Emerging Techniques for Broadcasting Future GNSS Services

1
Emerging Techniques for Broadcasting Future GNSS
Services

• Tom Stansell
• Stansell Consulting
• CGSIC Meeting
• September 12, 2005

2
Choosing Between GPS, Galileo, etc.

• Will anyone choose between GPS, Galileo, GLONASS,
  QZSS, etc?
• If GLONASS retains FDMA and if Galileo becomes
  operational, most will ignore GLONASS
• The additional geometry is not worth the cost
• Assuming Galileo success, almost every receiver
  will be compatible with GPS, Galileo, QZSS, and
  SBAS augmentation systems
• With CDMA on common center frequencies, almost no
  additional cost to have the geometric advantages

3
Most Important Improvements

• New better signals on current new frequencies
• But, two main improvements
• Civil codes on two or more frequencies
• Improved signal geometry
• Two frequencies permit iono-free navigation
• There is a code noise penalty
• Sad there are not three common frequencies
• Better geometry provides or improves
• Operation in difficult terrestrial environments
• Autonomous integrity monitoring (RAIM)
• Accuracy because of lower DOPs and

4
Whats Most Important?

• The most important aspects of any GNSS are its
  geometry and the code and carrier measurements
• The data message is important but less vital
• Data is long-lasting, highly redundant, and can
  be provided in other ways
• The first L1C survey revealed interest in other
  types of GPS-related messages
• Long lasting clock and ephemeris for all
  satellites
• Fast clock and ephemeris for quicker TTFF
• Differential corrections and integrity messages

5
Alternate Communication Sources

• Without limiting threshold performance, it is not
  possible to satisfy all communication desires
• But, other communication sources are spreading
• Wireless Internet, 3-G cell phones, satellite
  radio, FM sidetones, SBAS, GBAS, GRAS, etc.
• These can provide specialized GPS messages, e.g.
• Differential corrections and integrity messages
• Long-lasting clock and ephemeris for all
  satellites
• User specific messages (e.g., software updates)
• Predict growth in alternate GPS messaging

6
Summary

• GNSS should focus on providing good geometry,
  robust code and carrier measurements, and robust
  but minimal messages for autonomous navigation
• Alternate communication sources should be
  developed for specialized application needs
• More and better signals will foster GNSS use
  primarily in challenged environments
• Indoors, urban canyons, mining and construction,
  etc.
• More satellites will enhance accuracy and
  integrity
• More dependable performance, Moores Law, and
  MEMS integration will foster expanding use