Orientador: Marcelo El Khouri Buzato / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Estudos da Linguagem / Made available in DSpace on 2018-08-24T15:28:48Z (GMT). No. of bitstreams: 1 Coser_DeboraSecolim_M.pdf: 1772608 bytes, checksum: 4b688b9568a58756ad8960c57221aa5d (MD5) Previous issue date: 2014 / Resumo: Nesta dissertação discuto o conceito de ensino- aprendizagem colaborativa online por referência a dois contextos distintos. O primeiro é a plataforma Galanet, mantida por um consórcio de universidades européias, que visa estimular e desenvolver uma cultura de intercompreensão entre falantes de línguas românicas como alternativa à hegemonia do inglês na comunicação entre cidadãos europeus. O segundo é o site Busuu.com, que conecta pessoas ao redor do mundo dispostas a ensinar e aprender línguas entre si, sem a intervenção de tutores/moderadores profissionais. Em ambos os casos, o atrativo principal dos ambientes está na possibilidade de interagir com falantes nativos das línguas-alvo. O corpus analisado foi gerado na forma de registros provenientes proveniente das interlocuções da pesquisadora que participou de eventos colaborativos em ambos os espaços por seis meses. A fundamentação teórica abrange o exame de concepções de mediação oriundas de diferentes tradições teóricas assim como uma revisão histórica do conceito de aprendizagem colaborativa de línguas mediada por computador. A concepção de linguagem empregada é enunciativo-discursiva, fundamentada nos conceitos bakhtinianos de dialogismo, plurilinguismo, intercompreensão e gênero discursivo. O método empregado foi a Análise do Discurso Mediado por Computador proposta por Suzan Herring. Buscou-se, responder às seguintes perguntas de pesquisa: (i) quais as principais diferenças e semelhanças entre Busuu e Galanet em termos de mediações tecnológicas e político-pedagógicas? e (ii) de que modo o gênero Chat Pedagógico Plurilíngue e o gênero Chat Colaborativo em Duplas refletem essas semelhanças e diferenças? Os resultados mostraram que ambas as plataformas avançam em relação às propostas tradicionais da pedagogia de línguas, mas ainda estão aquém das dinâmicas de aprendizagem de línguas de caráter colaborativo e mediado por tecnologias digitais tais como os movimentos de desenvolvimento de softwares livres / Abstract: In this essay I discuss the concept of online collaborative teaching and learning by referring to two distinct contexts. The first one is the Galanet platform, maintained by European universities, which aims to encourage and develop a culture of mutual intelligibility between speakers of Romance languages as an alternative to the hegemony of English in communication amongst European citizens. The second one is the Busuu.com site that connects people around the world who are willing to teach and learn languages amongst themselves, without the intervention of tutors or professional moderators. In both cases, the most attractive characteristic of the environments is the possibility to interact with native speakers of the desired language. The corpus analyzed was generated in the form of records coming from the interactions of the researcher who participated in collaborative events in both platforms for a period of six months. The theoretical bases cover the concepts of mediation coming from different theoretical traditions, as well as a historical review of the concept of computer-mediated collaborative language learning. The conception of language is enunciative-discursive, based on the concepts of Bakhtinian dialogism, multilingualism, mutual understanding and discursive genre. The method employed was the Computer Mediated Discourse Analysis proposed by Suzan Herring. The research questions sought to be answered were: (i) What are the main differences and similarities between Busuu and Galanet in terms of technological and political-pedagogical mediations? And (ii) How does the Plurilingual Pedagogical Chat and Collaborative Chat in Pairs genres reflect these similarities and differences? The results showed that both platforms advances regarding the traditional language learning pedagogies, but are still below the dynamics of language learning and collaborative feature mediated by digital technologies, such as the development of Opens Source software / Mestrado / Linguagem e Educação / Mestra em Linguística Aplicada

