Programa de Pós-Graduação em Engenharia Elétrica - PPGEE/ITEC

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2314

O Programa de Pós-Graduação em Engenharia Elétrica (PPGEE) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará (UFPA) foi o primeiro e é considerado o melhor programa de pós-graduação em Engenharia Elétrica da Região Amazônica. As atividades acadêmicas regulares dos cursos de mestrado e doutorado são desenvolvidas principalmente nas Faculdades de Engenharia Elétrica e Engenharia de Computação, supervisionadas pela Coordenação do Programa de Pós-Graduação em Engenharia Elétrica (CPPGEE).

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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 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.
Desconhecido
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.
Desconhecido
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.
Desconhecido
Aspectos de avaliação de desempenho em redes ponto a ponto e ponto multiponto baseados em modelagem Markoviana e medições
(Universidade Federal do Pará, 2012-04-02) SOUZA, Lamartine Vilar de; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
This thesis presents a methodology for performance evaluation of broadband access networks. The performance evaluation of networks is a way to identify and analyze how certain features, such as different traffic types or forms of use, can influence the behavior of the network in focus. This way, we can predict how the network will behave in future situations. The methodology is composed of two approaches: an approach based on measurements and the other based on modeling using Markov processes. The networks analyzed cover the two basic types of access architecture: ADSL2+ (asymmetric digital subscriber line 2+) networks, which are wired networks that use twisted pair cables; FBWN (fixed broadband wireless network) networks, which are wireless networks based on IEEE 802.16 standard. The measurement approach is focused on network behaves against three situations: transmission of a generic traffic, impact of non-stationary noise in the system, and using network for the transmission of real-time multimedia traffic. The modeling approach, in its turn, is based on predicting the behavior of the network using mathematical models based on Markov processes. The results presented indicate the feasibility of applying this methodology as form of performance evaluation. The results also make possible the extension of this methodology to other types of broadband access networks such as fiber optic networks, microwave links, and VDSL/VDSL2 (Very-high-data-rate DSL) networks.
Desconhecido
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 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.
Acesso aberto (Open Access)
Caracterização e desenvolvimento de sensores ópticos de corrente elétrica para aplicações em linhas de alta tensão
(Universidade Federal do Pará, 2017-04-03) SANTA BRÍGIDA, Angela Costa; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
This thesis, titled "Characterization and development of electric sensors for electrical applications in high voltage lines" was developed in a PhD program in Electrical Engineering. Fix the devices and characterized the magneto-optical current sensors for measurement applications and protection in high power systems, namely, prism sensor and photonic glass fiber (PCF) sensor. Both are based on the Faraday effect, using a double quadrature polarimetric configuration. This work was then divided in two moments. In the first, a prism sensor, consisting of a portable sensor head for anchoring in the transmission line was developed, in Portugal, for an industrial application. In this case, no prism sensor prototype was used in a Schott SF57 glass prism 8cm in length with high Verdet constant and low birefringence. It has been incorporated into a Nylon casing suitable for fastening applications in the power line. The operation of the sensor is characterized and compared using Super Luminescent Diodes (SLD) as a source of 650, 830 and 1550 nm. Class 1 precision sensor for nominal currents of 900 ARMS or higher and classes 0,1 and 0,2 for nominal currents of 1,2 kARMS and 0,3 kARMS, respectively, and the possibility of detecting impulses in the network of 10 Μs. Second, another type of wrapping, the use of optical fibers as a transition element, using highly rotated fibers at 4, 6, 9, and 11 revolutions per second, developed by the group of the Laboratory of Special Fibers and Photonic Materials - LaFE, from the Institute of Physics Gleb Wataghin of UNICAMP, Brazil. In particular, these lines were tested as a whole on an electric conductor using three winding sizes of 6, 12 and 18 cm in diameters with different turns, with currents of up to 800 ARMS using an SLD source at 650 nm. Parameters, such as sensitivity and linearity of the sensor, were investigated. A symbolic analysis was also performed to quantitatively analyze the fiber sensitivity value with respect to the number of turns and with respect to the diameter of the support, there is no conclusion that there is a compromise between these two parameters in order to obtain a better response in the signal of sensor output.
