Dissertações em Engenharia Elétrica (Mestrado) - PPGEE/ITEC

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2316

O Mestrado Acadêmico inicou-se em 1986 e pertence ao Programa de Pós-Graduação em Engenharia Elétrica (PPGEE) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará (UFPA).

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Agora exibindo 1 - 20 de 56

Acesso aberto (Open Access)
5G MIMO and LIDAR data for machine learning: mmWave beam-selection using deep learning
(Universidade Federal do Pará, 2019-08-29) DIAS, Marcus Vinicius de Oliveira; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
Modern communication systems can exploit the increasing number of sensor data currently used in advanced equipment and reduce the overhead associated with link configuration. Also, the increasing complexity of networks suggests that machine learning (ML), such as deep neural networks, can effectively improve 5G technologies. The lack of large datasets make harder to investigate the application of deep learning in wireless communication. This work presents a simulation methodology (RayMobTime) that combines a vehicle traffic simulation (SUMO) with a ray-tracing simulator (Remcom’s Wireless InSite), to generate channels that represents realistic 5G scenarios, as well as the creation of LIDAR sensor data (via Blensor). The created dataset is utilized to investigate beam-selection techniques on vehicle-to-infrastructure using millimeter waves on different architectures, such as distributed architecture (usage of the information of only a selected vehicle, and processing of data on the vehicle) and centralized architectures (usage of all present information provided by the sensors in a given moment, processing at the base station). The results indicate that deep convolutional neural networks can be utilized to select beams under a top-M classification framework. It also shows that a distributed LIDAR-based architecture provides robust performance irrespective of car penetration rate, outperforming other architectures, as well as can be used to detect line-of-sight (LOS) with reasonable accuracy.
Acesso aberto (Open Access)
Acoplamento de modos guiados em cabos de pares trançados utilizando antenas com simetria radial no cenário terabit DSL
(Universidade Federal do Pará, 2020-03-26) SOUSA, Brenda Penedo Tavares de; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The development of data transmission standards and access technologies has always been linked to the need to supply high data rates. Thus, technologies already implemented, such as the DSL (Digital Subscriber Line) system that uses twisted pairs for transmission, have been adjusting to support this growing data demand. In DSL systems, the twisted pairs are used as a transmission line, using the transverse electromagnetic mode (TEM). However, the physical limitations of the twisted pair as a transmission line prevent the system from achieving higher rates, needed to support fifth generation (5G) applications. Recently, it was proposed to use other transmission modes in the twisted pair, the higher order guided modes, as an alternative for this structure to be able to support transmission rates of the order of Terabits per second, having been termed as the Terabit DSL technology (TDSL). However, one of the challenges for this implementation is the coupling of the guided modes in the twisted pair, since they are not widely explored in the context of the propagation of higher-order guided modes, as simpler waveguides, such as Sommerfeld and Goubau. In this scenario, this dissertation aims to evaluate the coupling of the radiated signal between an antenna with radial propagation and the twisted pair cable, analyzing the electromagnetic behavior of structures. Considering that the twisted pair cable does not have a closed analytical model for the behavior of higher order modes, which propagate along these structures, all the results were obtained from numerical simulations in the software HFSS (High Frequency Structure Simulator).These results are in terms of the scattering parameter of the antenna and the electromagnetic field in the cable, making it possible to evaluate the coupling efficiency, the signal guidance and to predict the transmission rate available to users. The results obtained showed that the coupling between the antenna and the unshielded twisted pair cable reached levels of up to 83.83 % at frequencies of 0.15 THz, demonstrating a high coupling efficiency when compared to simpler scenarios in the literature, reaching levels on average 67 %. It was found that the use of these cables for data transmission is effective, managing to deliver rates of up to 1.737 Tbps in cables of up to 10 meters, while the rate forecasts for the TDSL scenario that consider the 100 % coupling reach levels of 2.013 Tbps.
Acesso aberto (Open Access)
Análise comparativa de nanoantenas plasmônicas no modo de recepção para a aplicação em nanocircuito óptico.
