raytrace
Display or compute RF propagation rays
Description
The raytrace function plots or computes propagation
paths by using ray tracing with surface geometry defined by the Map argument. The function color-codes each propagation path according
to the received power (dBm) or path loss (dB) from the transmitter site to the receiver
site. The ray tracing analysis includes surface reflections and edge diffractions, but
does not include effects from corner diffraction, refraction, or diffuse scattering.
This function supports frequencies from 100 MHz to 100 GHz. For more information, see
Choose a Propagation Model.
raytrace(
displays the propagation paths from the transmitter site tx,rx)tx to
the receiver site rx in the current Site Viewer. By default,
the function uses the shooting and bouncing rays (SBR) method, finds paths with up
to two reflections and zero diffractions, and discards paths that are more than 40
dB weaker than the strongest path.
raytrace(
finds propagation paths using the ray tracing propagation model
tx,rx,propmodel)propmodel. Ray tracing propagation models enable you to
specify properties such as the maximum number of reflections and diffractions, path
loss thresholds, and building and terrain materials. Create a ray tracing
propagation model by using the propagationModel function.
raytrace(___,
specifies options using one or more name-value arguments, in addition to any
combination of inputs from the previous syntaxes.Name=Value)
rays = raytrace(___)rays.
Examples
Show reflected propagation paths in Chicago using a ray tracing propagation model.
Launch Site Viewer with buildings in Chicago. For more information about the OpenStreetMap® file, see [1].
viewer = siteviewer(Buildings="chicago.osm");Create a transmitter site and a receiver site near two different buildings.
tx = txsite(Latitude=41.8800, ... Longitude=-87.6295, ... TransmitterFrequency=2.5e9); show(tx) rx = rxsite(Latitude=41.8813452, ... Longitude=-87.629771, ... AntennaHeight=30); show(rx)
Show the obstruction to the line-of-sight path.
los(tx,rx)
Display propagation paths with reflections. By default, the raytrace function uses the SBR method and calculates propagation paths with up to two reflections.
raytrace(tx,rx)
Appendix
[1] The OpenStreetMap file is downloaded from https://www.openstreetmap.org, which provides access to crowd-sourced map data all over the world. The data is licensed under the Open Data Commons Open Database License (ODbL), https://opendatacommons.org/licenses/odbl/.
Launch Site Viewer with buildings in Chicago. For more information about the OpenStreetMap® file, see [1].
viewer = siteviewer(Buildings="chicago.osm");
Create a transmitter site on a building.
tx = txsite(Latitude=41.8800, ... Longitude=-87.6295, ... TransmitterFrequency=2.5e9);
Create a receiver site near another building.
rx = rxsite(Latitude=41.881352, ... Longitude=-87.629771, ... AntennaHeight=30);
Create a ray tracing propagation model, which MATLAB® represents using a RayTracing object. By default, the propagation model uses the SBR method and finds propagation paths with up to two surface reflections.
pm = propagationModel("raytracing");Calculate the signal strength using the receiver site, the transmitter site, and the propagation model.
ssTwoReflections = sigstrength(rx,tx,pm)
ssTwoReflections = -54.3151
Plot the propagation paths.
raytrace(tx,rx,pm)
Change the RayTracing object to find paths with up to 5 reflections. Then, recalculate the signal strength.
pm.MaxNumReflections = 5; ssFiveReflections = sigstrength(rx,tx,pm)
ssFiveReflections = -53.3965
By default, RayTracing objects use concrete terrain materials and building materials derived from the OpenStreetMap file. When the OpenStreetMap file does not specify materials, the model uses concrete. Change the building and terrain material types to model perfect electrical conductors.
pm.TerrainMaterial = "PEC"; pm.BuildingsMaterial = "PEC"; ssPerfect = sigstrength(rx,tx,pm)
ssPerfect = -38.9334
Plot the propagation paths for the updated propagation model.
raytrace(tx,rx,pm)
Appendix
[1] The OpenStreetMap file is downloaded from https://www.openstreetmap.org, which provides access to crowd-sourced map data all over the world. The data is licensed under the Open Data Commons Open Database License (ODbL), https://opendatacommons.org/licenses/odbl/.
Launch Site Viewer with buildings in Hong Kong. For more information about the OpenStreetMap® file, see [1].
viewer = siteviewer(Buildings="hongkong.osm");
Create transmitter and receiver sites that model a small cell scenario in a dense urban environment.
tx = txsite(Name="Small cell transmitter", ... Latitude=22.2789, ... Longitude=114.1625, ... AntennaHeight=10, ... TransmitterPower=5, ... TransmitterFrequency=28e9); rx = rxsite(Name="Small cell receiver", ... Latitude=22.2799, ... Longitude=114.1617, ... AntennaHeight=1);
Create a ray tracing propagation model, which MATLAB represents using a RayTracing object. Configure the model to use a low average number of degrees between launched rays, to find paths with up to 5 path reflections, and to use building and terrain material types that model perfect electrical conductors. By default, the model uses the SBR method.
