I'd like to add support for GPS L2 signals - need some direction.

[bangpradyumna]

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!