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On-body communication channels are of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper describes investigations into channel characterization and antenna performance at 2.45 GHz. It is shown that significant channel fading occurs during normal activity, due primarily to the dynamic nature of the human body, but also due to multipath around the body and from scattering by the environment. This fading can be mitigated by the use of antenna diversity, and gains of up to 10 dB are obtained. Separation of the antenna's performance from the channel characteristics is difficult, but results show that for many channels, an antenna polarized normal to the body's surface gives the best path gain. Simulation and modeling present many challenges, particularly in terms of the problem's scale, and the need for accurate modeling of the body and its movement. [ABSTRACT FROM AUTHOR]

In this paper, we present results from a joint oceanographic-acoustic study of solitary, waves and their effects during the 1997 winter PRIMER4 experiment on the shelfbreak south of Cape Cod, MA. The study addresses the acoustic effects induced by solitary waves and associated oceanographic phenomena. Solitary wave generation and propagation simulations are produced by the Lamb model [J. Geophys. Res., vat. 99, pp. 848-864, 1994]. The model is nonhydrostatic and is formulated in 2.5 dimensions using terrain following coordinates. Acoustic field calculations are performed with a parabolic equation acoustic model along the path of solitary wave train propagation. The oceanographic model is initialized from density profiles derived from conductivity-temperature-depth (CTD) casts using analytical functions. The model is forced with a prescribed semidiurnal tidal velocity. An ocean background current is introduced. Simulations based on parameters derived from measurements show the following: 1) internal solitary waves of elevation propagate onto the shelfbreak region; 2) opposing ocean currents enhance the formation of solitary waves at the shelf break; 3) deepening of the winter mixed layer results in less penetration of the solitary waves on to the shelf; 4) density structure, mixed-layer depth, tidal forcing, and ocean currents control the formation of solitary waves of elevation at the shelfbreak: 5) energy conversion, from semidiurnal barotropic to semidiurnal barcoclinic tides and to internal solitary waves, occurs: 6) amplitudes and periods of modeled solitary waves are in the range of thermistor chain measurements; and 7) lower mixed-layer densities increase the phase speed of simulated solitary waves. Acoustic field calculations are coupled to the propagation of the solitary wave packets through the sound-speed changes that are derived from the oceanographic simulations. Acoustic model predictions show signal intensity fluctuations similar to the anomalous loses in acoustic energy observed in the Yellow Sea data taken by Zhou et aL [J. Acoust. Soc. Amer., vol. 90, pp. 2042-2054, 1991]. In some cases, the presence of solitary waves on the shelf enhances the propagation of acoustic energy onto the shelf. This was observed for acoustic simulations where the acoustic source was located beyond the shelfbreak and at a depth greater than the shelf depth. [ABSTRACT FROM AUTHOR]

This paper presents a ray-tube tracing method to simulate waves propagating in curved road tunnels from base stations for mobile communications. Ray tubes are traced by including multiple reflections in the curved tunnels and diffractions from wedges of the tunnel structures, together with the direct path. To verify this ray-tube tracing approach, field measurements of 900 MHz signals in two curved road tunnels from GSM base stations were performed for comparisons with the ray-tube tracing simulations. By tracing ray tubes reflected and diffracted from the curved structures of the tunnels, the effects of the curvature on wave propagations in large guiding structures can be evaluated. Good agreement between simulations and measurements has been obtained. A parametric study of the influence of the tunnel geometry and the signal frequency on the path loss is also presented by applying this ray-tube tracing method. Curved tunnels for different radii of curvature in the tunnel cross-section and horizontal plane and also lengths of the curved part are compared, together with rectangular tunnels. Simulations of the field distribution over the cross-section of the curved tunnel away from the transmitting antenna are demonstrated as well. The ray-tube tracing program can be applied to determine the deployment of the base-station antennas for improving signal coverage in tunnels, which may have curved structures. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new empirical formula for handover rate as a function of base stations separation, standard deviation of shadow fading, path loss exponent, averaging distance, and correlation distance. The handover initiation algorithm is based on averaged signal strength measurements using relative signal strength with hysteresis margin approach. We generate the data through computer simulations for the average number of handovers referred to as handover rate, for the practical range of path loss exponent and standard deviation of shadow fading. The proposed formula provides for a practical design tool to optimize the handover initiation performance under varied propagation environments. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we propose a novel propagation model for the uncertainty in the reference pixels and the model-based improved intra-refreshment method for the H.264 streaming service through the error-prone channel. The proposed intra-refreshment algorithm can incorporate with the SAD-based low-complexity mode decision as well as the RD-optimizing high-complexity mode decision. Simulations on RTP/IP transmission over mobile channels with the 42.7 and 85.3kbps encoding of QCIF 30 frames/s sequences show that the proposed intra-refreshment scheme improves the average quality of decoded pictures by 1.36–0.47dB compared with the conventional periodic GOB refreshment algorithms. [Copyright &y& Elsevier]

