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TETRA
(TERRESTRIAL TRUNKED RADIO)
MOBILE TELEPHONE TECHNOLOGY
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 TECHNOLOGY
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.
THE FUTURE
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.
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