(Universidade Federal do Pará, 2020-01-30) LOPES, Patrik Coelho; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647; https://orcid.org/0000-0003-4393-3217
In this work, a theoretical study is made for different cases of optical nanoantennas. Numerical analyzes are performed using the Finite Element Method (FEM). The first part of the analysis will be done with the isolated nanoantennas considered: dipole,dipole-loop, loop and rod-loop. Initially it is made for the transmission mode to obtain important parameters for the study of nanoantennas, such as input impedance, reflection coefficient, radiation efficiency and gain diagram. Later in reception mode, excited by a plane wave linearly polarized, varying the direction of polarization. Where the power received by charge versus frequency and the near-field electric are investigated for antennas. The results show that the case of the dipole-loop nanoantenna is the most efficient (reaching up to and er = 81.25%) in addition to a better reception band. The second part is presented the application of an optical nanocircuit, composed of the receiving loop connected to a bifilar Optical Transmission Line (OTL) with a dipole at the line end. Also investigated are the near-field and the received power for the nanocircuits analyzed separately, with a load at the terminal of the streaming. Finally, the excitation of the nanocircuit is done through an opening probe modeled by a gaussian beam, focused on the receiving loop, transferring energy to the emitting dipole, with a standing wave pattern, the electromagnetic coupling of the nanocircuit turns with the Gaussian beam, showed better results (with a maximum reached of PZC = −103 dBm) compared to the plane wave (with value maximum of PZC = −125 dBm), with the power received at the load of ZC = 50Ω.
Acesso aberto (Open Access)
Análise comparativa do desempenho da compensação da dispersão em redes de fibras ópticas
(Universidade Federal do Pará, 2019-12-13) LUZ, Fabrício Pinho da; COSTA, Marcos Benedito Caldas; http://lattes.cnpq.br/7636226766852440
Este trabalho aborda o uso de métodos para tratamento da dispersão em fibras ópticas, mostrando a eficácia da utilização para um melhor resultado do Fator de qualidade (Q. Factor) e da taxa de erro de bit (Min. Ber) na transmissão de dados por redes de fibras ópticas. Desse modo, esta dissertação tem por objetivo fazer uma análise do desempenho de uma das técnicas de Pós-compensação em sistemas Multiplexação por Divisão de Comprimento de Onda Densa, baseado em redes ópticas passivas (DWDM-PON) com 16 canais e 100GHz de espaçamento para uma taxa de transmissão de dados de 10Gbps através do método de Pós-compensação de dispersão; propõe a utilização de técnicas de dispersão, a de Pós-compensação e a de dispersão Cromática na transmissão de dados por fibras ópticas com utilização de fibras compensadoras de dispersão (DCF) e Fibras de Grade de Bragg (FBG) para um melhor resultado do fator de qualidade (Q-Factor) e da taxa de erro de bit (Min Ber). A metodologia aplicada teve base em levantamentos bibliográficos de trabalhos na mesma linha de pesquisa sobre métodos de tratamento dos efeitos não lineares, em especial o de dispersão em fibras ópticas; em seguida foi feita a modelagem da rede óptica no software OptiSytem da Optiwave Corporation para implementação das simulações dos métodos utilizados para tratamento da dispersão em fibras ópticas. Concluiu-se, a partir do estudo de três sistemas de compensação de dispersão, onde uma ligação DCF e uma ligação FBG foram utilizadas para esse fim, que os valores do fator Q e do BER foram comparados e analisados a uma taxa de transmissão de 10 Gb/s; que o fator Q e o OSNR para o sistema de compensação de simétrica (mista) eram os maiores, estas técnicas de compensação de dispersão diminuem a degradação do sinal, melhorando a transmissão dos dados no sistema, com fibra DCF as perdas totais aumentam devido os efeitos não lineares, e seu custo é maior do que a fibra FBG, ou seja, com fibra FBG, o custo do sistema é menor, porém seu alcance é limitado. Portanto as duas técnicas podem ser utilizadas dependendo dos requisitos da rede do projeto de telecomunicações.
