# Rural Dominant Path Model

The Dominant Path Model uses a full 3D approach for the path searching, which leads to realistic and accurate results.

The simple approach of the Hata-Okumura Model is clearly visible in the left image. Topography between transmitter and receiver is not considered. In contrast to this case, the Knife-Edge Diffraction Model considers topography, but the effects are too dominant. The shadows behind the hills are too hard, because always the direct ray is considered. This leads to too pessimistic results. The Dominant Path Model uses a full 3D approach for the path searching, which leads to realistic and accurate results.

## Advantages of the Dominant Path Model

- The most important propagation path is computed by using a full 3D approach
- Short computation times
- Accuracy exceeds the accuracy of empirical models

## Algorithm of the Dominant Path Model

The DPM determines the dominant path between transmitter and each receiver pixel. The computation of the path loss is based on the following equation:

- Distance from transmitter to receiver (
*l*) - Path loss exponent (
*p*) - Wave length (lambda)
- Individual interaction losses due to diffractions (
*f*) - Empirically determined loss reduction due to wave guiding ( $\Omega $ )
- Gain of transmitting antenna (
*g*)_{t}

As described above, *l* is length of the path between transmitter and current
receiver location. *p* is the path loss exponent. The value of *p* depends
on the current propagation situation. In areas with vegetation (which is not modeled
in the project) *p* = 2.4 is suggested, whereas in open areas *p* = 2.0 is
reasonable. In addition *p* depends on the breakpoint distance. After the
breakpoint, increased path loss exponents are common due to distortions of the
propagating wave. The function *f* yields the loss (in dB) which is caused by
diffractions. The diffraction losses are accumulated along one propagation path. The
directional gain of the antenna (in direction of the propagation path) is also
considered.

## Configuration of the Dominant Path Model

The following screenshot shows the configuration dialog of the DPM.

- Path Loss Exponents
- The path loss exponents influence the propagation result computed by the DPM significantly. The path loss exponents describe the attenuation with distance. A higher path loss exponent leads to a higher attenuation in same distance. The following figure shows a comparison of three predictions with different path loss values for the LOS area.
- Losses
- Each change in the direction of propagation due to an interaction (diffraction, transmission/penetration) along a propagation path causes an additional attenuation. The maximum attenuation can be defined. The effective interaction loss depends on the angle of the diffraction. It is recommended to select Auto. The transmitter frequency will then be taken into account in the calculation of maximum interaction loss.
- Adaptive Resolution Management
- For acceleration purposes, the DPM offers an adaptive resolution. In close streets a fine resolution is used for the prediction and on large places or open areas DPM switches automatically to a coarse resolution. The prediction time and the memory demand are positively influenced by the adaptive resolution but the accuracy is limited - especially if the highest level for the adaptive resolution is selected by the user.

## Additional Features

- Consideration of clutter in rural/suburban environment: Clutter databases describe the land usage of scenarios and can be considered by the DPM.
- Auto calibration of model parameters.

## Auto Calibration

The model can be calibrated automatically.