This Recommendation contains a general purpose wide-range model for terrestrial propagation which predicts basic transmission loss due to both signal enhancements and fading over effectively the range from 0% to 100% of an average year. This makes the model particularly suitable for Monte-Carlo methods, and studies in which it is desirable to use the same propagation model, with no discontinuities in its output, for signals which may be either wanted or potentially interfering. The model covers the frequency range from 30 MHz to 50 GHz. The model is believed to be most accurate from about 3 km to 1 000 km. At shorter distances, the effect of clutter (buildings, trees, etc.) will tend to dominate unless the antenna heights are high enough to given an unobstructed path. There is no specific lower limit, although the path length must be greater than zero. A prediction of basic transmission loss less than 20 dB should be considered unreliable. Similarly, there is no specific maximum distance. Antennas heights above ground level must be greater than zero. There is no specific maximum height above ground. The method is believed to be reliable for antenna altitudes up to 8 000 m above sea level.
Description of the model
This Recommendation provides a calculation for basic transmission loss across the full distribution of time percentages, defined as the percentage of an average year for which a given loss value is not exceeded. For interference analysis, this Recommendation should be used by choosing small values for time percentages. The propagation mechanisms (including free-space loss, diffraction, and troposcatter) in Recommendation ITU-R P.2001 are similar or identical to those in Recommendation ITU-R P.452 and the comments given above in relation to Recommendation ITU-R P.452 about frequency applicability apply to Recommendation ITU-R P.2001 as well. The model also includes clear-air enhancements and fading, precipitation fading, anomalous/layer refraction, and ionospheric propagation by sporadic-E that may be significant for long paths and low frequencies.
Only flat terrain profile (with terrain height equal zero masl) and inland paths are implemented in SEAMCAT.
Note that the only substantial difference between Recommendations ITU-R P.2001-4 and ITU-R P.2001-3 is in the free-space basic transmission loss which in new version is aligned with Recommendation ITU-R P.525.
Input parameters
The input parameters for the propagation model ITU-R P.2001-4 are shown in Figure 1 and defined in Table 1. The remaining parameters (such as frequency, Tx/Rx antenna heights and distance) are taken directly from the local environments and SEAMCAT workspace.
