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International Civil Aviation Organization Spectrum Seminar Nairobi, Kenya February 17-19, 2004 Global Navigation Satellite System (GNSS) Overview and Spectrum.

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Presentation on theme: "International Civil Aviation Organization Spectrum Seminar Nairobi, Kenya February 17-19, 2004 Global Navigation Satellite System (GNSS) Overview and Spectrum."— Presentation transcript:

1 International Civil Aviation Organization Spectrum Seminar Nairobi, Kenya February 17-19, 2004 Global Navigation Satellite System (GNSS) Overview and Spectrum Implementation

2 Basic GNSS System Space Segment –Orbiting Satellites GPS GLONASS Future … Galileo? –Geostationary Satellites SBAS Ground Segment –Satellite Control Stations –Augmentation Systems GBAS Future … GRAS?

3 a b c Satellite Navigation … Basically Multilateration Multilateration: By knowing your distance from at least 3 points of known-position, you can determine your own position. For Satellite Navigation: a, b & c are satellites, and a fourth is needed to solve for clock variations.

4 Earths Ionosphere Actual Path Assumed Path Approach: t arrival – t transmitted ~ distance from satellite Assumes straight path of radio frequency signals Earths ionosphere actually disrupts/bends that path Augmentations correct for that bend using dual-frequency measurements Currently not possible in aircraft; L2 signals not protected. GNSS Ranging and Timing

5 Satellite Navigations Mission SBAS/GBAS Implementation GBAS SBAS

6 FAA Satellite Based Augmentation System (WAAS used as example) L1, L2

7 Ground Based Augmentation System (GBAS) Architecture GBAS Reference Station (Integrity Accuracy Availability) Processor GNSS Receiver VHF Transmitter Monitor Status Pseudolite

8 Planned GNSS Modernization Addition of satellite constellations –Galileo, additional GLONASS satellites –Improves user availability Addition of civil signals – MHz band –Facilitates user ionospheric corrections –Possible broadcast of integrity signal May limit need for external augmentations Increased power, improved coding –Better resistance to interference

9 GNSS Frequency Bands Frequency (MHz)Function GBAS broadcast link GPS L5, Galileo E5, future SBAS, GLONASS L GPS L2 (site-by-site ground use only) SBAS, GPS L1, GLONASS, Galileo E1

10 Spectrum Issues GNSS signals are very weak –~ 50,000 times weaker than the minimum specified edge-of-coverage DME signal Aviation spectrum managers must be constantly watching to ensure spectrum incursion from in- band/adjacent band systems does not cause interference. One example: ITU Footnotes and –Allow fixed service in GNSS bands in some countries –Countries encouraged to remove their names from the footnotes.


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