Custom version

[pierluigipisanti]

Hi, if I would like to have a custom version, is possible to discuss with you about this ?

Thanks
Peter

[kantooon]

Yes, of course. Do you mean some new feature? I'm open to ideas, as long as they are feasable.

[pierluigipisanti]

Server / client connector simple interface like attached image

and other simple features like.....ANALOG on client and forward to Server that transmit in DMR....like a simple crossband. So I can try to semplify:

My ICOM 2730 Analog radio at home -> limesdr (+your interface) -> internet (VOIP) -> limesdr (+your interface) at your home + your DMR Hytera/Motorola/Others.

So in that case I can talk without any Repeater, and everywhere there is a internet connection ;-)
regards
Peter

[kantooon]

Ok, I think I understand. Part of this is already implemented, for the analog radio transmission and VOIP transit of audio over internet (using the Mumble protocol) so you can already do what you describe with analog radios.

The hard part which is missing currently is a DMR transceiver implemented with the LimeSDR. It is an idea I have played with, and I've read enough of the DMR ETSI standard to understand what would be required software-wise. It is a hard endeavour, not impossible, but requires a lot of time, patience, and especially a very good legal understanding of the legal situation regarding open source implementations of the AMBE codec.

The things which stopped me in the past was the ambiguous situation around the AMBE codec, and the difficulty of implementing TDMA transmissions as required by DMR. There is a free software project which implements a DMR transceiver minus the double slot TDMA transmission, it is called OP25 and it also implemented Yaesu C4FM and D-Star. Without a potential collaboration with this project, it could take a long time to implement DMR from scratch.
Here is a link to the project's home: https://osmocom.org/projects/op25/wiki

I can suggest to also contact them regarding this, see if they would be interested in such a collaboration, and whether the legal aspect is taken care of. If we can raise enough interest in this area, then DMR and othe amateur radio voice protocols can be used like you describe with the LimeSDR.
Myself, right now, am more focused on other digital voice modes which come from a free and open source software area: Codec2 (FreeDV modes) and Opus (custom implementation on qradiolink).

[pierluigipisanti]

Thanks a lot for you clear explanation. At this point some hardware/software like openspot (SharkRF) they should be considered illegal. Very strange...it would be interesting to see how they resolved the legal issues. Thanks a lot...I will continue to follow your interesting project with a lot of curiosity.
Peter

[kantooon]

DMR hotspots are different. They do not have any code to convert digital AMBE frames to audio for playback, or if they have, they use a DVSI chip which is free from any legal issues. But usually they take the AMBE digital voice frames and transmit them unaltered over the internet towards other hotspots (or DMR repeaters). So there is no need for the AMBE codec to be used. Indeed MMDVM which is usually the base for these projects is completely free from legal problems because no AMBE encoding/decoding happens inside. However they also cannot be used without some additional software (and maybe a DVSI AMBE chip) to be able to cross-talk with analog radios.

Given that OP25 can do software encoding/decoding of *MBE voice, perhaps the project's creators found a way around this. Additionally OP25 also uses GNU radio for DSP which makes a potential integration a bit easier.