Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 139-152). Available also in a digital version from Dissertation Abstracts.

Digital Signal Processors (DSPs) have evolved to a level where it is feasible for digital modems with relatively low data rates to be implemented entirely with software algorithms. With current technology it is still necessary for analogue processing between the RF input and a low frequency IF but, as DSP technology advances, it will become possible to shift the interface between analogue and digital domains ever closer towards the RF input. The software radio concept is a long-term goal which aims to realise software-based digital modems which are completely flexible in terms of operating frequency, bandwidth, modulation format and source coding. The ideal software radio cannot be realised until DSP, Analogue to Digital (A/D) and Digital to Analogue (D/A) technology has advanced sufficiently. Until these advances have been made, it is often necessary to sacrifice optimum performance in order to achieve real-time operation. This Thesis investigates practical real-time algorithms for carrier frequency synchronisation, symbol timing synchronisation, modulation, demodulation and FEC. Included in this work are novel software-based transceivers for continuous-mode transmission, burst-mode transmission, frequency modulation, phase modulation and orthogonal frequency division multiplexing (OFDM). Ideal applications for this work combine the requirement for flexible baseband signal processing and a relatively low data rate. Suitable applications for this work were identified in low-cost satellite return links, and specifically in asymmetric satellite Internet delivery systems. These systems employ a high-speed (>>2Mbps) DVB channel from service provider to customer and a low-cost, low-speed (32-128 kbps) return channel. This Thesis also discusses asymmetric satellite Internet delivery systems, practical considerations for their implementation and the techniques that are required to map TCP/IP traffic to low-cost satellite return links.

Thesis (M.Eng.Sc.)--School of Electrical & Electronic Engineering , 2005.

[pt] Este trabalho teve como objetivo o levantamento de parâmetros para o auxílio no cálculo de desempenho e dimensionamento de sistemas digitais terrestres. Estes parâmetros forma obtidos através de medidas em enlaces analógicos pertencentes a Empresa Brasileira de telecomunicações e a Telesc, espalhados por todo o Brasil. Toda estrutura necessária para obtenção destes dados foi desenvolvida no CETUC. As principais características dos sistemas experimentais de medidas, programas para análise de dados, bem como uma descrição detalhada dos experimentos são apresentadas neste trabalho. Os resultados principais apresentados são as análises estatísticas de parâmetros de propagação em condições de céu claro. Nestes resultados estão incluídos as distribuições anuais, pior mês, desvanecimentos máximos e retardo. Os resultados obtidos foram também usados para avaliação de performance de alguns enlaces digitais. / [en] The aim this work was to obtain design parameters for terrestrial digital systems, and to Access their reliability and quality. These design parameters were obtained from measurements made in analogic links operated by the Brazilian telecommunication company Telebrás and Telesc, localised throughout Brazil.The techniques necessary to obtain the data were developed at CETUC. The main characteristcs of experimental links used in this work are presented, as well as the software used for the analyses. A complete description of the experimental set-up is also presented. The main results are the statistical analyses of the propagation parameters for cleae sky. Thes eresults include the annual attenuation, worst month attenuation, relative delay and maximum fading distributions. The results obtained were also used for performance evaluation of some digital links.

