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Old 06-07-2013, 12:54 AM
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Default Question about Phase I and II

Question, say today an agency chose to build a P25 trunking system... would they have to go Phase II? Or can they still still go Phase I or is Phase II mandatory now that it has succeeded Phase I.
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Old 06-07-2013, 1:06 AM
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There is no mandate (yet) to use Phase II, i.e. TDMA.

It's not entirely accurate to say that Phase II "succeeded" Phase I, rather it has built upon it. It's important to remember that Phase II only applies to trunked systems, not conventional P25, so Phase I is alive and well in that regard. As far as trunked systems, Phase II is very much optional at this point. In fact, it's an optional add-on for most (if not all) manufacturers. If you purchase a Motorola ASTRO 25 system tomorrow, you have to specify that you want TDMA functionality, and it's going to cost you a pretty penny.

Of course the upside is that you double your channel capacity with TDMA. So, a system that has 10 frequencies in the pool will have either 9 talkpaths with FDMA, or 18 talkpaths with TDMA (as always, one frequency is reserved for the control channel). That is a significant benefit to either upgrading a Phase I system to Phase II, or to spec'ing Phase II right out of the box.

One thing to keep in mind is that not all P25 radios are Phase II capable. With Motorola equipment, only the APX series is capable of TDMA, the XTL/XTS series are not. Motorola does offer a mixed-mode option on their ASTRO 25 systems that is called "DDM" or Dynamic Dual Mode. This allows a talkgroup to change between FDMA and TDMA on the fly depending on the capabilities of the radios affiliated with that particular talkgroup. So, if you have 5 APX radios affiliated with TG 1001, it will operate in TDMA mode. If an XTS affiliated with that talkgroup, it will fall back to FDMA mode. You find this option most often on systems that are transitioning between Phase I and Phase II, or systems that want to run in Phase II mode 95% of the time, but may have to support a few outside agencies for mutual aid purposes who don't have TDMA capable radios.


The short answer: Phase II TDMA is completely optional, you can run in Phase I FDMA mode on a brand new system, no problem.
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Old 06-07-2013, 1:17 AM
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Quote:
Originally Posted by Chauffeur6 View Post
There is no mandate (yet) to use Phase II, i.e. TDMA.

It's not entirely accurate to say that Phase II "succeeded" Phase I, rather it has built upon it. It's important to remember that Phase II only applies to trunked systems, not conventional P25, so Phase I is alive and well in that regard. As far as trunked systems, Phase II is very much optional at this point. In fact, it's an optional add-on for most (if not all) manufacturers. If you purchase a Motorola ASTRO 25 system tomorrow, you have to specify that you want TDMA functionality, and it's going to cost you a pretty penny.

Of course the upside is that you double your channel capacity with TDMA. So, a system that has 10 frequencies in the pool will have either 9 talkpaths with FDMA, or 18 talkpaths with TDMA (as always, one frequency is reserved for the control channel). That is a significant benefit to either upgrading a Phase I system to Phase II, or to spec'ing Phase II right out of the box.

One thing to keep in mind is that not all P25 radios are Phase II capable. With Motorola equipment, only the APX series is capable of TDMA, the XTL/XTS series are not. Motorola does offer a mixed-mode option on their ASTRO 25 systems that is called "DDM" or Dynamic Dual Mode. This allows a talkgroup to change between FDMA and TDMA on the fly depending on the capabilities of the radios affiliated with that particular talkgroup. So, if you have 5 APX radios affiliated with TG 1001, it will operate in TDMA mode. If an XTS affiliated with that talkgroup, it will fall back to FDMA mode. You find this option most often on systems that are transitioning between Phase I and Phase II, or systems that want to run in Phase II mode 95% of the time, but may have to support a few outside agencies for mutual aid purposes who don't have TDMA capable radios.


The short answer: Phase II TDMA is completely optional, you can run in Phase I FDMA mode on a brand new system, no problem.
Thanks so much for the reply. You're always helpful within the community, I appreciate that.
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Old 06-07-2013, 4:13 PM
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Quote:
Originally Posted by Chauffeur6 View Post
Of course the upside is that you double your channel capacity with TDMA. So, a system that has 10 frequencies in the pool will have either 9 talkpaths with FDMA, or 18 talkpaths with TDMA (as always, one frequency is reserved for the control channel). That is a significant benefit to either upgrading a Phase I system to Phase II, or to spec'ing Phase II right out of the box.
One caveat, you can only have a maximum of 28 talkpaths (with Motorola, not sure about others). Even if you have a 21 channel system, you are still limited to 28, that "should" change with a future software enhancement.
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Old 04-11-2014, 1:13 AM
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So in other words, P25 Phase II is something you'll only see in large cities.
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Old 04-11-2014, 2:14 AM
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Quote:
Originally Posted by seanhenderson View Post
Question, say today an agency chose to build a P25 trunking system... would they have to go Phase II? Or can they still still go Phase I or is Phase II mandatory now that it has succeeded Phase I.
6.25 kHz efficiency IS mandatory for 700 MHz. (at this time by 12/31/16) Phase II (TDMA)is a necessary evolution/solution to achieve that.

