TETRA (Terrestrial Trunked Radio)
Terrestrial trunked radio (TETRA) is the modern digital private mobile radio (PMR) and public access mobile radio (PAMR) technology for police, ambulance, fire, transport and security services. It is use by utilities, the military, public access, fleet management, clodsed user groups, factory site services, mining, etc. In short, TETRA is digital radio.
The standard is defined by the European Telecommunications Standards Institute (ETSI), which established a memorandum of understanding (MoU) in 1994 and now has 56 members across 19 countries. The Technical Body has over 150 representatives involved in the various technical working groups, with support from the TETRA MoU Association providing further expertise in specialist areas. Besides representatives from Europe, activity has now extended worldwide to include the US, China, Asia and the Middle East.
TETRA offers the automatic operation and frequency efficiency of trunking combined with the terminal autonomy of a conventional PMR. TETRA has a multi-mode capability by combining these two modes, trunking and direct (conventional), into a single terminal equipment, and it also provides the standardised way of inter-working between these two modes. TETRA is designed to offer bandwidth-on-demand, a facility to have a variable amount of bandwidth allocated for the call duration, depending on the application.
TETRA is also designed for emergency situations, when almost instantaneous communication is required, both between individuals and within a group of an unlimited size. Priority calls can be made, backed by call pre-emption if required, and on occasions an all-informed communication.
BENEFITS OF TETRA
TETRA offers fast call set-up time, group communication support, direct mode operation between radios, packet data and circuit data transfer services, frequency economy and security features. TETRA uses time division multiple access (TDMA) technology with four user channels on one radio carrier and 25kHz spacing between carriers. This makes it inherently efficient in the way that it uses the frequency spectrum. For emergency systems in Europe the frequency bands 380-383MHz and 390-393MHz have been allocated by a single harmonized digital land mobile system. Additionally, whole or appropriate parts of the bands 383-395MHz and 393-395MHz can be utilized should the bandwidth be required.
For civil systems in Europe, the frequency bands 385-389.9MHz and 395-397.9MHz, 410-420MHz and 420-430MHz, 450-460MHz and 460-470MHz, 870-876MHz and 915-921MHz have been allocated for TETRA.
A TETRA trunking facility provides a pooling of all radio channels, which are then allocated on demand to individual users, in both voice and data modes. By the provision of national networks, countrywide roaming can be supported, the user being in constant seamless communications with his colleagues. TETRA supports point-to-point and point-to-multipoint communications both through the TETRA infrastructure and by use of direct mode without infrastructure.
TETRA standardisation has reached a mature state. The major future developments involve the installation and maintenance of the technology across the world. By the end of 1999, more than 40 infrastructure contracts have been awarded worldwide, with a combined value of $1.5 billion. TETRA systems are being installed in most of the EU and EFTA countries, as well as many of the neighbouring ones, to serve both the emergency services and the civil market.
A pan-European PMR TETRA network is being rolled out, starting with the UK, France and Germany. The emergency services in the UK, Holland, Belgium, Gibraltar, Norway and Finland are using TETRA technology for their nationwide public safety networks, with most of them are already in the process of setting up the network.