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Appendix A - Digital Mobile Radio (DMR) Standards

Digital Mobile Radio (DMR) is a digital radio standard specified for business mobile radio users, developed by the European Telecommunications Standards Institute (ETSI) and first ratified in 2005.

The standards that define DMR consist of four documents covering DMR Tier I, II and III. These can be downloaded free of charge from the ETSI website. Tier I is designed for unlicensed radio systems and Tier III is based around digital trunked radio. The DMR standard tiers (Tier I, Tier II and Tier III) are all incompatible. Tier II is the most suitable for fireground communications.

  • General system design TR 102 398
  • Part 1: DMR air interface (AI) protocol - TS 102 361-1
  • Part 2: DMR voice and generic services - TS 102 361-2
  • Part 3: DMR data protocol - TS 102 361-3
  • Part 4: DMR trunking protocol - TS 102 361-4

Tier II covers licensed conventional radio systems, mobile phones and hand portable radios operating in private mobile radio (PMR) frequency bands from 66-960MHz. The standard is aimed at users who need spectral efficiency, advanced voice features and integrated internet protocol (IP) data services in licensed bands for high-power communications. ETSI DMR Tier II specifies two-slot Time Division Multiple Access (TDMA) in 12.5 kHz channels.

As well as ensuring that the correct digital standard is being used, several other parameters need to be correct to provide compatibility on a given channel (frequency), including colour code, time slot, talk-group identification and encryption, although regulations require that transmissions are in clear speech (i.e. not encrypted).

Digital fireground radios are configured by software in the radio, referred to as a code plug. The overarching procurement principle for fire and rescue services is to maintain interoperability with all neighbouring fire and rescue services, wherever possible.

When developing their radio specification for procuring DMR (Tier II) fireground radios, fire and rescue services should consider:

Frequency

Based around current channel assignments for fireground radios.

Digital colour code

16 digital colour codes are available. A code is used to allow different systems or organisations to ‘share’ a frequency without hearing each other. Only one system can use the frequency time slot at any given time.

Group ID

A group ID allows multiple talk groups to share the same colour code. Only one talk group can use the colour code/frequency time slot at a time.

Slot number

DMR allows a 12.5 kHz channel to be sliced into two time slots. Users on time slot one and time slot two can use the frequency simultaneously, effectively creating two channels per 12.5 kHz assignment. N.B. In simplex mode, only time slot one should be used.