Acesso aberto (Open Access)
Análise da Coexistência entre Sistemas 5G e Serviços Fixos na Faixa de Ondas Milimétricas
(Universidade Federal do Pará, 2019-10-07) TEIXEIRA, Fátima Priscila Araújo; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
This works aims to analyze the impact of interference of a 5G system over a legacy 26 GHz fixed point-to-point system and, thus, obtain a minimum protection distance for the fixed system not be affected by the 5G system. To obtain these results, simulations were performed using the Monte Carlo method. The impact of 5G network co-channel interference on the fixed service was evaluated considering different parameters such as fixed antenna height, cell number, fixed antenna gain and number of users. In the results obtained, the 7-cell tri-sectored network topology, combined with a 60 m of fixed antenna height, had the greatest impact on the required protection distance, while other parameters such as gain and power had a moderate impact. These results imply that coexistence will be possible when all appropriate parameters are measured for each case in question. Another contribution of this dissertation is the availability of a coexistence model in the SEAMCAT simulator, which can help new scenarios for coexistence analysis.
Acesso aberto (Open Access)
Análise de canal para frequência de 3,5 GHz em aeroporto
(Universidade Federal do Pará, 2022-01-28) MACEDO, Alex Sanches; BARROS, Fabrício José Brito; http://lattes.cnpq.br/9758585938727609; http://lattes.cnpq.br/9758585938727609
With the constant evolution of technology and communication systems, the increase in data exchange, speed and reliability regarding access to the mobile network has reinforced. Several causes such as spectral deficiency, difficulties in signal coverage, problems with antennas and radio link, are obstacles to be worked on and improved in order to provide services with higher quality within a mobile communication network infrastructure. To meet the vertiginous increase in the consumption of users and equipment connected to the mobile network, several works and researches are being proposed and developed. In Brazil, the arrival of fifth generation technology (5G) is expected from 2021, which will use the frequency band of 3.5 GHz. 5G promises fast connectivity with more users covering services and applications that demand high data rates over a wide coverage area. In particular, on this frequency that represents a sub-6 GHz band to be used for 5G in Brazil. As for the behavior of the channel, the characterization of this channel is of important relevance. Thus, in this dissertation, the study on channel analysis for the frequency of 3.5 GHz in a large indoor environment was motivated, this scenario is in a lobby of the International Airport Val de Cans, in Belém do Pará. measurements were performed for Line-Of-Sight (LOS) and through channel probing the dispersion parameters of the small-scale channel are extracted. These parameters are the average RMS delay and average RMS spread, the channel coherence band and the power profile and delays were also verified. Understanding large-scale signal propagation is important for designing mobile radio systems. The signal was also investigated through the Floating-Intercept (FI), Close-In (CI) models and their variations are applied and analyzed to evaluate the path loss for co-polarization (V-V and H-H) and cross-polarization (V-H and H-V ). It can be inferred that the methodology applied on a large scale proved to be adequate with the data and, when compared to other types of environments and other frequencies found in the literature.
Acesso aberto (Open Access)
Análise de desempenho de redes de acesso G.mgfast e fronthaul 5G baseado em cabos coaxiais
(Universidade Federal do Pará, 2019-05-27) FREITAS, Marx Miguel Miranda de; NUNES, Diogo Lobato Acatauassú; http://lattes.cnpq.br/1972007941497086; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
This work explores two possibilities of harnessing mature cabling technologies used in broadband networks of 4th generation systems in emerging next generation applications. Specifically, two proposals for using the cabling structure of Hybrid Fiber Coax and SAT TV (Satellite Television) systems are evaluated. The first one, as support in 5G network analog transport networks (fronthaul). The second evaluates the use of coaxial cables in access networks G.mgfast (Multi Gigabit G.fast). In the firs one, It is shown the relationships between the data rates and the number of antennas reached by the coaxial cable RG06, under a fixed power level and a target signal noise condition, considering different distances and two configurations of radio signals. It is shown that in the 5G analogue fronthaul analyzed, rates higher than 40 Gbps can be obtained in a RG06 coaxial cable, giving support to 140 antennas, meeting 3GPP transmission criteria. The second solution proposes a process to reduce power consumption in the network, by adapting the transmission power in the coaxial network, with higher bit load in the initial frequencies of the spectrum. Links with RG59, RG06 and RG11 coaxial cables are analyzed, considering rates ranging from 5 Gbps to 10 Gbps and two types of bit loading algorithms. It is shown that with these procedures the power saving obtained in single link with 100 m coaxial cable can be used to power another 28 cables of 50 m. On the other hand, it is shown that the power reduction is not relevant, from the point of view of redistribution, in cables whose length is less than or equal to 25 m.
