14 resultados
Resultados de la búsqueda
Mostrando 1 - 10 de 14
Ítem Technological Models of Municipal Wireless Networks based on Hybrid WiFi/WiMAX Mesh Networks: a proposal to Colombian Municipalities(Ieee, 2009-10-30) Rodríguez Hernández, Pedro SalvadorThe telecommunications infrastructure citizen-oriented has become a necessity in cities that wish to direct themselves to a new Information Society. One of the technological alternatives for these infrastructures is municipal wireless networks. These municipal wireless networks offer flexibility, speed of installation and less implementation costs for cities. For this reason, it is considered of interest the wider use of wireless networks for the Colombian municipalities, considers that in this environment there is limited budget and low rate of connectivity to broadband networks. This article presents a review of the current state of municipal wireless networks related to the technological aspects, with the intention to propose two technological architectures that may be feasible to implement in the Colombian municipalitiesÍtem SNR estimation for on body communications in MB OFDM Ultra Wide Band communications(Ieee Computer Society, 2010-04-12) Navarro Cadavid, AndrésIn this paper a new signal to noise ratio estimator algorithm based on the moments of the received signal is presented. The novel algorithm has been designed for Ultra Wide Band communications based on Multi Band Orthogonal Frequency Division Multiplexing (MB-OFDM) communication systems. In this proposal, we analyze the behavior of ultra wide band channels when the time and frequency fading have fast changes. Hence, different time coherence values were considered and all the frequency fading models are based in real measurements made in an anechoic chamber. It is remarkable that all the measurement campaigns were focused on body communications. We conclude that the proposed model can be used for SNR estimation in adaptive modulation and channel estimation and link quality control in MB OFDM systems. The performance of the proposed SNR estimation algorithm and its comparison with other SNR estimators was achieved through simulations based on real channel measurements.Ítem A statistical channel model for on body Area networks in Ultra Wide Band Communications(IEEE, 2009-09-10) Cardona, NarcisThis paper presents a novel statistical channel model for Ultra Wide Band Communications when On Body Area Networks Environments are considered. Results and Analysis of frequency measurements from 1GHz to 12GHz for body area networks are described. We propose a modified Saleh-Valenzuela statistical channel model considering different assumptions for small scale statistics in the model. Results show that the small scale amplitude follows a log normal distribution, the inter arrival times between multi path components are poisson process; the decay factor, the number of paths and clusters follow exponential distributions. The proposed model can be used for realistic simulations for on body communications in Ultra Wide Band systems. © 2009 IEEE.Ítem Arquitecturas tecnológicas y modelos de negocio para un operador de Hotspots inalámbricos WI-FI.(Universidad Icesi, 2006-10-11) Varela, Claudia P.; Escandón, Alfredo; Castillo, Hector F.; Murillo, Sandra L; Millán, Andrés Felipe; Zúñiga Cañón, Claudia LilianaThis paper presents technology architectures and business models in wireless hotspot Wi-Fi service providers market. Besides to describe a business and technology model for Broadband Wireless Network (RIBA) of EMCALI Local Service Provider, this could be implemented in the Wireless Hotspots Colombian Providers.Ítem The UWB-OFDM Channel Analysis in Frequency(IEEE, 2009-06-12) Llano Ramírez, GonzaloIn this paper, the ultra-wideband channel with orthogonal frequency division multiplexing (UWB-OFDM) is analyzed in the frequency domain. For UWB-OFDM channels with log-normal fading in the time domain, we show that the amplitude of each subcarrier can be approximated by a Nakagami-m random variable, where the fading parameter, the mean power and the correlation coefficient are expressed in terms of the following parameters: time arrival of the clusters, inter-arrival time of rays inside clusters, and power decay constants of rays and clusters.Ítem Using game engines for wideband channel estimation parameters in Andean cities(IEEE, 2010-04-16) Guevara, DinaelThis paper shows the results obtained with a new raytracing method using an open source game engine and high performance graphic cards for the estimation of path loss and parameters of wide-band channel with high accuracy, for both low or high base-station in some specific outdoor urban Andean scenario as is the Cost 2100 Cali reference scenario. We use the algorithms and techniques developed by the game community together with graphics hardware accelerators for parameters estimation in time and frequency for wide-band channels. We use a 3D model dynamically obtained from raster digital elevation model (DEM) with information about constitutive parameters of materials and compare it with measurements, obtaining a good fit.