The Digital Mobile Radio (DMR) standard is developed by the European Telecommunications Standards Institute (ETSI) and was first approved in 2005. DMR employs Time Division Multiple Access (TDMA) technology, dividing a 12.5 kHz channel into two time slots. Each time slot lasts 30 milliseconds, and the data transmission rate is 9.6 kbps per slot.
DMR supports three operational modes: Direct Mode, Repeater Mode, and Trunking Mode. Its operating frequency bands include VHF (136–174 MHz) and UHF (400–470 MHz). The protocol utilizes a three-tier architecture, encompassing unlicensed (Tier 1), licensed conventional (Tier 2), and licensed trunking (Tier 3) operational modes.
DMR employs 4FSK modulation. Voice encoding and decoding are performed using the AMBE algorithm, typically at a data rate of 3.6 kbps. The advantages of DMR include high spectral efficiency, compatibility with analog systems, and lower equipment costs. Compared to other digital radio standards, DMR occupies a distinct niche in terms of cost, spectral efficiency, and applicable use cases.