Acesso aberto (Open Access)
Carimbó: canal de retorno com interatividade condicionada por mecanismo de sinalização contínua e provisionamento de banda orientado QoS
(Universidade Federal do Pará, 2006-12-15) COUTINHO, Mauro Margalho; FRANCÊS, Carlos Renato Lisboa; http://lattes.cnpq.br/7458287841862567; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
This doctoral thesis proposes a framework has controling and management the return network in Digital Television from four components: Digital Television Provider, Interactivity Terminal, Return Channel Provider, and Content Provider. Together, they interact based on a signaling mechanism that propagates QoS restrictions associated to the current interactive programming through the data carrousel system. The set of them also provide an admission control that investigates, periodically, the return channel status allowing or restricting the access according to the necessities of the interactive applications. Moreover, the system is so flexible that admit applications as in large scale as in small scale (local), thanks to the mobility of the service provider. An e-gov/e-health application was development in Xlet Java to evaluate the performance of the system. The performance analysis was proceeded using measurement and modeling techniques according to the system scale. In the last mille, some technologies of low cost and without periodically billing were tested such as wireless local area network. In large scale, the system was evaluated in different scenarios by means of simulation using the Network Simulator.
Acesso aberto (Open Access)
Cenário de redes de acesso para integração de redes ópticas e sem fio baseadas em sistemas de rádio sobre fibra
(Universidade Federal do Pará, 2016-01-15) OLIVEIRA, Rosinei de Sousa; TEIXEIRA, Antônio Luis Jesus; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The constant increasing demand for higher bandwidth services from subscribers has led to the integration of optical network infrastructure and wireless broadband access. Combining the capacity of optical fiber with the flexibility and mobility of wireless networks, a powerful system can be created to support data traffic volumes on demand. The radio over fiber system is the most used solution to integrate radio and fiber technologies. However, the analog links decrease linearly with the increasing length due to distortions from optical link. On the other hand, digitized radio transmission minimizes the physical impairments and can maintain its dynamic range independent from the fiber’s transmission length. Nevertheless, the optical link requires a high bandwidth due to the digitalization process, which from the implementation point of view represents one of the major challenges. This new context will change the network infrastructure and has forced operators to embrace solutions to improve the capacity of the system, mainly in radio access network (RAN). A new concept of RAN, called Centralized-RAN (C-RAN) is gaining great interest because this architecture improves the fixed/mobile convergence. In comparison with a classic architecture, this comes out with an innovative architecture where all complex functionalities are executed in the central office (CO), while the base station (BS) is responsible for executing less complex functions which bring reduced costs, improved performance and fixed/mobile convergence. Based on this information, this thesis proposal aims to investigate the radio over fiber scenarios as a solution to provide real access networks. In order to meet this goal, first we intending to investigate architectures by simulations, after we want replay the proposed followed by experimental demos in more realistic scenarios.
Acesso aberto (Open Access)
Classificação de regiões de desmatamento via imagens do satélite landsat no nordeste do Pará
(Universidade Federal do Pará, 2023-12-18) CANAVIEIRA, Luena Ossana; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Acesso aberto (Open Access)
A Comparison of dimensionality reduction and blind source separation techniques for video-based modal identification
(Universidade Federal do Pará, 2023-03-29) PAES, Thaisse Dias; SILVA, Moisés Felipe Mello da; http://lattes.cnpq.br/8154941342611201; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Understading the dynamic properties of a structural system is indispensable for a reliable study of the structural behavior. Video-based structural dynamics identification has been effectively used as a key method for modal analysis in recent years.With several different approaches, the ones based on the blind source separation strategy have received increased attention for identifying structural characteristics. Blind source separation addresses the problem of separating or extracting the original source waveforms from a sensor array. Although the literature addresses several techniques to perform the source separation, only one of them (named complexity pursuit) is often employed for video-based solutions. This work aims to explore other blind source separation algorithms to perform video-based modal analysis. In order to perform the modal decomposition, a set of blind source separation methods is combined with different dimensionality reduction techniques for full-field high-resolution structural dynamics from video. Specifically, Principal Component Analysis (PCA) and NonnegativeMatrix Factorization (NNMF), two dimensionality reduction techniques, are used for video compression along with six source separation algorithms, resulting in twelve different frameworks tested over a laboratory cantilever beam structure and a bench-scale model of a three-story building structure. The blind source separation techniques used are: Complexity Pursuit (CP), Idependent Component Analysis (ICA), Second Order Blind Identification (SOBI), Second Order Blind Identification with Robust Orthogonalization (SOBIRO), Equivariant Robust Idependent Component Analysis (ERICA) and Algorithm for Multiple Unknown Signals Extraction (AMUSE). The twelve techniques based on dimensionality reduction and blind source separation algorithms are evaluated here using as the criteria comparison their mode shape, modal coordinates and MAC values. The main goal is to provide a range of alternatives for the vide-based structural dynamics evaluation. For specific algorithms, the results indicate that both dimensionality reduction techniques and the blind source separation methods play a major role in the mode estimation performance. In the experiment utilizing the cantilever beam structure, all expected modals were successfully identified using the algorithms based on PCA-CP, PCA-ICA, PCA-SOBIRO, PCA-ERICA, NNMF-CP, NNMFSOBI, NNMF-SOBIRO and NNMF-ERICA. For the second scenario, using the model of a three-story building structure, the methods that correctly perfomed modal analysis are based on PCA-CP, PCA-SOBI, PCA-SOBIRO, PCA-ERICA, NNMF-CP and NNMF-SOBIRO. It is suggested that The effectiveness of combining NNMF and blind source separation methods for modal analysis may be contingent upon the complexity of the system under investigation.
