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RACELOGIC Support Centre

11 - LabSat 2 Replaying GNSS Data

Note: Applicable to RLLSP02-GNL1 and RLLSR02-GNL1 LabSat 2 Models.

Any LabSat 2 unit can replay a recorded scenario file to any connected GNSS device capable of receiving the L1 GPS signal, E1 Galileo, B1 BDS, L1 GLONASS signals. So that the receiver under test can accept the LabSat scenario it is strongly recommended that the receiver is cold started prior to each replay. This will remove and almanac and ephemeris data from the receiver to allow for the data contained in the scenario to be used.

Note: LabSat 2 is designed for direct connection to a GNSS receiver via a suitably screened cable.  If testing is to be performed on GNSS equipment without an external GNSS antenna connection, it is the responsibility of the user to ensure that this is done in a fully RF screened environment, such as an anechoic chamber to avoid interference with other GPS/GLONASS receivers.

Contact Racelogic for more information.

The LabSat 2 is connected as illustrated in the diagram below:

  1. Connect the high speed USB cable from the LabSat 2 to the computer the Scenario data file will be replayed from.
  2. Connect power to the LabSat 2, and the recipient GNSS device.
  3. The LabSat 2 comes supplied with a number of adaptor cables which allow connection to a number of GNSS devices.  Select the appropriate antenna cable for the device to be connected.
  4. Connect the RF-OUT connector of the LabSat 2 (illustrated below) to the GNSS antenna input of the device.
  5. Start the LabSat software.
  6. The LabSat 2 is now ready to replay GNSS data to the DUT (Device under Test).  Select the Replay Mode tab on the LabSat 2.  The LabSat 2 is now ready to replay GNSS RF data.

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  1. Once the GNSS device is powered and ready to receive data and has been cold started, press the Browse button to locate the scenario required for the test. The Info button will display a full description of the scenario as entered in the description box display on the record screen. Information is also displayed about the LabSat recorder used and its configuration settings.

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  1. Click the Play button to start scenario replay on LabSat 2. 
  2. The progress bar gives a visual indication of the current progress through the scenario file being replayed.
  3. The total duration of the scenario selected, and the progress of the scenario replay are also shown on the LabSat software, above.
  4. The replay of the file can be stopped and restarted by pressing the ‘Stop’ button then the ‘Play’ button at any point during Playback.
  5. During Replay the Buffer display may be selected, to display memory buffer loading.  The LED display on the LabSat 2 front panel also indicates the status of the buffer.

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  1. The Advanced Playback Control feature on LabSat 2 contains a feature that allows you to repeat the same scenario over again, so that at the end of the scenario replay the LabSat 2 will loop back to the start of the scenario, and start replaying the scenario over again. 

    The user can specify the number if repeats, or set the scenario to repeat indefinitely. You can also specify a time delay between repeats, for example to allow time for a cold-start of the DUT before the scenario re-starts. In the example shown below, four repeats have been selected, with a delay of 30 seconds between each repeat of the scenario replay.

    Note: At least 30 seconds of constant satellite data is required for the receiver to collect the necessary data to use that satellite so choose sections of the recording with good view of the sky reflect the real world situation when commencing replaying a section of the scenario.

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  1. The Advanced Playback Control also allows users to define a specific start point, end point, or duration of a scenario. In the example shown previously the scenario is set to start 28 seconds from the beginning, and the end point has been set to 1 minute 50 seconds into the scenario, giving a total scenario replay time of 1 minute 22 seconds.The slider position, on Advanced Playback Control indicates progress along the specified scenario length. The scenario may also be fast forwarded, and rewound, by clicking on the progress pointer, and dragging it along the blue progress bar. If you wish to start replaying a scenario at some point other than the start of the file.

    The Start Point setting may be used to specify the time to advance the replay start point. By combining the ‘Start Point’ and ‘End Point’ or ‘Length’ functions, it is possible to select a particular time segment out of any given scenario. The LabSat 2 will stop replaying the scenario when the replay duration has reached the time specified on the scenario length setting.
  2. The Channel Mode selector will allow for the replay to separate out the data recorded. For example a Channel A+B 1 bit recorded scenario can be replayed as a GPS and GLONASS file, GPS only or GLONASS only. A Channel A 2 bit GPS only - 2 bit I & 2 bit Q recorded file will play the 2 bit file as recorded or can be set to replay GPS 1 bit only.
  3. Depending on the sensitivity of the GNSS engine under test, it may be necessary to adjust the output attenuation control slider. This can be used to vary the output power of the LabSat 2 from a nominal -83 dBm down to -107 dB.  In the example below, the digital output attenuator has been set to provide 15.5 dB of attenuation on channel A and 8.5 dB on Channel B. 

    It is recommended to try the 0 dB slider setting (-83 dBm output) first. If the GNSS engine under test does not lock onto the LabSat 2 signal at 0 dB then increase the attenuation slider by 0.5 dB at a time and replay the file. It is also advisable to cold start the GPS / GLONASS device under test after starting each replay to clear any almanac data that the GNSS engine may have stored. By ticking the Linked Box the relationship between the attenuation on each channel is linked and fixed to each other. 

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  1. The digital noise function allows degradation of the replayed GNSS signals by mixing a noise source with the original recorded/simulated file. The Digital Noise slider in the LabSat software is used to adjust the output signal from 0% noise to 100% noise. At the 0% noise setting, the signal output is 100% of the original signal.

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  1. For GNSS Monitor details please refer to page 17 in the previous section.
  2. The Video Sync is a powerful way of using a video recording of your live route to replay in synchronisation with the LabSat scenario file. For a full descriptions please go the the Video Synchronisation section. To play a LabSat scenario with the recorded video VBOX recording please tick the video sync tick box in the plug-in section of settings. The video sync drop down section will appear in the relay section of the software.

    Locate the LabSat file as normal using the browse button and then locate the browse button in the video sync drop down menu. Click on the vbo file located in the same folder as the Video recording file. Wait for the file to load in the software and then click on the play button as normal. The LabSat scenario file will then play in synchronisation with the Video VBOX video. Please ensure that the GPS monitor is enabled and is showing the live data from the LabSat scenario. 

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The video VBOX video shown in the software can be expanded by clicking on it to the full screen size of the computer screen.

  1. Click Stop, to halt replay of GNSS RF data and the video replay.
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