Quad Constellation Receiver - GPS, GLONASS, Galileo, BeiDou

P.G. Mattos, F. Pisoni

Abstract:	Multiconstellation GNSS first became widely available in 2010/2011, but only as 2 constellations, GPS+Glonass, as although receivers may have supported Galileo, there were no usable satellites. Compass was a name only, as without a spec (ICD), no receivers could be built. However the hardware development time of receivers had been short-circuited…the Galileo ICD had been available for years, Compass codes had been reverse-engineered by Stanford(Gao et al), and at the end of 2011 confirmed by the “test-ICD”, which allowed signal testing without yet releasing message characteristics or content. The last weeks of 2012 gave two great leaps forward for GNSS. Galileo IOV3 and 4 started transmitting at the beginning of December, bringing the constellation to 4 and making positioning possible for about two hours a day. At the end of December the Chinese issued the Beidou/Compass ICD, allowing the final steps of message decode and ephemeris calculation to be added to systems that had been tracking Beidou for many months, and thus supporting positioning. The Teseo-2 receiver has been available for some years, so apart from software development, it was just waiting for Galileo, but for Compass it needed hardware support in the form of an additional RF front end. Additionally, while it could support all four constellations, it could not support Compass and GPS/Galileo at the same time, as without the Compass ICD the spreading codes had to be software generated and used from a memory based codegenerator, thus blocking the GPS/Gal part of the machine. New for 2013 is the Teseo-3 receiver, which returns to the optimum single chip (RF integrated with digital silicon, and flash memory in the same package), and Compass and GPS/Gal can now be used simultaneously. Multiconstellation in 2012 was GPS+Glonass, which brought huge benefits in urban canyons with up to 20 visible satellites in an open sky. Now for two hours a day in Europe, while the Galileo IOV’s are visible, we can run three constellation, and in the China region, GPS/Compass/Galileo is the preferred choice. The paper covers the first tracking of 4 Galileo satellites on December 4th 2012, first positioning with Galileo, first positioning with Compass in January 2013. It will cover static and road tests of each constellation individually and together as a single positioning solution, Road tests in the US/Europe will combine GPS/Glonass/Galileo, while tests in the China region will combine GPS/Galileo/Compass. Results will be discussed from a technical point of view, but also the market future of multi-constellation hardware will be considered. In the 2010-2020 timeframe Glonass and Compass (1602MHz FDMA and 1561MHz respectively) cost extra silicon in both RF and digital hardware, and cause marginal extra jamming vulnerability due to the 50MHz bandwidth of the front end. The extra silicon also causes extra power consumption. After 2020, Glonass is expected to have the L1OC signal operational, CDMA on the GPS/Galileo frequency, and Compass is expected both to have expanded worldwide, and also to have the B3 signal fully operational, again on 1575MHz. At this point we will have 4 global constellations all on the same frequency, giving us over 100 satellites…so with a clear sky the user might expect to see over 30, sometimes 40, simultaneously. Besides the performance benefits in terms of urban canyon availability and accuracy, this allows the receiver to be greatly simplified. While code generators will require great flexibility to generate any of the code families at will, the actual signal path will be greatly simplified…just one path in both RF (analogue) and baseband (digital) processing…including all the notch filters, derotations etc. And this will greatly the power consumption. Will the market want to take the benefit in power consumption and silicon area, or will it prefer to reuse those resources by becoming dual-frequency, adding also the lower-L-band signals, initially L5/E5, but possibly also L2/L3/L6 ? The current view is that the consumer receiver will go no further than L5/E5, but that the hooks will be built-in to allow the same silicon to be used in professional receivers also, or in L2C implementations to take advantage of the earlier availability of a full constellation of GPS-L2C rather than GPS-L5. The paper will present both technical results of field trials of the quad-constellation receiver, which is already running in the lab, and also the forward looking view of how receivers will grow through multi-frequency, and shrink through the growing signal commonalities over this decade.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	176 - 181
Cite this article:	Mattos, P.G., Pisoni, F., "Quad Constellation Receiver - GPS, GLONASS, Galileo, BeiDou," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 176-181.
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