Teses em Engenharia Elétrica (Doutorado) - PPGEE/ITEC

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2317

O Doutorado Acadêmico inicio-se em 1998 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 21

Acesso aberto (Open Access)
Análise de sensores plasmônicos baseados em Nano estruturas estratificadas utilizando o Método das imagens complexas discretas
(Universidade Federal do Pará, 2018-05-11) SOUZA, Nadson Welkson Pereira de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
In this thesis, the theoretical analysis of a surface plasmon resonance (SPR) sensor coupled to metallic nanoparticles is presented. The sensor is considered in the Surface Plasmon Coupled Emission (SPCE) configuration, where the metallic nanoparticles (or analytes) are modeled by equivalent dipoles located above the sensor. A complete set of Green’s dyadic functions for the electric field is estimated for planar, multilayer, and uniaxial media in a computationally efficient and convenient manner for applications using the Discrete Complex Imaging Method (DCIM) via the Generalized Pencil of Function Method (GPOF). The principle of complex path deformation in a two-level contour is employed to express an original integral as a sum of complex images. The results related to the surface plasmon resonance, reflection, near and far field of planar sensors are presented and it is described how these nanoparticles influence the ability to increase the near field strength and alter the sensitivity response of these optical sensors. In addition, for comparison purposes, some results are calculated by numerical and experimental methods. The results show suitable agreement, which proves that DCIM is an efficient and powerful theoretical method for analyzing SPR sensors in the SPCE configuration.
Acesso aberto (Open Access)
Análise e modelagem em larga escala para as frequências 8, 9, 10 e 11 ghz em ambientes indoor
(Universidade Federal do Pará, 2019-12-06) BATALHA, Iury da Silva; BARROS, Fabrício José Brito; http://lattes.cnpq.br/9758585938727609; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
Within the context of studies related to radiopropagation, this work presents a proposal for large-scale modeling of propagation loss for 8, 9, 10 and 11 GHz bands in relation to the number of walls, distance and polarization. Measurement campaigns were conducted in the Annex II corridor and in a teaching laboratory located at the Federal University of Pará. The measurement campaign was performed using VV and HH co-polarized directional horn antennas and VH cross polarization nantennas in Line of Sight (LoS) and Line of Sight (NLoS) conditions, the transmitter was fixed within the environment with 0 dBm transmission with VV and HH antenna array and 15 dBm for VH. Directional antennas for transmitter and receiver with 29.3∘ elevation and 29∘ azimuth were used for frequencies 8, 9, 10 and 11 GHz. The Minium Mean Square Error (MMSE) technique was applied to determine the values of the equation parameters as: PLE , XPD, HHPD, and OPLE. The proposed propagation loss model presented satisfactory results compared to the measured data presenting a low standard deviation. A point-to-point standard deviation analysis is also presented within the two environments for the studied frequencies. For the corridor the standard deviation values using polarized V-V antennas were 7, 7.5, 5.6 and 5 dB, and for cross-polarized V-H antennas were 5, 6.2, 2.3 and 3.5 dB for studies frequencies. For the laboratory the values of standard deviation for polarized V-V antennas were 7, 7, 6.5 and 7.3 dB and for polarized H-H antennas were 9.3, 6.1, 6.1 and 6 dB. The polarization loss factor (XPD) presented in the extension of the CIX model for the corridor present values of 19.3, 28.7, 21.3 and 14.3 for the frequencies of 8, 9, 10 and 11 GHz, respectively.
