Trunked radio system

Trunked radio, Eng. Trunked Radio System, is an umbrella term for different standards of wireless systems with channel bundling. The term is in German speaking countries as a synonym for Professional Mobile Radio (English Professional Mobile Radio, PMR) spread.

The best-known digital trunked TETRA standards, Tetrapol, DMR and APCO P25. The most common analog systems are MPT 1327 Smartnet and SmartZone. Those standards require a variety of mobile services work.

Channel bundling

The advantage of channel bundling ( hence the name) is that of a closed user group, eg the garbage disposal of a waste disposal operation, not one (or more ) fixed frequency (a fixed channel) must be assigned ( which is then optionally be utilized only slightly ), but that multiple user groups of one or more companies share a set of frequencies. This is much more efficient with respect to the need of frequencies; with the same communication needs much less resources ( frequencies) are required. In the case of public trunked radio networks there is the possibility that many companies use a common wireless infrastructure instead of every single company needs to build its own infrastructure with radio towers, base stations, etc.. In order to meet the requirements of as many users in a region (Cover) are often connected together several radio towers on leased line or microwave links to increase the radio range, so that a radio system is created which extends over a complete laundry room.

MPT -1327

See also: paging # Chekker

Even before the introduction of the GSM networks various states had statewide or regional analog trunked radio networks based on the MPT -1327 standards in operation. In Germany there were several suppliers of which the German Telekom, which has marketed their trunked radio systems under the name Chekker, who was the greatest. The legislature had in planning a regional network in mind - as an exclusion of pre-existing C network wireless telephone network. The regionality was but in the long run also the biggest problem of the networks. On the one had to be provided for each economic region a separate application. Many A4 folder with expensive planning documents had to be submitted. On the other had to the user when he sent his vehicle into another region ( to the site there), the radios to be reprogrammed with the radio channels used there. Then an additional fee is payable for the additional region. A roaming, as usual in wireless telephone networks, there was not. Was trunked compared with the C network still competitive, so came up with the sinking of the charges in the D- net for many network operators quickly the corner. The operating companies changed very often. A centralization began, and the last - then nationwide - Dolphin Telecom operators said. He tried another conversion to digital trunked radio. When, however, was denied a U.S. cellular phone standard by the Federal Network Agency, the conversion, the Canadian investor withdrew from Europe. The operating company was settled, and many wireless networks have been shut down. Some subnetworks were held by local operators continue to operate and are still in operation today.

Key Features

The main difference to conventional mobile phones, where only point -to-point telephone calls are possible, in PMR called point-to- multipoint communication ( group call), in which a device can simultaneously communicate with several other. Usually, the radios are easy to use - to speak a button is pressed (push- to-talk) and built within less than 100 milliseconds, the call, to listen, he is re- released ( release- to- listen). The ranges of different standards vary. At present growth and most powerful TETRA trunked radio system, up to 83 km are possible depending on the terrain, for example. However, this theoretical value is of little relevance because of planning parameters such as subscriber density, usage patterns and terrain topography. In addition, a single radio device can be used as a mobile relay station for other devices, in order to extend the radio coverage area. Basically, the federated within a trunked radio network groups operate completely independently. The change from one group to the other is possible in the digital system of trunked radio networks usually without any hassle. For this, the system administrator must " unlock " the desired group access. Most is already done when setting up the system. Of the users, this fact is exactly perceived as very beneficial, not everyone has to listen to the system everything, but can, provided the appropriate permission to dial in the respective group radio networks that are of concern to him.

Areas of application

Unlike the mobile as GSM, the use of trunked radio is typically limited to a specific region. Trunked radio systems but are distinguished from conventional GSM systems by significantly improved voice quality in the case of loud ambient noise and a higher frequency of economics. PMR systems such as TETRA standard offer over GSM networks, which provide eight channels of communication at 200 kHz channel spacing, a four times better frequency reuse ( four communication channels at 25 kHz channel spacing ). In addition, a frequency division multiplexing takes place by the mating of each RF channel in an uplink and a downlink frequency, instead. Thus, the high channel capacity is achieved. The latest generation is called TETRA TETRA Enhanced Data Service. Data rates of up to 300 kbit / s are possible with this system, which means about a tenfold increase in speed. This also visual information such as maps, images or video sequences can now be transferred in real time. For areas of public safety trunked radio systems offer service options such as dynamic group formation or the possibility that two or more can be mobile stations without an intermediate base station communicate directly with one another ( direct mode ). As the office of the emergency services are able to draw on information systems and databases and query information: maps, site plans, information on chemical products or water protection zones, capacity of the surrounding hospitals and the locations of certain special vehicles in the region. Interestingly PMR systems are therefore particularly for public safety such as police, fire and civil protection institutions. Because with the help of digital radio across the voice or data communications to be private forwarded to the respective task forces. Just PMR systems will also be installed as a radio network. With large companies such as BMW, Audi or M.A.N. they belong long ago as standard. Such radio communication systems can connect, for example, staff in the plant security, fire-fighting, maintenance or in the high-bay warehouse on digital radio together. Employees had to use a number of different notification systems.

Communication services

  • Direct, group, emergency call set-up with short
  • Data transfer (status messages, short data service, IP packet data)
  • Fax, e -mail, database queries
  • Call forwarding, call forwarding, conference calling, call priorities
  • Authentication and Encryption

Licenses

In Germany, the licenses for the operation of a trunked radio system by the Federal Network Agency for Electricity, Gas, Telecommunications, Post and Railway ( Federal Network Agency, formerly the Regulatory Authority for Telecommunications and Post) were awarded in the following classes:

  • A metropolitan areas, regions with high demand
  • B smaller areas
  • C individual plots of land (eg, airports, harbor area )
  • D entire federal territory

Meanwhile, this distinction is no longer being made. All licenses issued will rank pari passu.

System Architecture

A trunking radio system comprises:

  • Switching system: MSC, Master System Controller
  • Network management system: NMC Network Management Center
  • Base stations: BS, Base Station

Analogous

In the analog trunked radio is used ( in Germany ), especially the standard MPT -1327 in the frequency band 410-430 MHz. The frequencies of 410-420 MHz for the uplink 420-430 MHz for the downlink. The data transmission on the control channel at up to 1.2 kbit / s

Digital

Successor of the analog trunked radio is the digital ' terrestrial trunked radio " TETRA or " digital mobile radio " DMR. Both are open standards of the European Institute for standardization in telecommunications and ETSI work including in the frequency band 410-430 MHz. TETRA enables data transfer up to 28.8 kbit / s, after the introduction of TETRA Enhanced Data Service TEDS several 100 kbit / s There are full-duplex connections possible.

Transmission towers

The transmission towers for the trunked radio are usually hard to distinguish from the known GSM transmitters. Only the antenna shape is variable.

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