Interference Computations Between GPS and GALILEO

Stefan Wallner, Guenter W. Hein, Thomas Pany, Jose-Angel Avila-Rodriguez and Andrea Posfay

Abstract:	After giving an overview of the baseline in all the bands, the most outstanding characteristics and figures of Galileo will be outlined and compared with GPS. The main objective of this paper is to show the common interference that GPS and the Galileo signals are expected to have in the future. Of special interest is the intersystem interference that GPS will suffer due to the Galileo signals and vice versa. The intersystem interference will be computed according to the methodology for GPS/Galileo radio frequency compatibility which was commonly agreed on by the United States and the European Union in June 2004. A great effort has been put in the computation of the ground received power for every point in time as well as for every point on the earth grid. In addition to the smoothed spectra approach that is used in this agreement more accurate simulations will be performed in this work accounting for the influence of the codes onto the spectra. Thus, in order to have a more realistic insight into the problematic, the real impact of the codes will be considered. This will permit to show how much the expected values of degradation change with respect to the assumption of ideal codes. Further simulations have been carried out to account also for the effects induced to intersystem interference that are caused by augmentation systems, i.e. SBAS. Intersystem interferences will be computed for signals where Galileo and GPS are sharing the band. As we will see, in comparison to the baseline signal BOC(1,1), the candidate optimized GALILEO L1 OS signal [7] is shown to have lower levels of interference with GPS C/A. For the computation of the interference a simulation tool in C++ was programmed. A verification of the simulation results is given by the outputs of the institute’s software receiver [8]. The results of both simulation approaches show good compliance with each other.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	861 - 876
Cite this article:	Wallner, Stefan, Hein, Guenter W., Pany, Thomas, Avila-Rodriguez, Jose-Angel, Posfay, Andrea, "Interference Computations Between GPS and GALILEO," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 861-876.
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