[pt] Em 2010, o Ministro das Comunicações instituiu o Sistema Brasileiro de Rádio Digital (SBRD). No entanto, um modelo de referência para o sistema ainda não foi definido. Este trabalho apresenta uma análise da radiodifusão sonora terrestre no Brasil e a partir desta são inferidos alguns requisitos para um rádio digital interativo. Esses requisitos são então utilizados para nortear a pesquisa. A relevância e importância do uso da NCL e do Ginga no rádio digital brasileiro, assim como acontece no Sistema Brasileiro de TV Digital (SBTVD), são discutidas, e a definição da forma como deve ser feito o transporte de aplicações NCL nos dois sistemas de rádio digital sendo considerados para adoção pelo país é realizada. Um novo perfil da linguagem NCL para o rádio digital é definido. Esse novo perfil recebeu o nome de perfil Digital Radio, ou simplesmente DR. O Ginga também é definido para uso em receptores de rádio digital, sendo que novos exibidores de mídia e recursos adaptados ao contexto do rádio digital são introduzidos. A implementação do Ginga da PUC-Rio é apresentada com as modificações necessárias para o rádio digital. Adicionalmente, um ambiente para validar a interatividade no rádio digital com o Ginga foi montado e testes exercitando toda a cadeia de transmissão e recepção de rádio digital com aplicações NCL embutidas foram realizados. As definições e conclusões que resultaram da pesquisa visam contribuir para a definição de um Sistema Brasileiro de Rádio Digital que seja poderoso em termos comunicacionais e agregue os recursos mais relevantes para o meio na era digital. / [en] In 2010, the Minister of Communications instituted the Brazilian Digital Radio System (SBRD), however a reference model for the system has not yet been set. This text presents an analysis of the terrestrial radio broadcasting in Brazil and presents some requirements for an interactive digital radio. These requirements are then used to guide the research. The relevance and importance of the use of NCL and Ginga in the Brazilian digital radio as in Brazilian Digital TV System (SBTVD), are discussed, and the definition of how the transport of NCL applications should be done in the two digital radio systems being considered for adoption by the country is performed. A new profile of NCL for use in digital radio is defined. This new profile was named Digital Radio Profile, or just DR. Ginga is also defined for use in digital radio receivers, and new media players and features adapted to the digital radio context are introduced. PUC-Rio s implementation of the Ginga middleware is presented with the necessary modifications for digital radio use. In addition, an environment to validate the interactivity in digital radio with the Ginga was assembled and tests exercising the entire digital radio chain of transmission and reception with embedded NCL applications were performed. The definitions and conclusions that resulted from research activities are expected to contribute to the definition of a Brazilian Digital Radio System that is powerful in communicational terms and aggregates the most relevant technologies for the medium in the digital age.

The C-Band All-Sky Survey (C-BASS) is a 1 GHz bandwidth survey of the radio sky in both intensity and polarization at a frequency of 5 GHz and with a resolution of 0.8. Northern and Southern sky coverage is provided by antennas located at the Owen’s Valley Radio Observatory (OVRO) in California, and the MeerKAT support base in South Africa, respectively. The primary science goal of C-BASS is to provide a highly sensitive C-Band all sky intensity and polarization map to augment the WMAP/Planck surveys. Removal of foregound contamination will place a limit on the success of Cosmic Microwave Background (CMB) experiments that attempt to detect the B-Mode polarization of the CMB. We will provide a HEALPix map (N_side=128) with an r.m.s. noise of 0.13 mK/pixel in Stokes Q and Stokes U, and a confusion limited r.m.s. noise of 0.8 mK/pixel in Stokes I. Removal of foregrounds at the higher frequency CMB surveys will be significantly improved by this lower frequency constraint. This thesis describes the development of the C-BASS gain-stabilized receiver capable of making sensitive measurements of both galactic total intensity and polarization. The receiver features a novel digital backend to provide spectral detail across the frequency band of interest. The analog signal conditioning uses a double sideband mixer to mix the RF frequencies to a DC–1000 MHz baseband for digitization. By changing the mixer frequency and/ or duplicating the signal conditioning and digital hardware, the RF frequency coverage can be modified for other projects. I also describe the process of converting a 7.6 m telecommunications dish to a high performance radio astronomy platform. The discussion includes dish surface measurements, optical design, and the development of an inexpensive telescope servo controller. The antenna conversion process and receiver design can be used to significantly reduce capital costs of future experiments, which is especially useful for short timescale experiments. The African VLBI (Nordling, 2012) is currently following a similar route to repurpose antennas across the African continent.

