DMR vs P25

[alphaprime]

Infrastructure:

• DMR has a Inter-System interface called AIS where P25's is called ISSI. AIS and ISSI can be used to interconnect different systems, even manufactured by different vendors.
• P25 has a standard for integrating consoles to any vendor's system called CSSI. DMR has no equivalent.
• P25 has a standard command/control IP protocol for repeaters called DFSI. DMR has no equivalent. DFSI is used by several manufacturers to control repeaters for both conventional and trunking applications (so you can literally have one P25 trunking controller at a site interfaced to multiple repeaters from various vendors). DFSI can also be used in conventional applications to with a console to make a repeater/base function as a high powered, remote transceiver.

Actually, DMR AIS also serves as a standards interface protocol for console systems. Good luck using DFSI to control different brands of repeaters from a system controller.

 

[Project25_MASTR]

Actually, DMR AIS also serves as a standards interface protocol for console systems. Good luck using DFSI to control different brands of repeaters from a system controller.

It's already been done with EF Johnson's Atlas 8000 controllers. EFJ's 3800/4x00 and 1200 series repeaters, check. Codan's MT-4E and Cascade repeaters, check. Tait TB9x00 repeaters, check (I've actually got the TB9100's EFJ used for testing). RF Technologies Eclipse 2/3, check.

What I don't know is if it has been tested with Harris Bravo Two47 repeaters, Motorola GTR8000 (which does support DFSI supposedly), Motorola Quantar through the RIC-M. Though in theory it should function but that's the overall goal...show it is possible to build a system where every repeater is from a different vendor.

 

[a727469]

While all this technical stuff is interesting to me and others here, an example of real life DMR unacceptable performance in my area is interesting.
The county sheriff agency converted to DMR awhile back and the had nothing but trouble with voice clarity and range. The radio techs worked on it for months but the sheriff had so many complaints from staff and examples of public safety being compromised that he ordered everything back to analog and it remains there today. No talk if p25 either.
I must assume the techs did the best they could and I have no knowledge of what brand equipment they had, but it did not work. Also, I do not know if they are working on it in the background but it has been back to analog since August of 2023.

 

[mmckenna]

I must assume the techs did the best they could and I have no knowledge of what brand equipment they had,

Assume is a strong word.

 

[rf_patriot200]

I have been trying to find differences between P25 and DMR, why do public safety agencies tend to use P25 more? From my experience they both sound the same, and do the same, plus DMR is cheaper..

P25 is C4FM and easier to program, with better audio fidelity on P1. DMR is TDMA which has a curve, when it comes to programming and has questionable audio quality, with periodic packet loss. DMR is cheaper, if you're not picky, and There is good used P25 gear out there, that can be cheaper.

 

[a727469]

Assume is a strong word.

You are correct. I based it on how I would work on a problem😀

 

[alphaprime]

It's already been done with EF Johnson's Atlas 8000 controllers. EFJ's 3800/4x00 and 1200 series repeaters, check. Codan's MT-4E and Cascade repeaters, check. Tait TB9x00 repeaters, check (I've actually got the TB9100's EFJ used for testing). RF Technologies Eclipse 2/3, check.

What I don't know is if it has been tested with Harris Bravo Two47 repeaters, Motorola GTR8000 (which does support DFSI supposedly), Motorola Quantar through the RIC-M. Though in theory it should function but that's the overall goal...show it is possible to build a system where every repeater is from a different vendor.

To be honest, I was thinking Harris and Motorola. Glad to hear about the Johnson, Codan, and Tait compatibility.

 

[kayn1n32008]

P25 is C4FM and easier to program, with better audio fidelity on P1.

Of course it has better audio fidelity, it has twice the payload as DMR for voice data. P25 uses a variety of PSK, in simulcast to increase maxim delay spread, where as C4FM is much less forgiving in delay spread.

DMR is TDMA which has a curve, when it comes to programming

If you are coming from conventional analogue environment, and have never programmed ASTRO25 gear, even only conventional P25, has a pretty steep learning curve, but no less than DMR. It really depends on the initiative of the person programming, and how willing they are to asking questions and how actively they are willing to learn.

and has questionable audio quality,

I've used a vendor locked DMR system on LMR(Con+ and ham(Cap+). Both systems sounded decent, because the audio was set up by competent technicians. Not just thrown together and hope for the best

with periodic packet loss.

All depends on how the coverage and(if it's a multi site, linked system) the quality of the design and imementation of the back haul between the sites. But really that goes for ANY system.

DMR is cheaper, if you're not picky, and There is good used P25 gear out there, that can be cheaper.

