Browsing by Autor "Gustavo A. Siles"

Now showing 1 - 20 of 38

A four-year variability study for Ka- and Q-band slant path propagation experiments in Madrid
(Universidad Politécnica de Madrid, 2019) Domingo Pimienta‐del‐Valle; Pedro García-del-Pino; José Manuel Riera; Gustavo A. Siles
In satellite propagation, variability (the fluctuations of certain parameter or phenomenon over time with respect to its average behavior) is assessed by using some statistical variable such as its variance over the years. Overall, there are few reports on rainfall and attenuation variability and only very few on fade dynamics, due to the need of experimental data for a long period of time with a high availability (a hard task to achieve) to produce meaningful results. Moreover, most of these reports are focused in the Ka-band. Having data with a high availability ( higher than 97 %) for a concurrent period of 4 years in Madrid for KA-SAT (19.680 GHz) and Alphasat (39.402 GHz) propagation experiments, a study on the variability of rainfall rate, excess attenuation and fade and inter-fade number of events is carried out. The results show a high variability of some parameters, confirming the need of performing multi-year experiments to assess statistically stable trends.
Accuracy assessment of water vapor and cloud attenuation estimated from ERA5 single level parameters at two sites with large difference of altitude
(2022) Gustavo A. Siles; Juan Pablo Arciénega; Yasmin Balderrama
ERAS reanalysis provides meteorological parameters that can help to predict atmospheric propagation effects. We investigate the accuracy of using ERA5 single level parameters, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$TCWV$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$TCLW$</tex> , to calculate water vapor and cloud attenuation, respectively, in El Alto (4065 m.a.s.l, Bolivia) and Madrid (633 m.a.s.l, Spain), locations having different climatological conditions. The assessment is performed using as reference the attenuation predicted by physical models combined with atmospheric vertical profiles from radiosondes: 4 years (El Alto) and 8 years (Madrid). The most recent global prediction models from ITU-R are also implemented to complete testing analysis: P.676-12 and P.804-8 global maps based methods. The results obtained show that water vapour attenuation from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$TCWV$</tex> predict statistics than can be used with small errors. Cloud attenuation from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$TCLW$</tex> show large discrepancies in El Alto. However, in Madrid, good agreement with RAOBS-based statistics is observed when using Salonen08 Tunned model as cloud detection model.
Alphasat propagation experiment in Madrid: Processing of the first year of measurements
(2016) José Manuel Riera; Gustavo A. Siles; Pedro García-del-Pino; Ana Benarroch
Universidad Politecnica de Madrid (UPM) is participating in the Alphasat propagation experiment by measuring the copolar level of the Q-Band beacon at 39.4 GHz. In this paper the processing procedures are discussed and exemplified by their application to the first year of measurements (April 2014 to March 2015). In the first phase (data pre-processing), daily files of normalized duration are developed and a flag vector is generated. Excess attenuation and total attenuation are separately calculated in the following processing phases. The reference level is calculated on an event-by-event basis in the first case, and obtained from GNSS-based gas attenuation in the second one. The different procedures are described and some examples of events are presented together with statistics of the first year of measurements.
Alphasat propagation experiment in Madrid: Results on excess and total attenuation
(2017) José Manuel Riera; Domingo Pimienta‐del‐Valle; Pedro García-del-Pino; Gustavo A. Siles; Ana Benarroch
Universidad Politécnica de Madrid (UPM) is participating in the Alphasat propagation experiment by measuring the copolar level of the Q-Band beacon at 39.4 GHz since April 2014. In this paper the results of the first two complete years of measurements (until March 2016) are presented with regards to excess and total attenuation. The reference level is calculated on an event-by-event basis in the first case, and obtained from GNSS-based gas attenuation in the second one. The results reflect the variability of the meteorological conditions in the climate of Madrid, with strong differences among the months of the year and between the two years, reinforcing the need of having long-term propagation experiments to capture all the variability of the propagation effects.
