DMR Vs. NXDN

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#1
For businesses, etc, selecting a digital mode, is one mode actually superior to the other?
 

wa8pyr

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#2
For businesses, etc, selecting a digital mode, is one mode actually superior to the other?
I've never noticed much of a difference in audio; primary advantage to DMR is that it allows two talk paths per frequency versus one for NXDN.
 
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#3
JASII - NXDN (iDAS) is superior in everyway to DMR. I suggest you look at the ICOM iDAS video on youtube. DMR is a catchall replacement for Business Radios and Tempoary Operators. It Quickly can update small operators who want Digital Clarity at low cost. where Voice security is not very important , though DMR can Encrypt. its also using a LESS efficient transmission of 12.5 Khz compared with iDAS 6.25 khz FDMA scheme. NXDN can operate in Mixed mode Analog-Digital to allow you to upgrade at YOUR pace. single site / multi site Trunking is Avalable as well. but the Real killer app is the Radios in iDAS are the most Advanced in the Industry, they have Military grade waterfroofing, Bult in GPS and Bluetooth audio, Radio monitoring of the USER, MAN down signaling and Alarms if Radio is no longer moving, another killer app is iDAS radios can connect to IP router, for communications in a 100 story building, in a Gaint Sadium, or a Fleet of Trucks.
 
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#4
IMO NXDN has better audio than DMR. The two users on one RF frequency/pair is an operational advantage, but depends what "business" we are talking about.

AES-256 isn't available on MSI DMR in the USA, unless you're special. OTOH, NXDN support AES-256 natively, and NXDN trunking offers authentication and ends piracy and bootleggers with eBay radios popping up on your system.

Both have pluses and minuses depending on the specific intended application.
 

jaspence

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#5
DMR vs NXDN

The one big difference for amateurs is the number of DMR radios available and their cost. Early FM analog dual band radios were in the $400 plus range when I got my first dual band HT, while a dual band analog/DMR radio can be had around $80 today.
 
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#6
As someone who designs, installs, and troubleshoots digital radio systems for a major manufacturer I would strongly recommend you buy the service and support of the local dealer/installer. I am a trbo fan, but Kenwood and Hyterra have good products as well. In these complex systems, the person installing the system makes it great, good, or poor system. TT
 
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#8
As someone who designs, installs, and troubleshoots digital radio systems for a major manufacturer I would strongly recommend you buy the service and support of the local dealer/installer.
I second this.

When I was ready to retire the Motorola SmartNet system at work, I trialed a MotoTrbo system and an NXDN system.
The NXDN system sounded better.
After coming off nearly 20 years of Motorola, I'd had enough of their service shops and didn't want to put up with them any more. Kenwood bent over backwards to get our business.
That, and at the time, none of the 800MHz MotoTrbo stuff would do NPSPAC channels. Motorola had them blocked. Motorola claimed that if we were using NPSPAC we -had- to use P25. That as the nail in the coffin for them.

As for the dual timeslot thing, that wasn't an issue for us. Having come off a 5 channel SmartNet system I knew I didn't need more than what I had. Wasn't a selling point for us.
 
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#9
As to hardsuit's claims, DMR has all of the feature sets he described in one form or another but it will be heavily dependent on the manufacturer. Motorola, Hytera and Simoco have the most featured rich DMR products on the market right now.

One of the major advantages to Motorola and Hytera DMR systems is the ability to enable pseudo-trunking. While these are vendor proprietary, it allows low budget trunking systems to be built (but there are limitations like the lack of ID databases) but access can still be restricted if planned correctly. The real advantage is for single channel trunking (Simoco also offers this for a single channel) allowing for two voice channels on a single frequency (this should've been part of the DMR Tier 2 spec IMO).

Then there is the true control based trunking systems such as Motorola's (Trident's) now EOL Connect Plus and the systems that follow the Tier 3 standard such as Motorola's Capacity Max (which I'm not fond of), Hytera's T3 solution, Tait/Harris' T3 solution and Simoco's Xd T3 solution (which is my favorite as it's is in a lower price-point than Motorola's multi-site pseudo-trunked solution, Linked Capacity Plus). All of these use authentication as a standard feature in a manner where the SU's serial number is used to validate the SID during the registration process (note, P25 also offers this but majority of the systems out there don't use it).

