M. Dottling

Two- and three-dimensional ray tracing applied to the land mobile satellite (LMS) propagation channel

This work examines the application of ray-tracing propagation models to system simulations for satellite mobile communications. A two-dimensional (2D) and a three-dimensional (3D) algorithm are outlined and compared using canonical propagation problems. Additional comparisons of both models with measurement campaigns are performed. The results show that two-dimensional models are suited for coverage and network planning. For system-design studies, however, three-dimensional ray tracing is mandatory. The novel three-dimensional ray-tracing model is able to predict time series of power delay profiles, Doppler and polarimetric information with high precision. It includes the time-variant correlation between the propagation channels of all visible satellites of an arbitrary satellite constellation. It therefore proves to be especially suited for system investigation of future LMS communication and navigation systems.

Ray optical prediction of outdoor and indoor coverage in urban macro- and micro-cells

A new approach for the prediction of path loss and channel impulse response of radio links with building penetration is presented. The wave propagation prediction is based on ray-tracing algorithms implemented in the IHE-URBAN-MICRO model, which has already been successfully applied to urban micro- and macro-cells. A brief description of this model is given and comparisons with path loss measurements are shown. The extension of the IHE-URBAN-MICRO model for indoor receiver locations, resulting in the new model IHE-URBAN-MICRO-I, is presented. Both models use vector oriented building data and raster based topography data. Arbitrary outdoor base station heights can be handled by the models, which is a very important feature from a practical point of view.

A novel ray-optical approach to model wave propagation in curved tunnels

In this paper, a novel ray optical approach is presented to model the electromagnetic wave propagation in curved tunnels with rectangular or arched cross-sections. The modelling is performed by a stochastic ray launching technique (Monte-Carlo method), based on geometrical optics. Due to the curved surfaces, a so-called ray density normalisation is introduced in order to predict the field strength precisely. The model is verified theoretically with a corrugated circular waveguide and by various measurements at 120 GHz in scaled tunnel models.

A versatile propagation channel simulator for land mobile satellite applications

This paper introduces a new channel simulator for land mobile satellite (LMS) systems. The mobiles surroundings are characterized by topographical and land use data, as well as by a statistical description of single roadside objects. The propagation model combines the advantages of deterministic ray tracing algorithms with stochastic models for shadowing and short term fading effects. Thus, in contrast to entirely statistical and empirical approaches, the simulation tool is valid for a wide frequency range and a great variety of operational scenarios. Comparison of calculated results with published LMS measurements show good agreement.

A comparison and verification of 2D and 3D ray tracing propagation. Models for land mobile satellite communications

Propagation modeling for land mobile satellite (LMS) systems is mainly used for system design. Questions of interest include the design of error protection, equalization, synchronization, Doppler compensation, as well as the performance evaluation of power control, satellite or polarization diversity, and handover. Therefore typical wideband time series are required, that include shadowing, short term fading, echo delay, Doppler, and polarization effects. Ray optical propagation models offer an excellent means to perform such in-depth propagation studies. In the following a two-dimensional (2D) and a three-dimensional (3D) ray tracing model for non-urban areas are briefly outlined. The performance of the two models is evaluated using LMS measurements. It is shown that 3D propagation modeling considerably increases prediction accuracy of first and second order channel statistics.

Modeling of the DECT outdoor radio channel

While originally planned for indoor use, more and more outdoor applications of DECT (Digital Enhanced Cordless Telecommunication) systems are emerging. In this paper a new wave propagation model based on imaging theory is introduced, which is especially adapted for low base station antenna heights. Comparisons with measurements and other ray tracing methods are used to evaluate the prediction accuracy and computational complexity. The advantages of ray optical models for the planning of outdoor DECT systems are demonstrated by path loss and delay spread predictions. Angle of transmission and angle of arrival diagrams are evaluated to optimize the coverage area using directive antennas.

Wideband channel modeling and diversity techniques for satellite-UMTS

Next-generation satellite systems aim at providing both high-data-rate services and mobility to the users. Therefore wideband propagation channel modeling becomes crucial for system planning. This paper introduces a novel approach of generating and processing realistic wideband time series of land mobile satellite (LMS) propagation channels. It uses the results of a ray-tracing propagation model to evaluate the performance of satellite and polarization diversity including the effects of imperfect power control and signaling delay, as well as intersymbol and multiple access interference. Exemplary results are shown for the wideband code division multiple access (W-CDMA) radio interface of future S-UMTS (Satellite-Universal Mobile Telecommunications Systems)/IMT-2000 (International Mobile Telecommunications).

Fast determination of channel impulse responses by 3D wave propagation modeling

A new deterministic 3D wave propagation model is presented, which is as accurate as the original IHE-3D-RURAL wave propagation model [Lebherz et al., 1992, Kurner et al., 1994] but less time consuming. Therefore, the ray tracing is improved by using new and faster algorithms. As a consequence, now an area covering bit-error-rate prediction for digital communication systems such as GSM or digital audio broadcasting is possible.

Spatial radio channel modeling for the design of new generation mobile communication systems

The market for broadband wireless communication systems has been growing enormously in the last years. Designing digital communication systems requires dedicated simulation approaches with an emphasis on the multipath propagation channel including directions of transmission and arrival. In this paper a stochastic channel model for the indoor propagation channel including path directions is presented. For the correct consideration of correlation in time and space the model is based on a stochastic process. Propagation paths appear, remain for a certain time-span, and finally disappear. The probability density functions and their parameters used to generate the properties of the propagation paths are determined from deterministic ray-tracing results. Additionally some first simulation results to demonstrate the function of the model and the potential of directive antenna systems in indoor environments are presented.

Deterministic modeling of the street canyon effect in urban micro and pico cells

In this paper the modeling of the street canyon effect in urban wave propagation is investigated. Multiple diffracted signal paths can be calculated using a simple ray tracer. However, significant power is also transmitted by a combination of wall reflection and wedge diffraction. This paper introduces a new deterministic algorithm which is able to calculate such paths using imaging techniques. Emphasis is put on the efforts made to reduce the problems complexity since a straight forward application would suffer from enormous computing time and memory requirements. Comparisons with DCS1800 measurements show notable improvements of the field strength prediction.