How many tg's supported at one time

[Hoofy]

In our area most of the mpscs towers have a primary, an alternate, and 2 other frequencies assigned to them. My question is how many different talk groups could be supported at the same time from one of these towers????

An example would be like a situation where you have multiple agencies responding to an incident and trying to talk on their own tg. How many of the following tg's could be on at the same time using the same tower?

fire tg
police tg
# 1 ambulance tg
# 2 ambulance tg
first responders #1 agency tg
first responders #2 agency tg
first responders #3 agency tg

 

[Grog]

If a tower has five frequencies, one would be the control channel at a time leaving four voice frequencies for talkgroups. If you have a lot of different talkgroups in action, someone's gonna get "bonked"

 

[MtnBiker2005]

Interesting question....

I take it the P25 trunked system doesn't support "Voice on Control channel freq" like on other motorola system. ?

 

[Grog]

Interesting question....

I take it the P25 trunked system doesn't support "Voice on Control channel freq" like on other motorola system. ?

What other motorola radio systems? (not cellphone of course)

 

[MtnBiker2005]

Grog,

I saw it talked about on this PDF file I saw on Google search.

Voice on Control (VOC) Sites (Optional)
With Voice on Control (VOC), IntelliRepeater sites can be enabled to allow the control channel to be used
as a voice channel if all other voice channels are currently in use. VOC can be used on a four channel trunking site,
down to a single channel trunking site. VOC provides economical site capacity for low traffic sites
From motorola website.
www.motorola.com/governmentandenter...ProductInformation/ASTRO_Trunked_brochure.pdf
or
Wikipedia site (Motorola Type II)
http://en.wikipedia.org/wiki/Motorola_Type_II_VOC
or this RR thread someone asked.
http://www.radioreference.com/forums/showthread.php?t=119218

Just asking if this MPSCS P25 system/other P25 system could have the same feature like on the older Type II stuff.

 

[seamusg]

In our area most of the mpscs towers have a primary, an alternate, and 2 other frequencies assigned to them. My question is how many different talk groups could be supported at the same time from one of these towers????

An example would be like a situation where you have multiple agencies responding to an incident and trying to talk on their own tg. How many of the following tg's could be on at the same time using the same tower?

fire tg
police tg
# 1 ambulance tg
# 2 ambulance tg
first responders #1 agency tg
first responders #2 agency tg
first responders #3 agency tg

If they are responding to the same incident, they should be on the same tg, not 10 different ones. I thought the event tgs were for this.

 

[bigbluemsp]

The new Motorola Platform is supposed to handle anywhere from 2-4 voice paths at the same time sort of like the M/A Disaster

 

[Hoofy]

from SEAMUSG:
""If they are responding to the same incident, they should be on the same tg, not 10 different ones. I thought the event tgs were for this""

I believe that an "event tg" needs to be approved and turned on before it is usable.

In our rural area, units responding to an incident stay on the tg they were paged out on so that dispatch has to relay traffic that needs to be passed between tg's. Example: Keweenaw county sheriff, Eagle Harbor first responders, Mercy ambulance, MSP troop car, Calumet twp rescue with the jaws, and Lac Labelle fire, all responding to the same accident and only msp and sheriff will be on the same tg.
I don't know how their radios are set up but first responders will relay thru dispatch to give the ambulance an update and I also hear the county and MSP doing the same thing. Maybe this is a situation where operator education is needed.

However it sounds like the answer to my question is one tg per frequency.....

 

[bigbluemsp]

from SEAMUSG:
""If they are responding to the same incident, they should be on the same tg, not 10 different ones. I thought the event tgs were for this""

I believe that an "event tg" needs to be approved and turned on before it is usable.

In our rural area, units responding to an incident stay on the tg they were paged out on so that dispatch has to relay traffic that needs to be passed between tg's. Example: Keweenaw county sheriff, Eagle Harbor first responders, Mercy ambulance, MSP troop car, Calumet twp rescue with the jaws, and Lac Labelle fire, all responding to the same accident and only msp and sheriff will be on the same tg.
I don't know how their radios are set up but first responders will relay thru dispatch to give the ambulance an update and I also hear the county and MSP doing the same thing. Maybe this is a situation where operator education is needed.

However it sounds like the answer to my question is one tg per frequency.....

Most counties have their own event tg's or emergency ops tg's they can go to.

They can use a Event Tg but they have to call the NCC and request it then if approved its on in a matter of minutes.

 

[Thunderbolt]

However it sounds like the answer to my question is one tg per frequency.....

Yes, you are correct. Current ASTRO-25 system architecture, will support only one talkgroup per radio radio frequency pair. For instance, if 13COM is active on that frequency at any given moment, then that is the only talkgroup you will hear at that time. However, this will change in the future.

Motorola plans on beta testing their Project 25, Phase-II TDMA modulation very shortly, on the new Montgomery County Texas TRS. This new modulation method, will allow for two talkgroups to occupy a frequency pair at any time. Moreover, current technology supports 65,504 talkgroups on a Project 25 TRS. Motorola plans on increasing that number by a factor of four, maybe even eight in a few years. This means that future ASTRO platforms will be able to support anywhere from 262,016 to 525,024 talkgroups.

Currently, each regular MPSCS site will support up to 28 frequency pairs in the 800 MHz band. Likewise, they are fully capable of using 700 MHz band as well (once the treaty with Canada is passed). In addition, simulcast sites can use up to 30 frequency pairs if required, for highly active channel loading requirements. Currently, it's unknown if future versions of the ASTRO Operating System will support an increase in the number of available frequency pairs, but given the expansive and upgradable nature of the radio communications technology, it seems very likely that it will. Nonetheless, I would look for the number of frequency pairs at each tower to increase across the state in the future.

73s

Ron

 

[N_Jay]

The number of talkgroups is related to both the number of channels and the amount of traffic.

In general you get one less talk-path tan total channels due to the control channel.

Yes, P25 can have voice on control, but it is not an often used feature when you are over 2 channels.

Just because you have 4 talk-paths (5 channels) does not mean that you are limited to 4 talkgroups, as most talkgroups are not 10% busy and channel sharing with priority manages the use very well.

P25 Phase 2 will have 2 talk-paths per channel, but still use a full control channel.

Motorola TDMA (called X2, different from MOTOTRBO) is not P25 Phase 2, but is similar in function but not technology (initially) and is expected to evolve into P25 Phase 2.