Acesso aberto (Open Access)
Aprovisionamento dinâmico de recursos em redes ópticas elásticas multiplexadas por divisão de espaço considerando limitações de camada física
(Universidade Federal do Pará, 2019-06-07) LOBATO, Fabricio Rossy de Lima; CARTAXO, Adolfo da Visitação Tregeira; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
In elastic optical networks (EONs) employing weakly-coupled single-mode multi-core fibers (MCF), inter-core crosstalk (XT) can affect significantly the network performance, particularly when the number of cores and the path length increase. Hence, from the network perspective, the impairment-aware (IA) routing, spectrum and core assignment (RSCA) problem is an important research challenge of MCF-EONs. In this thesis, we propose a dynamic provisioning methodology that solves independently the IA-RSCA problem taking impairments physical layer into account. To achieve the XT impact minimization, we decompose the IA-RSCA problem into two subproblems: the IA routing sub-problem and the IA spectrum and core assignment (IA-SCA) sub-problem. For the routing solution, a precomputation method based on the k-shortest path is used, and a physical layer impairment verification phase is performed taking the required optical signal to noise ratio into account. For the IA-SCA sub-problem, the novel XT-aware greedy algorithm is proposed to minimize the XT impact on the MCF-EONs performance as follows: for each new connection, the level of detected XT power of the new connection and interfering connections relative to the XT power threshold of each connection is minimized on the average over all those connections. This minimization is achieved by choosing the core and frequency slot of the new connection. In order to take the spectral overlapping extension of the new and interfering connections into account in the detected XT power, a novel frequency slot overlapping index is introduced. The performance of the proposed algorithm is evaluated through computer simulations. The results show that the total blocking probability and network average utilization achieved by the proposed algorithm are better than the ones obtained by core prioritization, random and first-fit strategies, for different scenarios of XT level and spectrum fragmentation.
Acesso aberto (Open Access)
Avaliação de técnica semi-supervisionada de análise de vetor comprimido (C2VA) em imagens de satélites para detecção de mudanças de uso e cobertura da terra
(Universidade Federal do Pará, 2017-12-15) SIRAVENHA, Ana Carolina Quintão; PELAES, Evaldo Gonçalves; http://lattes.cnpq.br/0255430734381362
Remote sensing image databases and Geographical Information System have the potential to act as accurate tools for environmental monitoring. Carajas Mountains are an important mineral deposit in Brazil and as environmental laws protect a great portion of this region, they have been at the core of conflicts involving human and nature interests. The biggest mining project in Brazil is active in this region (Carajas project) and this analysis aims at identifying the environmental impact caused directly or indirectly by this activity using state of the art methods. This study collects information of land-use and land-coverage from an area larger than 111, 000 km2 including five municipalities, aiming at observing the landscape intervention from a big scale perspective. Therefore, employing the resultant products of the multi-spectral approach called compressed change vector analysis, this work analyses both the environmental changes in five municipalities of the Carajas Mountains: Parauapebas, Canaa dos Carajas, Ourilandia do Norte, Sao Felix do Xingu and Tucuma. From the point of view of the applicability of the proposed tools, it was noticed that the combination of the compressed change vector analysis with the fuzzy clustering is sufficiently efficient for the detection and analysis of changes in land use and land coverage. The quantitative and qualitative evaluation metrics show good accuracy compared to the manually obtained reference images. The results show that in general the vegetative coverage was replaced by pasture lands, which in turn were replaced by urban occupations. The comparison with official statistics and by visual inspection indicate good accuracy of the present study in the estimation of vegetative cover. The presence of environmentally protected areas has prevented the increase of deforestation in the mountains, in which the observed change rates were at least 15% lower than non-protected regions.
Acesso aberto (Open Access)
Circuladores de grafeno de banda ultralarga para região THz
(Universidade Federal do Pará, 2019-06-07) SILVA, Samara Leandro Matos da; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
Non-reciprocal components are indispensable parts of many microwave and optical systems. In the future, THz communication systems will also require these components. Existing publications show that the bandwidth of graphene-based circulators in the THz region can be 10% to 20% with the use of rather complicated structures. The suggested circulators are formed by a graphene junction with concave pattern connected to the waveguides. Graphene is supported by SiO2/Si layers. The circulating behavior is based on the nonsymmetry of the graphene conductivity tensor that appears due to magnetization by a DC magnetic field normally applied to the plane of the graphene. We discuss the main parameters that define the bandwidth and its influence on it. Circulators have record bandwidth that is twice as high as those published. We have shown that the circulator Y can have the bandwidth of 42% in the frequency range (2.75 ÷ 4.2) THz, with the insulation better than −15 dB and the larger insertion losses that −2 dB, provided by the DC magnetic field polarization of 1.5 T and the chemical potential of 0.15 eV. For the two 4-port circulators we achieved a bandwidth of 44% for the same physical parameters.