DMR, P25, NXDN and analogue ALL have their place where they make sense.

 

[kayn1n32008]

While all this technical stuff is interesting to me and others here, an example of real life DMR unacceptable performance in my area is interesting.
The county sheriff agency converted to DMR awhile back and the had nothing but trouble with voice clarity and range. The radio techs worked on it for months but the sheriff had so many complaints from staff and examples of public safety being compromised that he ordered everything back to analog and it remains there today.

So is it an issue of the vendor over selling the audio quality of DMR or thay they were usi g stock audio gain and AGC settings?

As for range problems, there is so much information missing. Did the vendor sales team over sell the coverage? All things being equal, DMR should have an edge in talk in range over analogue with a much better DAQ. Was DAQ explained and qualified to the customer in a way they understood? If it was a rip and replace, using existing feedline and antennas, were they tested before DMR was deployed?

Was the vendor technically incompetent?

Was the vendor trained and competent in how to properly set up audio profiles of the DMR radios?

Did the users have ANY training on the differences in the audio chain between an analogue radio and a digital one and that there is a proper way to use it?

Blaming the format is a cop-out, there are likely one or more factors in this 'failure' that is likely NOT the fault of the DMR protocol.

 

[mmckenna]

While all this technical stuff is interesting to me and others here, an example of real life DMR unacceptable performance in my area is interesting.
The county sheriff agency converted to DMR awhile back and the had nothing but trouble with voice clarity and range. The radio techs worked on it for months but the sheriff had so many complaints from staff and examples of public safety being compromised that he ordered everything back to analog and it remains there today. No talk if p25 either.

Having worked on several radio system projects, this says a couple of things:

The Sheriff probably didn't hire a consultant. A radio shop is -not- a consultant. Many, many radio shops will claim they are. They aren't. Expecting the radio shop to design the system is a major failure. External, third party, vendor agnostic consultants are the way to go. But they cost money, and the radio shop will always insist they can do it themselves.

Sounds almost like someone just swapped out analog repeaters with DMR repeaters and called it a day.

Letting the radio shop design the system is another major failure. They are going to do the absolute minimum possible to increase profits. Looks like that backfired.

The Sheriffs office probably didn't have an appropriate budget. A good consultant would have included the budget in the design of the system. The system would have been properly designed. Coverage/propagation software is quite accurate if used correctly. Major coverage issues shouldn't be a surprise.

Not having a trained technician set up the audio is another bad thing. I spent a lot of time playing with the audio settings on my NXDN trunked system, and spent a lot of time consulting with the manufacturer. Audio sounds really good, but it's 12.5KHz FDMA digital, not a 6.25KHz slice.

They were smart to cut their losses and roll back. That's the sign that they focusing on doing what was right and not letting egos get in the way. Often leadership and/or a shop won't want to admit failure and will do anything rather than admit they need to roll back. Been there, done that, learned the lesson. Rolling back should -always- an option.

This isn't the failure of digital. It's the 6 P's: Poor Planning Produces Piss Poor Performance.

 

[kg4icg]

P25 Phase 1 is FDMA, P25 Phase 2 is TDMA in c4fm format

 

[a727469]

Having worked on several radio system projects, this says a couple of things:

The Sheriff probably didn't hire a consultant. A radio shop is -not- a consultant. Many, many radio shops will claim they are. They aren't. Expecting the radio shop to design the system is a major failure. External, third party, vendor agnostic consultants are the way to go. But they cost money, and the radio shop will always insist they can do it themselves.

Sounds almost like someone just swapped out analog repeaters with DMR repeaters and called it a day.

Letting the radio shop design the system is another major failure. They are going to do the absolute minimum possible to increase profits. Looks like that backfired.

The Sheriffs office probably didn't have an appropriate budget. A good consultant would have included the budget in the design of the system. The system would have been properly designed. Coverage/propagation software is quite accurate if used correctly. Major coverage issues shouldn't be a surprise.

Not having a trained technician set up the audio is another bad thing. I spent a lot of time playing with the audio settings on my NXDN trunked system, and spent a lot of time consulting with the manufacturer. Audio sounds really good, but it's 12.5KHz FDMA digital, not a 6.25KHz slice.

They were smart to cut their losses and roll back. That's the sign that they focusing on doing what was right and not letting egos get in the way. Often leadership and/or a shop won't want to admit failure and will do anything rather than admit they need to roll back. Been there, done that, learned the lesson. Rolling back should -always- an option.

This isn't the failure of digital. It's the 6 P's: Poor Planning Produces Piss Poor Performance.

