Measurements and modeling of the satellite-to-indoor channel for Galileo

Abstract

In this paper we present results obtained during an ESA project in 2002, carried out by Joanneum Research/Austria, DLR/Germany and the University of Vigo/Spain. Measurements were performed using a high resolution channel sounder on board a helicopter, the objective being the characterization of the satellite-to-indoor channel at frequencies close to those assigned to the future Galileo system. The helicopter flew around a building at different elevations. The receiver was placed in different locations within the building so that different penetration conditions were studied. Typical measured power-delay profiles will be presented and analyzed. To complement the study, a 3D CAD model of the measurement building was created to be used by a deterministic ray-tracing based propagation tool to gain further insight on the propagation phenomena. The external and internal walls as well as windows and doors and features like staircases were considered in the CAD model. Different materials and wall widths were also assumed. The ray-tracing tool included a Uniform Geometrical Theory of Diffraction, UGTD, electromagnetic module. Contributions of second order reflections and diffractions were taken into account, characterized in terms of magnitude, phase, delay and angle of arrival, being later converted to power-delay profiles. It has been confirmed that wall attenuation is the main propagation element, which drastically reduces in-building coverage, except for rooms with external walls. For these external wall rooms and hallways the consideration of diffracted rays is essential to make the predictions match the measurements. A statistical channel model was derived from the measurements and the deterministic ray-tracing analysis. It reflects the different time-spreading conditions found in the measurements, which are mainly caused by reflections and diffractions within the building itself and those produced on external buildings. The statistical model also addresses how the arriving contributions reach the receiver in groups or clusters of rays.