Why P25 phase II instead of DMR tier 3?

[knockoffham]

I know that this thread will probably cause fights and be shut down, but that's not my intention... How come, in the US, public safety has for the most part ignored DMR tier II/III and instead gone to P25 phase 2? The spectral efficiency is the same, the audio quality is the same (as far as I know), and both have voice and data modes. Is it because of hardware encryption? I am guessing not, since when P25 was first pushed, people did not care as much. Or is it just because the push for P25 happened before DMR? If DMR radios were made to the same standards as public safety would this still be the case? Is it because of sales reps convincing subscribers that for whatever reason public safety tech and commercial tech need to be totally different? Is it just because P25 was more of a US project and DMR was more European? As someone who does not know a ton, right now it seems to me like public safety could use DMR tier-3 systems with IP multi-site link instead of P25 phase II without real tradeoffs, and the equipment would be cheaper, however I feel if this were true it would be talked about more. To keep this on topic I'd like to stick to P25 phase II vs DMR tier II/III, no TETRA or dPMR. I just want some knowledge and maybe background info. Thank you

 

[KevinC]

Before it goes down that road, this is not going to turn into a Motorola (or any other manufacturer) bashing thread, One warning...carry on...

 

[mmckenna]

P25 was in development before DMR came along. Money had already been invested and there were a lot of P25 users already established. Feds and others adopted P25 as the standard for interoperability (band choices aside) and it just continued on from there.

Idea was that if everyone used P25, it would drive prices down and make it more affordable for others. That obviously hasn't happened.

 

[DeoVindice]

DMR equipment generally has not been built to a standard acceptable for safety-critical applications. This is gradually changing but will have been a factor in past selections. Public safety grade DMR equipment exists now, much of it utilizing the same hardware as P25 equipment. Multiprotocol shakes things up even more.

Grant eligibility is probably the biggest factor, and interoperability concerns as mmckenna stated.

 

[kayn1n32008]

One big issue with DMR, encryption was an after thought. When using RC4 or AES encryption, there is a voice quality hit because of how it is implemented in DMR. Voice quality is not degraded at all using P25 and AES/RC4/DES encryption.

In Motorola XPR radios, AES/RC4 is implemented in software, and keys are not securely stored

 

[K6GBW]

The simple answer is that way back in the day APCO had to pick a digital format to get everyone on the same page. At the time, they chose P25. Since then the Federal Government occassionally offers grants for equipment and it has to be P25. All this is an effort to make sure everyone is compatible. It works to a degree, but Motorola pushes the cost of P25 equipment so high that sometimes smaller agencies and agencies that are public safety adjacent end up buying DMR. Frankly there's nothing wrong with DMR, it works fine. But when you have DMR and your neighboring agency is on P25 it can be a pain. Most areas get around this by simply creating mutual aid channels that are anolag FM. At my Agency we were FM, the other agency around us was P25 and the largest hospital we covered had a huge security force using DMR. Not ideal, but we managed.

 

[RRR]

Grant eligibility is probably the biggest factor, and interoperability concerns as mmckenna stated.

Where are these grants now? Particularly for county and city public safety agencies?

I was part of an RFP review team for a county radio system not long ago, and there were no grants to be found for P25. Went DMR instead, much cheaper, and just as good.

 

[mancow]

Where are these grants now? Particularly for county and city public safety agencies?

I was part of an RFP review team for a county radio system not long ago, and there were no grants to be found for P25. Went DMR instead, much cheaper, and just as good.

They are generally only available to those that don't need them.

 

[jeepsandradios]

My department recied AFG grant to replace 40 portables. I know many departments who have applied for that grant and gotten it for radios. Nomally your county or state can help locate the proper grants.

 

[mmckenna]

Where are these grants now? Particularly for county and city public safety agencies?

I was part of an RFP review team for a county radio system not long ago, and there were no grants to be found for P25. Went DMR instead, much cheaper, and just as good.

They are out there at the DHS. I helped write a grant request for $300K late last year, and it was awarded earlier this year.

 

[Project25_MASTR]

Long story short, the P25 standard has been around longer and has heavy emphasis on backwards compatibility but here's some quick bullet points.

