Hilly Terrain, Two Ray Empirical

Calculate propagation in a hilly terrain using the empirical two-ray model (ETR).

Model Type

In this rural/suburban scenario, the geometry is described by topography (elevation) and clutter/morpho (land usage). In the tree view, click Topography to view the topography database or Clutter/Morpho to view the land usage.


Figure 1. The topography for the rural/suburban scenario.


Figure 2. The clutter/morpho (land usage) for the rural/suburban scenario.

Sites and Antennas

The topography contains two sites: Site 1 has two directional antennas at the height of 25 m, and Site 2 has an omnidirectional antenna at a height of 50 m. Each antenna operates at a single carrier frequency of 2000 MHz.
Tip: Click Project > Edit Project Parameter and click the Sites tab to view the sites and antennas.

Computational Method

The empirical two-ray model (ETR) model computes the path loss to each pixel based on the assumption that the direct ray and the ground-reflected ray exist. There is no check if the rays exist or if they are shadowed, whereas in the deterministic two ray model, rays are only considered if they are not shadowed.

Knowing that the empirical two-ray model would be too optimistic in shadow regions, a line-of-sight check is performed, and the two-ray model is extended with knife-edge diffraction to handle such regions accurately.
Tip: Click Project > Edit Project Parameter and click the Computation tab to change the model.

Results

Results are computed for each transmitter on a prediction plane of 1.5 m. Propagation results include power coverage of each transmitting antenna, field strength, path loss, and line-of-sight results for both sites. Figure 3 shows an example of power coverage for Site 2 Antenna 1. The large dynamic range is obtained by the addition of knife-edge diffraction for shadow regions. The knife-edge diffraction ensures realistic results where no direct line of sight exists.



Figure 3. Power coverage of Site 1 Antenna 2. Note the large dynamic range. The option of additional Knife-Edge Diffraction ensures realistic results where no direct line of sight exists