Acesso aberto (Open Access)
Análise de desempenho deum sistema óptico baseado em interferômetro de Mach-Zehnder e amplificador óptico semicondutor
(Universidade Federal do Pará, 2024-11-18) ARAÚJO, Fábio Souza de; COSTA, Marcos Benedito Caldas; http://lattes.cnpq.br/7636226766852440
The present work introduces and explores, using the OptiSystem software, the performance of an optical system that combines the Mach-Zehnder interferometer, the semiconductor optical amplifier (SOA), and the Fiber Bragg Grating (FBG). The system is composed of three main parts: the transmission section, the semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) section, and the reception section. The performance parameters analyzed include the quality factor (Q-Factor) and the bit error rate (BER) for different bit sequences and variations in the optical fiber length. Overall, the proposed system demonstrated good performance, proving to be a viable design for metropolitan networks with links up to 50 km.
Acesso aberto (Open Access)
Análise de nanoenlaces ópticos sem fio compostos por nanoantenas plasmônicas yagi-uda e dipolo
(Universidade Federal do Pará, 2019-12-17) GARCIA, Tiago dos Santos; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work shows a comparative theoretical analysis of plasmonic nanoantennas Yagi-Uda and dipole wireless optical nanolinks. All results found from the isolated antennas at transmission mode such as, input impedance, directivity, gain, radiation efficiency, reflection coeficiente and radiation diagram were obtained by the linear Method of Moments, assitionally, the effect of a silicon dioxide substract on antenna resonant properties were obtained by the Finite Element Method through COMSOL Multiphysics software. The numerical analysis of the nanolink is performed by the linear Method of Moments, witch the transmission power and the near electric field are investigated and optimized for the nanolinks Yagi-Uda/Yagi-Uda, Yagi-Uda/dipole and dipole/dipole. The results show that the Yagi-Uda/Yagi-Uda nanolinks offers an improvement in power transmission at some frequency points over the nanolinks dipole/dipole and Yagi-Uda/dipole. In addition, the results demonstrate that all three links can operate at good transmit power at different frequency points, varying the load impedance of the receiving antenna.
