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Channel Model (channel + model)
Selected AbstractsThe two-user Gaussian interference channel: a deterministic view,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 4 2008Guy Bresler This paper explores the two-user Gaussian interference channel through the lens of a natural deterministic channel model. The main result is that the deterministic channel uniformly approximates the Gaussian channel, the capacity regions differing by a universal constant. The problem of finding the capacity of the Gaussian channel to within a constant error is therefore reduced to that of finding the capacity of the far simpler deterministic channel. Thus, the paper provides an alternative derivation of the recent constant gap capacity characterisation of Etkin, Tse and Wang. Additionally, the deterministic model gives significant insight towards the Gaussian channel. Copyright © 2008 John Wiley & Sons, Ltd. [source] Interpretation of the enhancement of field-scale effective matrix diffusion coefficient in a single fracture using a semi-analytical power series solutionHYDROLOGICAL PROCESSES, Issue 6 2009Tai-Sheng Liou Abstract A power series solution for convergent radial transport in a single fracture (PCRTSF) is developed. Transport processes considered in PCRTSF include advection and hydrodynamic dispersion in the fracture, molecular diffusion in the matrix, diffusive mass exchange across the fracture-matrix interface, and mixing effects in the injection and the extraction boreholes. An analytical solution in terms of a power series in Laplace domain is developed first, which is then numerically inverted by de-Hoog et al.'s algorithm. Four dimensionless parameters determine the behaviour of a breakthrough curve (BTC) calculated by PCRTSF, which are, in the order of decreasing sensitivity, the matrix diffusion factor, two mixing factors, and the Peclet number. The first parameter is lumped from matrix porosity, effective matrix diffusion coefficient, fracture aperture, and retardation factors. Its value increases as the matrix diffusion effect becomes significant. A non-zero matrix diffusion factor results in a , 3/2 slope of the tail of a log,log BTC, a common property for tracer diffusion into an infinite matrix. Both mixing factors have equal effects on BTC characteristics. However, the Peclet number has virtually no effect on BTC tail. PCRTSF is applied to re-analyse two published test results that were obtained from convergent radial tracer tests in a discrete, horizontal fracture in Silurian dolomite. PCRTSF is able to fit the field BTCs better than the original channel model does if a large matrix diffusion coefficient is used. Noticeably, the ratio of field-scale to lab-scale matrix diffusion coefficients can be as large as 378. This enhancement of the field-scale matrix diffusion coefficient may be ascribed to the presence of a degraded zone at the fracture-matrix interface because of karstic effects, or to flow channeling as a result of aperture heterogeneity. Copyright © 2009 John Wiley & Sons, Ltd. [source] Blind MIMO equalization with optimum delay using independent component analysisINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2004Vicente Zarzoso Abstract Blind space,time equalization of multiuser time-dispersive digital communication channels consists of recovering the users' simultaneously transmitted data free from the interference caused by each other and the propagation effects, without using training sequences. In scenarios composed of mutually independent non-Gaussian i.i.d. users' signals, independent component analysis (ICA) techniques based on higher-order statistics can be employed to refine the performance of conventional linear detectors, as recently shown in a code division multiple access environment (Signal Process 2002; 82:417,431). This paper extends these results to the more general multi-input multi-output (MIMO) channel model, with the minimum mean square error (MMSE) as conventional equalization criterion. The time diversity introduced by the wideband multipath channel enables a reduction of the computational complexity of the ICA post-processing stage while further improving performance. In addition, the ICA-based detector can be tuned to extract each user's signal at the delay which provides the best MMSE. Experiments in a variety of simulation conditions demonstrate the benefits of ICA-assisted MIMO equalization. Copyright © 2004 John Wiley & Sons, Ltd. [source] Closed-form expression for the BER of m-QAM-OFDM systems over time- and frequency-selective wireless channelsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2006F. Castells Abstract The broadcast DVB-T system is an m-QAM-OFDM communication system that includes pilot-symbol-assisted modulation (PSAM) in order to enhance channel estimation at the receiver. This characteristic makes DVB-T suitable for a mobile reception, over time- and frequency-selective wireless channels. In this work, a closed-form expression for the BER as a function of the transmission system, channel model and the channel estimation strategy employed at the receiver is derived. In addition, adjacent channel interference due to Doppler effects is also considered. The results are focused on the DVB-T system under different scenarios. The channel estimation at the receiver has been shown to be very critical, and the impact of channel estimation errors on the BER is analysed in detail. Copyright © 2005 John Wiley & Sons, Ltd. [source] Transmission on indoor power lines: from a stochastic channel model to the optimization and performance evaluation of multicarrier systemsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2003Virginie Degardin Abstract This paper deals with optimization and performance evaluation of multicarrier transmissions on indoor power lines, taking the actual channel characteristics into account. From intensive measurements of noise on lines, the most significant parameters of impulsive noise were defined and classified, and then a statistical study was carried out. The other types of noise, i.e. narrow band and coloured noise have also been characterized. In like manner, the transfer functions between two points of a power line network have been measured. From all these data, a stochastic channel model representative of the environment is built and implemented in a software tool simulating the link. Various transmission schemes have been considered to mitigate the