Site Trunking

[troymail]

Really wanted to ask this in a P25 forum/thread but didn't see one...

Questions regarding site trunking mode -- saw a VIPER site go into site trunking mode today following a heavy thunderstorm. The first indication was my Unication G4 telling me the site was in site trunking mode and I was hearing no activity (county and the area around the site was very busy with lightning strikes an structure fires).

I plugged in Pro96Com and it confirmed site trunking mode.

I was seeing a few units affiliated with the failed site but there was no voice activity or other frequencies in user other than seeing the primary and alternate control channel frequencies and the callsign frequency.

This made me curious -- in site trunking mode, do subscriber radios "avoid" that site? What about the few radios I was seeing affiliated?

 

[RFI-EMI-GUY]

Really wanted to ask this in a P5 forum/thread but didn't see one...

Questions regarding site trunking mode -- saw a VIPER site go into site trunking mode today following a heavy thunderstorm. The first indication was my Unication G4 telling me the site was in site trunking mode and I was hearing no activity (county and the area around the site was very busy with lightning strikes an structure fires).

I plugged in Pro96Com and it confirmed site trunking mode.

I was seeing a few units affiliated with the failed site but there was no voice activity or other frequencies in user other than seeing the primary and alternate control channel frequencies and the callsign frequency.

This made me curious -- in site trunking mode, do subscriber radios "avoid" that site? What about the few radios I was seeing affiliated?

Those radios are programmed with that tower as a critical site. They might belong to an agency that has specific coverage needs that site alone can provide. For example a prison might need indoor coverage and that is the only site that can provide it. The radios will tend to stick to that site unless it is totally off the air.

Sent from my SM-T350 using Tapatalk

 

[GTR8000]

This made me curious -- in site trunking mode, do subscriber radios "avoid" that site?

Generally speaking, yes. If a subscriber comes across a site that is in site trunking mode, they should try to find another site that is in wide area mode.

What about the few radios I was seeing affiliated?

Two most common reasons:

• After being powered back up, the subscriber registers with the last site it was active on, which happens to be the site that is now in site trunking. The radio should at this point hunt for an alternative site that is in wide area mode.
• The personality for the talkgroup the radio is affiliating with is setup to have a preference for a particular site. This can either be "preferred", where it will use that site unless it's in site trunking mode, or "always", where it will use that site irrespective of the fact that it might be in site trunking mode.

The key is whether or not you saw those subscribers quickly de-register, or whether they seemed to hang around. If they registered, affiliated, then de-registered, they likely went off to look for a wide area site. If they lingered, then they may've been setup to always prefer that site, i.e. they were essentially strapped to that particular site/talkgroup combination in the personality.

 

[GTR8000]

Really wanted to ask this in a P25 forum/thread but didn't see one...

The System Administration and Maintenance forum is probably best suited for these types of technical questions.

https://forums.radioreference.com/system-administration-maintenance/

 

[troymail]

Thinking more about the affiliations, I suspect it could be one or more of the above offered situations. Further, I know from experience that Pro96Com sometimes detects affiliations of radios but misses UNaffiliations (probably because it's not perfect reception/decoding - not because of Pro96Com).

There was alot of activity in the area of this site during this observation yesterday. I need to get my radio IDs loaded into Pro96Com in case this happens again.

I believe this failed site was an "add" to the system when this county went onto the system due to poor coverage. It seems the site is critical for some users (structural firefighting at a minimum) and even on a good day, I hear indications of poor coverage. One fire company in the area (had 3 possible structure fire dispatches during/after the storm) still seems to use their VHF frequency/repeater for fireground operations -- this seems to prove why they need to do that.

The System Administration and Maintenance forum is probably best suited for these types of technical questions.

https://forums.radioreference.com/system-administration-maintenance/

Ok - wouldn't even have considered that one. I scrolled through looking for an area that made sense/matched the question. Some things just don't have an obvious place.

 

[GTR8000]

Thinking more about the affiliations, I suspect it could be one or more of the above offered situations. Further, I know from experience that Pro96Com sometimes detects affiliations of radios but misses UNaffiliations (probably because it's not perfect reception/decoding - not because of Pro96Com).

Actually I should've given my answer more thought. If the subscriber is already registered on the system, and it decides to switch to another site, there would be no indication of such broadcast over the control channel of the site it's leaving. The subscriber would simply affiliate with the talkgroup on the new site. The message you might see on the old site is if the radio were turned off, in which case it would de-register.

Just for the sake of clarity, when a subscriber is turned on, it first registers (logs on) the system, then it affiliates with a talkgroup. If the subscriber changes talkgroups, it simply affiliates with the newly chosen talkgroup, there is no de-affiliation message broadcast. When the radio is turned off, it de-registers (logs off). In certain cases you won't see a de-registration message, such as an abrupt loss of power caused by removing the radio's power source before it can be gracefully powered down. The very last thing a subscriber does after the power knob/button is turned off is to send a de-registration ISP.

It seems the site is critical for some users (structural firefighting at a minimum) and even on a good day, I hear indications of poor coverage. One fire company in the area (had 3 possible structure fire dispatches during/after the storm) still seems to use their VHF frequency/repeater for fireground operations -- this seems to prove why they need to do that.

Which is exactly why fireground operations, especially interior ops, should be on a simplex frequency. Using digital trunking for interior ops is just about the worst decision a department can make. But, that's a whole other discussion that we probably shouldn't rehash.

 

[troymail]

Looks like the failed site is completely offline now... I assume they are working on it....

 

[mikey60]

Actually I should've given my answer more thought. If the subscriber is already registered on the system, and it decides to switch to another site, there would be no indication of such broadcast over the control channel of the site it's leaving. The subscriber would simply affiliate with the talkgroup on the new site. The message you might see on the old site is if the radio were turned off, in which case it would de-register.

This is actually incorrect. The adjacent site broadcast information on all other sites that are neighbors of the site in question would broadcast that the site is disconnected. The site is still advertised as a neighbor, but there is an indication that the site is not connected to the system there. There are cases where the site may still be shown as active, but those are rare from what I've seen.

On the site itself, there is an indication that it's operating in site trunking mode, and would still list neighbor sites (in most cases at least) but would indicate that the information about control channel and status is stale information (has not been updated in some period of time).

Mike

 

[KevinC]

One more thing to add (and this is for Motorola subscribers, no idea on others)...

The subscriber will chose coverage over site trunking. Meaning that if no other site is above "poor" it will stay on the site trunking site.

 

[GTR8000]

This is actually incorrect. The adjacent site broadcast information on all other sites that are neighbors of the site in question would broadcast that the site is disconnected. The site is still advertised as a neighbor, but there is an indication that the site is not connected to the system there. There are cases where the site may still be shown as active, but those are rare from what I've seen.

On the site itself, there is an indication that it's operating in site trunking mode, and would still list neighbor sites (in most cases at least) but would indicate that the information about control channel and status is stale information (has not been updated in some period of time).

Mike

I think you misunderstood my post. I never mentioned adjacent site broadcasts. I was talking about the fact that if a radio leaves one site for another site, there's not going to be any OSP on the site being left indicating that the radio itself has left. It simply switches sites and would "pop up" on the newly chosen site.

Not sure what made you thing that I was talking about adjacent site broadcasts.

 

[slicerwizard]

This is actually incorrect.

Uh yeah, what exactly in the text you quoted is incorrect?