Pavel Valtr

Estimation of the Refractivity Structure of the Lower Troposphere From Measurements on a Terrestrial Multiple-Receiver Radio Link

A matched field technique is used for remote sensing of refractivity profile. The method relies on electromagnetic propagation simulation to estimate the height profile of radio refractivity in the lower atmosphere by comparing theoretical predictions with measurements on a terrestrial radio link. The objective is to discover whether small variations of the airs refractive index can be detected in the lowest part of atmosphere, up to 150 m above the ground. The resultant estimations of the height profile of refractivity are compared with the measured refractivity profile obtained from meteorological sensors at different heights. The results show a close agreement between the estimated and measured refractivity profiles during periods of deep fading events.

A wideband, directional model for the satellite‐to‐indoor propagation channel at S‐band

This paper presents a hybrid empirical-statistical model for the satellite-to-indoor propagation channel at S-band derived from measurements using a helicopter to simulate the satellite. The measurements have been carried out by means of a wideband, circularly polarized channel sounder in a SIMO (Single Input Multiple Output) configuration, allowing the derivation of entry loss, wideband and spatial model parameters. It is hoped that this paper will provide relevant information on the satellite-to-indoor channel given the large amount of experimental data available, covering a significant member of different buildings of various types, and the amount of measurement configurations: elevations and azimuths. Copyright

Propagation measurements and comparison with EM techniques for in-cabin wireless networks

This paper presents results of a narrowband measurement campaign conducted inside a Boeing 737–400 aircraft, the objective being the development of a propagation prediction model which can be used in the deployment of in-cabin wireless networks. The measurements were conducted at three different frequency bands: 1.8, 2.1, and 2.45 GHz, representative of several wireless services. Both a simple, empirical, inverse distance power law and a deterministic, site-specific model were investigated. Parameters for the empirical model were extracted from the measurements at different locations inside the cabin: aisle and seats. Additionally, a statistical characterization of the multipath scenario created by the transmitted signal and the various cabin elements is presented. The deterministic model, based on Physical Optics (PO) techniques, provides a reasonable match with the empirical results. Finally, measurements and modeling results are provided for the penetration loss into the cabin (or out of the cabin), representative of interference scenarios.

Domain Decomposition Algorithm for Complex Boundary Modeling using the Fourier Split-Step Parabolic Equation

This paper addresses the use of parabolic equation in radiowave propagation problems involving impedance-boundary modeling. The Fourier split-step technique for solving the parabolic equation provides numerical efficiency but lacks the ability to represent complex boundary conditions. A method that makes use of the domain decomposition technique to solve two-dimensional problems of impedance-boundary modeling using the Fourier split-step technique is introduced. A test case, using an urban scenario represented by buildings with various electrical parameters, was used to validate the results given by the method with results obtained by geometrical optics

The Influence of Horizontally Variable Refractive Index Height Profile on Radio Horizon Range

This letter addresses refraction effects, assuming a horizontally nonhomogeneous troposphere. The influence of a range-dependent refractivity profile on a terrestrial radio link is investigated in terms of radio horizon range. The results can be used for interference analysis in metropolitan wireless networks. An analytical ray-tracing approach was employed to derive formulas for the radio horizon range calculation, considering a horizontally variable refractivity height profile.

World Maps of Atmospheric Refractivity Statistics

Atmospheric refractivity and its vertical gradient affect electromagnetic wave propagation in the atmosphere. Consequently, their statistics are needed for propagation predictions. New world maps of refractivity and its vertical gradient statistics are derived from a global, long-term dataset of meteorological quantities as given by ERA-Interim reanalysis. The derived maps provide long-term statistics obtained from 33 years of meteorological data with a one-degree spatial resolution on a latitude/longitude mesh. A processing method is described and examples of the derived maps are shown. The consistency of the new maps is checked by comparing world maps provided by ITU-R. Accuracy is tested by comparing refractivity statistics obtained from high-quality local measurements using radiosonde and tower measurements. New global maps demonstrate enhanced statistical stability, spatial resolution, and accuracy.

Atmospheric refractivity profiles and microwave propagation on a terrestrial path - Experiment and simulation

The results of experimental measurement of atmospheric refractivity profiles and microwave propagation characteristics at 11 GHz carried out recently at the Podebrady site in the Czech Republic are presented. Long term statistics of atmospheric refractivity were obtained from the tower measurement of temperature, pressure and relative humidity of air. Microwave propagation during clear air conditions was observed concurrently on the 50 km long terrestrial path Prague-Podebrady with several receivers located in different heights above the ground. Propagation of electromagnetic waves was modeled using the parabolic equation method and compared with measured data.

Building entry loss and delay spread measurements on a simulated HAP-to-indoor link at S-band

Results from a measurement campaign emulating the high altitude platform (HAP)-to-indoor communication channel at S-band are presented in this paper. A link was established between a transmitter carried by a helicopter, representing the HAP, and a receiver placed at several locations in different building types including an airport, an office building, a shopping mall, a residential house, and a skyscraper. A wideband, directive channel sounder was used to measure building entry loss and time delay spread. Results of the building entry loss are presented as a function of building type, elevation, and building entry angle. Results of delay spread for each building are also provided.

Short-Term Terrain Diffraction Measurements From L- to Q-Band: Results and Analysis

In response to the current need for a reliable interference and frequency coordination analysis, especially within the ground segment of satellite systems, atmospheric refraction and terrain diffraction phenomena play a key role from a radiowave propagation point of view. While it is convenient to use an ITU-R model for the case of the atmospheric refraction, several different types of models for terrain diffraction are identified in the literature. On the other hand, only a limited amount of experimental data is globally available to address their performance. This is why we carried out own short-term terrain diffraction measurements at the frequencies from L- to Q-band. During the trials, truck-mounted access platforms reaching up to 46 m above ground level were used and terrain profiles with path lengths from 7 km up to 50 km for various combinations of transmitter and receiver heights were addressed. Based on the obtained experimental dataset, the performance of the delta-Bullington and Deygout models, currently recommended by the ITU-R for the purposes of interference analysis, and the terrain diffraction models based on the UTD and parabolic equation approach has been addressed in terms of the testing variable defined in this paper.

In-cabin propagation measurements and comparison with EM techniques

This paper presents a measurement campaign conducted inside a Boeing 737-400 aircraft for the development of in-cabin wireless networks. The measurements were conducted in three different frequency bands in order to provide various services. It was found that the path loss factor along the aircraft corridor varies between 2.1 and 2.3 depending on frequency. In respect the path loss factor ranges between 2.0 and 3.9 at the passenger seats. Propagation prediction technique based on Physical Optics was applied to the cabin scenario to obtain comparison of theoretically predicted values and measurements.