TETRA – Taking Military Technology into the Everyday World

Since 1995 TETRA has become a major requirement in military communications projects. David Mackay looks at how 13 years down the line, TETRA research is now escaping its military origins and being adopted in everyday life.


Communication has long been a priority for military operations, but the challenges in getting it right, and secure, are many. You only have to look at the old case of 'the bridge too far' at Arnhem. But it is not only the military that has complications with communications. The King's Cross Underground fire in 1985, in which 31 people died, could have been a lot less catastrophic with the right communications in place.

For years, every generation of new radio system has attempted to overcome the generic problems of bandwidth, range and frequency spectrum. The latest improvements arrived in 1995 with TETRA (terrestrial trunked radio).

TETRA is a digital trunked mobile radio standard developed by the European Telecommunications Standards Institute (ETSI) which aims to meet levels of interoperability required when developing infrastructure and radio terminal products.

Designed initially for the military, TETRA was first deployed in 1997 and there are now hundreds of TETRA systems throughout the world. It is a major innovation and today the TETRA Association represents over 150 organisations from more than 35 countries who are involved in the development and or deployment of the global standard for TETRA.

"The ability to communicate consistently is the fundamental requirement for all military operations."

The armies of many nationalities have always pushed for development and trial of technology, such as the developments pioneered by ARPA and NASA in the USA. The ability to communicate consistently is the fundamental requirement for all military operations, as well as all police and emergency service activities.

The purpose of the TETRA standard is to meet the needs of traditional professional mobile radio (PMR) user organisations such as public safety; transportation; utilities; government; military; public access mobile radio (PAMR); commercial and industry; and oil and gas utilities.

Since the advent of digital communications, incompatible protocols have been a major problem in interoperability between different pieces of equipment. The TETRA standard means that the air interfaces, network interfaces, services and facilities are specified in sufficient detail to enable independent manufacturers develop infrastructure and radio terminal products to fully interoperate with each other, allowing, for example, radio terminals from different manufacturers can operate on infrastructures from other manufacturers.

Public safety is the largest TETRA market today and involves the deployment of shared nationwide networks, operational autonomy and interoperability with other services during emergencies.

"TETRA is a digital trunked mobile radio standard developed by ETSI."

Asia is the fastest growing TETRA market and there is also significant European growth.

Transportation is the next fastest growing area, particularly when involving mass rapid transport systems and major airports. TETRA is also deployed on military non-tactical operations, an application not part of the original specification, but stems from the constant need for military and emergency services training.

HOW TETRA WORKS

The ability for full interoperability between different manufacturers' products is a distinct advantage of the open standards developed by ETSI. The TETRA standard is supported by independent manufacturers and this increases competition, provides second source security and allows a greater choice of terminal products for specific user applications.

While still competing in the market, TETRA ensures that manufacturers are also collaborating for the benefit of end users. And, besides meeting the needs of traditional PMR user organisations, the TETRA standard has also been developed to meet the needs of PAMR operators.

TETRA security is extensive, as it needs to provide different levels ranging from what is acceptable on commercial networks to what is acceptable on a national military or public safety network. The security structures are provided by authentication, air interface encryption (AIE) and end-to-end encryption. The threats to confidentiality, authenticity, integrity, availability and accountability are delivered by these measures.

Mutual authentication ensures that a TETRA system can control access to it, as well as enabling a radio terminal to check if a network can be trusted. This authentication is fundamental for network security. It also produces validated billing in public access systems and a secure distribution channel for sensitive information such as other encryption keys. The mutual authentication security mechanisms protect both voice and data services. These measures have been welcomed by the communications market as vital enhancements.

There are four TETRA algorithms (TEAs) that support network use. TEA2 is used by public safety networks in European Schengen-related countries; the other TEAs have wide applications in regions where TEA2 is not used. The principal benefit of over the air encryption is that it protects all signalling and identities, as well as user speech and data. This provides robust protection from traffic analysis as well as from eavesdropping.

"The ability for full interoperability between different manufacturers' products is a distinct advantage."

TETRA can also support a wide range of security management capabilities; the most important of these is encryption key management, which is fully integrated in TETRA standard functions. Using this, the security risks are condensed to specific elements in the network, which can be adequately controlled.

The TETRA standard supports various end-to-end encryption algorithms for national security organisations. The TETRA Association Security and Fraud Prevention Group has now defined a general framework for the incorporation of end-to-end encryption.

