Using the Scalable Networks Modeling Interface to Analyze Communications Network Performance

STK Pro, STK Premium (Air), STK Premium (Space), or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

Required product install: The EXata network modeling software from Keysight Technologies must be installed and licensed on your computer. See the Scalable Networks Modeling Interface for STK Communications Requirement for version compatibility information.

Required product install: Installation of the Scalable Networks Modeling Interface for STK Communications plugin, which is included with STK UI Plugins on the Ansys STK Resource Utilities install media, is required to complete this tutorial. You can obtain the necessary installer by visiting https://support.agi.com/downloads or by contacting AGI Support.

This lesson requires version 13.0 of the STK software or newer to complete in its entirety. If you have an earlier version of the STK software, you can view a legacy version of this lesson.

Optional product install: A tool to inspect database files compatible with SQLite, such as the DB Browser for SQLite software or the MATLAB programming platform's Database Explorer app, which is part of the MATLAB Database Toolbox add-on, is needed to complete all aspects of this tutorial.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

Capabilities covered

This lesson covers the following capabilities of the Ansys Systems Tool Kit® (STK®) digital mission engineering software:

  • STK Pro
  • Communications

Problem statement

Engineers and technicians want to analyze the performance of a communications network between a convoy and a UAV as the convoy traverses a road through mountainous terrain. You want to analyze the network configuration to resolve any communications issues that may exist between the UAV and the elements of the convoy. You need to consider the dynamic positions of each asset, their antenna pointing parameters, and the communications link budget between the UAV and the convoy's communications vehicle.

Solution

Use the STK software's Communications capability to model the time-dynamic positions and orientations of the vehicles, the characteristics and pointing of sensors and communications assets, and the spatial relationships (for example, line of sight) between objects. Then, use the Scalable Networks Modeling Interface to link the physics-based software geometry capabilities of the STK software to the EXata network modeling software's real-time network simulation capabilities to perform an experiment, which models behavior of the communications network at a granular level, to identify potential issues with network configuration.

What you will learn

Upon completion of this tutorial, you will understand:

  • How to use the Scalable Networks Modeling Interface Scenario Explorer
  • How to run an experiment on a scenario using the Scalable Networks Modeling Interface
  • How to view and export the results of an experiment run in the Scalable Networks Modeling Interface
  • How to map an EXata scenario's configuration to an STK scenario using the Scalable Networks Modeling Interface Config Importer

Downloading the required starter scenario

A scenario containing preconfigured STK objects has been created for you to allow you to focus on using the Scalable Networks Modeling Interface plugin.

  1. Download the zipped folder here: https://support.agi.com/download/?type=training&dir=sdf/help&file=ScalableTutorial.zip

    If you are not already logged in, you will be prompted to log in to agi.com to download the file. If you do not have an agi.com account, you will need to create one. The user approval process can take up to three (3) business days. Please contact support@agi.com if you need access sooner.

  2. Navigate to the downloaded folder.
  3. Right-click on ScalableTutorial.zip.
  4. Select Extract All... in the shortcut menu.
  5. Set the Files will be extracted to this folder: path to the location of your choice. The default path is C:\Users\<username>\Downloads\ScalableTutorial.zip).
  6. Click Extract.
  7. Go to the chosen folder.
  8. ScalableTutorial.vdf will be in the extracted folder.

Opening the starter scenario

Open the downloaded scenario in the STK application.

  1. Launch the STK application ().
  2. Click Open a Scenario () in the Welcome to STK dialog box.
  3. Browse to location of your extracted VDF file.
  4. Select ScalableTutorial.vdf.
  5. Click Open.

Saving the VDF as a scenario

Save and extract the VDF data in the form of a scenario folder. When you save a VDF in the STK application, it will save in its originating format. That is, if you open a VDF, the default save format will be a VDF (.vdf). If you want to save and extract a VDF as a scenario folder, you must change the file format by using the Save As feature. This will create a permanent scenario file complete with child objects and any additional files packaged with the VDF.

  1. Select the File menu.
  2. Select Save As....
  3. Select the STK User folder in the navigation pane when the Save As dialog box opens.
  4. Select the ScalableTutorial folder.

    5. A folder with the same name as the VDF was created for you when you opened the VDF in the STK application. This folder contains the temporarily unpacked files from the VDF.

  5. Click Open.
  6. Select Scenario Files (*.sc) as the Save as type.
  7. Select the ScalableTutorial Scenario file in the file browser.
  8. Click Save.
  9. Click Yes when the Confirm Save As dialog box opens to overwrite the existing scenario file in the folder and to save your scenario.

The following file will be extracted to your scenario folder:

  • ScalableNetworks_Tutorial.config

When saving a VDF containing external files as a scenario folder, you must extract its contents to the scenario folder the STK application automatically creates for you in the STK User folder. This allows files packaged with the VDF, such as data files, reports, presentations, HTML pages, scripts, spreadsheets, and other files, to unpack to the scenario folder. If you save the VDF as a scenario folder in another location, these additional files will not be included. See the Permanently Extracting a VDF as a Scenario Folder and VDF Setup Considerations pages for more information.

Save () often during this lesson!

Viewing the terrain for situational awareness

You are modeling a mountainous region in South Wales, United Kingdom, over a period of forty minutes for your analysis. Your scenario uses a terrain inlay (.pdtt) file and converted image (.pdttx) file for analysis and visualization through the Globe Manager. View the inlaid terrain and imagery in the 3D Graphics window.

  1. Right-click on SWalesHiRes.pdtt () in the Globe Manager hierarchy.
  2. Select Zoom To () in the shortcut menu.
  3. Use your mouse to move around and to zoom in and out to view the terrain in the Mission Area 3D Graphics window.

Viewing the UAV

A UAV is flying over the convoy in a racetrack holding pattern. Its flight route uses the StkExternal propagator, which enables you to import the position and velocity for a vehicle, at whatever time values needed to support analysis and animation, directly from an ephemeris file. The route was initially modeled using the STK software's Aviator capability, which is an advanced propagator that creates a route using a sequence of curves parameterized by readily available performance characteristics of aircraft, including cruise airspeed, climb rate, roll rate, and bank angle.

