Tetrapol

TETRAPOL is a digital cellular trunked radio system for speech and data transmission, which is specially tailored to the area of ​​public safety. Trunked radio systems are professional radio systems for closed user groups such as private mobile radio applications or radio of authorities and organizations with security tasks ( BOS). Unlike other mobile radio systems, where each available transmission channels are only a dedicated group of users to available, are distributed all available channels according to requirements of the different groups in the trunked radio. Thus the total number of potential users increases. The radius of a TETRAPOL cell is up to 28 kilometers.

Development

TETRAPOL was originally developed by Matra and the European Aeronautic Defence and Space Company EADS for the French security forces. Among the first users belonged to the French Gendarmerie, where TETRAPOL is already being used successfully since 1988. There are now 80 TETRAPOL-N etworks in 34 countries. EADS is the only manufacturer of TETRAPOL technology and has already begun, with the help of a self-initiated for this purpose association to establish TETRAPOL as the industry standard.

Areas of application

Unlike the public mobile GSM as the use of trunked radio to a particular region is limited. A so-called hand -over - ie the passing from cell to cell during a call - is not provided.

Tailor-made for all areas of public safety as the Bundeswehr TETRAPOL is mainly because of service options such as group call, or the possibility that two or more mobile stations without an intermediate base station can communicate directly with each other. As the office of the forces can draw with TETRAPOL on Information systems and databases while 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. With the help of digital radio such information is communicated eavesdropping by voice or data transmission to the respective task forces.

Similarly, the TETRAPOL technology can be installed as a radio network. In such wireless communication systems, for example, staff in the plant security, fire service, maintenance, or from the high-bay warehouse on digital radio can be connected together. Previously, employees had to fight through a number of different notification systems.

Nevertheless, the combined within a TETRAPOL network groups operate completely independent of each other. The change from one group to the other is in the digital system naturally without any hassle possible. For this, the system administrator only needs to " unlock " the desired group access. Mostly this is already done when setting up the system. Users will be accurately perceived this fact as very beneficial, not everyone has to listen to the system all that they can connect to the respective group radio networks that are of concern to him.

Operation

Unlike the earlier analogue fixed channel systems where each service or each user a specific radio channel was assigned to fixed all the time, the frequencies are assigned to the individual participant and services dynamically trunked radio systems. Thus, the so-called trunk gain is exploited and increasing the spectrum efficiency depends on the type of use to often many times. As a channel access method TETRAPOL developers chose the frequency division multiplexing ( FDM or FDMA). FDMA is the classical channel access method in which each user is assigned a specific frequency for a connection. Can thereby be transmitted and received simultaneously. This procedure - other things being equal - a greater range and thus better coverage of large areas as with other channel access method reached ( eg, TDMA). At the same time, the base station sends each radio cell continuously from one control signal. In this control channel, the base station supplies the connected mobile devices running the current system data of the network. TETRAPOL can in principle be used at frequencies 70-520 MHz., 160 - - In practice, however, only the typical designated for PMR frequencies in the 80 to 400 MHz band are used. The frequency division duplexing method is used also in TETRAPOL as in most radio systems. The uplink and downlink are carried on two different frequencies, which are distinguished from each other by the so-called duplex spacing.

Compatibility

Due to the proprietary wireless standard, there are no compatibility with other wireless systems. Tetrapol works with FDMA, TDMA TETRA contrast with. Over the air interface, an interaction is possible.

Telephone services

  • Individual Call ( Individual paging ): This service corresponds to the compound in a public mobile telephone system (GSM, UMTS). A user calls another other user and is connected with this.
  • Group Call ( Group Call ): A user calls a predefined group. Each member of the group can hear everything and also have a say. A group can be modified dynamically, so it can be added or removed members.
  • Direct Mode: In direct mode, two or more mobile stations to communicate without involving a base station directly. This can be used in places where there is no radio coverage is available - for example, in a tunnel or the basement of a building.
  • Broadcast Call: This is a unidirectional point-to- multipoint connection in a given area. The area and participants will be determined in advance. The individual participants do not acknowledge the call, and it can therefore no control over the caller be maintained of who has received the call or not.
  • Emergency Call ( Emergency ): An emergency call button sets up high-priority call to a dispatcher or a predefined group of users can be built.
  • Include call: This call makes it possible to call one or more additional participants during a conversation and engage in conversation.
  • Open Channel (open voice channel ): A group of participants can be on a certain channel, during a certain time, talk to each other. Within the group, everyone hears each and can speak at any time. To participate in the call, the subscriber only needs to enter the number of the " talk group ". The numbers of the active at a specific time " talk groups " is sent on the control channel, and all stations in the network is known.

Data services

  • Paging: From a dispatcher short messages to the mobile station can be sent.
  • Status Transmission: very short, predefined messages can be sent from the dispatcher to the mobile stations and vice versa, or between mobile stations.
  • Short Data Messaging: This data service allows participants to quickly exchange short messages.
  • X.25 Packet Data Services: This data service allows you to set up an X.25 link between two terminals.
  • TCP / IP Access: This data service allows the mobile stations access to the Internet or to servers that support the TCP / IP protocol.
766395
de