CiteULike: dcastro's model

A wideband channel model applicable to mobile satellite systems at L- and S-band

MAN Parks — 2008-07-15T14:02:11-00:00

Propagation Aspects of Future Mobile Systems (Digest No: 1996/220), IEE Colloquium on (1996), pp. 12/1-12/6.

In the near future, mobile satellite systems (MSS), providing worldwide voice and data communications are to come into service. As the demand for these services and the requirement for higher data rates and quality of service increases, the effects of the wideband mobile satellite propagation channel become more critical with respect to the overall system link budget. There is an increasing need to be able to accurately model the channel in order to optimise the design of radio mobile satellite systems. A wideband channel model has been developed based on the philosophy as the RACE ATDMA model. The model is of the tapped delay type, comprising a transversal filter structure with equidistant time shifted taps. The model parameters have been derived from the measurement campaign, and defined by a small number of discrete taps, where each tap is described by its complex time-varying amplitude including its statistical distribution and corresponding Doppler spectrum. A typical example is included of the tap amplitudes and statistical distributions from the measured data and the respective Doppler spectrum for the first tap (direct path) and the second tap (first multipath echo) in the model for the urban environment at 45° elevation angle. Additionally, the model has been validated against independent results published from the DLR measurement campaign

A new path-gain/delay-spread propagation model for digital cellular channels

LJ Greenstein — 2008-06-09T19:33:11-00:00

Vehicular Technology, IEEE Transactions on, Vol. 46, No. 2. (1997), pp. 477-485.

We derive a statistical model for the distribution of RMS delay spread (τ<sub>rms</sub>) within a cellular environment, including the effects of base-to-mobile distance, environment type (urban, suburban, rural, and mountainous areas), and the correlation between delay spread and shadow fading. We begin with intuitive arguments that τ<sub>rms</sub> should be lognormally distributed at any given distance d; that the median of this distribution should grow as some (weak) power of d and that the variation about the median should be negatively correlated with shadow fading gain. We then present empirical evidence, drawn from a wide array of published reports, which gives strong support to these conjectures. Finally, we combine our findings with the widely used model for path gain in a cellular environment. The result is a compact statistical model for the joint distribution of path gain and delay spread. The model lends itself readily to Monte Carlo simulation and is useful for performance studies of cellular systems with bandwidths up to tens of kilohertz

Measurement and modeling of land mobile satellite propagation at UHF and <e1>L</e1>-band

WJ Vogel — 2008-06-09T19:22:06-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 36, No. 5. (1988), pp. 707-719.

A propagation experiment is described in which a stratospheric balloon served as a transmitter platform at 870 and 1502 MHz in simulation of a land mobile satellite. A vehicle followed the drifting balloon along roads of western Texas and New Mexico, collecting at <e1>L </e1>-band amplitude and phase, and at UHF amplitude information only for elevation angles between 25° and 45°. The data obtained has been analyzed and is presented along with results from modeling of multipath scattering and roadside tree attenuation. The signal, with variations caused by multipath propagation and tree shadowing, was reduced by 3 dB at <e1>L</e1>-band and 2 dB at UHF for one percent of all locations. A median ratio of 3.9 was found between peak-to-peak phase (degrees) and power (dB) fluctuations. The ratio between <e1>L</e1>-band and UHF dB attenuation averages varied from 1.3 to 1.0 at fade levels from 6 to 23 dB. Optical sky brightness was measured and used to predict fade distribution with great accuracy. A single-scatterer multipath model is introduced. It is used to duplicate some of the measured data and to show the dependence of power variations on satellite elevation angle. Using Fresnel diffraction theory, the attenuation caused by a model tree was calculated to be near 10 dB and the maximum fade was found to increase by the logarithm of the number of branches

Channel modeling and simulation in satellite mobile communication systems

B Vucetic — 2008-06-09T19:22:04-00:00

Selected Areas in Communications, IEEE Journal on, Vol. 10, No. 8. (1992), pp. 1209-1218.

An analog model describing signal amplitude and phase variations on shadowed satellite mobile channels is proposed. A linear combination of log-normal, Rayleigh, and Rice models is used to describe signal variations over an area with constant environment attributes while an <e1>M</e1>-state Markov chain is applied to represent environment parameter variations. Channel parameters are evaluated from the experimental data and utilized to verify a simulation model. Results, presented in the form of signal waveforms, probability density functions, fade durations, and average bit and block error rates, show close agreement with measurements

Identification of Time-Varying Frequency-Flat Rayleigh Fading Channels Based on Errors-In-Variables Approach

A Jamoos — 2008-05-19T19:43:40-00:00

Signal Processing Advances in Wireless Communications, 2006. SPAWC '06. IEEE 7th Workshop on (2006), pp. 1-5.