  1. Right-click on UAV () in the Object Browser.
  2. Select Zoom To in the shortcut menu.
  3. View the UAV in the 3D Graphics window.

The UAV is represented by a 3D model, mq-9b_predator_b.glb. The STK installation contains detailed 3D models of many objects, such as satellites, ground stations, aircraft, air strips, naval vessels, and ground vehicles.

Understanding the UAV's communications system

The STK software's Communications capability was used model the UAV's on-board communications systems. The Communications capability simulates the performance of communications systems in the context of their missions. With the Communications capability, you can model all the physical components of a system, including the RF environment.

Understanding the UAV's antenna servo

The UAV's communications systems consists of an Antenna object, which models the properties and behavior of an antenna, attached to a rotating servo motor. The servo is represented by a Sensor object, which models the field of view and other properties of a sensing device attached to another STK object. The UAV's antenna is targeted via the servo to the convoy's radio equipment, which is located in GroundVehicle2.

  1. Right-click on UAVtoGV2 ().
  2. Select Properties () in the shortcut menu.
  3. Select the Basic - Pointing page when the Properties Browser opens.
  4. Note that the Pointing Type is Targeted, and that GroundVehicle2 () is added to the Assigned Targets list.

    5. The Targeted pointing type causes the sensor to point to other objects in the scenario.

  5. Click Cancel to close the Properties Browser without making any changes.

Understanding the UAV's antenna

The UAV is equipped with a parabolic antenna. Antenna objects are used in conjunction with the Scalable Networks Modeling Interface to model the position, altitude, antenna, gain, and all signal power gains and losses between the input to the transmit antenna and the output to the receive antenna in a wireless communications system. A Parabolic antenna component is an analytical model of a uniformly illuminated parabolic antenna. The antenna names carry over to the Scalable Networks Modeling Interface.

  1. Right-click on UAVtoGV2_Antenna ().
  2. Select Properties ().
  3. Ensure the Basic - Definition page is selected when the Properties Browser opens.
  4. Note the Antenna Model is set to Parabolic.
  5. Note the antenna's specifications:
    6. Option Value
    Design Frequency 14 GHz
    Diameter 30 in
    Efficiency 80 %

Viewing the UAV's receiver

The UAV is equipped with a 14-gigahertz receiver. A Receiver object models the characteristics of a receiver, the antenna it uses, and the environment in which it operates.

  1. Open UAVtoGV2_Rcvr's () Properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Note that Complex Receiver Model is selected for the Receiver model.

    4. A Complex Receiver model enables you to select among a variety of analytical and realistic antenna models and to define the characteristics of the selected antenna type.

  4. Note the Frequency - Auto Track check box is cleared.

    5. The Frequency Auto Track option allows a receiver to track and lock onto the carrier frequency of the transmitter, with which it is currently linking, including any Doppler shift. For the purposes of this analysis, you want this option disabled.

  5. Note the Frequency is set to 14 GHz.
  6. Select the Antenna tab.
  7. Note the Reference Type is set to Sensor/UAVtoGV2/Antenna/UAVtoGV2_Antenna.

    8. The Complex Receiver model allows you to reference an Antenna object you created previously.

  8. Click Cancel to close the Properties Browser without making any changes.

While you can define antenna parameters directly in the Receiver object, Antenna objects are required to define and map network interfaces for experiments run using the Scalable Networks Modeling Interface.

Viewing the UAV antenna pattern

The 3D Graphics Attributes page for an Antenna object controls the 3D display of contour lines and antenna patterns. Take a look at the UAV's antenna volume in the 3D Graphics window.

  1. Return to the 3D Graphics window.
  2. Move around in the 3D Graphics window until you can get a good view of the UAV and its antenna pattern.

    3. Red areas have the most gain, while areas shaded in blue have the least.

  3. Click Start () in the Animation toolbar to animate the scenario.

    4. UAV Parabolic Antenna Pattern Tracking GroundVehicle2

    Note the antenna gain volume for the UAV's receiver as it tracks the reported location of GroundVehicle2.

  4. Click Reset () when you are finished.

Viewing the convoy's route

In addition to aircraft, the STK application also offers propagators for high-fidelity modeling of ground vehicles, launch vehicles, missiles, satellites, and ships.The convoy is modeled using Ground Vehicle objects. A Ground Vehicle object models the properties and behavior of a vehicle that travels on the surface of the Earth. As with the UAV, the routes of the vehicles in the convoy were modeled using the StkExternal propagator. View the convoy's route in the 3D Graphics window.

  1. Right-click on GroundVehicle2 () in the Object Browser.
  2. Select Zoom To in the shortcut menu.
  3. Use your mouse to zoom out until you can see the entire convoy.
  4. Click Start () to view the animation.

    5. Watch as the convoy exits the motorway and heads into the mountains.

  5. Click Reset () when you are finished.

Convoy En Route

Understanding the convoy's communications system

The second vehicle in the convoy is serving as a mobile command and control center. It is connected to the UAV through a targeted 14-gigahertz parabolic antenna and to the other vehicles in the convoy through a 2.4-gigahertz wireless network.

Understanding the convoy's connection to the UAV

View the communications vehicle's UAV antenna system.

  1. Open GV2toUAV's () Properties ().
  2. Select the Basic - Pointing page when the Properties Browser opens.
  3. Note the Pointing Type is Targeted.

    4. Note the ground vehicle's sensor is targeted to the UAV.

  4. Click Cancel to close the Properties Browser without making any changes.
  5. Open GV2toUAVantenna's () Properties ().
  6. Select the Basic - Definition page when the Properties Browser opens.
  7. Note the following design specifications:
    8. Option Value
    Design Frequency 14 GHz
    Diameter 9.75 in
    Efficiency 55 %
  8. Click Cancel to close the Properties Browser without making any changes.

