raytrace

Display or compute RF propagation rays

Since R2019b

Syntax

raytrace(tx,rx)

raytrace(tx,rx,propmodel)

raytrace(___,Name,Value)

rays = raytrace(___)

Description

The raytrace function plots or computes propagation paths by using ray tracing with surface geometry defined by the 'Map' property. 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(tx,rx) displays the propagation paths from the transmitter site 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(tx,rx,propmodel) finds propagation paths using the ray tracing propagation model 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(___,Name,Value) specifies options using one or more name-value arguments, in addition to any combination of inputs from the previous syntaxes.

rays = raytrace(___) returns the propagation paths in rays.

Examples

Obstructed and Reflected Paths Using Ray Tracing

Show reflected propagation paths in Chicago using a ray tracing propagation model.

Launch Site Viewer with buildings in Chicago. For more information about the osm 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 osm 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/.

Signal Strength Using Ray Tracing Propagation Model

Launch Site Viewer with buildings in Chicago. For more information about the osm 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 = -54.3015

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 = -53.3889

By default, RayTracing objects assume that building and terrain materials are concrete. Change the building and terrain material types to model perfect electrical conductors.

pm.BuildingsMaterial = "perfect-reflector";
ssPerfect = sigstrength(rx,tx,pm)

ssPerfect = -39.6711

Plot the propagation paths for the updated propagation model.

raytrace(tx,rx,pm)

Appendix

[1] The osm 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/.

Path Loss Due to Material Reflection and Atmosphere

Launch Site Viewer with buildings in Hong Kong. For more information about the osm 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","perfect-reflector", ...
    "TerrainMaterial","perfect-reflector");

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  111.3904  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  106.1290  119.2409  121.2488  122.4103  121.5566  126.9462  124.1624  122.8190  127.5473  139.0664  140.5822

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  107.1887  121.8261  123.1442  124.9972  124.1457  129.6641  126.0587  125.4094  130.2653  143.0496  144.5656

Appendix

[1] The osm 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/.

Visualize Ray Tracing in Conference Room

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 might use other units. If your STL file does not use meters, you must scale the model before importing it into Site Viewer.

Read an STL file as a triangulation object. The file models a small conference room with one table and four chairs.

TR = stlread("conferenceroom.stl");

Scale the coordinates and create a new triangulation object. For this example, assume that the conversion factor from the STL units to meters is 0.9.

scale = 0.9;
scaledPts = TR.Points * scale;
TR_scaled = triangulation(TR.ConnectivityList,scaledPts);

View the new triangulation object using Site Viewer. Alternatively, you can save the new triangulation object as an STL file by using the stlwrite function.

viewer = siteviewer("SceneModel",TR_scaled);

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.

Input Arguments

tx — Transmitter site

txsite object | array of txsite objects

Transmitter site, specified as a txsite object or an array of txsite objects. If you specify an array, then the function plots propagation paths from each transmitter to each receiver site.

rx — Receiver site

rxsite object | array of rxsite objects

Receiver site, specified as an rxsite object or an array of rxsite objects. If you specify an array, then the function plots propagation paths from each transmitter to each receiver site.

propmodel — Ray tracing propagation model

"raytracing" (default) | RayTracing object

Ray tracing propagation model, specified as "raytracing" or as a RayTracing object. The default is "raytracing", which uses the 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.

Create a RayTracing object by using the propagationModel function. RayTracing objects enable you to specify properties such as the ray tracing method, the maximum number of reflections and diffractions, path loss thresholds, and building and terrain materials.

For information about the differences between ray tracing methods, see Choose a Propagation Model.

Data Types: char | string

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: raytrace(tx,rx,Type="pathloss") color-codes paths based on path loss.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: raytrace(tx,rx,"Type","pathloss") color-codes paths based on path loss.

Type — Type of quantity to plot

"power" (default) | "pathloss"

Type of quantity to plot, specified as one of these options:

• "power" — Color-code paths based on the received power in dBm.

• "pathloss" — Color-code paths based on path loss in dB.

The function uses a modified version of the Friis transmission equation to calculate received power (in logarithmic units):

$$P_{rx}=P_{tx}+G_{tx}+G_{rx}-L-L_{tx}-L_{rx}$$

where:

• P_rx is the received power at the receiver.

• P_tx is the transmit power specified by the TransmitterPower property of the transmitter site.

• G_tx is the absolute antenna gain of the transmitter site in the direction of the angle-of-departure (AoD).

• G_rx is the absolute antenna gain of the receiver site in the direction of the angle-of-arrival (AoA).

• L is the path loss between the transmitter site and the receiver site.

• L_tx is the system loss specified by the SystemLoss property of the transmitter site.

• L_rx is the system loss specified by the SystemLoss property of the receiver site.

Data Types: char | string

PropagationModel — Type of propagation model for ray tracing analysis

"raytracing" (default) | RayTracing object

Propagation model, specified as "raytracing" or as a RayTracing object. The default is "raytracing", which uses the 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.