effects on one hand of the stationary noise, the channel frequency selectivity and of the change of its state, and on the other, on the impulsive noise. These techniques are optimized for the indoor power line environment and their performances, expressed in terms of bit error rate, are compared. Copyright © 2003 John Wiley & Sons, Ltd. [source] The generalized Rice lognormal channel model,first and second order statistical characterization and simulationINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2002F. Vatalaro Abstract The Rice-lognormal (RLN) channel model was recently generalized to include an additive scattering component having constant average power. The generalized Rice-lognormal (GRLN) model includes as limiting cases many well-known narrowband models such as, e.g. Rice, lognormal (and combinations), and Loo's. The paper provides the GRLN first-order statistical description of envelope and phase, and the second-order statistics in terms of level crossing rate. The paper then provides a fitting procedure to extract model parameters from experimental data. Finally, it presents a new simulation procedure and validates it through comparison with theoretical results. Copyright © 2002 John Wiley & Sons, Ltd. [source] Vertical price leadership: A cointegration analysisAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 3 2002W. Erno Kuiper Here we detail a method to test whether or not retailers allow suppliers to set the wholesale price not only on the basis of the costs faced by the suppliers but also on the basis of consumer demand. Using standard theory, long-run price relationships between the stages in the channel are derived. Next, these static price relationships are imposed on a dynamic model to be tested for cointegration and long-run noncausality, embedding the hypotheses on vertical price leadership. To derive the testable implications of these hypotheses, we show that the common stochastic trend and long-run equilibrium error must explicitly be assigned to variables in the channel model. The model is particularly relevant for industries characterized by a low degree of product differentiation. An empirical application to two Dutch marketing channels for food products gives comprehensible results. [EconLit citations: C32, L12, Q11] © 2002 Wiley Periodicals, Inc. [source] Transient simulation of a catalytic converter for a dual fuel engineTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2000Benlin Liu Abstract An experimental and modelling study was performed for a catalytic converter attached to a natural gas/diesel dual fuel engine. The catalytic converter was a ceramic monolith honeycomb substrate coated with a washcoat of catalyst. A multiple segmented design of converter was used. This paper describes the application of a one-dimensional finite element model for the transient and steady state operation of this converter. The model is a single channel model. The laminar flow was approximated using a dispersed plug flow model. The chemical kinetics were simulated using LHHW type expressions. Comparison of simulated results are made with experimental results for heating and cooling cycles that resulted from speed and load changes on the engine. These comparisons showed a maximum difference between experimental and predicted emission levels of about 10%. On a mené une étude expérimentale et réalisé la modération d'un convertisseur catalytique relié è un moteur è combustible double gaz naturel/diesel. Le convertisseur catalytique est un substrat de monolithes céramique en nid d'abeille enduit d'une couche de catalyseur. Une conception segmentée multiple a étée utilisée pour le convertisseur. On décrit dans cet article l'application d'un modèle d'éléments finis unidimensionnel pour un fonctionnement en régime transitoire et permanent du convertisseur. Ce modèle est un modèle à canal unique. L'écoulement laminaire a été approximé à l'aide d'un modèle à écoulement piston dispersé. La cinétique chimique a été simulée au moyen d'expressions de type LHHW. On effectue une comparaison entre les résultats simulés et les résultats expérimentaux pour les cycles de chauffe et de refroidissement qui résultent des changements de vitesse et de charge sur le moteur. Ces comparaisons montrent une différence maximum entre les taux d'émission expérimentaux et prédits d'environ 10%. [source] Baroclinic development within zonally-varying flowsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 626 2007David M. Schultz Abstract Previous idealized-modelling studies have shown the importance of across-jet barotropic shear to the resulting evolution of cyclones, anticyclones, surface-based fronts, and upper-level fronts. Meanwhile, many observational studies of cyclones have shown the importance of along-jet variations in the horizontal wind speed (i.e. confluence and diffluence). This study investigates the importance of these along-jet (zonal, for zonally-oriented jets) variations in the horizontal wind speed to the resulting structures and evolutions of baroclinic waves, using idealized models of growing baroclinic waves. An idealized primitive-equation channel model is configured with growing baroclinic perturbations embedded within confluent and diffluent background flows. When the baroclinic perturbations are placed in background confluence, the lower-tropospheric frontal structure and evolution initially resemble the Shapiro,Keyser cyclone model, with a zonally-oriented cyclone, strong warm front, and bent-back warm front. Later, as the baroclinic wave is amplified in the stronger downstream baroclinicity, the warm sector of the cyclone narrows, becoming more reminiscent of the Norwegian cyclone model. The upper-level frontal structure develops with a southwest,northeast orientation, and becomes strongest at the base of the trough, where geostrophic cold advection is occurring. In contrast, when the baroclinic perturbations are placed in background diffluence, the lower-tropospheric frontal structure and evolution resemble the Norwegian cyclone model, with a meridionally-oriented cyclone, strong cold front, and occluded front. The upper-level frontal structure is initially oriented northwest,southeast on the western side of the trough, before becoming zonally oriented. Weak geostrophic temperature advection occurs along its length. These results are compared to those from previous observational and idealized-modelling studies. Copyright © 2007 Royal Meteorological Society [source] | ||||||||||