Multilpath and Tracking Performance of Galileo Ranging Signals Transmitted by GIOVE-A

Andrew Simsky, David Mertens, Jean-Marie Sleewaegen, Tom Willems, Martin Hollreiser and Massimo Crisci

Abstract:	Analysis of GIOVE-A signals is an important part of the IOV phase of the Galileo program with a particular goal to test the tracking of all the code modulations, evaluate multipath performance of the Galileo signals, verify the design and operation of both signal transmitters and receivers. In this paper we summarize the results of the performance analysis of the GIOVE-A measurements, collected with the use of Septentrio’s GETR receiver during more than a year since the first reception of GIOVE-A signals in the beginning of 2006. GIOVE-A is transmitting the ranging signals using all the code modulations currently foreseen for the future Galileo. Multipath performance of GIOVE-A signals provides a foretaste of the performance of future Galileo signals in real-life applications. Due to the use of advanced code modulations, the ranging signals of Galileo provide significant improvement of the tracking and multipath performance as compared to current GPS. A year ago we presented at this conference first results of the performance analysis for GIOVE-A signals: signal power, tracking noise and multipath performance. In this paper the results of the next stage of this research are reported. Based on the same methodology of data analysis, we processed a lot more data sets including the data from different antenna sites, different geographic locations and different antenna types. The main conclusions of our first paper are now verified on a much wider array of data. Despite significant site-dependent variability of static data the previously stated classification of the signals in terms or multipath performance is confirmed. According to this classification, all the Galileo signals fall into 3 groups: (i) the group of 3 best signals E5AltBOC, L1A, E6A (ii) intermediate group which includes E5a, E5b, E6BC and (iii) L1BC which shows the lowest values of performance indicators. This classification, which agrees with theoretical predictions and computer simulations, can be accepted as a general rule, although in some tests E6BC and E5a show performance similar to L1BC, and E6A in the others shows performance more typical to the medium group. Peculiarities of real-life multipath, especially site-dependent variations of typical delays of reflected signals, present a great variety of multipath conditions, which lead to significant site-dependent variablity of multipath statistics. One conclusion is very clear: in all the hitherto performed tests E5AltBOC showed by far the best multipath performance, with the magnitude of multipath errors about 4-5 times lower than for GPS-CA. It is quite remarkable that GLONASS-L2P signals have the same code modulations as Galileo E6BC. The multipath analysis of GLONASS-L2P sheds additional light on the future performance of the Commercial Service of Galileo which is based on E6BC. It is demonstrated that both GLONASS-L2P and E6BC have similar performance gain with respect to GPS-CA. Due to significant attention to the car navigation as a potential application field for new Galileo signals, a few car tests have been done. It is shown that in the car tests the differences between the multipath errors for different modulations are much smaller than for the static tests. These results are discussed in the context of the ongoing debate about the possible replacement of BOC(1,1) with MBOC. It is expected by many that MBOC shall perform better in automotive applications, this being one of the most popular arguments in support of MBOC. In fact, the analysis of GIOVE-A data shows that in car tests all the different signals, both of Galileo and GPS show comparable multipath performance, generally much better than in the static environment. Therefore in our opinion, replacement of BOC(1,1) with MBOC cannot become a real differentiator for car navigation applications.
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:	1596 - 1609
Cite this article:	Simsky, Andrew, Mertens, David, Sleewaegen, Jean-Marie, Willems, Tom, Hollreiser, Martin, Crisci, Massimo, "Multilpath and Tracking Performance of Galileo Ranging Signals Transmitted by GIOVE-A," 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. 1596-1609.
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