D-STAR (Digital Smart Technologies for Amateur Radio) is a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses frequency-division multiple access and minimum-shift keying in its packet-based standard. There are newer digital modes (Codec2, for example) that have been adapted for use by amateurs, but D-STAR was the first that was designed specifically for amateur radio.
Several advantages of using digital voice modes are that it uses less bandwidth than older analog voice modes such as amplitude modulation, frequency modulation, and single sideband. The quality of the data received is also better than an analog signal at the same signal strength, as long as the signal is above a minimum threshold and as long as there is no multipath propagation.
D-STAR compatible radios are available for HF, 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, allowing streams of voice or packet data to be routed via amateur radio.
D-STAR compatible radios are manufactured by Icom, Kenwood, and FlexRadio Systems.
In 1998 an investigation into finding a new way of bringing digital technology to amateur radio was started. The process was funded by a ministry of the Japanese government, then called the Ministry of Posts and Telecommunications, and administered by the Japan Amateur Radio League. In 2001, D-STAR was published as the result of the research.
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 440 MHz 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, the card became available and once installed into the radios, it provided D-STAR connectivity. The June 2005 edition of the ARRL’s QST magazine reviewed the Icom IC-V82.
JARL released some changes to the existing D-STAR standard in late 2004. Icom, aware that the changes were coming, delayed the release of their hardware in anticipation of the changes.
The Icom ID-1 1.2 GHz mobile radio was released in late 2004. The ID-1 was the first and only D-STAR radio that provides digital data (DD) mode operation. In this mode, data can be transferred at 128 kbit/s as a wireless bridge via the RJ-45 Ethernet jack on the radios.
The first D-STAR satellite QSO occurred between Michael, N3UC, FM-18 in Haymarket, Virginia and Robin, AA4RC, EM-73 in Atlanta, Georgia while working AMSAT’s AO-27 microsatellite (Miniaturized satellite) in 2007. The two experienced minor difficulty with doppler shift during the QSO.
As of late 2009, there are around 10,800 D-STAR users talking through D-STAR repeaters with Internet connectivity via the G2 Gateway. There are approximately 550 G2 enabled repeaters now active. Note, these numbers do not include users with D-STAR capabilities that are not within range of a repeater, or working through D-STAR repeaters that do not have Internet connectivity.
The first D-STAR capable microsatellite was launched in early 2016. OUFTI-1 is a CubeSat 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 expertise in various aspects of satellite design and operation. The satellite weighs just 1 kilogram and utilize a UHF uplink and a VHF downlink.
In 2015, FlexRadio Systems added D-STAR support to their line of HF transceivers and receivers via a software upgrade. D-STAR support requires the addition of the ThumbDV device from NW Digital Radio.
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 amateurs 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 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.
The current gateway control software rs-rp2c version G2, more commonly called “Gateway 2.0”. Though most Linux distributions should be suitable, the recommended configuration uses CentOS Linux 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 system, 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 G2 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 G2 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 V1 and G2
The main differences between Gateway V1 and V2 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 V1 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 G2 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 V1 control software
The Gateway V1 software was similar to Gateway G2, and utilized Fedora Core 2+ or Red Hat Linux 9+ OS on a Pentium-grade 2.4 GHz or faster machine.
Gateway software developed by Jonathan Naylor, G4KLX, has a larger network of repeaters and users and is being adopted by former Gateway G2 users as the G2 system is closed source, only supports Icom repeaters, and runs on Centos 5.x which will reach end of life in March 2017. ircDDBGateway operates on the ircDDB and QuadNet2 networks.
ircDDBGateway supports Icom controllers and repeaters, as well as homebrew repeaters and hotspots (simplex access points). It provides more linking and routing options over the Gateway V1 and G2.
ircDDBGateway can run on various distributions of Linux and versions of Microsoft Windows. Computer requirements can be as simple as a Raspberry Pi.
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. Dplus software development has an active following, 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.