Orientadores: Dalton Soares Arantes, Fábio Lumertz Garcia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-26T08:19:51Z (GMT). No. of bitstreams: 1 CarrionBetancourt_CarlosEnrique_M.pdf: 2602148 bytes, checksum: d14588789c8a464595b34613eb4822aa (MD5) Previous issue date: 2014 / Resumo: Esta dissertação estuda as técnicas de recuperação de frequência e fase de portadora em receptores ópticos coerentes, operando no modo rajada. Inicialmente, abordam-se a análise e modelagem das duas principais degradações que afetam a portadora, quais sejam, os desvios de frequência, que são produto da diferença de frequência entre o laser emissor e o oscilador local no receptor, e de ruídos de fase dos dispositivos a laser usados em comunicações ópticas coerentes. Usando os modelos de passeio aleatório (random walk) para o ruído de fase, os principais algoritmos de recuperação de frequência e de fase são revisados. Os estudos levam em consideração as novas tecnologias de lasers para comunicações, que asseguram alta estabilidade de frequência de curto prazo (short-term), para uso em receptores ópticos coerentes operando a taxas acima de 100 Gbps. Um projeto de preâmbulo especial foi concebido, a fim de viabilizar a obtenção de expressões analíticas para um estimador ótimo, no sentido do Mínimo Erro Quadrático Médio (MMSE). Resultados de simulações em MatLab/Simulink são apresentados para a validação dos resultados teóricos / Abstract: Frequency and phase estimation for carrier recovery in burst-mode coherent optical receivers are studied in this dissertation. Accurate models for frequency and phase deviations in communication lasers are initially studied, in order to present a tutorial study on frequency mismatch and phase recovery algorithms. Our studies take into account the current laser technology for optical communications using coherent receivers, especially the high short-term laser frequency stability for receivers operating above 100 Gbps. A special preamble design is presented for which an optimum estimator using the Minimum Mean-Square Error criterion is obtained. The estimator is given in closed-form solution with low computational space- and time-complexity. Simulation results in MatLab/Simulink are presented to validate the theoretical results. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientadores: Aldário Chrestani Bordonalli, Júlio César Rodrigues Fernandes de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T05:17:21Z (GMT). No. of bitstreams: 1 Diniz_JulioCesarMedeiros_M.pdf: 3463779 bytes, checksum: 7779aef72110b0e57aedeef25fc53b07 (MD5) Previous issue date: 2013 / Resumo: Sistemas de comunicações ópticas coerentes digitais permitem a utilização de formatos de modulação que carregam informação através de fase, amplitude e polarização do sinal óptico. Com o processamento digital dos sinais ópticos, é possível compensar as distorções inerentes à transmissão óptica, bem como realizar o sincronismo entre transmissor e receptor. Assim, junto ao avanço da eletrônica digital, a transmissão e recepção de sinais a centenas de gigabits por segundo se torna possível. Dentro desse cenário, os métodos comuns para a estimação de fase da portadora que chega ao receptor possuem baixa tolerância à dessintonia em frequência entre a portadora transmitida e o laser oscilador local. Nesta dissertação, é proposto e experimentalmente demonstrado um método de estimação de desvios de frequência de alimentação direta, com amplo alcance de estimação, eficiente, no ponto de vista de hardware, e compatível com os requisitos definidos pelo Fórum de Interconexões Ópticas (OIF ¿ Optical Internetworking Forum). Resultados obtidos experimentalmente mostram que o método proposto possui alta tolerância à assimetria espectral causada por filtragens no sinal / Abstract: Digital coherent optical systems allow the use of modulation formats that carry information through optical signal phase, amplitude and polarization. With digital processing of optical signals it is possible to compensate for distortions associated with optical transmission, as well as to perform timing and carrier synchronization. Thus, by also taking into account the current high speed electronic progress, transmission and reception of signals at hundreds gigabits per second has became possible. In this scenario, common carrier phase estimation methods have low tolerance to frequency offsets between transmitted carrier and local oscillator laser. This dissertation proposes and experimentally demonstrates a hardware-efficient, feed-forward, wide-range frequency offset estimator, compliant with Optical Internetworking Forum (OIF) requirements. Experimental results show that this method has high tolerance to the spectrum asymmetry caused by signal filtering / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

D.Ing. (Electrical and Electronic) / In this thesis, the problem of undetected errors in digital communication systems employing error detection as the only means of error control, is investigated. In the past, the undetected error probability of linear block codes, was mainly investigated on the binary symmetric channel, which is memoryless. With this thesis, the main aim was to investigate the undetected error probability for linear block codes, on channels with memory. The channel models investigated are the Gilbert-Elliott and Fritchman channel models. Three techniques for calculating the undetected error probability on channels with memory are investigated. These techniques are: (i) Exhaustive codeword generation, (ii) Simulation and (iii) A trellis based technique. The trellis description of a block code based on the states of a syndrome calculating linear feedback shift register, formed the basis of the latter technique. The calculation of the weight spectrum of binary linear block codes, is still largely an unsolved problem. Using the trellis description of a binary linear block code, referred to earlier, we propose a description of binary linear block codes based on graphs, and from this we develop a technique for calculating the weight spectrum of binary linear block codes. The weight spectra of block codes determine the undetected error probability of these codes when used on the binary symmetric channel. Very favourable results were obtained through the application of the techniques developed for undetected error probability calculation as well as weight spectrum calculation.

