MAKING ASSIGNMENTS FOR THE GROUND BASED AUGMENTATION SYSTEM GBAS

1
MAKING ASSIGNMENTS FOR THE GROUND BASED
AUGMENTATION SYSTEM (GBAS)

• International Civil Aviation Organization
• Spectrum Seminar
• Nairobi, Kenya
• February 17-19, 2004

2
GBAS Basics

• Carrier frequency 108.025 to 117.950 MHz.
• Channel spacing 25 kHz.
• Each frequency includes 8 assignable timeslots
• Nominally 2 slots used per GBAS
• Therefore multiple GBAS can share same frequency
• Broadcast range 20 nm, omnidirectional
• One GBAS station may serve multiple
  close-proximity airports if coverage can be
  maintained
• More detail in Annex 10, Volume 1, 3.7.3.5

3
Channel Assignment Criteria

• GBAS/ILS and GBAS/VHF Comm criteria under
  development
• Until completed, only use band 112.050-117.900
  MHz
• GBAS/VOR and GBAS/GBAS criteria specified in
  Annex 10, Volume 1, Attachment D, 7.2.1

4
Developing Geographical Separation Criteria

• Testing Determines required Pd/Pu for proper
  operation.
• Separate from the undesired station such that
  the required Pd/Pu is satisfied at the edge of
  the desired coverage volume

Resultant distance d is the required geographical
separation
5
 
Typical GBAS/GBAS Separation Criteria
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Example GBAS/VOR Separation Distances