DMR Digital Mobile Radio
- a summary or overview about the basics of DMR, Digital Mobile Radio technology, the digital radio communications alternative to analogue PMR, professional mobile radio.
Digital Mobile Radio, DMR, is a new standard that has been developed by ETSI defining digital standard for PMR. PMR, an acronym for Professional, Personal, or Private mobile radio is recognised as the term covering radio communications other than mobile telephones.
With the growing need to improve the efficiency of radio communications systems and add new facilities, the move to a digital system is of great importance. Accordingly the new Digital Mobile Radio communications system has been developed to provide affordable digital systems with low complexity with facilities for voice, data and other supplementary services.
Although the Digital Mobile Radio communications system has been defined by ETSI, a European organisation, it is being developed as a worldwide standard which will have a similar take-up to previous analogue radio communications systems such as MPT 1327.
The resulting Digital Mobile Radio technology has been designed to deliver a cost-effective, highly functional communication system for professional mobile radio users, along with an easy upgrade path and multi-vendor interoperability and flexibility. It has been designed to operate within the existing 12.5 kHz channel spacing that is standard for PMR applications. It ahs also been designed to meet the future 6.25 kHz channel equivalence. The DMR standard is designed to operate within the existing 12.5kHz channel spacing used in licensed land mobile frequency bands globally and to meet future regulatory requirements for 6.25kHz channel equivalence.
DMR Digital Mobile Radio basics
The Digital Mobile Radio communications standard has been developed to meet the requirements of many different classes of users. Those developing the standards have looked at the users of existing PMR radio communications systems. They concluded that these users fell broadly into three different categories:
- Domestic and short range industrial users. These users typically need fast, convenient and low cost communications over a limited range. Typically simple low power low cost radios meet their needs admirably.
- Professional users for which radio communications are critical. These applications can be found in organisations that need to communicate with a mobile workforce. They include business sectors such as transportation, construction, manufacturing, energy and utilities. The communications needs vary considerably but they may need to communicate over a restricted area, of they may require communications across a variety of sites or over a much larger region.
- Emergency services for which radio communications are vital. These applications require top reliability communications which need also to be secure. They may also need to be available over a wide area, and may need to be customised to the specific needs of the user. These radio communications networks are costly, but a necessary requirement for these organisations.
In order to meet these needs the ETSI standard for Digital Mobile Radio provides for three different tiers of radio communications systems.
- Tier 1: This is a basic licence free form of digital radio communications system. Its aim is to fill the same slot that is addressed by PMR466.
- Tier 2: This form of the Digital Mobile Radio communications system requires licensed operation and it offers high power levels, peer to peer operation as well as a repeater mode to provide greater coverage.
- Tier 3: This tier of the Digital Mobile Radio communications standard again requires a licence and provides for trunked operation, thereby providing a digital form of the widely used MPT1327 standard.
The Digital Mobile Radio standard provides operation within the existing channel spacing used within the land mobile radio frequency allocations. It thereby provides an easy upgrade path for current users of analogue mobile radio technology.
Digital Mobile Radio and other technologies
It may appear that Digital Mobile radio directly competes with other technologies and therefore may be redundant. However it has been designed to offer unique advantages and fill a market requirement that is not being addressed by other services.
- Unlicensed PMR: This sector of the market requires low cost solutions. The main driver is for improved use of the spectrum which will be provided by the Tier 1 Digital Mobile Radio technology. This will ultimately need to take over from the existing analogue solutions.
- TETRA and Project 25 (P25) : These standards are typically aimed at the market where mission criticality is key and where a variety of different facilities are required. TETRA (Terrestrial Trunked Radio) the standards for which are under ETSI control uses 25 kHz channels and supports many facilities including multiple talk groups on multiple frequencies, including one-to-one, one-to-many and many-to-many calls.
In North America the Telecommunications Industry Association, TIA has developed a system with the name Project 25 (P25) which has similar capabilities to TETRA but uses 12.5 kHz channel spacing with FDMA for Phase I although Phase II will use a two slot TDMA system for digital trunked radio
Both these systems are very sophisticated and require a complex infrastructure which enable them to provide a highly reliable service. Digital Mobile Radio is able to offer a lower cost alternative that will be more applicable to lower end applications.
- MPT1327 and dPMR : The majority of the PMR business is seen in between the low end domestic and small business short range communications and the high end mission critical region. In this arena, cost is a critical element and all the facilities offered by TETRA and P25 are not needed. Digital Mobile Radio is seen as offering a key improvement in this area. It provides increased capacity and spectrum efficiency usage along with improved facilities and reliability. While analogue radios and MPT1327 for trunked radio have provided very fgood services there is a need to move to more efficient digital radio options. Accordingly Digital Mobile Radio technology is seen as providing the solution for new users and those needing to upgrade.
The foundations for the DMR Association were laid in 2005 when a group of companies that were potential suppliers of DMR equipment signed a Memorandum of Understanding to support ETSI in the establishment of Digital Mobile Radio as an open standard. These suppliers included: Fylde Micro, Icom, Kenwood, Motorola, Selex, Tait, and Vertex Standard.
The standardisation work was undertaken such that the DMR standards were overseen by ETSI and the standards and themselves were issued by them.
Then in 2009, the original signatories of the original MOU set up the DMR Association (www.dmrassociation.org) with its aims to provide interoperability between Digital Mobile Radio vendors equipment and to provide information about the DMR standard.
ETSI Digital Mobile Radio standards
Digital Mobile Radio technology is defined under the relevant ETSI standards. These include the following:
- TR 102 398 : This technical report provides an introduction to Digital Mobile Radio technology
- TS 102 362 parts 1 to 3: These technical specifications define Digital Mobile Radio protocol conformance testing and test suites
- TS 102 490: This technical specification defines the narrow-band or 'digital PMR' protocol.
- Technical Report TR 102 335-1: Digital Mobile Radio System Reference document for Tier 1 DMR.
- TR 102 335-2: Digital Mobile Radio System Reference document for Tier 2 DMR (licensed).
Digital Mobile Radio Summary
Digital Mobile Radio technology offers users of Professional Mobile Radio systems the opportunity to upgrade their PMR systems from analogue to digital technology. As the DMR standard has been developed to facilitate the easy migration from analogue to digital, Digital Mobile Radio provides an ideal platform for many users.
By Ian Poole
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