Evaluating the Performance of GALILEO using the NavSim tool

Stefan Schluter, Evelin Engler, Alexander Steingass, Rainer Kramer and Thoralf Noack

Abstract:	Based on the known specifications of the European satellite navigation system GALILEO, the software simulation tool NavSim is used to estimate the achievable positioning performance under consideration of several natural, geometric and technical scenarios. To allow for a correct interpretation of the derived results, a short overview about the architecture of the simulation tool NavSim, the implemented models and therefore of their capability and limitations will be given. The NavSim simulator is realised as a two layer concept. The system layer covers satellite movements, user movements, tropospheric and ionospheric effects and the solution of the navigation equation. The signal layer covers all signal aspects of the system like pulse shapes, spreading codes, chip rates, non linearities or multipath distortions. For the proposed GALILEO satellite constellation and the allocated frequency bands in a first step the propagation conditions are analysed with regard to their effects on the signal states described by the carrier power to noise power density ratio (C/N0), the code and phase delays and the corresponding rates. This will be performed under consideration of temporal and regional differences and the signal magnitude and probability distribution. To contribute to current technology discussions we will include the topics: • Pulse shaping of the signal The ranging accuracy of the receiver is influenced directly by the selected pulse shape. A comparison of the two possible pulse shapes root raised cosine and rectangular will be given. • Non linear satellite amplifiers The impact of non linear high power amplifier on the gathered ranging performance will be discussed. The amount of the decrease shows that it‘s possible to handle this effect within the link budget. • Multipath errors Multipath reflections are biasing the pseudorange determination of GALILEO. The influence of different channels to the navigation accuracy has been determined and will be presented in dependency of the C/N0. • Atmospheric propagation effects The influence of propagation errors on the signal states and on the gathered positioning accuracy and availability will be analysed considering especially non regulary effects like scintillations. • Clock errors The system time error will be discussed under consideration of used clock types and in dependence of the system time generation parameters. • Positioning performance The navigation accuracy will be described for several scenarios using standard algorithm for data preprocessing and positioning. The examples are used to derive an impression of GALILEO performance. These simulations lay a foundation for a definition of GALILEO’s performance which can be used not only in the definition phase but as well on designing the system itself.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	1317 - 1324
Cite this article:	Schluter, Stefan, Engler, Evelin, Steingass, Alexander, Kramer, Rainer, Noack, Thoralf, "Evaluating the Performance of GALILEO using the NavSim tool," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 1317-1324.
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