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  #1 (permalink)  
Old 11-09-2011, 7:56 PM
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Default Motorola X2-TDMA vs P25 Phase II TDMA

There is already a ton of confusion out there about the differences between Motorola's X2-TDMA and the final P25 Phase II TDMA standard. That's not exactly what this thread is about, though. The problem is that the way P25 systems are listed in the RR DB doesn't help matters.

There's a trunked system report Project 25 X2-TDMA Systems, which lists 13 or so systems that have been identified as using TDMA of some form. That's where the confusion comes into play.

If you click on any of those systems and look at their DB page, you find the following conflicting information:

System Type: Project 25 Motorola X2-TDMA

and then

Some talkgroups on this system are using Project 25 Phase II TDMA modulation

X2-TDMA is not Phase II TDMA. X2-TDMA is Motorola's flavor of TDMA, a precursor to the final Phase II TDMA standard, which only started shipping this August.

This really ought to be clarified in the DB. The text of the Important Note should be changed from "Project 25 Phase II TDMA" to "Motorola X2-TDMA".

Of course, there will be systems coming online that will be pure Phase II TDMA and won't use Motorola X2-TDMA, which means a new system type will have to be added to the RR DB, with the corresponding report to accurately reflect the difference between the two types.

Eventually the Motorola X2-TDMA systems will be fully converted to the official P25 Phase II TDMA standard, and this won't be an issue any longer. But during this transition period, the difference really should be distinguished.

Last edited by Chauffeur6; 11-09-2011 at 7:58 PM..
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Old 11-09-2011, 9:00 PM
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Two questions...

1) What difference does the differentiation between X2 and Phase II add to the consumer of RR data? At this point there is only one TDMA capable scanner product.

2) Who is qualified to validate and confirm this info you are suggesting? I live in an area with several up and running TDMA systems and if I wasn't an authorized guest on their system(s) and didnt have software at work to program my govt issued APX radio, I wouldn't know (and wouldn't be qualified) or be able to determine if they were yet using Phase II instead of X-2.

I agree with the differentiation, but I would suggest it might be better to track or make notation of what systems are TDMA exclusive vs.TDMA.

For example, the listings for many new P25 system say "System Type: Project 25 Motorola X2-TDMA", "System Voice: APCO-25 Common Air Interface Exclusive" and the warning you mention says "Some talkgroups on this system are using Project 25 Phase II TDMA modulation which cannot be monitored by most scanners."

However, while some are exclusive, many of these systems are not TDMA exclusive, meaning that if an FDMA radio affiliates on a talkgroup that talkgroup reverts to FDMA and any digital capable scanner can listen.


As it stands, because these systems are listed in the database as TDMA, it doesnt get picked up by the weekly Uniden database conversion for the HP-1 and you cant listen to them on the HP-1 (without manual programming) even though there would be or could be transmissions that the HP-1 is capable of scanning.

I would say if they are looking at this topic that RR take a hard look if X2 or Phase II differention is needed, but more so if a flag for TDMA 'exclusivity' is needed.

Note: Its easy for someone to determe if a system is TDMA exclusive - listen to the system for a while on a non-TDMA capable digital scanner (I suggest prime time of day to do this is during a weekday when a neighboring jurisdiction is likely parked on a talkgroup with an non-TDMA (FDMA) transciever.)

Thoughts?
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Old 11-09-2011, 9:31 PM
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Quote:
Originally Posted by c5corvette View Post
1) What difference does the differentiation between X2 and Phase II add to the consumer of RR data? At this point there is only one TDMA capable scanner product.
Given that the PSR-800 is currently the only scanner that can decode any form of TDMA, at this point the differentiation probably doesn't make much of a difference on the surface to the majority of end-users.

However, three points:

1) The database should always strive to provide the most accurate information possible. Given that X2-TDMA and Phase II TDMA are technically two different things, the terms really should not be used interchangeably.

2) At some point, the X2-TDMA systems will almost surely all be converted to Phase II TDMA systems. Why shouldn't the DB therefore differentiate between the two, especially as true Phase II TDMA systems are starting to be installed? Systems that will never use the X2-TDMA protocol because they've shipped after Phase II TDMA was finalized. Eventually the X2-TDMA distinction will be irrelevant and shouldn't show up anywhere in the DB.

3) The PSR-800 has only been officially confirmed by GRE to work on Motorola X2-TDMA systems. It has not yet been officially confirmed to work on Phase II TDMA systems. If the DB made the clear distinction between the two, it would be easier for end-users to differentiate between the two, and perhaps be better able to confirm whether the PSR-800 in fact will decode true Phase II TDMA systems.