This paper deals with the identification of time-varying frequency-flat Rayleigh fading channels disturbed by an additive white Gaussian noise, using a training sequence based approach. When the channel is modeled by an autoregressive (AR) process, it can be estimated by using a Kalman filter. However, this solution requires the preliminary unbiased estimations of the AR parameters and the variances of both the additive noise and the driving process in the state space representation of the system. Instead of using the existing noise compensated approaches which usually require a long observation window and do not necessarily provide reliable estimates when the signal to noise ratio is low, we propose an alternative approach using recent results developed for the errors-in-variables (EIV) issue. This method consists in estimating the kernel of specific autocorrelation matrices and has the advantage of providing both the noise variances and the channel AR parameters. Moreover, the maximum Doppler frequency can be also deduced

APPROXIMATION AND RESAMPLING OF TAPPED DELAY LINE CHANNEL MODELS WITH GUARANTEED CHANNEL PROPERTIES

Christian Mehlfuhrer — 2008-05-19T18:57:54-00:00

ICASSP (2008)

Design and Validation of Digital Channels for a Galileo Receiver Prototype

F Rossi — 2008-05-18T14:17:34-00:00

Digital System Design: Architectures, Methods and Tools, 2006. DSD 2006. 9th EUROMICRO Conference on (2006), pp. 545-549.

This paper describes the design activity for the digital baseband processing of a prototype receiver for the Galileo system. According to the applied hardware-software partitioning, the high rate elaborations have been implemented on a dedicated hardware, a Xilinx Virtex2 FPGA, while the remaining low rate processing has been programmed on an analog device DSP. A customarily designed prototype board has been used to validate the receiver under real working conditions: a dynamic GPS and Galileo scenario. Particularly, the paper focuses on the receiver digital channel, which is the critical core of the FPGA, from VHDL modeling to hardware implementation and testing

ADAPTIVE DECISION FEEDBACK EQUALIZER FOR SUI CHANNEL MODELS

B Zayen — 2008-05-18T12:50:14-00:00

Proceedings of EURASIP (2007)

A transmission line model for high-frequency power line communication channel

H Meng — 2008-05-16T12:02:03-00:00

Power System Technology, 2002. Proceedings. PowerCon 2002. International Conference on, Vol. 2 (2002), pp. 1290-1295 vol.2.

This paper presents a novel approach to modelling the transfer function of the broadband power line communication channel. In the approach, the power line is firstly approximated as a two-wire transmission line. The two intrinsic line parameters, the characteristic impedance and the propagation constant, are derived based on the transmission line theory. Then from the derived line parameters, an echo-based model is used to determine the transfer function for communication signals in the frequency range of 1 MHz-30 MHz. This approach reaps the advantages of accuracy and simplicity of the conventional modeling approaches.

Distributed channel model for HEMT signal and noise parameters

P Gardner — 2008-05-10T14:14:37-00:00

Electronics Letters, Vol. 28, No. 22. (1992), pp. 2063-2064.

A new simple model for the signal and noise properties of a microwave FET or HEMT avoids the need for any explicit correlation between gate and drain noise sources by distributing the drain-to-gate capacitance and the drain noise source along the conducting channel. The new model applied to a commercial HEMT chip demonstrates a very good fit to measured scattering and noise parameter data

HEMT models for S-parameter and noise parameter extrapolation

MT Hickson — 2008-05-10T00:03:25-00:00

Microwave Symposium Digest, 1992., IEEE MTT-S International (1992), pp. 277-280 vol.1.

Four models have been developed and assessed for fitting the measured noise parameters up to 26 GHz and S-parameters up to 400 GHz for a commercial HEMT (high electron mobility transistor) chip. The first treats the intrinsic noise sources as uncorrelated thermal sources. The second is an extension of this, allowing a better fit to be achieved by including the distributed nature of the gate and drain electrodes using a semidistributed, sliced model. The third model neglects the distributed effect but takes into account the partial correlation of the gate and drain noise sources. This causes a larger improvement in the quality of fit, allowing the model to fit the measured data within reasonable measurement limits. The addition of the distributed effect to the correlated model gives the fourth model, which allows a further marginal improvement, but the conditioning of the problem and the accuracy of the data appear to be insufficient to allow accurate extraction of the additional parameters needed

Modeling, analysis, and design of RF LDMOS devices using harmonic-balance device simulation

FM Rotella — 2008-05-09T16:40:12-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 48, No. 6. (2000), pp. 991-999.

