Trunked radio

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Trunked radio , engl. Trunked radio system , is the umbrella term for various standards of radio systems with channel bundling for radio devices . The term is widely used in German-speaking countries as a synonym for Professional Mobile Radio (PMR). A permanently installed radio infrastructure consisting of transmitter masts and a core network is required for trunked radio . All radio communication is handled via the permanently installed radio infrastructure ( TMO ).

Channel bundling

The advantage of channel bundling (hence the name) is that a closed user group, e.g. B. the garbage collection of a municipal waste disposal company no longer has to be assigned one (or more) fixed frequency (a fixed radio channel ) (which may then be used only slightly), but that several user groups of one or more companies share a bundle of frequencies can. This is much more efficient in terms of the need for frequencies; significantly fewer resources (frequencies) are required for the same communication requirements. In the case of public trunked radio networks, there is the possibility that many companies use a common radio infrastructure instead of each individual company having to set up its own radio infrastructure with transmitter masts , core network, etc. In order to meet the requirements of as many users as possible in a region, several transmission masts are often interconnected via fiber optic cables , dedicated lines or radio links to increase the range (coverage) , so that a radio system is created that extends over an entire economic area.

Key functions

The biggest difference to conventional mobile phones , with which only point-to-point calls are possible ( unicast ), is the group call with trunked radio , in which one radio device can communicate with several others at the same time. The radios are usually easy to operate - a button is pressed to speak ( push-to-talk ) and the call is established within a few 100 milliseconds, and it is released again to listen (release-to-listen). The use of rules of speech (e.g. "understood" / "answer") is recommended.

The ranges of the various standards vary. With the currently growing and most powerful trunked radio system TETRA , depending on the nature of the terrain, up to 30 kilometers are possible. However, this theoretical value is of little relevance due to planning parameters such as subscriber density, usage behavior and terrain topography. Mobile relay stations can also be used to expand the radio coverage area.

Basically, the groups connected within a trunked radio network work completely independently of one another. Switching from one group to the other is usually possible in the digital system of trunked radio networks without any major inconvenience. To do this, the system administrator must "activate" the desired group access. This is usually done when setting up the system. This fact is perceived by the users as very beneficial: Not everyone has to listen to everything with the system, but can dial into the respective group radio networks that are relevant to them, provided they have the appropriate authorization.

Areas of application

Trunked radio has a number of advantages over mobile telephony that are indispensable for professional users. The most important: speaking at the push of a button ( push-to-talk ) instead of dialing and waiting for the call to be established. At the push of a button, one channel is made available from a bundle of radio channels according to the “frequency bundle principle”. The conversation is immediately set up with the desired individual participant or with the entire group. All participants, be it from your own fleet or from other fleets, can be reached extremely quickly on the move. They can be dynamically assigned and flexibly adapted immediately to urgent orders or changed situations. In addition to the speed and security of the technology, there is a further advantage in the infrastructure that is independent of public communication networks. B. also guaranteed for New Year's Eve or at major events.

In contrast to mobile telephony , the use of trunked radio is typically restricted to a certain region. Trunked radio systems are characterized by a higher spectral efficiency compared to older mobile radio standards such as GSM .

For areas of public safety, trunked radio systems offer service options such as dynamic group formation or the possibility that two or more radio devices can communicate directly with one another without a permanently installed radio infrastructure ( DMO ). As if from the office, the emergency services can access information systems and databases and query information: information about chemical products or water protection areas, capacities of the surrounding hospitals or the locations of certain special vehicles in the region. Trunked radio systems are therefore particularly interesting for public security bodies such as the police , fire brigade or disaster control . With the help of digital radio, the entire voice or data transmission is transmitted securely to the respective emergency services.

Just trunked radio systems as well as private mobile radio network installed. In large companies such as BMW, Audi or MAN, they have long been part of the basic equipment. Such trunked radio systems can, for example , connect employees in the areas of plant security , plant fire brigade , maintenance or from the high-bay warehouse with each other via radio. Previously, employees had to use a whole range of different notification systems.

Trunked radio is not only used for mobile voice communication, but also for M2M communication. Electricity supply companies in particular often operate regional corporate radio networks that enable reliable M2M communication from the control center of the EVU with all relevant components of the electricity network even in the event of a longer power failure .

Communication services

Comfort functions:


Eavesdropping protection :


Prioritization and displacement:

  • Emergency call with guaranteed, short call setup times
  • Call prioritization: If there are several voice calls to be set up, the emergency call , for example, has priority over the other voice calls.
  • Displacement: If there is no free transmission capacity on the air interface , the data transmission capacity required for the emergency call, for example, is diverted from ongoing voice calls and data transmissions and reserved for the emergency call. Active voice calls are automatically disconnected if necessary.


