Title: GROUND BASED AUGMENTATION SYSTEM Frequency Planning Criteria Presentation GNSS 3'3 by Christophe DEH
1GROUND BASED AUGMENTATION SYSTEMFrequency
Planning CriteriaPresentation GNSS 3.3 by
Christophe DEHAYNAIN Direction Générale de
lAviation Civile FRANCE
2GROUND BASED AUGMENTATION SYSTEMPresentation
Overview
- GBAS principle
- Why do we need frequency planning criteria ?
- How the ICAO criteria have been established ?
- What are the current criteria ?
- What has still to be done ?
3GBAS principle
- The Ground Based Augmentation System is composed
of 3 segments - the space segment (GPS, GLONASS, GALILEO
satellites) - the ground segment (GBAS ground station)
- the airborne segment (the users equipment)
4GBAS principle
- Objective of the Data Link
- interface between the ground and the airborne
segments - Type of transmitted information
- Pseudo Range Corrections (high rate)
- Integrity parameters (?,B values) (high rate)
- Final Approach Segments description (low rate)
5ICAO GNSSP choice
- ICAO GNSS Panel validated in June 2000 the VHF
D8PSK data Link among five considered options - VHF Nav. 108-117.975 MHz
- D8PSK modulation
- GFSK modulation
- DME UHF band (960-1215 MHz)
- GPS L1 band (1575.42 MHz)
- C band (5030-5150 MHz)
6ICAO GNSSP choice
- VHF Navigation band (108-117.975 MHz)
- 25 KHz channel spacing
- horizontal polarisation (possibility to have
vertical also) - D8PSK modulation
- 31.5Kbit/s rate
- TDMA (Time Division Multiple access) 8 slots
per 0.5 s frame
7Why do we need frequency planning criteria ?
- GBAS Data Link will use Navigation VHF Band
frequencies (108 - 118 MHz) - This frequency band is already used for VOR and
ILS localizer assignations - GBAS, ILS and VOR will coexist during a
transition phase - The three services need to be protected from
mutual interference
8How the ICAO criteria have been established ?
- Determination of minimum Desired/Undesired signal
ratio at which VOR receiver is jammed by GBAS
transmission on co- and adjacent channels (and
vice- versus) - Use of the GNSS SARPS to determine the minimum
Desired/Undesired signal ratio at which GBAS is
jammed by VOR or GBAS transmission on co- and
adjacent channels - Computation of minimum geographical distance
between co- and adjacent VOR/GBAS and GBAS/GBAS
channels transmitters
9Determination of minimum Desired/Undesired signal
ratio at which VOR receiver is jammed by GBAS
transmission on co- and adjacent channels
VOR/ILS desired signals
VOR/ILS receiver under test
ILS/VOR indicator
VDB undesired signals
10Computation of minimum geographical distance
between co- and adjacent VOR/GBAS channels
transmitters
Dw
VOR protected volume
GBAS protected volume
Dvor
DGBAS
GBAS
VOR
Dac
Minimum separation
11Computation of minimum geographical distance
between co- and adjacent VOR/GBAS channels
transmitters (2)
Dac, Dw in km Fdoc in microvolts/meter
12What are the current criteria for VOR to GBAS
separation ?
13What are the current criteria for GBAS to GBAS
separation ?
14What has still to be done ?
- Compatibility criteria for
- ILS Localizer and GBAS in the band 108 - 112 MHz
have still to be defined (ICAO objectives
2004-2005) - VHF AM Communications and GBAS have still to be
defined (ICAO objectives 2004-2005) - VHF VDL Mode 4 and GBAS have still to be defined
(ICAO objectives 2004-2005) - Compatibility criteria for elliptical polarised
GBAS signals need to be defined (No ICAO plan) - Before these criteria are defined, GBAS Data-link
frequencies have to be assigned in a limited band
(112.025 - 116.400 MHz)