Acesso aberto (Open Access)
Análise de ressonâncias eletromagnéticas em estrutura periódica de discos de grafeno magnetizadosd na faixa de terahertz
(Universidade Federal do Pará, 2023-02-27) SILVA, Amanda Evangelista da; OLIVEIRA, Cristiano Braga de; http://lattes.cnpq.br/2012907724305086; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
Since its isolation in 2004, graphene has shown to be a promising material, as it allows strong interaction of charge carriers with terahertz (THz) radiation. This extensive interaction with light is due to the excitation of surface plasmon polaritons (SPPs) thus providing several applications in the areas of THz photonics. In the presence of an external magnetic field, the cyclotron resonance dominates in the THz spectra. In this work we analyze several resonance modes (dipole, quadrupole, hexapole and modes with azimuthal symmetry) that can exist in the graphene disk in an arrangement with periodic square unit cells. We calculated the resonances with magnetization by an external DC magnetic field ranging up to 3T and compared them with the case of the same structure without magnetization where it was observed that the presence of the magnetic field results in the splitting of some resonant modes. The resonant characteristics are numerically obtained using the COMSOL Multiphysics software in two distinct and complementary studies: the eigenfrequency calculation regime referring to the natural modes of resonance and the plane wave excitation with normal incidence. Floquet boundary conditions on the four sides of the unit cells are used to simulate the in-plane periodic structure of graphene. The unit cell side (i.e. the period of the matrix) used in the numerical calculation is A = 9µm, the radius of the graphene disk is D = 3µm. The problem of excitation of some modes is discussed from the point of view of the circular symmetry that, to generate the resonance peaks in this regime, had to be broken through a subtle cut in the shape of a rectangular slit of size Lx = 10nm by Ly = 550nm starting axially from the edge. The disk is modeled as a two-dimensional element, and this provides a good approximation of the atomic thickness of a single layer of this material. Conductivity is modeled by the semi-classical Drude model. The discussion of resonator properties is fulfilled in terms of graphene currents and electromagnetic fields outside graphene. Potential applications of the obtained results are Faraday and Kerr rotators, controllable filters and absorbers for THz photonic circuits
Acesso aberto (Open Access)
Análise de sensor plasmônico na configuração emissão acoplada via função de Green 3D
(Universidade Federal do Pará, 2018-09-28) CRUZ, André Felipe Souza da; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
In the present work, a theoretical study on a plasmon resonance sensor in the Surface Plasmon Coupled Emission (SPCE) configuration is presented. Coupled to the sensor structure is a microfluidic channel containing suspended target particles (gold nanoparticles functionalized to attract fluorescent molecules), which when excited and immobilized upon the sensor structure can be efficiently modeled as a planar array of induced dipoles. The electromagnetic modeling of the device was performed by the magnetic potential, defined by means of the Periodic Green Function (PGF) 3D. The electromagnetic fields are presented in terms of the discrete spectral representation by the complex double Fourier series, and to reduce the number of terms in the series, it is proposed the use the Euler identity. Firstly, parametric field results are presented in the sensor structure, and then the spectral analysis of the magnetic potential field is performed, where the SPP and SW poles appear in the spectral domain. For the validation of the method, the limit case was analyzed, in which the particles are distant from each other, and compared with published works. Finally, results and discussions about the convergence of series in the cosine PGF are presented. The results show good agreement, showing that the theoretical method of PGF 3D is efficient, and can be used as a tool in the design of this sensing device.
Acesso aberto (Open Access)
Uma Análise do uso de informacões multiescala no mapeamento da PSNR para pontuacão perceptual
(Universidade Federal do Pará, 2019-11-18) GONÇALVES, Luan Assis; ZAMPOLO, Ronaldo de Freitas; http://lattes.cnpq.br/9088524620828017; BARROS, Fabrício José Brito; http://lattes.cnpq.br/9758585938727609
The prediction of visual quality is crucial in image and video systems. For this task, image quality metrics based on the mean squared error prevail in the field, due to their mathematical straightforwardness, even though they do not correlate well with the visual human perception. Latest achievements in the area support that the use of convolutional neural networks (CNN) to assess perceptual visual quality is a clear trend. Results in other applications, like blur detection and de-raining, indicate the combination of information from different scales improves the CNN performance. However, to the best of our knowledge, the best way to embody multi-scale information in visual quality characterization is still an open issue. Thus, in this work, we investigate the influence of using multi-scale information to predict the perceptual image quality. Specifically, we propose a single-stream dense network that estimates a spatially-varying parameter of a logistic function used to map values of a objective visual quality metric to subjective visual quality scores through the reference image. The proposed method achieved a reduction of 36.37% and 69.45% for the number of parameters and floating-point operations per second, respectively, and its performance is compared with a competing state-of-the-art approach by using a public image database.