Many of these points are certainly possible, but I have no knowledge as to the “real” reasons. I would like to think they did all the right things but we all know that errors are made in planning and execution of anything like this. At this point, I have heard nothing further, however, another police department in the next county just went dmr but they are encrypted, unusual for this area, but will be interesting to see how it goes.

 

[a727469]

So is it an issue of the vendor over selling the audio quality of DMR or thay they were usi g stock audio gain and AGC settings?

As for range problems, there is so much information missing. Did the vendor sales team over sell the coverage? All things being equal, DMR should have an edge in talk in range over analogue with a much better DAQ. Was DAQ explained and qualified to the customer in a way they understood? If it was a rip and replace, using existing feedline and antennas, were they tested before DMR was deployed?

Was the vendor technically incompetent?

Was the vendor trained and competent in how to properly set up audio profiles of the DMR radios?

Did the users have ANY training on the differences in the audio chain between an analogue radio and a digital one and that there is a proper way to use it?

Blaming the format is a cop-out, there are likely one or more factors in this 'failure' that is likely NOT the fault of the DMR protocol.

Again, all excellent points, but as I stated, I have no inside knowledge, but I do know that for months I heard techs testing while the system was in use trying to adjust or fix, although obviously not working.

 

[mmckenna]

Many of these points are certainly possible, but I have no knowledge as to the “real” reasons.

Right, none of us know.
But those of us that have been doing this for a few decades can make an educated guess. Proper design, including using propagation analysis tools, would prevent surprises. Other than not having a competent consultant or having a totally unrealistic budget, there's no reason why there should have been any major coverage impact. The current tools work that well. Real propagation tools (not the free hobby versions) will take into account the differences between analog, DMR, P25p1/p2, simulcast interference, antenna gain, height, cable loss, transmitter power, antenna down tilt, mobile antenna gain/height, portable antenna gain, body loss, topography, noise floor, buildings, ground clutter, and give a propagation map showing expected performance down to a 1 meter by 1 meter square. We recently used it for a design and found it to be extremely accurate.

 

[GTR8000]

P25 Phase 1 is FDMA, P25 Phase 2 is TDMA in c4fm format

P25 Phase II TDMA uses H-DQPSK modulation, not C4FM. Even at standalone (ASR)/non-simulcast sites where the FDMA control channel is using C4FM modulation, the TDMA traffic channels will always use H-DQPSK modulation.

 

[rf_patriot200]

P25 Phase 1 is FDMA, P25 Phase 2 is TDMA in c4fm format

If you look at the Moto Software, Apco 25 Phase 1 is also C4FM.

 

[rf_patriot200]

If you look at the Moto Software, Apco 25 Phase 1 is also C4FM.

P25 Phase II TDMA uses H-DQPSK modulation, not C4FM. Even at standalone (ASR)/non-simulcast sites where the FDMA control channel is using C4FM modulation, the TDMA traffic channels will always use H-DQPSK modulation.

When programming my Xts 2500. the software indicates C4FM, and the 2500 is Phase 1 only. Think what you like.

 

[Project25_MASTR]

When programming my Xts 2500. the software indicates C4FM, and the 2500 is Phase 1 only. Think what you like.

Phase 1 (FDMA) is C4FM…unless you are dealing with simulcast then it can be CQPSK (or LSM as some older Motorola radios put it). Go pull up a R2670 service monitor, P25 is referred to as (gasp) C4FM/CQPSK even for trunking. Actually, the SU only transmits C4FM on Phase 1.

Phase 2 traditionally uses a C4FM or CQPSK 9600 bps control channel. The TDMA voice channels however are H-DQPSK at 12,000 bps.

That's all GTR is saying (and GTR is in the business of Motorola P25).

 

[rf_patriot200]

Phase 1 (FDMA) is C4FM…unless you are dealing with simulcast then it can be CQPSK (or LSM as some older Motorola radios put it). Go pull up a R2670 service monitor, P25 is referred to as (gasp) C4FM/CQPSK even for trunking. Actually, the SU only transmits C4FM on Phase 1.

Phase 2 traditionally uses a C4FM or CQPSK 9600 bps control channel. The TDMA voice channels however are H-DQPSK at 12,000 bps.

That's all GTR is saying (and GTR is in the business of Motorola P25).

Correct, That I agree with. As for GTR, there's medication for your problem...

 

[RRR]

FDMA = Frequency Division Multiple Access. Understood.

Where is there a system, such as NXDN, that actually makes use of FDMA?

FDMA is 2 talkpaths, literally right beside each other, with virtually no separation, right?