Commit graph

37 commits

Author SHA1 Message Date
Thomas Kolb 84c172abc7 Fixed iterative frequency refinement; count header errors 2024-01-05 21:28:38 +01:00
Thomas Kolb 3a4be428b5 sdr: stop reading packets if the TX buffer is too full 2024-01-05 14:13:11 +01:00
Thomas Kolb be5fa06950 Handle SIGTERM and SIGINT for graceful shutdown 2024-01-03 22:03:19 +01:00
Thomas Kolb 8689ed5b27 Use fsleep instead of nanosleep 2024-01-03 17:29:51 +01:00
Thomas Kolb c9d53ed96e Ensure that buffer is full when transmission starts 2024-01-03 00:33:54 +01:00
Thomas Kolb 628659511c sdr: properly flush the transmit buffers 2024-01-03 00:25:55 +01:00
Thomas Kolb ef0fad4335 Improved handling of up- and downsampling 2024-01-02 23:49:55 +01:00
Thomas Kolb 2b741acd8a Use libhackrf directly (not tested yet) 2024-01-02 22:49:16 +01:00
Thomas Kolb 7995f5bef0 Print RX stats periodically instead of debug logging 2024-01-02 19:04:19 +01:00
Thomas Kolb 112a8a1215 Improved logging and soapy stream handling 2023-05-20 22:01:26 +02:00
Thomas Kolb f5a367464f Optimized one-shot frequency synchronization
- Ramp-up length increased to 128 symbols (here is room for
  improvement!)
- Try to detect the frequency once during ramp-up. To do so, every
  second symbol is inverted (to remove the +/-1 symbol toggling) and the
  phase difference between neigboring resulting symbols is checked. When
  it is low enough for all symbols, the frequency is estimated and
  corrected. When frequency estimation was done, it is not retried for a
  number of incoming symbols in order to allow the timing estimator to
  converge again.
- This approach was verified in a simulated loopback test with frequency
  offset and AWGN.
2023-05-17 22:28:18 +02:00
Thomas Kolb c8e0516e80 Implement time-based carrier sensing
In the following events, the modem cannot switch to transmit mode for the
given time:

- after a preamble has been received, for 500 ms
- after a packet has been successfully decoded, for 1 ms
- after receive mode was initially enabled, for 500 ms

Note that the times are that long to work around the RX/TX switching of
the hackrf and can be hopefully reduced to <10 milliseconds in a later
version.
2022-05-07 21:17:53 +02:00
Thomas Kolb b2d6c713e1 Briefly start in TX mode to ensure correct RX frequency
Obviously SoapyHackRF does not set the correct RX frequency on startup.
This is a crude but effective workaround.
2022-05-07 20:12:03 +02:00
Thomas Kolb 715cda83a8 RX: process samples in larger chunks 2022-04-07 21:17:37 +02:00
Thomas Kolb 47fc177e87 Reorganize Soapy stream management; flush tx buffer 2022-04-03 18:11:52 +02:00
Thomas Kolb 152d2f02f6 Basic transmitter-only main loop 2022-03-05 21:38:05 +01:00
Thomas Kolb 45156e64a0 Show packets as hexdump instead of text 2022-02-27 22:01:51 +01:00
Thomas Kolb 934b18e382 Integrate TUN device interface
Packets are now read from the TUN device and transmitted. The signal
goes through a channel emulator and is then received + decoded. If
decoding is successful, the result is written back to the TUN device
(which does not make much sense, but works for testing).

Unfortunately, there still seems to be a problem in the receiver: packet
loss is very high even at extremely high SNRs.
2022-02-27 20:21:14 +01:00
Thomas Kolb 8a8ddc5ea3 rx: integrate AGC 2022-02-27 16:59:14 +01:00
Thomas Kolb 0ed7109335 Clean up debug output 2022-02-16 21:46:56 +01:00
Thomas Kolb 876bafd6f9 Moved receiver to separate module 2022-02-16 20:52:46 +01:00
Thomas Kolb a5634ed736 Move the transmission chain to a separate "tx" module 2022-02-13 21:29:35 +01:00
Thomas Kolb 513a399ae4 Refactoring: moved layer1-related stuff to subdirectory 2022-02-13 20:05:47 +01:00
Thomas Kolb eb3fc5f9c7 Use data whitening 2022-02-12 22:06:49 +01:00
Thomas Kolb 87b844a2da Implement CRC check and phase tracking 2022-02-12 21:58:53 +01:00
Thomas Kolb 947615f5cd First complete RX chain
Decoding of the test message works down to ~10 dB SNR.

Still missing:
- Phase tracking during header and payload.
- CRC calculation and check.
- Data whitening.
2022-02-11 17:56:26 +01:00
Thomas Kolb 042c05f9f3 Decode the received header 2022-02-10 22:33:51 +01:00
Thomas Kolb f2c95a125d Use new frequency+phase estimation method for preamble 2022-02-06 18:04:31 +01:00
Thomas Kolb 8060137c1d Move frequency estimation to separate module 2022-02-05 20:33:56 +01:00
Thomas Kolb 465d9a1c26 main: restructure state management; evaluate a found preamble 2022-02-03 22:18:24 +01:00
Thomas Kolb c17c7e060f Integrate preamble search 2022-02-01 21:35:43 +01:00
Thomas Kolb b6713909f7 Make initial frequency sync much faster
The NCO frequency is now only adjusted every 8 symbols. That means that
the frequency error over the last 8 symbols before the adjustment is
(almost) constant, giving a good estimation result. Therefore, the
adjustment factor can be much larger than previously, leading to faster
acquisition time.
2022-01-30 20:23:41 +01:00
Thomas Kolb c1dd039d6b First shot at frequency synchronization
Supports only the BPSK part so far (ramp-up, preamble).
2022-01-30 20:05:20 +01:00
Thomas Kolb 09465591ed Added symsync to the receiver chain 2022-01-29 22:37:55 +01:00
Thomas Kolb d522a1d6bd Implemented pulse shaping
The pulse shaper currently uses an RRC filter with beta=0.2.
2022-01-29 22:05:17 +01:00
Thomas Kolb 874d8d5073 Fixed the modulator + test demodulation 2021-10-17 19:45:54 +02:00
Thomas Kolb 9ba470adeb Initial implementation of packet modulation
Not really tested yet…
2021-10-17 19:26:38 +02:00