dPMR FAQs

The content of this page aims to address misconceptions and provide answers to some of the most common questions asked about the dPMR technology and its application.

It is our intention to present a neutral and balanced view of the respective narrowband technologies and also correct misrepresentations and misunderstandings arising from opinions and materials published and in circulation in the public domain. This page has been prepared by the dPMR® Association Marketing Working Group with the full consensus and approval of the member companies. The dPMR® Association has checked the content for accuracy but reserves the right to amend and/or correct any part of this page without notice or obligation.

General Questions

All you need to know about dPMR.

We welcome membership enquiries from all stakeholder categories. That means everyone from Manufacturers, Application Developers, System Integrators, Resellers and Regulators right through to Test Equipment Manufacturers and Test Houses and End-Users.

Please get in touch through the contact form and we’ll guide you through the application process.

dPMR was also developed to avoid IPR and again, reduce the total cost for both the manufacturer and ultimately, the end user. A statement about dPMR and IPR can be found on the website. No licenses are required for developing dPMR either. Again, the dPMR Association can provide advice to prospective developers on this subject. However, it is public knowledge that a license is required to develop DMR, although the details require an NDA.

There have been comments over the years that dPMR™ is a low cost “non-professional” orientated system. This should not to be confused with the original intention of dPMR™ being conceived as a “low cost, low complexity” protocol. This means that the technology was largely achieved by using existing FM hardware engineering architecture. Also, as explained particularly in the text and diagrams on the pages ‘dPMR: a brief overview’ and ‘Spectrum Efficiency’, each system offers basically the same level of functions, trunking and networking capability. As with the “Which is better?” question, the answer is “the system that best suits the end user’s needs”.

Other Questions

The answers on most common questions are described below.

This should probably be clarified before anything else. To keep things simple, narrowband in its current form would refer to the use of 12.5 kHz channels for two-way PMR/LMR radio communication. However, as 6.25 kHz technologies exist, these would be considered “ultra-narrowband” or “very narrowband”.

Historically, professional two-way radio has dealt with the problem of congested spectrum/channels by narrowing the channel spacing. I.e. 50 kHz  25 kHz  12.5 kHz  6.25 kHz. The DMR system is often quoted as being 6.25 kHz “equivalent”, and dPMR™ or NXDN™ are true 6.25 kHz. Basically what this means is that the 2-slot TDMA architecture of DMR provides the equivalent of two 6.25 kHz voice or data paths in a 12.5 kHz channel and the FDMA systems’ channel spacing is 6.25 kHz.

This was a pertinent question in the beginning of the migration to digital narrow band LMR/PMR technologies. In the end, both FDMA and TDMA digital technologies have been accepted in the market based on the features and advantages provided.

Notice we have not used “digital” with narrowband. This is because 12.5kHz analogue FM is considered narrowband technology based on the explanation in A1 above, and thus the first type of narrowband technology available. Diagrams are provided for the systems relevant to the discussion in this document with references to other systems as required.

Analogue Narrowband:
Good old reliable FM: As mentioned above, analogue FM 12.5 kHz products have been available for many years now, and fit the description of the current narrowband channel spacing standard of 12.5 kHz.
Digital Narrowband:
dPMR™: dPMR™ is a digital 6.25 kHz FDMA based protocol described in the ETSI technical standards TS 102 490 and TS 102 658. Details of what dPMR™ is and can do, can be found on the dPMR™ Association website, but the basic structure of the dPMR™ standards suite is shown in the graphic below.


As the diagram shows, dPMR™ is a full featured system capable of providing communications solutions ranging from license-free all the way up to multi-site trunking networks.



NXDN™: NXDN™ is an open digital 12.5 kHz or 6.25 kHz FDMA based protocol described in the NXDN™ suite of standards. Details of what NXDN™ is and can do, can be found on the NXDN™ Forum website, (http://www.nxdn-forum.com/) but the basic structure of the NXDN™ standards suite is shown in the graphic below.



As the diagram shows, NXDN™ is a full featured system capable of providing flexible trunking solutions in dedicated control channel format or distributed logic format for small, medium and large networks.



DMR: DMR is a digital 12.5 kHz 2-slot TDMA based protocol described in the ETSI technical standard TS 102 361. Details of what DMR is and can do, can be found on the DMR Association website (http://dmrassociation.org/), but the basic structure of the DMR standards suite is shown in the graphic below.


As the diagram shows, DMR is a full featured system capable of providing communications solutions ranging from license-free all the way up to multi-site trunking networks.
Other Digital Systems:
APCO Project 25: APCO P25 is a digital standard targeted mainly for the United States public safety market, but has implementation worldwide. The current Phase 1 part of the standard is a digital 12.5 kHz FDMA based protocol described in the TIA APCO P25 standards. A Phase 2 standard which is a 2-slot TDMA 12.5 kHz protocol is also available.

Tetrapol: This is a 12.5 kHz FDMA digital standard that is also targeted for the public safety market as well as high-end commercial markets.

Tetra:This is a digital 25 kHz 4-slot TDMA based protocol described in the ETSI EN 300 392 suite of standards. Tetra is also targeted for the public safety market as well as high-end commercial markets.

Japanese and Chinese standards: ARIB standards T-98 and T-102 are NXDN™ based 6.25 kHz FDMA standards that are available in the Japanese domestic market.
China has also developed a digital standard called Police Digital Trunking (PDT), which is a 12.5 kHz TDMA based standard. They have also created two separate Business and Industry digital standards, based on the dPMR™ and DMR ETSI protocols, but tailored to the Chinese market.

The dPMR™ Association website has a comprehensive Product Showcase detailing the dPMR™ products and services currently available.

DISCLAIMER

The web page and document have been prepared by the dPMR Association as a reference document. The information in this document has been carefully checked and is believed to be correct and accurate. However, the dPMR Association assumes no responsibility for inaccuracies or mistakes. Document Revisions: The dPMR Association reserves the right to make changes to the content of this web page / document at any time without notice or obligation. Trademarks dPMR and the dPMR logo are registered trademarks of the dPMR Association in Europe, the United States, Japan, China and/or other countries. NXDN is a trademark of Icom Inc. and Kenwood Corporation. All other products or brands are registered trademarks or trademarks of their respective holders.

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The dPMR Association was established in 2007 and provides a forum for interested parties to contribute their expertise.

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