P25 multisite neighbors

[DaveNF2G]

Do radio affiliations affect the designation of tower sites as "neighbors"?

Here is a scenario that might clarify the question:

Suppose a radio unit is taken from one end of a multisite P25 trunked system's coverage area to the other. When the radio reaches the distant site, it is turned on. Alternatively, the user of the radio switches to a talkgroup that is normally used "back home."

Does the affiliation of the radio to its "back home" talkgroup cause the distant tower site to be listed by the "back home" tower site as a "neighbor"?

I am asking this because I am attempting to use "neighbor" information as an aid to mapping out a very large multisite P25 trunked system. As I nail down the exact locations of more towers, some of the neighbor site listings make less sense. I am beginning to suspect that some of these listings are specious, perhaps caused by situations like the above scenario.

I need a P25 trunking expert to set me straight. Thanks in advance.

[seamusg]

Originally Posted by DaveNF2G

Do radio affiliations affect the designation of tower sites as "neighbors"?

Here is a scenario that might clarify the question:

Does the affiliation of the radio to its "back home" talkgroup cause the distant tower site to be listed by the "back home" tower site as a "neighbor"?

I need a P25 trunking expert to set me straight. Thanks in advance.

I'm not an expert, but as far I know the neighbor sites are the ones closest to the site and tells the radios what the next CC is for roaming. So the answer is no, I base this on watching the MPSCS system on PRO96COM.

[wlmr]

Originally Posted by DaveNF2G

Do radio affiliations affect the designation of tower sites as "neighbors"?

Nope, two separate things. Adjacent site broadcast lists and radio/talkgroup affilliations.

The tower sites "neighbors" are set in the system using a matrix known as the adjacent site broadcast list. Very simply put, these adjacent sites are picked to help with roaming from a tower to the ones near it.

Originally Posted by DaveNF2G

Suppose a radio unit is taken from one end of a multisite P25 trunked system's coverage area to the other. When the radio reaches the distant site, it is turned on. Alternatively, the user of the radio switches to a talkgroup that is normally used "back home."

When the radio turns on it searches for control channel frequencies for it's system. (Detailed discussion of all the variations on how this can be set up skipped here.) After the system recognizes the radio as belonging, the radio then tells the system what talkgroup it wants to use. The radio traffic for that talkgroup then starts being heard by someone with a scanner listening to that site. BUT, the system can tell the radio that talkgroup isn't allowed here away from it's normally planned area and can tell the radio to move on & find another site. While the radio was parked on the first site it finds out what other system towers are nearby via the adjacent site broadcast list.

Originally Posted by DaveNF2G

Does the affiliation of the radio to its "back home" talkgroup cause the distant tower site to be listed by the "back home" tower site as a "neighbor"?

Nope, just tells the system that another talkgroup will need to use the tower (if allowed).

Originally Posted by DaveNF2G

I am asking this because I am attempting to use "neighbor" information as an aid to mapping out a very large multisite P25 trunked system. As I nail down the exact locations of more towers, some of the neighbor site listings make less sense. I am beginning to suspect that some of these listings are specious, perhaps caused by situations like the above scenario.

I need a P25 trunking expert to set me straight. Thanks in advance.

What doesn't make sense to you MAY (?!?) have logical reasons to the system people. Or not.

[DaveNF2G]

Thanks, wlmr, for the explanations.

Another possible reason for the oddball neighbor listings is that new sites have been added since the last time the data were collected, so maybe those same towers are listing different neighbors now.

Tough to verify, though - this system covers a few thousand (!) square miles of upstate New York.