Phase II trunking monitoring on Conv

[123]

Has anyone tried to monitor Phase II on conv. ?
Is there a way to switch between phase I and II protocols on Conv P25 ?

I am using a APX 7000 and still new to the 3.00 CPS

[akardam]

Well, according to Motorola (and as far as I can verify from poking around in the CPS), TDMA on the APX is limited to trunking, so you're almost certainly not going to do it with an APX.

There is no scanner yet that I'm aware of that can do trunk tracking on a P25 Phase II system, although I suspect it's only a matter of time before someone comes out with it. The one thing I don't yet know about Phase II is if the control channel is still on Phase I or not - I suspect it is, because Motorola has the ability to setup their Phase II systems in essentially mixed mode - Phase I and Phase II subscribers can exist on the same system.

Now, there's rumors that Motorola is bringing P25 capability to the MotoTRBO radios at some point in the future. Whether this will include any P25 trunking capability, or more to the point Phase II capability, or even eventually the ability to do Phase II on conventional (just like P25 Phase I works on conventional) remains to be seen.

I guess the old addage "go buy a scanner" doesn't really apply here, yet...

[Wowbagger]

Well, according to Motorola (and as far as I can verify from poking around in the CPS), TDMA on the APX is limited to trunking, so you're almost certainly not going to do it with an APX.

To clarify: you pretty much CANNOT do TDMA systems without a control channel. Since you are multiplexing the signal in the time domain (hence the name), your radio MUST transmit precisely within its allocated time slot, which means your radio has to have SOMETHING to synchronize to in order to make that determination. That "something" has to always be there, and be available to all radios. That's pretty much a description of a control channel.

The one thing I don't yet know about Phase II is if the control channel is still on Phase I or not - I suspect it is, because Motorola has the ability to setup their Phase II systems in essentially mixed mode - Phase I and Phase II subscribers can exist on the same system.

The actual answer is "It depends". You can use a conventional Phase 1 control channel. You can use a Phase 2 channel, and assign one time slot to control and one to traffic. You can use a Phase 2 channel and use both slots for control.

Right now, I suspect the only folks that have even looked at implementing a TDMA control channel work for either Motorola or Aeroflex.

[akardam]

To clarify: you pretty much CANNOT do TDMA systems without a control channel. Since you are multiplexing the signal in the time domain (hence the name), your radio MUST transmit precisely within its allocated time slot, which means your radio has to have SOMETHING to synchronize to in order to make that determination. That "something" has to always be there, and be available to all radios. That's pretty much a description of a control channel.

Any thoughts on what Motorola's doing with the talkaround mode on the TRBO's (does it just fall back to using the entire 12.5khz as a single timeslot?), and how something like Self-Organized TDMA (as used by marine AIS, among other things) might play into the LMR market?

[Wowbagger]

Any thoughts on what Motorola's doing with the talkaround mode on the TRBO's (does it just fall back to using the entire 12.5khz as a single timeslot?),

On the nosie.

and how something like Self-Organized TDMA (as used by marine AIS, among other things) might play into the LMR market?

I'd have to look into it more, but I'd guess the following issues would be important:
1) the "hidden node" problem. On the water you the only thing that really obstructs the signal is the big round ball we live on. On land you pick up quite a few more blocking items, so you get more hidden nodes you have to somehow co-ordinate.
2) Density: again, on the wet stuff you get fewer users per unit area than on the dry stuff.
3) Velocity: part of what makes TDMA tricky is that your TX delay on a timeslot varies as distance. It's hard enough to solve when the nodes aren't moving a lot from burst to burst. Things tend to move faster on land.

[Astro Spectra]

And not to mention Tetra DMO modes in all their glory (DMO to DMO, DMO repeater, DMO dual watch, and DMO gateway).

TDMA simplex, love it!

[MattSR]

Try this little beauty out --> http://forums.radioreference.com/trunki ... belib.html

It lets you monitor Phase two traffic using a disc tapped scanner - though you will need Linux to use it.

[Jim202]

Isn't there a better way to get the files rather than being harassed by some stupid quize?

Try this little beauty out --> http://forums.radioreference.com/trunki ... belib.html

It lets you monitor Phase two traffic using a disc tapped scanner - though you will need Linux to use it.

[MattSR]

Yeah, did you read the rest of the thread? Theres links at the end to the new version hosted on a decent file sharing site.

[Jim202]

One file can be had. The second one still has that :o site and the stupid quiz. Guess this just isn't worth the trouble.

We have one of the TDMA Motorola trunking sites near by and thought it would be worth the effort. But not with all this download crap in the way.

Jim

Yeah, did you read the rest of the thread? Theres links at the end to the new version hosted on a decent file sharing site.

[123]

Download the voice samples he has, Phase I sounds good, but phase II audio sounds like crap.

[MattSR]

One file can be had. The second one still has that site and the stupid quiz. Guess this just isn't worth the trouble.

We have one of the TDMA Motorola trunking sites near by and thought it would be worth the effort. But not with all this download crap in the way.

Jim

Yeah, did you read the rest of the thread? Theres links at the end to the new version hosted on a decent file sharing site.

I found both links to the easy download site no worries. Took me about 10 seconds

http://forums.radioreference.com/trunki ... ost1285836

[MattSR]

And the author has created a wiki page ---> http://wiki.radioreference.com/index.php/DSD

[JohnG]

which means your radio has to have SOMETHING to synchronize to in order to make that determination. That "something" has to always be there, and be available to all radios. That's pretty much a description of a control channel.

The Phase 2 standard has two methods that can be used. Synchronization can be done on the Phase 2 voice channel or optionally on the control channel. Using the control channel SYNC_BCST OSP is not required by the standard.

The actual answer is "It depends". You can use a conventional Phase 1 control channel. You can use a Phase 2 channel, and assign one time slot to control and one to traffic. You can use a Phase 2 channel and use both slots for control.

All Phase 2 systems for now will use the Phase 1 control channel with just a very few new or modified ISPs and OSPs. The Phase 2 slotted control channel is a "future item" and is not enabled in current Phase 2 standards. The only advantage with a slotted control channel is for systems that include a control and a voice channel on a single carrier and who don't care about interoperability with existing phase 1 subscribers.