[aprssig] NEW! IC-V82 - VHF/APRS Transceiver
Stephen H. Smith
wa8lmf2 at aol.com
Thu Mar 3 01:57:53 CST 2005
After wading through all the broken English in the technical description
and PowerPoint presentation on the Icom site, my conclusion was that
the whole D-Star system is far too complex for widespread adoption by hams.
It turns out there are TWO separate on-air transmission formats - a
4.8Kb/sec stream for low-speed data (like callsign ID, selective calls
and GPS posits) and AMBE-vocoded digitized speech --and-- a
high-speed 128KB/sec mode that amounts essentially to ".1BaseT"
Ethernet. Separate receivers and transmitters are used at the
repeater site for each format.; i.e. you have to somehow combine two RX
and two TX into your antenna system(s) for a single "channel".
The low-speed format is for use on 2 and 440 while both the low and
high-speed formats would be available on 1260 only.
The system architecture (clusters of 144/440/1260 repeaters in one area
tied together by 10 GHz RF links are connected to clusters in other
geographic areas via high-speed Internet connections) has a strangely
close resemblence to the architecture of Motorola SmartZone commercial
networks, even to the QOS prioritizing of voice vs non-voice packets in
it's IP neworks.
Oddly, one of the most interesting documents on the Icom site (though
incredibly dry) was the "history" of the development of this system
which involved an absolutely ludicrous amount of politics between JARL
(Japan Amateur Radio League), various government ministries and Icom to
be authorized to put this experimental system on the air on existing ham
bands. It appears that there was a lot of support and seed money
provided by the Japanese Communications Ministry. Near the end of this
account was the final outcome that no more than two hops over-the-air
would be allowed (more than that would require Internet linking) because
more than that would constitute "a commercial communications
company"! [ At least it addresses abusively long paths .... ]
------ BOTTOM LINE ------
I wonder if this whole thing is kind of a beta test for a kind of
Made-In-Japan "Smartzone Lite" to be sold in the commercial landmobile
market to public safety users in smaller communities that can't afford
the incredible complexity and expense of Motorola's current offerings.
[ Motorola has completely abandoned the analog and small-systems market
already to the Japanese land-mobile mfrs and New Zealand's Tait Radio.
Moto quite making analog base stations last September.]
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
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