This paper describes how device simulation may be used for the modeling, analysis, and design of radio-frequency (RF) laterally diffused metal-oxide-semiconductor (LDMOS) transistors. Improvements to device analysis needed to meet the requirements of RF devices are discussed. Key modeling regions of the LDMOS device are explored and important physical effects are characterized. The LDMOS model is compared to dc and small-signal ac measurements for calibration purposes. Using the calibrated model, large-signal accuracy is verified using harmonic distortion simulation, and intermodulation analysis. Predictive analysis and a study of the structure's parasitic components are also presented. Load-pull simulation is used to analyze matching network effects to determine the best choices for device impedance matching

A semidistributed HEMT model for accurate fitting and extrapolation of S-parameters and noise parameters

MT Hickson — 2008-05-09T15:16:17-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 40, No. 8. (1992), pp. 1709-1712.

A model is described for a low noise millimeter-wave HEMT device. It takes account of the distributed nature of the gate and drain electrodes by dividing the active region of the device into a number of slices. Each slice is modeled as an intrinsic HEMT with thermal noise sources and the slices are connected together through lossy reactances. The parameters of the first slice are made different from those of the remaining slices, in order to account for the inevitable differences in the field distribution in the gate feed region. The model parameters have been optimized numerically to fit the manufacturer's measured S-parameters and all four noise parameters, for a commercially available HEMT chip. A good fit has been achieved simultaneously to all of these parameters, and the model therefore provides a reasonable basis for extrapolation to higher frequencies. The significance of the distributed gate effect and the unequal slice effect is assessed by comparing the best fit achievable when these effects are not included

FDTD analysis of microwave active antenna including nonlinear model of FET transistor

Y Zhang — 2008-05-09T14:56:17-00:00

Microwave and Millimeter Wave Technology, 2002. Proceedings. ICMMT 2002. 2002 3rd International Conference on (2002), pp. 618-621.

In this paper, a non-linear circuit model of a FET has been incorporated into the finite-difference time-domain (FDTD) method when microwave active antennas are analysed. The FET, operating in class A mode, is biased and its non-linear properties (second harmonics) are investigated in a patch antenna configuration. The algorithm and the simulation results will be useful in the development of high power integrated active antenna modules.

An overview of the modelling of an active microstrip patch array

K Williams — 2008-05-09T08:35:37-00:00

Communications and Signal Processing, 1998. COMSIG '98. Proceedings of the 1998 South African Symposium on (1998), pp. 373-378.

This paper presents an overview of the use of the HP-EESof Communications Design Suite software and the finite-difference time-domain (FDTD) method for the analysis of an active microstrip patch array. The use of frequency- and time-domain simulation algorithms for the prediction of free-running and injection-locked oscillators is discussed. The modelling of the passive radiating part of the antenna using the FDTD method is covered. Free-running oscillators are shown to be handled accurately and efficiently using the harmonic-balance algorithm, but injection-locked oscillators are a source of difficulty. The FDTD method, when compared to measurements, gives good results for the input impedance and mutual coupling of the passive array

Modeling of active antenna array coupling effects-load variation method

S Sancheti — 2008-05-09T07:26:06-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 43, No. 8. (1995), pp. 1805-1808.

This paper presents a simple method for the calculation of the frequency and power variation of an active antenna operated in the presence of a reflecting surface. The situation modeled accounts for interdependent amplitude and phase dynamics and also allows for the extraction of active antenna array coupling coefficients. Analytical and experimental results are presented for both frequency and power variations of an individual element when operated in a strongly coupled imaged array environment. Here the nearest neighbor coupling is shown to be the dominant coupling mechanism

Mobile satellite propagation channel. Part II-a new model and its performance

A Mehrnia — 2008-05-08T08:48:32-00:00

Vehicular Technology Conference, 1999. VTC 1999 - Fall. IEEE VTS 50th, Vol. 5 (1999), pp. 2780-2784 vol.5.

In a companion paper (Mobile Satellite Propagation Channel, Part I-A Comparative Evaluation of Current Models) several models of the mobile satellite propagation channel were reviewed and their performances were compared by means of computer simulation and comparison with available empirical data. In this paper a new model which is a combination of N (Rice) and Q distributions is proposed and compared with the other mobile satellite channel models. A major conclusion is that this model has superior performance compared to other well-known models. The principles of the model and its capability in fitting empirical data are reported

Mobile satellite propagation channel. Part 1-a comparative evaluation of current models

A Mehrnia — 2008-05-08T08:47:11-00:00

Vehicular Technology Conference, 1999. VTC 1999 - Fall. IEEE VTS 50th, Vol. 5 (1999), pp. 2775-2779 vol.5.

In this paper major statistical propagation models of the mobile satellite channel are presented and their performances are evaluated by means of computer simulation and comparison with available empirical data. The comparison shows that Lutz provides the best fit to empirical data. After that, Nakagami, Corazza, Loo, and Norton are the better performance models, in the given order. In a companion paper, a flexible model of the channel, which is phenomenologically reasonable is proposed and its performance is compared with other available major channel models

The land mobile satellite communication channel-recording, statistics, and channel model

E Lutz — 2008-05-08T08:46:43-00:00

Vehicular Technology, IEEE Transactions on, Vol. 40, No. 2. (1991), pp. 375-386.