Experimental results for the demonstration of backward-wave or double-negative (DNG) propagation in waveguide technology combining inductive windows and split-ring resonators are presented and discussed in depth. A novel segmented prototype has been designed, fabricated, and measured, thus allowing the analysis and discussion of different length structures. The experimental characterization proves the DNG nature of the devices by comparing the phase of the transmission coefficient S21 for different length structures. Dielectric and metallic losses linked to the resonators also limit the transmission levels of these very compact structures in the longitudinal dimension, and the sources of such losses are interpreted through the comparison of measured results with full-wave electromagnetic simulations. [ABSTRACT FROM AUTHOR]

This article introduces a simple MATLAB radiowave propagation package, SSPE_GUI, for the visualization of EM propagation over non-fiat terrain through an inhomogeneous atmosphere, for waves radiated by a horizontally oriented antenna over the ground. The package can be used as an engineering tool to test the effects of various user-specified longitudinal terrain profiles and refractivity variations, as well as guiding and anti-guiding conditions on radiowave propagation, especially for GSM rural coverage planning. It can also be used as an educational aid (virtual tool) in EM lectures, for example, in antennas and propagation, wireless communication, etc. [ABSTRACT FROM AUTHOR]

We discuss an electronic circuit that simulates wave propagation in dispersive media. The circuit is an array of phase shifters composed of operational amplifiers. The envelope of the simulated light pulse can be described by a discretized version of the one-dimensional wave equation. The circuit can be used to change the group velocity both spatially and temporally and emulate slow light or stopped light. The control of the group velocity of optical pulses is expected to be a useful tool for quantum information and communication. [ABSTRACT FROM AUTHOR]

The analysis of n-coupled transmission lines with nonuniform cross-section is often necessary in the design and simulation of high-speed integrated circuits. A new modal analysis technique is presented, illustrating how a 2n-port coupled nonuniform line structure can be broken down into a set of n uncoupled 2-port nonuniform lines. Modal propagation parameters and modal transformation matrices are retrieved from the entries of the ABCD-matrix representation of the n-coupled line structure. An application concerning a tapered transmission-line system typically found in chip-carrier interconnections is provided as an example. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 186–189, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20415 [ABSTRACT FROM AUTHOR]

In this paper, an efficient numerical simulation technique is introduced to extract the propagation characteristics of interconnects over lossy substrate structures. This approach is based on a compact-form FDFD method in conjunction with the two-step Lanczos (TSL) technique. The efficiency and accuracy of the algorithm are demonstrated through the simulation of several lossy transmission-line structures. [ABSTRACT FROM AUTHOR]

In downlink communication of a direct-sequence (DS) code-division multiple-access (CDMA) system, each user's short spreading codes are superimposed by base station's common long codes. This situation creates much difficulty in blind signal detection when multipath propagation occurs. However, when spatial/temporal diversity is available at the receiver, it is shown in this paper that subspace technique can be directly applied to estimate the common downlink multipath channel. Then, typical linear receivers, such as zero-forcing (ZF), minimum mean-square-error (MMSE) and RAKE receivers can be designed to detect to desired signal. Since the data covariance matrix is used but estimated from finite data samples, performance of both channel estimator and receivers gets perturbed. It is thus thoroughly and jointly analyzed by perturbation analysis. Justification of analysis and comparison of different receivers are also made through simulations. [ABSTRACT FROM AUTHOR]