Ítem Implementación de una red de banda ancha inalámbrica a nivel de acceso en la ciudad de Cali(Universidad Icesi, 2006-12-01) Sossa Mendoza, Yesid Fernando; Pachón de la Cruz, AlvaroCada día se ven nuevas empresas ingresando al mercado de banda ancha. La creciente demanda está determinada por el aumento en el volumen de datos transmitidos sobre Internet, el creciente número de procesos y aplicaciones destinadas a realizarse en línea y en como las empresas van integrando las redes con la operación central de su negocio. Es un hecho, como lo vemos en la actualidad, que la demanda ha venido de las PYMES, de las SOHO, de los conjuntos y edificios residenciales y de las universidades [3]. Toda empresa que decide ofrecer banda ancha debe regirse por un esquema común para prestar sus servicios, y así estar a tono con los nuevos esquemas de comunicaciones que permiten maximizar la operación de los recursos y la rápida identificación de fallas. Un ejemplo claro de esto es el esquema Acceso - Backbone - Servicios.Ítem Frequency UWB Channel(InTech, 2011-01-01) Navarro Cadavid, AndrésUltra wideband (UWB) transmission systems are characterized with either a fractional bandwidth of more that 20%, or a large absolute bandwidth (>500 MHz) in the 3.1 GHz to 10.6 GHz band, and for a very low power spectral density (-41.25 dBm/MHz, equivalent to 75nW/MHz), which allows to share the spectrum with other narrowband and wideband systems without causing interference (FCC, 2002), this spectral allocation has initiated an extremely productive activity for industry and academia. Wireless communications experts now consider UWB as available spectrum to be utilized with a variety of techniques and not specifically related to the generation and detection of short RF pulses as in the past (Batra, 2004). For this reason, UWB systems are emerging as the best solution for high speed short range indoor wireless communication and sensor networks, with applications in home networking, high-quality multimedia content delivery, radars systems of high accuracy, etc. UWB has many attractive properties, including low interference to and from other wireless systems, easier wall and floor penetration, and inherent security due to its Low Probability Interception/Detection (LPI/D). Two of the most promising applications of UWB are High Data Rate Wireless Personal Area Network (HDR-WPAN), and Sensor Networks, where the good ranging and geo-location capabilities of UWB are particularly useful and of interest for military applications (Molisch, 2005).Ítem Estrategia para la formación de comunidades virtuales que generen y usen aplicaciones en la red de nueva generación de un operador de telecomunicaciones [recurso electrónico](Universidad Icesi, 2014-07-08) Hernández , Victor Hugo; Pachón de la Cruz, Alvaro; Asesor TesisEl negocio de las telecomunicaciones es altamente competido, evoluciona rápidamente intentando sorprender al usuario tratando siempre de ofrecer más servicios por menos dinero, es común para los usuarios cada día recibir una mayor cantidad de tiempo en las llamadas, una mayor velocidad de conexión, una mayor capacidad de almacenamiento, provocando que los ingresos que percibidos por cada usuario resulten cada vez menores. Por otra parte, aparecen nuevos jugadores en el negocio (por ejemplo, los proveedores de servicios sobre la nube) que pueden atraer un volumen creciente de clientes sin necesidad de proporcionar acceso, utilizando la conexión provista por cualquier operador. Desde esta perspectiva, el operador tradicional tiene una menor utilidad porque debe compartirla.Ítem A novel SNR estimation algorithm for MB OFDM ultra wide band communications(IEEE, 2014-09-10) anavarro@icesi.edu.coIn this paper we propose a novel signal to noise ratio algorithm based on the moments of the received signal. The novel algorithm has been designed for Multi Band Orthogonal Frequency Division Multiplexing (MB-OFDM) communication systems in ultra wide band channels. The proposed algorithm is a switched estimator that uses two equation models, one is for large SNR scale and the other for low SNR scale. The proposed model can be used for SNR estimation in adaptive modulation and channel estimation and link quality control in MB OFDM systems. This algorithm can be implemented in receivers with simple structures. The performance of the proposed SNR estimation algorithm and its comparison with other SNR estimators was achieved through simulations. © 2009 IEEE.