DMR -  Digital Mobile Radio

 

What is DMR ?

DMR stands for Digital Mobile Radio - an open digital radio standard. DMR has received global recognition as a technology that combines voice, data, features and applications. DMR was designed with three tiers.

DMR tiers I and II is conventional and DMR III is Trunked version.

DMR Tier I products are specified for non-infrastructure use only (meaning without the use of repeaters).

DMR Tier II covers licensed conventional radio systems, mobiles and hand portables operating in PMR frequency bands from 66–960 MHz.

DMR Tier III covers trunking operation in frequency bands 66–960 MHz.

How does DMR operate ?

DMR, is a new standard that has been developed by ETSI defining digital standard for PMR. PMR, an acronym for Professional, Personal, or Private mobile radio is recognised as the term covering radio communications other than mobile telephones.

DMR (Digital Mobile Radio) is a powerful system for linking the worlds of amateur radio and the Internet. You can link your handheld radio to repeaters, individuals, or talk groups located anywhere in the world, quickly and easily. And because it’s all digital, you get crystal-clear sound.

The DMR standard operates within the existing 12.5 kHz channel spacing used in land mobile frequency bands globally, but achieves two voice channels through two-slot TDMA technology built around a 30 ms structure.

 What is TDMA ?

Time division multiple access (TDMA) is a channel access method (CAM) used to facilitate channel sharing without interference. TDMA allows multiple stations to share and use the same transmission channel by dividing signals into different time slots. Users transmit in rapid succession, and each one uses its own time slot. Thus, multiple stations (like mobiles) may share the same frequency channel but only use part of its capacity.

 DMR in Amateur Radio

DMR is the first time a commercial system was adopted for ham use. Most of the terms heard in relation to DMR are carryovers from the commercial world. In comparison, D-STAR and Fusion were specifically designed for ham radio use. D-STAR, Fusion, and DMR are all open standards. This means commercial gear is setup for commercial users while ham gear is setup for the way hams use radios. All three use the proprietary AMBE codec allowing 12.5 kHz wide transmissions. DMR achieves two simultaneous transmissions in the same bandwidth. D-STAR uses the AMBE codec while DMR and Fusion use AMBE+2.

 

Typical DMR functions

 

DUAL MODE

Ensure a smooth transition from analog to digital with dual mode functionality.

NOISE CANCELLATION

Be heard anywhere with background noise cancellation, ensuring clarity wherever you go.

TEXT MESSAGING

Text messaging functionality with a one-touch feature for pre-programmed text messages and voice calls.

VERSATILE VOICE CALLS

Make the right call - individual, group or broadcast on all digital channels.

SAFETY FEATURES

Stay safe at all times with Lone Worker, Man Down, Emergency Alarm and GPS positioning features.

 

 D-STAR (Digital Smart Technologies for Amateur Radio) is a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum shift keying in its packet-based standard. 

 System Fusion is Yaesu’s implementation of Digital Amateur Radio, utilizing C4FM 4-level FSK Technology to transmit digital voice and data over the Amateur radio bands.

D-STAR has an Internet and networking component accessible by users built into the standard. This includes an APRS-like position reporting system called D-PRS. Fusion can transmit pictures messages, and position information to other stations. DMR data features in ham radio are underutilized. Up to this point, text messaging was the most widely used data feature. The Brandmeister network is the first network to begin taking advantage of position reporting data.

 Other commercial digital technologies / protocol

  • dPMR - Digital Private Mobile Radio
  • NXDN - is an open standard Common Air Interface (CAI) technical protocol for mobile communications
  • P25 - Project 25 (P25 or APCO-25) is a suite of standards for digital mobile radio communications designed for use by public safety organizations
  • TETRA - Terrestrial Trunked Radio (TETRA; formerly known as Trans-European Trunked Radio), a European standard for a trunked radio system, is a professional mobile radio and two-way transceiver specification

Information courtesy :

  • https://en.wikipedia.org/wiki/Digital_mobile_radio
  • https://www.techopedia.com/definition/5089/time-division-multiple-access-tdma
  • http://kenwoodcommunications.co.uk/digital-pmr/kenwood-dmr/dmr-repeaters
  • https://www.hytera.us/dmr
  • https://brandmeister.network
  • https://www.jeffreykopcak.com