This paper considers the propagation model in which the amplitude of the direct wave is kept constant and that of the indirect wave exhibits Rayleigh fluctuations in the line-of-sight and non-line-of-sight channels. The instantaneous received signal level distribution is examined by computer simulation and a fading simululator, with the equivalent received bandwidth (product of received bandwidth 2Δf and maximum path length difference ΔLmax) as the propagation parameter. It is seen that the equivalent received bandwidth is suited as a parameter to represent the instantaneous received signal level distribution. The instantaneous received signal level distributions derived by the computer simulation and the fading simulator agree well. Conventional narrow-band transmission corresponds to the case in which 2ΔfΔLmax is less than 10 MHz-m. Then, the fading depth is determined by the power ratio a between the direct wave and the indirect wave. Wide-band transmission corresponds to the case in which 2ΔfΔLmax is larger than 10-MHz-m. Then, the fading depth is determined by a and 2ΔfΔLmax, becoming less when those quantities are increased. When 2ΔfΔLmax is very large, the fading depth also depends on the number of arriving waves. These properties are derived theoretically and are verified by the simulation and the fading simulator. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(2): 94–105, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1157 [ABSTRACT FROM AUTHOR]

Deals with the use of a time-domain (TD) analysis for the prediction of radio wave propagation for wireless communications in urban environments. Comparison between measured propagation data and predictions given by a polygonal line (PL) simulator; Purpose of the TD analysis; Appraisal of predictions obtained with the PL simulator.

Proposes a ray-tracing approach for indoor and outdoor radio wave propagation through window structures. Results of the finite-difference time-domain method for the propagation; Description of a ray-tracing algorithm; Characteristics of a ray-optics window model.

Presents a ray-tracing procedure based on a triangular grid approach for predicting the propagation of radio waves in urban environments. Facts on the two-dimensional triangulation of propagation environments; Description of a ray-tracing algorithm; Comparison of simulations for radio wave propagation.

Considers scaled models of two-dimensional urban environments in order to investigate radio wave propagation along a vertical plane. Description of a polygonal line simulator; Comparisons on ray-tracing propagation simulation; Types of polygonal shapes examined to test the performance of the polygonal line simulator.

Examines the influence of a diffraction coefficient and building corner shape on predicting the propagation of radio waves in urban environments. Formulation of the diffraction coefficient; Information on a vertical plane launch ray tracing algorithm used in predicting the propagation; Description of a wide-band measurement system.

In this paper, the simulation of general frequency-dependent magnetoelectric material properties in time-domain TLM is described. The formulation is developed from Maxwell's equations and the constitutive relations using bilinear 𝒵-transform methods leading to a general Padé system. The approach is applicable to all frequency-dependent linear materials including those displaying anisotropic and bianisotropic behaviour. The method is validated by the example of a chiral slab having an analytic solution. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Presents a study which examined wet antenna attenuation during rain events. Methodology; Measured wet antenna characteristics; Path-attenuation statistics.

Presents a channel parameter simulation for wave propagation in a forest environment. Overview of the forest model; Details on the problems; Fast-field calculations based on reciprocity; Near-field calculation.

Describes a laboratory model designed to investigate radio wave propagation in the perturbed environment of the earth-ionosphere waveguide. Properties of Maxwell's equations involved in the construction of the model; Overview on the problem; Electromagnetic models; Conclusions.

Provides information on a study which proposed two phase models for the wide-band indoor radio propagation channel. Modeling of phase; Comparative evaluations; Simulation algorithms used.

Presents information on a study which used the Green's function or propagator of the advection-diffusion equation to link the transilient matrix to the equation. Some issues on meteorology; Development of the Green's function framework; Conclusions.

Describes a simulator, called PROSIM (PROpagation SIMulator), developed at Virginia Technology for simulating propagation conditions on land mobile links to geostationary earth orbit (GEO) satellites. Brief information on land mobile satellite systems (LMMS); Physics and statics of mobile satellite propagation; Description of a numerical propagation model.

The level of details for choosing a simulator has provided by experience of wired network. Wireless simulation raise many new questions about appropriate level of detail in simulation model for radio propagation and energy consumption. As we have many simulation tools which are easily available openly like OMNeT++, QualNet and Ns2 but each has its own limitation. Where as Matlab is an emerging computing tool provide wide variety of functional toolboxes and easy to use language. In this paper a simulation model for wireless network using Matlab is implemented and there execution timings are also compared to check the effectiveness. [ABSTRACT FROM AUTHOR]

Indoor propagation is conducted in an experimental room, in order to estimate the setting absorber for an improved wireless LAN communication environment. Comparison of well reflected environment, replacing of one side wall to the developed absorber makes the average delay profile half, and further replacing of ceiling makes that 1/4. Simulation using the ray-tracing method is also performed to confirm the effectiveness. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 226–228, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20425 [ABSTRACT FROM AUTHOR]

