TETRA was used during the French TGV train speed record on 3 April 2007 at 574.8 km/h. * very fast call set-up - a one to many group call is generally set-up within 0.5 seconds (typical less than 250 msec for a single node call) compared with the many seconds (typically 7 to 10s) that are required for a GSM network.
* High spectral efficiency - 4 channels in 25 kHz and no guard bands, compared to GSM with 8 channels in 200 kHz and guard bands. * the much lower frequency used gives longer range, which in turn permits very high levels of "geographic" coverage with a smaller number of transmitters, thus cutting infrastructure costs. The main advantages of TETRA over other technologies (such as GSM) are: TETRA provides both over the air encryption and end-to-end encryption. Status messages and short data services (SDS) are provided over the system's main control channel, while Packet Data or Circuit switched data communication uses specifically assigned traffic channels.Īll traffic is normally encrypted. In addition to voice and dispatch services, the TETRA system supports several types of data communication. In rescue situations this feature could allow direct communications underground or in areas of bad coverage. This functionality is called DMO gateway (from DMO to TMO) or DMO Repeater (DMO to DMO). As well as allowing direct communications in situations where network coverage has been lost, Direct Mode or DMO also includes the possibility of using one (or a chain) of TETRA terminals as relays for a signal. TETRA Mobile Stations (MS) can communicate Direct Mode or using Trunked infrastructure (Switching and Management Infrastructure or SwMI) made of TETRA Base Stations (TBS). Digital data transmission is also included in the standard though at a low data rate. Both point-to-point and point-to-multipoint transfer can be used.
TETRA uses Time Division Multiple Access (TDMA) with four user channels on one radio carrier and 25 kHz spacing between carriers. 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. 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. 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. TETRA terminals can act as mobile phones ( cell phones), with a direct connection to the PSTN. TETRA is endorsed by the European Radio Communications Committee (ERC) and mandated for use in Europe. TETRA is an ETSI standard, first version published 1995. TETRA was specifically designed for use by government agencies, emergency services, ( police forces, fire departments, ambulance), rail transportation staff, transport services and the military.
For other uses, see Tetra (disambiguation)" TErrestrial Trunked RAdio ( TETRA) (formerly known as "Trans European Trunked RAdio") is a specialist Professional Mobile Radio and two-way transceiver (colloquially known as a walkie talkie) specification.