Yes an

Yes and the problem the problem gets worse when Yeasu Finally puts its Repeaters on the market, Yet another incompatible system causing more devision in the DV ranks.
Yeasu and Motorola are one but will they be compatible? not on your nelly..
We will have 3 systems and all of them proprietory what a comercial hodge podge.
If Radio Amateurs could have devised a single Non Proprietory system that all amateurs could subscribe to without the guilt of loosing the amateur radios inclusive principle.
The expensive DV dongles and other responses are just eyewash, they just helps the likes of ICOM yeasu etc to up the Anty sorry Price for the HT and mobile rig.
Maybe the codec is the key or 3 codecs, maybe thats the bit Radio Hams should have concentrated attention on...
I am well in favour of DV but but not the total theft of the system which manufacturers are performing

I think the way digital voice should go is to produce an add-on box which plugs into the 6-pin data socket present on most VHF/UHF radios. It would need it's own microphone and speaker socket on the front panel and would need to be controlled and programmed either via a PC or an LCD display (large enough for mobile use!). Most modern radios have a 9,600 baud packet mode built in which gives direct access to the modulation and demodulation stages.

It would ideally run on open-source and hence easily reproducible hardware - something along the lines the existing DV-RPTR boards which are based on a PIC-32. Or, if more computer power is required, something along the lines of the Beaglebone Black (costs £35 +a widely available radio interface).

Yes the CODEC is key. All current amateur digital voice systems to date use proprietary CODECS based on AMBE or it's derivatives that need the chip to do the encoding and decoding (hence the Dongles) - there is a freely available open source codec called CODEC 2 which does everything the commercial ones do but at a lower bit rate and higher audio quality. The differences between the proprietary codecs and the open source ones is the bits they decide to patent as most are based on freely available research!

One thing which is essential is forward error correction - D-Star DV works down rough noise as it is able to piece together the signal from the information it has. The data stream embedded in D-Star doesn't have this correction and will only work with STRONG signals. The ability to use the whole data stream for data when voice isn't present - with the same level of forward error correction would be extremely useful.

The modulation method is equally important, not just from the point of view of on-air performance, but from a compatibility with other systems. D-Star with its GMSK doesn't co-exist with other repeaters in the same way as the 4 level FM used in APCO 25 does, letting the APCO repeaters work on both FM and digital.

I think I have probably summed up the ideal system Hardware, Modulation Method, FEC and CODEC. The next thing is presentation and routing. The callsign based routing on D-Star works well, but I do like the recent add on which gives the ability to dial someone up on DTMF pad and the repeater system finds them - and most of all, the ability to remember where other stations are, even the ones that aren't digital from a DTMF code they use to register on the system and transmit to them in the appropriate format...

Good post Andy you do have a good point, i have NXDN gear and as far as i know the audio quality is the same as trbo, the way i see it, it comes down to cost and as there are lots of mototrbo radios on ebay (without charges nudge nudge wink wink) then thats what they will buy i think.
dealer prices for trbo are less the nxdn so the dealers sell that gear and then that finds its way on to ebay thats why theres no nxdn gear on but lots of trbo.

Motorola only has the commercial Yeasu gear, Ham yeasu is Yeasu.

May be some on will develope an open source, public domain system that can co-operate with either TRBO or D-Star
or both then we can believe that DV is an Amateur Radio option not just a way to bolster Icom / Yeasu profits
or maybe no one has noticed that Icom/Yeasu pricing doubles the cost when we go digital, Lets get the Amateur bands back from these Pirate companies.

Mototrbo and nexedge are open source

The first task is to break the system down into layers... (using the ISO Open Systems Interconnection model)

Physical - The point to point data link using whatever modulation method (GMSK, 4FM etc.)
Data Link - The means of making this reliable, forward error correction etc.
Network - The addressing or routing (translating callsigns to IP addresses)
Transport - The means of delivering the data stream to the appropriate repeater (UDP)
Session - Communications between nodes (keeping Callsign lists up to date)
Presentation - The encoding and decoding of digital voice
Application - The presentation of data via the radio's display / PC Software (talk groups / reflectors etc.)

The concept being that each layer on one system talks to the corresponding layer in the other via the layers below it - by conversion to an intermediate format which preserves the data itself and metadata (data describing the data) and then into the appropriate format at the other end...

A lot of work!

Yes I take your point, this is all done in software, who does all the work? a few committed amateurs /software writers mostly open source.
Who locks us in and blows the whole open source principle? in D-Star its Icom with some sort of control via a codec chip. The dvnode and dvap conspiracy help to keep the prices sky high, my bet it will all happen again with Mototrbo and nexedge and whatever Yeasu conspires , Amateurs need to set the standards before manufactures own them all...

I wonder if we implemented the Presentation layer in software and made it compatible with D-star would we be sanctioned by the Ambe codec patents. I hear the Peter Martinez G3PLX had some problems with his recent software Codec!
Maybe Icom would implement the open source Software Codec in all future D-Star production hi hi, we can live in hope
It would be Icom supporting the Amateur fraternity a nice reward for their customers loyalty.

It would be theoretically possible to implement D-Star using another audio CODEC - except the current system doesn't have any provision for a data-only QSO and hence slotting in another CODEC without conflicts will always be impossible.

However, it would be nice to use the existing infrastructure and repeaters...

See http://www.rowetel.com/blog/?page_id=452 and http://codec2.org/

Andy

Many Thanks for the links above, Its all very interesting, I have spent a few hours browsing and following. The preference for more open source is stronger than I thought, Sounds like the way to go.
I do not think provision of data link will be a problem, looks like its under consideration already, even adding a PSK channel sounds viable, Peter Martinez is mentioned hope he gets involved with the MoDem implementation

Thanks Again

Ron