DMR (Digital Mobile Radio) is a digital radio standard for Professional
Mobile Radio (PMR) users developed by ETSI (the European
Telecommunications Standards Institute). It is specifically targeted at
systems where analogue PMR is currently applied and designed to deliver
digital voice, data and other supplementary services in a simple and low
cost manner, and first ratified in 2005
One of the principle benefits of DMR is that it enables a single 12.5kHz
channel to support two simultaneous and independent calls. How this is
Under the DMR standard, Time Division Multiple Access (TDMA) retains the 12.5kHz channel width and divides it into two alternating timeslots. Each timeslot acts as a separate communication channel with an equivalent bandwidth of 6.25kHz, but the channel as a whole maintains the same profile as an analogue 12.5kHz signal. This means that DMR will fit into your existing licensed PMR bands, meaning that there is no need for re-banding or re-licensing and at the same time doubling the capacity of your 12.5kHz channel.
While voice is utilising the first time slot the second time-slot can, in a TDMA system, be used for transmitting application data such as text messaging or location data in parallel with call activity useful, for example, in dispatch systems that provide both verbal and visual dispatch instructions. In an increasingly data rich world this enhanced data capability may become important. Another advantage of the DMR TDMA approach is that you get the two channels with one repeater, one antenna and a simple duplexer
Compared to FDMA solutions, two-slot TDMA allows you to achieve 6.25kHz equivalent efficiency while minimising investments in repeaters and combining equipment. FDMA requires a dedicated repeater for each channel, plus expensive combining equipment to enable multiple frequencies to share a single base-station antenna. It can be particularly expensive to make combining equipment work with 6.25kHz signals, and there’s typically a loss in signal quality and range when it’s used in this way.
Two-slot TDMA achieves stable two-channel equivalency using single-channel equipment. No extra repeaters or combining equipment are required (and there is lower drain on air conditioning and less back up power supplies needed). This means lower cost and simpler site planning for DMR users.
Longer battery life and greater power efficiency
One of the biggest challenges with mobile devices has always been battery life. In the past, there have been limited options for increasing the talk time on a single battery charge. Two-slot TDMA, however, offers a good way forward. Since each call uses only one of the two timeslots, it requires only half of the transmitter’s capacity. The transmitter is idle half the time that is, whenever it’s the unused timeslot’sn turn
For example, in a typical duty cycle of 5 percent transmit, 5 percent receive, and 90 percent idle, the transmit time accounts for a high proportion of the drain on the radio’s battery. By cutting the effective transmit time in half, two-slot TDMA can enable up to 40 percent improvement in talk time in comparison with analogue radios. (One manufacture’s published product literature gives a talk time of 9 hours operation for analogue mode but 13 hours for digital mode on the same radio). With overall battery consumption per call dramatically reduced longer usage time in the field between recharges is enabled. Modern digital devices also include sleep and power-management technologies that increase battery life even further.
These power efficient features give DMR users a leaner and greener radio network as well as one with the benefit of long battery life on the radios themselves. The end-to-end digital nature of DMR enables applications such as text messaging GPS and telemetry to be easily added onto radio devices and systems. As the DMR standard also supports the transmission of IP data over the air, this enables the easy development of standard applications. In a world which increasingly relies on data as well as voice communication this ability to add a wide range of data applications to your system results in the greatest possible return on your investment. As DMR is a fully public open standard backed by a wide variety of vendors, buyers can be assured of continuity of supply. Today DMR is the most widely adopted digital two way radio system, is in active use in over 100 countries and is the market leading digital PMR technology. Ease of use of and creation of data applications Security of supply through a fully open, well established, widely backed standard DMR is the best established digital technology in the market today and is the clear choice for organizations looking to deploy new digital two-way radio systems, or to upgrade their existing analogue radio to digital.