site trunking question

[speedway_navigator]

Our 20 by 20 mile county has a 4 site P-25 simulcast system. My understanding is if we lose the microwave link to the main site that site goes into site trunking.

If a portable on the west side keys and only hits the closest site there is a good chance most radios would hear that site in site trunking.
If another user on the east side keys and only hits the east site could both be on the same freq since the west site is operating independently or do the repeaters monitor the air for traffic before transmitting?
I think the odds would low with 10 channels per site but in theory I don't see why it couldn't, but I don't have any P-25 experience.

 

[Ubbe]

Not knowing how critical the main site is and how much coverage the supporting sites have, I personally wouldn't configure the sites to use Local Site Trunking in a simulcast system. The control channel and the voice channels wouldn't send the same info as the other sites. Dispatchers have no communication with the mobiles on the LST site and the mobiles would only be able to talk to each other creating confusion. It would propably be chaos if one site where in LST. Better to just allow wide trunking or else cut off the transmitters. In a non-simulcast system it's much more easy to have dispatchers use a backup mobile on the LST sites frequency and have full communication. That's one of the most negative aspects of using simulcast, how to handle local site trunking, if it even would be allowed.

/Ubbe

 

[TampaTyron]

Simulcast sites won't transmit if the backhaul (microwave) or timing reference fails. The remaining sites with backhaul and timing will continue to operate. If there is no backhaul at all, there will be a lone site transmitting. TT

 

[MTS2000des]

What Tampa says is correct, at least in Astro 25 simulcast operation, lose your backhaul to your prime/master or DSR, and you're in failsoft. No call processing subsystem/core link=failsoft.

TRAK9100 goes belly up (or resets), RFSS goes offline until it syncs back up. Links down? Failsoft.

At least that what I have experienced on the two times in 4 years I've experienced going into failsoft on our 7.16 system.

 

[TampaTyron]

I just want to clarify that in a non-simulcast system that failsoft is all repeaters at all sites transmitting continuously. Failsoft in a simulcast system is only the main site transmits, that the other sites are disabled to prevent interference. I am a TRBO guy, but occasionally bump into Astro. TT

 

[MTS2000des]

Failsoft in a simulcast system is only the main site transmits, that the other sites are disabled to prevent interference.

Not true. During both failures and during our implementation and Astro 25 system manager workshop, I was instructed to put my system in failsoft and site trunking through the UNC. During failsoft, all 15 of our simulcast RF sub-sites transmit the failsoft word, and carriers come up on subscriber radios and display the failsoft message on the subscriber. This was done to simulate what happens so we know what we would later experience post go-live.

The two failures (one of which occurred last year when a script hung while the ATIA was upgrading from 7.14 to 7.16), it caused a failsoft incident that lasted 45 minutes. During that time we still had simulcast, as each RFSS has a TRAK9100 and so long as it stays operational, the site remained on the air in failsoft as did our other 14 RFSS's. We had simulcast operation but no call processing (trunking).

 

[KevinC]

Not true. During both failures and during our implementation and Astro 25 system manager workshop, I was instructed to put my system in failsoft and site trunking through the UNC. During failsoft, all 15 of our simulcast RF sub-sites transmit the failsoft word, and carriers come up on subscriber radios and display the failsoft message on the subscriber. This was done to simulate what happens so we know what we would later experience post go-live.

The two failures (one of which occurred last year when a script hung while the ATIA was upgrading from 7.14 to 7.16), it caused a failsoft incident that lasted 45 minutes. During that time we still had simulcast, as each RFSS has a TRAK9100 and so long as it stays operational, the site remained on the air in failsoft as did our other 14 RFSS's. We had simulcast operation but no call processing (trunking).

That seem s like a recipe for disaster (failsoft at all subsites at the same time) as all subsites would be keyed at the same time potentially carrying different traffic. I have a feeling that exact scenario is not happening...but I could be wrong.

 

[MTS2000des]

That seem s like a recipe for disaster (failsoft at all subsites at the same time) as all subsites would be keyed at the same time potentially carrying different traffic. I have a feeling that exact scenario is not happening...but I could be wrong.

You're assuming RF subsites are in different zones. Not true in my case, our system is the largest SINGLE ZONE Astro 25 system in the state. All RFSSs are in a single zone configuration. Why is done that way is a TLDR story but our situation is unique. So in our configuration, it makes perfect sense that, should ST/FS occur, all sites carry the same traffic if at all possible.

 

[KevinC]

You're assuming RF subsites are in different zones. Not true in my case, our system is the largest SINGLE ZONE Astro 25 system in the state. All RFSSs are in a single zone configuration. Why is done that way is a TLDR story but our situation is unique. So in our configuration, it makes perfect sense that, should ST/FS occur, all sites carry the same traffic if at all possible.

Actually I didn't assume anything. But this isn't the place to argue this, so I'm done.

 

[MTS2000des]

Actually I didn't assume anything.

