6 resultados
Resultados de la búsqueda
Mostrando 1 - 6 de 6
Ítem 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 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 Simulation of vertical handover algorithms with NCTUns(Society for Modeling and Simulation International, 2010-01-01) Navarro Cadavid, AndrésThis paper presents the simulation of Vertical Handover Algorithms (VHA) using NCTUns and tested them on scenarios with WiFi/GPRS or WiFi/WiMAX Mobile networks: The first evaluates parameters such as the network bandwidth, economic cost of the connection and the mobile node mobility and uses a cost function toevaluate candidate networks. The second one is based on application requirements such as bandwidth, latency and % packet loss rate. The third one organizes the nodes connections to balance the load on connection points, optimize battery consumption, or both. We developed several scripts in C and PERL language for inclusion in the tool like other components and use a NCTUns API to communicate with the simulation engine. In simulation scenario we use the multi-interface node for Intelligent Transportation System (ITS) networks or a node for each technology, but they behave as a single node with multiple interfaces. Simulations results are used to analyze the VHAs performance measuring handover delay, number of avoided handovers and computational cost of the algorithms.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 Vertical handoff algorithms - A new approach for performance evaluation(IEEE, 2010-12-06) 2010 IEEE Globecom Workshops, GC'10A myriad of Vertical Handoff Algorithms (VHA) have been proposed by researchers and networks practitioners. These algorithms allow mobile terminals (MT) to maintain the network connection when they switch from one wireless network to another one. Given the amount of proposed VHA and the need for an objective assessment of these solutions different evaluation methodologies have been proposed, becoming the problem of evaluation of VHA in an interesting challenge. However, there is no consensus on how to evaluate performance of VHA. In this paper, we address this issue by proposing a new approach for evaluating the VHA, which is based on multi -criteria evaluation and criticality analysis - a specific concept taken from the operational reliability. The new approach allows evaluating VHA using measured values of some defined parameters, which can be obtained from simulating VHA on a network simulation tool (e.g. NCTUns, NS -2, OMNET++, among others) or generic software simulation tools (e.g. MATLAB). As a test of the new model, an evaluation of five VHA is presentedÍtem Evaluation Model for Vertical Handoff Algorithms(IGI Global, 2012-02-01) Navarro Cadavid, AndrésThis chapter begins by introducing the problem of vertical handoff in heterogeneous wireless networks and illustrates the lack of a proper evaluation model to compare the different Vertical Handoff Algorithms (VHAs) that have been proposed in the literature over the last few years. In the following sections, a novel evaluation model for VHAs is introduced and described. The design of the new evaluation model is based on the multi-criteria evaluation methodology and criticality analysis, which permitted the model to be developed as a software component. The new proposed evaluation model is flexible in terms of the number of evaluation parameters and facilitates the analysis of VHAs by researchers. A specific case study considering some VHAs is presented, analyzed, and discussed in detail. The case study is used to compare the proposed evaluation model with another evaluation model (Ordinal Model) for VHAs.