Viewing the transmitter specifications

A Transmitter object models the characteristics of a transmitter, the antenna it uses, and the environment in which it operates.

  1. Open GV2toUAV_Xmtr's () Properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Note the Transmitter model is set to Complex Transmitter Model.

    4. A Complex Transmitter model allows you to select among a variety of analytical and realistic antenna models, and to define the characteristics of the selected antenna type.

  4. Select the Model Specs tab.
  5. Note following model specs:
    6. Option Value
    Frequency 14 GHz
    Power -10 dBW
  6. Select the Antenna tab.
  7. Note the transmitter is linked to Sensor/GV2toUAV/Antenna/GV2toUAVantenna.
  8. Click Cancel to close the Properties Browser without making any changes.

Understanding the convoy's WiFi antennas

The vehicles in the convoy use dipole antennas for their communications. Dipole antennas are modeled analytically in the STK application using modeling equations that can be found in standard antenna texts.

  1. Open WiFi2's () Properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Note that Dipole is selected for the Antenna Model.
  4. Note the following design specifications:
    5. Option Value
    Design Frequency 2.4 GHz
    Length/Wave Length Ratio 1
    Efficiency 100 %
  5. Click Cancel to close the Properties Browser without making any changes.

The convoy's WiFi antennas are named as follows:

Object Antenna Name
GroundVehicle1 WiFi1
GroundVehicle2 WiFi2
GroundVehicle3 WiFi3
GroundVehicle4 WiFi4

Viewing the communication vehicle's antenna patterns

View the communication vehicle's antenna patters in the 3D Graphics window.

  1. Zoom back in to GroundVehicle2 ().
  2. Click Start () in the Animation toolbar to animate the scenario.

    3. Note the antenna gain volumes for GroundVehicle2. The parabolic antenna pattern looks very similar to that on the UAV and rotates to target the UAV. The dipole antenna pattern is static. You will notice that both antenna patterns originate from the roof of the vehicle. In the case of the GV2toUAVantenna, its parent GV2toUAV Sensor object's Location properties were updated to position the sensor with respect to GroundVehicle2's body frame. In the case of the WiFi antenna, the Antenna object's Position Offset properties were updated to raise it off the Ground Vehicle model's center point. To speed up processing, only the antenna graphics for GroundVehicle2 are enabled.

  3. Click Reset () when you are finished.

GroundVehicle2 Antenna Patterns

Analyzing the UAV communications link

The STK application allows you to determine the times one object can "access," or see, another object. You can impose constraints on accesses between objects to define what is a valid access. These constraints are defined as properties of the objects whose accesses are being calculated. This is used with the STK Communications capability to allow you to model and evaluate communications links.

The Scalable Networks Modeling Interfaces leverages access availability between two link antennas based on all active constraints. If the STK application determines that there is no access between the two antennas, the STK application tells Scalable Networks Modeling Interface that communication is not possible.

Computing access

Before you can evaluate the quality of the communications link, you must first compute access between the convoy's transmitter and the UAV's receiver using the Access tool.

  1. Right-click on GV2toUAV_Xmtr () in the Object Browser.
  2. Select Access... () in the shortcut menu.
  3. Expand () UAV () in the associated objects list when the Access tool opens.
  4. Select UAVtoGV2_Rcvr ().
  5. Click .

Creating a dynamic data display

You can dynamically display the receiver gain over the equivalent noise temperature (g/T), the bit energy-to-noise power spectral density ratio (Eb/No), and Bit Error Rate (BER) for the link between GroundVehicle2 and the UAV over time in the 3D Graphics window.

  1. Click 3D Graphics Displays. . ..
  2. Click Add. . . when the 3D Graphics Data Display dialog box opens.
  3. Select Link Budget - BER in the Styles list when the Add a Data Display dialog box opens.

    4. The Link Budget - BER report is calculated based on each asset's current position, attitude, and (defined) transmitter and receiver parameters.

  4. Click OK to confirm your selection and to close the Add a Data Display dialog box.
  5. Click OK to confirm your changes to close the 3D Graphics Data Display dialog box.
  6. Keep the Access tool open.

Viewing the dynamic data display

View the dynamic data display in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Click Start () in the Animation toolbar to view the dynamic display of data.
  3. Click Reset () when you are finished.

Generating a static link budget report

You can also determine the quality of the link between the UAV and the convoy by generating a static Link Budget - Detailed report. A Link Budget - Detailed report provides detailed information for a communications link budget. Each line of the report conforms to a single time step (user specified) of the dynamic link. The link budget information flow in each line of the report follows the signal path. The link starts from a transmitter RF source and goes through the modulator, transmitter antenna, propagation through the RF environment, such as atmosphere, rain, fog, atmospheric scintillation, etc. The signal arrives at the receive antenna, passing through cables, low noise amplifiers (LNA), and is finally demodulated at the receiver. The report provides the link information such as signal powers, RF propagation losses, environmental noise, and link performance at each stage of the signal propagation. The link performance parameters, C/N, Eb/No, and Bit Error Rate (BER), show the signal status without the presence of any interfering signals as well as under the presence of the interfering (jamming) signals.

  1. Bring the Access tool to the front.
  2. Click Report & Graph Manager....
  3. Make sure that GroundVehicle-GroundVehicle2-Transmitter-GV2toUAV_Xmtr-To-Aircraft-UAV-Receiver-UAVtoGV2_Rcvr () is selected in the Object List when the Report & Graph Manager opens.
  4. Select the Link Budget- Detailed () report in the Installed Styles () folder in the Styles list.
  5. Click Generate....

Reviewing the Link Budget- Detailed report

Once the report opens, review the report.

  1. Scroll through the report.

    2. Notice that the BER remains negligible throughout the analysis.

  2. Right-click on the Mission Area 3D Graphics window tab at the bottom of the STK workspace.
  3. Select Close All But This in the shortcut menu.
  4. Save () your scenario.

