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A Multi-Ring Scatternet Topology with Self-Routing for Bluetooth NetworksLee, Jen-Yen 31 August 2004 (has links)
Bluetooth is a low-cost, low-power and short-range wireless communication technology, which operates in the global unlicensed 2.4GHz ISM band. Recently many people have paid close attention to do a lot of relevant research and product development on it. In addition to the scatternet formation problem, two major issues of Bluetooth, scheduling and routing, also greatly interest the researchers.
In this paper, we propose new scatternet topology architecture for Bluetooth networks, called multi-ring scatternet. The scatternet formation and packet routing method are presented. The self-routing property of multi-ring scatternet makes its routing method efficient and low overhead. Comparing to the Bluetree scatternet, the proposed scatternet is more reliable and relieves the bottleneck at root nodes. As compared with the BlueRing scatternet, it reduces the network diameter and average routing path. The simulation results reveal that our multi-ring scatternet topology gains better performance by the three metrics of number of piconets, average routing path length and throughput.
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Aplicação da otimização por enxame de partículas com topologia "multi-ring" na estimação de parâmetros de linhas de transmissão / Aplication of particle swarm optimization with “multi-ring” topology in the estimation of transmission line parametersArruda, Sérgio Alexandre Martins 03 November 2015 (has links)
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Previous issue date: 2015-11-03 / Present world demands high availability of electricity for various equipment, in a context in
which dominates the intensive use of technology. The electricity is transported from generation
centers to consumers through Transmission Lines (TLs), which in Brazil have significant
dimensions, given the continental size of the country, his predominantly hydro power plant
generation, located long distances from major centers consumption.
To ensure compliance of this high demand, often the electric power companies overload these
TLs, generating undesirable effects, such as the formation of arrow in the conductors, for example.
Monitoring of TL operating conditions is key part, therefore, to ensure system availability
and security.
This work aims in this context to present a method to assist in the monitoring of three-phase
TLs of simple circuit based on measurement of electric and magnetic fields of the line and in
application of an optimization procedure based on Particle Swarm Optimization metaheuristic,
with a topology denominated Multi-Ring, to estimate simultaneously the values of current,
voltage, cable-ground clearance of conductors and distance between phases, in a cross section
of the line, assisting electric power companies and the National Electric System Operator (ONS)
in the monitoring task.
The good results achieved, combined with its simplicity of implementation compared to other
methods and its robustness, indicate their suitability for estimating these parameters. Associated
with this, the reasonably low times obtained in the execution make it promising for use by the
electric power company and by the system operator as an auxiliary tool in monitoring TLs. / O mundo atual demanda alta disponibilidade de energia elétrica para equipamentos diversos, em
um contexto em que predomina o uso intensivo de tecnologia. A energia elétrica é transportada
dos centros de geração até os consumidores por meio de Linhas de Transmissão (LTs), que
no Brasil possuem significativas dimensões, dados o tamanho continental do país e a matriz
de geração predominantemente hídrica e localizada a longas distâncias dos grandes centros de
consumo.
Para assegurar o atendimento dessa alta demanda, muitas vezes as concessionárias do sistema
elétrico sobrecarregam essas LTs, gerando efeitos indesejáveis como a formação de flecha nos
condutores, por exemplo. O monitoramento das condições de operação da LT é peça chave,
portanto, para garantir a disponibilidade e segurança do sistema.
Este trabalho visa, nesse contexto, apresentar um método que auxilie no monitoramento de
LTs trifásicas de circuito simples, com base na medição dos campos elétrico e magnético gerados
pela linha e na aplicação de um procedimento de otimização baseado na metaheurística
de Otimização por Enxame de Partículas (do inglês, Particle Swarm Optimization), com uma
topologia denominada Multi-Ring, para estimar simultaneamente os valores da corrente, tensão,
altura cabo-solo dos condutores e distância entre fases, em uma seção transversal da linha,
podendo auxiliar as concessionárias e o Operador Nacional do Sistema Elétrico (ONS) na tarefa
de monitoramento.
Os bons resultados alcançados, aliados à maior simplicidade de implementação em relação a
outros métodos e à sua robustez, indicam sua adequação para a estimação desses parâmetros.
Associado a isso, os tempos razoavelmente baixos obtidos na execução o tornam promissor
para aplicação por concessionárias e pelo operador do sistema como ferramenta auxiliar no
monitoramento de LTs.
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Design And Analysis Of Microstrip Ring Antennas For Multi-frequency OperationsBehera, Subhrakanta 06 1900 (has links) (PDF)
In this research we attempted several modifications to microstrip ring/loop antennas to design multi-frequency antennas through systematic approaches. Such multi-frequency antennas can be useful while building compact terminals to operate at multiple wireless standards. One of the primary contributions was the use of a capacitive feed arrangement that enables simultaneous excitation of multiple concentric rings from an underlying transmission line. The combined antenna operates in the same resonant bands as the individual rings and avoids some of the bands at harmonic frequencies.
A similar feeding arrangement is used to obtain dual band characteristics from just one ring, with improved bandwidth. This is made possible by widening two adjacent sides of a square ring antenna symmetrically, and attaching an open stub to the inner edge of the side opposite to the feed line. Use of fractal segments replacing the side with the stub also results in a similar performance. Use of fractal geometries has been widely associated with multi-functional antennas. It has been observed from the parametric studies that, the ratio of the resonant frequencies can range from 1.5 to 2.0. This shows some flexibility in systematically designing dual-band antennas with a desired pair of resonant frequencies.
An analysis technique based on multi-port network modeling (MNM) has been proposed to accurately predict the input characteristics of these antennas. This approach can make use of the ordered nature of fractal geometries to simplify computations. Several prototype antennas have been fabricated and tested successfully to validate simulation and analytical results.
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