NXDN on the other hand, has better audio and typically has lower cost equipment. While I've never had the opportunity to physically check, I've also heard reports of better low-signal capabilities compared to DMR. Primary disadvantages to NXDN is a lack of vendors with Icom, Kenwood (who now has a DMR solution as well), and Alinco and the physical channel spacing capabilities. What I mean with that, both Kenwood and Icom advertised the ability to fit two 6.25 kHz channels in 12.5 kHz spectrum (where DMR is 2 times slots on a single 12.5 kHz channel) but what they failed to inform customers about was the fact this physically can't be done on a single cavity combiner and will either require two cavity combiners with physical separation of antennas or a hybrid combiner. So a choice has to be made, do you split your combiner and physically separate your transmit antennas (which may have adverse coverage consequences) or do you take the extra 5 dB loss with the hybrid? This is before even addressing the additional hardware costs for site infrastructure if you need equivalent capacity to a DMR system.

Now like mmckenna said, he went from a Smartnet system (Type II) in a 5 channel configuration to a NXDN system in a 5 channel configuration as he didn't need the extra 5 voice paths a DMR control based trunking system would have offered for the same 5 carriers. Personally, I wouldn't go with either for a large scale trunking system but that's just me.
 
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#10
A problem with the NXDN in urban areas is that licensees are taking up a single .00625 slot rendering the other half of .0125 KHz channels unavailable for analog or DMR users. For railroads or utilities whose coordinators are more specific to those industries, NXDN can be coordinated to more tightly pack the channels.

But for Industrial and Business users, the coordinators don't seem to be paying attention to this, nor concerned.. So although it may seem efficient, in the near term it is not delivering any spectral efficiency advantage. All that results are fewer contiguous 12.5 KHz slots for new systems.

For users that require multiple channels DMR has 2:1 TDMA so only one repeater is required and pseudo trunking can allow a small number of talk groups beyond two. For users that need wide area, IP linking is a cinch and there are vendors providing simulcast as well. There is really nothing not to like about DMR. It runs circles around P25. And yes you can get away from the Motorola brand with DMR.

If you go with DMR try to avoid the proprietary trunking systems and stick with straight tier 2 solutions.
 

KK6ZTE

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#11
When it comes to bang for the buck, you can't beat DMR.

NXDN has it's advantages under certain use cases, but the two talk paths for a single repeater (and associated equipment which cost far more than the repeater) for most users is the deal breaker.
 

redbeard

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#12
I see a lot of fanboi foaming over NXDN and stating of features that make it 'better' leading one to assume the evil competition lacks those features but in reality is untrue.

JASII - NXDN (iDAS) is superior in everyway to DMR. I suggest you look at the ICOM iDAS video on youtube. DMR is a catchall replacement for Business Radios and Tempoary Operators. It Quickly can update small operators who want Digital Clarity at low cost. where Voice security is not very important , though DMR can Encrypt.
Small and 'Temporary' are not words I would use to describe the large multi-state networks being built with MotoTRBO. The jab at security/encryption is somewhat valid with Motorola refusing to offer AES-265 to drive sales toward higher tier products. But do you even need encryption for your needs that nobody has bother to ask for? Basic encryption is included for free and is enough to keep scanner listeners in the dark.

...its also using a LESS efficient transmission of 12.5 Khz compared with iDAS 6.25 khz FDMA scheme. NXDN can operate in Mixed mode Analog-Digital to allow you to upgrade at YOUR pace. single site / multi site Trunking is Avalable as well.
As an end user, are you concerned with spectral efficiency? I doubt it. This is an industry and legislative challenge and doesn't concern the customer. But for the sake of clarity these numbers are more important in terms of cost. To achieve two simulataneous talk paths, you will require only one DMR repeater working on a 12.5 KHz channel. The same two talk paths will require two seperate NXDN repeaters, doubling the hardware cost and even though 6.25 x 2 = 12.5 in reality it will be more like two 12.5 channels due to spacing issues. Mixed mode isn't anything special, the current line of radios mostly all do analog as well and if you are upgrading (which again we do not know your needs) newer radios on the same band could still potentially access legacy analog equipment. Single or multi site trunking (if you need it) is available to both technologies so again no advantage either way.

But the Real killer app is the Radios in iDAS are the most Advanced in the Industry, they have Military grade waterfroofing, Bult in GPS and Bluetooth audio, Radio monitoring of the USER, MAN down signaling and Alarms if Radio is no longer moving, another killer app is iDAS radios can connect to IP router, for communications in a 100 story building, in a Gaint Sadium, or a Fleet of Trucks.
All features available with DMR as well. The Motorola XPR 7000 series is submersible, and rugged to standards IP68/MIL STD 810 C,D,E,F,G, and has intrinsically safe options for hazardous locations. A large new petrochemical plant is being built in my backyard and they have already selected and installed a new Motorola Tier III Capacity Max system for the plant.
 

krokus

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#14
I see a lot of fanboi foaming over NXDN and stating of features that make it 'better' leading one to assume the evil competition lacks those features but in reality is untrue.



