Towards open-source infrastructure for DMR repost from OpenDV


Steve N4IRS
 

DMR, after D-Star, is the most political of the digtial voice modes. Unlike the other modes, most DMR systems connect to a centralised server, known as a "master" and that is responsible for all of the talk group routine, personal calls, and position data interpretation and forwarding. There are three main centralised systems: BrandMeister, DMR+ (known as Phoenix in the UK), and TGIF.
 
What these systems have in common is that they are closed source. This is not good for the amateur community. There were mutterings about them having signed NDAs with Hytera and Motorola to get details of their internet connection protocols, which may or may not be true. Even if true, why not make the non-NDA parts of the source code open?
 
In the commercial world, digital voice repeaters, be they for DMR, P25, NXDN, or dPMR have limited abilities within themselves for call routing. They do include CPUs of course, but for anything other than simple point-to-point links, they are useless. This limitation is fine for what they were originally designed for, small centrally controlled networks, with or without a dispatching console function. The YCS system for System Fusion is looking to do the same for YSF and that is why I oppose it.
 
This model of a centralised control structure carried through to the amateur DMR networks. In its simplest form, a repeater would simply have a point-to-point network connection to the master and things would be fine. Even with a semi-distributed system, with one or more master per country, there is still some central control of the system with the power to overrule the decisions made at the local level. Such central control is also not conducive to supporting each countries requirements, and leads to much used functionality being arbitrarily removed. In the extereme case the countries master may also be removed. When such things happen you have to ask from where did they derive their authority? Who voted for them? Who made the decision and how do they know that it is correct?
 
In the amateur world we have gone beyond having dumb repeaters. Most MMDVM systems for example have a Raspberry Pi or similar running the system, and have the potential to provide a lot of local processing power which can be used for more complex tasks than simply routing traffic over a point-to-point link. Many sysops expressed the wish to be able to have access to multiple masters, simultaneously, and hence the DMR Gateway was born in 2017. It does complex call routing, and almost everything else, bar the position data interpretation.
 
In some quarters this development was opposed. I believe that the sysop should have the choice on how to route their traffic and so development went ahead and it has been enhanced since. It has been a huge success.
 
I think that the time has come to look at having an open source, non-centralised, DMR network. A network where no one person or group has control. We already have the beginnings of this with the HBLink and with XLX projects. If more people get involved with these projects then they will grow and offer more features as time goes on.
 
Some may say, what about integration of commercial repeaters like Hyteras and Motorolas? There is already a program available that converts the Hytera repeater protocol to the protocol used by the MMDVM, and integration of Motorola repeaters is possible all be it with a number of programs in series. Maybe someone will rationalise this into something simpler.
 
Things are already moving on this, and I hope that in the future we will see such systems appear and then DMR will be free of the tyranny of what we have now. Sysops and their users are sovereign and should not be dictated to by anybody (the same goes for software developers :-) ).
 
Jonathan  G4KLX
 

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