Acesso aberto (Open Access)
Compressão de sinais em sistemas de rádio sobre fibra digital para redes fronthaul
(Universidade Federal do Pará, 2019-07-23) MATE, Dércio Manuel; TEIXEIRA, António Luis de Jesus; OLIVEIRA, Rosinei de Sousa; http://lattes.cnpq.br/3853897074036715; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The introduction of technologies such as Carrier Aggregation (CA), Massive Multiple Input Multiple Output (MIMO) and Coordinated Multipoint (CoMP), aiming to improve the performance of LTE and LTE-A systems, increases the challenge for deploying Mobile Fronthaul due to the network capacity limitation to support higher transmission rates. An approach to deal with Frontahul’s capacity limitation is data compression. Several techniques have been developed for signal compression in fronthaul, and most of these techniques compress the signal transmitted in baseband. In this work, a compression technique is developed for specific scenarios of Digital Radio-over-Fiber systems, transmitting the signal in intermediate frequency (IF). This technique uses the radio channel state information (CSI) to control signal compression in the fronthaul. The simulation results with the developed technique demonstrate its ability to reduce the data transmitted onthe network by 45.05%. In addition, this technique allows the transmission of 64 QAM modulated signals using a lower quantizer resolution, e.g., 4 bits per sample, maintaining the EVM below 3GPP recommended threshold (8%). Finally, the performance of the fronthaul network is evaluated experimentally in an optical link of 20-km, considering scenarios with and without signal compression.
Acesso aberto (Open Access)
Dispositivos não-recíprocos baseados em grafeno na região de THz
(Universidade Federal do Pará, 2019-02-28) CASTRO, Wagner Ormanes Palheta; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
Four new types of nonreciprocal graphene-based devices operating in the Terahertz region are suggested and theoretically analyzed in this work. They are two three-port circulators with Y and W geometries and two power dividers with different geometries. The cross section of the components has a three-layer structure, composed of graphene, silica and silicon. The planes of the figures of these components consist of a circular resonator of graphene and waveguides connected to it. The graphene resonator is magnetized normally of its plane by an external DC magnetic field, and the physical principle of operation of the devices is based on the dipole resonance of the magnetized graphene resonator. Using the Magnetic Group Theory, we analyze the scattering matrices of the symmetrical components of the devices. In addition, for the analysis of the circulators, the Analytical Temporal Coupled Mode Theory was also used. Numerical simulations were performed by a full wave computational program and the calculations demonstrate isolation levels better than -15 dB for both the circulators and the dividers. The Y-circulator has insertion losses around - 2.6 dB, bandwidth of 7.4% at the center frequency of 5.38 THz, whereas the circulator W showed insertion losses of - 2 dB, bandwidth of 4.5% at the center frequency of 7.5 THz. The DC bending magnetic field in the two cases was 0.45 T and 0.56 T, respectively. The power dividers have shown to posses the division of the signal between the two output ports of -4.4 dB with in the frequency band of 4.5% and 3.4% with magnetic filed of 0,8 T. The influence of geometric and physical parameters on the characteristics of the circulators is discussed. The frequency bands of the devices can be controlled dynamically by changing bias voltage applied between the graphene layer and the substrate.
