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GNSS and UWB

Explore the fascinating world of Global Navigation Satellite Systems (GNSS) and Ultra-Wideband (UWB) technologies. This comprehensive guide covers the fundamentals of GPS, GLONASS, and Galileo, including how they work, potential errors, and augmentations like DGPS and WAAS. Furthermore, delve into UWB's innovative communications, precision ranging, and its ability to distinguish signals within mere feet. Learn about key concepts such as geometric dilution of precision (GDOP), carrier phase tracking, and more, to better understand how these technologies enhance navigation and positioning accuracy.

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GNSS and UWB

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  1. GNSS and UWB Joe Newman Interactive Media Systems Group

  2. Contents • GPS • How it works • Errors • Augmentations • GLONASS • Galileo • UWB

  3. GPS • Constellation of 24 satellites • 6 orbital planes at 54.8o • Atomic clock • Broadcast on two L-band frequencies • Pseudo-random code • Military encrypted code

  4. Ranging • Received signal level less than background • Errors • Clock errors • Atmospheric delay • Pseudorange is range including error • Navigation message • Carrier phase tracking

  5. Triangulation 1 range puts user on the spherical face of the cone. Intersecting with a 2nd range restricts user to the circular arcs. 3rd range constrains user to 1 of the 2 points. Which point is determined by “sanity” – 1 point obviously wrong.

  6. GDOP • Geometric Dilution of Precision • Depends on user-satellite geometry • TDOP • HDOP • VDOP

  7. DGPS • Errors in one location are similar to errors in surrounding error • Corrections broadcast from Reference Station to Mobile Station over Data Link

  8. WAAS/EGNOS/MTSAT • 25 ground reference stations across US • Master ground station broadcasts corrections to geo-stationary satellites

  9. LAAS • Similar to WAAS • Ground reference stations in vicinity of airport • Line-of-sight VHF radio link to plane • Can be augmented with pseudolites

  10. GLONASS • 24 satellite constellation in 3 orbital planes (8 currently active) at 64.8o • Higher inclination of satellite orbits • More availability for higher latitudes (e.g. Sweden and polar regions) • Better accuracy for civilians (pre-SA) • Some devices use GLONASS and GPS together

  11. Galileo • 30 satellite constellation • 27 operational + 3 active spares • 3 MEO orbital planes of 56o inclination • Planned active by 2008 • Safety critical systems • Quality of service guarantees • Business model TBA • Subscriber services • Search and Rescue feature

  12. UWB • Claim - “Communications with precision ranging and positioning ability” • Transmit short discrete pulses instead of modulating code onto carrier signal • Pulses last ~1-2 ns • Distinguish pulses 1-2 ft apart • UWB avoids • Ranging accuracy degradation • Deep fades

  13. Questions & Discussion

  14. UWB revisited (1) • Not sinewave – millions pulses per second • Time coded to make noise-like • Channelization • Anti-jamming • Smooths spectrum • Pulse Polarity modulation

  15. UWB revisited (2) • Time of flight precisely measured by phase shift of code • Receiver locks to coded sequence of transmitter with accuracy < 100 ps

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