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README: update modem info.

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This commit is contained in:
Roman Zeyde
2015-01-08 18:24:26 +02:00
parent ae7d742ee4
commit c2a4bfbd5e
1 changed files with 12 additions and 17 deletions
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29
README.md
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@@ -26,11 +26,11 @@ receiving microphone.
The modem is using OFDM over an audio cable with the following parameters:
- Sampling rate: 32 kHz
- BAUD rate: 1 kHz
- Symbol modulation: 64-QAM
- Carriers: (1,2,3,4,5,6,7,8) kHz
- Baud rate: 1 kHz
- Symbol modulation: BPSK, 4-PSK, 16-QAM ,64-QAM
- Carriers: 2-11 kHz
This way, modem achieves 48kbps bitrate = 6.0 kB/s.
This way, modem may achieve 60kbps bitrate = 7.5 kB/s.
A simple CRC-32 checksum is used for data integrity verification
on each 250 byte data frame.
@@ -38,14 +38,9 @@ on each 250 byte data frame.
# Installation
Make sure that `numpy` and `PyAudio` Python packages are installed.
Make sure that `numpy` and `PortAudio v19` packages are installed (on Debian):
$ pip install numpy
$ pip install git+http://people.csail.mit.edu/hubert/git/pyaudio.git
or, on Debian/Ubuntu:
$ sudo apt-get install python-numpy python-pyaudio
$ sudo apt-get install python-numpy portaudio19-dev
Clone and install latest version:
@@ -60,7 +55,7 @@ For graphs and visualization (optional), install:
Run:
$ export BITRATE=48 # explicitly select highest MODEM bit rate (assuming good SNR).
$ export BITRATE=16 # explicitly select high MODEM bit rate (assuming good SNR).
$ amodem-cli -h
usage: amodem-cli [-h] {send,recv} ...
@@ -82,13 +77,13 @@ following scripts:
- On the sender's side:
```
~/sender $ export BITRATE=48 # explicitly select highest MODEM bit rate (assuming good SNR).
~/sender $ export BITRATE=48 # explicitly select high MODEM bit rate (assuming good SNR).
~/sender $ amodem-cli send --calibrate
```
- On the receiver's side:
```
~/receiver $ export BITRATE=48 # explicitly select highest MODEM bit rate (assuming good SNR).
~/receiver $ export BITRATE=48 # explicitly select high MODEM bit rate (assuming good SNR).
~/receiver $ amodem-cli recv --calibrate
```
@@ -126,12 +121,12 @@ background noise or increase the signal (without causing saturation).
- Start the receiver, which will wait for the sender to start:
```
~/receiver $ amodem-cli recv -vv >data.rx
~/receiver $ amodem-cli recv -vv -i data.rx
```
- Start the sender, which will modulate the data and start the transmission:
```
~/sender $ amodem-cli send -vv <data.tx
~/sender $ amodem-cli send -vv -o data.tx
```
- A similar log should be emitted by the sender:
@@ -183,7 +178,7 @@ background noise or increase the signal (without causing saturation).
Make sure that `matplotlib` package is installed, and run (at the receiver side):
```
~/receiver $ amodem-cli recv --plot >data.rx
~/receiver $ amodem-cli recv --plot -o data.rx
```