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Ítem Handset based automatic network re-selection system for GSM/GPRS and WiFi(ACM Press, 2008-10-30) Navarro Cadavid, AndrésThis paper presents the results of the development of a handset based automatic network reselection software system, which allows keeping end-to-end connections through semi-transparent handoff on WiFi/GSM-GPRS networks. A description of the developed system's software architecture is given, as well as of the components implemented for it, their functionalities and flow of control, all of which allow the permanent discovery of available networks for the mobile device, their evaluation, selection and switching to the network which offers the best ratings in its performance and operational profile, taking into account the preferences previously configured by the user. The system was developed in Java and C# for different operating systems (WinXP, WinMobile and Linux), and its interoperability has been tested in them. Some of the test scenarios are described and final comments about the tests results are given. Copyright 2008 ACM.
Ítem Aplicación de modelos markovianos en sistemas de comunicación móvil celular GSM900*(Universidad Icesi, 2006-07-28) Mantilla F., Javier D.; Monclou S., Alex A.; Navarro Cadavid, Andrés; Camerano F., RafaelEl presente artículo muestra en forma clara que el canal de acceso RACH del sistema GSM (Global System for Mobile) se puede modelar como una cadena de Markov discreta. La teoríade cadenas de Markov se emplea para encontrar el comportamiento de estado estable en el modelo de seis estados planteado por la norma GSM utilizando un lenguaje de alto nivelcomo Matlab, que se emplea para simular el modelo planteado teóricamente. Los resultados de las simulaciones muestran el comportamiento estadístico del proceso de selección yreselección de celda del terminal móvil en el sistema GSM.Ítem Herramienta gráfica de modelado de redes inalámbricas basada en modelos de propagación de señales en interiores(Universidad Icesi, 2006-07-28) Osorio Betancur, Juan David; López Ocampo, Sandra Paulina; Navarro Cadavid, AndrésEl presente artículo describe el proceso de implementación de un modelo de predicción de la propagación de señales en interiores, basado en el modelo semiempírico de K. W. Cheung, J. H. M. Sau, y R. D. Murch,[1] donde se tienen en cuenta la atenuacióndebida a la distancia, el ángulo de incidencia sobre las paredes, laatenuación asociada a estas mismas y las zonas de Fresnel.Los datos del entorno a simular son tomados de un archivo DXF que debe seguir un formato establecido. Se obtienen del usuario la atenuación asociada a cada tipo de pared y la ubicacióndel punto de acceso. También se desarrolla un algoritmo desombreado que optimiza el tiempo de simulación debido a su sencillez. Finalmente se muestra la comparación de los resultados de la simulación y los datos obtenidos en la prueba de campo.Ítem Some comparison between propagation models in Cost 2100 Cali Reference Scenario(Universidad Icesi, 2009-08-18T20:25:14Z) Ardila, Carlos Andredy; Mejía Mateus, Duván Javier; Navarro Cadavid, AndrésIn this paper we present results from traditional propagation models like Hata and Walfish Bertoni, implemented in our planning tool, and compare it with results obtained from a commercial tool and also with measurements provided by a local operator. For this experiment, we use the Cost 2100 Cali Reference Scenario.Ítem Método de evaluación y selección de herramientas de simulación de redes(Universidad Icesi, 2011-03-01) García Dávalos, Alexander; Vásquez Mejía, Andrés; Navarro Cadavid, Andrés; Escobar Paz, Lina MarcelaCurrently exists many software tools designed for Network Simulation (both commercial and Open source), situation that present an important decision to make for many researchers: Which tool use for network simulation? This paper proposes a method for evaluation/selection of network simulation tools, based in two key factors: ISO/IEC 9126-1 standard, which defines a quality model for software evaluation; and a cost function, based on values assigned to each one of the six items defined by ISO/IEC 9126-1. This method allows an expert based classification for each of the analyzed tools. We executed a test for NS-2 and NCTUns network simulation tools and obtained results was contrasted with technical reports and scientific articles related with network simulation tools.