D-STAR in Amateur Radio Emergency Communications
The use of D-STAR technology for Amateur Radio emergency communications provides a number of benefits augmenting traditional analog FM operations. Clear, crisp, noise-free communication is one of the most significant benefits of D-STAR. The ability to transmit simultaneous text along with voice increases the utility of Amateur Radio in emergency scenarios. Add the ability to link to remote stations via the internet and the capability to transmit high speed multi-media (HSMM) at 128 kbps and the true benefit of D-STAR can be seen. The narrow-band aspect of D-STAR (6.25 Khz) also conserves precious frequency spectrum.
What is D-STAR?
D-STAR, an acronym for Digital Smart Technologies for Amateur Radio, is a digital voice and data protocol developed by the Japanese Amateur Radio League (JARL). D-Star is one of the first on-air packet-based standards to be widely deployed and sold by a major radio manufacturer designed specifically for amateur service use. Presently, Icom is the leader in manufacturing D-STAR equipment but other manufacturers are developing radios for this growing market.
Within D-STAR Digital Voice (DV) protocol standards, voice audio is encoded as a 3600 bps data stream using proprietary AMBE encoding with FEC (Forward Error Correction) and 1200 bps available for text and for an additional data "path" between radios. On air bit rates for DV mode are 4800 bps over the 2m, 70cm and 23cm bands. Advanced Multi-Band Excitation (AMBE) is a proprietary speech coding standard developed by Digital Voice Systems, Inc.
How does it work?
In Digital Voice (DV) mode, a D-Star transceiver employs circuitry that converts voice audio, using proprietary AMBE encoding, to data packets. The packets are transmitted at a rate of 4800 bps, with 3600 bps used for voice and error correction. The remaining 1200 bps are used for synchronization and general use, of which 900 bps are available for transmitting slow-speed text.
Since voice packets and text packets each have a reserved space on the D-Star data stream, they can be sent simultaneously with no interference to each other. This capability has great utility in permitting short text messages to be transmitted while sending voice.
In addition to DV mode, a high-speed Digital Data (DD) mode can be sent at 128 kbps only on the 23cm band. A higher-rate proprietary data protocol is used in 10GHz "link" radios for site-to-site linking.
Radios providing DV data service within the low-speed voice protocol typically use an RS-232 or USB connection for low speed data (1200 bps), while the Icom ID-1 23cm band radio offers a standard Ethernet connection for high speed (128 kbps) connections, to allow easy interfacing with computer equipment.
The D-Star data stream has space reserved for routing information. This data is used to direct signals to specific stations and to route signals through separate ports on different bands as well as internet linking to other repeater systems.
How is D-STAR applicable to emergency communication?
An important 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 instantly send e-mail or Microsoft Word files to someone. The quantity of data sent can be extremely high-volume compared to traditional amateur modes. Voice and even CW are capable of getting a message through, albeit slowly, but D-STAR can place documents, images, and spreadsheets into the hands of those who need them most.
D-RATS is an emerging 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 DPRS function of D-STAR.
During the Great Coastal Gale of 2007 the Washington County ARES group was able to put D-STAR to the test. 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 in Delaware County
Delaware County ARES-RACES operates two D-STAR repeater systems to accommodate emergency communications within the county and region. The N3AEC digital repeater system, designated DelStar East, is located atop Delaware County Memorial Hospital in Drexel Hill. This repeater system was funded by DCMH. A second D-STAR repeater system, W3AEC, designated DelStar West, is located atop the 14-story Fair Acres building in Lima. It was funded by the Pennsylvania Southeastern Counter-terrorism Task Force. Both systems employ identical equipment including a 23cm digital voice (DV) repeater, a 23cm digital data (DD) repeater and 70cm digital voice (DV) repeater. Additionally, Delaware County ARES-RACES employs three tactical communication (TAC-COM) kits that include an Icom ID-1 D-STAR transceiver for 23cm digital voice (DV) and high-speed digital data (DD) capability.
For more information on the two D-STAR repeater systems in Delaware County, check our ARES Repeaters page