D-STAR (Digital Smart Technologies for Amateur Radio) is a digital voice and data protocol specification developed as the result of research by the Japan Amateur Radio League to investigate digital technologies for amateur radio. While there are other digital on-air technologies being used by amateurs that have come from other services, D-Star is one of the first on-air and packet-based standards to be widely deployed and sold by a major radio manufacturer that is designed specifically for amateur service use.
Other non-digital voice modes such as amplitude modulation, frequency modulation, and single sideband have been widely used since the first half of the 20th century. By comparison, digital D-STAR signals offer clearer signals and use less bandwidth than their non-digital counterparts. As long as the signal strength is above a minimum threshold, and no multi-path is occurring, the quality of the data received is better than an analog signal at the same strength.
D-Star compatible radios are available on VHF, UHF, and microwave amateur radio bands. In addition to the over-the-air protocol, D-Star also provides specifications for network connectivity, enabling D-Star radios to be connected to the Internet or other networks and provisions for routing data streams of voice or packet data via amateur radio callsigns.
The first manufacturer to offer D-Star compatible radios is Icom. As of December 30, 2008, no other amateur radio equipment manufacturer has chosen to include D-Star technology in their radios. Kenwood re-brands an Icom radio and distributes it in Japan only.
In 1999 an investigation was put into finding a new way of bringing digital technology to amateur radio. The process was funded by the Japanese government and administered by the Japan Amateur Radio League. In 2001, D-Star was published as the result of the research and Icom entered the construction of the new digital technology by offering the hardware necessary to create this technology.
In September 2003 Icom named Matt Yellen, KB7TSE (now K7DN), to lead its US D-Star development program.
Starting in April 2004 Icom began releasing new "D-Star optional" hardware. The first to be released commercially was a 2-meter mobile unit designated IC-2200H. Icom followed up with 2 meter and 440Mhz handheld transceivers the next year. However, the yet to be released UT-118 add-on card was required for these radios to operate in D-Star mode. Eventually Icom began selling the card and once installed into the radios it provided D-Star connectivity for each of the transceivers. The June 2005 edition of the ARRL's QST magazine reviewed the Icom IC-V82.
JARL released significant changes to the existing D-Star standard in late 2004. Icom, aware that the changes were coming, had placed the release of their hardware on hold for a period of as much as a year while they awaited the changes. As soon as the changes were out, Icom announced they would be able to finish up and release equipment.
The Icom ID-1 1.2 GHz mobile radio was released in late 2004. This was to have been the first D-Star radio, providing full Digital Data (DD) functionality.
The first D-Star over satellite QSO occurred between Michael, N3UC, FM-18 in Haymarket, Virginia and Robin, AA4RC, EM-73 in Atlanta, while working AMSAT's AO-27 microsatellite (Miniaturized satellite) in 2007. The two operators used a variety of Icom gear to make the contact and experienced slight difficulty with doppler shift during the QSO.
As of late 2009 there are around 10,800 D-Star users talking through D-Star repeaters which have connectivity to the Internet via the G2 Gateway. There are around 550 G2 enabled repeaters now active. Note, these numbers do not include the scores of users with D-Star capabilities but not within range of a repeater, or working through D-Star repeaters that do not have Internet connectivity.
The first D-Star capable microsatellite is scheduled for launch during October 2010. OUFTI-1 is a CubeSat and is built by Belgian students at the University of Liège and I.S.I.L (Haute École de la Province de Liège). The name is an acronym for Orbital Utility For Telecommunication Innovation. The goal of the project is to develop experience in the different aspects of satellite design and operation. The satellite weighs just 1 kilogram and will utilize a UHF uplink and a VHF downlink.
The system today is capable of linking repeaters together locally and through the Internet utilizing callsigns for routing of traffic. Servers are linked via TCP/IP utilizing proprietary "gateway" software, available from Icom. This allows amateur radio operators to talk to any other amateur participating in a particular gateway "trust" environment. The current master gateway in the United States is operated by the K5TIT group in Texas, who were the first to install a D-Star repeater system in the U.S.
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 is valuable to allow emergency communications oriented networks to continue to link in the event of internet access failure or overload.
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 DV mode, a high speed Digital Data (DD) mode can be sent at 128 kbit/s only on the 23 cm band. A higher-rate proprietary 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.
The current gateway control software rs-rp2c version 2.0, more commonly called "Gateway 2.0", runs on virtually any distribution of Linux, but the Icom-supported and -recommended configuration is CentOS 5.1 on a Pentium IV 2.4 GHz or faster machine.
The recommended configuration uses Linux CentOS 5.1 with the latest updates, typically running (kernel 2.4.20. glibc 2.3.2 and BIND 9.2.1 or later). The CPU should be 2.4 GHz or faster and the memory should at least be 512 MB or greater. There should be two network interface cards and at least 10 GB free of hard drive space which includes the OS install. Finally for middleware, Apache 2.0.59, Tomcat 5.5.20, mod_jk2 2.0.4, OpenSSL 0.9.8d, Java SE 5.0 and postgreSQL 8.2.3 are utilized, but these can be different as updates occur.
