Browsing by Autor "Roberto Bustamante"

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A fast method to seek the mean and variance of the summation of lognormal variables
(Universidad de Antioquia, 2021) Juan Guillermo Torres Hurtado; Roberto Bustamante; Carlos Caicedo
The sum of lognormal variables has been a topic of interest in several fields of research such as engineering, biology and finance, among others. For example, in the field of telecommunications, the aggregate interference of radio frequency signals is modeled as a sum of lognormal variables. To date, there is no closed expression for the probability distribution function (PDF) of this sum. Several authors have proposed approximations for this PDF, with which they calculate the mean and variance. However, each method has limitations in its range of parameters for mean, variance and number of random variables to be added. In other cases, long approximations as power series are used, which makes the analytical treatment impractical and reduces the computational performance of numerical operations. This paper shows an alternative method for calculating the mean and variance of the sum of lognormal random variables from a computational performance approach. Our method has been evaluated extensively by Monte Carlo simulations. As a result, this method is computationally efficient and yields a low approximation error computation for a wide range of mean values, variances and number of random variables.
Herramienta para la predicción de la radiopropagación en una celda inalámbrica
(Universidad Autónoma del Estado de México, 2008) Diego R. Bernal; Carlos A. Díaz; Carlos-Iván Páez-Rueda; Roberto Bustamante
"En el presente artículo se presentan los resultados de una nueva herramienta asistida por computador desarrollada para la predicción de la cobertura en una celda inalámbrica válida para la banda de VHF y UHF. Esta aplicación está basada en el modelo electromagnético de dos rayos en combinación con el modelo de difracción planteado por Vogler. Para la validación de los resultados encontrados por medio de la herramienta, se utilizó un sistema de monitoreo automático y se registraron los niveles de potencia en dos trayectos en la ciudad de Bogotá, Colombia. Con los niveles de potencia medidos se propuso un nuevo modelo empírico simplificado, que permite predecir el cubrimiento de regiones urbanas conformada por construcciones cuya altura es comparable con la altura del transmisor."
Literature review of deploying small transmitters on a spectrum sharing scheme
(Universidad de Antioquia, 2021) Juan Guillermo Torres Hurtado; Roberto Bustamante; Carlos Caicedo
Nowadays, there are a lot of misinformation and myths related to both the deployment of antennas for 5G and the frequency bands used in such technology. Many of these myths arise from the lack of serious research documents released in common language to be understood by different knowledge areas. This work makes a small contribution in this regard and shows a bibliographic review of the most relevant characteristics related to the problem of deployment of transmitters (a.k.a. base stations), and also takes into account a spectrum sharing scheme. As a case study, we will analyze the CBRS regulation used in the United States for the deployment of 5G, it will provide an overview of engineering problems and also, the areas of research that still need to be explored.
Modelo de simulación de la capa MAC IEEE 802.16-2004 para modo Mesh. IEEE 802.16-2004 MAC Layer Simulation Model in the Mesh Mode
(Universidad Icesi, 2007) Javier E. Sierra; Roberto Hincapié; Roberto Bustamante; Leonardo Betancur
IEEE 802.16-2004 standard supports mesh networks topology and it’s important to realize the performance of such systems. Simulation of communication systems allows its optimization in performance measures. In this article we present a model developed over Network Simulator 2 to simulate data link layer operation in mesh topologies based on that standard. We present the results based on a link scheduler and the model developed, as the mean queue length, mean queue delay and the system capacity for different topologies.
Novel computational approach to solve convolutional integral equations: method of sampling for one dimension [Online First]
(2019) Carlos-Iván Páez-Rueda; Roberto Bustamante
Objective: This paper proposes a new methodology to solve one-dimensional cases of integral equations with difference kernels using Fourier analysis. Methodology: In this study, it was proven that any Fredholm equation of the first kind can be expressed as an extended convolutional problem; consequently, a new approach to solve that problem, using the nonideal instantaneous sampling theory and Fourier analysis, can be developed. Results and Discussion: The proposal was extensively evaluated and compared with the method of moments by considering two benchmarks. The first was a narrowband problem related to a second-order differential equation with specific boundaries. The second was a standard wideband problem related to wire antenna radiation in electrodynamics, known as the Pocklington equation. In both cases, we derived new interpretations and different approaches to solve the problems efficiently. Conclusions: The new proposal generalized the method of moments via new interpretations, strategies and design rules. We found that the techniques based on the method of moments are point-matching procedures independent of the weighting functions; the basis functions can be designed as generalized interpolation functions with more information provided by the original domain; the weighting functions literally represent a sampled linear filter; the unknown continuous function can be approximated without using the classical variational approach; and several new strategies based on the Fourier transform can be used to reduce the computational cost
Tool for radio propagation prediction in a wireless cell
(2008) DiegoR. Bernal; Carlos A. Díaz; Carlos-Iván Páez-Rueda; Roberto Bustamante