(DMR(Digital Mobile Radio

Digital mobile radio (DMR) is an European Telecommunications Standards Institute (ETSI) digital mobile radio standard for professional mobile radio users worldwide.

The DMR standard provides voice and data services and operates in existing channel spacing bands. It is a spectrally efficient, time division multiple access (TDMA) technology offering two timeslots in a 12,5 kHz channel, and thus doubles channel capacity when compared with existing analogue technologies.

DMR is available for professional mission and operation-critical applications in Tiers 2 & 3:

·         DMR Tier2 covers licenced conventional operation in 66 to 960 MHz and offers spectral efficiency, advanced voice features and integrated IP data services.

·         DMR Tier3 covers licenced trunked operation in 66 to 960 MHz and supports voice and data messaging similar to MPT1327, and also supports packet data services.

Tier2 products are available worldwide from Vertex Standard, Motorola, Hytera, Selex and Radioactivity. There are currently no Tier3 products available, however Hytera and Tait Radio Communications are planning to release Tier3 products within the next twelve months.

In the African market, there are many legacy analogue systems that would benefit significantly from the digital technology supported by the DMR standard. This has already been demonstrated by successful installations of DMR at airports, for traffic control systems, and utilities.

Digital mobile radio (DMR) is an European Telecommunications Standards Institute (ETSI) digital mobile radio standard for professional mobile radio users worldwide.

The DMR standard provides voice and data services and operates in existing channel spacing bands. It is a spectrally efficient, time division multiple access (TDMA) technology offering two timeslots in a 12,5 kHz channel, and thus doubles channel capacity when compared with existing analogue technologies.

DMR is available for professional mission and operation-critical applications in Tiers 2 & 3:

·         DMR Tier2 covers licenced conventional operation in 66 to 960 MHz and offers spectral efficiency, advanced voice features and integrated IP data services.

·         DMR Tier3 covers licenced trunked operation in 66 to 960 MHz and supports voice and data messaging similar to MPT1327, and also supports packet data services.

Tier2 products are available worldwide from Vertex Standard, Motorola, Hytera, Selex and Radioactivity. There are currently no Tier3 products available, however Hytera and Tait Radio Communications are planning to release Tier3 products within the next twelve months.

In the African market, there are many legacy analogue systems that would benefit significantly from the digital technology supported by the DMR standard. This has already been demonstrated by successful installations of DMR at airports, for traffic control systems, and utilities.

DMR for professional mobile radio networks

The challenge for DMR is to educate professional users in order to create an understanding and appreciation of the advantages of two-slot TDMA. The myriad of non-ETSI compliant 6,25 kHz FDMA technologies may appear to be very attractive if a simplistic, uneducated equipment cost comparison is performed.

FDMA requires additional site equipment

The implementation of a two- channel, 6,25 kHz FDMA system requires double the transceiver equipment, additional antennas and feeder cable and/or antenna combining equipment when compared to a two-timeslot 12,5 kHz DMR installation. This is an often-overlooked cost.

DMR scalability

DMR, notably Tier3, is a scalable system designed for professional users in mission- critical applications and supports both small and large multi-site systems. Many FDMA systems, by contrast, are limited to smaller system applications.

DMR supports features and functionality suitable for professional mission-critical applications that simply cannot be supported by single-channel 6,25 kHz FDMA technologies.

DMR –longer battery life and greater power efficiency

TDMA devices utilise one timeslot at a time, therefore the radio transmitter is idle for a significant portion of the operation. This increases the operational time or user shift life of a battery operated terminal. DMR radios consume typically 20 to 34% less battery capacity than similar FDMA models.

DMR system flexibility through simultaneous use of TDMA channels

DMR uses two timeslots which facilitates extended usability that cannot be offered or supported by a single-channel FDMA device:

·         Whilst voice is used on the first time slot, DMR supports simultaneous use of the second timeslot for data, e.g. GPS location information. This is particularly useful in professional dispatch applications where both voice and visual instructions are transmitted.

·         By combining two timeslots for data, the data throughput is doubled.

·         Full duplex voice functionality is possible on DMR radios while for FDMA radios this requires the addition of a second transmitter.

Spectrum usage migration from analogue to DMR

DMR facilitates an easy migration from analogue to digital as it re-uses existing spectrum. FDMA systems, by comparison, require allocation of new 6,25 kHz channels as it is generally not possible (or allowed) to fit two 6,25 kHz channels into one existing licenced 12,5 kHz channel. Therefore in order to increase capacity without applying for new frequencies, DMR is the only choice.