Acesso aberto (Open Access)
Análise e desempenho de um acoplador baseado em cristal fotônico dopado com érbio
(Universidade Federal do Pará, 2018-04-13) MARTINS, Elizete Sabino; COSTA, Marcos Benedito Caldas; http://lattes.cnpq.br/7636226766852440
In this dissertation, the concepts of photonic crystal were used to design an Erbium-doped photonic crystal coupler in order to verify the switching performance for the bar and cross states of the doped device in relation to the non-doped device. The Erbium-doped Photonic crystal coupler used the non-linear resonance caused by the excitation of the erbium ions located in the central row of a Photonic Crystal directional coupler. Such excitation causes the transition of the erbium ions from the ground state to the metastable state by amplifying the signal when the photons absorb the light emitted by the signal. The simulations occurred in the COMSOL Multiphysics® software, which uses the Finite Element Method (FEM). A comparative analysis was performed between a directional coupler of photon crystal doped with erbium and another non-doped. It was verified the switching performance of both from the normalized frequencies variation and it was verified that the doped coupler was able to operate in the barrra and cross states with the higher frequency spectrum.
Acesso aberto (Open Access)
Análise numérica de sensor de ressonância plasmônica de superfície baseado em grafeno na faixa de terahertz
(Universidade Federal do Pará, 2022-06-24) SILVA, Wêndria Cunha da; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work proposes a Terahertz plasmonic refraction index sensor based on Single-Layer Graphene operating as a refractometer in the Terahertz range. The configuration used is Kretschmann, where one of the variables that monitors the reflectivity is the chemical potential. The sensor was theoretically analyzed by the finite element method (FEM), using a bidimensional-based model structure. In it, the reflectivities and the field distributions were calculated for different parameters, such as sample thickness, operating frequency, incidence angle, chemical potential variation and electrical permittivity. Firstly, a study was made to determine the best operating frequency, the sensor’s angle of incidence and minimum sample thickness that the sample should have Subsequently, the numerical model was compared with the analytical model obtained through two literatures.. From the numerical results, parametric analyzes were performed to verify variations in sensitivity, full width at half maximum (FWHM) and resolution, all parameters of device quality. Numerical results are compared with theoretical concepts available in the literature and in recently published works.
Acesso aberto (Open Access)
Análises de atividades oscilatórias de EEG durante treinamento cognitivo e análise espectral de Holo-Hilbert
(Universidade Federal do Pará, 2022-07-19) SOUZA, Suzana Cescon de; GOMES, Bruno Duarte; http://lattes.cnpq.br/4932238030330851; PEREIRA JÚNIOR, Antonio; http://lattes.cnpq.br/3239362677711162
In this work we developed a protocol for the analysis of a cognitive training (TC), in order to raise the performance in bulldozer operators of Vale S.A. This research took part of the POAD (High performance operators' program) Innovation Project of the Vale Technological Institute ITV). The protocols of the TC were based in Neurofeedback (NFB), in order to develop the ability to self-regulate cerebral frequencies, based on electroencephalogram (EEG) analysis. In this research, the Holo-Hilbert Spectral Analysis (HHSA) for the study of amplitude modulation (AM) band frequency (FM) of the rhythms that compose the cerebral frequencies. The HHSA was based on empirical mode decomposition (EMD) in two layers. First the EEG signal has been decomposed in a series of intrinsic mode function in modulated frequency (IMFs) and then every IMF modulated in frequency have been decomposed in a sel of IMFs modulated in amplitude. thus. the present work explores the eflicicney of an TC bas s on modulated frequency and amplitude variations in EEG data obtained via NFB. The results show statistical relevance for the group-who went through the TC showing the effects of the application of TC, Moreover validate the efficacy of HHSA in the extraction of informative characteristics from the signals
Acesso aberto (Open Access)
Aprendizagem profunda aplicada a telecomunicações: classificação de modulação e controle de congestionamento
(Universidade Federal do Pará, 2019-05-31) NASCIMENTO, Ingrid Ariel Silva; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
