Part 14: Evaluate Communication Links

This training requires additional licenses to complete. You can obtain the necessary license for the training by visiting http://licensing.agi.com/stk/evaluation or calling AGI support.

STK Communications

The Communications module allows you to define and analyze detailed communications systems. You can incorporate detailed rain models, atmospheric losses, and RF interference sources in your analyses and generate detailed link budget reports and graphs. Communications modeling in STK includes:

There are two case studies that showcase the use of AGI's Communications module: NASA Space Communication Network Architecture Analysis andStudying Mobile Ad-Hoc Network Communications Architectures.

  • Modeling communications links under dynamic conditions.
  • Performing communications link budget analysis.
  • Presenting parameters, analysis, link behavior, and antenna patterns graphically in 2D, and when possible, 3D.
  • Dynamically animating link parameter behavior.
  • Determining an object's geometric or refractive/radio line-of-sight visibility.
  • Performing system- level engineering.

These capabilities can be expanded upon by integrating Communications with commercially available network modeling and simulation applications. Such integrations allow for communications analysis down to the protocol layer to be fused into an entire mission construct modeled in STK. You can model and assess network-protocol-level aspects such as:

  • Buffering
  • Routing
  • Rate control
  • Quality-of-service frameworks

Model Communication Equipment and Calculate Link Budget

Watch the following video, then follow the steps below incorporating the systems and missions you work on (sample inputs provided).

  1. Create a new scenario with the default time period.Closed
    1. Click the Create a new scenario () button.
    2. In the New Scenario Wizard, set the following options:
      • Enter a name for the scenario (e.g. STK_Comm).
      • Define the analysis start and stop times or accept the defaults.
    3. Click OK.
  2. Incorporate terrain as a constraint.Closed
    1. Select the Basic - Terrain page.
    2. Enable the Azimuth/Elevation Mask in the Advanced Analysis Operation field.
    3. Enable the Line-of-Sight, Terrain Mask, Azimuth-Elevation Mask, and Coverage options.
    4. Click OK.
  3. Model a ground site (any type, , , ) that will model ground control station.Closed
    1. Insert a Place () by typing in the location (e.g. Latitude = 46.28 deg; Longitude = -122.22 deg).
    2. Insert a Place () using the Search by Address method (requires Internet ()) (e.g. Johnston Ridge, WA).
    3. If using a Place, open its Properties and select the 3D Graphics - Model page.
    4. In the Detail Thresholds field, move the slider for All to the right.
    5. Select the Basic - AzElMask page.
    6. Set the following options:
      • Use: Terrain Data
      • Enable Use Mask for Access Constraint
    7. Click OK.
  4. Model a satellite () that has visibility to the ground site.Closed
    1. Insert a satellite using the Orbit Wizard method.
    2. Ensure the orbit has at least one pass over the ground site.

  5. Compute Access between the moving vehicle and ground site to assure access.Closed

    1. Open the Access () tool.
    2. Click the Select Object... button and select the moving vehicle as the Access For object ("From").
    3. Select the ground site as the "To" object.
    4. Click the Compute button.
    5. Click Access... in the Reports area to generate an Access report.
    6. If there is no access, modify the moving vehicle's orbit, route, or trajectory.
  6. Model a simple transmitter () on the satellite ().Closed
    1. Insert a Transmitter () on the satellite ().Closed
      1. Select Transmitter () in the Insert STK Objects () tool.
      2. Select Define Properties as the Select A Method option.
      3. Click Insert... to bring the Select Object window to the front.
      4. Select the satellite in the Select Object window.
      5. Click OK. You will notice that the default transmitter is a simple transmitter.
    2. Change the transmitter's frequency (2 GHz) and EIRP (20 dBW).Closed
      1. On the Basic - Definition page, select the Model Specs tab.
      2. Enter the desired two (2) GHz Frequency value in the textbox.
      3. Enter the desired 20 dBW EIRP value in the textbox.
      4. Click OK to apply the changes and dismiss the Properties Browser.
  7. Model a two (2) degree Simple Conic Sensor () on the ground site targeted towards the satellite which acts as a pointing device for the ground antenna.Closed
    1. Insert a sensor () on the ground site.Closed
      1. Select Sensor () in the Insert STK Objects () tool.
      2. Select Define Properties as the Select A Method option.
      3. Click Insert... to bring the Select Object window to the front.
      4. Select the ground site in the Select Object window.
      5. Click OK.
    2. Change the sensor's field-of-view to a two (2) degree Cone Half Angle.Closed
      1. Select the Basic - Definition page.
      2. Enter the desired two (2) deg Cone Half Angle value in the text field.
    3. Change the sensor's pointing to target the moving vehicle.Closed
      1. Select the Basic - Pointing page.
      2. Change the Pointing Type to Targeted in the drop-down list.
      3. Move () the satellite to the Available Targets list. You can also double-click the satellite to move it to the Available Targets list.
    4. Add an Azimuth and Elevation constraint to the sensor.Closed
      1. Select the Constraints - Basic page.
      2. Enable the AzEl Mask option.