Opening the Scalable Networks Modeling Interface for STK Communications plugin

The STK application's Communications capability offers an enhanced solution for communications network modeling by introducing off-the-shelf interoperability with the EXata network modeling software, an industry-recognized network modeling and simulation tool, which enables you to evaluate on-the-move communication networks: the Scalable Networks Modeling Interface for STK Communications plugin. The Scalable Networks Modeling Interface combines the EXata software's network performance evaluation capability with the platform mobility models, wireless link calculations and mission visualization environment of the STK application. Its workflow dynamically exchanges data between an EXata scenario's physical layer (PHY) model and an STK antenna object when communications between wireless interfaces is required. This exchange of data enables you to combine the strengths of both analysis tools when evaluating communications links.

The Scalable Networks Modeling Interface can be accessed through the Scalable Networks Modeling Interface toolbar; with the toolbar, you can configure your EXata scenario, run experiments, and display statistical charts.

  1. Select Toolbars in the View menu.
  2. Select Scalable Networks Modeling Interface from the View menu to display the Scalable Networks Modeling Interface toolbar.

Scalable Networks Modeling Interface functions are also available from the Scalable Networks Modeling Interface submenu in the Utilities menu.

The Scalable Networks Modeling Interface features the ability to display and animate event types, such as Receive, Unicast, and Drop, which are published by the EXata simulation. You can animate the events using the buttons on the Scalable Networks Modeling Interface toolbar. Animation events are beyond the scope of this tutorial.

Opening the Scalable Networks Modeling Interface Configuration File Scenario Explorer

The Scalable Networks Modeling Interface Scenario Explorer displays the scenario configuration, hierarchy of STK object nodes, and network connections (wireless subnets, applications and links).

  1. Click Scenario Explorer () on the Scalable Networks Modeling Interface toolbar.
  2. Expand () ScalableNetworksInterface () in the object tree when the Scalable Networks Modeling Interface Scenario Explorer window opens.

Reviewing the scenario's General Settings

Now that the physical objects are fully defined using the STK software, you can map those objects into a EXata simulation. Use the Scalable Networks Modeling Interface Scenario Explorer to define your scenario's configuration.

  1. Expand () the Scenario Configuration () folder.
  2. Expand () General ().
  3. Select General Settings ().
  4. Review the properties panel.

Notice that the Simulation Time of 2400S (equivalent to 40 minutes) is inherited from the STK Scenario Analysis time. Also, notice that the 2400S Simulation Time is bolded. All values that are user-defined or inherited from the STK software are bolded. Take note as well that the default Experiment Name is exata.

Scenario Settings

Enabling the Statistics Database

One of the powerful tools the EXata software provides is for the generation of numerous tables of statistics through its Statistics Database. The Statistics Database collects time-based statistics at a high level of granularity during a network simulation. The statistics captured in the database's tables can be analyzed and used to generate reports to understand network performance issues at a much finer level of detail than you can with just the STK software itself. In this case, you want to use the Statistics Database to collect data on the transmission and reception of individual signals sent over the network's PHY layer.

  1. Expand () Statistics and Tracing ().
  2. Select Statistics Database ().
  3. Open the Enable Statistics Database - Value drop-down list.
  4. Select Yes.

    5. The child properties of Enable Statistics Database should expand out automatically.

  5. Note the Engine Type property is set to SQLite.

    6. The Scalable Networks Modeling Interface supports the creation of SQLite and MariaDB database files.

  6. Expand () the Statistics Database Detail Level - Events Tables property.
  7. Select Yes for the PHY Signal Events Table property.

    8. This will expand the PHY Signal Events Table property to show its child properties.

Statistics Database Properties

Now, when you run your experiment, an SQLite-compatible database file with the selected tables and columns will be generated.

Adding another channel

Your network operates on two channels: a 2.4-gigahertz wireless channel for the convoy is already present, but you need to add a second, 14-gigahertz channel for communications between GroundVehicle2 and the UAV.

  1. Select Channel Properties () in the Scenario Configuration () folder.
  2. Click in the Value field for Number of Channels.
  3. Enter 2 in the Value field for Number of Channels.
  4. Select the Enter key.
  5. Note that the Channel Name [1] property is automatically set to channel1.
  6. Enter 14 GHz in the Channel Frequency [1] - Value field.
  7. Select the Enter key.
  8. Leave the channels names set to their default values.

Channel Properties

Reviewing the scenario hierarchy

A scenario hierarchy is composed of nodes. Nodes communicate with each other through connected network interfaces. Each node must have at least one network interface for it to be considered in the network analysis. Verify that there is one node for each STK parent object in the STK scenario hierarchy.

  1. Expand () Hierarchy () in the object tree.
  2. Select UAV ().
  3. Ensure there is one Node ID listed in the properties panel.
  4. Repeat the process for GroundVehicle1 (), GroundVehicle2 (), GroundVehicle3 (), and GroundVehicle4 ().

    5. Object Nodes

  5. Confirm your Node IDs match the following table:
Node Node ID
UAV 1
GroundVehicle1 2
GroundVehicle2 3
GroundVehicle3 4
GroundVehicle4 5

Defining network interfaces

A network interface is a connection instance between a transmit antenna and a receive antenna. You can define one or more network interfaces for each node in the hierarchy folder. A node requires at least one interface for each network connection instance.

Renaming an existing interface

By default, objects that already have antennas attached to them in your STK scenario automatically have a wired and a wireless interface created for them. The wireless interfaces are already configured to use the attached Antenna objects. These interfaces are listed in a nested Interfaces folder for each node in the Scenario Hierarchy. For clarity of organization, begin by renaming the existing wireless interface for the UAV node.

  1. Expand () UAV () in the object tree.
  2. Expand () the Interfaces () folder.
  3. Note that UAV () has two network interfaces (): interface0 () and interface1 ().

    4. interface0 () is the default wired interface; interface1 () is the default wireless interface.

