A new approach for predicting the future channel situation on the basis of actual and past channel characteristics is suggested. Applying high resolution estimation techniques to the time-variant transfer function of the radio channel, a 2-D fading forecast based on parametric modeling is introduced. In contrast to existing methods this allows a small-scale fading forecast not only in the time domain, but also in the frequency domain. Moreover, considering the evolutional nature of the channel and its parameters, an increased prediction range is expected, as compared with previously proposed approaches. Explaining the extended approach and corresponding modeling of the parameter variations, an appropriate prediction scheme is introduced considering a mobile moving with constant speed on a straight line. Applied on simulation data of a ray-tracing modeled indoor scenario of moderate complexity, the performance as well as the boundary conditions of the proposed procedure are illustrated.

After a review of the known description of time-variant channels by means of system and correlation functions, a consistent extension of this description to directional time-variant channels is described. This extension allows a clear distinction between time- and space-variant effects in directional mobile radio channels. The major intention of the described directional extension however is the derivation of a statistical modeling approach for small-scale fading effects in time-variant wideband directional channels, which can be regarded as a consistent extension of the well established Rayleigh or Rice-fading approach for nondirectional time-variant narrowband channels. The approach, which is based on the time and aperture-variant transfer function, appears to be preferable to the frequently used statistical modeling of the time-variant angle-resolved impulse response for several reasons. The major advantage is that the approach can cope with the demand for a great number of superimposing components as the basis for statistical modeling. The correlation between adjacent values is proposed to be achieved by filtering with appropriate directional scattering functions. The description of the modeling approach, as done in the present paper, is intended to be general and universal; for the application on certain channel types statistical distribution functions and parameters to be used with the approach can readily be determined from appropriate measurements.

With a view to planning for wireless local area networks (WLAN) in the 5.2 GHz frequency band, a ray-tracing-based wideband indoor wave propagation model is applied to a real indoor environment and the major wave propagation effects found in the corresponding measurements are analyzed with its help. In evaluating the space-variant impulse responses of the measurement and simulation, the main propagation paths are properly reconstructed by the model for a classroom environment. Still, there is a lack of knowledge concerning the material parameters of the obstacles involved. However, it is shown that using a ray-tracing algorithm, the essential channel properties can be extracted from measurements by comparing the scattering functions of the channel for both measurement and simulation. Significant scatterers are identified and qualitative information is extracted, showing which material parameters have been chosen "well" or "badly" by comparing single contributions from the simulation results to the corresponding measurements. An optimization and automation should be possible and is topic of current research.

For investigations on channel characteristics in a deterministic indoor environment, a ray-tracing-based wideband wave propagation model with moving receiver is proposed. Considering multiple reflections and transmissions to be basic propagation effects inside buildings, the space-variant complex channel impulse response and the scattering function are calculated and compared to wideband measurements at 1800 MHz carried out in a shelter. Good agreement was found for delay times, detection of propagation paths and general characteristics of the impulse responses both for the LOS and NLOS cases. Yet, especially the magnitudes in the NLOS case suffer, for example, from uncertainties caused by an arbitrary choice of material parameters. Further investigations have to show, whether it is possible to apply the model to less deterministic environments.

To investigate the performance of a planned short range traffic management system with data rates more than 1 Mbit/s in case of multipath effects, an experimental system has been built. Bit error properties are investigated by recording transmitted pn-sequences in real time and off-line analysis using correlation techniques. Measurement results regarding the dependence of bit errors and clock errors on the covered distance are presented for the downlink. The results show that a sufficient range of about 25 m is achievable for synchronous data transfer.>