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- Insights on Spectrum Sharing in Heterogeneous Networks with Small CellsPublication . Silva, Bruno C.; Sousa, Sofia C.; Teixeira, Emanuel; Velez, FernandoThis work explores the viability of 5G New Radio spectrum sharing in Ultra High Frequency (UHF), Super High Frequency (SHF) and millimetre wavebands(mmWaves) in outdoor environments. In the mmWaves the linear cellular topology is considered while in the UHF/SHF bands cells with hexagonal shape are assumed. Performance evaluation includes the study of the behaviour of PHY and supported throughput for 2.6, 3.5, 28, 38, 60 and 73 GHz. While the two-slope model is considered for the 2.6 and 3.5 GHz frequency bands, the modified Friis propagation model, with shadow fading, and different values for the standard deviation, is the considered in the millimeter wavebands. With sharing, lower system capacity is supported. We clearly observe that, for coverage distances up to circa 100 m, the supported throughput is higher at the millimetre wavebands, mainly due to the reduction that characterizes the application of the two-slope propagation model at the UHF/SHF bands.
- Service Quality of the Urban Microcellular Scenario in the Sub-6 GHz Frequency BandsPublication . Paulo, Rui R.; Teixeira, Emanuel; Velez, Fernando J.This paper compares the service quality between 4G and 5G New Radio (NR) among different sub-6 GHz frequency bands in an urban micro-cellular outdoor setting. An updated version of LTE-Sim is considered to obtain the exponential effective signal-to-interference-plus-noise ratio in 4G while determining the modulation and coding scheme. System capacity is obtained by considering a video application at 3.1 Mb/s and the proportional fair (PF) scheduler while comparing 4G and 5G NR through system-level simulations (the 5G-air-simulator is considered for 5G NR). The modified largest weighted delay first (MLWDF) scheduler is compared with the PF, though only in 4G. Optimal system performance is reached both in 4G and 5G NR for cell radii longer than two times the breakpoint distance (or beyond), which are preferable compared to the shortest values for the cell radius. We have learned that the packet loss ratio (PLR) is higher for the cell radii, R, shorter than breakpoint distance, d′ BP. For d′BP ≤ R ≤ 1000 m, the PLR first decreases and then increases. For a target PLR < 2%, in 4G, the highest maximum average goodput is obtained with the M-LWDF scheduler (10-25% increase). This maximum occurs at the 2.6 GHz and 3.5 GHz frequency bands for 300 ≤ R ≤ 500 m, while at 5.62 GHz the highest goodput occurs for the longest Rs. With 5G NR and the PF, the maximum average goodput increases, in our simulations, from ≈ 14.1 (in 4G) to 26.1 Mb/s (20 MHz bandwidth).
- Cost/Revenue Trade-Off of Small Cell Networks in the Millimetre WavebandsPublication . Teixeira, Emanuel; Velez, FernandoIn this work, we identify and discuss the potentialities of mobile cellular communications in the millimetre wavebands, showing that very high bit/data rates can be supported in small cells with short-range coverage. We study the behaviour of the carrier-to-noise-plus-interference ratio with the coverage distance (and the actual distance from users to the eNBs) in actual environments and the respective analysis of the impact in cellular planning and optimization process. We assess the equivalent supported throughput within cells with reuse pattern K=2, assuming, in this preliminary phase, the use of LTE. In terms of cell coverage and the computation of interference, LoS propagation models have been considered at the 28, 38, 60 and 73 GHz frequency bands. From these analytical computations, we conclude that, at 28 GHz, although lower system capacity is achieved for very short coverage distances of the order of 25 m, in comparison to the 73 GHz frequency band, there is an enhancement in the supported throughput for longer coverage ranges, and it is clearly more favourable for the lowest frequency band. Owing to the additional attenuation of oxygen, the 60 GHz frequency band is more challenging, as the lowest values of the cochannel interference due to the additional oxygen attenuation originate higher values for the supported throughput, even for lower values of the reuse pattern. Based on these results, costs and revenues are studied. Revenues are proportional to the supported throughput and the profit is generally a declining function with cell radii. The highest profit corresponds to the shortest cell radii, up to 80 m, and the best results occur for the 28 GHz band.
- Fractal Patch Antenna based on Crystal Photonic applied to Intelligent Transportation Systems in the 40 GHz Millimeter WavebandPublication . Bagheri, Nila; Khan, Bahram; Teixeira, Emanuel; Velez, Fernando J.5G (and beyond) has very high bandwidth, short latency, better quality of service, and the right amount of capacity. Technological breakthroughs in mobile communication systems user equipments operating in the millimeter wavebands imply a high gain to compensate the effect of path loss. In this work, a novel photonic crystal-based microstrip patch antenna array with high gain is designed to be used in the next generation intelligent transportation ssytems, e.g., V2X, and other exciting applications. The Photonic Band Gap (PBG) structure and Finite Element Method were considered. By using the High Frequency Structure Simulation (HFSS) software, a fractal microstrip patch antenna operating in the U-band of the electromagnetic spectrum is conceived and modeled on a two-dimensional photonic crystal. The use of the PBG structure improves the antenna’s gain and bandwidth, while the antenna’s fractal form decreases its size and improves its input impedance. The operational frequency range is 41.72-45.12 GHz with a resonant band centered at 43.26 GHz. The proposed antenna is comprised of a 0.45 mm thick copper ground plane, a 0.9 mm thick FR-4 epoxy substrate with a relative transmittance of 4.4, and a 0.45 mm thick copper antenna patch. The achieved frequency band gain is 8.95 dBi.