Failure safety :

  • Direct mode (DMO) : direct communication between wireless devices with complete circumvention of the fixed radio infrastructure upon failure of the fixed radio infrastructure or in the absence of network coverage of fixed radio infrastructure ( dead zone ).

Disadvantages of trunked radio and comparison with cellular networks

The data transmission rates available for voice transmissions are significantly higher in the cellular network than in digital trunked radio. That is why the voice quality in the cellular network is significantly better than with digital trunked radio. Digital trunked radio is not suitable for longer calls because of the poorer voice quality. AMR with 12.2 kbit / s is often used in modern mobile communications . Modern, digital trunked radio uses data transmission rates in the range from 2.4 kbit / s ( AMBE ) to 4.75 kbit / s (AMR) for voice transmissions .

Digital trunked radio allows no or only very cumbersome voice telephony via MSISDN .

The modern, digital trunked radio systems listed below use exclusively FDM or a combination of FDM / TDM . Radio systems based on FDM or a combination of FDM / TDM are susceptible to narrowband interference and multi-path reception . Modern radio methods such as CDM or OFDM are not used by any of the modern digital trunked radio systems listed below. OFDM or OFDM-like methods are the current state of radio technology for mobile devices that have to support fast data transmission rates (> 1 Mbit / s). OFDM offers a very high spectral efficiency . OFDM in the COFDM version is immune to multi-path reception and narrowband interference.

The CDM radio method is best suited for slow data transmissions and voice transmissions (<20 kbit / s). A radio technology based on CDM can take advantage of frequency spreading with DSSS . DSSS is insensitive to narrowband interference. With the DSSS used, a rake receiver can be used in the radio receiver . A rake receiver can use multipath reception to improve radio reception. For the radio cells - handover based on the CDM radio systems "soft handover" can be used. "Soft handover" enables more stable and safe cell changes. For these reasons, CDM and DSSS are used for UMTS .

All wireless standards support the radio cells - handover . The user does not notice anything about the change of radio cell during the phone call. The change of radio cells takes place in mobile radio networks without interruption for the user. Most trunked radio systems do not support handover. If the handheld radio leaves the radio cell, the ongoing call is terminated. Only TETRA supports radio cell handover.

All mobile radio standards support the automatic, adaptive transmit power control (TPC) of the mobile devices and the base station . Trunked radio systems generally do not support automatic, adaptive transmission power control (TPC). Only TETRA supports an automatic, adaptive transmission line control (TPC) for the mobile device. With TPC, the transmission power is reduced to the minimum required, which extends the battery life of the mobile device or handheld radio and reduces the risk of radio interference. Without TPC, the maximum transmission power is always used, which means an unnecessarily high radiation exposure (high SAR value). In the case of handheld radios for trunked radio, the maximum transmission power at the antenna connection is in the range of 0.5 to 5.0 watts . Without TPC and with long talk times, the battery of the handheld radio is quickly empty.

In the cellular networks, speaking at the push of a button ( push-to-talk ) is possible with special mobile devices . Speaking at the push of a button in the cellular network is called push-to-talk over cellular .

With the "network slicing" introduced with 5G , data transmission rates and round-trip times for packets can be guaranteed in the public cellular network even when the public cellular network is overloaded. "Network Slicing" enables a comprehensive QoS that meets the high requirements of authorities and corporate customers. In addition to trunked radio, which is only suitable for slow data transmissions, the police in particular need a fast (OFDM-based) radio network for the transmission of large amounts of data such as maps, photos, video recordings. This radio network must be protected against overload and have an autonomous energy supply ( UPS ).

As an alternative to trunked radio or the public cellular network with "network slicing", a private, private cellular network can also be operated. Railway infrastructure companies often operate their own private cellular network based on GSM-R for train radio and shunting radio. GSM-R expands the mobile communications standard GSM the known from the trunked radio features such as push-to-talk , group call , emergency call , Rufpriorisierung, guaranteed call setup and repression.

None of the mobile radio standards supports communication with complete bypassing of the fixed radio infrastructure ( direct mode (DMO) ). In older specifications of GSM-R, DMO was provided. In the current specifications of GSM-R, DMO is no longer included. For the shunting in the absence of network coverage of fixed GSM-R radio infrastructure, for example in sidings , must on mobile radio recourse or trunked in the direct mode (DMO).

