PROPAGATION MODEL

The following methods are proposed for assessment of anticipated interference inside neighbouring country based on established trigger values. Due to the complexity of radiowave propagation nature, different methods are proposed to be considered by administrations and are included here for guidance purposes only.

It should be noted that the following methods provide theoretical predictions based on available terrain knowledge. It is practically impossible to recreate these methods with measurement procedures in the field. Therefore, only some approximation of measurements could be used to check compliance with those methods based on practical measurement procedures. The details of such approximation are not included in this recommendation and should be negotiated between countries based on their radio monitoring practices.

Where appropriate detailed terrain data is available, the propagation model for interference field strength prediction is the latest version of Recommendation ITU-R P.452, For the relevant transmitting terminal, predictions of path loss would be made at x km steps along radials of y km at z degree intervals. The values for those receiver locations within the neighbouring country would be used to construct a histogram of path loss – and if more than 10% of predicted values exceed the threshold the station should be required to be coordinated.

Values for x, y, z and path specific field strength levels are to be agreed between the administrations concerned.

If it is not desirable to utilise detailed terrain height data for the propagation modelling in the border area, the basic model to be used to trigger coordination between administrations and to decide, if co-ordination is necessary, is Recommendation ITU-R P.1546, "Method for point to area predictions for terrestrial services in the frequency range 30 to 3000 MHz". This model is to be employed for 50% locations, 10% time and using a receiver height of 3m.

For specific reception areas where terrain roughness adjustments for improved accuracy of field strength prediction are needed, administrations may use correction factors according to terrain irregularity and/or an averaged value of the TCA parameter in order to describe the roughness of the area on and around the coordination line.

Administrations and/or operators concerned may agree to deviate from the model by mutual consent5.

3e.g. as used by members of the HCM-Agreement

In the case where greater accuracy is required, administrations and operators may use the area calculation below.

For calculations, the pixels of a given geographical area to be agreed between the administrations concerned in a neighbouring country are taken into consideration.

For the relevant base station, predictions of path loss should be made for all the pixels of a given geographical area from a base station and at a receiver antenna height of 3m above ground.

For evaluation, only 10 percent of the number of geographical areas between the borderline (including also the borderline) and the 6 km line itself inside the neighbouring country may be interfered by higher field strength than the trigger field strength value given for the borderline at a height of 3 m above ground;

only 10 percent of the number of geographical areas between the 6 km (including also 6km line) and 12 km line inside the neighbouring country may be interfered by higher field strength than the trigger field strength value given for the 6 km line at a height of 3 m above ground. It is recommended that during area calculations not only detailed terrain data but also clutter data be considered. Use of correction factors for clutter is crucial where the border area is "open" or "quasi-open" from the point of view of clutter or where the interfering base station is just a few kilometres from a borderline.

If the distance between a base station and a terrain point of a borderline is closer than or equal to 1 km, free space propagation model needs to be applied. Furthermore, if there is no terrain obstacle within the 1st Fresnel zone, also the free space propagation model should be applied.

If clutter data is not available, it is proposed to extend the usage of free space propagation model to a few kilometres, depending on the clutter situation in border areas.

For area type interference calculations, propagation models with path specific terrain correction factors are recommended (e.g. Recommendation ITU–R P.1546 with the terrain clearance angle correction factor TCA, HCM4A method with the terrain clearance angle correction factor or Recommendation ITU–R P.1812).

As to correction factors for clutters "open area" and "quasi-open area", 20 dB and 15 dB should be used respectively. Recommendation ITU–R P.1406 should be used if a finer selection of clutter is required.

It must be noted that terrain irregularity factor Δh is not recommended to be used in area calculations. Administrations and/or Licensees concerned may agree to deviate from the models by mutual consent.

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5 Such as in use by members of the HCM4A - Agreement