency Synthesis for Power-Constrained Systems

Thesis (Ph.D.)--University of Washington, 2015

Compensation of undesired effects in MIMO wireless transceivers

This paper presents compensation of all undesired effects (Power Amplifier (PA) nonlinearity, transmitter and receiver antenna crosstalk, before-PA nonlinear crosstalk, Multiple Input Multiple Output (MIMO) channel fading and crosstalk) in MIMO Orthogonal Frequency Division Multiplex (OFDM) wireless systems. It has been demonstrated that reduced-complexity Crossover Digital Predistortion (CO-DPD) algorithm on transmitter side and Matrix Inversion algorithm on receiver side can suppress almost all undesired effects introduced by transmitter, channel and receiver in 4×4 MIMO OFDM System that can be used in modern wireless system applications. A significant complexity reduction is achieved due to the fact that Digital Signal Processing (DSP) during CO-DPD process on transmitter side is done with real instead of complex numbers.

Good Practice in EU Public Service Media and Contemporary Practice in Jordan: A Comparative Analysis

UNESCO Amman Office Foreword: UNESCO Amman office is pleased to publish a comparative analysis between good Public Service Media (PSM) practices in Europe and the contemporary practice in Jordan. The study is part of the Support to Media in Jordan project, funded by the European Union, aiming to increase media freedom, media independence and journalistic professionalism in Jordan. The state owned broadcaster, Jordan Radio and Television (JRTV), has informed, entertained and educated Jordanians for decades. JRTV reaches almost every corner of the Kingdom and has the potential to serve all Jordanians with balanced, impartial and accurate news and programmes relevant to their day-to-day lives.Based on this potential there has been a long standing ambition to transform the JRTV from a state broadcaster to a public service broadcaster; from a TV and radio that predominately serves the state, to a broadcaster that serves the public and is independent from the Government of the day. This ambition is expressed also in the Support to Media in Jordan project, agreed between the Government an the EU, under which UNESCO has been asked to produce two studies: The comparative PSM analysis and a broader media landscape assessment based on UNESCO’s Media Development Indicators (MDI’s). The Jordanian MDI assessment was carried out by a team of national and international researchers during the first six months of 2015, and builds on the rich flora of recent studies on the Jordanian media landscape, as well as on original research. The study is available in Arabic and English. Professor Naomi Sakr carried out the comparative PSM analysis parallel to the MDI study, and in close cooperation with the MDI research team and UNESCO Amman office.

Bi-Dimensional Characterization of a Wimax Radio Channel at 3.5GHz

This paper presents the characterization of an indoor Wimax radio channel using the Finite-Difference Time-Domain (FDTD) [1] method complemented with the Convolutional Perfect Matched Layer (CPML) technique [2]. An indoor 2D scenario is simulated in the 3.5GHz band (IEEE 802.16d-2004 and IEEE 802.16e-2005 [3]). In this study, we used two complementary techniques in both analysis, technique A and B for fading based on delay spread and technique C and D for fading based on Doppler spread. Both techniques converge to the same result. Simulated results define the channel as flat, slow and without inter-symbolic interference (ISI), making the application of the spatial diversity the most appropriate scheme.

RadiaLE: A framework for designing and assessing link quality estimators in wireless sensor networks

Stringent cost and energy constraints impose the use of low-cost and low-power radio transceivers in large-scale wireless sensor networks (WSNs). This fact, together with the harsh characteristics of the physical environment, requires a rigorous WSN design. Mechanisms for WSN deployment and topology control, MAC and routing, resource and mobility management, greatly depend on reliable link quality estimators (LQEs). This paper describes the RadiaLE framework, which enables the experimental assessment, design and optimization of LQEs. RadiaLE comprises (i) the hardware components of the WSN testbed and (ii) a software tool for setting-up and controlling the experiments, automating link measurements gathering through packets-statistics collection, and analyzing the collected data, allowing for LQEs evaluation. We also propose a methodology that allows (i) to properly set different types of links and different types of traffic, (ii) to collect rich link measurements, and (iii) to validate LQEs using a holistic and unified approach. To demonstrate the validity and usefulness of RadiaLE, we present two case studies: the characterization of low-power links and a comparison between six representative LQEs. We also extend the second study for evaluating the accuracy of the TOSSIM 2 channel model.

Neighbour list optimization for real LTE radio network

With the increasing complexity of current networks, it became evident the need for Self-Organizing Networks (SON), which aims to automate most of the associated radio planning and optimization tasks. Within SON, this paper aims to optimize the Neighbour Cell List (NCL) for Long Term Evolution (LTE) evolved NodeBs (eNBs). An algorithm composed by three decisions were were developed: distance-based, Radio Frequency (RF) measurement-based and Handover (HO) stats-based. The distance-based decision, proposes a new NCL taking account the eNB location and interference tiers, based in the quadrants method. The last two algorithms consider signal strength measurements and HO statistics, respectively; they also define a ranking to each eNB and neighbour relation addition/removal based on user defined constraints. The algorithms were developed and implemented over an already existent radio network optimization professional tool. Several case studies were produced using real data from a Portuguese LTE mobile operator. © 2014 IEEE.

Automated design of microwave discrete tuning differential capacitance circuits in Si-integrated technologies

A genetic algorithm used to design radio-frequency binary-weighted differential switched capacitor arrays (RFDSCAs) is presented in this article. The algorithm provides a set of circuits all having the same maximum performance. This article also describes the design, implementation, and measurements results of a 0.25 lm BiCMOS 3-bit RFDSCA. The experimental results show that the circuit presents the expected performance up to 40 GHz. The similarity between the evolutionary solutions, circuit simulations, and measured results indicates that the genetic synthesis method is a very useful tool for designing optimum performance RFDSCAs.