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)
Compressão de sinais para fronthaul em arquitetura CRAN utilizando algoritmo evolutivo
(Universidade Federal do Pará, 2019-06-28) SOUZA, Vitória Alencar de; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Centralized radio access networks are present as a potential alternative for next generation of wireless networks, because they are able to provide high data rates and allow the reduction of structural and operational costs in the network. The centralized architecture implements the concept of fronthaul, and enables the challenge to increase the capacity of data transmission in hese links. In this way, the study of digital signal compression techniques presents itself as an alternative to reduce the cost of implementing centralized radio access networks.This work investigates the use of vector quantization methods in the compression of complex samples of baseband LTE signals. We propose the use of Genetic Algorithms in the training of sub-optimal dictionaries for the process of vector quantization in order to reduce the errors imposed in this process and consequent increase in fronthaul capacity. Results showed that the proposed compression algorithm allows reduction of fronthaul data rates associated with acceptable errors. It has been shown to be possible data rate compression factors of 5:4 times, with errors of approximately 4:4%, proving the effectiveness of codebook training process in LTE signals present in the downlink of centralized radio access networks.
Acesso aberto (Open Access)
Desenvolvimento de sensores baseados em fibra óptica afunilada para monitoramento ambiental
(Universidade Federal do Pará, 2015-02-06) SILVEIRA, Clenilson Rodrigues da; GIRALDI, Maria Thereza Miranda Rocco; http://lattes.cnpq.br/0270661833822671; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The monitoring of environmental parameters is important in preserving the environment. The development of technologically advanced systems for measuring physical parameters allows the early detection of harmful environmental factors. For example, refractive index and temperature measurement systems can detect thermal and chemical pollution in rivers water. Curvature or tilt measurement is important in predicting natural phenomena that may cause damage to human beings, such as landslides and earthquakes. This thesis investigates sensors based on tapered optical fiber for monitoring environmental parameters. The investigated technology is based on standard single-mode optical fiber with tapered section that makes use of the evanescent field to detect changes in the external environment, such as refractive index, temperature and curvature. This type of device is analyzed through numerical simulations and experimental measurements. The numerical modeling is performed using finite difference beam propagation method (FD-BPM). It is numerically and experimentally demonstrated that once tapered optical fiber Michelson interferometer is subjected to bending the sensitivity to refractive index change is enhanced in comparison with the not bent device. Experimental measurements indicate that this type of device has great potential as a temperature sensor. Numerical results, based on FD-BPM, indicate that it is possible to optimize the taper parameters in optical fiber to improve its sensitivity to bending in terms of transmitted power.
Acesso aberto (Open Access)
Desenvolvimento de sensores baseados em fibra óptica para monitoramento estrutural
(Universidade Federal do Pará, 2016-04-01) FERNANDES, Cindy Stella; GIRALDI, Maria Thereza Miranda Rocco; http://lattes.cnpq.br/0270661833822671; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The research and development of systems for measuring physical and mechanical parameters of structural health, allows the early detection of collapses, deterioration process and other natural and / or caused by man factors. In this case, real-time measurements of these parameters are crucial for identification, localization and quantification of damages, and also improve the maintenance and safety of such structures. Curvature and vibration measurements are important to structural monitoring due to their relationship with the dynamic responses of engineering structures. In this thesis, core diameter mismatch structures are proposed and experimentally investigated for curvature and vibration sensing. Among the analyzes, two settings exhibited improved performance, one approach uses a structure formed by splicing an uncoated short section of multimode fiber between two standard single mode fibers (SMS), combined to an optical fiber mirror at its end, and the other approach is made by the sandwich of one single mode fiber section between two short multimode fiber sections, spliced between two standard single mode fibers (SMSMS). The SMS device is analyzed through experimental measurements and numerical simulations. In the curvature analysis, the proposed SMS sensor generates destructive interference patterns whether it is bent, varying only the attenuation of the optical signal without wavelength shifts. Numerical modeling is performed using the finite difference beam propagation method by means of the BeamProp 9.0 software of Rsoft™ company. In the experimental vibration analysis, the SMSMS sensor is formed by two MMF sections that act as coupler and re-coupler of core-cladding modes, and the SMF section in the middle acts as the "arm" of interference. So the cladding modes that propagate in the SMF middle section become sensitive to the applied frequencies. The SMSMS vibration sensor proved to be suitable to monitor very low frequencies such as 0.1 Hz. The proposed sensors configurations present several interesting features, such as easy fabrication, low-cost, high-efficiency, and high sensitivity. Although the manufacturing process of the structures is not very precise, which affects its reproducibility, such sensors very useful in a wide range of applications, such as structural health monitoring.