  4. Right-click on interface1 ().
  5. Select Edit in the shortcut menu.
  6. Enter UAVtoGV2 in the Interface Name field when the Edit Wireless Interface dialog box opens.
  7. Note that UAVtoGV2/UAVtoGV2_Antenna is automatically selected for the Transmit Antenna - Instance Name.
  8. Also note that the Use Transmit Antenna for Receive check box is automatically selected in the Receive Antenna panel.

    9. Edit Wireless Interface

  9. Click OK to confirm your changes and to close the Edit Wireless Interface dialog box.

You can control whether wired and wireless interfaces are created by default when an object is added to your scenario by updating the Scalable Networks Modeling Interface Settings.

Renaming the remaining wireless interfaces

Repeat the process for each ground vehicle's default wireless interface.

  1. Expand () each of the four GroundVehicle () nodes.
  2. Expand () the Interfaces () spellfolder nested under each of the ground vehicle () nodes.
  3. Note that GroundVehicle2 () has three default interfaces (): one wired connection and one wireless connection for each attached antenna.
  4. Repeat the steps in the previous section to rename each ground vehicle node's default wireless interfaces (), as specified below:
    5. Node Default Interface Name New Interface Name Instance Name
    GroundVehicle1 interface1 GV1_WiFi WiFi1
    GroundVehicle2 interface1 GV2_WiFi WiFi2
    interface2 GV2toUAV GV2toUAV/GV2toUAV_Antenna
    GroundVehicle3 interface1 GV3_WiFi WiFi3
    GroundVehicle4 interface1 GV4_WiFi WiFi4

Interface Hierarchy

If you expand () the wireless interfaces (), you will note that they have properties for the Physical Layer, MAC Layer, and other network layers. For this tutorial, you don't need to define them at the interface level, since you will be defining them at the subnet level and those definitions will take precedence.

Creating network connections

Now that you have defined the interfaces between STK antennas, you can define your connections. The Scalable Networks Modeling Interface enables you to create and define network connections for wired subnets, wireless subnets, applications, and links.

Creating the wireless subnet between the ground vehicle and the UAV

A wireless subnet contains nodes and/or interfaces. Once a node and/or interface is a member of a subnet, it is unavailable to other subnets. The Physical Layer of the wireless subnet includes radio type, transmitter powers, receiver sensitivities, and noise properties.

  1. Right-click on Connections () in the object tree.
  2. Select Add Wireless Subnet ... in the shortcut menu.
  3. Enter GV2toUAV in the Name field when the Add Wireless Subnet dialog box opens.
  4. Move (>) UAV/UAVtoGV2 from the Available Interfaces list to the Selected Interfaces list.
  5. Move (>) GroundVehicle2/GV2toUAV to the Selected Interfaces list.
  6. Select the Assign IP address to interfaces to match network IP check box.

    7. If you do not select the Assign IP address to interfaces to match network IP check box, the Scalable Networks Modeling Interface will not run.

  7. Keep the default values for all other parameters.

    8. Add Wireless Subnet

  8. Click OK to confirm your changes and to close the Add Wireless Subnet dialog box.

Setting up the GV2toUAV wireless subnet's channel properties

Set up the GV2toUAV wireless subnet so that it can only transmit and receive on the 14-gigahertz channel. The GV2toUAV wireless subnet is located in the Connections - Wireless Subnets folder in the object tree.

  1. Expand () Connections () in the object tree.
  2. Expand () the Wireless Subnets () folder.
  3. Expand () GV2toUAV ().
  4. Select Physical Layer ().
  5. Click on the Listenable Channel Mask - Value field.
  6. Clear the Enabled? check box for the channel 0 - 2.4 GHz Frequency option when the Channel Mask Editor dialog box opens.
  7. Select the Enabled? check box for the channel 0 - 14 GHz Frequency option.

    8. Channel Mask Editor

  8. Click OK to confirm your change and to close the Channel Mask Editor dialog box.

    9. Note that the Listenable Channel Mask - Value has been set to channel1; channel1 is the default name of your 14 GHz channel.

  9. Set the Listening Channel Mask to use channel1 by selecting only 14 GHz in the Channel Mask Editor.

Configuring the subnet's PHY layer

Select a Radio Type that is appropriate for the large range of the link between the Ground Vehicle and the UAV. Use an Abstract radio type and update its properties. The Scalable Networks Modeling Interface interacts with the PHY layer's transmit power, frequency, and data rate to compute the received signal-to-noise ratio and BER based on the received power computed by the STK application.

  1. Open the Radio Type drop-down list in the properties panel.
  2. Select Abstract.
  3. Expand () the Tx and Rx Use Same Frequency property.
  4. Set the Tx and Rx Center Frequency - Value to 14 GHz.
  5. Set the Rx Bandwidth - Value to 32 MHz.
  6. Expand () the Number of Modulation and Coding Schemes property.
  7. Set the Data Rate [0] - Value to 16 Mbps.
  8. Set the Frequency Bandwidth [0] - Value to 32 MHz.

Setting the Reception Sensitivity and Threshold

For the purposes of your network test, you want to examine the receiver sensitivity and threshold values.

  1. Set the Reception Sensitivity (dBm) [0] - Value to -40.
  2. Set the Reception Threshold (dBm) [0] - Value to -50.

When working with EXata, the reception threshold should be set lower than the sensitivity.

Your Physical Layer properties should match the following table:

Property Value
Listenable Channel Mask channel1
Listening Channel Mask channel1
Radio Type Abstract
Tx and Rx Center Frequency 14 GHz
Rx Bandwidth 32 MHz
Data Rate [0] 16 Mbps
Frequency Bandwidth [0] 32 MHz
Reception Sensitivity (dBm) [0] -40
Reception Threshold (dBm) [0] -50

Wireless Subnet Physical Layer configuration

Setting up the MAC layer

Use a generic MAC protocol for the wireless interface.

  1. Select MAC Layer () in the object tree.
  2. Open the MAC Protocol - Value drop-down list.
  3. Select Generic MAC.

Setting up the Network layer

Configure the network's buffer to use a single IP output queue.

