Creating a Scenario

This procedure guides you through the settings to create a scenario using the Scenario Generator tab on the software user interface (UI):

To view information for each setting, click on the cell and the information appears at the bottom of the window. In the above figure, the window displays the information for the highlighted Elevation Resolution cell.

1. If the software is not open, start the software by double clicking the desktop icon or access the software through the PC start menu.

   The software starts with Create as the default Generation Mode.

2. If working with assisted GPS (A-GPS), select On for the Output A-GPS and Ephemeris Files cell.

   With the cell set to On, the software creates and outputs two additional files in a csv format: one file contains the A-GPS data and the other contains the ephemeris data. The software uses data from the selected almanac file to generate the two files.

3. If there is a need to use an ephemeris file, click the Ephemeris File (Optional) cell, and use the dialog box button to launch the Open dialog box for navigating to and selecting the ephemeris file.

   If no file is selected, the software uses data from the selected almanac file to create its own internal ephemeris file data. Ephemeris files are typically required to create specific scenarios required for some 3GPP conformance tests.

   If you use an ephemeris file created with the Output A-GPS and Ephemeris Files cell, ensure that you use the modified version.

4. Click the Almanac File cell, and use the dialog box button to launch the Open dialog box for navigating to and selecting the almanac file.

   The software only accepts this file in the Yuma format. You can obtain this required GPS almanac file from the URL: http://www.navcen.uscg.gov/?pageName=gpsAlmanacs and save it to your PC.

5. Set the Elevation Mask Angle.

   The software sets the mask from the horizon to the angle entered. This means that the software only recognizes satellites that appear above the mask value.

6. If desired, set the Troposphere Model to NATO or leave as No Model.

   Some tests, such as in the 3GPP standards, require the NATO model selection.

7. If performing conformance tests for W-CDMA or cdma2000, select the respective Ionosphere Model:Klobuchar for WCDMA or Klobuchar for cdma2000. Otherwise leave the No Model selection.

8. Select the Scenario Type to either Static or Dynamic (moving GPS receiver).

   If you select Dynamic, the software removes some settings (cells) that are requirements only for the Static selection.

9. Finish configuring the settings for either the Static or Dynamic scenario type selection.

   Static Type Settings:

   1. Set the Initial Longitude.

   2. Set the Initial Latitude.

   3. Set the Initial Altitude.

   4. Set the Start Date Time (GPS Time) cell with the start date and time of the scenario simulation.

      The start date and GPS time is automatically updated to the TOA (Time of Applicability) from the almanac file. Manually override the file setting by either entering a date and time, or using the drop-down arrow that appears when the property is clicked to select a different date and time.

   5. Set the Duration (HH:mm:ss) with the length of time that the scenario plays back. 24 hours is the maximum time period.

   6. Set Channel Packing to either Auto or Manual.

      The software supports a maximum of eight visible satellites. When set to Auto, the software automatically selects the optimal satellites for the scenario. When set to Manual and more than eight satellites exist for a time period, the software, upon clicking the Create Scenario button, displays a message on the conflict. After you acknowledge the message, it then creates and displays a Satellite Visibility view where you manually select the undesired satellites to resolve conflicts that occur in a time period with more than eight satellites.

   7. If desired, set Antenna Pattern to On to configure a gain mask.

      When set to On, the software UI displays three additional cells:

      

   8. If the Antenna Pattern is On,

      1. If desired, change the values for the  Elevation Resolution, Azimuth Resolution, and Azimuth Rotation cells by clicking the cell and entering a value.

         The values in these cells affect the Antenna Pattern display shown on the Antenna Pattern tab.

         

      2. Select the Antenna Pattern tab.

      3. Configure the Antenna Pattern gain mask.

      4. Select the Scenario Generator tab.

   Dynamic Type Settings:

   1. Click the NMEA Message File cell, and use the dialog box button to launch the Open File dialog box for navigating to and selecting the NMEA message file.

      The software accepts NMEA message files that contain both the GGA and RMC messages. The GGA message is mandatory, but the RMC is optional.

   2. If the NMEA message file does not contain the date and time, set the Start Date Time (GPS Time) cell with the start date and time of the scenario simulation.

      When the NMEA message file contains the RMC message with the date and time, the software uses the message's date and time, and ignores this cell's entry. If there are multiple RMC messages, the software uses the date and time from the first RMC message it encounters as the scenario start date and time.

      Manually override the file messages date and time by either entering a date and time, or using the drop-down arrow that appears when the property is clicked to select a different date and time.

   3. Set Channel Packing to either Auto or Manual.

      The software supports a maximum of eight visible satellites. When set to Auto, the software automatically selects the optimal satellites for the scenario. When set to Manual and more than eight satellites exist for a time period, the software, upon clicking the Create Scenario button, displays a message on the conflict. After you acknowledge the message, it then creates and displays a Satellite Visibility view where you manually select the undesired satellites to resolve conflicts that occur in a time period with more than eight satellites.

10. If there is a need to change the leap seconds default value, click the Leap Seconds cell and set the number of Leap Seconds using the dialog box button  that appears to launch the Leap Seconds Editor. Set each leap second as either positive or negative.

    

    The default leap seconds is the official value as defined by the BIH (Bureau International of the Hour or International Bureau of Time)

11. Click the Create Scenario button to launch the Save As dialog box for selecting a location and saving the file.

    If using manual channel packing and a satellite conflict exists (more than eight satellites), the software does not create the scenario until the conflict(s) are resolved. Instead the software displays a message and creates the Satellite Visibility view where you resolve the conflicts. After resolving the conflicts, click Done in the Satellite Visibility view to create the scenario file.

    Keep the file name to 23 characters or less. If you attempt to download a file with a name that contains more than 23 characters, the download will fail and the software displays an error message.

    After creating the scenario, click on the Scenario Graphics tab to view the satellites used across the scenario for each channel.

Related Topics

Scenario Generator

Scenario Graphics

Antenna Pattern

Satellite Visibility

Downloading a Scenario

Resolving a Satellite Conflict Region