1. Frequency Assignment Planning
Prepared by Torsten Jacob
ICAO ANB/CNS
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

2. General Methodology
The electromagnetic compatibility of radio equipment should be calculated by the following method:
determine the desired signal level at the victim receiver front end;
determine the resulting level of interference at the victim receiver’s front end;
determine the interactive effects among wanted signals, interference and receiver characteristics for various frequency or distance separations;
determine the appropriate propagation model to be used; and
determine, from these data, a relationship between the frequency separation and distance separation that the interference is considered tolerable.
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

3. Free – Space Propagation Model
The propagation loss that would occur if the antennas were replaced by isotropic antennas located in a perfectly dielectric, homogeneous, isotropic and unlimited environment, the distance between the antennas being retained (see Recommendation ITU-R P.525).
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

4. Aeronautical Standard Propagation Model
Aeronautical standard propagation model (ASPM) is derived from the ITU-R Recommendation P.528. For distances up to the radio horizon, free space propagation is assumed. Beyond the radio horizon, a constant attenuation factor a, which depends on the frequency band under consideration, is used.
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

5. Radio horizon
If both heights hTX and hRX are expressed in feet (ft), the distance d in Nautical Miles (NM), the Earth radius RE = 6360 km and if the atmospheric conditions are assumed to be normal (effective Earth radius factor k = 4/3), the following practical formula can be used to calculate the radio horizon:
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

6. Aeronautical Standard Propagation Model
The propagation loss in dB between two isotropic antennas located in a perfectly dielectric, homogeneous, isotropic and unlimited environment can be calculated as follows:
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

7. VHF COM General principles for VHF voice communication:
To protect a service with a circular operational coverage (circular service), the distances from the edge of the service to another airborne or ground transmitter must be 5 times the range of that circular service; if the other transmitter is below the radio horizon from that service edge and the radio horizon distance is also less than 5 times circular service range then radio horizon distance is to be used;
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

8. VHF COM General principles for VHF voice communication:
To protect a service with a non-circular operational coverage area the ground or airborne transmitter of the other service must be below the radio horizon;
the protection criteria for both the requested service and the existing assignment must be met for a valid assignment.
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

9. VHF COM
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

10. ILS Co-channel protection requirement for ILS localizer
Minimum separation between undesired facility (ILS2) and the Protection Point of the desired facility (ILS1) of 80 NM
ILS localizer protection point at 25 NM distance and
6250 ft height
Minimum separation between second facility
and the protection point of the first facility
80 NM
ILS 1
UNDESIRED
SIGNAL
ILS 2
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

11. VOR Co-channel protection requirement
Minimum uplink free-space desired-to-undesired signal ratio (D/U) of 20 dB at all points within the desired facility’s service volume
INTERFERENCE
VICTIM
UNDESIRED SIGNAL
DESIRED
SIGNAL
INTERFERENCE SOURCE
VOR 2
VOR 1
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

12. DME Ground facilities channel assignment:
Minimum uplink free-space desired-to-undesired signal ratio (D/U) at all points within the desired facility’s service volume
Specific free-space D/U values are selected in order to guarantee an effective post-processing D/U of 8 dB taking into account frequency and code rejection capabilities of the interrogator receiver
INTERFERENCE
VICTIM
UNDESIRED
SIGNALS
INTERFERENCE SOURCE(S)
DESIRED
SIGNAL
DME 2
DME 1
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

13. More information
More information on assignment planning principles for systems such as NDB, GBAS, HF voice and data, VDL Mode 2, 3 and 4 etc can be found at:
ICAO Annex 10
ICAO RF Handbook Doc 9718
Publications of ICAO Regional Offices such as
FMG Frequency Management Manual
National regulations on aeronautical assignment planning
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006

14. Thank You Any questions?
ICAO Radio Spectrum Seminar
MID Office, Cairo, 4 – 6 June 2006