  1. Expand () Network Layer () in the object tree.
  2. Select Schedulers and Queues ().
  3. Set the Number of IP Output Queues - Value to 1.
  4. Leave all other values their defaults.

Setting up the Routing Protocol

Use the Ad hoc On-Demand Distance Vector Routing (AODV) network protocol, which is efficient for dynamic, rapidly changing topologies.

  1. Select Routing Protocol () in the object tree.
  2. Select AODV in the Routing Protocol IPv4 - Value drop-down list.
  3. Leave all other values their defaults.

Creating and configuring the convoy's wireless subnet

Now, add and configure a wireless subnet for the convoy.

  1. Right-click on Connections () in the object tree.
  2. Select Add Wireless Subnet ... in the shortcut menu.
  3. Set the following properties when the Add Wireless Subnet dialog box opens:
    4. Name Selected Interfaces
    Convoy GroundVehicle1/GV1_WiFi
    GroundVehicle2/GV2_WiFi
    GroundVehicle3/GV3_WiFi
    GroundVehicle4/GV4_WiFi

    Keep the default values for all other parameters.

  4. Select the Assign IP address to interfaces to match network IP check box.

    5. Remember that, as when you set up the previous wireless interface, if you do not select the Assign IP address to interfaces to match network IP check box, the Scalable Networks Modeling Interface will not run.

  5. Click OK to confirm your changes and to close the Add Wireless Subnet dialog box.
  6. Configure the Convoy's wireless subnet Physical Layer () as follows:
    7. Property Value
    Listenable Channel Mask channel0
    Listening Channel Mask channel0
    Radio Type 802.11b Radio
    Transmission Power at 1 Mbps (dBm) 45
    Transmission Power at 2 Mbps (dBm) 45
    Transmission Power at 5.5 Mbps (dBm) 45
    Transmission Power at 11 Mbps (dBm) 45
  7. Set the Network Layer's () Schedulers and Queues () Number of IP Output Queues to 1.
  8. Set the Routing Protocol () Routing Protocol IPv4 to AODV.

Creating a CBR application link

An application link includes a source, a destination and an application type. Each application sends a start time, stop time, precedence, item size and number of items. Create an application to send data from GroundVehicle4 to the UAV.

  1. Right-click on Connections () in the object tree.
  2. Select Add Application ... in the shortcut menu.
  3. Open the Source drop-down menu when the Add Application dialog box opens.
  4. Select GroundVehicle4.
  5. Open the Destination drop-down list.
  6. Select UAV.
  7. Set the Application type to CBR.

    8. This option sends data from a client to a server at a constant bit rate (CBR).

  8. Click OK to confirm your changes and to close the Add Application dialog box.

Setting up the CBR application

Configure the items for the CBR application to send and its Start and End times.

  1. Expand () the Applications () folder, located under Connections (), in the object tree.
  2. Select CBR: GroundVehicle4 --> UAV ().
  3. Set the following properties for the CBR application:
    4. Parameter Value
    Items to Send 360
    Start Time 790 seconds
    End Time 1150 seconds

The Start Time and End Time settings enable you to focus on just a small portion of the route. The Items to Send value of 360, in combination with the 360-second time period between Start Time and End Time, force the application to send one packet per second.

Running a Scalable Networks Modeling Interface experiment

Apply all network settings and compute network-level statistics on your STK scenario by running an experiment, then view the results.

Running your experiment

You can run the experiment through the Scalable Networks Modeling Interface Scenario Explorer toolbar.

  1. Ensure Simulation is selected in the drop-down list on the Scenario Explorer toolbar.

    2. You can choose whether you are performing a network simulation or network emulation.

  2. Click Run Experiment () on the Scenario Explorer toolbar.
  3. Take note of the Initializing status displayed on the bottom left of the Simulator Run Control window when it opens.

    4. Initialization can take anywhere from several seconds to several minutes, depending on the complexity of your scenario and experiment.

  4. When the status has changed to Ready to Run, click Start.

    5. The elapsed Simulation Time is displayed, and the status of the run is displayed in the Progress bar.

  5. When the simulation is completed the Stat File viewer will automatically open.

Each time you run a Scalable Networks Modeling Interface experiment, the STK application populates a working directory with files used by Scalable Networks Modeling Interface. The STK application also places the Stat file into this folder.

The folder structure is:

<user-selected folder or STK scenario folder>\Scalable Networks Modeling Interface Experiments\<Scalable Networks Modeling Interface experiment name>\<date in format YYYY_MM_DD>\<time in format HH_MM_SS>

An example is:

C:\Users\<username>\Documents\STK_ODTK 13\ScalableTutorial\Scalable Networks Modeling Interface Experiments\exata\2026_03_05\09_32_33.

In addition to the Stat file, the following Scalable Networks Modeling Interface Experiment files will be saved to that working directory, which is specified in the Scalable Networks Modeling Interface preferences:

  • Application configuration file (*.app), which specifies the applications running on the nodes in the scenario and is referenced by the scenario configuration file.
  • Scenario configuration file (*.config), which is the primary input file for the Scalable Networks Modeling Interface application and specifies the network scenario and parameters for the simulation. This file allows you to map the interfaces to their respective antennas and can be used directly in the EXata software itself.
  • Qimap file (*.qimap), which contains the mapping between STK objects and the Scalable Networks Modeling Interface nodes and is required by both the STK and the EXata applications.
  • STK VDF file (*.vdf), which enables you to view the exact settings used by STK software when generating the Scalable Networks Modeling Interface stat file. This is a handy reference if you plan to later change the STK scenario. Be aware that each copy of an STK scenario can potentially use a large amount of disk space.

The folder may also contain:

  • Generic database file (*.db), built using SQLite, if you specified one to be generated in the Statistics Database properties earlier
  • log file (*.log), containing link and node information
  • JSON file (*.json), containing structured data about your scenario

You can see a visual representation of this workflow here.