pm = propagationModel("raytracing", ... MaxNumReflections=5, ... AngularSeparation="low", ... BuildingsMaterial="PEC", ... TerrainMaterial="PEC");
Visualize the propagation paths and calculate the corresponding path losses.
raytrace(tx,rx,pm,Type="pathloss") raysPerfect = raytrace(tx,rx,pm,Type="pathloss"); plPerfect = [raysPerfect{1}.PathLoss]
plPerfect = 1×13
104.2656 103.5699 112.0092 109.3137 111.2840 111.9979 112.4416 108.1505 111.2825 111.3905 117.7506 116.5906 117.7638
Set the building and terrain material types to glass and concrete, respectively. Then, revisualize the propagation paths and recalculate the corresponding path losses. The model finds one fewer path because, by default, the model discards paths that are more than 40 decibels weaker than the strongest path. The first path loss value does not change because it corresponds to the line-of-sight propagation path.
pm.BuildingsMaterial = "glass"; pm.TerrainMaterial = "concrete"; raytrace(tx,rx,pm,Type="pathloss") raysMtrls = raytrace(tx,rx,pm,Type="pathloss"); plMtrls = [raysMtrls{1}.PathLoss]
plMtrls = 1×12
104.2656 106.1249 119.2135 121.2269 122.3753 121.5228 126.8929 124.1284 122.7842 127.4910 138.9922 140.4998
Incorporate atmospheric loss by adding rain and gas propagation models to the ray tracing model. Then, revisualize the propagation paths and recalculate the corresponding path losses.
pm = pm + propagationModel("rain") + propagationModel("gas"); raytrace(tx,rx,pm,Type="pathloss") raysAtmospheric = raytrace(tx,rx,pm,Type="pathloss"); plAtmospheric = [raysAtmospheric{1}.PathLoss]
plAtmospheric = 1×12
105.3245 107.1846 121.7988 123.1224 124.9622 124.1119 129.6107 126.0247 125.3746 130.2090 142.9753 144.4831
Appendix
[1] The OpenStreetMap file is downloaded from https://www.openstreetmap.org, which provides access to crowd-sourced map data all over the world. The data is licensed under the Open Data Commons Open Database License (ODbL), https://opendatacommons.org/licenses/odbl/.
This example shows how to:
Scale an STL file so that the model uses units of meters.
View the scaled model in Site Viewer.
Use ray tracing to calculate and display propagation paths from a transmitter to a receiver.
While Cartesian txsite and rxsite objects require position coordinates in meters, STL files can use other units. If your STL file does not use meters, you must scale the model before importing it into Site Viewer.
Import and view an STL file. The file models a small conference room with one table and four chairs. Scale the model by specifying the SceneModelScale name-value argument. For this example, assume that the conversion factor from the STL units to meters is 0.9.
viewer = siteviewer(SceneModel="conferenceroom.stl",SceneModelScale=0.9);
Before R2023b: Read the model into a triangulation object by using the stlread function, scale the coordinates and create a new triangulation object, and then read the new triangulation object into Site Viewer.
Create and display a transmitter site close to the wall and a receiver site under the table. Specify the position using Cartesian coordinates in meters.
tx = txsite("cartesian", ... AntennaPosition=[-1.25; -1.25; 1.9], ... TransmitterFrequency=2.8e9); show(tx,ShowAntennaHeight=false) rx = rxsite("cartesian", ... AntennaPosition=[0.3; 0.2; 0.5]); show(rx,ShowAntennaHeight=false)
Pan by left-clicking, zoom by right-clicking or by using the scroll wheel, and rotate the visualization by clicking the middle button and dragging or by pressing Ctrl and left-clicking and dragging.
Create a ray tracing propagation model for Cartesian coordinates, which MATLAB represents using a RayTracing object. Calculate rays that have up to 1 reflection and 1 diffraction. Set the surface material to wood. By default, the model uses the SBR method.
pm = propagationModel("raytracing", ... CoordinateSystem="cartesian", .... MaxNumReflections=1, ... MaxNumDiffractions=1, ... SurfaceMaterial="wood");
Calculate the propagation paths and return the result as a cell array of comm.Ray objects. Extract and plot the rays.
r = raytrace(tx,rx,pm);
r = r{1};
plot(r)View information about a ray by clicking on it.
Since R2023b
View a 3-D model from a glTF™ file created using RoadRunner. RoadRunner is an interactive editor that lets you design 3-D scenes for simulating and testing automated driving systems.
Create a temporary folder to store a sample glTF file. Download the file into the folder by using the downloadGLTFFile helper function. The helper function is attached to the example as a supporting file.
dataDir = fullfile(tempdir,"IntersectionAndBuildings"); if ~exist(dataDir,"dir") mkdir(dataDir) end downloadGLTFFile(dataDir)
Downloading glTF file. Done.
