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In this thesis, the m-arity tree networks have been investigated to derive equations for their nodes, links and required wavelengths. The relationship among all parameters such as leaves nodes, destinations, paths and wavelengths has been found. Three situations have been explored, firstly when just one server and the leaves nodes are destinations, secondly when just one server and all other nodes are destinations, thirdly when all nodes are sources and destinations in the same time. The investigation has included binary, ternary, quaternary and finalized by general equations for all m-arity tree networks. Moreover, a multicast technology is analysed in this thesis to transmit data carried by specific wavelengths to several clients. Wavelengths multicast switching is well examined to propose split-convert-split-convert (S-C-S-C) multicast switch which consists of light splitters and wavelengths converters. It has reduced group delay by 13% and 29% compared with split-convert (S-C) and split-convert-split (S-C-S) multicast switches respectively. The proposed switch has also increased the received signal power by a significant value which reaches 28% and 26.92% compared with S-C-S and S-C respectively. In addition, wavelengths allocation algorithms in multicast technology are proposed in this thesis using tree networks topology. Distributed scheme is adopted by placing wavelength assignment controller in all parents’ nodes. Two distributed algorithms proposed shortest wavelength assignment (SWA) and highest number of destinations with shortest wavelength assignment (HND-SWA) algorithms to increase the received signal power, decrease group delay and reduce dispersion. The performance of the SWA algorithm was almost better or same as HND-SWA related to the power, dispersion and group delay but they are always better than other two algorithms. The required numbers of wavelengths and their utilised converters have been examined and calculated for the researched algorithms. The HND-SWA has recorded the superior performance compared with other algorithms. It has reduced number of utilised wavelengths up to about 19% and minimized number of the used wavelengths converters up to about 29%. Finally, the centralised scheme is discussed and researched and proposed a centralised highest number of destinations (CHND) algorithm with static and dynamic scenarios to reduce network capacity decreasing (Cd) after each wavelengths allocation. The CDHND has reduced (Cd) by about 16.7% compared with the other algorithms.

Made available in DSpace on 2016-04-04T18:31:31Z (GMT). No. of bitstreams: 1 Mateus Zegrini Nassar Garcia.pdf: 1207153 bytes, checksum: 9877adea8b2a851dc64c4374c0e8691c (MD5) Previous issue date: 2011-06-17 / The aim of this study was to evaluate experimentally a voice over IP (VoIP) streaming in opaque and all-optical networks. For this, we prepared an experimental setup to emulate the two types of networks. In particular, the experimental arrangement for opaque networks emulated packet loss and jitter; for all-optical networks the variation of the optical signal-to-noise ratio (OSNR) was emulated. The VoIP flow was generated by the G.711 and G.729 codecs, and the performance of these codecs in the emulated network was rated in terms of the R Factor, which is a computational tool developed by ITU-T and described by the Model E. The experimental results showed that G.711 codec has a better performance than the G.729 codec in opaque networks. On the other hand, the performance of G.729 was better in all-optical networks. Moreover, results for alloptical networks suggested that system performance depends not only on the OSNR, but also on the absolute value of the signal power. Results also showed that OSNRs higher than 14 dB did kept the factor R at its maximum. / O objetivo desse trabalho foi avaliar experimentalmente um fluxo de voz sobre IP (Voice Over IP, VoIP) em redes opacas e redes ?pticas transparentes. Para isso, foi montando um arranjo experimental emulando os dois tipos de redes. Em especial, nas redes opacas o arranjo experimental emulou perda de pacotes e varia??o do atraso e, nas redes ?pticas transparentes, foi emulada a varia??o da rela??o sinal-ru?do ?ptica (Optical Signal-to-Noise Ratio, OSNR). O fluxo de VoIP foi gerado pelos codecs G.711 e G.729, e a avalia??o do desempenho desses codecs nas redes emuladas foi feita em termos do Fator R, que ? uma ferramenta computacional desenvolvida pelo ITU-T e descrita pelo Modelo E. Os resultados experimentais permitiram concluir que, em geral, o codec G.711 possui um desempenho melhor do que o codec G.729 nas redes opacas. No entanto, nas redes ?pticas transparentes o desempenho do codec G.729 foi melhor. Al?m disso, os resultados para as redes ?pticas transparentes sugeriram que o desempenho do sistema depende n?o apenas da OSNR, mas tamb?m do valor absoluto da pot?ncia do sinal e ru?do. Os resultados tamb?m mostraram que OSNRs superiores a 14 dB mantiveram o fator R em seu m?ximo.

Multilevel Random Pulse Width Modulation (RPWM) schemes have drawn increasing attention in the past few years. Multilevel topologies provide high voltage and high power capabilities and random PWM schemes offer reduction in discrete harmonics spectral. This dissertation provides a generalized theory and analysis methods of the standard five-level Weighted RPWM (WRPWM). Equations have been derived to analyze the spectral performance and average switching frequency of the WRPWM output waveform using statistical approach. A modified WRPWM scheme has been proposed. The modified WRPWM scheme is then analyzed with the equations derived from the same approach. The analyzed theoretical spectrum of the standard five-level WRPWM is then compared with the three-level WRPWM scheme and the conventional carrier based PWM scheme. A scaled laboratory prototype diode clamping five-level inverter has been built for verification of the standard and the proposed modified WRPWM schemes. It can be seen that the experimental measurements and the theoretical analyzed results are all in good agreement. Results show the two five-level WRPWM schemes offers significant improvements on the spectrum content than the conventional carrier based PWM scheme. It was found that the five-level WRPWM schemes have successfully suppress the magnitude of third harmonic below 5% of the magnitude of fundamental component and even less for the higher order harmonic components. Research contributions made by the dissertation are: - The proposed modified multilevel WRPWM scheme which utilizing the switching decision redundancy of multilevel inverter to manipulate the harmonic content of the output signal. - The derived mathematical equations of the standard and modified five-level WRPWM scheme for analytical purposes. / Dissertation (MEng (Electrical Engineering))--University of Pretoria, 2005. / Electrical, Electronic and Computer Engineering / unrestricted

