sigstrength

Received signal strength

Syntax

ss = sigstrength(rx,tx)

ss = sigstrength(rx,tx,propmodel)

ss = sigstrength(___,Name,Value)

Description

ss = sigstrength(rx,tx) returns the signal strength in power units (dBm) at the receiver site due to the transmitter site.

ss = sigstrength(rx,tx,propmodel) returns the signal strength at the receiver site using the specified propagation model. Specifying a propagation model is the same as specifying the PropagationModel name-value argument.

ss = sigstrength(___,Name,Value) specifies options using name-value arguments, in addition to any combination of arguments from the previous syntaxes. For example, "Type","efield" returns the signal strength in electric field strength units (dBμV/m).

Examples

Received Power and Link Margin at Receiver

Create a transmitter site.

tx = txsite('Name','Fenway Park', ...
        'Latitude', 42.3467, ...
        'Longitude', -71.0972);

Create a receiver site with sensitivity defined (in dBm).

 rx = rxsite('Name','Bunker Hill Monument', ...
        'Latitude', 42.3763, ...
        'Longitude', -71.0611, ...
        'ReceiverSensitivity', -90);

Calculate the received power and link margin. Link margin is the difference between the receiver's sensitivity and the received power.

ss = sigstrength(rx,tx)

ss = -71.1414

margin = abs(rx.ReceiverSensitivity - ss)

margin = 18.8586

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/.

Input Arguments

rx — Receiver site

rxsite object | array of rxsite objects

Receiver site, specified as a rxsite object. You can use array inputs to specify multiple sites.

tx — Transmitter site

txsite object | array of txsite objects

Transmitter site, specified as a txsite object. You can use array inputs to specify multiple sites.

propmodel — Propagation model to use for path loss calculations

"longley-rice" (default) | "freespace" | "close-in" | "rain" | "gas" | "fog" | "raytracing" | propagation model created using propagationModel

Propagation model to use for the path loss calculations, specified as one of these options:

• "freespace" — Free space propagation model

• "rain" — Rain propagation model

• "gas" — Gas propagation model

• "fog" — Fog propagation model

• "close-in" — Close-in propagation model

• "longley-rice" — Longley-Rice propagation model

• "tirem" — TIREM™ propagation model

• "raytracing" — Ray tracing propagation model that uses the shooting and bouncing rays (SBR) method. When you specify a ray tracing model as input, the function incorporates multipath interference by using a phasor sum.

• A propagation model created using the propagationModel function. For example, you can create a ray tracing propagation model that uses the image method by specifying propagationModel("raytracing","Method","image").

The default value depends on the coordinate system used by the input sites.

Coordinate System	Default propagation model value
"geographic"	"longley-rice" when you use a terrain. "freespace" when you do not use a terrain.
"cartesian"	"freespace" when Map is set to none. "raytracing" when Map is set to the name of an STL file or a triangulation object. The default ray tracing model uses the shooting and bouncing rays (SBR) method.

Terrain propagation models, including "longley-rice" and "tirem", are only supported for sites with a CoordinateSystem value of "geographic".

You can also specify the propagation model by using the PropagationModel name-value pair argument.

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.

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

Example: "Type","power"

Type — Type of signal strength to compute

"power" (default) | "efield"

Type of signal strength to compute, specified as one of these options:

• "power" — The signal strength is in power units (dBm) of the signal at the mobile receiver input.

• "efield"— The signal strength is in electric field strength units (dBμV/m) of signal wave incident on the antenna.

Data Types: char | string

PropagationModel — Propagation model to use for path loss calculations

"freespace" | "close-in" | "rain" | "gas" | "fog" | "longley-rice" | "raytracing" | propagation model created using propagationModel

Propagation model to use for the path loss calculations, specified as one of these options:

• "freespace" — Free space propagation model

• "rain" — Rain propagation model

• "gas" — Gas propagation model

• "fog" — Fog propagation model

• "close-in" — Close-in propagation model

• "longley-rice" — Longley-Rice propagation model

• "tirem" — TIREM propagation model

• "raytracing" — Ray tracing propagation model that uses the shooting and bouncing rays (SBR) method. When you specify a ray tracing model as input, the function incorporates multipath interference by using a phasor sum.

• A propagation model created using the propagationModel function. For example, you can create a ray tracing propagation model that uses the image method by specifying propagationModel("raytracing","Method","image").

The default value depends on the coordinate system used by the input sites.

Coordinate System	Default propagation model value
"geographic"	"longley-rice" when you use a terrain. "freespace" when you do not use a terrain.
"cartesian"	"freespace" when Map is set to none. "raytracing" when Map is set to the name of an STL file or a triangulation object. The default ray tracing model uses the shooting and bouncing rays (SBR) method.

Terrain propagation models, including "longley-rice" and "tirem", are only supported for sites with a CoordinateSystem value of "geographic".

Data Types: char | string

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

ss — Signal strength

M-by-N array

Signal strength, returned as M-by-N array, where M is the number of transmitter sites and N is the number of receiver sites.

The units of ss depend on the value of the Type name-value argument.

• When you specify Type as "power", then ss is in power units (dBm) of the signal at the mobile receiver input.

• When you specify Type as "efield", then ss is in electric field strength units (dBμV/m) of signal wave incident on the antenna.

Version History

Introduced in R2017b

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 sigstrength 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 sigstrength function.

R2022b: Ray tracing functions consider multipath interference

When calculating received power using ray tracing models, the sigstrength function now considers multipath interference by using a phasor sum. In previous releases, the function used a power sum. As a result, the calculations in R2022b are more accurate than in previous releases.

R2021b: "raytracing" propagation models use SBR method

Starting in R2021b, when you use the sigstrength function and specify the propmodel argument or PropagationModel name-value argument as "raytracing", the function uses the shooting and bouncing rays (SBR) method and calculates up to two reflections. In previous releases, the sigstrength function uses the image method and calculates up to one reflection.

To calculate received signal strength using the image method instead, create a propagation model by using the propagationModel function. Then, use the sigstrength function with the propagation model as input. This example shows how to update your code.

pm = propagationModel("raytracing","Method","image");
ss = sigstrength(rx,tx,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.