The Benefits of Recorded GNSS Signals

 

Record & Replay is a technique with which previously recorded GNSS data is replayed to run software and hardware tests.

This technique can faithfully reproduce all the propagation phenomena that altered the GNSS signal between the satellite antenna and that of the receiver's one.

 

1. Repeatability

Record/Replay is highly repeatable, which means one can run the same test multiple times and compare the agreement between results to ensure reliability.

 

2. Fidelity, but only with the right settings!

The true value of Record/Replay is the fidelity of recorded signals. A proper setting of the sampling frequency and the number of bits used by the quantization process is needed to preserve the information on the specific environment, assuring the fidelity of the recorded scenario with respect to the real one. 

If the level of quantization is too low, only a fraction of signal variables can be seen and characterized. On the contrary, if quantization's level is high, then recorded content has a much higher testing value.

8-bits I&Q of quantization and 50 MHz are usually considered as a good starting point for GNSS Record and Playback. This implies at least 100Mb/s recording capabilities for a single frequency (3 times more while testing L1, L2, and L5 simultaneously). We consider perfect reproduction once settings are reaching 16 bits I&Q quantization and 100 Mhz sampling rate on 3 bands simultaneously (requiring a 1200MB/s recording speed).

 

3. Cost savings

Record/Replay is often much more affordable than real-world testing, so engineers can now cheaply run multiple tests while developing components. It’s also relatively risk-free since they are not sending expensive prototypes into the real world.


Echo_RecorderPlayer


Learn more about the GNSS Recorder & Player:
Syntony GNSS Echo R&P


 


Limitations of recorded data

One problem with Record/Replay is that testing data will be limited in scope. You can only record what is happening in real-time, but that doesn’t mean you have recorded everything that can ever happen. Testing data will be limited to whichever events have been recorded.

Another limitation of Record/Replay is that variables cannot be isolated. This is a problem if you want to isolate a particular phenomenon and evaluate how your system performs under a slight change. As a result, R/R is a more holistic approach to testing.

Beyond the limitations

Leveraging the complementarity of simulated signals


Using simulated GNSS signals solves the limitations of recorded signals, to learn more by reading the following article:

 


 

Constellator_Full

 

Learn more about the GNSS Simulators:
Syntony GNSS Constellator