But you said:

That seem s like a recipe for disaster (failsoft at all subsites at the same time) as all subsites would be keyed at the same time potentially carrying different traffic. I have a feeling that exact scenario is not happening...but I could be wrong.

Which is indeed, an assumption. and factually incorrect in my case.

But this isn't the place to argue this, so I'm done.

But you felt the need to step in anyway. Uh, ok.

 

[KevinC]

But you said:

Which is indeed, an assumption. and factually incorrect in my case.


But you felt the need to step in anyway. Uh, ok.

Ok, you win.

 

[GTR8000]

You're assuming RF subsites are in different zones. Not true in my case, our system is the largest SINGLE ZONE Astro 25 system in the state. All RFSSs are in a single zone configuration. Why is done that way is a TLDR story but our situation is unique. So in our configuration, it makes perfect sense that, should ST/FS occur, all sites carry the same traffic if at all possible.

Your post is confusing. Are you talking about a single simulcast cell comprised of 14-15 subsites? If so, then of course they are all in the same zone, as it is considered a single site by the system. There is nothing unique about that at all, in fact many ASTRO 25 systems have numerous simulcast cells comprised of numerous subsites within a single zone, even with a multi-zone capable M3 core. Take a look at some of the larger statewide ASTRO 25 systems and you'll see that it's the rule, not the exception.

PS - "RFSS" has a specific meaning when it comes to P25: "Radio Frequency SubSystem" aka "Zone" in ASTRO 25 speak. You're using "RFSS" to describe simulcast subsites (Simulcast Remote Sites), which is the wrong terminology.

 

[MTS2000des]

Your post is confusing. Are you talking about a single simulcast cell comprised of 14-15 subsites?

Exactly. Nothing confusing about that for me.

Are you talking about a single simulcast cell comprised of 14-15 subsites? If so, then of course they are all in the same zone, as it is considered a single site by the system.

Correct. Which, in the O/P's case, may or may not apply. Can't speak to that system(s), only the one I have my hands in.

Take a look at some of the larger statewide ASTRO 25 systems and you'll see that it's the rule, not the exception.

I'm well aware. Been to Schaumburg (before it was moved downtown) got the ticket and the T-shirt.

PS - "RFSS" has a specific meaning when it comes to P25: "Radio Frequency SubSystem" aka "Zone" in ASTRO 25 speak. You're using "RFSS" to describe simulcast subsites (Simulcast Remote Sites), which is the wrong terminology.

You got me, though not to nitpick, but our MSI STs refer to our "SRS" as "RFSS" in both emails and during project meetings. So I'll pass this along to them as well.

 

[GTR8000]

It's confusing when you use incorrect terminology and make statements like "You're assuming RF subsites are in different zones"

I very seriously doubt that Kevin is assuming that simulcast subsites of the same site are in different zones, when that's not even possible with an ASTRO 25 system....but I could be wrong.

 

[TampaTyron]

I have been to Elgin (CCSI) where systems are staged (assembled and tested before being accepted and shipped to customers) countless times. In fact, I may have touched the system during assembly/testing before it was presented to the customer for acceptance. I get what is being said, but we are debating very high level technical minutiae on a hobbiest website. I think most scanner listeners could read this thread and figure out if the system behavior they observe is likely regular behavior or some sort or failure mode. TT

 

[KevinC]

I have been to Elgin (CCSI) where systems are staged (assembled and tested before being accepted and shipped to customers) countless times. In fact, I may have touched the system during assembly/testing before it was presented to the customer for acceptance. I get what is being said, but we are debating very high level technical minutiae on a hobbiest website. I think most scanner listeners could read this thread and figure out if the system behavior they observe is likely regular behavior or some sort or failure mode. TT

But this is the Motorola forum and not a scanner forum so I expect technical topics to be discussed.

I went to a warehouse in Dallas once where they used Motorola radios. Does that count?

 

[GTR8000]

I agree with Kevin. We're in the Industry Discussion section, where the expectation should be for higher level, more technical discussions to take place than would be found elsewhere on this site. System Administration and Maintenance is another section where the same should apply. I'm sure some members of that other forum would scoff at the notion of any intelligent discussion taking place anywhere on this site, but that's another topic entirely.

 

[KevinC]

I decided I'd play along some more...

While it's technically possible to have all 14, 15, whatever subsites in a simulcast in failsoft I think it's a bad design. If subscriber A only gets into subsites 1, 2 and 3 units close to other subsites may not hear the traffic and talk at the same time on subsites 9, 10 and 11, causing bad interference in overlap areas.

Personally I would ( if I was using failsoft) pick a few strategic subsites to have failsoft to minimize interference. And yes I understand failsoft is a SHTF feature, but judicious programming can make it less of a disaster. Or just not use failsoft at all.

 

[GTR8000]

Ah, DSR is such a wonderful thing if you're lucky enough to have it!

 

[KevinC]

Ah, DSR is such a wonderful thing if you're lucky enough to have it!

And Geo-Prime.