Acesso aberto (Open Access)
Efeitos de Faraday e Kerr em estruturas periódicas metálicas: Grafeno na faixa de THz e Ouro-Dielétrico-Bi:YIG na faixa do infravermelho
(Universidade Federal do Pará, 2018-10-05) SANTOS, Carlos Rafael Marques dos; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
Photonics is a research field whose purpose lies in the use of light (photons), rather than electrons (electronics) in the realization of certain functions such as storage, transfer and processing of signals. In this context, it opens the possibility of development and production of devices whose storage capacity surpasses those of electronic devices. To do this, it is necessary to control the photons similarly, to what is done in electronics with the electrons. The control of radiation, in the context of photonics, can be realized through magneto-optical effects, such as the Faraday and Kerr effects. The Faraday effect is used as the basis of operation of devices such as optical isolators, current sensors and others. In turn, the Kerr effect is the basis of the operation of data storage devices (optical magnetic memory). In the present work, magneto-optical effects of Faraday and Kerr, as well as the transmission of electromagnetic radiation are studied in the regions of terahertz and infrared. In the frequency range that corresponds to the THz, the Faraday effect, the Kerr effect and the radiation transmittance are analyzed in periodic structures of graphene with different geometries. The structures analyzed in this work can present RF, for weak magnetic fields (B =1 T, for example), greater than 3_ depending on the choice of geometry that can be circles, squares, squares with small cuts in the corners and ribbons. Faraday rotation in these systems can be explained by a simple circuit model where the introduction of periodicity in the graphene promotes the increase of the system impedance and consequently changes the magneto-optical properties of the system, improving the rotation of Faraday at high frequencies (larger than 8 THz) still with magnetic field values taken as weak. This characteristic can not be obtained in a uniform sheet of graphene, since it is possible to obtain a strong rotation of Faraday at high frequencies with strong magnetic fields (10 T, for example). Additionally, for the three periodic structures it was calculated the Kerr rotation that can reach the value 3.96_ depending on the geometry chosen. For all cases, the maximum frequency of Faraday and Kerr rotations occur for frequencies greater than 7 THz. These results are better than results already published. In the infrared region are studies the effects of Faraday, Kerr, as well as extraordinary optical transmission in a plasmonic hybrid structure composed of four layers. For this, the Faraday rotation is of 7_ and 0.25 of of transmittance For wavelength 945 nm. Additionally, the Kerr effect can reach 23_. These results are better than results already published. In the proposed structure, the improvement of Faraday’s rotation is due to the increase of the Q factor of the resonances in the magneto-optical material layer.
Acesso aberto (Open Access)
Estados ligados de Majorana em nanodispositivo com ponto quântico acoplado à cadeia de átomos em zigue zague sobre supercondutor topológico.
(Universidade Federal do Pará, 2018-10-11) BEIRÃO, Antonio Thiago Madeira; SILVA, Shirsley Joany dos Santos da; http://lattes.cnpq.br/6060351208361634; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The research in condensed matter physics with insulators and superconductors topological has contributed greatly to the characterization of the surface properties and modes zero in nanowires. We investigate theoretically, through the recursive Green’s function approach, the electron transport through the T-shaped quantum dot (PQ) with a single level and spinless, connected to a zigue zague chain and coupled to a p-wave superconductor. This model is an extension of the Kitaev chain for a network triangular of finite-size with for three, four, and five sites. We find that the Majorana zero modes can be tuned through the coupling parameters of the device and the linear conductance show both the Majorana Bound States (MBS) in topological phase and in the general topological phase maximally robust. This more realistic model allows the detection of MBS through of the control of the parameters governing the electronic tunneling and can be helpful for relevant experiments. Keywords: Majorana Fermions, recursive Green’s function approach, Kitaev chain, class of electronic nanodevices, Quantum Dot, T-shaped, Qubit, Majorana Bound States (MBS).