[pt] Um método, baseado no conceito de assinatura, foi desenvolvido para avaliar a influência da separação vertical entre as antenas na melhoria introduzida pala diversidade em espaço nos Sistemas Rádio Digitais. Para esta análise foram utilizadas estatísticas de desvanecimentos seletivos, medidos em enlaces radiovisibilidade no Brasil. Os resultados revelam a existência de uma separação ótima. Também é apresentado um método do estimativo para o cálculo da melhoria deste tipo de diversidade em espaço. / [en] A method base don the concept of signature for analysis of the improvement related to vertical antenna separation on digital radio with space diversity was developed. The analysis was performed on selective fading statistics obtained from measurements in LOS links in Brazil. The results reveal the existence of an optimum antenna separation. Also, a prediction method for evaluating this type of diversity improvement is presented.

[pt] Este trabalho examina os novos sistemas de transmissão, fibra ótica e rádio digital, sob o ponto de vista de sistema, procurando discutir métodos e sugerir critérios para o projeto e dimensionamento de enlaces. O trabalho inclui uma abordagem dos conceitos básicos, bem como uma análise de questões operacionais e econômicas existentes na aplicação a entroncamentos urbanos. / [en] This work analyses moderns transmission systems, optical fiber and digital radio, with the objectives to discuss methods and to suggest criterios for planning and design of radiolinks. The work contains basic concepts as well as operational and economic questions for urban conections.

Internet and digital media have profoundly reorganised the radio landscape by giving birth to new formats and patterns of radio listening. Today, traditional radio actors systematically use online platforms to diffuse their programs and communicate with their audience. This master thesis offers a case study and examines how Radio FIP, a French music station of public service, uses its digital devices to diffuse its program and produce content online. On the basis of existing researches on radio and radio diffusion online, and with the help of the concepts of format, media logics and hybrid media system, the author of this paper defines two logics of traditional radio and radio online used as reference in order to analysis the influence of media logics on the station’s material and formats online.   Observation of Radio FIP’s website and social media pages on Facebook and Twitter showed  a clear influence of radio online logics in the visual and informative extra content, the additional audio offers through online webradio streams, the promotion of non linear and asynchronous formats of radio listening’s and the incorporation of networked media frames. At the same time, logics of traditional radio prove to be also very significant with the pre-eminence and promotion of the station’s on air broadcast on digital devices and the reproduction of traditional radio patterns of temporality, music prescription and vertical communication on social media platforms. The coexistence of the two logics in Radio FIP online platforms characterises the station’s digital apparatus as a hybrid media space, and opens up new research trails for better understanding what influence the content formats of radio stations diffusing online.

[pt] As variações que ocorrem na estrutura da troposfera ao longo do tempo em relação à sua condição mediana provocam diversos fenômenos que fazem variar aleatoriamente o nível de sinal recebido num enlace rádio. Estas variações aleatórias são denominadas desvanecimentos. Os desvanecimentos são normalmente classificados em rápidos e lentos. Os desvanecimentos rápidos estão geralmente associados ao efeito de multipercurso atmosférico que é fortemente dependente da freqüência, sendo por isto denominados desvanecimentos seletivos, e são a principal causa de degradação do desempenho de enlaces rádio digitais de alta capacidade. Os modelos existentes para a caracterização estatística do desvanecimento por multipercurso são semi-empíricos e baseados em dados experimentais obtidos em regiões de clima temperado, acarretando uma má estimativa quando aplicados a regiões de clima tropical e equatorial. Neste trabalho é apresentada uma avaliação dos métodos existentes para previsão do desempenho de enlaces rádio digitais de alta capacidade, a partir da utilização de dados reais de desempenho extraídos de medidas em um tronco rádio de alta capacidade numa região tropical. / [en] The variations which happen in the troposphere layers throughout the time in relation to the median condition of the signal cause various phenomena that change the received signal level at digital radio relay systems randomly. The random changes are named fading. Fading is normally classified as fast or slow. The former is normally associated with the atmospheric multipath propagation and is strongly dependent on frequency; therefore, this is named selective fading and it is normally the cause of performance degradation in high capacity digital radio relays. The existing models for statistics of multipath fading are semi - empirical and based on experimental data extracts from regions the climate of which is temperate; and this gives a rough estimate with respect to the tropical and equatorial zones. This work presents an evaluation of existing methods of performance prediction for high capacity digital radio relay systems using real performance data obtained from measures of a high capacity digital radio link in operation in the tropical region.