Specify the name of the binary file. Then, import and view the glTF file using Site Viewer. Site Viewer displays the model using the colors and textures stored in the file.
filename = fullfile(dataDir,"IntersectionAndBuildings.glb");
viewer = siteviewer(SceneModel=filename,ShowEdges=false,ShowOrigin=false);
Site Viewer assigns materials to the surfaces in the scene by matching each material name stored in the file with the name of a supported material. View a subset of the materials and matched materials. By default, ray tracing analysis functions use the materials stored in the MatchedCatalogMaterial variable.
viewer.Materials(1:5,:)
ans=5×2 table
Material MatchedCatalogMaterial
______________ ______________________
"Metal_Trim" "metal"
"Glass" "glass"
"Stone_Trim" "marble"
"Roof_Asphalt" "concrete"
"Bricks_Red" "brick"
Create a transmitter site above a building and a receiver site behind a cluster of buildings. Specify the positions using Cartesian coordinates in meters.
tx = txsite("cartesian",AntennaPosition=[18;38;22]); rx = rxsite("cartesian",AntennaPosition=[-40;-35;1]);
Create a ray tracing propagation model for Cartesian coordinates, which MATLAB® represents by using a RayTracing object. Configure the model to find propagation paths that have up to two reflections (the default) and one diffraction.
pm = propagationModel("raytracing", ... CoordinateSystem="cartesian", ... MaxNumDiffractions=1);
Calculate the propagation paths and return the result as a cell array of comm.Ray objects. Extract the propagation paths from the cell array.
rays = raytrace(tx,rx,pm);
rays = rays{1};Display the transmitter site, the receiver site, and the propagation paths.
show(tx) show(rx) plot(rays)
View information about a path by clicking it. The information box displays the interaction materials.
Input Arguments
Name-Value Arguments
Output Arguments
References
[1] International Telecommunications Union Radiocommunication Sector. Effects of Building Materials and Structures on Radiowave Propagation Above About 100MHz. Recommendation P.2040. ITU-R, approved August 23, 2023. https://www.itu.int/rec/R-REC-P.2040/en.
[2] International Telecommunications Union Radiocommunication Sector. Electrical Characteristics of the Surface of the Earth. Recommendation P.527. ITU-R, approved September 27, 2021. https://www.itu.int/rec/R-REC-P.527/en.
[3] Mohr, Peter J., Eite Tiesinga, David B. Newell, and Barry N. Taylor. “Codata Internationally Recommended 2022 Values of the Fundamental Physical Constants.” NIST, May 8, 2024. https://www.nist.gov/publications/codata-internationally-recommended-2022-values-fundamental-physical-constants.
Extended Capabilities
Version History
Introduced in R2019bWhen you find propagation paths using the SBR method, MATLAB corrects the results so that the geometric accuracy of each path is exact, using single-precision floating-point computations. In previous releases, the paths have approximate geometric accuracy.
For example, this code finds propagation paths between a transmitter and receiver
by using the default SBR method and returns the paths as comm.Ray
objects. In R2022b, the raytrace function finds seven
propagation paths. In earlier releases, the function approximates eight propagation
paths, one of which is a duplicate path.
viewer = siteviewer(Buildings="hongkong.osm"); tx = txsite(Latitude=22.2789,Longitude=114.1625,AntennaHeight=10, ... TransmitterPower=5,TransmitterFrequency=28e9); rx = rxsite(Latitude=22.2799,Longitude=114.1617,AntennaHeight=1); rSBR = raytrace(tx,rx) raytrace(tx,rx)
| R2022b | R2022a |
|---|---|
rSBR =
1×1 cell array
{1×7 comm.Ray}
|
rSBR =
1×1 cell array
{1×8 comm.Ray}
|
Paths calculated using the SBR method in R2022b more closely align with paths calculated using the image method. The image method finds all possible paths with exact geometric accuracy. For example, this code uses the image method to find propagation paths between the same transmitter and receiver.
viewer = siteviewer(Buildings="hongkong.osm"); tx = txsite(Latitude=22.2789,Longitude=114.1625, ... AntennaHeight=10,TransmitterPower=5, ... TransmitterFrequency=28e9); rx = rxsite(Latitude=22.2799,Longitude=114.1617, ... AntennaHeight=1); pm = propagationModel("raytracing",Method="image",MaxNumReflections=2); rImage = raytrace(tx,rx,pm)
rImage =
1×1 cell array
{1×7 comm.Ray}In this case, the SBR method finds the same number of propagation paths as the image method. In general, the SBR method finds a subset of the paths found by the image method. When both the image and SBR methods find the same path, the points along the path are the same within a tolerance of machine precision for single-precision floating-point values.
This code compares the path losses, within a tolerance of
0.0001, calculated by the SBR and image methods.
abs([rSBR{1}.PathLoss]-[rImage{1}.PathLoss]) < 0.0001ans = 1×7 logical array 1 1 1 1 1 1 1
The path losses are the same within the specified tolerance.
As a result, the raytrace function can return different
results in R2022b compared to previous releases.
The function can return a different number of
comm.Rayobjects because it discards invalid or duplicate paths.The function can return different
comm.Rayobjects because it calculates exact paths rather than approximate paths.
