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       ACARSX


1. Overview 
===========

acarsx is a free, realtime and accurate ACARS demodulator for embeded linux.
It can be run in a 3G router (TP-LINK W703n, TLMR13U...) as a daemon to
supply net service.

This tool is based on the project of acarsdec 2.3 hosted in sourceforge.


1.1 Features
-------------

 + Up to six channels decoded simultaneously
 + Error detection AND correction
 + Could send packet over UDP in planeplotter format


1.2 Usage
----------

acarsx [options] -r <rtl_dev_num> f1 [f2...f6]

<rtl_dev_num> is the rtl dongle number starting from 0
f1 and optionaly f2 to f6 are frequencies in Mhz
Example: acarsx -r 0 131.450 131.825

Options:
 -v            verbose output
 -A            don't display uplink messages
 -o <format>   output format: 0, no log; 1, one line by msg; 2, full(default)
 -l <logfile>  append log messages to logfile (Default: stdout)
 -n <ip:port>  send acars messages to ip:port on UDP

 -g <gain>     set rtl preamp gain in tenth of db (ie. -g 70 for +7db)
 -p <ppm>      set rtl ppm frequency correction
 -h            show this help message



1.3 Build
----------

It depends on 1 external library: librtlsdr.

It is for software radio rtl dongle. The lib homepage:

  http://sdr.osmocom.org/trac/wiki/rtl-sdr



2. ACARS
===========

ACARS (Aircraft Communications Addressing and Report System) is a digital
datalink system for transmission of short messages between aircraft and ground
stations via airband radio (VHF/HF) or satellite (Iriduim/Inmarsat). The
protocol was designed by ARINC (Aeronautical Radio, Incorporated) and deployed
in 1978, using the Telex format.


2.1 Specicication
------------------

The core specification documents of the ACARS:

  o ARINC 618, AIR/GROUND CHARACTER-ORIENTED PROTOCOL SPECIFICATION
  o ARINC 620, DATALINK GROUND SYSTEM AND INTERFACE SPECIFICATION
  o ARINC 622, ATS Data Link Applications over ACARS Air-Ground Network
  o ARINC 623, CHARACTER-ORIENTED AIR TRAFFIC SERVICE (ATS) APPLICATIONS


2.2 VHF Frequency
------------------

118MHz - 136.975MHz, 25KHz Step, 760 channels

  o 131.450MHz China(Including Hong Kong and Macau)
  o 131.450MHz Japan, Mongolia, Australia
  o 131.450MHz Southeast Asia(Thailand, Malaysia, Singapore, Philippines)
  o 131.550MHz North America(Canada, United states, Mexico)
  o 131.550MHz South America
  o 131.550MHz Guam, Saipan
  o 131.725MHz South Korea, Taiwan 
  o 131.825MHz India
  o 131.825MHz Europe and Middle East

  o 131.475MHz Air Canada
  o 136.850MHz SITA North American


2.3 DSP 
--------

DSP, Data Service Provider:

The DSP of china aviation is Aviation Data Communication Corporation(ADCC)

  + ADCC:     VHF, 131.450MHz, China
  + ARINC:    VHF/VDL Mode2/HF/Satellite, 131.550MHz, America
  + SITA:     VHF/VDL Mode2/Satellite, 131.825MHz, Europe
  + AEROTHAI: VHF, 131.450MHz, Thailand
  + AVICOM:   VHF, 131.550MHz, Japan 
  + GLOBALINK: ARINC + ADCC + AEROTHAI