Quote:
Originally Posted by c5corvette View Post
2) Who is qualified to validate and confirm this info you are suggesting? I live in an area with several up and running TDMA systems and if I wasn't an authorized guest on their system(s) and didnt have software at work to program my govt issued APX radio, I wouldn't know (and wouldn't be qualified) or be able to determine if they were yet using Phase II instead of X-2.
Those with intimate knowledge of the system being installed or brought online will know whether the system is X2-TDMA or Phase II TDMA. There are currently only 13 systems in the DB flagged as TDMA, so it's not as if we're talking about a monumental task to identify them all.

Additionally, any systems that ship after August 2011 are inherently Phase II TDMA. Yes, they may continue to use mix-mode X2-TDMA and Phase II TDMA until all subscriber units have been software updated or hardware upgraded, but refer to my previous point about the eventuality of all X2-TDMA systems moving to the Phase II TDMA standard.

Or perhaps, if the PSR-800 proves not to be able to decode Phase II TDMA out-of-box without a firmware update, then I suppose end-users monitoring those systems that switch from X2-TDMA to Phase II TDMA will figure out pretty quickly what standard the system is using!



Quote:
Originally Posted by c5corvette View Post
I agree with the differentiation, but I would suggest it might be better to track or make notation of what systems are TDMA exclusive vs.TDMA.

For example, the listings for many new P25 system say "System Type: Project 25 Motorola X2-TDMA", "System Voice: APCO-25 Common Air Interface Exclusive" and the warning you mention says "Some talkgroups on this system are using Project 25 Phase II TDMA modulation which cannot be monitored by most scanners."

However, while some are exclusive, many of these systems are not TDMA exclusive, meaning that if an FDMA radio affiliates on a talkgroup that talkgroup reverts to FDMA and any digital capable scanner can listen.


As it stands, because these systems are listed in the database as TDMA, it doesnt get picked up by the weekly Uniden database conversion for the HP-1 and you cant listen to them on the HP-1 (without manual programming) even though there would be or could be transmissions that the HP-1 is capable of scanning.

I would say if they are looking at this topic that RR take a hard look if X2 or Phase II differention is needed, but more so if a flag for TDMA 'exclusivity' is needed.

Note: Its easy for someone to determe if a system is TDMA exclusive - listen to the system for a while on a non-TDMA capable digital scanner (I suggest prime time of day to do this is during a weekday when a neighboring jurisdiction is likely parked on a talkgroup with an non-TDMA (FDMA) transciever.)

Thoughts?
I agree with the issue of FDMA/TDMA mixed-mode versus TDMA Exclusive, however that's another issue entirely, perhaps a topic for another thread. Let's get one issue at a time straightened out.

It's also worth noting that every P25 system technically is and always will be backwards compatible with FDMA. That's just part of the standard. If an FDMA subscriber unit affiliates to a normally TDMA TG, it will revert to FDMA. Now I suppose there's a setting the sysadmin can enable to prevent FDMA units from operating on the system, however I'm not sure in reality you'll see that practice put in place. Especially not on public safety systems, where interoperability is the name of the game. Or should be, at least.

My personal opinion on the matter is that the FDMA versus TDMA TG distinction should exist at the TG level, not the system level. Similar to the way a TG is flagged as Analog, Digital, Encrypted, etc. Flagging FDMA vs TDMA at the system level means that the HP-1 won't get anything, even if some of the TG's are not TDMA.
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Old 11-09-2011, 9:59 PM
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I am still not convienced that the people with 'intimate' knowledge will update the database. And, if you are so sure that these systems will all eventually be Phase II, why should anyone care about the interim?

Quote:
Originally Posted by Chauffeur6 View Post
It's also worth noting that every P25 system technically is and always will be backwards compatible with FDMA. That's just part of the standard. If an FDMA subscriber unit affiliates to a normally TDMA TG, it will revert to FDMA. Now I suppose there's a setting the sysadmin can enable to prevent FDMA units from operating on the system, however I'm not sure in reality you'll see that practice put in place. Especially not on public safety systems, where interoperability is the name of the game. Or should be, at least.
I agree with you from an interop perspective, but I believe if you look closely, Prince George's MD operates a system with TDMA only talkgroups that can't be affiliated onto with an FDMA radio. While surrounding jurisdictions don't like it this way, PG has several FDMA specific talkgroups to accomidate the interop issue.

Quote:
Originally Posted by Chauffeur6 View Post
My personal opinion on the matter is that the FDMA versus TDMA TG distinction should exist at the TG level, not the system level. Similar to the way a TG is flagged as Analog, Digital, Encrypted, etc. Flagging FDMA vs TDMA at the system level means that the HP-1 won't get anything, even if some of the TG's are not TDMA.
For the reasons quoted above with PG's system, flagging the talkgroup FDMA or TDMA would need to include a category to flag for BOTH.