TETRA APPLICATIONS

The peripheral equipment interface (PEI) standardises the connection of the radio terminal to an external device. It supports data transmission between applications within the device and the connected TETRA radio terminal. The PEI supports applications such as: alarm reporting; telemetry; bus ticketing machines; train borne systems; automatic vehicle location (AVL); mobile data terminals; desktop consoles; command and control.

The PSTN/ISDN/PABX interface enables TETRA to interface with the PSTN, the ISDN and PABXs. One of TETRA's main strengths is the standardised Inter-System Interface (ISI) which permits interoperability between different infrastructures from different manufacturers.

TETRA enables conventional PMR trunking problems to be resolved. Time division multiple access (TDMA) was adopted in TETRA to balance the cost of equipment, the services and facilities required by users for a medium to high capacity network providing single site local RF coverage and/or multiple site wide area RF coverage.

TETRA utilises the latest trunking technology and achieves higher data rates because TDMA uses wider channels than FDMA, therefore combined data rate on a single RF carrier is greater. The TETRA standards have brought about improved data throughput in poor RF conditions. In addition, it has devised a solution for bandwidth on demand.

"TETRA ensures that manufacturers are collaborating for the benefit of end users."

It also improves concurrent voice and data requirements; the TDMA time slot structure is able to assign the first time slot to support voice and the next time slot to support data in a two slot transmission from radio terminals. This capability effectively allows a single radio terminal to concurrently transmit or receive voice and data at the same time. This is an impressive improvement to previous systems.

TETRA also provides full duplex voice communications as TDMA technology supports full duplex communications.

WHO IS USING TETRA?

The British Army have long praised TETRA for its improved capabilities. In the past, cellular communications were patchy, but the TETRA-compatible equipment now enables the army to maintain excellent communications throughout. Major Cartwright of 43 Wessex Brigade says: "TETRA provided a communications system which was far superior in terms of quality, capacity and reliability than previous systems. We also needed to use fewer pieces of equipment than in the past."

Airwave, the new major UK digital communications system deployed by all emergency services, has completed its initial run in Scotland. The Scottish Police Forces launched a joint procurement exercise and the resulting system and equipment is fully TETRA compatible; "This has been a major advance for police communications in Scotland" says the Association of Chief Police Officers in Scotland (ACPOS): "We will be trialling the system over the next few years, but are very pleased with initial reports," says the ACPOS spokesman.

There has been major use in Sweden of TETRA equipment. The Prison and Probation Service public-safety agency has now joined the TETRA network, along with the Swedish Police.

"TETRA enables conventional PMR trunking problems to be resolved."

Zenitel Radioteknik have a contract with the Swedish Road Authority to equip Stockholm's largest tunnel complex, Södra Länken, with coverage for the national public safety TETRA network. This is the second major Swedish contract for Zenitel Radioteknik; they already have one for the Öresund Link, as well as the Danish TetraNet public safety network.

Zenitel also have another TETRA solution being implemented for a large Swedish nuclear power plant to provide plant communication and critical communication in emergencies.

TETRA is also in use in Lima, Peru, for protection duties in the city's historic district. Thales has supplied a digital infrastructure that will be expanded throughout the city over time. Hungary, with its 42,000 public safety users, has also installed a TETRA system.

The Chinese Ministry of Public Security has chosen TETRA equipment as the standard for the Chinese police. This is probably one of the biggest TETRA applications in the world. At the other end of the scale, the city of Aix-en-Provence, in France, uses TETRA radios for its municipal organisations and plans to implement a portable TETRA system for use in emergency and crisis situations as well as major sports or cultural events. This will replace the existing analogue radio communication system.

"TETRA allows a single radio terminal to concurrently transmit or receive voice and data at the same time."

There are many police forces, ambulance services and public transport organisations, military customers from the US Department of Defense to the armies of Greece, Norway, South Korea and the UK, as well as fire brigades, municipal and utilities customers. Commercial users include Air France, Russian Railways, Petroleum Development Oman, Saudi Electricity Company, China Light and Power, Volvo, BMW, and the airports of Hannover and Madrid.

TETRA contracts worldwide are in excess of 1,400 in total. The market sectors are as follows:

  • Public safety – 48%
  • Transportation – 21%
  • Utilities – 7%
  • Various – 5%
  • Government – 5%
  • Commercial and industrial – 5%
  • Military – 4%
  • PAMR – 3%
  • Oil and gas – 2%

TETRA has also been deployed in many regions and nations outside Europe, thus becoming a truly global standard and will develop similar to GSM. 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.