Viewing the Command-line Output Log

Before taking a close look at the Stat File viewer, it is helpful to review the Command-line Output Log, which lists all messages generated by the Scalable Networks Modeling Interface Experiment run. If you ever need to debug your scenario or determine why your experiment hasn't initialized or run successfully, the Command-line Output Log will show you that information.

  1. Return to the Scalable Networks Modeling Interface Scenario Explorer window.
  2. Click Simulator Command-line Output Log () on the Scenario Explorer toolbar.
  3. Correct any errors () listed in the log to run your experiment successfully, if necessary.
  4. Re-run () the Scalable Networks Modeling Interface experiment, if necessary.

Analyzing your experiment

With your experiment completed, review the results to understand any network issues that may exist with your network configuration or scenario.

Reviewing the Stat file

Statistics (or Stat) files are the primary output file generated by a Scalable Networks Modeling Interface simulation run and have a *.stat file extension. When a simulation run is completed, a Stat file is automatically loaded into the Stat File viewer.

You can also import a EXata Stat file for review in the STK application by clicking Import Results () on the Scenario Explorer toolbar.

  1. Take note of the categories listed in the object tree.

    2. These include Throughput, Broadcasts Sent and Received, Packets Queued, Packets dropped, Route Timeouts, and Packet Times. Graphs are shown by node ID (interface ID). The Statistics file is the primary output file generated by a Scalable Networks Modeling Interface simulation run. The statistical categories are listed in the object tree, including Throughput, Broadcasts Sent and Received, Packets Queued, Packets dropped, Route Timeouts, and Packet Times. Graphs are shown by node ID (interface ID).

  2. Select the Physical - Abstract - Signals Transmitted (signals) category.

    3. You can click on any parameter in the Stat File viewer to display its statistics from the simulation run.

  3. Note the results on the Physical - Abstract bar chart.
  4. Hover over the results to show the Node, the Interface, and the number of packets sent.

    5. As expected, GroundVehicle2 is sending out a lot of signals, as it is the main communications hub. However, you configured your experiment to send 360 packets of information, and only 219 packets were received by the UAV.

  5. Select the Network - AODV for IPv4 - Number of Data Packets Dropped for no route category.
  6. Review the Network - AODV for IPv4 chart.

All data packets dropped

If you want to export an image of a chart for sharing outside of the STK application, you can right-click on the chart and select Save Image As... in the shortcut menu.

Recall the goal of your experiment was to use a CBR application to send data from GroundVehicle4 to the UAV. However, all 360 packets of information for Node ID 5 (which corresponds to GroundVehicle4) were dropped for no route. Another clue that your network isn't performing as expected is under the Application category; you can see categories for the CBR Client, but no categories for CBR Server, which means you are not getting any server-side results.

Since your BER was negligible throughout the scenario, there must be some other cause for the lost data. You will need to investigate your results in greater detail to understand why the signals aren't being sent.

Reviewing the Statistics Database

The Stat file can only tell you so much. To help identify the root cause of the network performance issues, examine the SQLite database file you configured to be produced in the Scenario's Statistics Database properties.

Opening the database file

Explore the database file with the database inspection tool of your choice. Examples include DB for SQLite or the MATLAB platform's Database Explorer app.

  1. Open Windows File Explorer.
  2. Navigate to your scenario folder (for example, C:\Users\<username>\Documents\STK_ODTK 13\ScalableTutorial).
  3. Open the exata sub-folder.
  4. Open the folder with today's date.
  5. Open the folder with the most recent time.
  6. Open the database (*.db) file with the database inspection tool of your choice.

Reviewing the physical events data

Recall that you configured your experiment to capture details about events with the physical layer. Review the PHY_Events table to learn more about the specifics of your network's performance.

  1. If you are using the DB for SQLite software, select the Browse Data tab.

    2. Other applications may have different interface options.

  2. Open the PHY_Events table.
  3. Browse through the data in the table.

    4. You can see through the various columns the various properties of the messages that have been sent.

  4. Review the data in FailureType column.

    5. As you scroll through the data in the column, you can see there are many instances where the FailureType is Signal below Rx Sensitivity. This is a clue why your packets are being dropped.

  5. Sort the data in the SignalPower column from the smallest value to the largest value.
  6. Review the data in the SignalPower column.

    7. Sorted db file showing weakest signal

    You can see that the weakest signal was around -57 decibel-milliwatts, and for signals of that magnitude, you encountered a PhyDrop EventType, with a FailureType of Signal below Rx Sensitivity. From these data, you can see that you need a more sensitive receiver in order to receive signals at least as weak as -57 decibel-milliwatts.

  7. Leave your database inspection tool and Windows File Explorer open.

Updating your scenario and re-running your experiment

Recall that you had previously set reception sensitivity and threshold values of -40 decibel-milliwatts and -50 decibel-milliwatts, respectively. Increase these values to allow the signals to be received, the re-run your experiment.

Updating the GV2toUAV wireless subnet's settings

Increase the reception sensitivity and threshold values for your experiment.

  1. Return to the STK application.
  2. Go to the Scalable Networks Modeling Interface Scenario Explorer window.
  3. Select Connections - Wireless Subnets - GV2toUAV - Physical Layer () in the object tree.
  4. Expand () the Number of Modulation and Coding Schemes property.
  5. Set the Reception Sensitivity (dBm) [0] - Value to -60.
  6. Set the Reception Threshold (dBm) [0] - Value to -70.

    7. Updated sensitivity and threshold values

  7. Save () your scenario.

Re-running your experiment and reviewing the results

Now that you've set your values, run your experiment again and review the data

  1. Click Run Experiment () on the Scenario Explorer toolbar.

    2. The progress bar may show 100% before the experiment fully initializes; this is left over from your previous run, it will clear once your experiment is ready to run.

  2. When the status has changed to Ready to Run, click Start.
  3. Review the data when the Stat File viewer open.

    4. You can see that unlike in your previous experiment, there is no longer category for Network - AODV for IPv4 - Number of Data Packets Dropped for no route category.