Along with the open-source tools, the Icom proprietary dsipsvd or "D-Star IP Service Daemon" and a variety of crontab entries utilize a mixture of the local PostgreSQL and BIND servers to look up callsigns and "pcname" fields (stored in BIND) which are mapped to individual 10.x.x.x internal-only addresses for routing of both voice and data traffic between participating gateways.
During installation, the Gateway 2.0 software installation script builds most of the Web-based open-source tools from source for standardization purposes, while utilizing some of the packages of the host Linux OS, thus making CentOS 5.1 the common way to deploy a system, to keep incompatibilities from occurring in both package versions and configuration.
Additionally, gateways operating on the U.S. trust server are asked during initial setup to install DStarMonitor which is an add-on tool that allows the overall system administrators to see the status of each Gateway's local clock and other processes and PIDs needed for normal system operation, and also sends traffic and other data to servers operated under the domain name of "dstarusers.org". By this means a complete tracking of user behaviour is technically possible. Installation of this software also includes JavaAPRSd, a Java-based APRS interface which is utilized on Gateway 2.0 systems to interface between the Icom/D-Star GPS tracking system called DPRS to the more widely known and utilized amateur radio APRS system.
How Gateway 2.0 works
Each participating amateur station wanting to use repeaters/gateways attached to a particular trust server domain must "register" with a gateway as their "home" system, which also populates their information into the trust server—a specialized central gateway system—which allows for lookups across a particular trust server domain. Only one "registration" per trust domain is required. Each amateur is set aside eight 10.x.x.x internal IP addresses for use with their callsign or radios, and various naming conventions are available to utilize these addresses if needed for specialized callsign routing. Most amateurs will need only a handful of these "registered" IP addresses, because the system maps these to callsigns, and the callsign can be entered into multiple radios.
The gateway machine controls two network interface controllers, the "external" one being on a real 10.x.x.x network behind a router. A router that can perform network address translation on a single public IP address (can be static or dynamic in Gateway 2.0 systems) to a full 10.x.x.x/8 network is required. From there, the Gateway has another NIC connected directly to the D-Star repeater controller via 10BaseT and the typical configuration is a 172.16.x.x (/24) pair of addresses between the gateway and the controller.
Differences between Gateway 1.0 and 2.0
The main differences between Gateway 1.0 and 2.0 are the addition of a relational database (PostgreSQL) for more flexibility and control of updates, versus the previous use of only BIND for "database" activities, the addition of both an administrative and end-user Web interface for registration which was previously handled via command-line commands by the Gateway 1.0 system administrators, dropping the requirement for static public IP addresses for gateways, and the ability of the software to use a fully qualified domain name to find and communicate with the trust server, allowing for redundancy/failover options for the trust server administrators. Finally, a feature called "multicast" has been added for administrators to be able to provide users with a special "name" they can route calls to which will send their transmissions to up to ten other D-Star repeaters at the same time. With cooperation between administrators a "multicast group" can be created for multiple repeater networks or other events.
Another additional feature of Gateway 2.0 is the ability to use callsign "suffixes" appended to the user's callsign in a similar fashion to the repeaters and gateways in the original system, which allow for direct routing to a particular user's radio or between two user radios with the same base callsign, by utilizing the 8th most significant field of the callsign and adding a letter to that location, both in the gateway registration process on the web interface, and in the radios themselves.
Gateway 1.0 control software
The Gateway 1.0 software was similar to Gateway 2.0, and utilized Fedora Core 2+ or Red Hat Linux 9+ OS on a Pentium-grade 2.4 GHz or faster machine.
Various projects exist for gateway administrators to add "add-on" software to their gateways, including the most popular package called "dplus" created by Robin Cutshaw AA4RC. A large number of Gateway 2.0 systems are offering services added by this software package to their end-users, and users are getting used to having these features. Features include the ability to link systems directly, "voice mail" (a single inbox today), ability to play/record audio to and from the repeaters connected to the Gateway and the most important, the ability for DV-Dongle users to communicate from the Internet to the radio users on the repeaters.
There is often a misconception by users and system administrators alike that the Gateway 2.0 systems have these add-on features from dplus by default, a testament to the popularity of this add-on software. Software development on dplus is very active right now, and features such as multiple repeater/system connections similar to the type of linking done by other popular repeater-linking systems (IRLP and EchoLink) are being worked on.
Another aspect of D-STAR technology is its ability to send large quantities of data to emergency responders in the event of a disaster. Served agencies can relate to sending e-mail or Microsoft Word files to someone. The quantity of data sent can be high-volume compared to traditional amateur modes. Voice and even CW are capable of getting a message through albeit slowly, but D-STAR can transfer documents, images, and spreadsheets in reasonable time periods.