Small and 'Temporary' are not words I would use to describe the large multi-state networks being built with MotoTRBO. The jab at security/encryption is somewhat valid with Motorola refusing to offer AES-265 to drive sales toward higher tier products. But do you even need encryption for your needs that nobody has bother to ask for? Basic encryption is included for free and is enough to keep scanner listeners in the dark.



As an end user, are you concerned with spectral efficiency? I doubt it. This is an industry and legislative challenge and doesn't concern the customer. But for the sake of clarity these numbers are more important in terms of cost. To achieve two simulataneous talk paths, you will require only one DMR repeater working on a 12.5 KHz channel. The same two talk paths will require two seperate NXDN repeaters, doubling the hardware cost and even though 6.25 x 2 = 12.5 in reality it will be more like two 12.5 channels due to spacing issues. Mixed mode isn't anything special, the current line of radios mostly all do analog as well and if you are upgrading (which again we do not know your needs) newer radios on the same band could still potentially access legacy analog equipment. Single or multi site trunking (if you need it) is available to both technologies so again no advantage either way.



All features available with DMR as well. The Motorola XPR 7000 series is submersible, and rugged to standards IP68/MIL STD 810 C,D,E,F,G, and has intrinsically safe options for hazardous locations. A large new petrochemical plant is being built in my backyard and they have already selected and installed a new Motorola Tier III Capacity Max system for the plant.
You beat me to it, pointing out that most of those highlights are model specific features, not things tied to the radio's modulation schema.

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redbeard

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#15
You beat me to it, pointing out that most of those highlights are model specific features, not things tied to the radio's modulation schema.

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What triggers me is when in a direct comparison, features common to both choices are touted as superior when in reality both lines share them. It would be like me saying how much better Motorola is for having models that are HazLoc certified.




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#16
I talked to a senior tech and engineer at a Kenwood and Hytera dealer today, they said they see better RX sens (-126 dBm) and range with 6.25kHz channels over DMR. They did acknowledge what's been said here about needing 2 repeaters for 2 channels but said they present this to customers with pros and cons so the customer can make the decision.
 
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#17
I talked to a senior tech and engineer at a Kenwood and Hytera dealer today, they said they see better RX sens (-126 dBm) and range with 6.25kHz channels over DMR. They did acknowledge what's been said here about needing 2 repeaters for 2 channels but said they present this to customers with pros and cons so the customer can make the decision.
You will always see a lower noise floor on a narrower receiver. However the modulation of the transmitter must be reduced to achieve the bandwidth and that impairs fidelity. The digital scheme modulation must be tailored to recover the reduced fidelity.

It would be interesting to see DMR side by side with NXDN to compare intelligibility at the extremes of coverage. I would like to see such a demonstration.

A dealer that sells both technologies is a good resource for a customer.


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krokus

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#18
They did acknowledge what's been said here about needing 2 repeaters for 2 channels but said they present this to customers with pros and cons so the customer can make the decision.
That is a good thing. I hope the dealer mentions that if something happens to a TDMA DMR repeater, you lose both talk paths, as part of the possible cons.



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#19
That is a good thing. I hope the dealer mentions that if something happens to a TDMA DMR repeater, you lose both talk paths, as part of the possible cons.



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You really have to address it as a single repeater, single point of failure issue.

I was out at a customer's last week who was complaining of their radios not working at times. After I finally found the repeaters I noticed something interesting. The two repeaters were Motorola XPR8400s in a two channel Capacity Plus (pseudo-trunking) arrangement both fed by a single UPS. One of them had disabled itself showing a "Power Unleveled Alarm" in RDAC. I began digging into when and how long the problem had been occurring. Turns out, they had been noticing the issue for about 6 months but really though nothing of it until they got busy the week prior due to a new exhibit opening…they were simply busying out but didn't know how to describe it as they had three primary groups trying to use two talk paths.

They were limited by the loss of a repeater but they still had a perceived 95% system availability during that time frame since the system still trunked reliably until they had a large crowd.
 
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#20
That is a good thing. I hope the dealer mentions that if something happens to a TDMA DMR repeater, you lose both talk paths, as part of the possible cons.



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If you lose an FDMA NXDN repeater you have same problem unless you bought a second one. At that point, if you have bought two repeaters for redundancy for either NXDN or DMR, the TDMA DMR system would have twice the talkgroup capacity for same investment.

Next?

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