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TETRA - Terrestrial Trunked Radio

TETRA is an open standard developed by the European Telecommunications Standards Institute (ETSI). The main purpose of the TETRA standard was to define a series of open interfaces, as well as services and facilities, in sufficient detail to enable independent manufacturers to develop infrastructure and terminal products that would fully interoperate with each other as well as meet the needs of traditional PMR user organisations.

The initial responsibility of ETSI Project TETRA (now known as ETSI Technical Committee (TC) TETRA) was to deliver as set of standards, under a mandate from the European Commission, for a Digital Trunked PMR communications system that could be deployed in Western Europe. As well as producing these mandatory ETSI deliverables (now completed), TC TETRA's responsibility was, and still is, to make sure that the portfolio of standards continue to be developed in accordance with user needs and priorities.

The technology solutions chosen to meet user requirements contained in the TETRA standards have been, and continue to be, developed primarily by well know and respected manufacturers who have been serving the PMR market with products and services for several decades. This combined 'Know How' ensures that optimum technology solutions are chosen to meet user requirements. Details of manufacturers can be viewed on the members page of the TETRA Association by clicking on the left hand menu under core products.

Although the prime responsibility of ETSI is to develop standards for Europe, many of its standards are also adopted world-wide, as evidenced by the uptake of GSM, the first wireless technology standard to be developed by ETSI. Similarly, TETRA has already been deployed in many regions and nations outside Europe, resulting in TETRA becoming a truly global standard.

There is no doubt that a proprietary technology solution can be brought to market in less time than a solution conforming to a recognised open standard. However, large user organisations, especially those in the public sector, have recognised that some proprietary solutions can meet their needs but the 'tie in' to a single supplier can have significant disadvantages. Even though there are some disadvantages, the main advantages and benefits of adopting an open standard are:

Because there are several independent manufacturers of both TETRA network infrastructure and radio terminals all the benefits of standardisation listed also apply to the TETRA market.

Evolution & Longevity

The ETSI TETRA standard will continue to evolve beyond Release 1 and Release 2 to provide additional enhancements as driven by user needs, technology innovations and other parallel standard developments. As a consequence, ETSI has no plans to develop a new technology standard for use by large traditional PMR user organisations. Similarly, other technology standards being developed and/or available outside Europe offer little or no benefit over what TETRA already provides.

This planned evolution of TETRA can be appreciated when considering that traditional PMR user organisations will always require private PMR networks because public networks cannot adequately provide the required RF coverage, Grade of Service (GoS) during busy periods and high levels of reliability. Besides these basic needs, public networks will not be able to provide the specialised voice services such as wide area fast call-set up all informed nets (group calls), Direct Mode Operation (DMO) and high levels of secure encryption for voice and data.

In summary, TETRA will evolve in a similar way to GSM, which evolved from providing a basic V+D 'one to one' telephony service (via GSM II+, GPRS, EDGE, etc.) to UMTS/3G supporting powerful multimedia applications and High Speed Data. Also, the focus and technology solution for Next Generation Networks (NGN) will primarily be for public networks.

Taking these previous factors into consideration and the fact that analogue MPT 1327 trunking networks are still being deployed across the world more than 28 years after the technology was first developed, TETRA networks are expected to be available for at least another 25 years, thereby ensuring a very good return on investment for user organisations as well as manufacturers and suppliers.

TETRA Applications

An important advantage of the TETRA standard is that it has a number of open interface specifications that can be used by application developers to further enhance the capabilities of TETRA. Similarly, manufacturers are able to provide (under license) details of their proprietary interface specifications in support of specific applications. Figure 1 shows all the interfaces on TETRA, some of which can be used by application developers.

TETRA Standard Interfaces

The interface specifications that are commonly used by application developers are described as follows.

Air Interfaces (1 & 2)

To utilise the air interface, application developers often use the Peripheral Equipment Interface (PEI) (described later) or a manufacturer specific interface on radio terminals for applications.

Man-Machine Interface MMI (3)

Peripheral Equipment Interface (4)

This interface standardises the connection of the radio terminal to an external device, and supports data transmission between applications resident in the device and the connected TETRA radio terminal. The PEI also supports certain elements of control within the radio terminal from the external device and/or applications such as:

Remote Dispatcher Interface (5)

As this interface has not been standardised only TETRA manufacturer specific interface specifications are available to support the many voice and data applications requiring access to TETRA infrastructures.

PSTN/ISDN/PABX (6)

This standardised interface enables TETRA to interface with the PSTN, the ISDN and/or PABXs as required by both user organisations and application developers.

Inter-System Interface (7)

This standardised Inter-System Interface (ISI) allows infrastructures supplied by different TETRA manufacturers to inter-operate with each other allowing interoperability between two or more networks. There are two methods of interconnection in the standard, one covering information transfer using circuit mode and the other using packet mode. Application developers are expected to utilise this interface when it becomes available on TETRA networks.

Network Management Interface (8)

As this interface has not been standardised only TETRA manufacturer specific interface specifications are available to support the many network management applications requiring access to TETRA networks.

Application developers

Because of the and success of TETRA, as well as the many applications required by traditional PMR user organisations, there are a wide variety of applications available from numerous application providers. Further details can be found on the TETRA Association member's page (members). Once the membership list has been accessed, use the left hand menu to link to application providers.

Other Applications

With the traditional PMR market segments TETRA is often used for specialist applications such as operation of terminals in Hazardous Environments and Public Protection & Disaster Relief (PPDR). More information on these special applications can be found by clicking the highlighted links.