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Digital Mobile Radio (DMR) is a digital radio standard specified for professional mobile radio (PMR) users developed by the European Telecommunications Standards Institute (ETSI), and first ratified in 2005.
The standard is designed to operate within the existing 12.5kHz channel spacing used in licenced land mobile frequency bands globally and to meet future regulatory requirements for 6.25kHz channel equivalence. The primary goal is to specify affordable digital systems with low complexity. DMR provides voice, data and other supplementary services. Today, products designed to its specifications are sold in all regions of the world.
The DMR protocol covers unlicensed (Tier I), licensed conventional (Tier II) and licensed trunked (Tier III) modes of operation, although in practice commercial application is today focussed on the Tier II and III licensed categories.
The standards that define DMR consist of four documents. These can be downloaded free of charge from the ETSI website. Follow the links below.
TS 102 361-1: the DMR air interface protocol
TS 102 361-2: the DMR voice and generic services and facilities
TS 102 361-3: the DMR data protocol
TS 102 361-4: the DMR Trunking protocol
There is also a designer's guide encompassing elements from all standards parts that is an easier read:
TR 102 398: DMR General System Design
What are the different types of DMR
There are three tiers in the DMR standard.
DMR Tier I: Unlicenced
DMR Tier I products are for license-free use in the 446MHz band.
Tier I provides for consumer applications and low-power commercial applications, using a maximum of 0.5Watt RF power. With a limited number of channels and no use of repeaters, no use of telephone interconnects, and fixed/integrated antennas, 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: Conventional DMR
Tier II covers licensed conventional radio systems, mobiles and hand portables operating in PMR frequency bands from 66-960MHz. The ETSI DMR Tier II standard is targeted at users who need spectral efficiency, advanced voice features and integrated IP data services in licensed bands for high-power communications. ETSI DMR Tier II specifies two-slot TDMA in 12.5kHz channels.
DMR Tier II products are commercially available today.
DMR Tier III: Trunked
DMR Tier III covers trunking operation in frequency bands 66-960MHz. The Tier III standard specifies two-slot TDMA in 12.5kHz channels. Tier III supports voice and short messaging handling similar to MPT-1327 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 and IPv6.
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