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Frequency Assignment Planning

An overview of methodology and models for radio frequency assignment planning, including free-space and aeronautical standard propagation models. Learn about VHF communication principles, ILS co-channel protection, interference mitigation, and more.

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Frequency Assignment Planning

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

  5. Radio horizon • If both heights hTXand hRXare 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: 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: 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; 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. MID Office, Cairo, 4 – 6 June 2006

  9. VHF COM 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 MID Office, Cairo, 4 – 6 June 2006

  11. INTERFERENCE VICTIM DESIRED SIGNAL 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 UNDESIRED SIGNAL INTERFERENCE SOURCE VOR 2 VOR 1 MID Office, Cairo, 4 – 6 June 2006

  12. INTERFERENCE VICTIM UNDESIRED SIGNALS DESIRED SIGNAL 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 SOURCE(S) DME 2 DME 1 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 MID Office, Cairo, 4 – 6 June 2006

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

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