Non-uniform printed antenna array for wireless communications in sports arenas

Wireless communications had a great development in the last years and nowadays they are present everywhere, public and private, being increasingly used for different applications. Their application in the business of sports events as a means to improve the experience of the fans at the games is becoming essential, such as sharing messages and multimedia material on social networks. In the stadiums, given the high density of people, the wireless networks require very large data capacity. Hence radio coverage employing many small sized sectors is unavoidable. In this paper, an antenna is designed to operate in the Wi-Fi 5GHz frequency band, with a directive radiation pattern suitable to this kind of applications. Furthermore, despite the large bandwidth and low losses, this antenna has been developed using low cost, off-the-shelf materials without sacrificing quality or performance, essential to mass production. © 2015 EurAAP.

Three essays in risky behaviors

A PhD Dissertation, presented as part of the requirements for the Degree of Doctor of Philosophy from the NOVA - School of Business and Economics

Res Publica: Citizenship and Political Representation in Portugal, 1820-1926

The term res publica (literally “thing of the people”) was coined by the Romans to translate the Greek word politeia, which, as we know, referred to a political community organised in accordance with certain principles, amongst which the notion of the “good life” (as against exclusively private interests) was paramount. This ideal also came to be known as political virtue. To achieve it, it was necessary to combine the best of each “constitutional” type and avoid their worst aspects (tyranny, oligarchy and ochlocracy). Hence, the term acquired from the Greeks a sense of being a “mixed” and “balanced” system. Anyone that was entitled to citizenship could participate in the governance of the “public thing”. This implied the institutionalization of open debate and confrontation between interested parties as a way of achieving the consensus necessary to ensure that man the political animal, who fought with words and reason, prevailed over his “natural” counterpart. These premises lie at the heart of the project which is now being presented under the title of Res Publica: Citizenship and Political Representation in Portugal, 1820-1926. The fact that it is integrated into the centenary commemorations of the establishment of the Republic in Portugal is significant, as it was the idea of revolution – with its promise of rupture and change – that inspired it. However, it has also sought to explore events that could be considered the precursor of democratization in the history of Portugal, namely the vintista, setembrista and patuleia revolutions. It is true that the republican regime was opposed to the monarchic. However, although the thesis that monarchy would inevitably lead to tyranny had held sway for centuries, it had also been long believed that the monarchic system could be as “politically virtuous” as a republic (in the strict sense of the word) provided that power was not concentrated in the hands of a single individual. Moreover, various historical experiments had shown that republics could also degenerate into Caesarism and different kinds of despotism. Thus, when absolutism began to be overturned in continental Europe in the name of the natural rights of man and the new social pact theories, initiating the difficult process of (written) constitutionalization, the monarchic principle began to be qualified as a “monarchy hedged by republican institutions”, a situation in which not even the king was exempt from isonomy. This context justifies the time frame chosen here, as it captures the various changes and continuities that run through it. Having rejected the imperative mandate and the reinstatement of the model of corporative representation (which did not mean that, in new contexts, this might not be revived, or that the second chamber established by the Constitutional Charter of 1826 might not be given another lease of life), a new power base was convened: national sovereignty, a precept that would be shared by the monarchic constitutions of 1822 and 1838, and by the republican one of 1911. This followed the French example (manifested in the monarchic constitution of 1791 and in the Spanish constitution of 1812), as not even republicans entertained a tradition of republicanism based upon popular sovereignty. This enables us to better understand the rejection of direct democracy and universal suffrage, and also the long incapacitation (concerning voting and standing for office) of the vast body of “passive” citizens, justified by “enlightened”, property- and gender-based criteria. Although the republicans had promised in the propaganda phase to alter this situation, they ultimately failed to do so. Indeed, throughout the whole period under analysis, the realisation of the potential of national sovereignty was mediated above all by the individual citizen through his choice of representatives. However, this representation was indirect and took place at national level, in the hope that action would be motivated not by particular local interests but by the common good, as dictated by reason. This was considered the only way for the law to be virtuous, a requirement that was also manifested in the separation and balance of powers. As sovereignty was postulated as single and indivisible, so would be the nation that gave it soul and the State that embodied it. Although these characteristics were common to foreign paradigms of reference, in Portugal, the constitutionalization process also sought to nationalise the idea of Empire. Indeed, this had been the overriding purpose of the 1822 Constitution, and it persisted, even after the loss of Brazil, until decolonization. Then, the dream of a single nation stretching from the Minho to Timor finally came to an end.

Could concomitant radio-chemotherapy improve the outcomes of early-stage node negative anal canal cancer patients? A retrospective analysis of 122 patients.

One hundred twenty-two early-stage anal canal cancer patients (median age: 69 years) were treated with curative radiotherapy with (70 patients) or without (52 patients) concomitant chemotherapy. Median follow-up was 65 months (range: 4-238). At multivariate analysis, concomitant chemotherapy significantly improved local control (p = .007). Local control significantly influenced all considered endpoints, except the metastases free survival. The global rates of G3-G4 acute and late toxicity were 13.1% and 8.2%, respectively, and they were not increased by concomitant chemotherapy. Finally, concomitant chemotherapy is efficacious and safe in the treatment of T1-2N0 anal canal cancer patients and should be prospectively studied.