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added new modes and bitrates

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Ahmet Inan 2025-07-18 17:06:55 +02:00
commit bedd84afb4
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@ -12,7 +12,7 @@ dd if=/dev/urandom of=uncoded.dat bs=1 count=256
Encode file ```uncoded.dat``` to ```encoded.wav``` [WAV](https://en.wikipedia.org/wiki/WAV) audio file with 48000 Hz sample rate, 16 bits and only 1 (real) channel:
```
./encode encoded.wav 48000 16 1 1500 5 uncoded.dat
./encode encoded.wav 48000 16 1 1500 ANONYMOUS 176 uncoded.dat
```
Start recording to ```recorded.wav``` audio file and stop after 5 seconds:
@ -41,19 +41,53 @@ diff -s uncoded.dat decoded.dat
### Supported Modes
All modes need a bandwidth of 2400 Hz and use a 1/2-rate forward error correction code
All modes need a bandwidth of 2400 Hz.
These use a differential modulation scheme:
* Mode 0: DBPSK, 2.6 seconds and 256 bytes
* Mode 1: DQPSK, 2.6 seconds and 512 bytes
* Mode 2: D8PSK, 3.4 seconds and 1024 bytes
These are the durations for each differential modulation scheme:
And these a coherent modulation scheme:
* Mode 3: BPSK, 2.6 seconds and 256 bytes
* Mode 4: QPSK, 2.6 seconds and 512 bytes
* Mode 5: QAM16, 1 second and 256 bytes
* Mode 6: QAM16, 2.6 seconds and 1024 bytes
* Mode 7: QAM64, 3.4 seconds and 2048 bytes
| Modulation | Short | Normal |
| ---------- | ----- | ------ |
| DBPSK | 1.5s | 2.6s |
| DQPSK | 1.0s | 1.5s |
| D8PSK | 1.9s | 3.4s |
And these are the durations for each coherent modulation scheme:
| Modulation | Short | Normal |
| ---------- | ----- | ------ |
| QAM16 | 1.0s | 1.5s |
| QAM64 | 1.9s | 3.4s |
| QAM256 | 1.5s | 2.6s |
| QAM1024 | 2.2s | 4.0s |
| QAM4096 | 1.9s | 3.4s |
Currently all digital modes use a 1/2-rate forward error correction code.
Therefore we have the following byte payloads for each modulation:
| Modulation | Short | Normal |
| ---------- | ----- | ------ |
| DBPSK | 128B | 256B |
| DQPSK | 128B | 256B |
| D8PSK | 512B | 1024B |
| QAM16 | 256B | 512B |
| QAM64 | 1024B | 2048B |
| QAM256 | 1024B | 2048B |
| QAM1024 | 2048B | 4096B |
| QAM4096 | 2048B | 4096B |
Which give us the following bitrates for each modulation:
| Modulation | Short | Normal |
| ---------- | ------- | ------- |
| DBPSK | 681b/s | 789b/s |
| DQPSK | 1070b/s | 1362b/s |
| D8PSK | 2141b/s | 2398b/s |
| QAM16 | 2141b/s | 2725b/s |
| QAM64 | 4282b/s | 4795b/s |
| QAM256 | 5449b/s | 6310b/s |
| QAM1024 | 7493b/s | 8268b/s |
| QAM4096 | 8563b/s | 9591b/s |
### Simulating
@ -62,7 +96,7 @@ Prerequisite: [disorders](https://github.com/aicodix/disorders)
Encode ```uncoded.dat``` to [analytic](https://en.wikipedia.org/wiki/Analytic_signal) audio signal, add [multipath](https://en.wikipedia.org/wiki/Multipath_propagation), [CFO, SFO](https://en.wikipedia.org/wiki/Carrier_frequency_offset), [AWGN](https://en.wikipedia.org/wiki/Additive_white_Gaussian_noise), decode and compare:
```
./encode - 48000 16 2 1500 5 uncoded.dat | ../disorders/multipath - - ../disorders/multipath.txt 10 | ../disorders/cfo - - 234.567 | ../disorders/sfo - - 147 | ../disorders/awgn - - -20 | ./decode - - | diff -q -s uncoded.dat -
./encode - 48000 16 2 1500 ANONYMOUS 176 uncoded.dat | ../disorders/multipath - - ../disorders/multipath.txt 10 | ../disorders/cfo - - 234.567 | ../disorders/sfo - - 147 | ../disorders/awgn - - -20 | ./decode - - | diff -q -s uncoded.dat -
```
### Reading