Urban Propagation Wireless InSite RT Model
The Urban Propagation Wireless InSite RT model offers a selection of a deterministic model and four empirical models for calculating path loss between two locations in an urban environment. The deterministic model, Triple Path Geodesic, is developed by Remcom, as a derivative of their Wireless InSite 3D propagation loss module, Wireless InSite Real Time.
The Triple Path Geodesic model is a rapid urban propagation model that uses the buildings' 3D geometry data to define an urban environment. The 3D geometry data is used to compute wedge diffractions. The Triple Path Geodesic model produces higher fidelity results than empirical models but at greatly reduced computation times compared to full physics-based models. For more information on the fidelity of Remcom's Wireless InSite Real Time module,
The Urban Propagation Wireless InSite RT model accounts for the directional gains of complex transmitter and complex receiver antennas for computing propagation field strengths.
The following frequency and STK object settings are recommended or required for analysis with the Triple Path Geodesic model:
- Frequency. Frequency cannot go below 100 MHz. There is no upper limit restriction; however, above 7 GHz, predictions can become more sensitive to the finer resolution building details that may not be present in the shapefile or in the model's internal, simplified geometry.
- Height Above Ground. Provided that both transmitter and receiver are above ground, there is no height restriction. However, prediction fidelity is reduced if both the transmitter and receiver are on or close to the ground (less than one meter) since ground conditions that are important to the analysis (e.g., ground cancellation) are not included.
- Line of Sight and Az-El Mask constraints. It is recommended that you do not enable STK Line of Sight and Az-El Mask constraints. The Triple Path Geodesic model of the Urban Propagation Extension employs a higher-fidelity algorithm to simulate RF propagation in an urban environment than a simple line-of-sight prediction. In particular, the model has the capability to make signal attenuation predictions in situations where line-of-sight transmission is obscured, by considering three of the most significant paths of diffracted energy around buildings and over terrain. The use of Line of Sight and Az-El/terrain mask constraints is therefore not appropriate when using the Triple Path Geodesic model.
For information on the recommended shapefile types, see Shapefile Requirements for the Urban Propagation Extension.
Click here for step-by-step instructions on modeling propagation loss in an urban environment.
In STK 10.0.1, access sampling was increased for the Urban Propagation model to help capture small and sudden variations in visibility and the constraint figures of merit computations. It is, however, advised that you review your scenario objects' dynamics and adjust the sampling step size on the Access Advanced properties page, if needed.
You can set the following parameters for the Urban Propagation Wireless InSite RT model:
| Option | Description |
|---|---|
| Calculation Method |
Select a propagation model to calculate path loss between two locations in an urban environment. All models, except for TPGEODESIC, perform sub-millisecond calculations. TPGEODESIC performs in the 1.5 millisecond range. All calculation models require building geometry data. Deterministic Model The deterministic model, which is the default, is the preferred model. It produces higher fidelity results than empirical models.
Triple Path Geodesic returns the no data value unless this restriction is met: transmitter and receiver must be outside of buildings and above ground. The TPGEODESIC model provides good general coverage of cityscapes, between any pair of antennas not located underground or indoors. Empirical Models Select an empirical model if you want ultra-fast characterization of urban performance.
In some situations, a model may return a no data value rather than a path loss value (for example, if a receiver is underground). Reference for HATA and COST-HATA: Parsons, J.D., The Mobile Radio Propagation Channel Second Edition, 2000 John Wiley & Sons, Ltd. ISBN 0 471 98857 X. |
| Enable Ground Reflection | Enable this option if you want the Urban Propagation Wireless InSite RT model to consider ground reflection when computing the direct line of sight (LOS) path. When there is no direct line of sight (for example, when the path is obstructed by a building), ground reflection is not applicable. |
| Urban Geometry Data File |
Browse to the shapefile (.shp) that will be used in calculating path loss. It is recommended that the shapefile be limited to a maximum range of three square kilometers. The shapefile may contain holes in its building polygons (e.g., courtyards, shafts, and plazas) but those holes are not recognized either analytically or graphically by the Urban Propagation Extension. For additional guidelines on selecting shapefiles and using urban data, see Obtaining Urban Terrain Data and Shapefile Requirements. In cases where one of the assets is located outside of the shapefile geographic extents, the urban propagation model specified in the Calculation Method field is used to model the propagation loss along the portion of the signal path that is within the shapefile geographic extents, and the latest ITU-R P676 model is used from the border of the shapefile to the asset. The STK Urban Propagation Model does not support UTM coordinate-based geometry shape files. |
| Projection/Horizontal Datum | Select the horizontal coordinate reference. |
| Building Height Data Attribute | Select the data attribute in the Urban Geometry Data file that provides the building height. |
| Building Height Reference Method | Specify the method for determining the height of buildings:
When HeightAboveTerrain is used, the calculation determines a building height relative to terrain. Buildings on irregular terrain may have corners at different terrain elevations. The Urban Propagation Extension adjusts building elevations until the first vertex touches the terrain and then extrudes the building walls until the building is in contact with the terrain at every point along the base of the building. The calculated building height becomes the minimum height of the building above irregular terrain. |
| Building Height Unit | Specify whether the building height is given in meters or feet. |
| Override Geometry Tile Origin | The origin of the urban geometry data coordinates displays in the Latitude and Longitude fields. You have the option to relocate the geometry data reference origin to a different location by overriding the data read from the file. |
| Use Terrain Data |
If terrain is loaded into your scenario, enable this option to incorporate the effect of terrain in your urban propagation analysis. If disabled, the analysis instead uses mean sea level as its ground surface. Thirty-meter resolution terrain is a good representation of terrain. Having terrain with a high resolution requires a very large number of samples and a large amount of memory to process that terrain. For example, moving from thirty-meter resolution terrain to one-meter resolution terrain will create 900 times more samples, and will use more processing time and memory. |
| Min Required Terrain Extents |
These latitude and longitude values show the extent of the loaded shapefile and are for informational purposes only. You can use these values to select an appropriate terrain source to cover the minimum extents for an urban propagation loss computation using terrain. |
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