Navegando por Assunto "Empirical radio propagation models"

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Acesso aberto (Open Access)
Modelo de rádio propagação em UHF para ambientes não homogêneos e climas distintos utilizando técnica de aprendizagem de máquina
(Universidade Federal do Pará, 2015-08-20) GOMES, Cristiane Ruiz; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
The digital TV broadcasts have greatly increased worldwide in recent years, especially in Brazil. The establishment and improvement of these transmission systems rely on models that take into account, among other factors, the geographical characteristics of the region, as these contribute to signal degradation. In Brazil, there is a great diversity of scenery and climates. For years several propagation models have been studied many for several frequency bands and types of paths. This thesis proposes an outdoor empirical radio propagation model for UHF band, which is used in digital TV. The proposed model estimates received power values can be applied to non-homogeneous paths and different climates, this latter presents innovative character for the UHF band. Different artificial intelligence techniques were chosen for theoretical and computational basis for having the ability to introduce, organize and describe quantitative and qualitative data quickly and efficiently, making it possible to determine the received power in a variety of settings and climates. The proposed model was applied to a city in the Amazon region with heterogeneous paths and wooded urban areas, fractions of freshwater among others. Measurement campaigns were conducted to obtain data signals from two digital TV stations in the metropolitan area of the city of Belém-Pará to model, compare and validate the model. The results are consistent. The model depicts a distinct difference between the two seasons of the studied year and small RMS errors for all cases studied. The validation of the model was based on the comparison with empirical and deterministic models.
Acesso aberto (Open Access)
Posicionamento otimo de estações rádio base do serviço móvel celular utilizando modelo de conhecimento discreto em propagação outdoor
(Universidade Federal do Pará, 2018-12-14) GOMES, Igor Ruiz; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
A good wireless network design depends on technical, financial and what criteria you want to meet. New technologies and services, such as transmission in 5G, and the reuse of frequencies, several new studies are being done to ensure the best project for a given area. This work presents a discrete radio propagation model that uses the K-nearest neighbors classifier. The model takes into account different attributes of an environment, the studied environment was in the dependencies of the Federal University of Pará (Pará-Brazil), representing a typically Amazonian environment. For design the model, measurement campaigns were carried out in three different frequencies: 521MHz, 2100 MHz, and 2600 MHz. The study of the fading in these frequencies was made to make a generalization of frequencies to include in the model. Two scenarios to optimize the positioning of the base stations under study were carried out. The proposed model was applied in some scenarios, showing the power received at each point, in addition, tests for frequency of 700 MHz were performed to show how good the polynomial obtained was in the generalization of the frequencies.