An Application of IGS Zenith Tropospheric Delay Data to Propagation Studies: Validation of Radiometric Atmospheric Attenuation
(IEEE Antennas & Propagation Society, 2015) Gustavo A. Siles; José Manuel Riera; Pedro García-del-Pino
The objective of this paper is to continue exploring the use of International GNSS Service (IGS) products as a tool to be used in Earth-space propagation experiments. With this purpose, 4 years of Zenith Tropospheric Delay data from IGS Villafranca station, in Madrid, Spain, have been processed with the aim to estimate the attenuation due to gases. These values are then used for the validation of a concurrent database of 4 years of radiometric measurements at 19.7 GHz, collected at Universidad Politécnica de Madrid (UPM) with the purpose of studying the attenuation effects of gases and clouds. The suggested validation procedure includes both an automatic routine and visual inspection. The validated measurements are statistically analyzed on a yearly and seasonal basis. Results point toward the usefulness of IGS data in propagation experiments as well as their integration in their processing routines.
An overview of 7 years of research on atmospheric propagation in Bolivia
(2024) Gustavo A. Siles
The Radiocommunications Laboratory, a research unit of the Universidad Privada Boliviana, has been investigating on atmospheric propagation and radiometeorology since 2017. The present paper showcases an overview of the work carried out during the last seven years, as well as some of its future lines of work.
ANÁLISIS COMPARATIVO: EL MARCO NORMATIVO DE LA TDT Y SU APLICACIÓN POR LOS GOBIERNOS DE ARGENTINA, BOLIVIA, BRASIL Y ECUADOR
(2020) Adriana Benítez; Belén Villena Araya; Laura Rivera; Andrés Laguna-Tapia; Gustavo A. Siles
La transición hacia la Televisión Digital Terrestre (TDT) en Latinoamérica es un fenómeno determinado por el contexto de cada país. En el presente artículo se busca describir cómo se gestionaron las políticas públicas en la transición hacia la TDT, en etapas de cambio de gobierno, en Argentina, Bolivia, Brasil y Ecuador. La investigación está estructurada en acápites, uno para cada país y uno comparativo. Se concluyó que existe una correlación entre las políticas públicas y los cambios de gobierno, sin embargo, esta misma no es de carácter determinante. Por otro lado, se evidenció que el estudio de marcos normativos referentes a la TDT puede ser de mucha ayuda para proyectos futuros similares. Finalmente, se puede afirmar que el carácter social de las políticas referentes a la TDT afecta directamente a la aplicación técnica de esta tecnología.
Annual Statistics from 5 Years of 1-Minute Rainfall Rate Measurements at a Specific Site in Bolivia
(2024) Gustavo A. Siles; Noelia Ayllon
1-minute precipitation data is crucial for evaluating the accuracy of rainfall rate prediction methods. In this paper, we present findings after conducting a 5-year rainfall rate measurement campaign at a single site in Bolivia, spanning from September 2018 to August 2023. Additionally, we utilized 6 years of 15-minute rainfall data from a nearby site. The widely-accepted EXCELL RSC model, with slight adjustments to account for the specific geographical characteristics of the study area, was applied to convert rainfall rate cumulative distributions from 15-minutes to 1-minute. The accuracy analysis performed reveals that long-term statistics of rain intensity predicted by the currently adopted version of the ITU-R P.837 model closely match the experimental results. The results indicate that the mean and RMS values of the relative error remain below 10%. This similarity is particularly notable when we incorporate monthly mean local values of surface temperature and rainfall amounts into the ITU-R model.
APLICACIÓN WEB PARA ESTIMACIÓN DE ATENUACIÓN POR LLUVIA EN ENLACES CON EL SATÉLITE TKSAT-1
(2020) Gustavo A. Siles; Gustavo H. Marín
En el presente artículo se introduce una aplicación web diseñada para el cálculo de estadísticas de atenuación por lluvia en Bolivia. Los cálculos que realiza son válidos para enlaces con el satélite boliviano TKSat-1 y se realizan en base la últimas Recomendaciones proporcionadas por la UIT-R. Se presentan un par de aplicaciones concretas tomando en cuenta dos emplazamientos en Bolivia: uno en una región tropical con altos niveles de precipitación, y otro en una región altiplánica en la región occidental del país. Los resultados obtenidos demuestran la utilidad de la aplicación y permiten estudiar de manera cuantitativa los diferentes efectos que produce la lluvia a diferentes bandas de frecuencias, así como su comportamiento estadístico en un año medio.
