Digital Mobile Radio

Digital Mobile Radio ( DMR ) to German: Digital mobile designates a transmission standard for voice and data in non- public wireless networks such as mobile radio. DMR was established in 2006 by the European Telecommunications Standards Institute (ETSI ) adopted as a standard (ETSI EN 300 113 Part 2).

Technically DMR provides full-duplex transmission and cooperates with the time-division multiplex method. In data transmission, a gross data rate of 9.8 kbit / s is achieved and occupies a bandwidth of 12.5 kHz.

A competing process is dPMR which uses the FDMA frequency division multiplexing method and with a bandwidth of 6.25 kHz, only a third of the previous bandwidth of 20 kHz is ( ETSI EN 301 166 Part 2).

A special topicality learn these two methods through a reorganization of the U.S. Federal Communications Commission. Due to a lack of free channels new wireless applications will only be approved if they use a maximum bandwidth of 6.25 kHz per voice path in the future in the U.S.. In dPMR this is just the carrier bandwidth, the DMR, with its two time slots on a 12.5 kHz carrier Speak of 6.25 kHz equivalent.

DMR in amateur radio

Even in amateur radio DMR is used. For commercial DMR equipment be modified and reprogrammed by radio amateurs. Worldwide, some DMR relay, often built in the 70 cm band and connected via IP Site Connect.

There are two amateur radio networks, the DMR -MARC network and the Hytera network. The DMR -MARC- network is the older network, it is based on Motorola Mototrbo repeaters. The network is based on Hytera Hytera repeaters of the company. Radios are compatible with both networks of all DMR manufacturers.

A list of the currently available relays in the DMR -MARC network is among http://dmr.darc.de/dmr-net.php (list of networked repeater) or http://www.dmr-marc.net/repeaters to find. html (list of networked repeater).

Here are the shifter in DL, HB and OE for the DMR -MARC network to Find: (MAP of repeaters in Europe) (MAP repeater in Austria )

The link is further http://dmr.darc.de/ the DMR Log evident (for the DMR -MARC- network).

Information about Hytera network can be found on http://www.ham-dmr.de ( with list of relays, the relay card, load- Heard -List, etc.)

Benefits

The main advantages are flexibility:

- Since DMR two time slots brings (two simultaneous calls possible), so can on time slot 1 (TS1 ) calls ( World Wide or AT / DE / CH .... ) can be performed with it at the same time possible, in the time slot 2 (TS2 ) to keep a Local / National Talk QSO without the other call is disturbed.

- By connecting the relay international calls are possible. Thus, discussions with 100 participants on the time slot TS1 -1 ( World Wide ) not uncommon.

- Each participant is given a unique ID, which he can then deposit into his radio. So it is possible that everyone can see the CALL SIGN / ID QSO his partner during the conversation on the display, if the CALL SIGN is stored in Contacts.

Disadvantages

Since the main application comes from the operation of radio, there is no provision for the reprogramming to make right on the radio. For a PC, and a programming cable is required. In the meantime, the direct changing the frequency and time slot for digital channels and talkgroup is directly possible in the current firmware version of Hytera. Motorola has also announced a firmware soon.

Classification compared to other wireless standards

DMR is marketed as a successor professional analogue radio networks. In the existing ( licensed and unlicensed ) frequency bands better understanding, noise-free transmission as well as higher data rates and additional service features are to be enabled. DMR offers in comparison to analog frequency modulated radio at the same bandwidth of 12.5 kHz with two voice channels, doubling the number of channels. The Federal Network Agency Federal Network Agency issued permits frequency on specially kept free for this mode frequencies in the 2 -meter VHF band and the 70 -cm UHF band.

Compared with TETRA requires DMR significantly lower investments and due to the simpler structure, lower maintenance costs and provides some compatibility with existing radio systems. DMR- Radio equipment and systems are suitable for all applications and can be used to large radio networks for smaller local commercial radio solutions. User, for example, taxi companies, public utilities, public transport and utilities, but also road and motorway authorities services and transport services.

The mixed-mode allows you to switch between analog radio in 12,5 / 20/25-kHz-Raster and digital radio in 6.25 - kHz channel spacing. The devices are so to speak " backwards compatible ". A collaboration with analog devices on another channel is possible, in contrast to Tetra. Repeater as the DR3000 can even support both standards on the same channel (one by one ) - in the mode in which it is called answers the repeater.

Finally, there are target group overlaps with the public GSM networks. As an advantage for DMR while the safer availability is seen as a private network is not hampered by congestion in the telephone network.

Variants

DMR Tier I is designed for hobby applications. The usual technical restrictions such as when PMR446 devices, ie permanently attached antenna, a maximum of 0.5 watts radiated power, use of commonly assigned frequencies. But this they are free of royalties. See also DMR446

DMR Tier II is designed for mobile radio applications. As in the analog radio operates each company 's own equipment, alternating speaking, ie without any external infrastructure. By suitable cross-linked repeater but can also be realized small radio networks with DMR Tier II. DMR Tier II is commonly referred to as "conventional DMR ".

DMR Tier III describes major radio networks with base stations and IP networks. This makes it possible to provide larger areas. For companies, for example, several buildings, with local transport companies or entire regions such as the amateur radio worldwide networking of all DMR repeater. DMR Tier III should therefore be seen as an alternative to TETRA standard.

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