A few thoughts on D-Star

January 2, 2011 | Amateur Radio | By: Mark VandeWettering

Some chatting on the #hamradio IRC channel on irc.freenode.net have made me think about D-Star a bit more, and I thought I’d write them down to see what other people thought.

If you don’t know what D-Star is, it’s a digital voice and data technology for amateur radio which can currently be found in radios manufactured by Icom. The Wikipedia page will fill in a few additional details. I’m going to presume that you already know a bit about D-Star, so if you don’t, go ahead and click the link.

A lot of people have what I consider to be unreasonable criticisms of D-Star. Of course, whether they are unreasonable is actually a matter of perspective, so you might disagree. Bitching about the trademarked name is pretty unreasonable from my perspective. Complaining about the “brick wall” of digital performance (either the message gets through and sounds perfect, or it fails utterly) is something I think of as unreasonable: all modes have tradeoffs. Arguing that P25 might be a better choice is rather silly, because P25 equipment is horrifically expensive compared to D-Star radios. And I especially think that complaining that D-Star radios are expensive is unreasonable (with some caveats below).

The single biggest reason that we should all be cautious about wide adoption of D-Star is that it relies on a patented digital voice codec. This is bad on multiple fronts. First of all, the DV (digital voice) protocol that the D-Star network uses to send voice data has no way to select alternative codecs (there is simply no place in the protocol to specify an alternative). This means that every investment in D-Star radios locks us into a product which is unavailable to amateurs for any other use. We can’t legally write a compatible codec to work with voice data on the D-Star network, nor can we substitute a freely available voice codec and carry that traffic on the D-Star network. What we’ve essentially done is guarantee that we’ll be sending $20 or so to the patent holder for every D-Star radio. That doesn’t really sound all that crazy, but there are further problems. As a practical matter, if this company (say) went out of business, we’d have no legal recourse to get new equipment which would inter-operate with our existing investment in D-Star (at least until the patent expires). The current patent holder could just flat out decide to not manufacture the chips anymore, and we’d have lost our investment in D-Star radios.

Think it can’t happen? What’s the average lifespan of a technology company?

But let’s suppose that I am being unreasonable. Maybe DVSI (the patent holders) and Icom (the current single source of radios employing D-Star) are good companies that will continue to sell products at reasonable prices. Isn’t D-Star a good choice then?

I’d submit the answer is still no, and here’s the reason. Since AMBE is currently patented, we are unable to make our own implementations of the digital voice component of D-Star. If we could do that, a whole raft of interesting applications could be created. We could fully integrate D-Star with other VOIP technologies currently in use on amateur radio such as IRLP and Echolink. We could provide free, open source software to send D-Star traffic over the D-Star network, just as we can now for Echolink. We could adapt the technology for links aboard satellites, where the harsh environment may make the chips which currently implement AMBE an unwise choice for use in space.

Our investment in D-Star doesn’t provide us with any of that. In fact, investment in D-Star pretty much precludes any of that.

D-Star does have one huge advantage: it is available today at your local radio store. You go down, you plunk down your money and you can get an HT which provides you all the advantages of digital voice. All of my criticisms aside, I haven’t really got an alternative. In fact, I don’t even know when the alternative will be available.

David Rowe is currently working on an unpatented codec for low rate speech. He thinks he can get a good sounding voice codec running at less than 2400bps, and his early results are promising enough to make me believe him. Surf on over to see what it currently sounds like. Once we have this up and running, I think there will be a whole host of interesting applications that could be developed for digital voice on HF and up. If there is a project that I think needs the help of the amateur radio community, this is it!

The program WinDRM is a program which implements digital voice over HF frequencies (and higher) using COFDM. It uses the LPC-10 codec at 2400bps (which sounds pretty robotic, but is in the public domain) and Speex (which similarly is a bit rough at only 2400bps). It is sadly Windows only, and not open source.

Ditto for FDMDV. Uses LPC-10, and appears to be Windows only, and not open source. It also hasn’t been updated in two years.

I think we need an open source digital voice project using Codec2. I think that in the long run, this kind of experimentation is vital to amateur radio, and will provide a greater lasting benefit than saddling ourselves with single source digital voice appliance.

What do you all think?

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Comments

Comment from Eric Smith
Time 1/2/2011 at 8:39 pm

The AMBE CODEC isn’t just patented, it’s also undocumented. That makes use of D-STAR on Amateur Radio a violation of FCC regulations, specifically 97.113(a)(4) “messages encoded for the purpose of obscuring their meaning”.

If someone transmits a message over amateur radio using D-STAR, there is no way I can decode it. For all other amateur radio modes, I can build my own radio, decoder and/or software. Not so with D-STAR.

