Fellow members, after so much discussion flying around regarding DSTAR, I
thought I’d refresh my memory of the situation, and write it down in as few
words as I can.
Overview
=======
DSTAR was launched in 2001, thus it’s 14 years old. It was intended to drive
digital radio adoption generally for non-broadcast applications and was funded
by the Japanese Government. ICOM have commercially implemented the protocols
using proprietary software [1] https://en.wikipedia.org/wiki/D-STAR
<https://en.wikipedia.org/wiki/D-STAR>
Is the system open or not? No, it is most certainly not in the ICOM form, and
the open-source codec and gateway under development do not and can never change
that. Anyone who has purchased an ICOM radio is forever on the proprietary
system.
There is an alternative codec under development, called Codec2, and an
open-source gateway, so it’s possible that in the future, yet another system
will appear which will be open to all, so anyone can build the equipment, or
modify existing equipment; this will see the price tag fall, but seems a long
way off at the moment.
Details:
Voice Codecs
==========
AMBE: The system provides voice communications using a digital codec, a
coder-decoder which is a type of analogue to digital convertor with
compression, from a family of codecs called AMBE. These codecs are proprietary
[1]. Licensing charges are thought to range for $100,000 to $1,000,000, which
explains at least partly why the equipment is so incredibly expensive.
https://en.wikipedia.org/wiki/Multi-Band_Excitation
<https://en.wikipedia.org/wiki/Multi-Band_Excitation>
The dongle: There is a USB dongle available which contains an instance of the
AMBE codec which can interwork with Icom radios, but is intended to be used as
an internet connected node. It is proprietary, uses proprietary drivers, but
has drivers for some versions of Windows, Apple OS X and Linux. Users should
be aware that when the vendor decides to stop supporting the device, it will no
longer work with ‘new’ versions of operating systems.
http://www.dvdongle.com/DV_Dongle/Home.html
<http://www.dvdongle.com/DV_Dongle/Home.html> It appears to sell for between
£150 and £200. Bargain? Perhaps, as the Icom radios seem to push £500.
Codec2: There is an open source [2] project to create an alternative codec,
imaginatively called Codec2. Please note that this will *not* interwork with
Icom DSTAR radios, rather, it will only work with radios using Codec2!
https://en.wikipedia.org/wiki/Codec2 <https://en.wikipedia.org/wiki/Codec2>
Data link, voice trunking and ‘internet linking’
==================================
The system also provides a data link capability, and uses IP protocol to link
nodes (think repeaters) together, so that trunking between repeaters takes
place over an IP network, which can be the public internet, or can be a private
network of some kind.
Opendstar.org/design <http://opendstar.org/design> : this is a design for an
open-source Gateway, designed to run on a small, low power computer, such as a
link sys wireless router (wrt54gl type), or similar, although a larger linux PC
will also be fine. The gateway will register into the proprietary Icom DSTAR
network and act as a node for handling both voice and data traffic. It does
support the ‘dongle’ noted above, so does provide a sort of working system at
rather less than the cost of an actual radio, but obviously, it’s not a radio.
And finally… has anyone cracked the AMBE codec, or any of the protocols? What
about RTL-dongles?
================================================================================
Actually, unsurprisingly, it would appear that the AMBE codec has been cracked,
at least for decode. RTL dongle code can be found from here:
http://www.rtl-sdr.com/listening-d-star-digital-voice-dsd-1-7/
<http://www.rtl-sdr.com/listening-d-star-digital-voice-dsd-1-7/>
An RTL solution for unpicking the text messages is here:
http://www.rtl-sdr.com/decoding-d-star-headers-rtl-sdr/
<http://www.rtl-sdr.com/decoding-d-star-headers-rtl-sdr/>
Is it legal? An interesting question. Software patents are currently not
legitimate in the EU, details are here in note 3 below, but in short, in the UK
and other EU countries, yes, it is legal. Also, it’s worth noting that
decoding encrypted satellite broadcasts is also specifically legal in the UK,
which is unusual in this respect. I don’t know whether that would apply to
DSTAR, but it’s possible.
Now the notes:
============
Note 1: Proprietary means that the source-code is only known to the vendor,
such as Icom, so it cannot be modified by a user. Proprietary software usage
is generally licensed, but it can be free of charge or can incur a one-off, or
a repeating charge. The software is ‘patented’ (something strictly not legal
in the EU or the UK, but even so…)
Note 2: Open source (GNU licence) in this context means that the licensing
for the software forces anyone who modifies and redistributes it to include the
source-code. This means that no company or individual can ever lock users out
of the system. Open source is not necessarily free of charge, but you cannot
stop a third party from giving it away.
Note 3:
https://en.wikipedia.org/wiki/Software_patents_under_the_European_Patent_Convention
<https://en.wikipedia.org/wiki/Software_patents_under_the_European_Patent_Convention>
The EU has a much higher standard for invention than the US. In the US,
someone has even managed to patent a number (this is true!). The UK position
is that it must align as far as possible with the EU. In the UK, software has
never been patentable, rather, it’s subject to copyright law.
