DMR is a digital radio standard 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 licensed land mobile frequency bands globally and to meet future regulatory requirements for 6.25kHz channel equivalence. The standard’s primary goal is to specify affordable digital systems with low complexity.
DMR provides voice, data and other supplementary services. DMR is a global standard and consists of three tiers, although in practice commercial application is currently focused on the Tier II and III licensed categories.
DMR Tier I: Unlicensed
DMR Tier I products are for licence-free use in the 446MHz band. Tier I provides for consumer applications and low-power commercial applications, using a maximum of 0.5W 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.
‘We won’t be producing products for Tier I because it is basically targeted at consumers,’ says Jonathan Bunce, marketing director of Simoco Group, which is soon to launch a full end-to-end system encompassing DMR base stations, portable and mobile devices. ‘It operates in unlicensed spectrum and is a low-end proposition for low-end customers of consumer electronics outlets.’
Sean Fitzgerald, solutions marketing manager for radio products and accessories at Motorola Solutions, which has been marketing its MOTOTRBO DMR solutions and devices for several years, agrees but points out there are also business applications for Tier I solutions.
‘Within Tier I consumer users are addressed but there is also a subset of business users, such as users in retail or restaurants, where waiting staff may have a small earpiece to communicate orders,’ he says. ‘Tier I is typically suitable for situations involving less than 10 radios where the requirements are not sophisticated and users are happy to just push the button to talk. It’s not an area we are interested in,’ adds Fitzgerald.
DMR Tier II: Conventional DMR
Tier II is where the DMR market becomes more interesting. It 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 and are starting to offer greater functionality than originally envisaged, as Fitzgerald explains: ‘Tier II fits in the middle between Tier I and Tier III,’ he says. ‘It was originally defined as conventional radio so users could talk to each other with no intelligence within the system. What’s happened, because the technology being used is so sophisticated, is that we’ve managed to squeeze some trunking capability into Tier II.
Fitzgerald adds that Motorola guarantees its Tier II solution will support up to 1,200 users, but he knows of organisations using it to support a greater number.
Simoco’s Bunce sees Tier II as the middle ground. ‘Tier II is where we really start playing,’ he says. ‘Tier II allows you to have a particular chunk of spectrum and make much more efficient use of it. It involves base stations and repeaters, so you get much greater capacity on this system than you could in a standard analogue system. Users could be on building sites, in schools or education sites, or in transport systems such as buses.’
Monique Princen, chair of the DMR Marketing Working Group, explains the tier’s applicability. ‘Tier II is targeted towards business-critical applications and users and is widely deployed worldwide in businesses and public service organisations. Ports, airports, highway control, hospitals, utility and transport organisations are amongst the hundreds of users of DMR today,’ she says.
‘It has given these organisations the ability to increase their communications system in a spectrally restricted environment and many users have the ability for the first time to implement location, intelligent dispatch and telemetry applications which before were only found on the high-end and large radio networks,’ points out Princen.
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 services in numerous formats, including support for IPv4 and IPv6.
‘Tier III is really where you’ve got a system that operates over a much wider area and allows multiple sites to talk to each other,’ explains Bunce. ‘It’s applicable to a manufacturer with three or four sites or business-critical markets like power distribution or oil and gas.’
It provides greater functionalities than Tier II. ‘Compared to Tier II, trunked DMR offers more comprehensive data capabilities and supports short data messaging, which is very suitable for location services without impacting the voice functionality,’ adds Princen. ‘The trunked features allows for advanced control of communications like call queuing and provides for easy and cost-effective fleet management.’
Although it’s been in existence since 2005, DMR is now coming of age as more vendors come to market. ‘We were the first to market but DMR has now become the most widely adopted standard,’ explains Motorola’s Fitzgerald.
‘That’s great for the ecosystem around DMR in terms of test equipment and integration of other technologies like GPS into handsets. More and more people are using radio – and these are sophisticated users – as a tool to help them run their businesses, and as third parties develop software apps for DMR, the market widens to encompass fleet operators, security firms, health and safety requirements and indoor localisation.’
Fitzgerald sees DMR integrating with RFID and Bluetooth in addition to GPS and expects that to widen the applications still further. ‘We don’t want to develop the apps themselves because the vertical markets are so varied,’ he adds. ‘We currently have 300 licensed developers, which represents by far the largest applications development programme in the industry.’
Bunce thinks the cost advantages, coupled with that widening ecosystem, will make the technology attractive to an even greater audience. ‘Once you go to an IP-type technology, you are basically using a computing level of communications and the amount of applications and customisation capability goes up hugely,’ he says.
‘DMR provides much, much less functionality than TETRA, but most DMR users don’t need full TETRA functionality. Critically, DMR is nowhere near as complex or as costly as TETRA or P25 and fits the next segment down in the market. As it develops, DMR will have a lot of the functionality of TETRA to get the apps out to the users,’ argues Bunce.