Frequency Assignment Planning

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Frequency Assignment Planning

• Prepared by Torsten Jacob
• ICAO ANB/CNS

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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 receivers 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.

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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).

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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.

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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

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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

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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

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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.

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VHF COM
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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
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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 facilitys service volume

UNDESIRED SIGNAL
INTERFERENCE SOURCE
VOR 2
VOR 1
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DME

• Ground facilities channel assignment
• Minimum uplink free-space desired-to-undesired
  signal ratio (D/U) at all points within the
  desired facilitys 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 SOURCE(S)
DME 2
DME 1
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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

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Thank You Any questions?