terrestrial flight telephone system (avionics) (TFTS)

Terrestrial Fight Telephone System (TFTS) is a cellular airborne telephone system standardized by the European Telecommunications Standards Institute( ETSI). It is a terrestrial cellular system that enables telephony from aircraft with a direct air-to- ground connection without satellite switching. It establishes an immediate full- duplex connection with direct dialing to the fixed network. In TFTS, several technical parameters were adopted from the GSM system.

A TFTS network consists of the air station( AS, Air Station), the ground station( GS, Ground Station) and the switching center (GSC, Ground Switching Center). Depending on the power of the ground station, aircraft can be reached at a distance of up to 400 km at altitudes of between 5,000 m and 13,000 m. For ground stations with lower power, connections close to the airport are possible. The ground stations allow connections to be handed over in the form of a handover. The switching centers control the earth stations and establish the connections to the fixed networks.

TFTS operates in the 1.8 GHzfrequency range, at uplink frequencies from 1.670 GHz to 1.675 GHz and downlink frequencies between 1.800 GHz and 1.802 GHz. The channel sp acing is 30.3 kHz. Transmission is digital, based on time division multiple access( TDMA). Each aircraft has four channels with a transmission rate of 9.6 kbit/s.

In total, a TFTS system provides 164 radio channels for up to 2,000 voice channels. In addition to voice transmission, TFTS also offers a Group 3 fax service, as well as other non-voice services.