This thesis investigates the potential for radio on the Internet to enhance processes of communication and media practice in the form of new a public sphere. Drawing on the work of Marshall McLuhan, the early stages of this thesis present an enquiry into the unique positive qualities of both radio and the Internet. The argument that follows contends that radio presented on the Internet can draw from the perceived technological benefits of each individual medium, combining as a potential site for public spheres. Both Habermas’s liberal public sphere and contemporary critiques of the concept are examined to define a range of principles that could be tested against relevant examples. The increasing commercialisation of the Internet is presented as a challenge to the normative ideals of a public sphere and counter-balances the optimism of a technologically determinist approach. A series of thematic codes are developed from the relevant theory and combined with qualitative interviews. This forms the framework for a thematic analysis of three individual case studies: Unwelcome Guests, an anti-corporate radio programme, SW Radio Africa, “the independent voice of Zimbabwe,” and NH Making Waves, the radio arm of a community peace activist group. The study investigates opportunities for these three individual case studies to act as public spheres, by examining the interplay that occurs between both Internet and radio practices. As the thematic analysis will demonstrate, placing radio content on the Internet presents new opportunities to diversify content and audiences through collaborative production and improved distribution. Recommendations for further research emphasise the need to pursue the Internet’s role in the public sphere potential of radio.

[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.

[pt] Recentemente, a UIT aprovou a recomendação G.826 que estabelece os padrões de desempenho dos enlaces digitais operando na ou acima da taxa de 64Kbits/s. Esta recomendação introduz novos conceitos e parâmetros de desempenho cujo impacto no dimensionamento de enlaces está ainda em processo de avaliação. É desenvolvida neste desenvolvida neste trabalho uma modelagem probabilística através da qual é feita uma análise dos parâmetros de desempenho da Recomendação G.826. O resultado desta análise é em seguida utilizado para estabelecer uma metodologia de dimensionamento de enlaces sujeitos a desvanecimento plano e seletivo, que é o caso típico de enlaces rádio digitais de alta capacidade. Esta metodologia é comparada com a que vem sendo elaborado no âmbito do grupo IX da UIT. / [en] Recently the ITU has approved the Recommendation G.826 that specified the performance of the physical layer of new broadband digital services. This recommendation has introduced new error performance parameters whose impact in the sytem design is still being evaluated. In this work a probabilistic model to analyse the G.826 error performance parameters is developed. These results are used to establish a new methodology for digital radio link design subject to flat or selective fading. Finally this metodology is compared with the one elaborated by Study Group IX of ITU-R.

In recent years, research on the design and performance evaluation of suboptimal receiver implementations has received considerable attention owing to complexity in the realization of the optimal receiver algorithms over wireless channels. This thesis addresses the effects of using reduced complexity receivers for the Satellite Digital Audio Radio (SDAR), Code Division Multiple Access (CDMA) and UltraWideband (UWB) communications technologies. A graphical-user-interface simulation tool has been developed to predict the link reliability performance of the SDAR services in the continental United States. Feasibility study of receiving both satellite and terrestrial repeater signals using a selection diversity (single antenna) receiver has also been performed. The thesis also develops a general mathematical framework for studying the efficacy of a sub-optimal generalized selection combining (GSC) diversity receiver over generalized fading channel models. The GSC receiver adaptively combines a subset of M diversity paths with the highest instantaneous signal-to-noise ratios (SNR) out of the total L available diversity paths. The analytical framework is applicable for rake receiver designs in CDMA and UWB communications. / Master of Science

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006. / John Papapolymerou, Committee Chair ; Joy Laskar, Committee Member ; John Cressler, Committee Member ; Alan Doolittle, Committee Member ; Clifford Henderson, Committee Member.

[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.

The system diagrams for the digital radio compatible with NASA's S-Band Space Network operating from 2025.8 - 2117.9 MHz (forward link) to 2200 - 2300 MHz (return link) are presented. The digital radio implementation includes binary phase shift keying (BPSK), quadrature phase shift keying (QPSK) and staggered quadrature phase shift keying (SQPSK). We have derived the system requirements for these modulation schemes from the Space Network User Guide (SNUG) and thereafter, derived system diagrams for the communication links. The designed system diagrams for the transceiver were implemented using Simulink models and USRP2 platform.

Made available in DSpace on 2015-05-07T14:46:40Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1217561 bytes, checksum: 80486693555edadcee476e93fee10422 (MD5) Previous issue date: 2012-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The question of content production for the communication media inserted in the scanning process and, consequently, the actual process of technological convergence issues are largely unexplored in the academic world. Accordingly, we set for digital radio, our object of study, the following problem: the media culture of radio mutations raise a new practice in digital content production. Regarding the approach to the problem this research is qualitative in nature. As the study's goals is characterized as an exploratory study, but is also structured on certain aspects that guide the dialectical approach, since our object is in an area of frequent mutation, the digital environment. The survey takes into account the four laws of media by McLuhan established about the consequences caused by technological innovations in media culture. The study is divided into five chapters, whose discussion turns to considerations of reinventing media, technological and cultural Brazilian radio, internet radio and the relationship, the reflection on the main characteristics of digital radio, its challenges, impacts and experiences , trends and perspectives, the approach of the current environment of technological convergence and its contributions to the design of new languages for radio content, the discussion about the new practice in the production of digital content from the literature review of media genres and the suggestion new radio formats that are based on the adoption of interactive features and contextually convergent able to enhance the performance of new users listeners of digital radio. / A questão da produção de conteúdos comunicacionais para as mídias inseridas no processo de digitalização e, consequentemente, no atual processo de convergência tecnológica são temas ainda pouco explorados no universo acadêmico. Nesse sentido, definimos para o rádio digital, nosso objeto de estudo, o seguinte problema: as mutações da cultura midiática radiofônica suscitam uma nova práxis na produção de conteúdos digitais. Em relação à abordagem do problema a presente pesquisa é de natureza qualitativa. Quanto aos objetivos pretendidos se caracteriza como um estudo exploratório, mas está estruturado também em certos aspectos que norteiam a abordagem dialética, uma vez que nosso objeto encontra-se em um espaço de mutação frequente, o ambiente digital. A pesquisa leva em consideração as quatro leis da mídia estabelecidas por McLuhan a respeito das consequências provocadas pelas inovações tecnológicas na cultura midiática. O estudo está dividido em cinco capítulos, cujas discussões se voltam para as considerações sobre a reinvenção midiática, tecnológica e cultural do rádio brasileiro; a relação rádio e internet; a reflexão sobre as principais características do rádio digital, seus desafios, impactos, experiências, tendências e perspectivas; a abordagem do atual cenário de convergência tecnológica e suas contribuições para a concepção de novas linguagens para os conteúdos radiofônicos; a discussão sobre a nova práxis na produção dos conteúdos digitais a partir da revisão de literatura sobre os gêneros midiáticos e a sugestão de novos formatos radiofônicos que tenham como base a adoção de características contextualmente interativas e convergentes capazes de potencializar a atuação dos novos usuários-ouvintes do rádio digital.

Master’s thesis deals with design and practical realisation of electronic circuits, which are needed for assembling of DRM signal transmitter for ham short waves bands. There is presented DRM standard as well as there are described the differencies between DRM for radio broadcast and for ham using. There is described design of input audio circuits, modulator, mixer, local generator, amplifier and filters. Principle of used SSB modulator is based on phase method, often called Tayloe modulator. This principle is analysed in detail including mathematical description, which was derived. It is possible to control the transmitter by program running at computer, communication takes place via USB. There is described establishment of communication in this work too.