Geez... this gets complicated.
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Old 11-09-2011, 10:32 PM
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Originally Posted by c5corvette View Post
And, if you are so sure that these systems will all eventually be Phase II, why should anyone care about the interim?
Because X2-TDMA is not Phase II TDMA, simple as that.

Look, we can debate this thread to death with posts written out as long as short stories, but in the end the point remains that A does not equal B. The database should strive to provide the most accurate, up-to-date information possible, within reason. Given that there are only 13 of these TDMA systems currently in the database, I think it's quite reasonable and manageable to clean up the verbiage so it accurately reflects the technology being used.

If Eric or Lindsay don't think it's worth looking into making the distinction, that's perfectly fine. However in all honesty and without intending to offend, I really have no great desire to debate the issue with other end-users of this site. This thread was intended to be less of a "solicit every Tom, Dick and Harry's opinion on the subject" thread, and more of a direct appeal to the administration of the database for their guidance, consideration and decision on the matter.

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Old 11-10-2011, 5:59 AM
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Quote:
Originally Posted by Chauffeur6 View Post
Because X2-TDMA is not Phase II TDMA, simple as that.
Are you sure about that ;-)
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Old 11-10-2011, 9:51 AM
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Quote:
This really ought to be clarified in the DB. The text of the Important Note should be changed from "Project 25 Phase II TDMA" to "Motorola X2-TDMA".
I updated the important note to the following:

Some talkgroups on this system are using TDMA modulation which cannot be monitored by most scanners.

That should resolve the issue.
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Old 11-10-2011, 11:25 AM
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Quote:
Originally Posted by Chauffeur6 View Post
Because X2-TDMA is not Phase II TDMA, simple as that.
&
Quote:
Originally Posted by loco-lee View Post
Are you sure about that ;-)
Yes, that is a good question. Since we can all admit that Motorola probably had a lot more influence on the P25 standard than other vendors might have been comfortable with. And since Motorola P25 TRS installations are subject to having some extensions to the standard (note they meet the standard and are fully interoperable and any vendor P25 radio can use the system); is it just possible that when the first Phase II system is in place we may find there is virtually no difference with an X2 system? As for what we call it in the database; that is subjective. The title has already undergone revision, it probably will be revised again, as Lindsay took care of a little earlier today.

As to the problem with the HP-1 weekly download, this has already been discussed and I liken it to the arbitrary decision Uniden made to not download "other" service tags initially; I don't know the status of that problem at the moment. Uniden's chief competition in this "on board RR database" type radio does not differentiate; indeed all things are contained, although some are marked as "locked out" by default (encrypted channels for example) they can are there on the card. The bottom line is that IMHO, Uniden should be downloading everything and if the radio is not able to monitor it by design (TDMA, encryption, etc.) then mark them as locked out and let the more advanced users deal with individual needs.
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Old 11-10-2011, 12:31 PM
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Quote:
Originally Posted by loco-lee View Post
Are you sure about that ;-)
100% sure... read on:

X2 TDMA is 9600bps, Phase II TDMA is 12kbps.. not the same animal. I also would not put alot of faith in an X2 system being guarenteed to be uplifted to Phase II anymore than someone could say a system running VSELP will be guarenteed to turn into Phase I FDMA. It is not a simple or trivial matter to uplift one to another. I am fully aware of a particular system that is X2-TDMA capable, but has ZERO plans on uplifting the infrastructure nor subscribers to Phase-II TDMA capable.
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Old 11-10-2011, 12:35 PM
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Quote:
Originally Posted by loumaag View Post
Yes, that is a good question. Since we can all admit that Motorola probably had a lot more influence on the P25 standard than other vendors might have been comfortable with. And since Motorola P25 TRS installations are subject to having some extensions to the standard (note they meet the standard and are fully interoperable and any vendor P25 radio can use the system); is it just possible that when the first Phase II system is in place we may find there is virtually no difference with an X2 system? As for what we call it in the database; that is subjective. The title has already undergone revision, it probably will be revised again, as Lindsay took care of a little earlier today.
Until and unless it is definitively shown that both technologies are in fact identical, I personally feel that it's worthwhile differentiating and distinguishing between them.

That being said, Lindsay definitely addressed my primary concern swiftly and expeditiously, as usual!