Acesso aberto (Open Access)
Desenvolvimento de sistema para verificação metrológica de transformadores de corrente IN SITU em sistemas de alta tensão utilizando transdutor óptico
(Universidade Federal do Pará, 2013-08-21) COSTA, Marcelo Melo da; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
This work presents the development and field application of an on site metrological verification system for high voltage current transformers. It was developed aiming at portability aspects besides the metrological requisites, in such a way it can be easily transported and assembled without the need of power interruption as well as the use of complex and expensive transport and assemble logistics. The system uses an optical transducer as reference standard, whose sensor measures the primary current of current transformer under verification based on Faraday effect It is also composed by additional standard instruments that measure the transformer secondary current under verification, and compares it to the optical transducer output. High voltage laboratory tests as well as on site tests were performed. On site tests were perfomed in two power substations in Brazil, in the city of Belém, in order to assure the correct operation under high voltages and high currents conditions. Six 230 kV rated current transformers were verified. The site tests involved six 230 kV current transformers, under medium load system conditions, and achieved satisfatory results.
Acesso aberto (Open Access)
Designing cost-efficient transport solutions for fixed and mobile broadband access network
(Universidade Federal do Pará, 2016-03-03) FARIAS, Fabrício de Souza; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
This thesis undertakes a techno-economic evaluation of transport solutions for fixed and mobile broadband access. In the case of future mobile access networks, it is proposed to make use of backhaul architectures using fiber and microwave applied to Greenfield deployments and a copper-legacy backhaul infrastructure based on Brownfield migration, i.e. finding a way of using a legacy infrastructure to its full capacity. At the same time, protection deployments based on fiber-wireless schemes are recommended for future fixed broadband. The main contribution made by this thesis is to carry out a research investigation into the total investment cost of the broadband transport infrastructure. This will be determined by employing two sets of models to assess the capital and operational expenditures, (CAPEX and OPEX respectively), of mobile and fixed broadband access network operators. First, this involves a set of models for mobile broadband that are summarized in a general methodology that aims at providing: traffic forecasting, wireless deployment, mobile backhaul deployment and total cost assessment. It was found that, fiber-based backhaul through a Greenfield deployment is the most energy-efficient option. Furthermore, Brownfield reveals that copper-based backhaul can still play a key role if used up to its full capacity and sharply reduces the investment costs in infrastructure. Additionally, there is an examination of the main differences in cost and energy values between Greenfield and Brownfield. Finally, a methodology is employed for fixed broadband based on network dimensioning, failure costs and an assessment of the total cost of ownership. The models are used to assess five architectures that represent different protection schemes for fixed broadband. This research shows the economic benefits of using a hybrid protection scheme based on fiber-wireless architecture rather than fiber-based protection options and a sensitivity analysis is conducted to show that the extra CAPEX invested to protect the infrastructure might be recovered through the OPEX after a number of years. The results obtained in the thesis should be useful for network operators to plan both their fixed and mobile broadband access network infrastructure in the future.