D-RATS is a D-STAR communications tool that supports text chat, TCP/IP forwarding, file transfers, and can act as an e-mail gateway. There is also the ability to map user's positions using the D’PRS function of D-STAR. The application is written in Python/GTK and is cross-platform It runs on Windows, Mac OS X, and Linux. The application was developed by Dan Smith (KK7DS) for the Washington County Amateur Radio Emergency Service in Oregon.
During the Great Coastal Gale of 2007 the Washington County ARES group was able to test D-STAR. The event was made up of several strong Pacific storms that interrupted conventional communication systems. Emergency traffic for the American Red Cross and the Vernonia, Oregon Fire Department was handled by the group using FM voice because the group had no D-STAR repeater equipment available. The D*Chat communication tool was also used to send small text transmissions via simplex during this event at distances of up to seventeen miles.
An ability for amateurs to send files during this weather event would have greatly increased the capacity for ARES to help during the emergency. Although D*Chat was a useful means of communication D-RATS was developed to help fill the gaps that may have been lacking.
Another improvement over D*Chat that D-RATS provides is form support. Users can set up frequently used forms well before they're necessary and when the need comes all that's required is to fill in the fields. In this way, for example, emergency forms from the Red Cross, National Traffic System, or the Incident Command System, such as the FEMA standard ICS-213, can be generated and quickly sent.
D-STAR uses a patented, closed-source proprietary voice codec (AMBE). Hams do not have access to the detailed specification of this codec or the rights to implement it on their own without buying a licensed product. Hams have a long tradition of building, improving upon and experimenting with their own 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. Even critics praise the openness of the rest of the D-STAR standard which can be implemented freely. An open-source replacement for the AMBE codec would resolve this issue.
Bruce Perens, K6BP, amateur radio and open source advocate, evangelized the need for an open source codec for amateur radio. David Rowe, VK5DGR, has implemented an Alpha-test replacement codec under the LGPL and is continuing in its development.
- Trademarked name
Despite many protestations from the Pro-D-Star lobby that the standard was developed by the JARL, and D-Star is not only an Icom system, the term 'D-Star' is itself a registered trademark of Icom.
- Usable range compared to FM
D-STAR has comparable usable range to FM but degrades differently. While the quality of FM progressively degrades the further a user moves away from the source, D-Star maintains a constant voice quality up to a point, then essentially "falls off a cliff". This behavior is inherent in any digital data system, and demonstrates the threshold at which the signal is no longer correctable.
D-STAR does add to the cost of a radio and is a barrier to the adoption of the technology. In 2006 the cost of a D-STAR radio was compared to that of a standard analog radio and the price difference was nearly double. This is due partly to the per-unit cost for the voice codec hardware and/or license, and partly to manufacturer research and development costs that need to be amortized. As is the case with any product, as more units are sold the R&D portion of the cost will decrease over time. The D-Star capable radios also cost most than their equivalents from other brands, even before the D-Star options boards are added (in the UK as of December 2010, Martin Lynch & Sons' website lists the Icom 2820 at £479.99, while the equivalent Yaesu, the FT8800, is listed at just £329.94).
- Other available digital standards
Amateur radio operators have been using the more widely available Project 25 (P25) standard for some time and that digital mode offers features that are comparable to DSTAR. P25 was developed by the Association of Public-Safety Communications Officials-International for use by federal, state/province and local public safety agencies, and has been around since 1995. The P25 suite of standards is firmly established and has proven itself in multiple public service agencies. Equipment is available from multiple manufacturers rather than from just one with DSTAR. Another drawback is P25 is not manufactured for amateur use and commercial grade equipment must be used, and the cost of commercial radios that employ the P25 technology were even more expensive than that of off-the-shelf D-STAR radios. As of 2008 new entry level P25 radios were available at a cost ranging from $900 to $1500. In addition, there are small pockets of amateurs in Europe experimenting with TETRA on the 70cms band.
- Questionable legalty
Many anti D-Star amateurs have argued that the proprietary codec constitutes a form of encryption, which is prohibited by almost every country's amateur radio licence conditions. For the most part, regulators have ignored these claims, and allowed unbridled D-Star use as with any other mode. However, the French regulators, in April 2010, have issued a statement that rules D-Star illegal in France, due to the ability to create a connection to the internet with it, and because the codec used is proprietary. The French Amateur Radio society, Réseau des Émetteurs Français have an online petition against this ruling, calling for the government to allow the mode as to ban it would deny them 'fundamental rights'
A non-Icom D-Star repeater
The world's first non-Icom D-Star repeater GB7MH, fully linked to the K5TIT G2 network and D-Plus, went live on 10 September 2009, in West Sussex, England. Whilst waiting for the DSL line installation, the repeater is connected to the Internet via a 3G dongle from network operator "Three". The system is built around Satoshi Yasuda's GMSK Node Adapter, a Mini-ITX system running CentOS 4, a Tait T800 repeater and G2 code written by G4ULF. All the usual G2 features such as callsign routing, D-Plus linkage and DPRS via D-Star Monitor are supported.
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