  4. Select the Network - AODV for IPv4 - Number of Data Packets Received category.
  5. Review the Network - AODV for IPv4 chart.

    6. All packets received

    Note that Node ID 1 (UAV) has now received all 360 data packets.

  6. Note also that you now have server-side results you can explore through the Application - CBR Server properties.

CBR Server categories present

Confirming the changes in the database file

The statistics look good, but you can also review the database file created from your latest run to confirm.

  1. Return to Windows File Explorer.
  2. Navigate up to the date sub-folder.

    3. Your updated database file is in a new experiment folder.

  3. Open your most recent experiment folder.
  4. Open the database (*.db) file with the database inspection tool of your choice.
  5. If you are using the DB for SQLite software, select the Browse Data tab.
  6. Open the PHY_Events table.
  7. Sort the data in the SignalPower column from the smallest value to the largest value.
  8. Review the data in the SignalPower column.

    9. Now, the FailureType column for the lowest signal powers have a null value, and instead of a PhyDrop event type, the lowest SignalPower values are associated with reception and transmission events. The data confirm you've successfully adjusted your reception sensitivity and threshold to receive all the signals.

  9. Close your database inspection tool.

Exporting your experiment

Once you are happy with your results, export your experiment.

  1. Click the down arrow next to Run Experiment ().
  2. Select Export Experiment in the drop-down menu.
  3. Read the warning when the Experiment Export dialog box opens.
  4. Click OK to close the Experiment Export dialog box and to open the containing folder.
  5. Close Windows File Explorer.

Importing an EXata scenario using a Scalable Networks Modeling Interface Configuration File

An alternative method to configuring your experiment in the STK application is to import the wireless interfaces from an EXata scenario directly into the STK application through the Scalable Networks Modeling Interface. The Scalable Networks Modeling Interface Configuration File Importer enables you to map wireless interfaces from an EXata scenario to antenna objects in the STK scenario.

A sample configuration file generated by the EXata software is included in your scenario and can be found in your scenario folder. Though a *.config file is also generated by the Scalable Networks Modeling Interface when you run an experiment, only those created by EXata proper can be ingested by the Configuration File Importer.

You can configure a scenario built in the EXata software for use with the STK application. Once you have everything configured the way you like, you must save it to produce a *.config file.

  1. In the EXata application, select the File menu.
  2. Select Save As Portable....

Save As Portable option in the EXata software

This option will create a *.config file, which you can then import into your STK application using the Scalable Networks Modeling Interface Configuration File Importer.

Importing a configuration file using the Scalable Networks Modeling Interface Configuration File Importer

Open the Scalable Networks Modeling Interface Configuration File Importer to bring in the configuration file included with your scenario.

  1. Click Configuration File Importer () on the Scalable Networks Modeling Interface toolbar.
  2. Click Add Configuration File () on the Configuration File Importer toolbar when the Scalable Networks Modeling Interface Config Importer window opens.
  3. Navigate to your scenario folder when the Open dialog box opens.
  4. Select ScalableNetworks_Tutorial.config.
  5. Click Open to confirm your selection and to close the Open dialog box.
  6. Note that ScalableNetworks_Tutorial.config is now listed in the Simulator Configuration File panel.
  7. Also note that ScalableNetworks_Tutorial.config has a warning () status and the Run Experiment button is grayed out.

You still need to map all your interfaces to your STK antenna objects before you can run an experiment.

Mapping the wireless interfaces to the STK antennas

View all the available interfaces and map them to their respective STK Antenna objects.

  1. Right-click on UAV (1) () in the Available Wireless Interfaces tree.

    2. The numbers in the parentheses are the Node IDs.

  2. Select Unmapped Interfaces in the shortcut menu.
  3. Select Expand in the Unmapped Interfaces submenu.
  4. Right-click on UAV () in the Available Antenna Objects tree.
  5. Select Expand All.

    6. Config Importer

  6. Click and Drag 190.0.0.1 () onto UAVtoGV2_Antenna ().

    7. Note that a green check box appears over 190.0.0.1 () and the mapping has been added to the table in the Mapped Interfaces panel.

  7. Using the same procedure as 190.0.0.1, make the following mappings:
Wireless Interface Antenna Object
190.0.0.2 GV2toUAV_Antenna
190.0.1.1 WiFi1
190.0.1.2 WFi2
190.0.1.3 WiFi3
190.0.1.4 WiFi4

If you have trouble identifying the wireless interfaces by their IP addresses, you can review the addresses and their node assignments in the EXata application's Table View.

EXata Table View

Once all of your mappings are completed, the status for the simulator configuration file will be updated with a green check mark () to indicate that the configuration file is up-to-date and all interfaces are mapped to STK antenna objects. The Run Experiment () button will also become active and you can then proceed to run your simulation as before.

Config Importer: All interfaces mapped

Saving your work

Clean up your workspace and close out your scenario.

  1. Close the Stat File Viewer, the Scalable Networks Modeling Interface Scenario Explorer, and all reports and windows except the 3D Graphics window.
  2. Save () your work.
  3. Close your scenario when you are finished.

Summary

You opened a preconfigured VDF file, and saved it as a Scenario file. The scenario used STK software's Communications capability to model a communications network between a convoy of ground vehicles traversing mountainous terrain and a UAV flying overhead. External ephemeris files were used to model the vehicles' routes and an attitude file was used to model the UAV's flight dynamics. You calculated access between the convoy and the UAV, then evaluated the quality of the link using a preinstalled report in the Report & Graph Manager. You then used Scalable Networks Modeling Interface to leverage your STK scenario with the EXata software's physical layer modeling capabilities to configure wireless network communications interfaces. You then performed an experiment on your network and analyzed the results. You examined the experiment's results and used them to improve your network performance. Finally, you imported a configuration file and used the Scalable Networks Modeling Interface Configuration File Importer to create mappings between an EXata scenario and STK antenna objects. By using the Scalable Networks Modeling Interface, you were able to combine the strengths of both the STK software and EXata network modeling software to evaluate your communications links.