Regarding the Acquisition of GPSSIM.bin file by GPSSDR SIM

[komalkumar6655]

Hello, I have generated the gpssim.bin file . But i cant get the acquisition results in GNSS SDR. Please help me with this Thank You.

[jonathanmuller]

Hi, extremely late reply but may help anyone with the same problem :

You probably want to use this in your conf file :

;######### SIGNAL_SOURCE CONFIG ############
SignalSource.implementation=File_Signal_Source
SignalSource.filename=/path/to/your/file/gpssim.bin
SignalSource.item_type=ishort
SignalSource.sampling_frequency=4000000
SignalSource.freq=1575420000
SignalSource.samples=0

And make sure to use the conf by using the "-c" option of the command line : gnss-sdr --config_file=../conf/from_file.conf

Depending on how you generated your .bin you should adapt the frequency For example gps-sdr-sim use 2600000 by default

Full explanation here : https://gnss-sdr.org/docs/sp-blocks/signal-source/

[fungaren]

It seems if sampling frequency is set to 2600000 (default value), gnss-sdr failed to decode GPS NAV message. But sampling freq set to 4000000 is OK:

./gps-sdr-sim -e brdc3470.21n -l 39.915119,116.403963,100 -b 8 -s 4000000 -d 240 -o ~/tmp/gpssim.bin

Acquisition/tracking is working fine, but cannot get position fix:

Current receiver time: 3 min 44 s
Current receiver time: 3 min 45 s
Current receiver time: 3 min 46 s
Current receiver time: 3 min 47 s
Current receiver time: 3 min 48 s
Current receiver time: 3 min 49 s
New GPS NAV message received in channel 7: subframe 3 from satellite GPS PRN 15 (Block IIR-M)
New GPS NAV message received in channel 3: subframe 3 from satellite GPS PRN 05 (Block IIR-M)
New GPS NAV message received in channel 1: subframe 3 from satellite GPS PRN 18 (Block III)
New GPS NAV message received in channel 0: subframe 3 from satellite GPS PRN 23 (Block III)
New GPS NAV message received in channel 4: subframe 3 from satellite GPS PRN 20 (Block IIR)
New GPS NAV message received in channel 5: subframe 3 from satellite GPS PRN 29 (Block IIR-M)
New GPS NAV message received in channel 2: subframe 3 from satellite GPS PRN 30 (Block IIF)
New GPS NAV message received in channel 6: subframe 3 from satellite GPS PRN 02 (Block IIR)
Current receiver time: 3 min 50 s
Current receiver time: 3 min 51 s
Current receiver time: 3 min 52 s
Current receiver time: 3 min 53 s
Current receiver time: 3 min 54 s
Current receiver time: 3 min 55 s
New GPS NAV message received in channel 7: subframe 4 from satellite GPS PRN 15 (Block IIR-M)
New GPS NAV message received in channel 1: subframe 4 from satellite GPS PRN 18 (Block III)
New GPS NAV message received in channel 3: subframe 4 from satellite GPS PRN 05 (Block IIR-M)
New GPS NAV message received in channel 0: subframe 4 from satellite GPS PRN 23 (Block III)
New GPS NAV message received in channel 5: subframe 4 from satellite GPS PRN 29 (Block IIR-M)
New GPS NAV message received in channel 4: subframe 4 from satellite GPS PRN 20 (Block IIR)
New GPS NAV message received in channel 2: subframe 4 from satellite GPS PRN 30 (Block IIF)
New GPS NAV message received in channel 6: subframe 4 from satellite GPS PRN 02 (Block IIR)
Current receiver time: 3 min 56 s
Current receiver time: 3 min 57 s
Current receiver time: 3 min 58 s
Current receiver time: 3 min 59 s
Current receiver time: 4 min 0 s
Stopping GNSS-SDR, please wait!
Total GNSS-SDR run time: 14.4205 [seconds]
GNSS-SDR program ended.

[ZiglioUK]

Actually I was having a related issue last week, when I tried to replay some simulated data from gps-sdr-sim through a HackRF. I was wondering why the default value wasn't a "round" number. I settled on 2MHz in order to limit the file size.

Unrelated, I thought hackrf_transfer would save files as unsigned 8 bits (like the rtl-sdr) but expects to read them as signed. I'm really confused.

[update] Ok, here's the configuration for a file generated for the HackRF:

SignalSource.item_type=ibyte
SignalConditioner.implementation=Signal_Conditioner
DataTypeAdapter.implementation=Ibyte_To_Complex

This is for a gpssim.bin file that's been generated with the -b 8 option, like the configuration in the message above.