Acesso aberto (Open Access)
Estruturas photonic band gap em antena de microfita com aplicações em microondas e terahertz
(Universidade Federal do Pará, 2019-08-16) OLIVEIRA, Jorge Everaldo de; COSTA, Marcos Benedito Caldas; http://lattes.cnpq.br/7636226766852440
In this work we are analyzing the simulations of two microstrip antennas. The first is an antenna using the ceramic material Bismuth Niobate (BiNbO4) doped with Vanadium Pentoxide (V2O5) on the substrate. The antenna patch was designed with indented power line to facilitate matching of impedances and the substrate with air holes was placed just below the patch to further decrease the losses. The second is a nano-antenne with Graphene Patch in the Terahertz range and PBG (Photonic Band Gap) substrate with triangular mesh, and holes in the following height configurations h1, h2 and h3. At time h1 the substrate is fully drilled, while at heights h2 the holes will be made top to bottom of the substrate and the height h3 is the antenna with substrate drilled from the bottom up to the middle of the substrate. Therefore three antennas are created in these geometries using a triangular hole network. The arrangement of the holes in the dielectric substrate constitute the PBG structure, to increase the performance and efficiency of these antennas, extinguishing surface waves in the substrate of microstrip antennas. The adopted geometry also improves antenna parameters such as efficiency and bandwidth. The commercial software HFSS and CST were used for the simulations of the antennas. After the numerical simulation steps the results of the parameters of these devices were obtained. The first antenna (periodic lattice with ceramic substrate) obtained a return loss of -36.21 dB, at a resonance frequency of 10,26 GHz, with a bandwidth of 2.18 GHz. In the simulations of the antennas of microstrip with Patch of graphene the antenna h3 obtained double transmission band with chemical potential of graphene of 0,3 eV.
Acesso aberto (Open Access)
Mapeamento de bits para adaptação rápida a variações de canal de sistemas QAM codificados com LDPC
(Universidade Federal do Pará, 2017-09-29) CORRÊA, Fernanda Regina Smith Neves; UCHÔA-FILHO, Bartolomeu Ferreira; http://lattes.cnpq.br/7752341440632617; PELAES, Evaldo Gonçalves; http://lattes.cnpq.br/0255430734381362
Low-Density parity-check (LDPC) codes are being adopted as the error correction strategy in di erent system standards, such as the G.hn (home networking standard) and the IEEE 802.11n (wireless local standard). In these LDPC-coded quadrature amplitude modulation (QAM) systems, mapping the LDPC coded bits properly to the di erent sub-channels considering the fact that sub-channels have di erent qualities ensures an improved overall system performance. Accordingly, this thesis presents a new bit mapping technique based on the assumption that bits transmitted in \good" sub-channels, help bits transmitted in \bad" sub-channels. This can be made possible through some restrictions to be imposed on the associated Tanner graph, akin to Root-LDPC codes. An optimization of the root-like bit mapping through extrinsic information transfer (EXIT) charts analysis is also presented. We show that this mapping has the advantage of a reduced optimization search space when applied to single-carrier based systems. Moreover, in situations where the search space is not só reduced, such as in orthogonal frequency division multiplexing (OFDM)-based applications, we arrive at a rule of thumb associated with the bit mapping constraints that practically eliminates the need for an optimization. Finally, a study of the impact of the level of reliability imbalance across the sub-channels on the performance of the root-like bit mapping is presented. Simulation results show that the new bit mapping strategy improves performance, and that in the presence of channel variations, the system can, adaptively, apply a new bit mapping without the need of a complex optimization, which can be very useful in practical systems.