• P25's CAI was developed in the 90's and companies such as Motorola, Ma/COM and EF Johnson began shipping radios capable of supporting the CAI by 1998. Standard defined trunking (not just P16 with a P25 CAI) and Phase 2 would continue to develop and deploy over the next 15 years.
• DMR Tier 2 was finalized in 2005 and many manufacturers didn't begin offering Tier 2 capable radios until 2006 or 2007. Tier 3 wasn't finalized until 2012.
• P25 has always focused on backwards compatibility. Services on the CAI can coexist on the same repeater as analog services for conventional operation (which also requires all P25 radios to support analog which is something not required for DMR). P25 Phase 2 systems can allow Phase 1 only radios to operate on the system. Even though Tier 3 is heavily based off of MPT-1327 signaling, there is no analog to digital interoperability.
• DMR Tier 3 is a 4FSK TDMA based protocol that operates at a overall data rate of 9600 bps.
• P25 Phase 2 has a C4FM or CQPSK 9600 bps control channel (excluding TDMA CC capability), H-DQPSK downlink (repeater transmit) at 12000 bps, H-CPM uplink (subscriber transmit) at 6000 bps.

 

[KE4ZNR]

Something else to consider: Mutual Aid.

Every mutual aid radio system around our system is P25. DMR is mostly used for businesses in this area. To easily maintain mutual aid capability it made sense to stay P25 when we upgraded from 4.1 years ago.

In effect changing to a DMR system would have put us on a walled off island.

 

[speedway_navigator]

Carol and Iggy at JPS would say they can solve mutual aid with their patching equipment.
Twice this week I've heard our county PD dispatch keeping local units advised on a state police pursuit but no patching was done. Many Indiana agencies are on the state wide system so it should be easier than disparate ones.

I guess a similar argument could be made for TETRA vs P25 phase 2. Wouldn't 4 TETRA repeaters give the same talk path capability as 8 phase 2 units? If TETRA repeaters are similar in price that would seem to me to be an advantage. I wonder if TETRA repeaters are more energy efficient on a talk path basis since they have double the capacity per unit, that would keep the green folks happy, if that's possible.

 

[MTS2000des]

P25 was designed for public safety from the ground up. From subscriber to FNE, it was purpose built for reliability and availability, with safety of life at the center of it.

DMR is a commercial standard meant to replace legacy analog LMR for business radio users. It's cost cutter design leaves out many things like failsoft, site trunking, ruthless preemption et al that at least on our Linked Cap Plus system are not there. It's great for school buses, public works, security guards, etc but it is not a drop in replacement for a purpose built P25 network.

 

[Low-Band]

As an end-user of both DMR and P25 Phase2 on a daily basis, I notice a big difference in voice quality between the two technologies. The P25 sounds more natural, whereas the DMR sounds more 'tinney'

Is the slight difference in voice quality worth the cost difference of 4~6 times in equipment...???
I don't know.
As a end-user (who doesn't see or care about the $$$), I would pick P25 Phase2. I wish we could move all of our agencies to P25.

I have some technical presumptions on why there is a difference in voice quality since they are both TDMA technologies, but I am going to hold back because I haven't been able to get the hard facts to prove it. Maybe others here can share why the difference in voice quality.

 

[K6GBW]

I've used both P25 and DMR extensively. If they are set up right I don't think one sounds better than the other. They both sound like crap when they drop off and artifact. DMR uses about half the bandwidth and can run two voice channels in the space of one P25 channel. I was a working cop for over thirty years. I started when we had low band and no hand held radios and whenever I hear this stuff about radio saving your life I just laugh. If you are depending on an electronic device to save your life then you've made a grave error is judgement. We were trained to NOT depend on the radio and we expected it to fail on us. As for DMR vs P25, I think they're both fine. Honestly, if I was running a small agency I'd probably opt for DMR soley because all manufacturers charge an outragous amount of money to provide a radio that does fifty times more than most agencies need. At the end of my career we had APX7000 portables that did thousands of channels, encryption, sent messages and all that doodad stuff. We ended up using them for two channels and a single mutual aid channel. Then I had to figure out cost replacements when one of my knuckheads would drive off with one on the top of the car. Much easier to maintain equipment when its afordable.

 

[RRR]

DMR uses about half the bandwidth and can run two voice channels in the space of one P25 channel.

Except Phase2 P25, which is basically the same as DMR, as far as how it works.

 

[Low-Band]

@K6GBW I agree with all your points you mentioned.

I do want to clarify that OP specifically mentioned P25 Phase2 which is also TDMA technology.

DMR uses about half the bandwidth and can run two voice channels in the space of one P25 channel.

So both DMR and P25 Phase2 are TDMA and have the same spectral efficiency.
2 voice talkpaths per one 12.5kHz channel bandwidth.

 

[RRR]

Actually, it's 2, 12.5khz talkpaths in one 25khz bandwidth

 

[KevinC]

Actually, it's 2, 12.5khz talkpaths in one 25khz bandwidth

You sure about that? I always thought it was 2 12.5 Khz talkpaths in one 12.5 kHz bandwidth...but I could be wrong.