The communication channel between the MARECS satellite at 26°W and a cruising van was measured and recorded in European areas exhibiting satellite elevations from 13 to 43°. Different environments and mobile antennas were tested. The results of an extensive statistical evaluation include spectra of the fading amplitude; probability density, and distribution of the received signal power; and the percentage of time for fade and nonfade periods. Based on the physical phenomena of multipath fading and signal shadowing, an analog model of the land mobile satellite channel which can readily be used for software and hardware fading simulation is developed. The most important parameter of this model is the time-share of shadowing. The Rice factor which characterizes the channel during unshadowed periods, can vary from 3.9 to 18.1 dB. Block error probability density, error gap distribution, and block error probability are discussed

Land mobile satellite channel measurements and modeling

Chun Loo — 2008-05-08T08:45:42-00:00

Proceedings of the IEEE, Vol. 86, No. 7. (1998), pp. 1442-1463.

This paper, tutorial in nature, describes the effort of many investigators who have and still are conducting channel measurements and modeling for land mobile satellite communications. Various channel measurement results, ranging from ultrahigh frequency to Ka-band, are given. Many statistical channel models and simplified models that have been developed are referred to. Some of the models are applicable to geostationary and nongeostationary communications satellites. A statistical model developed by Loo (1985) is described in detail, as well as its extension to modeling land mobile satellite communications at Ka-band. This was accomplished by including a Gaussian probability density function to account for weather conditions. Also, practical computer-generated statistical channel models are given. These computer models should facilitate the estimation of performance of satellite communications systems

A high resolution model for the satellite-to-indoor channel

F Perez-Fontan — 2008-05-08T08:44:44-00:00

Position Location and Navigation Symposium, 2004. PLANS 2004 (2004), pp. 674-683.

In this paper measurements and modeling results obtained in the course of an European Space Agency, ESA, project (2002-2003) entitled "Navigation signal measurement campaign for critical environments" carried out by Joanneum Research (Austria) with subcontracts to DLR (Germany) and the University of Vigo (Spain), are presented.

A high resolution model for the aeronautical multipath navigation channel

A Steingass — 2008-05-08T08:44:22-00:00

Position Location and Navigation Symposium, 2004. PLANS 2004 (2004), pp. 357-365.

In this paper we present the results of satellite navigation multipath channel measurements for aeronautical applications. For the most critical scenario - the final approach, we derived a statistical channel model which we describe in detail.

A statistical model of flicker noise

JA Barnes — 2008-05-08T07:59:00-00:00

Proceedings of the IEEE, Vol. 54, No. 2. (1966), pp. 176-178.

By the method of fractional order of integration, it is shown that it is possible to generate flicker noise from "white" noise. A formal expression for the relation of flicker noise to white noise is given. An approximate method, amenable to the use of digital computers, is also given for the generation of flicker noise modulated numbers from random, independent numbers.

Incorporating the Fresnel Zone Theory in Ray Tracing for Propagation Modelling of Fixed Wireless Access Channels

Georgia Athanasiadou — 2008-04-20T16:25:30-00:00

Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on (2007), pp. 1-5.

A propagation model which combines the Fresnel zone theory and the ray tracing techniques is presented in this paper. The aim of this novel approach is a more accurate representation of the Fixed Wireless Access channel. Deterministic models do not consider power loss when the radio waves propagate close to roof tops. However, according to the theory of the Fresnel zones, even when there is line-of-sight (LOS), the loss can be as much as 6dB due to a single obstacle just below the LOS. In the model presented here, the path of each ray is found by a three-dimensional (3D) ray tracing algorithm and the electromagnetic field of each ray is calculated according to Geometric Optics (GO) and the Uniform Theory of Diffraction (UTD). The first Fresnel zone of each ray is also found and examined and the losses due to its partial blockage are taken into account. Simulation results show significant differences in the power predictions when the blockage of the Fresnel zones is considered.

Multipath channel models for wireless local and metropolitan area networks

K Jeong — 2008-04-15T17:51:06-00:00

Information Technology and Applications, 2005. ICITA 2005. Third International Conference on, Vol. 2 (2005), pp. 295-298 vol.2.

Wideband mobile radio channel characteristics were measured in various environments in Korea. SKT conducted impulse response measurements at 2.3 GHz with a commercial channel sounder and presents multipath channel models for wireless local and metropolitan area networks. In this paper, we describe the process to analyze the measured data and build tapped delay line channel models. The whole measurements were conducted throughout more than 25 sites around Seoul city and various channel models that represents rural, suburban, suburban alternative, micro-cell hilly, urban high-rise and urban rooftop environments are presented.