Poaching is a persistent issue that threatens many of earth’s species including therhino. The methods used by poachers are varied, but many use guns to carry outtheir illegal activities. Gunfire is extremely loud and can be heard for kilometres.This thesis investigates whether it is possible to aid anti-poaching efforts in Kenyawith a gunshot detection and estimation device using an array of microphones. Ifsuccessful, the device could be placed around the savannah or any exposed areaand warn if poaching is taking place in the nearby. If a shot is fired within theaudible range of the device’s microphones, a trained machine learning algorithmdetects the shot on the edge using a microprocessor. The detection runs in realtime and achieved an accuracy of 93% on an unbalanced data set, where themajority class was the one without gunshots. Once a detection has been made, thereceived signal power to each microphone is used to produce a direction of arrivalestimate. The estimate can produce an angle estimate with a standard deviationof 66.78° for a gunshot, and with a standard deviation of 7.65° when testing themodel with white noise. Future implementations could use several devices thatdetected the same event, and fuse their estimates to locate the shooter’s position.All of this information, as well as the sound file, can be used to alert and assistlocal wildlife services. The challenges of this project have been centred aroundmaking a system run in real time with only a microprocessor on the edge, whilealso prioritizing low cost components for future deployment. / Project Ngulia

Um estudo comparativo entre os principais modelos empíricos e semi-empíricos de predição de nível de sinal para comunicações móveis celulares é descrito neste trabalho. Medidas de cobertura outdoor em ambiente urbano foram comparadas com os resultados simulados a partir dos modelos de Okumura-Hata e Lee, lkegami, Walfisch-Bertoni e Walfisch-Ikegami. As medidas de potência de sinal recebido foram realizadas na cidade de Conceição das Alagoas, MG, a partir da única estação rádio-base (ERB) da cidade, operando na banda A com tecnologia AMPS/TDMA. Foi utilizada como portadora de teste o canal de controle analógico 328. As informações foram coletadas em algumas ruas da cidade, por meio de equipamento instalado em veículo, em diferentes posicionamentos em relação a ERB, de forma a se obter amostras de cobertura em diferentes cenários, seja em visada direta, em obstrução parcial ou total. O modelo de Ikegami se mostrou apropriado para predição de níveis de sinal recebido no ambiente estudado, apresentando desvio médio 5,81 dB em relação às medidas realizadas. / A comparative study among the main empiric and semi-empiric models of prediction of signal leveI for cellular mobile communications is described in this work. Measurements of covering outdoor in an urban environment were compared to the simulated results from the models of Okumura-Hata, Lee, Ikegami, Walfisch-Bertoni and Walfisch-Ikegami. The measurements of received signal level were accomplished in some streets of the city of Conceição das Alagoas, MG, starting from the only radio base station of the city, operating in the A band with AMPS/TDMA technology. The 328-analog control channel was used as test carrier. The measurements were carried out using some equipment installed in a vehicle, in different positions in relation to the radio base station, in order to obtain covering profile in different circunstances such as line-of-sight, non line-of-sight, and partial obstruction. The model of Ikegami was shown appropriate for prediction of the received signal levels in the studied environment, exhibiting an average deviation of 5,81 dB in relation to the accomplished measurements.

Um estudo comparativo entre os principais modelos empíricos e semi-empíricos de predição de nível de sinal para comunicações móveis celulares é descrito neste trabalho. Medidas de cobertura outdoor em ambiente urbano foram comparadas com os resultados simulados a partir dos modelos de Okumura-Hata e Lee, lkegami, Walfisch-Bertoni e Walfisch-Ikegami. As medidas de potência de sinal recebido foram realizadas na cidade de Conceição das Alagoas, MG, a partir da única estação rádio-base (ERB) da cidade, operando na banda A com tecnologia AMPS/TDMA. Foi utilizada como portadora de teste o canal de controle analógico 328. As informações foram coletadas em algumas ruas da cidade, por meio de equipamento instalado em veículo, em diferentes posicionamentos em relação a ERB, de forma a se obter amostras de cobertura em diferentes cenários, seja em visada direta, em obstrução parcial ou total. O modelo de Ikegami se mostrou apropriado para predição de níveis de sinal recebido no ambiente estudado, apresentando desvio médio 5,81 dB em relação às medidas realizadas. / A comparative study among the main empiric and semi-empiric models of prediction of signal leveI for cellular mobile communications is described in this work. Measurements of covering outdoor in an urban environment were compared to the simulated results from the models of Okumura-Hata, Lee, Ikegami, Walfisch-Bertoni and Walfisch-Ikegami. The measurements of received signal level were accomplished in some streets of the city of Conceição das Alagoas, MG, starting from the only radio base station of the city, operating in the A band with AMPS/TDMA technology. The 328-analog control channel was used as test carrier. The measurements were carried out using some equipment installed in a vehicle, in different positions in relation to the radio base station, in order to obtain covering profile in different circunstances such as line-of-sight, non line-of-sight, and partial obstruction. The model of Ikegami was shown appropriate for prediction of the received signal levels in the studied environment, exhibiting an average deviation of 5,81 dB in relation to the accomplished measurements.