Acesso aberto (Open Access)
Uma metodologia temporal para avaliação do desempenho de códigos concatenados em sistemas OFDM para transmissão de vídeo 4K-UHD
(Universidade Federal do Pará, 2024-08-16) COSTA, Thiago de Araújo; CASTRO, Bruno Souza Lyra; http://lattes.cnpq.br/1897829604434609; BARROS, Fabrício José Brito; http://lattes.cnpq.br/9758585938727609
The communication channel is a critical part of the process of information degradation. In the 4K ultra-resolution video transmission domain, the communication channel is a crucial part where information degradation occurs, inevitably leading to errors during reception. To enhance the transmission process in terms of fidelity, advanced technologies such as digital video broadcasting terrestrial (DVB-T) and its evolutionary successor, digital video broadcasting terrestrial second generation (DVB-T2), are utilized to mitigate the effects of data transmission errors. In the transition, a notable change is the replacement of the concatenated channel coding pairs. Within this scenario, this research presents an innovative methodology for the temporal analysis of 4K ultraresolution video quality under the influence of additive white Gaussian noise (AWGN) and Rayleigh channels. This analytical endeavor is facilitated through the application of concatenated coding schemes, specifically, the Bose-Chaudhuri-Hocquenghem concatenated low-density parity check (BCH-LDPC) and Reed-Solomon concatenated convolutional (RS-CONV) coders. A more comprehensive understanding of video quality can be attained by considering its temporal variations, a crucial aspect of the ongoing evolution of technological paradigms. In this study, the Structural Similarity Index (SSIM) serves as the main metric for quality assessment during simulations. Furthermore, the simulated Peak Signal-to-Noise Ratio (PSNR) values validate these findings, exhibiting consistent alignment with the SSIM-based evaluations. Additionally, the performance of the BCH-LDPC significantly outperforms that of RSCONV under the 64-QAM modulation scheme, yielding superior video quality levels that approximate or surpass those achieved by RS-CONV under QPSK (Quadrature Phase Shift Keying) modulation, leading to an increase in spectral efficiency. This enhancement is evidenced by SSIM gains exceeding 78% on average. The computation of average gains between distinct technologies in video quality analysis furnishes a robust and comprehensive evaluation framework, empowering stakeholders to make informed decisions within this domain.
Acesso aberto (Open Access)
Metodologias de discretização espacial sem malha baseadas nos potenciais de Coulomb e Lennard-Jones para o método radial de interpolação por pontos (RPIM) aplicadas para solução numérica das equações de Maxwell
(Universidade Federal do Pará, 2017-12-04) SOUSA, Washington César Braga de; RABELO, Wilson Ricardo Matos; http://lattes.cnpq.br/7978676206209168; OLIVEIRA, Rodrigo Melo e Silva de; http://lattes.cnpq.br/4768904697900863
In this thesis, three new particle interaction methods based on the Coulomb's and Lennard- Jones' potentials have been developed (and computationally implemented), aiming to generate meshless spatial discretization which can be used to the Radial Point Interpolation Method (RPIM) for solving partial di erential equations. These new methods, called Coulomb Law Discretization Method (CLDM), Electric Charge Gaussian Gradation Method (ECGGM) e Lennard-Jones Discretization Method (LJDM),employ adapted versions of Coulomb's and Lennard-Jones' vector forces equations for obtaining a balanced distribution of nodes in space (equilibrium state), in order to achieve high discretization quality of space and complex structures. For this aim, a new quality metrics is introduced. This doctoral thesis is presented as an aggregation of three scienti c papers, which present respectively the methods: CLDM, ECGGM and LJDM. The RPIM and the uniaxial perfectly matched layers (UPML) are used for solving Maxwell's equations in time domain for 2D (TMz mode) and 3D problems. The CLDM, ECGGM and LJDM methods (each in conjunction with the RPIM method) are applied to electromagnetic scattering problems, based on circular, elliptic and triangular metal cylinders (2D case). The LJDM / RPIM method is applied to the 3D case. The obtained results are in accordance with analytical solutions.
Acesso aberto (Open Access)
Modelagem da perda de qualidade de videos H.264 em redes sem fio considerando perdas de PSNR e de frames
(Universidade Federal do Pará, 2019-08-16) CARMONA, João Victor Costa; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382; BARROS, Fabrício José Brito; http://lattes.cnpq.br/9758585938727609
Multimedia applications have been growing in recent years; new consumptions like online games, video conference, video on demand and IP telephony are some of these. However, there is a greater prominence in the search related to videos and streaming, currently in high resolutions and mostly traffic over wireless networks, mainly due to the proliferation of mobile devices and significant increase of access networks, which make it more comfortable. Providing this information is easy. Thus, as an immediate consequence of this type of flow, there is a need for investments in techniques and mechanisms that provide the end user with the desired quality and satisfaction in the face of high definition content. This work aims to perform the modeling of video quality loss by analyzing their performance in various resolutions, specifically standards in HD and UHD, at 720p, 1080p and 2160p. In this sense, applying a correlation investigation between the metrics extracted from the videos, using Pearson’s correlation coefficient, and fundamentals of the area in question. Also proposing equations for quality loss modeling, based on analysis of metrics associated with packet loss, in which at the end of the study and according to notes made throughout the text, we used for the general modeling equation, the parameters of Loss of PSNR and Loss of Total Frames. The result obtained shows maximum values of RMSE and Standard Deviation of 0.793 dB and 0.810 dB, respectively, making the developed model very good for the tested video set and its resolutions.
