Digital


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DMR on site: embodying all the good points of earlier digital mobile technologies, this standard is attracting strong interest among users with a diverse range of requirements – in industry, in power and the utilities, in oil, gas and mining, as well as in small campus applications


DMR in the spotlight I


Andy Grimmett, chief technologist at Simoco, takes a look at the latest developments in Digital Mobile Radio technology and at some of its uses


t has taken over a decade for 15 per cent of the world’s licensed mobile radio us- ers to switch from analogue to digital,


according to a recent report (IMS Research). However, these key findings suggest that de- spite this sluggish start, recent developments


within the industry are set to see migration more than double in the next five years. Digital technologies were first introduced


to the mobile radio market in the mid-1990s. Early standards included Tetra and APCO Project 25 (P25), but were designed for use by the emergency services and so, for many commercial organ- izations, they can be rather like using a sledgehammer to crack a nut. While technologies such as dPMR, NXDN and PDT will help to open up


the digital market to many more users, it is the intro- duction of Digital Mobile Radio (DMR) in particu- lar that will fuel growth.


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So what is DMR? DMR is a two-slot, time division multiple ac- cess (TDMA) system offering voice, data and a range of other features and applications. Tis is the same underlying technology used


by Tetra and P25 Phase II. Simply put, TDMA divides up spectrum using timeslots (diagram, left): User A gets a few milliseconds of access to the bandwidth, and then it is User B’s turn. • DMR Tier 1 is targeted at the unlicensed market, providing for consumer applications and low-power commercial applications.


• DMR Tier 2 is targeted at those who require spectral efficiency, advanced voice features and integrated IP data in licensed bands for high-power communications.


• DMR Tier 3 is the trunked variant of the standard, for systems with a large number of subscribers and for multi-site networks.


LAND mobile January 2011


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