System and Circuit Models for Microwave Antennas

MI Sobhy — 2008-04-15T17:39:59-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 55, No. 4. (2007), pp. 729-735.

This paper describes how circuit and system models are derived for antennas from measurement of the input reflection coefficient. Circuit models are used to optimize the antenna performance and to calculate the radiated power and the transfer function of the antenna. System models are then derived for transmitting and receiving antennas. The most important contribution of this study is to show how microwave structures can be integrated into the simulation of digital communication systems. This enables system designers to predict the effect of the microwave subsystem on the digital signals and calculate the resulting bit error rate

Spread-spectrum ranging multipath model validation

MS Braasch — 2008-04-15T12:42:14-00:00

Aerospace and Electronic Systems, IEEE Transactions on, Vol. 37, No. 1. (2001), pp. 298-304.

Spread-spectrum ranging multipath model validation results are presented. Previously published theoretical results are compared with data obtained from bench-testing using a multichannel satellite simulator. Results are presented for standard or wide-correlator (i.e., 1 chip early-to-late correlator spacing) and narrow-correlator (i.e., 0.1 chip) GPS C/A-code architectures as well as standard P-code. The close agreement of the bench data and theoretical results confirm the validity of the theoretical model

GPS multipath model validation

MS Braasch — 2008-04-15T12:40:21-00:00

Position Location and Navigation Symposium, 1996., IEEE 1996 (1996), pp. 672-678.

Multipath represents the dominant error source in satellite-based precision guidance systems. Since multipath errors are not common to the reference station and remote receivers, they are not eliminated through differential corrections and they do not cancel out in a differential carrier-phase tracking system. For precision approach applications, multipath is the most significant obstacle to overcome in the quest for CAT III accuracy and integrity using code-DGPS. Although a multitude of GPS articles discuss the effects of multipath, few derive the basic relationships between the composite signal at the antenna and the resulting measurement error. Furthermore, no validation of the aforementioned theory has been performed to date. This paper presents a comprehensive treatment of the problem. The traditional theoretical multipath error relationships are presented along with validation results obtained from bench-testing using a multichannel satellite simulator. Results are presented for standard and narrow-correlator C/A-code architectures as well as standard P-code. One result of particular interest to the aviation community is validation of the theoretical results which indicate that airframe-based multipath error cannot be reduced with narrow-correlator or P-code technology

Channel modeling for ad hoc mobile wireless networks

R Wang — 2008-04-15T10:37:07-00:00

Vehicular Technology Conference, 2002. VTC Spring 2002. IEEE 55th, Vol. 1 (2002), pp. 21-25 vol.1.

Fading is fundamentally different in ad hoc and cellular mobile wireless networks. Herein we show a way to simulate small-scale and large-scale fading on links in an ad hoc network and present simulation results for a multipath shadowed outdoor environment. We study fundamental discrepancies between ad hoc and cellular networks and find that link performance is worse for the ad hoc case, but, more interestingly, the performance gap shrinks with "increased mobility".

Unified channel model for mobile radio systems with smart antennas

J Fuhl — 2008-02-28T18:54:16-00:00

Radar, Sonar and Navigation, IEE Proceedings -, Vol. 145, No. 1. (1998), pp. 32-41.

The definition of flat fading and frequency-selective fading channels is extended to low-rank and high-rank channels to include the angular domain. By physical reasoning a generic channel model is introduced incorporating directions of arrival and a set of parameters is given for its configuration. The time evolution of the scattering processes and directions of arrival is taken into account. Analytical expressions are derived for space-correlation coefficients and frequency-correlation coefficients. Spatial correlation decreases with increasing angular spread and decreasing angle of incidence, measured from a array broadside

Simple model for the input impedance of coax-fed rectangular microstrip patch antenna for CAD

F Abboud — 2006-09-05T05:12:09-00:00

Microwaves, Antennas and Propagation, IEE Proceedings H, Vol. 135, No. 5. (1988), pp. 323-326.

The authors present a simple model for the input impedance of a rectangular microstrip patch antenna. This model is well suited for computer aided design (CAD). It is based on classical methods: (a) the cavity model determining the frequency and the input resistance at resonance, (b) the dynamic permittivity of a rectangular microstrip path antenna (to take into account the influence of the fringing field at the edges of the rectangular patch antenna) and (c) the resonant parallel RLC circuit with an inductive reactance. This model is valid for electrically thick substrates. The theoretical results are in good agreement with experimental data.<<ETX>>

Propagation models for short-range wireless channels with predictable path geometries

A Domazetovic — 2008-04-10T06:25:28-00:00

Communications, IEEE Transactions on, Vol. 53, No. 7. (2005), pp. 1123-1126.

