Digital mobile radio is an open digital radio standard for professional mobile radio

Professional Mobile Radio

Professional mobile radio are field radio communications systems which use portable, mobile, base station, and dispatch console radios...

 (PMR) users specified in the European Telecommunications Standards Institute

European Telecommunications Standards Institute

The European Telecommunications Standards Institute is an independent, non-profit, standardization organization in the telecommunications industry in Europe, with worldwide projection...

 (ETSI) Standards TS 102 361 parts 1 to 4 and used in products sold in all regions of the world. The applicable ETSI compliance standards are EN 300 113 and EN 300 390. Products built to the DMR standard also comply with the U.S. Federal Communications Commission

Federal Communications Commission

The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...

 (FCC) mandates in the United States for the use and certification of 12.5 kHz and 6.25 kHz narrowband technology for systems covered by Part 90 regulations.

The DMR standard operates within the existing channel spacing

Channel spacing

Channel spacing is a term used in radio frequency planning. It describes the frequency difference between adjacent allocations in a frequency plan. Channels for mediumwave radio stations, for example are allocated in internationally-agreed steps of 9 or 10 kHz: 10 kHz in ITU Region 2 and 9 kHz...

 used in land mobile frequency bands globally. Its primary goal is to specify a digital system with low complexity, low cost and interoperability across brands, so radio communications purchasers are not locked in to a proprietary solution. DMR provides voice, data and other supplementary services.
DMR is a two-slot, time division multiple access

Time division multiple access

Time division multiple access is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This...

 (TDMA) system offering voice, data and a range of other features and applications.

In 2005, a Memorandum of Understanding

Memorandum of understanding

A memorandum of understanding is a document describing a bilateral or multilateral agreement between parties. It expresses a convergence of will between the parties, indicating an intended common line of action. It is often used in cases where parties either do not imply a legal commitment or in...

 (MOU) was formed with potential DMR suppliers including Tait Radio Communications

Tait Radio Communications

Tait Radio Communications is a multinational radio communications company with headquarters based in Christchurch, New Zealand. The company has offices in 17 countries and employs 869 staff . Tait develops voice and data radio technologies, exporting about 95% of products from its Christchurch...

, Fylde Micro, Selex, Motorola

Motorola

Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

, Vertex Standard, Kenwood and Icom to establish common standards and interoperability. While the DMR standard does not specify the vocoder

Vocoder

A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...

, MOU members agreed to use the half rate DVSI Advanced Multi-Band Excitation

Advanced Multi-Band Excitation

Advanced Multi-Band Excitation is a proprietary speech coding standard developed by Digital Voice Systems, Inc.- Overview :AMBE is a codebook-based vocoder that operates at bitrates of between 2 and 9.6 kbit/s, and at a sampling rate of 8 kHz in 20-ms frames...

 (AMBE) vocoder to ensure interoperability. In 2009, the MOU members set up the DMR Association to work on interoperability between vendors equipment and to provide information about the DMR standard.

DMR Tier I

DMR Tier I products are for license-free use in the 446 MHz band.

This part of the standard provides for consumer applications and low-power commercial applications, using a maximum of 0.5
watt RF power. With a limited number of channels and no use of repeaters, no use of telephone interconnects, fixed/integrated antennas, and a talk timer of 180 seconds, Tier I DMR devices are best suited for personal use, recreation, small retail and other settings that do not require wide area coverage or advanced features.

DMR Tier II

DMR Tier II covers licensed conventional radio

Conventional radio

In radio communication, a conventional radio is generally understood as being a system in which each group of talkers is assigned one frequency. This is usually contrasted to a trunked radio system, where talkgroups share a given group of frequencies....

 systems, mobiles and hand portables operating in PMR frequency bands from 66-960 MHz.
The ETSI DMR Tier II standard is targeted at those users who need spectral efficiency

Spectral efficiency

Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system...

, advanced voice features and integrated IP data services in licensed bands for high-power communications. ETSI DMR Tier II specifies two slot TDMA in 12.5 kHz channels.

DMR Tier III

DMR Tier III covers trunking

Trunking

In modern communications, trunking is a concept by which a communications system can provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually. This is analogous to the structure of a tree with one trunk and many branches. Examples of...

 operation in frequency bands 66-960 MHz. The Tier III standard specifies two slot TDMA in 12.5 kHz channels. Tier III supports voice and short messaging handling similar to MPT-1327

MPT-1327

MPT 1327 is an industry standard for trunked radio communications networks.First published in January 1988 by the British Radiocommunications Agency, and is primarily used in the United Kingdom, Europe, South Africa, New Zealand, Australia and even China...

 with built-in 128 character status messaging and short messaging with up to 288 bits of data in a variety of formats. It also supports packet data service in a variety of formats, including support for IPv4

IPv4

Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...

 and IPv6

IPv6

Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...

.