Friedrich M. Landstorfer

Improved PO-MM hybrid formulation for scattering from three-dimensional perfectly conducting bodies of arbitrary shape

The method of moments (MM) represents a suitable procedure for dealing with electromagnetic scattering problems of arbitrary geometrical shape in the lower frequency range. However, with increasing frequency both computation time and memory requirement often exceed available computer capacities. Therefore a current based hybrid method combining the MM with the physical optics (PO) approximation suitable for three-dimensional perfectly conducting bodies is proposed in this paper. The hybrid formulation allows a substantial reduction of computation time and memory requirement, while the results are in reasonable agreement with those based on an application of the MM alone. Further improvement can be achieved for flat polygonal parts of the scattering body by a heuristic modification of the PO current density taking into account the effects of edges. As opposed to the physical theory of diffraction (PTD), no additional electric and magnetic line currents along the edges are necessary. >

Database correlation for positioning of mobile terminals in cellular networks using wave propagation models

Many new services for mobile radio networks rely on a precise location of the mobile terminal. Especially in urban environments, multipath propagation leads to very complex scenarios without line-of-sight between the mobile and the different base stations. In these situations, a location technique based on simple delay evaluations and/or GPS is not accurate enough or not applicable. In this paper, a database correlation method for the positioning of mobile terminals is presented which yields precise results in urban environments. The approach is based on propagation models utilized for the planning of mobile radio networks. The results of the propagation models during the planning process define a look-up-table. By evaluating the measured path losses and available propagation times between the mobile terminal and several base stations, the positions of mobile terminals in urban environments can reliably be predicted.

Improvement of the PO-MoM hybrid method by accounting for effects of perfectly conducting wedges

A correction of the conventional physical optics (PO) current close-to-perfectly conducting wedges based on an application of the uniform geometrical theory of diffraction (UTD) is presented. This improved PO current is used in a hybrid formulation in combination with the method of moments (MoM) to deal with three-dimensional scattering bodies of arbitrary shape. The accuracy of this hybrid method is demonstrated by some examples. As opposed to an application of the physical theory of diffraction (PTD), only surface current densities and no fictitious electric and magnetic line currents along the edges are involved which allows a uniform treatment of the MoM and the PO region by expressing the surface current density as a superposition of basis functions defined over triangular patches. >

Measurement of building penetration loss and propagation models for radio transmission into buildings

The investigation of radio transmission into buildings is getting more and more important. Models for the propagation into buildings enable the calculation of the indoor field strength coverage based on the given outdoor coverage. In order to develop and to calibrate such propagation models several measurements of the building penetration loss with different transmitter locations were undertaken and evaluated. Additionally, the empirical, semi-empirical and deterministic models we developed are presented in this paper.

Dominant paths for the field strength prediction

An algorithm for the determination of the dominant paths for indoor wave propagation is presented. The algorithm computes a tree of the relations between the rooms inside the building and the branches of the tree are used for the determination of the dominant paths. Based on these dominant paths, three different prediction models are presented and compared with one another and with measurements. Two of the three models are based on neural networks, trained with measurements and the third model is an empirical model. With the neural prediction models a good generalization is achieved and they are very accurate in buildings not used for the training of the neural network.

Field strength prediction in indoor environments with neural networks

A new model for the field strength prediction for mobile communication networks inside buildings is presented. The model is based on artificial neural networks, trained with measurements. In contrast to other neural prediction models a good generalization is achieved, so the prediction results are also very accurate in buildings not used for the training of the neural network. Two algorithms for the selection of the training patterns for the neural networks are presented and compared to each other.

Advanced ray‐optical wave propagation modelling for urban and indoor scenarios including wideband properties

Ray-optical propagation models are often utilized for the prediction of the field strength (and delay spread) in mobile radio networks. However, the practical usage of these deterministic models is limited by their high computational demands. A new method for the acceleration of ray-optical models is presented in this paper. It is based on a single preprocessing of the database in which the mutual visibility relations between the walls and the edges of the buildings are determined. The propagation model is implemented for urban and indoor scenarios, and comparisons with measurements show the gain in computation efficiency as well as in achieved prediction accuracy.

Numerical study on an equivalent source model for inhomogeneous magnetic field dosimetry in the low-frequency range

A new equivalent numerical source model is proposed for efficient dosimetric investigations in the low-frequency range. This approach allows the reproduction of complicated inhomogeneous magnetic field distributions around electronic appliances with full generality (i.e., supports three-dimensional vector fields). This paper investigates the accuracy of the equivalent source model using the geometry-based numerical reference model of a current loop to simulate the magnetic field distribution of a real electronic appliance. Good agreement between the equivalent source model and the reference is obtained with regard to the magnetic field distribution and the induced electric current density in a homogeneous human body model, respectively.

Radio network planning with neural networks

The increasing number of participants in modern mobile radio networks, especially with the prospect of the new CDMA systems, necessitates a more and more detailed and efficient radio network planning. The basis of network planning is always the prediction of the quality of transmission between the transmitter and the participant. In order to find the optimal location of the transmitters in a tolerable time, an automatic positioning of base stations in an urban area needs an accurate and fast propagation model. Presently, there is no satisfying combination of an accurate and fast propagation model and an algorithm which perform the positioning of base stations in large urban areas. A fast optimization algorithm for CDMA networks based on a fast and accurate propagation model is presented. For both, the coverage prediction and the optimization process neural networks are used. For the prediction of the coverage, which has to be optimized, a sophisticated backpropagation network is used whereas for the optimization process a self organizing map is applied. First results of the planning and optimization of an urban radio network based on these new algorithms are presented.

Wave Propagation Models for the Planning of Mobile Communication Networks

The paper gives a survey on a variety of methods for modelling wave propagation in different mobile communication scenarios. The requirements for predicting fieldstrength level and other relevant parameters are discussed for various mobile communication networks including outdoor and indoor scenarios. Apart from well known and widely used propagation models new approaches with minimised computation time are presented.