The goal of this dissertation is to explore Deep Learning (DL) techniques applied to Telecommunications. DL has achieved success in areas such as computer vision and object detection and it is timely to investigate DL in communication problems. Then, two distinct problems are investigated. First, DL is applied to Automatic Modulation Classification (AMC) to detect the adopted modulation scheme automatically. AMC is important, for instance, in Cognitive Radios and military applications. In this dissertation, we discuss the benefits and drawbacks of using DL as an alternative for AMC and show its efficiency in comparison to other machine learning methods applied to AMC. Other DL application in communication is Congestion Control. The context is related to Fronthaul in C-RAN architecture using congestion control in order to attend the strict requirements of the 5G system. Specifically, DL is investigated in conjuction with Deep Reinforcement Learning (DRL) techniques. In this topic, this dissertation presents a framework for investigations in congestion control for Fronthaul, and the implementation of a model and environment using NS-3 and Gym API of the OpenAI group for simulation. The developed framework is validated with preliminary experiments that compare Deep Reinforcement Learning methods with traditional congestion control techniques, using as figu
Acesso aberto (Open Access)
Atenuação de oscilações magnetohidrodinâmicas em cuba de redução de alumínio usando estruturas periódica
(Universidade Federal do Pará, 2023-04-27) ANDERE, Thais Pascoal de Oliveira; OLIVEIRA, Rodrigo Melo e Silva de; http://lattes.cnpq.br/4768904697900863
Magnetohydrodynamic instability (MHD) in an aluminum reduction cell is due to the interactions between the conductive liquid currents and the magnetic field generated by very high currents flowing through current feeding circuit buses. Such phenomenon creates oscillations in this fluid, compromising the efficiency of the process aluminum reduction. The reduction cells consist, in their usual configuration, of a container with flat walls that accommodates the liquid. In this work, a new geometry is proposed for the container based on periodic structures, with the aim of to mitigate such oscillations. The analysis of oscillations of fluid in both configurations is made with a software developed in this work to numerically simulate the process in two dimensions. The numerical formulation employed is based on the finite-difference time-domain method to solve the Navier-Stokes equations (N-S) explicitly through the Chorin projections method. The volume and surface of the fluid are mapped using the MAC method, (marker and cell). The liquid is treated as incompressible and viscous, in addition to being electrically conductive. The accelerations caused by magnetic field and the electric currents are coupled to N-S by calculating the Lorentz Force. The results are analyzed and comparisons through the difference between the variation of the height of the conductive fluid in two scenarios, considering the flat bottom of the cell, current configuration, and by applying periodic structures at the bottom of the cell.
Acesso aberto (Open Access)
Avaliação de modos guiados em cabos de cobre para transmissão de dados em terabit por segundo
(Universidade Federal do Pará, 2020-03-27) SOUZA, Daynara Dias; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Copper-based technologies have used twisted pair and coaxial cables as transmission lines, exploring TEM (Transverse Electromagnetic) mode to transmit data. In twisted pair technology, to ensure higher rates, it is necessary to increase the band frequencies, which also implies an increase in attenuation over the TEM mode, with a consequent limit on the link data rate. Applications for the latest generation (5G) systems require rates in the order of tens Gbps (Gigabit per second), practically impossible to meet due to their attenuation, even considering short links. In this context, to give a new breath to twisted pair cables, it was proposed to use them as waveguides, i.e., exploring their higher-order modes for transmission, in a system called Terabit DSL (Digital Subscriber Line). Such modes are of the TE (Transverse Electric) or TM (Transverse Magnetic) types, and arise when the wavelengths, associated to the operating frequencies, are of the same order or smaller than the cross-sectional dimensions of the twisted pair cable. A similar fact applies to coaxial cables. When using these modes, it is estimated transmission rates in the order of Tbps (Terabit per second) to be achieved on twisted pair cables. This enables, for example, to have twisted pair and coaxial cables as viable alternatives to the transport network in the future 5G system. Such predictions assume that the model based on the guided mode on a single bare conducting wire, known as the Sommerfeld model, describes the attenuation of the higher-order guided modes in a twisted pair. However, this model does not adequately describe twisted pair cables, given that its physical structure is much more complex. Therefore, a more accurate study on the characteristics of the higher-order modes present in twisted pair and coaxial cables is needed, aiming at predictions in complete agreement with the real structure and electromagnetic propagation through them. This work investigates the propagation of several guided modes in twisted pair and coaxial cables, from numerical simulations in the HFSS (High Frequency Structure Simulator) software, considering real constructive characteristics. Based on the results obtained, the aggregate data rate of each cable used as a waveguide was determined. The results obtained indicate that data rates of more than 1.7 Tbps in just one twisted pair can be reached for 10 meters in length, up to 6.1 Tbps in one cable with four twisted pairs and approximately 5.6 Tbps in one coaxial cable.