Acesso aberto (Open Access)
Designing feasible deployment strategies for cell-free massive MIMO networks : assessing cost-effectiveness and reliability
(Universidade Federal do Pará, 2024-06-14) FERNANDES, André Lucas Pinho; MONTI, Paolo; http://lattes.cnpq.br/4220330196422554; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Cell-free Massive Multiple-Input Multiple-Output (mMIMO) networks are a promising solution for the Sixth Generation of mobile systems (6G) and beyond. These networks utilize multiple distributed antennas to transmit and receive signals coherently, under an apparently non-cellular communication paradigm that eliminates the traditional concept of cells in mobile networks. This shift poses significant deployment challenges, as conventional tools designed for cellular systems are inadequate for planning and evaluating cell-free mMIMO architectures. In this sense, the literature has been developing models specific to cell-free mMIMO that deal with system coordination, fronthaul signaling, required computational complexities of processing procedures, segmented fronthaul, transitioning from cellular network deployments, and integration to Open Radio Access Network (O-RAN) technologies. These advancements are instrumental in transforming cell-free mMIMO from a theoretical system to a practical application. Despite this, further study is needed to integrate existing models and develop practical evaluation tools to assess the feasibility of cell-free mMIMO and its enablers. This thesis addresses these gaps by proposing new tools to evaluate the feasibility of cell-free mMIMO networks regarding reliability and costs. The first tool focuses on evaluating the reliability of cell-free mMIMO. It is used to improve the understanding of possible failure impacts and to develop effective protection schemes for the fronthaul network of cell-free mMIMO networks. Results for an indoor office implementation with an area of 100 m2 and a Transmission-Reception Point (TRP) spacing of 20 m, demonstrate that cell-free systems with segmented fronthaul, i.e., with serial fronthaul connections between TRPs, require protection strategies. It is shown that interconnecting serial chains and partially duplicating serial chains (40% redundancy) are effective protection schemes. Finally, in the considered indoor scenarios, interconnection appears to be the most feasible alternative when the number of serial chains is higher than three. The second tool assesses the Total Cost of Ownership (TCO) of cell-free mMIMO and its enablers, considering essential aspects, like user demands, fronthaul bandwidth limitations, and hardware processing capacities. The tool is used to evaluate the costs of two functional splits from the literature that are equivalent to distributed and centralized processing architectures for cell-free mMIMO networks. Results for an ultra-dense urban scenario covering an area of 0.25 km2 with up to 800 TRPs, reveal that centralized processing is more feasible for most user demands, hardware configurations of TRP, and cost considerations. Despite this, distributed processing may be more feasible in limited cases of low demand (up to 50 Mbps per user) and under massive cost reductions for expenses related to TRPs deployment.
Acesso aberto (Open Access)
Determinação da função de transferência de enlaces metálicos a partir de medições de impedância de entrada
(Universidade Federal do Pará, 2012-04-02) RODRIGUES, Roberto Menezes; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The digital subscriber line (DSL) technology aims at exploiting the full potential of the telephone metallic lines on providing broadband access. On the other hand, the telephone lines may have distinct transmission capacities due to differences on their topologies. Therefore, it is important to measure the actual transmission capacity of each line before the DSL service deployment. This process is called line qualification. The determination of the transmission capacity of metallic lines requires previous determination of their transfer function. The existent qualification techniques determine the transfer function from the communication between equipments at the central office and the customer’s premises or indirectly, from knowledge about the topology of the line under test. Both processes are not in line with a pre-deployment scenario since they imply additional costs with the dispatching of technicians to the subscriber’s site, dependency of updated records about the telephone network (rarely available) or use of sophisticated line topology techniques. Therefore, the goal of this work is to propose a method for determining the transfer function of metallic lines with the following features: it does not need previous knowledge about the line topology, it uses information collected just at the central office (CO) and it does not require any human intervention at the subscriber’s site. Essentially, the general form of the proposed method analytically describes the transfer function of the line under test in function of its short and open-circuited input impedances, taken from the CO, and its asymmetry. Additionally, an algorithm that derives the short-circuited input impedance from the envelopes of the open-circuited one was developed. By applying this algorithm together with the general form of the proposed method, it is possible to determine the transfer function from just an open-circuited input impedance measurement and without any human intervention at the subscriber’s site. The proposed method was evaluated in two steps. The first step concerns the evaluation of the general form of the method. Specifically, the tests involve baseline comparison using simulated data for threeline topologies, application of the method to a bunch of simulated data generated from an arbitrary lines generator, and evaluation using measurements performed in laboratory for eight real test lines. The second step concerns the joint application of the general form of the method and the algorithm that estimates the short-circuited input impedance to measured data for two of the test lines reproduced in laboratory. The results for simulated data indicate that the general form of the proposed method is efficient, providing estimates well below the defined threshold (< 3 dB per DSL tone). For measurements, the general form of the method has estimated the transfer function of seven from the test lines with deviation per tone below 1.5 dB, but it failed for the line with two bridged-taps, being one very close to the subscriber’s site. Concerning the joint application of the general form of the proposed method and the algorithm that estimates the short-circuited input impedance, the transfer function estimations have been equivalent to those provided by the general form of the method, but with significant deviations in the beginning and in the end of the frequency band. These significant deviations are due to the current version of the envelope detector block of the algorithm that has limited performance, especially for lines with more than two serial sections.