GNSS Simulation Mode

NI GNSS Simulation Toolkit Help

Edition Date: April 2013

Part Number: 372446D-01

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The GNSS Simulation toolkit supports the following simulation modes: GPS only, GLONASS only, GPS+GLONASS Multiple RF Vector Signal Generators, and GPS+GLONASS Single RF Vector Signal Generator.

GPS only mode

Use this mode to simulate up to 12 GPS satellites. The toolkit chooses the number of GPS satellites based on the GPS almanac and ephemeris files, GPS time, and the receiver location that you specify.

In the GPS only mode, you can do the following:

  • Generate 24 hours of L1 (C/A codes) signal for up to 12 satellites
  • Simulate satellites automatically using almanac and ephemeris file
  • Define custom motion trajectories for mobile simulation
  • Adjust individual satellite power levels for scenario specific–tests
  • Take advantage of manual control of satellite pseudorange, Doppler, and power–level information

GLONASS only mode

Use this mode to simulate up to 12 GLONASS satellites. The toolkit chooses the number of GLONASS satellites based on the GLONASS almanac and ephemeris files, UTC time, and the receiver location that you specify.

In the GLONASS only mode, you can do the following:

  • Generate 24 hours of L1 signal for up to 12 satellites
  • Simulate satellites automatically using almanac and ephemeris file
  • Define custom motion trajectories for mobile simulation
  • Adjust individual satellite power levels for scenario–specific tests
Note Note  Glonass only mode does not support manual mode.

Using the NI GNSS Simulation toolkit, GPS+GLONASS constellation could be simulated in the following ways:

GPS+GLONASS Multiple RF Vector Signal Generators mode

The toolkit uses multiple radio frequency vector signal generators (RFSGs) for GPS+GLONASS streaming application. One RFSG generates a GPS satellite signal, and the other RFSG generates a GLONASS satellite signal.

Refer to the niGNSS Direct Streaming Generation on Multiple RFSGs.vi example for more information about GPS+GLONASS multiple RFSG streaming. The two RFSGs are synchronized in time.

The example VI contains the input parameters for both the GPS and GLONASS modes using two sessions in parallel. You must take care of the leap seconds conversion between the Initial GPS time and Initial UTC time specified in the example front panel. Provide the receiver location in WGS–84 format for the GPS simulation and the receiver location in PZ 90.02 format for the GLONASS simulation.

GPS+GLONASS Single RF Vector Signal Generator mode

The toolkit also generates GPS+GLONASS constellation using a single RFSG by writing to a TDMS file and streaming from it.

Use the toolkit to create a file (offline) containing GPS+GLONASS constellation signal at a high sample rate, for example 60 MS/s) using the example “niGNSS Write Waveform to File (Simple,Automatic Mode).vi”. The file that is created is very large in size and hence, may be stored on a RAID disk containing a large space. The GPS + GLONASS constellation data is read from the file on the RAID disk at a high rate and generated from the RFSG using the example VI “niGNSS Streaming from TDMS file.vi”.

Note Note  This mode is available only in LabVIEW 2011 or later.

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