Quote:
Originally Posted by loumaag View Post
As to the problem with the HP-1 weekly download, this has already been discussed and I liken it to the arbitrary decision Uniden made to not download "other" service tags initially; I don't know the status of that problem at the moment. Uniden's chief competition in this "on board RR database" type radio does not differentiate; indeed all things are contained, although some are marked as "locked out" by default (encrypted channels for example) they can are there on the card. The bottom line is that IMHO, Uniden should be downloading everything and if the radio is not able to monitor it by design (TDMA, encryption, etc.) then mark them as locked out and let the more advanced users deal with individual needs.
I completely agree with this also. Include everything, lock out the stuff that can't be monitored, leave the rest up to the consumer. Seems as if Uniden is trying to really dumb down the process to the point where they're trying to eliminate as much end-user "issues" as possible. Rather than have Joe Novice try to unlock a TDMA TG, only to have him complain that he never hears his local PD...just eliminate the possibility altogether by excluding the entire system entirely from the device's database.
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Old 11-10-2011, 1:54 PM
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Quote:
Originally Posted by grem467 View Post
100% sure... read on:

X2 TDMA is 9600bps, Phase II TDMA is 12kbps...

Someone is confused!!! What the heck are you trying to say?
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Old 11-10-2011, 2:34 PM
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I apologize for causing any confusion, hopefully i can alleviate some of it. Lets go over the differences between X2 TDMA and Phase II trunking systems. Both systems use an FDMA 9600bps control channel. For the voice channels, an X2 TDMA transmission the data rate is also 9600bps, this results in less bandwidth for the voice frames due to the timeslotting in comparason to a FDMA phase I channel which is at the same data rate. In an effort to provide similar voice quality to FDMA, it was decided to increase the size of the voice frames, thus requiring a faster data rate of 12kbps.

Even looking at the emission masks, you can see that additional bandwidth is required for Phase II over X2:

FDMA (Non Simulcast): 8K10F13 (8K70D1W for LSM)
X2 TDMA (Non simulcast): 8K10F7W (8K7D7W for LSM)
P2 TDMA (Non Simulcast): 9K80D7W
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Old 11-10-2011, 2:40 PM
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My understanding at IWCE last year is that X2 was released with the APX7500 radios to get PG county going with the plans of it going to true P25 P2. What was relayed to me is that APCO took longer to finalize the standards and Motorola promised a P2 system to a few customers...but couldn't, hence X2.

It now could become another product in the Motorola portfollio, but the way many grants are/were written, it requires certain industry standards...which X2 as well as OpenSky are not (the codec is, just not trunking format for interop, standards, etc).

My guess is that you will see the majority convert to P2. IIRC, the last one or two APX firmware releases stated that its brings them in line with the P2 standards, but would have to look at the exact wording.

Marc, when did you go west?
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Old 11-10-2011, 2:47 PM
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About a year or so ago, came to implement houstons new X2/P2 system. I know firsthand what it takes to convert a system from X2 to P2 and its alot more than you would think. In addition to having to uplift the whole systems release version, depending on what version you launch from would require additional hardware at the sites.

Subscribers on the other hand are easy, if you already purchased X2 TDMA, uplifting it to FW 6.0 with CPS 6.0 gives you both X2 and P2 TDMA.
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Old 11-10-2011, 3:41 PM
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Grem467, thank you for the detailed information. This is the first concise (other than a guess) at the differences I have seen to date, of all the threads I've read on this site.
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Old 11-10-2011, 3:46 PM
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I agree with Dave - thanks Grem - it looks like you have posted some useful info for a lot of people!!!

I asked above how one would ever know if a system was X2 or TDMA. I am sure the emission designator on the license would be one way. Other than that, you need to know the inner workings of the GTR or the APX equipment configurations in said system.

That said, I have only one more observation... the county I live in is running an X2 system but it doesn't appear they are licensed for that emission designator -- so even that wouldnt help someone update the database as suggested by the OP.

As a follow up, and two throw in .02 worth to the conversation, my somwhat deduced and uneducated guess is that my PSR800 will work on Phase II since the front end of these scanners arent like that of a typical high dollar transceiver; such that grem467 and loco-lee are both really correct, the 9K80D7W and the 8K70D7W are the same except for the bandwidth -- both have the 'D7W' suffix (which indicates the same modulation "D", the same two slots "7" and the same 'combined' type of information to be transmitted "W").
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Old 11-10-2011, 4:56 PM
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Originally Posted by c5corvette View Post
That said, I have only one more observation... the county I live in is running an X2 system but it doesn't appear they are licensed for that emission designator -- so even that wouldnt help someone update the database as suggested by the OP.
I never suggested reliance on the emission designators on the FCC license to make any determination. I've come across entirely too many FCC licenses that contained inaccurate information because they were never updated. What I did say was that "those with intimate knowledge of the system" might well submit the pertinent information to the DB. As one of those people with intimate knowledge of a local system currently being built out, as soon as the system is online and I add it to the DB, I'd be sure to note that it is in fact a true Phase II TDMA system, not X2-TDMA. Surely I'm not the only member of RR who possesses such "inside information". You seem to be stuck on the idea that the information in the DB only comes from casual listeners who have no real working knowledge of what they're listening to. I disagree wholeheartedly.
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