Create a RayTracing object by using the propagationModel function. RayTracing objects enable you to specify properties such as the ray tracing method, the maximum number of reflections and diffractions, path loss thresholds, and building and terrain materials.

For information about the differences between ray tracing methods, see Choose a Propagation Model.

Data Types: char | string

ColorLimits — Color limits for colormap

two-element numeric row vector

Color limits for the colormap, specified as a two-element numeric row vector of the form [min max].

The units and the default value depend on the value of Type:

• "power"– Units are in dBm, and the default value is [-120 -5].

• "pathloss"– Units are in dB, and the default value is [45 160].

The color limits indicate the values that map to the first and last colors in the colormap. The function does not plot propagation paths with values that are below the minimum color limit.

Data Types: double

Colormap — Colormap for coloring propagation paths

"jet" (default) | colormap name | M-by-3 array of RGB

Colormap for coloring the propagation paths, specified as a colormap name or as an M-by-3 array of RGB triplets that define M individual colors. For more information about colormap names, see colormap.

Data Types: char | string | double

ShowLegend — Show color legend in Site Viewer

true or 1 (default) | false or 0

Show color legend in Site Viewer, specified as a numeric or logical 1 (true) or 0 (false).

Map — Map for visualization or surface data

siteviewer object | triangulation object | string scalar | character vector

Map for visualization or surface data, specified as a siteviewer object, a triangulation object, a string scalar, or a character vector. Valid and default values depend on the coordinate system.

Coordinate System	Valid map values	Default map value
"geographic"	A siteviewer objecta. A terrain name, if the function is called with an output argument. Valid terrain names are "none", "gmted2010", or the name of the custom terrain data added using addCustomTerrain.	The current siteviewer object or a new siteviewer object if none are open. "gmted2010", if the function is called with an output.
"cartesian"	"none". A siteviewer object. The name of an STL file. A triangulation object.	"none".
a Alignment of boundaries and region labels are a presentation of the feature provided by the data vendors and do not imply endorsement by MathWorks®.

Data Types: char | string

Output Arguments

rays — Ray configuration

M-by-N cell array of comm.Ray objects

Ray configuration, returned as a M-by-N cell array of comm.Ray objects, where M is the number of transmitter sites and N is the number of receiver sites. Each cell element is a row vector of comm.Ray objects that represent the propagation paths (rays) found between the corresponding transmitter site and receiver site.

Within each row vector, the function sorts the comm.Ray objects alphabetically by the first interaction type. When the first interaction type for multiple rays is the same, the function sorts according to the second interaction type and repeats this behavior for succeeding repeated interaction types. When multiple comm.Ray objects have the same number and types of interactions in the same order, the function sorts the objects by increasing propagation distance. If a line-of-sight path exists, the function includes it as the first element.

Version History

Introduced in R2019b

R2023a: Ray tracing models discard paths based on path loss

Ray tracing propagation models discard propagation paths based on path loss thresholds. By default, when you specify the propmodel input argument as "raytracing" or a RayTracing object, the propagation model discards paths that are more than 40 dB weaker than the strongest path.

As a result, the raytrace function can return different values in R2023a compared to previous releases. To avoid discarding paths based on relative path loss thresholds, create a RayTracing object (by using the propagationModel function) and set its MaxRelativePathLoss property to Inf. Then, use the object as input to the raytrace function.

R2023a: Ray tracing with SBR method calculates paths using increased precision

When you find propagation paths by using the raytrace function with a ray tracing model that uses the shooting and bouncing rays (SBR) method, MATLAB^® calculates the results using double-precision floating-point computations. In previous releases, the function used single-precision floating-point computations.

As a result, the raytrace function can return different comm.Ray objects in R2023a compared to previous releases.

R2023a: NumReflections name-value argument has been removed

The NumReflections name-value argument has been removed.

Instead, create a propagation model by using the propagationModel function and specify the MaxNumReflections name-value argument. Then, use the raytrace function with the propagation model as an input. This code shows the recommended workflow.

pm = propagationModel("raytracing",MaxNumReflections=3);
rays = raytrace(tx,rx,pm);

R2022b: SBR method finds paths with exact geometric accuracy

When 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]) < 0.0001

ans =

  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.Ray objects because it discards invalid or duplicate paths.

• The function can return different comm.Ray objects because it calculates exact paths rather than approximate paths.

R2022a: NumReflections name-value argument will be removed

The NumReflections name-value argument issues a warning that it will be removed in a future release.

R2021b: raytrace function uses SBR method

Starting in R2021b, the raytrace function uses the shooting and bouncing rays (SBR) method and calculates up to two reflections by default. In previous releases, the raytrace function uses the image method and calculates up to one reflection.

To display or compute RF propagation rays using the image method instead, create a propagation model by using the propagationModel function. Then, use the raytrace function with the propagation model as input. This example shows how to update your code.

pm = propagationModel('raytracing','Method','image');
raytrace(tx,rx,pm)

For information about the SBR and image methods, see Choose a Propagation Model.

Starting in R2021b, all RF Propagation functions use the SBR method by default and calculate up to two reflections. For more information, see Default modeling method is shooting and bouncing rays method.