Too many users?

[wdz]

I'm writing a paper about maintaining VHF and UHF systems in addition to Trunking systems. I was curious to know what would happen if there are too many talk groups active at one time, what would happen. Say you have 20 frequencies and 300 talk groups. What happens when you have 25 agencies trying to talk on the system at the same time?

Thanks!

 

[Colin9690]

If more users than the system can handle trys to transmit, the users trying to transmit will be put on the system's "Holding Queue". Once a frequency has cleared up, the user with the HIGHEST PRIORITY is assigned to the open frequency. (Ex. Police might have highest priority, then fire, then maybe the lowest priority are sewer workers)

Hope This Makes Sense!

 

[Sac916]

Using a Motorola SmartNet for example

If a user attempts to transmit when there is not a frequency available, they will get a "tone" indicating the inability to transmit.

The radio system has a " user priority " system.

Meaning, each agency/user belongs to a rank system giving them priority over other users.

In Sacramento County for example ( WNYR751 ) The Sheriff's Department has priority #1

A Deputy's transmission will override a Bus or Garbage truck's transmission.
In the 8+ years WNYR751 has been in full service, I have always been able to transmit.

Radio management is key. The number of talk groups available to a user and total number of actual radios in use is imperative. Those that maintain the radio system have a variety of tools to monitor system status, usage, xmit time, etc etc

Currently in Sacramento County, the #1 user of the system is the Sacramento International Airport shuttle service. Granted their transmissions are very short, they xmit more than any other user of the system. That being said, The shuttles have the lowest priority and will never prevent the Sheriff's Dept. from getting on the air.

 

[wdz]

Just what I wanted to know! Thanks for the quick response guys!

 

[mmartinfan]

Bbbbbbbbbooooooooooooonnnnnnnnnnnnnnnnnnnnnnnkkkkkkkkkkkkkkk

 

[pinetree]

This question was exactly the main question that was asked here in Delaware when the 800 system was set up. The way that it was set up was that the Police (the key) has first use of the system. This gave the Fire Service a great deal of concern, as a call for help from a trapped fireman could be held up by an officer asking information on a car stop. However as it is for general use there are enough freqs.
The question is today what will happen in a major incident ie. hurricane. At the time of the last big one here in Delaware Gloria (85) Sussex county had more actual freqs. available to all services than there are freqs. assigned to the lower 2 counties combined. We hope that we will never have to find out, but with all the holes in the system ( no service) ???

 

[N4DES]

Using a Motorola SmartNet for example

If a user attempts to transmit when there is not a frequency available, they will get a "tone" indicating the inability to transmit.

The radio system has a " user priority " system.

Meaning, each agency/user belongs to a rank system giving them priority over other users.

In Sacramento County for example ( WNYR751 ) The Sheriff's Department has priority #1

A Deputy's transmission will override a Bus or Garbage truck's transmission.
In the 8+ years WNYR751 has been in full service, I have always been able to transmit.

Radio management is key. The number of talk groups available to a user and total number of actual radios in use is imperative. Those that maintain the radio system have a variety of tools to monitor system status, usage, xmit time, etc etc

Currently in Sacramento County, the #1 user of the system is the Sacramento International Airport shuttle service. Granted their transmissions are very short, they xmit more than any other user of the system. That being said, The shuttles have the lowest priority and will never prevent the Sheriff's Dept. from getting on the air.

Priority #1 is reserved for Emergency Button activations and I know in SmartZone the highest priority that can be issued is #2 for an end user. I'm not 100% on SmartNet, but I can't see it being any different than SmartZone.

As to the "override", your completely off on this one. The lower priority user does not get "knocked off". If there is a busy que the users with a higher priority go to the front of the line. If someone is talking they can continue to talk, even with a lower priority, until they release the channel back into the pool.

 

[N4DES]

I'm writing a paper about maintaining VHF and UHF systems in addition to Trunking systems. I was curious to know what would happen if there are too many talk groups active at one time, what would happen. Say you have 20 frequencies and 300 talk groups. What happens when you have 25 agencies trying to talk on the system at the same time?

Thanks!

That's easy...the end user gets a busy. Here are some of the stats that I generated the day after Hurricane Wilma on my 28 channel simulcast system:

Peak calls in a 24 hour period - 147,513
Total Airtime in Seconds in 24 hrs - 772,200
Average call length - 5.23 seconds
Average EARLANG 9.0
Busy Count 1090
Time in Busy Que - .935 seconds

Our normal call average is 65K daily with no busy's.

This is the product that I have configured in a Raid5 server that captures all of my loading data:

http://www.genesisworld.com/GenSZAI/GenSZAISetupAccumulator.htm

Mark
813A System Admin.
http://www.pbcgov.com/fdo/ESS/800MHz.htm

 

[RolnCode3]

Priority #1 is reserved for Emergency Button activations and I know in SmartZone the highest priority that can be issued is #2 for an end user. I'm not 100% on SmartNet, but I can't see it being any different than SmartZone.

As to the "override", your completely off on this one. The lower priority user does not get "knocked off". If there is a busy que the users with a higher priority go to the front of the line. If someone is talking they can continue to talk, even with a lower priority, until they release the channel back into the pool.

In the Sac County case, the Sheriff's Dept (and most other LE as well) are assigned Priority 3 according to the fleetmap. About 95% of the Fire talkgroups, as well as the Hospitals are also Priority 3. The rest of the priorities are scattered down to 8. No talkgroup on the system has a priority 2.

 

[N4DES]

That's fine....all of my Public Safety TG's and users have a priority of 6 and LG have a priority of a 7.
The only 2 users that have higher priority than PS is me and the Sheriff's 2 radios.

It a moot issue unless there are radios going into the busy que anyway.

 

[SCPD]

The question is today what will happen in a major incident ie. hurricane. At the time of the last big one here in Delaware Gloria (85) Sussex county had more actual freqs. available to all services than there are freqs. assigned to the lower 2 counties combined. We hope that we will never have to find out, but with all the holes in the system ( no service) ???

In this case you have to build the church big enough for Easter Sunday. How many people come to church on Easter Sunday and will there be more coming 5 years from now? That is the challenge, but if there are more frequencies available it is much easier to expand a trunked system than a conventional system, and in a way that is really seemless for the users.