The uniform geometrical theory of diffraction and ray tracing technique is used to simulate ultra wideband signal multipath propagation characteristics. The simulation model covers indoor office and outdoor corridor with thick wall and metal doors. The range of path loss exponent of distance is obtained by regression analysis, and the lognormal distribution about shadowing fading is got by the fitting and test. The distance-dependence path loss in the indoor and indoor to the corridor present lognormal distribution characteristics. Through the comparative research, the signal of the transmission metal door has a decisive influence on the corridor environment. [ABSTRACT FROM AUTHOR]

A new distance-aware broadcasting algorithm was proposed to enhance the propagation distance in the latency time of safety-related message broadcasting. The IEEE 802.11p standard states that if the medium is detected as idle, a station would defer its transmission within a backoff time to avoid collisions with other stations. The backoff times follow uniform distribution over [0, CW]. In this way, fairness among all the stations can be guaranteed. However, propagation distance was ignored and in safety-related message broadcasting fairness is not the most important issue. In the proposed algorithm, the lengths of backoff times are generated from a nonuniform distribution. They are related with the distances between the source station and its forwarding stations. The farthest forwarding station has the highest probability to forward messages. Performance of the proposed algorithm is analyzed by using a 2D Markov chain. Analytical and simulation results demonstrate that the proposed algorithm can enhance the performance of safety-related message broadcasting in terms of propagation distance, which is reflected by the successful transmission probability. The proposed algorithm does not need additional waiting time, RTS/CTS, and ACK, therefore having better compatibility with the IEEE 802.11p standard than earlier distance-aware algorithms. [ABSTRACT FROM AUTHOR]

This work examines the technique of fractional frequency reuse for the downlink of multi-cellular WiMAX networks. Different frequency-reuse deployment scenarios are presented. Three schemes for the reuse zone selection are evaluated, namely, the distance-based and SINR-based approaches, as well as a new scheme, which is based on load-balancing between different reuse zones. The proposed load-balancing scheme overcomes the main weakness of the SINR-based approach, which is its inability to efficiently manage the available resources of both reuse zones as their size varies. The evaluation of the different schemes is based on simulations that employ a ray-tracing propagation model, thus estimating the propagation phenomena as closely to reality as possible. The simulation results demonstrated clearly better performance of the proposed algorithm compared to the distance-based and SINR-based approaches. It is shown that the use of fractional frequency reuse with the proposed load-balancing approach improves the performance of WiMAX networks in terms of a variety of metrics, such as blocking ratio and offered bit rate. [ABSTRACT FROM AUTHOR]

In this article, we aim to evaluate the influences of different propagation models on the results of V2X simulations. First, we analyze how the models free space propagation, Rayleigh fading, and Ricean fading in synthetic scenarios with and without background communication influence the simulation of communication in general. After that, we investigate the impact of the models on the simulated behavior of a V2X traffic efficiency application in a real inner city scenario. Our results show that the selection of the propagation model affects the number of delivered messages, but exerts no significant influence on the simulated effectiveness of a V2X traffic efficiency application in urban areas. Under those circumstances, a simplified propagation model is sufficient. [ABSTRACT FROM PUBLISHER]

The article relates the author's experience of giving a half-day short course "Electromagnetic Engineering and Teaching via Virtual Computer Tools" at the Institute of Electrical and Electronics Engineers Inc. EUROCON 2007. Struck by a question about numerical propagation from one of the attendees, he realizes that it is important to first briefly discuss modeling and numerical simulation approaches in electrostatics and electrodynamics. He opines that it is essential to agree on some fundamental terms and concepts in computer simulations of differential equations of different types.

Oceanographic and geo-acoustic variability in the shallow water can dominate acoustic propagation. Often the environment is critically undersampled, compared to the sensitivity of the full-field propagation model used [such as the Parabolic Equation (PE) model]. For regions with environmental uncertainty (which is known from measurements or models), there will be a Minimum Achievable Uncertainty (MAU) in acoustic propagation modeling (Transmission Loss). Given this MAU, it is proposed that field interpolation techniques be applied to speed up the acoustic propagation computation, consistent with keeping the interpolation errors below the MAU. Techniques for estimating the uncertainty in TL and speeding up the broadband range-dependent computation using the Navy Standard PE model will be presented. For fully 3-D field computations in a range-dependent environment, the speed up is expected to be several orders of magnitude. [ABSTRACT FROM AUTHOR]