What is D-STAR?
D-STAR, which stands for Digital Smart
Technologies for Amateur Radio, is a digital voice and data protocol
designed for amateur radio. It was developed in the late 1990's by the
Japan Amateur Radio League (JARL) in an effort to find new ways to
bring digital technology to amateur radio. The original study was
funded by Japan's Ministry of Posts and Telecommunications, and
administered by the JARL.
By 2004, Icom, which was involved with the development of the protocol,
began releasing "D-STAR optional" transceivers, beginning with the
IC-2200H. Although "D-STAR ready," these transceivers required the
yet-to-be-released UT-118 add on card required for use with D-STAR.
D-STAR transfers both voice and data via digital encoding over the 2 m
(VHF), 70 cm (UHF), and 23 cm (1.2 GHz) amateur radio bands. There is
also an interlinking radio system for creating links between systems in
a local area on 10 GHz, which allows emergency
communications oriented networks to continue to link in the event of
internet access failure or overload.
application chart above, shows the various modes and applications
available with D-STAR
Within the D-STAR Digital Voice protocol standards (DV), voice audio is
encoded as a 3600 bit/s data stream using proprietary AMBE encoding,
with 1200 bit/s FEC, leaving 1200 bit/s for an additional data "path"
between radios utilizing DV mode. On air bit rates for DV mode are 4800
bit/s over the 2 m, 70 cm and 23 cm bands.
In addition to digital voice mode (DV), a Digital Data (DD) mode can be
sent at 128 kbit/s only on the 23 cm band. A higher-rate data protocol,
currently believed to be much like ATM, is used in the 10 GHz "link"
radios for site-to-site links.
Radios providing DV data service within the low-speed voice protocol
variant typically use an RS-232 or USB connection for low speed data
(1200 bit/s), while the Icom ID-1 23 cm band radio offers a standard
Ethernet connection for high speed (128 kbit/s) connections, to allow
easy interfacing with computer equipment.
Excitation (AMBE) is the technology that is used in D-STAR to compress
voice for transmission. AMBE is implemented in the AMBE-2000 or
AMBE-2020 chips which are found within every D-STAR radio. The
AMBE-2000™ Vocoder Chip, which is manufactured by Digital Voice
Systems, Inc.(DVSI), implements DVSI’s patented
and award winning
AMBEŽ Voice Compression Algorithm. The field-proven success of this
technology has resulted in its recognition as the standard for voice
quality in communication systems around the globe. Satellite systems
such as ACeS, AMSC/TMI, ICO, Inmarsat, Iridium, Optus and Thuraya use
this technology because of its superior voice quality at low bit rates.
radios, repeaters, and dongles
One of the biggest
criticisms of D-STAR is its use of a closed-source proprietary codec,
which unfortunately means that amateur radio operators do not have
access to the specification or the rights to implement it on their own
without buying a licensed product. This goes against amateur radio's
long standing tradition of building, improving upon and experimenting
with radio designs. The modern digital age equivalent of this would be
designing and/or implementing codecs in software. Critics say the
proprietary nature of AMBE and its availability only in hardware form
(as ICs) discourages innovation, however, hams have been involved with
other areas of D-STAR development, including reflectors and linking.
Since the early 2000's, D-STAR has developed into a robust
communications system that utilyzes both radio frequency (RF) and
D-STAR Repeaters in Maine
Cooper Hill, ME
For more information about D-STAR, click on the links below:
Wireless Society of Southern
Maine, P.O. Box 6833, Scarborough, ME 04074