Choose a Propagation Model
Propagation models allow you to predict the propagation and attenuation of radio
signals as the signals travel through the environment. Create an object that simulates a
propagation model by using the propagationModel function. Combine propagation models by using the
add function. You can also determine the range and path loss of radio
signals in the simulated models by using the range and pathloss functions.
The following sections describe various propagation and ray tracing models. The tables
in each section list the models that are supported by the
propagationModel function and compare, for each model, the
supported frequency ranges, model combinations, and limitations.
Atmospheric
Atmospheric propagation models predict path loss between sites as a function of distance. These models assume line-of-sight (LOS) conditions and disregard the curvature of the Earth, terrain, and other obstacles.
| Model | Description | Frequency | Combinations | Limitations |
|---|---|---|---|---|
Free space (FreeSpace) | Ideal propagation model with clear line of sight between transmitter and receiver | No enforced range | Can be combined with rain, fog, and gas | Assumes line of sight |
Rain (Rain) | Propagation of a radio wave signal and its path loss in rain. For more information, see [3]. | 1 GHz to 1000 GHz | Can be combined with any other propagation model | Assumes line of sight |
Gas (Gas) | Propagation of radio wave signal and its path loss due to oxygen and water vapor. For more information, see [5]. | 1GHz to 1000 GHz | Can be combined with any other propagation model | Assumes line of sight |
Fog (Fog) | Propagation of the radio wave signal and its path loss in cloud and fog. For more information, see [2]. | 10GHz to 1000 GHz | Can be combined with any other propagation model | Assumes line of sight |
Empirical
Like atmospheric propagation models, empirical models predict path loss as a function of distance. Unlike atmospheric models, the close-in empirical model supports non-line-of-sight (NLOS) conditions.
Terrain
Terrain propagation models predict point-to-point path loss between sites over irregular terrain, including buildings. These models calculate path loss from free-space loss, terrain and obstacle diffraction, ground reflection, atmospheric refraction, and tropospheric scatter. They provide path loss estimates by combining physics with empirical data statistics.
To predict path loss in scenes that feature buildings, such as urban environments, consider using a ray tracing propagation model. Compared to terrain models, ray tracing models better capture multipath effects.
| Model | Description | Frequency | Combinations | Limitations |
|---|---|---|---|---|
Longley-Rice (LongleyRice) | Also known as Irregular Terrain Model (ITM). For more information, see [4]. | 20 MHz to 20 GHz | Can be combined with rain, fog, and gas |
|
TIREM (TIREM (Antenna Toolbox)) | Terrain Integrated Rough Earth Model™ | 1 MHz to 1000 GHz | Can be combined with rain, fog, and gas |
|
Ray Tracing
Ray tracing models, represented by RayTracing objects, compute propagation paths in
3-D environments. The models determine the path loss and phase shift of each path
using electromagnetic analysis, including tracing the horizontal and vertical
polarizations of a signal through the propagation path. The path loss calculations
include free-space loss, reflection losses, and edge diffraction losses.
While the other supported models compute single propagation paths, ray tracing models compute multiple propagation paths.
These models support both 3-D outdoor and indoor environments.
For more information about ray tracing models, see Ray Tracing for Wireless Communications.
| Ray Tracing Method | Description | Frequency | Combinations | Limitations |
|---|---|---|---|---|
| Shooting-and-bouncing rays (SBR) |
| 100 MHz to 100 GHz | Can be combined with rain, fog, and gas | Does not include effects from corner or vertex diffraction, refraction, or diffuse scattering |
| Image |
| 100 MHz to 100 GHz | Can be combined with rain, fog, and gas | Does not include effects from diffraction, refraction, or diffuse scattering |
References
[1] Sun, Shu, Theodore S. Rappaport, Timothy A. Thomas, Amitava Ghosh, Huan C. Nguyen, Istvan Z. Kovacs, Ignacio Rodriguez, Ozge Koymen, and Andrzej Partyka. “Investigation of Prediction Accuracy, Sensitivity, and Parameter Stability of Large-Scale Propagation Path Loss Models for 5G Wireless Communications.” IEEE Transactions on Vehicular Technology 65, no. 5 (May 2016): 2843–60. https://doi.org/10.1109/TVT.2016.2543139.
[2] International Telecommunications Union Radiocommunication Sector. Attenuation due to clouds and fog. Recommendation P.840-6. ITU-R, approved September 30, 2013. https://www.itu.int/rec/R-REC-P.840/en.
[3] International Telecommunications Union Radiocommunication Sector. Specific attenuation model for rain for use in prediction methods. Recommendation P.838-3. ITU-R, approved March 8, 2005. https://www.itu.int/rec/R-REC-P.838/en.
[4] Hufford, George A., Anita G. Longley, and William A.Kissick. A Guide to the Use of the ITS Irregular Terrain Model in the Area Prediction Mode. NTIA Report 82-100. National Telecommunications and Information Administration, April 1, 1982.
[5] International Telecommunications Union Radiocommunication Sector. Attenuation by atmospheric gases. Recommendation P.676-11. ITU-R, approved September 30, 2016. https://www.itu.int/rec/R-REC-P.676/en.
[6] Yun, Zhengqing, and Magdy F. Iskander. “Ray Tracing for Radio Propagation Modeling: Principles and Applications.” IEEE Access 3 (2015): 1089–1100. https://doi.org/10.1109/ACCESS.2015.2453991.
[7] Schaubach, K.R., N.J. Davis, and T.S. Rappaport. “A Ray Tracing Method for Predicting Path Loss and Delay Spread in Microcellular Environments.” In [1992 Proceedings] Vehicular Technology Society 42nd VTS Conference - Frontiers of Technology, 932–35. Denver, CO, USA: IEEE, 1992. https://doi.org/10.1109/VETEC.1992.245274.
