A17.6.2.1 Description of the model

Recommendation ITU-R P.452-16 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 to 50 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.

Recommendation ITU-R P.452 considers different propagation mechanisms, such as line-of-sight, diffraction, tropospheric scatter, surface ducting, elevated layer reflection and refraction and combines them into an overall prediction in which the statistics of dominance by one mechanism merge gradually into another. SEAMCAT P.452-16 implementation allows the user to choose to compute the diffraction-only portion of the propagation loss.

SEAMCAT Specific Implementation

According to Recommendation ITU-R P.452, the distance between the transmitter and the receiver is defined along the great circle path (2D) and it does not take into account the antenna height difference when computing line-of-sight propagation losses. This may lead to basic transmission loss values that are smaller than the free space loss in some rare scenarios where the path distance between transmitter and receiver is short and the difference in their antenna heights is significant. For this reason, the SEAMCAT specific implementation uses 3D distance d_{3D} between the transmitter and the receiver in the line-of-sight propagation equations of Recommendation ITU-R P.452-16 (Section 4.1) instead of the 2D distance d:

SEAMCAT propagation model P.452-16 implements also clutter loss following the method of application as described in Recommendation ITU-R P.452-16: (i) the basic propagation loss is first computed for the portion of the path between the positions of Tx and Rx clutter, considering nominal clutter heights as antenna heights; (ii) the additional loss due to protection from local clutter is then added to the previously computed basic propagation loss. There is a predefined set of clutter (ground-cover) categories that the user can choose from: Suburban, Dense suburban, Urban, Dense urban, High-rise urban, and Industrial zone. The user can also specify other clutter conditions by introducing the corresponding Tx/Rx clutter nominal heights as well as the distances from Tx/Rx antennas.

The additional clutter loss is not suitable if the clutter distance d_k from the respective terminal is not significantly greater than the distance between the terminals d. In SEAMCAT, the clutter loss is computed only if