A Novel Channel Model for Land Mobile Satellite Navigation

Abstract

One of the most significant problems to achieve an accurate navigation solution for both GPS and GALILEO within cities is the multipath reception. Various channel models do exist for ground to ground communications (e.g. COST 207 for the GSM system). But there is still a lack of knowledge for broadband satellite to earth channels. Therefore the German Aerospace Centre (DLR) performed a measurement campaign in 2002. In this campaign we used a Zeppelin to simulate a satellite transmitting a 100 MHz broadband signal towards earth. To ensure a realistic scenario the signal was transmitted between 1460 and 1560 MHz just nearby the GPS L1 band. This signal was received by a measurement van and was recorded using a regular time grid. The so gathered data was then passed through a super resolution algorithm to detect the single reflections. In a further step we tracked the detected reflections in time and gained a knowledge about the characteristics of any isolated reflection. This includes Power distribution Delay distribution Duration statistic Doppler drift Doppler spectrum. Direct path blockage From this data we derived a channel model that is synthesising approximately the measured channel impulse response. This channel model will be presented in the talk. It allows the realistic simulation of the multipath channel by approximating every single reflection. This model includes time variant reflectors approaching and receding, appearing and disappearing reflectors and a variation of the azimuth and elevation of the satellite. Due to the measurement approach the channel model is independent on the transmitted signal. Therefore the usability for both navigation systems (GPS as well as GALILEO) is given. For better understanding and visualisation we will present video recordings taken during the measurements combined with the channel impulse response, Doppler delay spectrum and geometrical information.