- Multi-Band Resonant Photonic Crystal Antenna for 5G ApplicationsPublication . Teixeira, Emanuel; Teixeira, Emanuel; Peha, Jon; Velez, Fernando J.Extended reality (XR) is bridging the gap between virtual and real-world interactions enabling users to interact in realistic virtual worlds, removing physical obstacles, and establishing shared areas that promote greater comprehension and teamwork. The growing demand for high-frequency 5G communication systems supporting these new applications motivates the need of compact and efficient antennas capable of operating at millimeter-wave frequency bands. This work explores how the use of photonic crystals leverages the properties of a multi-band antenna operating within the 27.81 GHz and 41.93 GHz resonant bands. The High-Frequency Structure Simulation (HFSS) software is utilized in this paper to outline a comprehensive design and modeling approach for the proposed microstrip patch antenna.The design process involves optimizing the geometry and periodicity of the photonic crystal structure to obtain resonant modes at the desired frequency bands by exploiting its bandgap properties, whilst enabling high quality resonances within the targeted frequency bands. The electromagnetic simulations and numerical analysis results demonstrate that the designed multiband photonic crystals-based antenna achieves a gain of 9.61 dBi. The resonant modes exhibit high quality factors, resulting in improved radiation efficiency. The proposed photonic crystalbased antenna compact size, high gain, and multiple resonant bands make it suitable for a wide range of applications, including next-generation wireless communication systems supporting XR, radar systems, or satellite communications in the upper frequency bands.
- Determinação de parâmetros em operadores para segmentação de nódulos mamários com o auxílio de Algoritmos GenéticosPublication . Teixeira, Emanuel José Soares Bordalo; Souza, José António Menezes Felippe deO cancro é uma das causas de morte mais frequente em todo o mudo e o cancro da mama é o mais comum em mulheres. Logo, é de extrema importância a deteção atempada, pois o diagnóstico precoce e o tratamento do cancro mamário aumentam significativamente as probabilidades de tratamento bem-sucedido. O exame da mama através de imagens por ultrassom (US) é o principal coadjuvante da mamografia, tornando-se deste modo um exame ainda mais importante, complementado por sistemas CAD, detetando e classificando nódulos mamários. Na presente dissertação foi desenvolvida uma metodologia, baseada em Operadores Morfológicos, Deteção de contornos, Métodos de Thresholding entre outros, para segmentar automaticamente imagens de US mamários, que determina diversos parâmetros com auxílio de Algoritmos Genéticos (AG).
- Monitorização da Disponibilização de Cobertura Celular Ubíqua em Ambiente Hospitalar: Medições do Espetro Radioelétrico no CHUCBPublication . Silva, Óscar; Teixeira, Emanuel; Corceiro, Ana; Reis, António; Velez, Fernando JoséNos últimos anos, as comunicações moveis celulares e sem fios têm evoluído de forma significativa, possibilitando o surgimento de várias tecnologias que transformaram a forma como nos comunicamos. No contexto da saúde, as Redes Sem Fios de Área Corporal (WBAN) possibilitam a monitorização remota de pacientes, recolhendo e transmitindo dados vitais através de dispositivos localizados ao redor ou dentro do corpo humano. Apesar dos avanços nas tecnologias de comunicação, estudos anteriores indicam que muitos hospitais enfrentam desafios de garantia de uma cobertura adequada, devido à complexidade das suas infraestruturas e às interferências que podem comprometer o sinal. O objetivo deste estudo é avaliar a cobertura celular no Centro Hospitalar Universitário Cova da Beira (CHUCB), identificando áreas onde a melhoria é necessária. Foram realizadas medições do espectro radioelétrico em mais de 20 pontos no CHUCB, utilizando dois equipamentos principais: o analisador de espetro NARDA SRM-3006 e o Scanner R&S®TSME6. As medições abrangeram diversas áreas do hospital, avaliando a potência do sinal recebido e a qualidade da ligação em diferentes horários, ao longo do dia. Os resultados indicam que as operadoras MEO e NOS dominam a cobertura celular no CHUCB, embora áreas como os pontos 17, 19 e 21 de medição, necessitem de melhorias significativas. Para a tecnologia 5G NR, a cobertura predominante em quase todos os pontos de medição pertence à operadora MEO, enquanto para a tecnologia LTE, a operadora NOS apresentou a melhor qualidade de sinal. Com base nos dados obtidos, propõe-se a instalação de femtocélulas nas áreas identificadas como deficientes para melhorar a cobertura celular no CHUCB.