Acesso aberto (Open Access)
Modelling and mitigation of alien crosstalk for DSL systems
(Universidade Federal do Pará, 2017-12-11) GOMES, Diego de Azevedo; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284; PELAES, Evaldo Gonçalves; http://lattes.cnpq.br/0255430734381362
G.fast is the most recent ITU-T standard for DSL transmission, which targets copper topologies with short distances and adopts a bandwidth of 106 MHz extensible to 212 MHz. In several situations, G.fast systems will be composed by or coexist with uncoordinated (or alien) lines, which are sources of strong crosstalk, because these lines are not part of the vectored group. This document presents a formulation to explain the performance of the alien crosstalk mitigation methods according to the number of alien lines in a certain environment, the mechanism that de nes the interference correlation of it and an alien crosstalk mitigation method for downstream DSL transmission impaired by multiple interferers called AMMIS. Simulation results show that alien crosstalk mitigation methods found in the literature can indeed improve the performance of G.fast systems, but only under speci c conditions. We have contrasted these situations and we provide guidelines about the feasibility of the crosstalk mitigation techniques in scenarios with distinct number of alien lines. Additionally, the AMMIS shows promising results in relation to the bit rate when compared with literature methods in scenarios with a large number of interferers, with the additional advantage of allows power savings. As support for the simulations, we also present a set of alien crosstalk measurements.
Acesso aberto (Open Access)
Modelo para representação de ambientes 3D utilizando composição de modos do método FDTD-2D
(Universidade Federal do Pará, 2017-05-26) LIMA, Bruno Wallacy Martins; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
In this work, we use the two and three-dimensional versions of the finite-difference time-domain method, FDTD, for simulating the propagation of the electromagnetic waves in an indoor environment. First, the validity of the FDTD-3D method is proven by comparing the values of the power delay profile obtained via a measurement campaign carried out in the indoor environment. The losses expressed with the FDTD-3D method were used to propose corrections to the FDTD-2D results by taking into account the propagation in the free space and the propagation in the indoor environment. The advantages of the FDTD-2D method with corrected transient responses are reduced processing time and memory requirements when compared to other numerical methods. It is possible with the FDTD-2D with corrected signals to simulate wave propagation for large and complex environments and to develop simulation software for personal computers and mobile devices.
Acesso aberto (Open Access)
Nanoantena Óptica Plasmônica Dipolo-Espira de Banda Larga
(Universidade Federal do Pará, 2018-10-11) SOUZA, Janilson Leão de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
Acesso aberto (Open Access)
Network slice admission using reinforcement learning and information-centric networking for mobile networks
(Universidade Federal do Pará, 2019-08-21) BATISTA, Pedro dos Santos; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
The evolution of the current most popular mobile network (4G), the so-called 5G, is targeting an increased traffic load at a lower cost. Thus, optimization of the delivery network plays an essential role at 5G; another aspect of the evolution is that 5G has the ambition to be highly customized, e.g., reliable enough to be used in industrial automation and cheap enough to be used for mobile broadband services. In this context, this thesis assesses two aspects of 5G: the first is to use information-centric networking (ICN) to improve the efficiency of multimedia delivery in mobile broadband services; and the second is the application of a reinforcement learning strategy as an enabler for the highly configurable network, which could pose a challenge to be understood and configured manually. ICN aims at circumventing several issues of current internet protocol, among them, achieving a more efficient multimedia distribution. Given the significant growth rate of video transmission over mobile networks, it is sensible to consider how mobile networks can leverage ICN. There is a substantial body of work considering ICN for fixed networks and also for the core of mobile networks. Less attention has been dedicated to ICN on the radio access network (RAN) or ICN-RAN, which has currently a user plane based on many connection-oriented protocols. To fully benefit from ICN, mobile networks must enable it on the RAN, not only on the core. This work details an ICN deployment on the RAN of