TETRA, Trans European Trunked Radio. It was later changed to land-based trunking radio.

Chinese name:泛欧集群无线电

Foreign name:Trans European Trunked Radio

Indentation:TETRA

Then changed to: land-based trunking radio

Services provided: command and dispatch, data transmission and telephone services are provided on the same technical platform

Supported Functions: Mobile platform off-network pass-through mode, enabling authentication, air interface encryption, and end-to-end encryption

TETRA简介

Introduction to TETRA

TETRA(Trans European Trunked Radio, has been changed to Terrestrial Trunked Radio - Terrestrial Trunked Radio) Digital trunked communication system is a professional mobile communication system based on digital Time division multiple access (TDMA) technology. This system is an open system designed and formulated by ETSI(European Communication Standards Association) to meet the needs of professional departments in European countries for mobile communication. It was put into use in 1988, and now it has become the European standard. At the same time, like GSM, it has been adopted by countries and regions outside Europe, including the United States, and has considerable development potential.

TETRA digital trunking communication system can provide command dispatching, data transmission and telephone service on the same technical platform. It not only provides multi-group dispatching function, but also provides short data information service, packet data service and digital full-duplex mobile telephone service. The TETRA digital trunking system also supports a powerful mobile station off-network passthrough (DMO) mode for authentication, air interface encryption, and end-to-end encryption. The TETRA digital trunking system also has a virtual private network capability that enables a single physical network to serve multiple unrelated organizations. TETRA digital cluster system has rich service functions, higher frequency utilization, high communication quality, flexible networking mode, many new applications (such as vehicle positioning, image transmission, mobile Internet, database query, etc.) have been realized in TETRA. Therefore, TETRA digital cluster system has developed rapidly in Europe and even the world in the past two years.

Introduction to TETRA business

According to different access points, the basic services of TETRA can be divided into bearer services and user terminal services.

TETRA supports the following user terminal services: single call (point-to-point), group call (point-to-multipoint), response group call, broadcast call (one-way point-to-multipoint), and open or secret call.

TETRA supports bearer services including packet data and circuit data.

The bearer service provides the following user bit rates:

·Unprotected voice or data is 7.2kb/s(Up to the maximum28.8kb/s);

·Data with low protection is 4.8kb/s(Up to the maximum19.2kb/s);

·Data with high protection is2.4kb/s(Up to the maximum9.6kb/s)。

Supplementary services supported by TETRA include: professional dispatch type supplementary services and telephone type supplementary services. Professional scheduling supplementary services include: access priority, pre-occupied priority, priority call; Call tolerance, dynamic transfer, late entry; Call, monitor and listen for verification by dispatch station; Regional selection; Abbreviated addressing; Speech recognition; Dynamic recombination, etc. Supplementary services of the telephone type include: list search call, call transfer, call restriction, call reporting, call waiting, call hold, calling/called Party Identification display, calling/called party identification Display restriction,

Call completion to busy user/to no answer; Billing notice; Call retention, etc. Supplementary services apply to most bearer services and user terminal services.

History of TETRA's development

1989: MDTRS standardization;

1990:7 technical proposals submitted by 6 manufacturers;

1991: Select TETRA technology;

1995: The main standard of TETRA was published, and the basic system was put into test;

1997: Completed 380-400 MHz band system;

1998-2000 Extended frequency band and improved functions.

Technical characteristics

Fast call establishment;

Variable time-slot data transmission;

Scheduling function (group call, priority, etc.);

Direct mode (off-network operation);

Space encryption + end to end encryption;

High frequency spectrum utilization, 4 channels within 25KHz;

Open standards, extensible.

TETRA advantages

TETRA system is a very flexible digital cluster standard. Its main advantages are good compatibility, good openness, high spectrum utilization rate, and strong security capability. It is the most elaborate digital cluster standard in the world, with good openness, the most advanced technology and the largest number of participating manufacturers.

Application of TETRA

Typical applications of TETRA include transportation, public utilities, industry, public safety, police official applications, fire emergency operations, etc.

Operating frequency

TETRA operates at 350MHz and 806MHz~866MHz.

Cluster mode

The TETRA standard supports three clustering modes: message clustering, transport clustering, and quasi-transport clustering. Message clustering is the control system always assigns a fixed wireless channel to the user during the scheduling call. After the user releases the PTT switch after the last speech, the system will wait for the "channel retention time" of 6 s to 10 s, and then the message cluster will be completed after the "off-network", and then the channel will be allocated to other conversation pairs. If, during this retention period, the original subscriber presses the PTT switch again to continue the conversation, the two parties are still talking on this channel, that is, the original channel allocation is maintained. Message cluster is not channel dynamic allocation mode but demand allocation mode, so the spectrum utilization is not high. 

Transmission cluster refers to that when both users work in simplex or half duplex, the user presses the PTT switch to occupy an idle channel. When the user releases the PTT switch after sending the first message, there is a "finished transmission" signaling sent to the controller of the base station, which is used to indicate that the channel can be reassigned to other users. The channel of transmission cluster is dynamically allocated, which has high spectrum utilization rate, but may lead to discontinuous and incomplete calls. 

Quasi-transmission cluster combines the advantages of message cluster and transmission cluster, shortens the "channel retention time" (about 0.5s ~ 6s), and increases the time after releasing the PTT switch after each call is made, without interrupting the message. The channel utilization of the quasi-transport cluster is lower than that of the transport cluster. 

TETRA spectrum resources

The distinguishing feature of the TETRA standard is the flexibility of its frequency resources. The spectrum ranges from 150 MHz on VHF to 900 MHz on UHF, with a 10 MHz interval between transceiver frequencies (45 MHz at 900 MHz).