- Internet das coisas e eficiência energética em agricultura de precisãoPublication . Pungo, Érica; Teixeira, Emanuel; Reis, António; Velez, Fernando JoséEste trabalho apresenta aspetos de Redes de Sensores sem Fios aplicadas à promoção da agicultura de precisão, inteligente e autónoma. O sistema de irrigação aqui desenvolvido com base em conceitos da Internet das Coisas (IoT) destina-se a combater os desperdícios, que ocorrem num modelo de rega tradicional e aprimorar a eficiência energética nas comunicações. Para desenvolver este sistema de irrigação foi utilizado o Raspberry Pi 4, juntamente com os módulos XBEE – PRO S1 da norma do Institute of Electrical and Electronic Engineering (IEEE) 802.15.4. Testaram-se os alcances de comunicação pretendidos. As medições da humidade do terreno, condições atmosféricas e horários apropriados de rega fornecem dados que são processados pelo sistema de monitorização, com o objetivo de realizar uma rega inteligente, autónoma, eficaz e sem desperdicios. Considerou-se a plataforma de interface gráfica Blynk para criar um painel que permite a visualização dos níveis de humidade e temperatura. A configuração do sistema de rega envolve a utilização de uma mini bomba submersível em água, de um sensor de temperatura e de um sensor de humidade do solo ligados a um Arduíno Uno. Este sensor comunica os valores da humidade para o Raspberry Pi. Os resultados subjacentes comprovam as vantagens da solução e mostram que a eficiência da comunicação entre nós XBEE é diferenciada dependendo da distância. Através da compação de dois modos de operação (Application Programming Interface, API, e modo transparente, AT) conclui-se que o modo AT é mais fácil de utilizar e económico, pois realiza configurações diretas e comunicações básicas.
- Characterization of Indoor Small Cells PropagationPublication . Andrade, Rooderson M.; Paulo, Rui R.; Francisco, Salomão M.; Teixeira, Emanuel; Velez, Fernando J.The characterization of the wireless medium in indoor small cell networks is essential to obtain appropriate modeling of the propagation environment. Universal Software Radio Peripherals (USRPs) and simple dipole antennas can emulate LTE-Advanced networks. In this work, we verify WINNER II propagation modeling for the indoor femtocell environment by considering different classrooms of 7.32 x 7.32 square meters near a common University Department corridor while measuring the power received in UEs placed in a grid of 49 points (radiated by the small eNodeB in the centre of the classroom of the own cell). These measurements have been carried out either by using the Software Radio Systems LTE that emulates the LTE-Advanced network and its UEs, or by measuring the received power in the UES with a Rohde & Schwarz FSH8 spectrum analyzer. In room 1, by varying the UE position, the highest values of the received power have occurred close to the central BS, and then in the opposite wall, further away from the interferer. Nevertheless, it was verified that the received power does not decrease suddenly because of the effect of the radiation pattern of the BS and UE antennas for large angles of apertures, as well as due to the non-omnidirectional horizontal antenna pattern. In addition, it was demonstrated that there is an effect of “wall loss” proven by the fact that path loss increases between room 2 and room 1 (or between room 3 and 2). If we consider an attenuation for each wall of circa 7-9 dB the behavior of the WINNER II model at 2.625 GHz for the interference coming across different walls is verified.
- Cost Benefit Analysis: Evaluation among the Millimetre Wavebands and Super High Frequency Bands of Small Cell 5G NetworksPublication . Teixeira, Emanuel; Ramos, Anderson; Lourenço, Marisa; Velez, Fernando J.; Peha, JonThis article discusses the benefit-cost analysis aspects of millimetre wavebands (mmWaves) and Super High Frequency (SHF). The devaluation along the distance of the carrier-to-noise-plus-interference ratio with the coverage distance is assessed by considering two different path loss models, the two-slope urban micro Line-of-Sight (UMiLoS) for the SHF band (from the ITU-R 2135 Report) and the modified Friis propagation model, for frequencies above 24 GHz. The equivalent supported throughput is estimated at the 5.62, 28, 38, 60, and 73 GHz frequency bands, and the influence of carrier-to-noise- plus-interference ratio in the radio and network optimization process is explored. Mostly owing to the lessening caused by the behaviour of the two-slope propagation model for SHF band, the supported throughput at this band is higher than at the millimetre wavebands only for the longest cell lengths. The benefit cost analysis of these pico-cellular networks was analysed for regular cellular topologies by considering unlicensed spectrum. For shortest distances, we can distinguish an optimal of the revenue in percentage terms for values of the cell length, R ≈ 10 m for the millimitre wavebands, and for longest distances, an optimal of the revenue can be observed at R ≈ 550 m for the 5.62 GHz. It is possible to observe that, for the 5.62 GHz band, the profit is slightly inferior than for millimetre wavebands, for the shortest Rs, and starts to increase for cell lengths approximately equal to the ratio between the break-point distance and the co-channel reuse factor, achieving a maximum for values of R approximately equal to 550 m.