Acesso aberto (Open Access)
Avaliação de técnicas de compressão de sinais Para o fronthaul
(Universidade Federal do Pará, 2019-11-27) BRITO, Flávio Mendes de; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
The growing data demand of mobile networks has motivated the creation and evolution of architectures aiming to supply such transfer requirements. To meet these requirements, a number of challenges need to be met, including data transfer at the link between the Base Station Unit (BBU) and the Remote Radio Head (RRH). Known as fronthaul, this link requires high speed information transfer and one method that allows to tranfer more data using the same rate is data compression. Therefore, this study aimed to evaluate different techniques used in fronthaul data compression. Initially, the efficiency of some quantizers such as the scalar quantizer (SQ), twodimensional vector (VQ) and the Trellis Coded Quantization (TCQ) was verified. The analysis consists of combining these quantizers with resampling, Block Scaling and Huffman coding. In both analyzes, it was found that the system using TCQ as quantizer obtained the best relationship between Error Vector Magnitude (EVM) and computational cost, offering an EVM lower than the scalar quantizer and a computational cost lower than the vector quantizer.
Acesso aberto (Open Access)
Avaliação técnico econômica de alternativas backhaul e fronthaul para arquiteturas de rádio centralizado em cenários 5G indoor
(Universidade Federal do Pará, 2019-05-28) FERNANDES, André Lucas Pinho; FARIAS, Fabrício de Souza; http://lattes.cnpq.br/1521079293982268; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The transport networks have a key role fifth in the support of demands of any telecommunications system. The fifth generation of mobile communication systems, the 5G, seeks to support a highly digitalized society, which has high operational demands. CRA (Centralized radio architecture) are emerging as a technically capable transport alternative to support 5G. Such solution divides the transport network into two sections, backhaul and fronthaul, which can be subdivided into several levels of links, whether optical, metallic or based on microwave. The viability of any technology to support the 5G does not only depend of technical requirements, whether traffic, coverage, availability or others, but also of the installation and operation economic aspects of the technologies. In this context, this work performs an technical and economic analysis for CRAs attending the indoor environment in the 5G context. To this end, a reference traffic forecast model is utilized and a set of models for dimensioning, predicting fault behavior and costs have been proposed and developed, which are generic and can be applied to different types of networks configurations or environments, whether indoor or outdoor, in a way that the two last mentioned models are based on a Markovian model solved by simulation. The analysis focused on CRAs installed in the indoor environment, where users spend most of their time, considering a high-density urban scenario, fronthaul with optical and metallic link levels or only metallic, as well PON (Passive Optical Network) based backhaul. The considered fronthaul alternatives were optical-metallic hybrid using 10 and 32 Gbps bidirectional transceivers, as well as all-metallic using the standard G.(mg)fast, making use or not of the phantom mode transmission, which is a technique to create virtual differential channels from real twisted pairs, resulting in increased capacity for metallic cables. The PON considered standards for the backhaul are 40 Gigabit PON and wavelength division multiplexing PON. The considered protection topologies against equipment failures for the PON backhaul are basic (unprotected), protected at the feeder level, protected at the feeder level and optical line terminal, and protected at the optical line terminal and at both levels feeder and distribution). The obtained results indicates that the best fronthaul alternative for CRA, supporting a average building of a high density urban scenario, is the all metallic using the standard G.(mg)fast with phantom mode transmission. In addition, they also indicate that PONs can be viable as backhaul 5G if protection schemes are used, and that in a dense urban setting, the 40 Gigabit PON standard is technically and economically the most viable for CRAs backhaul.