Ítem Ajuste estadístico de modelos de propagación de señal usando medidas de la ciudad de Cali(Universidad de Santiago de Cali,, 2012-03-20) Ardila, Carlos AndredyLa dificultad de estimar con exactitud la influencia de los obstáculos, los edificios y el terreno en la pérdida de trayectoria de la señal hace que los modelos de propagación, generalmente utilizados para la planificación de redes inalámbricas externas, en entornos urbanos incluyan algunos elementos empíricos. Por lo tanto, la ecuación final generalmente contiene constantes y coeficientes para los diferentes términos, que se obtienen principalmente a partir del análisis estadístico de mediciones recolectadas durante actividades de drive test en grandes áreas de la ciudad. Desafortunadamente, estos resultados son realmente válidos únicamente para las áreas de la ciudad en las que se obtuvieron y, en el mejor de los casos, para áreas o ciudades similares. Sin embargo, si el nivel de similitud no es suficiente, es necesario realizar ajustes, un proceso que resulta en la formulación de nuevas constantes y nuevos coeficientes. El propósito de este artículo es discutir algunos de los hallazgos obtenidos durante el proceso de ajuste estadístico al escenario de la ciudad de Cali, de los modelos Okumura-Hata, Stanford University Interim (SUI) y Walfisch-Bertoni, usando mediciones.Ítem Simulation and analysis of compressed sensing technique as sampling and data compression and reconstruction of signals using convex programming(Institute of Electrical and Electronics Engineers Inc., 2016-12-14) Navarro Cadavid, Andrés; 21st Symposium on Signal Processing, Images and Artificial Vision, STSIVA 2016The information management has been treated primarily under the Nyquist sampling theory, but it is important to introduce new theories that replace deficiencies of what we know as the classical theory of sampling. These deficiencies create difficulties in data acquisition; this is a problem when large volumes of information are handled, in addition to the higher costs in storage and processing. This article presents the results obtained from the compressed sensing simulation technique applied to two types of signals. The aim of this paper was to simulate a communication system involving the data recovery applying the compressed sensing technique, analyzing sampling rates reduction, measuring the efficiency of the process and the behavior of the technique. The recovery of the signal is made using convex programming and using l1 norm minimization for recover the signals in the time domain. We used the L1Magic toolbox, which is a set of Matlab® functions used to solve optimization problems in this case with the l1eqpd function. As a summary of the obtained results, we checked the efficiency of the compressed sensing technique, minimum average rates for sampling the constructed signals, and the best performance of the technique to recover soft signals compared to non-differentiable signals. Additionally, the recovery results of an audio signal with the compressed sensing technique, by varying the sampling rate and checking the audibility of the signal, are presented. This allowed the testing of this technique in a real scenario, finding a good opportunity for the transmission of audio signals in a more efficient way.Ítem Spectrum monitoring system and benchmarking of mobile networks using open software radios SIMONES(Institute of Electrical and Electronics Engineers (IEEE), 2015-11-01) Aguilar, Julio HectorIn this article, we briefly describe a project whose main objective is to offer simple, unattended operation and low cost spectrum monitoring units based on open source software and hardware for Software Defined Radio (SDR), to support monitoring and management tasks and to complement traditional fixed, transportable and mobile spectrum monitoring units, with specific functionalities that are not common in typical monitoring systems. The system was designed according to the monitoring tasks specified in ITU-R Recommendations. The project is the result of cooperation between a company specialized in spectrum related activities and a university, with a Colciencias grant and the endorsement of the Colombian National Spectrum Agency.Ítem Using game engines and graphic technologies for ray-tracing in future wireless(Institute of Electrical and Electronics Engineers Inc., 2014-04-11) Guevara, DinaelWe present here a discussion about the use of 3D ray-tracing (RT) techniques based on game engines and graphic technologies to derive the multipath channel. Our approach harnesses the power of video game development engines to provide the urban 3D model and 3D RT for exploration and analysis of multipath channel for a wide frequency range in different complex outdoor scenarios. The advantage of this approach is that it efficiently utilizes the potential and capabilities in the graphical processing units (GPUs) and provide high performance in computing time with accurate results. We demonstrate the usefulness of this approach using our 3D RT in different applications. We show simulation results and compare them with measurements, obtaining a good fit. © 2014 European Association on Antennas and Propagation.Ítem WLAN's access points java based automatic location tool(World Wireless Congress, 2007-05-23) Navarro Cadavid, AndrésIn this paper, we will show the development process and the results obtained with a Java based toll for automatic location of WLAN Access Points. We will describe the algorithm developed and the results obtained until the time we wrote the paper. Also we will discuss future work and possible evolution for the tool.