TETRA is a modern standard for digital Private Mobile Radio (PMR) and Public Access Mobile Radio (PAMR). It offers many advantages including flexibility, security, ease of use and offers fast call set-up times. This makes it an ideal choice for many business radio communications requirements.
The name TETRA stands for TErrestrial Trunked RAdio.
It is aimed at a variety of mobile radio communications users including the police, ambulance and fire services, it is equally applicable for utilities, public access, fleet management, transport services, and many other users. It offers the advantages of digital radio whilst still maintaining the advantages of a PMR system.
Work started on the development of the TETRA standards in 1990 and has relied on the support of the European Commission and the ETSI members. Experience gained in the development of the highly successful GSM cellular radio standard, as well as experience from the development and use of trunked radio systems has also been used to fashion the TETRA standard. In addition to this the process has gained from the co-operation of manufacturers, users, operators and industry experts. With this combined expertise the first standards for the new private mobile radio communications system were ready in 1995 to enable manufacturers to design their radio communications equipment to interoperate successfully.
TETRA digital trunked mobile radio for voice and data has found international acceptance and a growing market in the Asia/Pacific region. Its success has been mainly due to compliance to an open standard of the European Telecommunications Standards Institute (ETSI). Further,the ETSI TETRA standard received significant input from the various manufacturers and prospective users by way of the TETRA Memorandum of Understanding Association. This international body known as the TETRA MoU or TETRA Association has been primarily responsible for the fast tracking of the ETSI TETRA open standard and air interface compatibility compliance testing between subscribing manufacturers.
The aim of the TETRA MoU was to create a forum that would act on behalf of all interested parties, i.e. users, manufacturers, application providers, integrators, operators, test houses and telecommunications agencies.
The TETRA Association represents more than 150 organisations and is continually growing as the TETRA standard is evolved and the uptake has increased.
The basic aims of the TETRA Association remain the same as that of the original TETRA MoU - providing a forum for all those interested in TETRA; to encourage adoption of the standard; and to support initiatives to obtain appropriate levels of spectrum to meet the growth in TETRA radio usage.
In view of its aims, the TETRA Association works closely with ETSI to maintain and advance the standards.
TETRA radio features
TETRA radio offers many new and valuable features and in this way it is a major step forwards over previous private mobile radio communications systems. These include a fast call set-up time, which is a particularly important requirement for the emergency services. It also has excellent group communication support, direct mode operation between individual radios, packet data and circuit data transfer services, better economy of frequency spectrum use than the previous PMR radio systems and in addition to this it provides advanced security features. The system also supports a number of other features including call hold, call barring, call diversion, and ambience listening.
The TETRA radio standard has undergone an evolutionary development to ensure that it is able to keep up with the needs of the users. There have been two releases of the TETRA radio standard.
TETRA Release 1
As would be envisaged this was the first release of the TETRA radio standard which occurred
TETRA Release 2
- This release of the TETRA radio standard occurred in 2005 as a result of work dating back to 1999. It introduced a number of new features into the TETRA radio standard:
- TETRA Enhanced Data Service (TEDS)
- Mixed Excitation Liner Predictive, enhanced (MELPe) Voice Codec
- Adaptive Multiple Rate (AMR) Voice Codec
- Trunked Mode Operation (TMO) Range Extension
- Of these enhancements, it is the TETRA TEDS that has caught the headlines as the main enhanced feature, although the others all add to the overall package.
The TETRA radio system offers many features that enable it to have more flexibility than many other systems.
- The TETRA 1 radio systems provide the major features, and although further development to TETRA 2 and TEDS have enabled further facilities to be added, they still retain the TETRA 1 capabilities and are backward compatible. In this way, TETRA 1 forms the basis for all TETRA radio systems.
There are three different modes in which TETRA radio systems can be run:
Voice plus Data (V+D)
Direct Mode Operation (DMO)
Packet Data Optimised (PDO)
The most commonly used mode is V+D. This mode allows switching between speech and data transmissions, and can even carry both by using different slots in the same channel. Full duplex is supported with base station and mobile radio units frequencies normally being offset by about 10 MHz to enable interference levels between the transmitter and receiver in the station to be reduced to an acceptable level.
DMO is used for direct communication between two mobile units and supports both voice and data, however full duplex is not supported in this mode. Only simplex is used. This is particularly useful as it allows the mobile stations to communicate with each other even when they are outside the range of the base station.
The third mode, PDO is optimised for data only transmissions. It has been devised with the idea that much higher volumes of data will be needed in the future and it is anticipated that further developments will be built upon the TETRA mobile radio communications standard.
For more information on TETRA Contact AA Radio
AA Radio is a member of the Australasian TETRA Forum