Terrestrial Trunked Radio (TETRA) is a specialist Professional Mobile Radio and two-way transceiver, designed for use by government agencies, and specifically emergency services, police forces, fire departments, ambulance, rail transportation staff, transport services, and the military. TETRA is an ETSI standard, first version published 1995. TETRA is endorsed by the European Radio Communications Committee (ERC).
TETRA terminals can act as mobile phones (cell phones), with a direct connection to the PSTN. It is common also for them to operate in a group calling mode in which a single button push will connect the user to a dispatcher and all the other users in a group. It is also possible for the terminal to act as a one-to-one walkie talkie but without the normal range limitation since the call still uses the network. Emergency buttons, provided on the terminals, enable the users to transmit emergency signals, to the dispatcher, overriding any other activity taking place at the same time.
TETRA uses TDMA with four user channels on one radio carrier and 25 kHz spacing between carriers. Both point-to-point and point-to-multipoint transfer can be used. Digital data transmission is also included in the standard though at a low data rate. To send information TETRA uses a digital modulation scheme known as π/4 DQPSK, this is a form of phase shift keying.
The system contains several mechanisms, designed into the protocols and radio parameters, to ensure communication success even during overload situations (e.g. during major public events or disaster situations), thus calls will always get through unlike in cellular systems. The system also supports a range of emergency calling modes.
Unlike the cellular technologies, which connect one subscriber to one other subscriber (one-to-one) then TETRA is built to do one-to-one, one-to-many and many-to-many. These operational modes are directly relevant to the public safety and professional users.
TETRA supports both air-interface encryption and End-to-end encryption.
TI has a wide range of products like ADCs, DACs, DDC, DUC, DSP, Power, clocking, TRF meeting the requirements of Tetra/PMR Base Station designs and plays a strong role in Public Safety.
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