...though Louisiana has already had an extension of that deadline approved until 2024.

Mandates for 6.25 kHz efficiency for other bands will come eventually, but that is still pretty far into the future.
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Old 05-19-2014, 4:31 PM
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Quote:
Originally Posted by pinballwiz86 View Post
So in other words, P25 Phase II is something you'll only see in large cities.
Not necessarily. I would not consider my city to be large (Population of about 118,000) We are in the early stages of upgrading our system (800 MHz EDACS) and I believe the intention is to go to Phase II.
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Old 06-11-2014, 2:00 PM
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Very informative, TYVM!

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Old 06-11-2014, 3:13 PM
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And for whatever it's worth, Phase II is backward compatible with Phase I operation, although not necessarily with conventional. In short, with TDMA @ 6.25KHzΔ, you approximately double the capacity, provided the system is capable (and designed) to handle the added resource. Here's a basic visual representation of how the different systems compare.
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Old 06-11-2014, 5:56 PM
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You will be hard pressed to find anyone currently deploying a Phase 1 system these days as all major vendors are currently selling Phase 2 infrastructure and phasing out phase 1 only infrastructure. Also while Phase 2 systems are backwards compatible with Phase 1 SUs, many systems may lock their talkgroups to Phase 2 only to preserve talk paths.


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Old 06-11-2014, 7:15 PM
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Quote:
Originally Posted by DisasterGuy View Post
Also while Phase 2 systems are backwards compatible with Phase 1 SUs, many systems may lock their talkgroups to Phase 2 only to preserve talk paths.
True, Disaster. This was assuming of course that, for whatever reason, the Phase II system wanted to grant access to the Phase I SUs. If they cannot upgrade all SUs to Phase II status concurrently, this would be a benefit.
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Old 07-04-2014, 7:42 AM
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Quote:
Originally Posted by DisasterGuy View Post
You will be hard pressed to find anyone currently deploying a Phase 1 system these days as all major vendors are currently selling Phase 2 infrastructure and phasing out phase 1 only infrastructure. Also while Phase 2 systems are backwards compatible with Phase 1 SUs, many systems may lock their talkgroups to Phase 2 only to preserve talk paths.


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I think that your position is not totally correct. What I think you will find is that the new system may be capable of phase 2 operation. The systems are being installed as phase 1 functionality due to equipment migration. Many agencies are going to new P25 systems, but are using their old user equipment during the migration. As they purchase the newer user equipment, then you will see a slow migration into the phase 2 operations as channel use dictates more capaqcity.

You will see groups of users switched over to the phase 2 as the whole group has the newer equipment available to them. This will cause the system to bounce back and forth between phase 1 and phase 2 users as they key up and talk. I know of several systems in the works that are going from an EDACS trunking system to a Motorola P25 system. The Harris radios currently in use can do the P25, but they can't do the phase 2. So initially the users will go onto the new system as a phase 1 user. As equipment gets updated over the next few years, then they can switch over to phase 2 operations if needed.

I know of no reason to press for phase 2 out of the gate on any system upgrade except for the vendor to make more money. The more they can BS their way through a customer that doesn't understand the issues, the greater the bank account gets for the sales force. See it happen all the time when an agency doesn't have a third party sit in and guide them through the process.
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Old 07-04-2014, 9:14 AM
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Jim- you are spot on. I was talking about the infrastructure itself not the mode it is operating in.


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Old 07-10-2014, 2:45 AM
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Default P25 Phase-II

About how many P25 systems in the US are actually operating Phase-II TDMA mode?
Anybody got a handle on this?

TIA, Larry
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Old 07-10-2014, 2:56 AM
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May not be entirely complete, as it has to be added to each individual system's wiki article but....
Template:P2Tracker - The RadioReference Wiki
Then select "What links here"
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Old 07-10-2014, 3:00 PM
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W7JYJ, please do not post the same question across multi threads, I provided you an anwser in the tread you started for this question.

By no having it in multi-threads, it helps user looking for the same anwser as you in the future as they search the forum.

Thanks
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Old 07-11-2014, 12:18 AM
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Default P25 Phase-II

gesucks:

Actually, I asked two separate questions. One question asked if there's a list somewhere of
P25 phase-2 systems. The other question in a different thread asked how many phase-2
systems are in operation. Not the same question... Please lighten up!

I have been researching this and found, e.g., that there is a P25 Phase-2 system operated
by Santa Clara County. But the database list of trunking systems in Santa Clara County
does NOT show it. The database does list Santa Clara County as having a legacy Motorola Type-II
SmartNet system... Appears that the database is not up to date even though the SC P25
system has been in operation for a few months. Though not necessarily as a Phase-2
system in the beginning. Callsign WQSE773, WQSE774, and others. Licenses issued about
ten months ago.

--Larry
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