DMR Network with mobile repeaters...roaming!

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DMR Network with mobile repeaters...roaming!

Postby pat211 » Wed Sep 28, 2016 2:29 pm


Please excuse me if I'm at the wrong place for this, I did not find anything suitable to this question.

Here the case:

We are about to setup a Radio Network with 1 permanent static repeater (RD985S).
We have planned 3 additional repeaters for mobiel use depending on events (mainly sport events that cover over 100s of km).
We planned to use Hytera RD985S repeaters (the first 1 arrived yesterday).

We want the users with their devices (Mobile & Portable) to communicate with other subscribers where ever they are independently on which repeater. The repeaters will be IP connected through the GSM network.

We will use up to 6 groups. We currently have 2 permanent UHF frequencies for Digital (DMR) use. Any additional frequency will be acquired temporarly based on events' needs.

Number of final subscribers starts with 30 onwards and no limit.

The question is:
What is the best use and best practice to avoid subscribers to change channels when they get out of range from a repeater and get into the range of the next repeater. I heard about the roaming function. How does this work? Do I need different frequencies for each repeater to avoid overlapping?
Is it an option (good or bad) to have more than 1 repeater per location? What about XPT & Tier III use in this case, usefull?

I also need to say, that for the 1st repeater the Frequencies will be permanent. For the other 3 repeaters, we will get new temporary frequencies every time we need them for an event. They may be the same, but this is not garanteed.

The system needs to be expendable as much as possible, so we are open to any upgradable solution, reason for the RD985S as this is Tier III compatible.

Thank you in advance for any help and suggestions
Kind regards

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Re: DMR Network with mobile repeaters...roaming!

Postby Metradio » Wed Sep 28, 2016 4:42 pm

Hi Patrick, I think your question needs to be aimed at your radio supplier and your country's radio regulatory authority as most of us are located in the UK and do not have a clue as to what happens in Switzerland..

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Re: DMR Network with mobile repeaters...roaming!

Postby pat211 » Thu Sep 29, 2016 7:46 am

Hello Mike,

Thank you.
This was mostly a general technical question about what would "technically" best to use for my project.

Best regards

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Re: DMR Network with mobile repeaters...roaming!

Postby g4eml » Thu Sep 29, 2016 9:22 am

Hello Patrick,

Roaming is an enhanced form of scanning. A radio set up for roaming has a roam list containing entries for all available repeaters. It scans through this list until it finds a repeater that is above a preset signal level. It then uses this repeater for all transmissions until the signal falls below the preset level, the radio then resumes scanning through the list to find an other repeater with a strong enough signal. Thus if a user moves from the coverage area of one repeater to another it will automatically switch channels.
To enable a radio to scan for repeaters when there is no activity each repeater needs to be set to send a regular beacon signal. This is configured in the repeaters Codeplug.
If a radio needs to transmit but has not heared a suitable repeater recently it will attempt to access all the repeaters in its roam list one after the other. If it is successfull then it uses that repeater for the call.

In an overlapping coverage system each repeater would need to be on a different frequency. However frequencies could be reused if the coverage areas do not overlap. In at case the two repeaters should have different colour codes so the radio is able to tell them apart.

Having temporarily allocated frequencies for each event would be quite a lot of work, every radio would need to be updated each time.


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