Commit graph

26 commits

Author SHA1 Message Date
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