ATENUACIÓN POR NUBES EN BANDA Ka, Q Y W EN BASE A RADIOSONDEOS DURANTE TEMPORADAS DE LLUVIA Y SECA EN LOS ANDES CENTRALES: ESTUDIO EN EL ALTO, BOLIVIA
(2021) Alejandro García; Gustavo A. Siles; Juan Pablo Arciénega; Yasmin Balderrama
CLOUD ATTENUATION AT Ka, Q AND W BANDS BASED ON RADIOSOUNDINGS DURING RAINY AND NON-RAINY SEASONS IN CENTRAL ANDES: A STUDY IN EL ALTO, BOLIVIA
(2021) Alejandro García; Gustavo A. Siles; Juan Pablo Arciénega; Yasmin Balderrama
Cloud attenuation in satellite communication systems becomes a relevant issue as the frequency increases, and thus, it has to be taken into account when link availability is being calculated. This atmospheric impairment is a variable atmospheric phenomenon whose characterization has to be done not only on a yearly-basis but also on a seasonal and monthly basis. In the present paper, cloud attenuation statistics are reported at 20 GHz, 40 GHz and 75 GHz during rainy and non-rainy seasons in El Alto, Bolivia, at 4065 m of altitude, using 3 years of radiosoundings (2016-2019). Cloud detection models have been used for the calculations, including Salonen, Salonen08, Decker and CldMod models, and results obtained are compared to those given by the global model of the ITU-R Rec. P.840. The results lead to conclude that zenith cloud attenuation during rainy season can reach maximum values between 0.15 and 0.45 dB (20 GHz), 0.55 and 1.5 dB (40 GHz), and 1.3 and 3.9 dB (75 GHz) depending on the model to be used. In comparison, during non-rainy season these values vary between 0.08 and 0.33 dB (20 GHz), 0.26 and 1.1 dB (40 GHz), and 0.62 and 2.6 dB (75 GHz). On the other hand, statistics based on CldMod model and, in a less extent, Decker model are close to the ones obtained using the ITU-R global model. These observations could open the possibility of further studies assessing the reliability of meteorological parameters in digital maps at high altitude sites, because these data are used in global propagation models.
Cloud Attenuation in the Q band: Estimation from Experimental Data of Excess Attenuation
(2024) Domingo Pimienta‐del‐Valle; Gustavo A. Siles; José Manuel Riera; Pedro García-del-Pino
Although rain is the main atmospheric impairment to millimeter waves, the adverse impact of clouds becomes more relevant. This contribution presents a study carried out at the Universidad Politécnica de Madrid, in which cloud attenuation has been estimated from 5-year of experimental data of excess attenuation, gathered with a Q-band beacon receiver, using a novel method to separate the contribution of clouds in the absence of rain in site and along the path. In this method, different ancillary data obtained from co-located instruments- a disdrometer and a Ka-band beacon receiver- are used to detect in-site rain, whereas possible rain events along the path are detected from fade slope information, since fade slope is expected to be higher with rain than with cloud attenuation. Results are compared with available cloud attenuation models including the recently published Rec. ITU-R P.840-9.
Cloud detection models and their effect on the calculation of cloud attenuation: Assessment at Ka-and Q-band at 4065 meters of altitude
(2020) Gustavo A. Siles; Miguel Heredia; Rodrigo Harriague
This contribution presents a comparative study of methods to calculate cloud attenuation in satellite communications at 20 GHz and 40 GHz. A set of 3 years of radiosonde observations, collected at 4065 meters of altitude in the southern hemisphere, are used as input to four different cloud detection models, in order to retrieve integrated liquid water content, then calculate the attenuation due to clouds. The results are compared with those calculated using the ITU-R method based on ERA-40 NWP data. Based on the analysis performed at this particular site, located in an extensive high altitude Andean region in Bolivia, the results given by the ITU-R ERA-40 model seems to approximate better to the estimates obtained with cloud detection models other than the Salonen model, which is commonly accepted in temperate and lower altitude regions. However, in absolute values, the differences are less noticeable at 20 GHz than at 40 GHz.
Comparison Between ERA5 Cloud Parameters and Rainfall Rate in Madrid
(2024) Ana Benarroch; Gustavo A. Siles; Mishel Cuiza; José Manuel Riera
This ongoing study, conducted at UPM, investigates the relationship between rainfall rate and cloud parameters, using data sourced from ERA5 and experimental rainfall rate measurements collected with a disdrometer. The findings presented in this paper have been obtained using a comprehensive dataset spanning 6 years, including total cloud liquid water, cloud base height, total cloud cover, and rainfall rate. The statistical analysis presented comprises cumulative distributions, histograms, as well as scatter plots of the ERA5 cloud parameters against both the hourly average and maximum hourly rainfall rates. It has been found that low values of total cloud liquid water and cloud base height are more probable with simultaneous rain occurrence, whereas total cloud cover yields values equal or close to one, which is its highest value.