We consider wireless data services characterized by short distances, no shadowing, low power, and low antenna heights, deployed in places where a high frequency of potential users is expected, e.g., toll booths, parking lots, intersections, etc. Within such a system, we expect to see a well-defined geometry of base-to-user radio paths, as well as a predictable user trajectory, neither of which can be assumed for the wide-area cellular case. This offers the promise of a strong deterministic component of the channel response, in addition to a weaker stochastic component. Here, we combine analysis of the former with measurements and modeling of the latter for three typical outdoor scenarios. Comparisons between predicted and measured behavior show excellent agreement.

A Multipath RF Propagation Model for Computer Simulation of Complex Impulse Responses of Broadcast Teletext Channels

M Sablatash — 2008-04-10T06:22:13-00:00

Selected Areas in Communications, IEEE Journal on, Vol. 5, No. 2. (1987), pp. 286-298.

To accurately predict the performance of broadcast teletext systems, one must know the characteristics of typical over-the-air broadcast television channels. Consequently, ensembles of typical complex impulse responses of broadcast teletext channels in the VHF and UHF frequency ranges are required for computer performance simulations. To circumvent the lack of comprehensive measured channel data, a theoretical multipath propagation model for suburban and urban environments was developed to gain insight into the nature of typical television multipath channels. In this model, both the direct and scatter paths consist of a line-of-sight and ground-reflected component. The basis of the propagation model is an expression for the ratio of the scattered path to direct path field strength caused by vertically oriented dielectric slabs of specified thickness, height, and width. The reflector location, orientation, width, height, and thickness are randomized for each Monte Carlo simulation cycle. A scatter table of relative amplitude versus multipath delay is maintained for subsequent analysis and formation of typical multipath channel impulse responses. A perceived desired-to-undesired ratio (PDUR), which is essentially a signal-to-clutter ratio, is computed to eliminate channels of unacceptable video quality, as these would be of no interest to the teletext application. A modification to account for near-field scattering is described. Finally, mobile channel applications are discussed.

Monte-Carlo multipath simulation of ray tracing channel models

A Muller — 2008-04-09T09:03:43-00:00

Global Telecommunications Conference, 1994. GLOBECOM '94. 'Communications: The Global Bridge'., IEEE, Vol. 3 (1994), pp. 1446-1450 vol.3.

This paper addresses the simulation of multipath propagation on indoor radio channels. In particular, we study extremely high frequencies (60 GHz), where the common WSSUS model suffers from spatial limitations. We introduce a new approach to channel modeling. A statistical channel model is derived from a deterministic ray tracing description of the multipath situation by a tolerance analysis. Further, we show that such a model can be used for channel simulation by extending the Monte-Carlo method, which has been introduced for the simulation of WSSUS channels. An example of a 60 GHz indoor channel simulation is included

Modeling and simulation of integrated capacitors for high frequency chip power decoupling

E Diaz-Alvarez — 2008-04-08T06:46:46-00:00

Components and Packaging Technologies, IEEE Transactions on [see also Components, Packaging and Manufacturing Technology, Part A: Packaging Technologies, IEEE Transactions on], Vol. 23, No. 4. (2000), pp. 611-619.

Power and ground decoupling is typically accomplished using a hierarchy of discrete capacitors spread throughout the power distribution network. Many of the limitations of discrete decoupling capacitors can be overcome with integrated capacitors. A modeling approach for integrated capacitors based on the partial-element-equivalent-circuit (PEEC) formulation is presented. This approach has been applied to 3M C-ply, a flexible planar integrated capacitor technology that can be laminated into multilayer substrates, such as printed wiring boards. The decoupling capability of 3M C-Ply technology for chip power distribution has been compared with conventional surface-mount technology (SMT)

Including Diffuse Multipath Parameters in MIMO Channel Models

Nicolai Czink — 2008-02-26T19:21:14-00:00

Vehicular Technology Conference, 2007. VTC-2007 Fall. 2007 IEEE 66th (2007), pp. 874-878.

GPS Ionospheric Error Correction Models

R Filjar — 2008-02-21T15:49:54-00:00

Multimedia Signal Processing and Communications, 48th International Symposium ELMAR-2006 focused on (2006), pp. 215-217.

Ionospheric errors are the most influential source of the GPS positioning errors. In an attempt to at least partially improve the GPS positioning process, a global ionospheric correction model is introduced within the standard GPS positioning service. Referred to as the Klobuchar model after its inventor, this model appeared as a compromise between computation complexity and correction accuracy. Unfortunately, the Klobuchar model is capable of correcting up to 70% of ionospheric errors, with particularly poor performance during severe ionospheric disturbances. Wide implementations of satellite navigation systems (GPS in particular) in modern technical systems call for better corrections of the ionospheric influence. This article presents three essential approaches in modelling the GPS ionospheric errors (physical, empirical and dynamic models) and discusses their implementation in GPS-based technical systems

A wave-based wideband MIMO channel modeling technique

H Xu — 2008-02-19T08:19:21-00:00

Personal, Indoor and Mobile Radio Communications, 2002. The 13th IEEE International Symposium on, Vol. 4 (2002), pp. 1626-1630 vol.4.

