Performance Evaluation of a Multi-frequency GPS/Galileo/SBAS Software Receiver

Marco Anghileri, Thomas Pany, Daniel Sanroma Guixens, Jong-Hoon Won, Ayse Sicramaz Ayaz, Carsten Stober, Isabelle Kramer, Dominik Dotterbock, Gunter W. Hein and Bernd Eissfeller

Abstract:	The real-time capable software GPS/Galileo receiver [1], developed at the Institute of Geodesy and Navigation at the University FAF Munich, has been completely redesigned. Within this paper we would like to discuss the most innovative features, analyze its performance and present an overview of its possible applications. The receiver is intended to work on a conventional PC, processing IF samples coming from a USB Front-end or from previously stored data files. The provided GUI shows detailed internal data as well as comprehensive information about the tracked satellites. A very important feature is that numerous receiver parameters can be set during the runtime. Several tests have been performed connecting high bandwidth L1 and triple frequency (L1/L2/L5) Frontends, specially developed to guarantee the very big transfer rate required for real time processing of such a large amount of data. Acquisition is based on a FFT-IFFT scheme, optionally enhanced with an indoor specific algorithm that performs parallel interference cancellation. For signal tracking, the receiver can run two different filter modes: the first is a order-configurable PLL/FLL/DLL, while a second one is represented by a third order PLL and aided FLL and DLL. The sensitivity that can be reached is about 10 dB-Hz. Advanced code multipath mitigation techniques have been implemented by the optimization of the correlators reference functions. Big effort has been put on the development of various core elements that enable the receiver to acquire and track even highly attenuated signals, as they may occur in an indoor environment. Concerning acquisition, the Doppler search space has been reduced to allow longer integration times and a vector re-acquisition technique is used for tracking signals that show high variable power characteristics. The tracking loop design itself and the bit/symbol synchronization module have been also optimized in this sense. Code phase ambiguity can be resolved by exploiting the so-called single-shotpositioning, in case a very inaccurate PVT solution is available. At the present the receiver can track all-in-view civil GPS and EGNOS signals, as well as the Galileo In-Orbit Validation Element GIOVE-A. A navigation message decoder for the CNAV message that will be sent with the GPS L2C/L5 signals has already been integrated, together with the one for the Galileo I/NAV message. The navigation solution can be obtained by Single Point Positioning or by a Kalman Filter estimate. Current performance shows accuracy levels which are better than 30 cm for code measurements and 1 mm for carrier phase measurements respectively. Beside the ordinary navigation features, a series of support services has been added to increase the performance, offer new capabilities and extend the receiver application field. The possible applications of the receiver are as a GNSS reference/monitoring station and as a powerful development platform for new algorithm prototyping. A version of the software receiver is currently working twenty-four-seven as GPS/Galileo/SBAS reference station, providing measurements obtained from GPS C/A and L2C, EGNOS and GIOVE-A E1-E5a broadcast signals. A first evaluation of the reference station performance is shown in Figure 1.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	2749 - 2761
Cite this article:	Anghileri, Marco, Pany, Thomas, Guixens, Daniel Sanroma, Won, Jong-Hoon, Ayaz, Ayse Sicramaz, Stober, Carsten, Kramer, Isabelle, Dotterbock, Dominik, Hein, Gunter W., Eissfeller, Bernd, "Performance Evaluation of a Multi-frequency GPS/Galileo/SBAS Software Receiver," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 2749-2761.
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