International Civil Aviation Organization

1
Global Navigation Satellite System(GNSS)
Overview and Spectrum Implementation
International Civil Aviation Organization Spectrum
Seminar Cairo, Egypt June 4-6, 2006
2
Basic GNSS System

• Core Constellations
• GPS
• GLONASS
• Galileo (under development)
• Augmentation Systems
• Aircraft-Based Augmentation System (ABAS)
• Space-Based Augmentation System (SBAS)
• Uses geostationary satellites
• India, Japan, Europe, US
• Ground-Based Augmentation System (GBAS)
• Ground-Based Regional System (GRAS)

3
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
GNSS Ranging and Timing

• Approach tarrival ttransmitted 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 directly in aircraft some
  signals not protected.

5
Satellite Navigations MissionSBAS/GBAS
Implementation
SBAS/GRAS
GBAS
6
L1, L2
Satellite Based Augmentation System (WAAS used as
example)
FAA288-021
7
Ground Based Augmentation System (GBAS)
Architecture
Pseudolite
Pseudolite
GBAS Reference Station (Integrity Accuracy Availab
ility)
Processor GNSS Receiver VHF Transmitter Monit
or Status
Pseudolite
8
Planned GNSS Modernization

• Addition of satellite constellations
• Galileo, additional GLONASS satellites
• Improves user availability
• Addition of civil signals
• 1164-1215 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
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 5.355 and 5.359
• Allow fixed service in GNSS bands in some
  countries
• Countries encouraged to remove their names from
  the footnotes.