Comparison of the Height of the 0°C Isotherm With Several ERA5 Cloud Parameters
(2025) Ana Benarroch; Gustavo A. Siles; José Manuel Riera
The 0°C isotherm height is used in rain attenuation prediction models to calculate the rain height, as proposed in ITU-R Recommendations. In previous studies, the 0°C isotherm obtained for Madrid was compared with the 0° isotherm height provided by the European Centre for Medium-Range Weather Forecasts fifth-generation climate reanalysis (ERA5). In this paper, the comparison is extended to several ERA5 cloud parameters: cloud base height, total cloud liquid water content and total cloud ice water content. The results presented here include the monthly average, histograms of each parameter and binned scatter plots of pairs of parameters.
ESTIMACIÓN DE INTENSIDAD DE LLUVIA PARA ESTUDIOS DE PROPAGACIÓN RADIOELÉCTRICA EN BOLIVIA
(2018) Gustavo A. Siles; Daniel Chirinos
La caracterización de la intensidad de lluvia, Rp(mm/h), para estimar la atenuación, A (dB) que produce una precipitación, es de gran importancia dada la relación directa entre ambas variables. Una descripción precisa de R requiere de estadísticas anuales obtenidas a partir de campañas de mediciones pluviométricas de varios años. En ausencia de esta información, es posible utilizar modelos de predicción que permiten determinar la Función de Distribución Acumulada Complementaria, P(R). El presente estudio implementa modelos de predicción propuestos en diferentes versiones de la Recomendación UIT-R P.837 con el objetivo de obtener la función P(R) para diferentes lugares de Bolivia. Los resultados obtenidos llevan a la conclusión preliminar que el modelo propuesto en la última versión de la Recomendación seguiría mejor las características climatológicas de los sitios seleccionados para el estudio.
ESTIMACIÓN DE INTENSIDAD DE LLUVIA PARA ESTUDIOS DE PROPAGACIÓN RADIOELÉCTRICA EN BOLIVIA
(2018) Gustavo A. Siles; Daniel Chirinos
La caracterización de la intensidad de lluvia, Rp(mm/h), para estimar la atenuación, A (dB) que produce una precipitación, es de gran importancia dada la relación directa entre ambas variables. Una descripción precisa de R requiere de estadísticas anuales obtenidas a partir de campañas de mediciones pluviométricas de varios años. En ausencia de esta información, es posible utilizar modelos de predicción que permiten determinar la Función de Distribución Acumulada Complementaria, P(R). El presente estudio implementa modelos de predicción propuestos en diferentes versiones de la Recomendación UIT-R P.837 con el objetivo de obtener la función P(R) para diferentes lugares de Bolivia. Los resultados obtenidos llevan a la conclusión preliminar que el modelo propuesto en la última versión de la Recomendación seguiría mejor las características climatológicas de los sitios seleccionados para el estudio.
Estudio radioeléctrico y problemáticas en una red WiFi con alta densidad de usuarios
(2019) Jhenifer Orozco; Gustavo A. Siles
Evaluation of ITU-R P.837 rainfall rate models using high-resolution measurements in Bolivia
(2024) Noelia Ayllon; Gustavo A. Siles
Rainfall rate is a key parameter in radiowave propagation, directly influencing rain attenuation prediction. This paper assesses ITU-R P.837 models that predict 1-minute rainfall rate statistics, using a 5-year high-resolution dataset of measurements in a temperate region of Bolivia as reference. Error analysis shows that the ITU-R P.837-7 model significantly outperforms previous versions, with enhanced accuracy achieved when local mean monthly meteorological data is used as input. Utilizing earlier versions of the ITU-R P.837 model may yield unreliable or inaccurate results.
Evaluation of total precipitation from ERA5-Land reanalysis for rain attenuation studies
(2024) Mishel Cuiza; Gustavo A. Siles
Propagation researchers continuously seek rainfall data to enhance rain attenuation modeling. This paper compares 60-to-1 minute converted long-term rainfall statistics from ERA5-Land reanalysis with experimental measurements from two rain sensors and ITU-R predictions for a specific region in Bolivia. Despite improved spatial resolution, discrepancies arise due to time resolution and grid averaging.