Public cellular networks in rural areas usually use radio frequencies in the range from 700 to 1000 MHz. Two cellular antennas for these radio frequencies can be accommodated in the housing of the cellphone. Thanks to the diversity of reception and MIMO, the use of two integrated cellular antennas in the mobile phone enables improved radio signal reception and faster data transmission rates when sending. Trunked radio systems for closed user groups such as BOS , industries and municipalities are, as a rule in the VHF - frequency band (136-174 MHz) and UHF home band (350-470 MHz). As the frequency decreases and the wavelength increases , it becomes more difficult to accommodate the antennas in the housings of radio devices. This is why handheld radios for radio applications in the named areas usually have a clearly visible rubber sausage antenna . Since multiple external antennas have a disadvantageous ergonomic effect on handheld radios , MIMO is not used in these applications

System architecture

Analog trunked radio

In analog trunked radio (in Germany) the MPT 1327 standard in the frequency band from 410 to 430 MHz is mainly used.

The frequencies from 410 to 420 MHz for the uplink , 420 to 430 MHz for the downlink . The data transmission on the organization channel takes place at up to 1.2 kbit / s.

Digital trunked radio

Digital trunked radio has technical advantages over analog trunked radio. Analog trunked radio is based on an analog data transmission method (usually: FM ). Digital trunked radio benefits from the advantages of a digital data transmission method, such as forward error correction . Digital trunked radio achieves a greater range than analog trunked radio while maintaining acceptable voice quality. The range of analog trunked radio is greater than the range of digital trunked radio. However, with analog trunked radio at the cell boundary, the voice quality is poor.

Digital trunked radio standards used worldwide for radio by authorities and organizations with security tasks ( BOS radio ( Germany , Austria ) or BORS radio ( Switzerland )) are:

These digital trunked radio standards, suitable for BOS radio and BORS radio, can also be used for commercial radio . Other digital trunked radio standards often used worldwide for professional radio are:

Transmission masts

The transmission masts for trunked radio can usually hardly be distinguished from the known cell phone masts . Only the antenna shape is variable.

See also

Web links

supporting documents

  1. ↑ https://www.swisscom.ch/content/dam/swisscom/de/biz/broadcast-new/funkkommunikation/betriebsfunk/Betriebsfunknetz%20Swisscom%20Broadcast.pdf.dl.res/Betriebsfunknetz%20Swisscom%20Broadcast.pdf Betriebsfunknetz Swisscom Broadcast (PDF)
  2. ↑ http://dpmr-mou.org/downloads/Latest-White-Paper.pdf dPMR White Paper - Issue 1.0
  3. ↑ https://www.qsl.net/kb9mwr/projects/dv/apco25/Digital-Radio-Standards.pdf Tait Radio Communications - White Paper: Technologies and Standards for Mobile Radio Communications Networks
  4. ↑ https://www.etsi.org/deliver/etsi_en/300300_300399/30039502/01.03.01_60/en_30039502v010301p.pdf ETSI EN 300 395-2 v1.3.1
  5. ↑ https://www.heise.de/ct/artikel/Gespreiztes-Spektrum-1899396.html Heise.de - Spread spectrum
  6. ↑ https://www.era.europa.eu/filebrowser/download/1092193_en UNISIG - Subset-044 (only chapter "Annex B")
  7. ↑ https://gsproductsupport.files.wordpress.com/2009/04/description-of-the-globalstar-system-gs-tr-94-0001-rev-e-2000-12-07.pdf Globalstar - Description of the Globalstar System (GS-TR-94-0001)
  8. ↑ http://www.public.navy.mil/spawar/PEOSpaceSystems/News/Documents/Mobile%20User%20Objective%20System%20Overview%20Brief%204.1.10-S.pdf Communications Satellite Program Office (PMW 146) - Mobile User Objective System (MUOS) - April 28, 2009
  9. ↑ https://www.golem.de/news/telecom-italia-mobile-wir-brauchen-kein-5g-1802-133035.html Golem.de - Telecom Italia Mobile: "We don't need 5G"
  10. ↑ https://www.golem.de/news/fuer-4g-und-5g-ericsson-und-swisscom-demonstrieren-network-slicing-1802-132902.html Golem.de - Ericsson and Swisscom demonstrate network slicing
  11. ↑ https://www.golem.de/news/nokia-hamburger-hafen-und-telekom-starten-5g-netz-1802-132553.html Golem.de - Hamburger Hafen and Telekom start 5G network
  12. ↑ dPMR 4 Level FSK / FDMA 6.25 kHz Technology: White Paper - Issue 1.0