    Sensors are used to point transmitters and receivers. The easiest way to ensure that the transmitter and receiver communicate with one another (in a geometric sense) is by attaching them to sensors that point toward the objects they want to communicate with.

  8. Model a complex receiver () with a parabolic antenna on the ground site's sensor and display the volume graphics.Closed
    1. Insert a receiver () on the ground site's sensor.Closed
      1. Select Receiver () in the STK Insert Objects () tool.
      2. Select Define Properties as the Select A Method option.
      3. Click Insert to bring the Select Object window to the front.
      4. Select the sensor on the ground site in the Select Object window.
      5. Click OK.
    2. Change the receiver Type to Complex Receiver Model.Closed
      1. Select the Basic - Definition page.
      2. Click on the ellipsis () button beside the Type option.
      3. Select the Complex Receiver Model and click OK.
      4. Click Apply to accept the changes and keep the Properties Browser open.
    3. Change the Antenna type to Parabolic with a 1.6 m diameter.Closed
      1. On the Basic - Definition page, select the Antenna tab.
      2. Click on the ellipsis () button beside the Type option.
      3. Select the Parabolic and click OK.
      4. Enter the desired 1.6m Diameter in the textbox.
      5. Click Apply to accept the changes and keep the Properties Browser open.
    4. Display the Volume GraphicsClosed
      1. Select the 3D Graphics - Attributes page.
      2. Enable the Show Volume option.
      3. Enter the desired 0.1 km Gain Scale (per dB) in the text field.
      4. Enable the Set azimuth and elevation resolution together option.
      5. Enter the desired one (1) deg resolution in the text field.

  9. Compute Access () from the transmitter () to the receiver ().Closed

    1. Open the Access () tool.
    2. Click the Select Object... button and select the transmitter on the moving vehicle as the Access For object ("From").
    3. Select the receiver on the ground site's sensor as the "To" object.
    4. Click Access... in the Reports area to generate an Access report.
    5. Right-click on the first Start Time.
    6. Extend the Start Time menu and select Set Animation Time.
    7. Bring the 3D Graphics window to the front.
    8. Click Step Forward () in the Animation Toolbar a few times to allow the volume graphics of the antenna pattern to exit terrain.
  10. Generate a Link Budget report () between the transmitter () and the receiver ().Closed
    1. Ensure the transmitter on the moving vehicle is selected as the Access For object and the receiver on the ground site's sensor is set as the "To" object.
    2. Click the Link Budget... button in the Reports area to generate a Link Budget report.
    3. Enter a smaller step size (e.g. 1 sec) in the Step text field. This updates the report step size.
    4. Locate the Bit Error Rate (BER) and determine the quality of the communications link. (e.g. 1.000000e-10 or lower)
  11. Create a new custom graph for your transmitter to receiver access that displays the carrier to noise ratio (C/N).Closed
    1. Click the Report & Graph Manager... button in the Access tool.
    2. In the Object Type drop-down list, select Access..
    3. Select the transmitter to receiver Access object that will be the focus of the graph.
    4. Select the Scenario Styles directory and click the Create new graph style () button.
    5. Rename the graph CN and click Enter on the keyboard to bring up the Graph Style properties.
    6. Replace the asterisk (*) with C/N and click Filter.
    7. Expand () the Link Information data provider.
    8. Select the C/N data provider.
    9. Move () the C/N data provider to the Y Axis.
    10. Click OK to save the custom graph style.
    11. Select the new graph style and click Generate....
    12. Enter a smaller step size (e.g. 1 sec) in the Step text field. This updates the graph step size.

Now that you have done communications from one moving vehicle (satellite), try it with other moving vehicles like aircraft or ground vehicles.

Don't forget to save your work!

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