the fourth and fifth generation of mobile networks and also presents a testbed that enables proofs of concept of this ICN-RAN using 4G. The results indicate, for example, that evolving ICN features can be tested with currently available tools, but the lack of hardware accelerators and optimized code limit the bit rate that can be achieved in real-time processing. In the context of network customization, the most prominent enablers are the so-called network slices. Slices can be understood as a part of the network that is customized to deliver certain services. The service requirements are imposed by the tenant, which acquire slices from an infrastructure provider. The 5G infrastructure provider must optimize the infrastructure resource utilization, usually admitting as many slices as possible. However, infrastructure resources are finite and admitting all the slices could increase the probability of service level agreement violation. This thesis investigates the application of reinforcement learning agents that learn how to increase the infrastructure provider revenue by intelligently admitting network slices that bring the most revenue to the system. We present a neural networks-driven agent for network slice admission that learns the characteristics of the slices deployed by the tenants from their resource requirements profile and balances the benefits of slice admission against orchestration and resource management costs.
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.
Acesso aberto (Open Access)
Projeto e síntese de superfície seletiva de frequências para o padrão IEEE 802.15.3C via técnica de otimização híbrida multiobjetivo de alta precisão
(Universidade Federal do Pará, 2019-12-19) MOTA, Raimundo José Santos; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
Artficial Neural Networks (ANN) are inspired by the structure and functional aspects in biological neural networks. They are trained through mechanisms obtained from the physical properties of the processes involved, for example, electromagnetic waves. From the knowledge acquired through that experience and learning, they may be able to provide solutions for predicting users behavior and providing, within a region of interest, accurate strategy data for projects and sizing. Those who criticized the application of ANN acquired by nature-inspired algorithms, argued that the problems to be faced were usually without complexities, although the conventional methods that were proposed to solve these same problems were not eficient. Some spurious successes have occurred in certain well-behaved environments, but without_exibility when encountering diverse constraints. Adding to these developments, there is the evolutionary openness of computational tools, which has given extraordinary support for deepening techniques to solve and optimize previously unthought problems. In many optimization issues, the quality of a solution is defined by its performance against several conficting goals. Such coficting objectives cannot be signi_cantly reduced to a single value, for example using a weighted sum or other methodology, but must be considered independently of each other. To achieve accurate solutions with reduced computational costs and shorter processing times, we present the Multi-Objective Evolutionary Algorithms (MOEA), as well as Bioinspired Computation (BIC). Combining the advantages of the classical algorithms, the Metaheuristic Algorithms emerged irreversibly. In many optimization problems, the quality of a solution is defined by its performance in relation to several, coficting objectives. Such conficting goals cannot be sensibly reduced to a single value using a weighted sum or another aggregate function, but rather they must be considered independently from each other. Multi-Objective Evolutionary Algorithms (MOEAs) are a natural answer of this kind of evolution. In this work is presented a hybrid bioinspired optimization technique that associates a General Regression Neural Network _ GRNN with the Multi-Objective Bat Algorithm _ MOBA, for the design and synthesis of the Frequency Selective Surfaces _ FSS, aiming its application in data communication systems by difusion of millimeter waves, speci_cally, in the IEEE 802:15:3c standard. The designed device consists of planar arrangements of metallizations (patches), diamond-shaped, arranged over a RO4003 substrate. The FSS proposed in this study presents an operation with ultra-wide band characteristics, its patch designed to cover the range of 40:0 GHz at 70:0 GHz, i.e., 30:0 GHz bandwidth and 60:0 GHz resonance. The upper and lower cuto_ frequencies, referring to the transmission coe_cients scattering matrix (dB), were obtained at the cuto_ threshold at -10dB, to control the bandwidth of the device.