A17.6.1.1 Description of the model
- Former user (Deleted)
- Zeljko Tabakovic
Recommendation ITU-R P.452-14 contains an interference prediction procedure for the evaluation of the available propagation loss over unwanted signal paths between stations on the surface of the Earth for frequencies above about 0.1 GHz, with losses not exceeded for time percentages over the range 0.001 ≤ p ≤ 50% and up to a distance limit of 10 000 km.
The models contained within Recommendation ITU-R P.452 work from the assumption that the interfering transmitter and the interfered-with receiver both operate within the surface layer of atmosphere. The procedure includes a complementary set of propagation models which ensure that the predictions embrace all the significant interference propagation mechanisms that can arise. Methods for analysing the radio-meteorological and topographical features of the path are provided so that predictions can be prepared for any practical interference path.
The clutter losses are designated as Aht (dB) and Ahr (dB) for the interferer and interfered-with stations respectively. The additional protection available is height dependent, and is therefore modelled by a height-gain function normalized to the nominal height of the clutter. Appropriate nominal heights are available for a range of clutter types.
The correction applies to all clear-air predictions in this Recommendation, i.e. for all propagation modes and time percentages.
A basic problem in interference prediction (which is indeed common to all tropospheric prediction procedures) is the difficulty of providing a unified consistent set of practical methods covering a wide range of distances and time percentages; i.e. for the real atmosphere in which the statistics of dominance by one mechanism merge gradually into another as meteorological and/or path conditions change. Especially in these transitional regions, a given level of signal may occur for a total time percentage which is the sum of those in different mechanisms. The approach in this procedure has been to define completely separate methods for clear-air and hydrometeor-scatter interference prediction, as described in §§ 4 and 5 respectively of this recommendation.
The clear-air method consists of separate models for diffraction, ducting/layer-reflection, and troposcatter. All three are applied for every case, irrespective of whether a path is LoS or transhorizon. The results are then combined into an overall prediction using a blending technique that ensures for any given path distance and time percentage that the signal enhancement in the equivalent notional line-of-sight model is the highest attainable.
Recommendation ITU-R P.452-14 contains an interference prediction procedure for the evaluation of the available propagation loss over unwanted signal paths between stations on the surface of the Earth for frequencies above about 0.1 GHz, with losses not exceeded for time percentages over the range 0.001 ≤ p ≤ 50% and up to a distance limit of 10 000 km.
The models contained within Recommendation ITU-R P.452 work from the assumption that the interfering transmitter and the interfered-with receiver both operate within the surface layer of atmosphere. The procedure includes a complementary set of propagation models which ensure that the predictions embrace all the significant interference propagation mechanisms that can arise. Methods for analysing the radio-meteorological and topographical features of the path are provided so that predictions can be prepared for any practical interference path.
The clutter losses are designated as Aht (dB) and Ahr (dB) for the interferer and interfered-with stations respectively. The additional protection available is height dependent, and is therefore modelled by a height-gain function normalized to the nominal height of the clutter. Appropriate nominal heights are available for a range of clutter types.
The correction applies to all clear-air predictions in this Recommendation, i.e. for all propagation modes and time percentages.
A basic problem in interference prediction (which is indeed common to all tropospheric prediction procedures) is the difficulty of providing a unified consistent set of practical methods covering a wide range of distances and time percentages; i.e. for the real atmosphere in which the statistics of dominance by one mechanism merge gradually into another as meteorological and/or path conditions change. Especially in these transitional regions, a given level of signal may occur for a total time percentage which is the sum of those in different mechanisms. The approach in this procedure has been to define completely separate methods for clear-air and hydrometeor-scatter interference prediction, as described in §§ 4 and 5 respectively of this recommendation.
The clear-air method consists of separate models for diffraction, ducting/layer-reflection, and troposcatter. All three are applied for every case, irrespective of whether a path is LoS or transhorizon. The results are then combined into an overall prediction using a blending technique that ensures for any given path distance and time percentage that the signal enhancement in the equivalent notional line-of-sight model is the highest attainable.