NXDN site roaming for Amateur Use

[Jethro30]

I'm brand new to this forum, but a ham since '92. I've been getting into Kenwood NX-5000 series in a big way the last couple of years, 2 NX-5800's, (one licensed for DMR and one licensed for P25), 1 NX-5700, and now one NX-5300 K, (P25). If I heard my dealer correctly, NXDN, both analog and digital, is native to these radios, P-25 and DMR require additional licensing, and the radios will do NXDN P-25 or NXDN DMR, but not all three together.
Since I retired a year and half ago from Healthcare IT and Telecom, with some Emergency Management and programming and maintaining the Icom IDAS security radio system with that hospital as well, I've been working with a group here who have been doing some P25 and NXDN into analog linked repeater systems. I just recently learned that IDAS and NXDN were developed together and are essentially the same protocol, which is why NXDN looked so familiar to me. Fun stuff. We recently started looking into NXDN site roaming, which is why I'm here.
Any help muddling through this stuff, and any "secret squirrel" stuff would be helpful.
Thanks.

 

[Chris7AA]

NXDN roaming is a multi-site trunked feature. Each site runs a control channel, the sites are tied together over a network, and the subscriber hunts control channels and picks which site to register on based on signal strength and quality. Kenwood documents it under Enhanced Multi-site Trunking.

Amateur NXDN is conventional. One repeater or hotspot at a time, RAN as the access code, and reflectors doing the linking over the internet. I am not aware of any amateur NXDN trunked systems, so in practice there is no control channel to hunt and no site registration, and nothing for a radio to roam between.

Amateur radio's adaptation of NXDN and P25 is built around the common air interface, the over the air waveform and framing, and not necessarily around the network capabilities of each mode.

Worth separating two things that sound alike: linked repeaters are not trunked sites. Several linked repeaters can carry the same audio, but the user still changes channel by hand, and that is not roaming in the NXDN sense.

I compiled notes on roaming and several other commercial features that do not carry over to amateur use here:

DMR, NXDN and P25 features Amateurs just do not use and why | N6JET

Since you are looking at NXDN seriously, one thing you may find interesting. On my own reflector, URFJET, the reflector software is modified to read the RAN out of each incoming NXDN transmission and use it to choose which module you land on, RAN 1 through RAN 26 for modules A through Z. Stock reflector software drops an NXDN operator into one fixed module with no way to move. It was tested on the air across all twenty six modules and every RAN produced a clean module change. Details here:

URFJET — Purpose

I also have a pending project for P25 I call P25-JET. It is a talkgroup selected bridge from P25 reflector 9512 into URFJET, so a P25 operator picks a URFJET module with a talkgroup, 4001 through 4026 for modules A through Z. No transcoder is involved: the two sides meet as plain audio. The reflector is up and listed, the bridge itself is still being built.

N6JET

 

[mmckenna]

NXDN roaming is a multi-site trunked feature. Each site runs a control channel, the sites are tied together over a network, and the subscriber hunts control channels and picks which site to register on based on signal strength and quality. Kenwood documents it under Enhanced Multi-site Trunking.

NXDN can do site roaming in conventional/non-trunked.
The repeaters send out a beacon and the radio will listen for them and choose the one with the strongest RSSI.

 

[Chris7AA]

Fair enough, you are right. I was describing the commercial trunked case and applied it too broadly. I will correct my notes. Thanks.

Either way it does not reach amateur NXDN. Our repeaters and hotspots are MMDVM and send no beacon. Amateur NXDN roaming is not possible.

 

[Chris7AA]

Regarding my previous post: not all amateur NXDN repeaters are MMDVM. There are Kenwood NEXEDGE NXR and Icom IDAS FR machines that would support it.

So the repeater hardware exists. What does not exist is the network. Roaming needs multiple linked sites running beacons, and nobody has built that on amateur bands.

Maybe Jethro30 is considering building one? Also for accessing the roaming feature of the repeater a NEXEDGE radio would be required. It is my understanding that an Anytone AT-D890UV would talk to the repeater but could not utilize roaming.

 

[buddrousa]

We have a County SO near us that has 7 sites all linked each users radio uses the best signal from the beacons and traffic is transmitted on all sites works like Simulcast but each site has a different repeater pair. The system has to be setup correctly not cheap backdoor the system does not work well with latency.

 

[Jethro30]

Thank you all for your reply's. Currently there are two NXDN repeaters intended for this site roaming project and they are not linked at this time, (time restraints), both beacon at this point, I have the closest one in my scan in my NX-5300 and I occasionally see it receiving a short burst. That's how this is intended to be set up. Time restraints with some of us, (who are not retired), makes this a slow process. But, it's ham radio, this is one of several projects going on, but this is the fun one I'm interested in.
This would have been very helpful when I was maintaining the IDAS system for my hospital with a main radio on site and several off-site repeaters at other locations our security dealt with, but our vendor of many years never mentioned it and he eventually just faded away. Oh well ...
So far, this is all Kenwood repeaters and radios running NEXEDGE that we're playing with.
We have a get-together scheduled for a week from this Sat and all the players will be there.
I will be back with more as we develop this project further.
Thanks again, this is very good information.

 

[buddrousa]

Like said they had to do the T1 route to get rid of the Latency. The locals tried to use RF Network links Kenwood came in after that did not work correctly pulled out the RF Radio Links and switched to T1 lines and devices designed for this type setup now it works great no problems.