The ability to use Software Defined Radio (SDR) in the civilian mobile applications will make it possible for the next generation of mobile devices to handle multi-standard personal wireless devices and ubiquitous wireless devices. The original military standard created many beneficial characteristics for SDR, but resulted in a number of disadvantages as well. Many challenges in commercializing SDR are still the subject of interest in the software radio research community. Four main issues that have been already addressed are performance, size, weight, and power. This investigation presents an in-depth study of SDR inter-components communications in terms of total link delay related to the number of components and packet sizes in systems based on Software Communication Architecture (SCA). The study is based on the investigation of the controlled environment platform. Results suggest that the total link delay does not linearly increase with the number of components and the packet sizes. The closed form expression of the delay was modeled using a logistic function in terms of the number of components and packet sizes. The model performed well when the number of components was large. Based upon the mobility applications, energy consumption has become one of the most crucial limitations. SDR will not only provide flexibility of multi-protocol support, but this desirable feature will also bring a choice of mobile protocols. Having such a variety of choices available creates a problem in the selection of the most appropriate protocol to transmit. An investigation in a real-time algorithm to optimize energy efficiency was also performed. Communication energy models were used including switching estimation to develop a waveform selection algorithm. Simulations were performed to validate the concept.

In the past decade or so, significant advances were made in the field of Future Internet Architecture (FIA) design. Undoubtedly, the size of Future Internet will increase tremendously, and so will the complexity of its users’ behaviors. This advancement means most of future Internet applications and services can only achieve and demonstrate full potential on a large-scale basis. The development of network testbeds that can validate key design decisions and expose operational issues at scale is essential to FIA research. In conjunction with the development and advancement of FIA, cyber-infrastructure testbeds have also achieved remarkable progress. For meaningful network studies, it is indispensable to utilize cyber-infrastructure testbeds appropriately in order to obtain accurate experiment results. That said, existing current network experimentation is intrinsically deficient. The existing testbeds do not offer scalability, flexibility, and realism at the same time. This dissertation aims to construct a hybrid system of conducting at-scale network studies and experiments by exploiting the distributed computing ability of current testbeds. First, this work presents a synchronization of parallel discrete event simulation that offers the simulation with transparent scalability and performance on various high-end computing platforms. The parallel simulator that we implement is configured so that it can self-adapt for the performance while running on supercomputers with disparate architectures. The simulator could be used to handle models of different sizes, varying modeling details, and different complexity levels. Second, this works addresses the issue of researching network design and implementation realistically at scale, through the use of distributed cyber-infrastructure testbeds. An existing symbiotic approach is applied to integrate emulation with simulation so that they can overcome the limitations of physical setup. The symbiotic method is used to improve the capabilities of a specific emulator, Mininet. In this case, Mininet can be used to run applications directly on the virtual machines and software switches, with network connectivity represented by detailed simulation at scale. We also propose a method for using the symbiotic approach to coordinate separate Mininet instances, each representing a different set of the overlapping network flows. This approach provides a significant improvement to the scalability of the network experiments.

Future generations are built on the children of today. Thus, children's well- being and safety is of paramount importance. Children are making use of mobile devices, such as smart phones, to gain access to the Internet and other data driven mobile services. Children and parents alike are unaware of the risks they are exposed to when accessing such services. A clear lack of parental control over or awareness of this mobile use has been identified in South Africa. Without adequate awareness and successful use of a comprehensive mobile parental control solution, South African children may be at risk. This risk may include exposure to potentially harmful content and/or individuals. This dissertation presents a framework that supports the attainment of a comprehensive mobile parental control solution based on sound research.

A wireless mesh network is a mesh network implemented over a wireless network system such as wireless LANs. Wireless Mesh Networks(WMNs) are promising for numerous applications such as broadband home networking, enterprise networking, transportation systems, health and medical systems, security surveillance systems, etc. Therefore, it has received considerable attention from both industrial and academic researchers. This dissertation explores schemes for resource management and optimization in WMNs by means of network routing and network coding. In this dissertation, we propose three optimization schemes. (1) First, a triple-tier optimization scheme is proposed for load balancing objective. The first tier mechanism achieves long-term routing optimization, and the second tier mechanism, using the optimization results obtained from the first tier mechanism, performs the short-term adaptation to deal with the impact of dynamic channel conditions. A greedy sub-channel allocation algorithm is developed as the third tier optimization scheme to further reduce the congestion level in the network. We conduct thorough theoretical analysis to show the correctness of our design and give the properties of our scheme. (2) Then, a Relay-Aided Network Coding scheme called RANC is proposed to improve the performance gain of network coding by exploiting the physical layer multi-rate capability in WMNs. We conduct rigorous analysis to find the design principles and study the tradeoff in the performance gain of RANC. Based on the analytical results, we provide a practical solution by decomposing the original design problem into two sub-problems, flow partition problem and scheduling problem. (3) Lastly, a joint optimization scheme of the routing in the network layer and network coding-aware scheduling in the MAC layer is introduced. We formulate the network optimization problem and exploit the structure of the problem via dual decomposition. We find that the original problem is composed of two problems, routing problem in the network layer and scheduling problem in the MAC layer. These two sub-problems are coupled through the link capacities. We solve the routing problem by two different adaptive routing algorithms. We then provide a distributed coding-aware scheduling algorithm. According to corresponding experiment results, the proposed schemes can significantly improve network performance.

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