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Propagation path losses affecting intervehicle communication (IVC) at 60 GHz are presented. In order to examine the radio-propagation characteristics in the IVC system, in the first stage of our investigation, we have carried out propagation tests between two vehicles communicating in a line-of-sight (LOS) situation at fixed positions on a smooth surface paved with asphalt, which is the normal communication condition. Furthermore, the non-LOS (NLOS) situation with up to three intermediate vehicles, which can cause an obstruction, has been conducted. To construct path-loss models in NLOS cases, the uniform theory of diffraction technique was applied to the calculation of waves propagating through the intermediate vehicles. The propagation path models were derived from the measured results. In the second stage, a path-loss prediction formula was derived by statistically processing the data that had been calculated using the propagation path model. The propagation tests between the vehicles in motion confirm that the path-loss prediction formula is very useful when the communicating vehicles are moving, and it is therefore suitable for designing the cells that form the IVC. [ABSTRACT FROM AUTHOR]

This paper covers some of the work carried out in the planning of the Global System for Mobile Communication for Railway (GSM-R) of the tunnels on the new high-speed trains in Spain. Solutions based on distributed antenna systems have been tested by installing several 900-MHz transmitters inside and outside of a 4000-m tunnel and measuring the propagation indifferent conditions. The measurements have been used to model the effects of tunnel propagation, including curves, trains passing from the outside to the inside, and the effect of two trains passing inside the tunnel. All cases have been tested by comparing solutions using isofrequency and multifrequency distributed transmitters inside the tunnel. The improvements of signal-to-noise ratio and the reduction of the blocking effects of two trains passing have demonstrated the advantages of using isofrequency distributed antenna systems in tunnels. Finally, a complete propagation model combining both modal analysis and ray tracing has been applied to predict the propagation loss inside and outside these tunnels, and results have been compared with the measurements. The model has proven to be very useful for radio planning in new railway networks. [ABSTRACT FROM AUTHOR]

This paper presents a method which optimises the computation time of the predictions of radio coverage for microcellular systems, no matter what propagation model is used. The principle consists in reducing the number of application points of the propagation model in relation to the classic technique. The proposed method is based on a multiresolution analysis of measured signals carried out around 2 GHz, and on an electromagnetic analysis of the propagation environment. The performance of the method is evaluated in terms of the reduction in computation time and the effect on accuracy, as compared to the classic technique. [ABSTRACT FROM AUTHOR]

As a remedy to multipath fading in land mobile communication, adaptive antenna arrays combined with equalizers have been proposed. For hardware realization and adaptive algorithm development in order to alleviate fading by temporal and spatial processing, it is necessary to clarify the spatiotemporal characteristics of the propagation channel such as the delay time and direction of arrival of multipath waves. In a microcell using a low antenna-height base station, the spatiotemporal propagation characteristics are measured for line-of-sight and non-line-of-sight propagation at 3.35 GHz. Characteristics of these channels have been presented. With regard to non-line-of-sight propagation, the measured spatiotemporal characteristics are modeled and the angular spread and the delay spread of the arriving waves are quantitatively evaluated. Also, when the transmission characteristics of fading prevention techniques by spatiotemporal processing are evaluated by computer simulation, an example of the delay-azimuth profiles that is usable as a reference for setting the conditions for fading is presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(7): 11–21, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10032 [ABSTRACT FROM AUTHOR]

A typical back-propagation neural network (BPN) model is developed for modelling radio propagation for field strength prediction based on data measurements of propagation loss (in decibels) with terrain information taken in an urban area (Athens region) in the 900 MHz band. The feasibility of the BPN model is checked against the performance of a conventional semiempirical reference model. The performance of both models is quantified by statistical methods. The evaluation is done by comparing their prediction error statistics of average absolute, standard deviation and root mean square and by comparing their percentage accuracy and correlation of predicted values relative to true data measurements. © 1998 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The problem of electromagnetic wave propagation in a two-dimensional tunnel with an arbitrary bending angle is numerically analyzed by the FVTD method. The FVTD representations for the electromagnetic field in a lossy medium and the PML absorbing boundary condition are formulated and a procedure for the numerical analysis of the two-dimensional tunnel is provided. Next, as specific numerical examples, the electromagnetic propagation characteristics near the bend of tunnels with bending angles of 30°, 45°, and 60° are computed. It is confirmed that the results agree well with those of the model experiment using microwaves. Detailed numerical calculations are performed for the case in which the width of the tunnel is much larger than the wavelength. In this way, the propagation characteristics are predicted for an electromagnetic wave in the mobile communication frequency band, used inside a tunnel. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(9): 1–9, 1999 [ABSTRACT FROM AUTHOR]

To understand the propagation structure of the microcells with a tall and medium-height antenna in an urban area, the fundamental propagation parameters are found and the structural model of the propagation loss was constructed. The fundamental propagation parameters were obtained based on the multivariable analysis of the propagation data at 800 MHz measured m the Tokyo Metropolitan area. These parameters are the distance between the transmitter and receiver, the average building height between the transmitter and receiver, and the base-station height which have high correlation and regression coefficients with the propagation loss. The relationship of parameters obtained from the model is (20 - α) log(h) for the base-station height characteristics and (α - 20) log (H) for the building height characteristics if the distance characteristics are α log (d). The relationships of coefficients of the conventional estimation equation and the regression equation obtained by the measured data almost agreed with those of the model so that the validity of the model was confirmed. [ABSTRACT FROM AUTHOR]

Propagation characteristics while entering tunnels are analyzed by using a ray-launching technique and the uniform theory of diffraction (UTD). RMS angular spread is studied and related to the “excitation zone.” This paper presents interesting differences in the behavior of this parameter and the RMS delay spread. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 196–198, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10866 [ABSTRACT FROM AUTHOR]

This letter presents a characterization of the vertical plane propagation in terms of the satellite elevation angle for different mechanisms of propagation. The effect of blockage by buildings on the received signal level versus the satellite elevation angle at L-band for urban environments is performed using the uniform theory of diffraction (UTD). © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 336–338, 2000. [ABSTRACT FROM AUTHOR]