Browsing by Author "Leonor, Nuno R."
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- A 2D ray-tracing based model for wave propagation through forests at micro-and millimeter wave frequenciesPublication . Leonor, Nuno R.; Sanchez, Manuel Garcia; Fernandes, Telmo; Caldeirinha, Rafael F. S.This paper proposes the extension of a 2-D ray-tracing-based model for radiowave propagation in the presence of trees and vegetation areas to include real-sized trees and outdoor forest scenarios. The original propagation model proved to be suitable to characterize the electromagnetic behavior in the presence of indoor tree formation scenarios, despite some limitations found when applied to real-sized trees. In addition, the original propagation model requires the prior knowledge of the trees’ re-radiation function to extract the relevant propagation input parameters, which is not always possible to obtain in outdoor scenarios. Therefore, an empirical method to extract the relevant input propagation parameters based on simple measurements is proposed. The performance of the proposed propagation model extension is extensively assessed in both the line-of-trees and tree formation scenarios, including various (and mixed) species, both in- and out-of-leaf foliation states, and at three signal frequencies. Finally, depending on the type of scenario, a benchmark between the proposed propagation model and both the radiative energy transfer (RET) and discrete RET (dRET) models, for line-of-trees and tree formation, respectively, is presented.
- A 2D Ray-Tracing Based Model for Wave Propagation Through Forests at Micro-and Millimeter Wave FrequenciesPublication . Leonor, Nuno R.; Sanchez, Manuel Garcia; Fernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.; Caldeirinha, RafaelThis paper proposes the extension of a 2-D ray-tracing-based model for radiowave propagation in the presence of trees and vegetation areas to include real-sized trees and outdoor forest scenarios. The original propagation model proved to be suitable to characterize the electromagnetic behavior in the presence of indoor tree formation scenarios, despite some limitations found when applied to real-sized trees. In addition, the original propagation model requires the prior knowledge of the trees' re-radiation function to extract the relevant propagation input parameters, which is not always possible to obtain in outdoor scenarios. Therefore, an empirical method to extract the relevant input propagation parameters based on simple measurements is proposed. The performance of the proposed propagation model extension is extensively assessed in both the line-of-trees and tree formation scenarios, including various (and mixed) species, both in- and out-of-leaf foliation states, and at three signal frequencies. Finally, depending on the type of scenario, a benchmark between the proposed propagation model and both the radiative energy transfer (RET) and discrete RET (dRET) models, for line-of-trees and tree formation, respectively, is presented.
- A Discrete RET Model for Millimeter-Wave Propagation Through VegetationPublication . Leonor, Nuno R.; Caldeirinha, Rafael; Fernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.; Richter, Jurgen; Al-Nuaimi, MiqdadA modified discrete radiative energy transfer (dRET) model has been developed envisaging to overcome some of the limitations found in the original dRET formulation, namely in terms of angular resolution, oblique and nonuniform incidence, and antenna patterns. In addition, the discretized squared nature of the dRET model can lead to some amount of staircase error. Hence, this paper also proposes an input parameter scaling model, enabling the characterization of tree cells with reduced size. The performance of the modified dRET model is assessed not only against the current ITU-R P.833-8 recommendation for propagation in vegetation but also against directional spectra measurements conducted in an outdoor inhomogeneous forest at 20 and 62.4 GHz.
- Input parameter extraction method for point scatterer formulation in vegetation media at millimetre-wave frequenciesPublication . Leonor, Nuno R.; Caldeirinha, Rafael F. S.; Sánchez, Manuel García; Fernandes, TelmoAn empirical method to extract the relevant point scatterer formulation input parameters for appropriate radio coverage simulation in vegetation areas, is proposed. While the original propagation model would require the prior knowledge of the complete tree(s) re-radiation function(s) to extract the relevant propagation input parameters, the empirical method proposed herein is based only on two simple measurements. Re-radiation measurements of several specimens of Thuja pelicata and Ficus benjamina trees at two frequencies have been used to validate the proposed simplified extraction method. The proposed empirical model was then used to characterise the propagation phenomena of various trees arranged in four different scenarios. Subsequently, directional spectra measurements performed inside an anechoic chamber at both 20 and 62.4 GHz were used to assess the empirical model performance, while predicting the received signal level arriving from various directions. A relatively good overall model performance when applied to tree formations was obtained which, coupled with the simplified parameter extraction proposed, makes it suitable to be integrated in commercial simulation platforms and/or as input data to other propagation models that may require the prior knowledge of the individual tree re-radiation functions.
- Satellite‐Terrestrial Channel Characterization in High‐Speed Railway Environment at 22.6 GHzPublication . Ma, Lei; Guan, Ke; Yan, Dong; He, Danping; Leonor, Nuno R.; Ai, Bo; Kim, JunhyeongThe integration of satellite and terrestrial communication systems plays a vital role in the fifth-generation mobile communication system (5G) for the ubiquitous coverage, reliable service, and flexible networking. Moreover, the millimeter wave (mmWave) communication with large bandwidth is a key enabler for 5G intelligent rail transportation. In this paper, the satellite-terrestrial channel at 22.6 GHz is characterized for a typical high-speed railway (HSR) environment. The three-dimensional model of the railway scenario is reconstructed and imported into the Cloud Ray-Tracing (CloudRT) simulation platform. Based on extensive ray-tracing simulations, the channel for the terrestrial HSR system and the satellite-terrestrial system with two weather conditions are characterized, and the interference between them are evaluated. The results of this paper can help for the design and evaluation for the satellite-terrestrial communication system enabling future intelligent rail transportation.
- A Three-Dimensional Directive Antenna Pattern Interpolation MethodPublication . Leonor, Nuno R.; Caldeirinha, Rafael; Sanchez, Manuel Garcia; Fernandes, Telmo R.An interpolation method to reconstruct the 3-D directive antenna pattern is presented. The proposed method is based on the prior knowledge of the original antenna's principal planes patterns, to which a specific weighting method is applied to obtain an approximate 3-D antenna pattern. The performance of the proposed interpolation method is evaluated against 3-D antenna patterns from three typical directional antennas, extracted from appropriate electromagnetic simulation. Finally, a comparative analysis between the proposed method and current interpolation methods present in the literature is presented.
- A Two-Dimensional Ray-Tracing-Based Model for Propagation Through Vegetation: A practical assessment using ornamental plants at 60 GHz. [Wireless Corner]Publication . Leonor, Nuno R.; Caldeirinha, Rafael F. S.; Garcia Sanchez, Manuel Garcia; Fernandes, Telmo R.This article aims to practically assess the point scatterer formulation to characterize the electromagnetic behavior of ornamental plants with varying thickness at 60 GHz. The proposed propagation model uses various point scatterers with specific radiation characteristics, distributed within a computational area, to describe the effect of the plants present in the radiowave propagation path. Additionally, a ray-tracing-based engine is used to gather all the interactions between the point scatterers present in the simulation channel. The performance of the proposed modeling approach is assessed against reradiation measurements of single and isolated plants, performed in the 60-GHz frequency band, inside an anechoic chamber. Additional model validation is obtained from reradiation measurements of several clumps of plants, mimicking specimens with varying thickness.