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osqzss / gps-sdr-sim

Software-Defined GPS Signal Simulator
MIT License
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I'd like to add support for GPS L2 signals - need some direction. #414

Open bangpradyumna opened 2 months ago

bangpradyumna commented 2 months ago

Hello @osqzss , I've recently been introduced to the wonderful world of GNSS and the gps-sdr-sim works perfectly for simulating GPS L1 signals.

I would really love to contribute to this repo and learn more about how GPS signals are formed, and for that I feel a good way is to implement GPS L2 functionality in this repository.

I must admit that I'm a bit overwhelmed by the code but I was wondering if I could get some directions on how to go about implementing GPS L2.

Based on my research, this is what i feel is required for GPS L2 support in current code :

  1. Carrier Frequency: Add support for 1227.60 MHz for L2.
  2. PRN Codes: Implement L2 CM/CL PRN code generation.
  3. Modulation: Modify the modulation logic for L2 (BPSK with CM/CL codes and CNAV data).
  4. Configuration: Generate dual frequency IQ files and test them with the SDR's and receivers. (Question - Would I need to use dual channel SDR for L1 and L2 generation or the same channel will be able to transmit in both frequencies ?)

Please let me know if I've missed anything in the above points, if you have any recommendations - I'd really appreciate them.

Thanks!

osqzss commented 2 months ago

Thank you for your contribution. I have just made a 'develop' branch for these new signals. Please push your commits to it. Regarding your question 4, there is no dual-channel SDR available a reasonable price. You need separate IQ files and a pair of SDR devices for L1 and L2 signals.

bangpradyumna commented 1 month ago

Thanks @osqzss, I'm using a USRP B210 which is dual channel so I can test it.

However, What do you think about the approach that I've described ? Is that a good one to start with or am I missing something there ?

slblbwl commented 3 days ago

Hello, I also want to use GPS-SDR-SIM to transmit L2 GPS signals. I would like to discuss with you how to transmit, is that okay?