If use of D-STAR on amateur radio doesn’t violate FCC regs, then I should be able to come up with any secret code I want to, and use it over amateur radio, and argue to the FCC that I’m not intending to obscure the meaning of the messages and will happily sell a radio using my secret code to anyone that is willing to pay me $10M.

Comment from Mark VandeWettering
Time 1/2/2011 at 9:41 pm

I don’t disagree, Eric, but the FCC hasn’t acted against PACTOR either, despite a nearly identical situation: patented, single source, undocumented protocol.

Comment from Andrew M1DNS
Time 1/3/2011 at 5:43 am

JUST A COUPLE OF POINTERS ON D-STAR, THE CODEC HAD TO BE A TRUSTED SOURCE TO ALLOW A WORLDWIDE PROGRAMME LIKE THIS TOO GET OFF THE GROUND. THE D-STAR RADIOS ARE A TAD MORE EXPENSIVE, BUT ISN’T ALL EQUIPMENT BASED ON NEW TECHNOLOGY? THE COST ISN’T ALL THAT GREAT WHEN YOU THINK YOU’RE GETTING A DUAL MODE RIG – ANALOGUE / D-STAR WITH THE ABILITY TO SEND DATA (TEXT MESSAGE AND WITH GPS / APRS (DPRS) ABILITIES BUILT IN ) IF YOU COMPARE IT TOO A D710 OR A FT350M IT’S NOT THAT EXPENSIVE.

THE IDEA OF LINKING THE D-STAR NETWORK TO OTHER VOIP SYSTEMS, IS ALREADY HERE…. MANY IRLP NODES ARE INTERFACED TO A D-STAR REFLECTOR- XRF005, A FAIRLY EASY TASK TO DO. HOWEVER A LOT OF D-STAR USERS, OPPOSE THIS IDEA AS IT DOWN GRADES THE D-STAR AUDIO, THE WHOLE IDEA IS TO HAVE DIGITAL GRADE AUDIO, NOT INTERSPERSE IT WITH BEEPS, BOPS AND CRACKLES FROM ANALOGUE AUDIO, AND THEREFORE ONLY A FEW OF THE MANY REFLECTORS ALLOW ANALOGUE TO D-STAR BRIDGING.

THERE IS AN ALTERNATIVE TO USING ICOM D-STAR, I AND MANY OTHER RUN D-STAR REPEATERS BUILT USING PC SOFTWARE AND A COUPLE OF ANALOGUE RADIOS, WE ALSO RUN RF GATEWAYS TO THE D-STAR NETWORK USING ANALOGUE RADIOS. IT IS POSSIBLE TO INTERFACE YOU’RE PC & A DV DONGLE TO YOUR 9K6 COMPATIBLE ANALOGUE RADIO AND WORK D-STAR VIA RF (NOT JUST VIA THE INTERNET)

FOR MORE INFO, CHECK OUT THESE GROUPS….
http://groups.yahoo.com/group/pcrepeatercontroller/
http://groups.yahoo.com/group/dstar_development/
http://groups.yahoo.com/group/gmsk_dv_node/
http://groups.yahoo.com/group/ircDDBGateway/
http://groups.yahoo.com/group/ircddb/
http://www.va3uv.com/freestar.htm

ANDREW M1DNS.

Comment from Christopher J. Pilkington N2MCS
Time 1/5/2011 at 2:56 pm

Mark, I couldn’t agree with you more. I had purchased a D-Star rig and a Not Quite So Mini Hot Spot board to make my own D-Star gateway. Ultimately, I did not use much the D-Star features (like end-user to end-user selective calling), mostly I just connected to conference nodes as I would with Echolink. I have since sold my D-Star HT to someone using it for EmComm. (Apparently the D-Star walled garden is a selling point to certain “Emergency Communicators.”)

@Andrew: I don’t know what you mean by the CODEC having to be a trusted source. Icom still to this day is the sole supplier of manufactured D-Star radios. Had they picked any other CODEC, this would not have changed the situation. Hobbyists would have still had to be compatible with xyz CODEC.

Ultimately, why JARL (and therefore Icom) chose AMBE was that there weren’t any other viable options for a narrowband digital codec when D-Star rolled out, save IMBE, produced by the same vendor, DVSI.

Sure there are many hobbyist attempts at opening the D-Star system. But all of them fall short of an alternative implementation of the CODEC, because the CODEC is closed-source and proprietary.

Comment from James
Time 1/9/2011 at 9:23 pm

@andrew, typing in all caps is considered extremely rude on the Internet. It’s akin to yelling. The issue with the codec isn’t hugely due to the price. There are issues that were covered in this very blog post. You shouldn’t need a DV dongle to do something that your computer has more than enough horsepower to do on it’s own. The codec should be available as a codec.c that you can add to your own programs.

73s
James
N9XLC

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