The paper presents a multiple-input-multiple-output (MIMO) channel modeling technique for link level and system level simulations. The classical approach of wave superposition is adopted to generate MIMO channels that are statistically consistent in delay, frequency and angle domains. The paper proposes an efficient way to generate four dimensional MIMO channel transfer matrices based on standard channel statistics such as power delay profile (PDP) and power azimuth spectrum (PAS).

A new model for calculating the input impedance of coax-fed circular microstrip antennas with and without air gaps

F Abboud — 2008-01-02T12:59:00-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 38, No. 11. (1990), pp. 1882-1885.

A model is presented for calculating the input impedance of a probe-fed circular antenna with and without air gaps between the substrate and the ground plane. It is based on the cavity method, the dynamic permittivity constant (to take into account the influence of the fringing field at the edge of radiating element), and the resonant parallel <e1>R</e1>-<e1>L</e1>-<e1>C</e1> circuit with an inductive reactance. Numerical results are shown to agree well with experimental ones. The model is well suited for computer-aided design

Equivalent Circuit Model Proposal Applied to Frequency Selective Surfaces

L Fernandez-Martinez — 2008-01-01T19:35:38-00:00

Applied Electromagnetics and Communications, 2005. ICECom 2005. 18th International Conference on (2005), pp. 1-4.

Frequency Selective Surfaces's (FSS's) representation with an equivalent circuit composed of lumped elements is very useful in the design stage, where it is desirable to know in a quick way if a FSS is able to give a fixed frequency response. The final aim will be to obtain an equivalent circuit that fits the simulated FSS response with the proposed LC circuit. The method will be validated with a metallic ring on a dielectric substrate.

A realistic two-lane traffic model for highway traffic

W Knospe — 2007-12-06T16:56:53-00:00

Journal of Physics A: Mathematical and General, Vol. 35, No. 15. (2002), pp. 3369-3388.

A two-lane extension of a recently proposed cellular automaton model for traffic flow is discussed. The analysis focuses on the reproduction of the lane usage inversion and the density dependence of the number of lane changes. It is shown that the single-lane dynamics can be extended to the two-lane case without changing the basic properties of the model, which are known to be in good agreement with empirical single-vehicle data. Therefore it is possible to reproduce various empirically observed two-lane phenomena, like the synchronization of the lanes, without fine tuning of the model parameters.

Channel estimation for OFDM transmission in multipath fading channels based on parametric channel modeling

Baoguo Yang — 2007-11-28T10:30:31-00:00

Communications, IEEE Transactions on, Vol. 49, No. 3. (2001), pp. 467-479.

We present an improved channel estimation algorithm for orthogonal frequency-division multiplexing mobile communication systems using pilot subcarriers. This algorithm is based on a parametric channel model where the channel frequency response is estimated using an L-path channel model. In the algorithm, we employ the ESPRIT (estimation of signal parameters by rotational invariance techniques) method to do the initial multipath time delays acquisition and propose an interpath interference cancellation delay locked loop to track the channel multipath time delays. With the multipath time delays information, a minimum mean square error estimator is derived to estimate the channel frequency response. It is demonstrated that the use of the parametric channel model can effectively reduce the signal subspace dimension of the channel correlation matrix for the sparse multipath fading channels and, consequently, improve the channel estimation performance

A general-purpose circuit model of interdigital capacitor for accurate design of low-loss microstrip circuit

Lei Zhu — 2007-11-27T10:24:18-00:00

Microwave Symposium Digest, 1998 IEEE MTT-S International, Vol. 3 (1998), pp. 1755-1758 vol.3.

A general-purpose CAD-oriented circuit model is presented for accurately modeling interdigital capacitor (IDC) in optimized design of low-loss IDC-related microstrip circuits. This equivalent model is formulated as an admittance-based π-network through the use of a so-called “Short-Open Calibration (SOC)” technique for extracting precisely circuit parameters from a fullwave method of moments (MoM). A J-inverter based topology is further developed for explicit characterization of IDC-related coupling characteristics that accounts for frequency dispersion and fringing effect. Extracted model parameters are given for two types of IDC structure and the model accuracy is well validated by our experiments for an IDC-related quasi-lumped bandpass filter

Corrections to "accurate circuit model of interdigital capacitor and its application to design of new quasi-lumped miniaturized filters with suppression of harmonic resonance"

Lei Zhu — 2007-11-27T10:23:01-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 10. (2002), pp. 2412-2413.

