Multipath and Tracking Performance of Galileo Ranging Signals Transmitted by GIOVE-B

Andrew Simsky, David Mertens, Jean-Marie Sleewaegen, Wim De Wilde, Martin Hollreiser, Massimo Crisci

Abstract:	One of the purposes of the GIOVE-B mission is to verify the improvement in multipath performance achieved by replacing the Galileo L1BC-BOC(1,1) modulation with MBOC, a combination of BOC(1,1) and BOC(6,1). This paper contains first experimental results for the multipath performance of both BOC(1,1) and MBOC modulations based on the analysis of live GIOVE-B measurements. A comparison of the two signals has shown that MBOC outperforms BOC(1,1) by 20-25%. This difference is mainly due to a reduction in the high-frequency part of the error which consists of tracking noise and long-range multipath. The optimization of antenna design for multipath performance can also significantly reduce multipath errors. In this paper we compare the performances of the wideband Space Engineering antenna (so far the main antenna in the GIOVE signal experimentation program) to that of the new prototype reference station antenna which is similar in design to well-known GPS choke-ring antennas. As expected, the choke-ring design brings about significantly better multipath performance, especially in the L1 band. Although the custom-made GETR receiver remains the main tool for GIOVE data analysis, two other GPS/Galileo receivers have recently become available: a single-frequency AsteRx1 and dual-frequency PolaRx3G (L1BC/E5a). Both AsteRx1 and PolaRx3G are able to track GIOVE signals. In this paper we compare the measurements taken with PolaRx3G to those taken with the GETR and demonstrate that the differential betweenreceiver biases are of the mm-level. The group delay between the L1 and E5 ranges is estimated with the help of an iono-free formula which uses the data at three frequencies. Signal power of GIOVE-A and GIOVE-B was compared. GIOVE-B transmits more power by 3dB in L1 band and by 5 dB in E5 band. With multiple frequencies simultaneously present on two satellites, computation of double-differenced measurements and estimation of integer phase ambiguities may be attempted. In this paper we present the first hands-on experience of the triple-frequency geometryfree ambiguity resolution using simultaneous data of GIOVE-A and GIOVE-B. We also obtain experimental estimates of noise values limiting the efficiency of the geometry-free approach.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	1525 - 1536
Cite this article:	Simsky, Andrew, Mertens, David, Sleewaegen, Jean-Marie, De Wilde, Wim, Hollreiser, Martin, Crisci, Massimo, "Multipath and Tracking Performance of Galileo Ranging Signals Transmitted by GIOVE-B," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 1525-1536.
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