Propagation measurements and models for wireless communications channels

JB Andersen — 2007-07-23T09:55:26-00:00

Communications Magazine, IEEE, Vol. 33, No. 1. (1995), pp. 42-49.

The authors describe the type of signals that occur in various environments and the modeling of the propagation parameters. Models are essentially of two classes. The first class consists of parametric statistical models that on average describe the phenomenon within a given error. They are simple to use, but relatively coarse. In the last few years a second class of environment-specific models has been introduced. These models are of a more deterministic nature, characterizing a specific street, building, etc. They are necessarily more time consuming to use, but are also more revealing concerning physical details and hopefully more accurate. Some key parameters and the measurement of them are discussed and then the different wireless environments are treated. The latter topic is divided into outdoor environments, indoor environments, and radio penetration from outdoor to indoor environments

A stochastic model of the temporal and azimuthal dispersion seen at the base station in outdoor propagation environments

KI Pedersen — 2007-11-16T08:09:02-00:00

Vehicular Technology, IEEE Transactions on, Vol. 49, No. 2. (2000), pp. 437-447.

A simple statistical model of azimuthal and temporal dispersion in mobile radio channels is proposed. The model includes the probability density function (PDF) of the delay and azimuth of the impinging waves as well as their expected power conditioned on the delay and azimuth. The statistical properties are extracted from macrocellular measurements conducted in a variety of urban environments. It is found that in typical urban environments the power azimuth spectrum (PAS) is accurately described by a Laplacian function, while a Gaussian PDF matches the azimuth PDF. Moreover, the power delay spectrum (PDS) and the delay PDF are accurately modeled by an exponential decaying function. In bad urban environments, channel dispersion is better characterized by a multicluster model, where the PAS and PDS are modeled as a sum of Laplacian functions and exponential decaying functions, respectively

A statistical discrete-time model for the WSSUS multipath channel

P Hoeher — 2007-11-15T13:35:03-00:00

Vehicular Technology, IEEE Transactions on, Vol. 41, No. 4. (1992), pp. 461-468.

The computation of the tap gains of the discrete-time representation of a slowly time-varying multipath channel is investigated. Assuming the channel is wide-sense stationary with uncorrelated scattering (WSSUS), a known Monte Carlo based method approximating the given scattering function (which fully determines the WSSUS channel) is extended by including filtering and sampling. The result is a closed-form solution for the tap gains. This allows the efficient simulation of the continuous-time channel with, e.g., only one sample per symbol, and without explicit digital filtering

Propagation channel models for mobile communication

Patrice Pajusco — 2007-11-15T10:26:30-00:00

Comptes Rendus Physique, Vol. 7, No. 7. (September 2006), pp. 703-714.

Propagation channel properties influence the development of wireless communication systems. During system design, channel properties are required to choose the suitable air interface (modulation, coding and access scheme). Comparisons and assessment of different solutions are performed using wideband propagation channel models. During network planning, prediction channel models provide valuable inputs to optimize network parameters. This article aims to present a short overview of these different propagation channel models. To cite this article: P. Pajusco, C. R. Physique 7 (2006).

Radio frequency channel modeling for proximity networks on the Martian surface

Vishwanath Chukkala — 2007-11-12T14:25:38-00:00

Computer Networks, Vol. 47, No. 5. (5 April 2005), pp. 751-763.

NASA's long-term goals for the exploration of Mars include the use of rovers and sensors which communicate through proximity wireless networks. The performance of any such wireless network depends fundamentally on the radio frequency (RF) environment. In order to evaluate and optimize the performance of such a wireless network, a basic understanding or model of the channel is important. In this paper, we present our results concerning the RF environment at selected sites on the surface of Mars with a focus on the link budget and RF coverage patterns. These results take into account the local topography using data from the Mars Global Surveyor, surface reflections, clutter, atmospheric absorption, etc., and contribute to a more accurate RF channel model. We consider a basic wireless network model and demonstrate the possibility for good site coverage and long links despite low antenna heights and radiated power. With such a channel model, mission operators can update elements of the wireless network after deployment with more accurate RF propagation information. Such updates could be used to extend the reach of the network or protect network elements from communication outages due to unforeseen features of the local topography.

Nonlinear prediction of mobile radio channels: Measurements and MARS model designs

T Ekman — 2007-11-12T14:11:14-00:00

(1999)

The rapid time variation of mobile radio channels is often modeled as a random process with second order moments reflecting vehicle speed, bandwidth and the scattering environment. These statistics typically show that there is little room for prediction of channel properties such as received power or complex taps of the impulse response coefficients, at least when linear predictor structures are considered. We use mutual information estimation to measure statistical dependencies in sequences of ...