Tetra network
Tetra is a trunked radio with radio cells. Like a GSM network, the Tetra network is a radio cell-based network in which the mobile radios communicate with the Tetra Base Station (TBS).
The Tetra network does not have a Base Station Controller( BSC) like the GSM network; in Tetra, the base stations are directly connected to an exchange, which in turn communicates with other exchanges, Digital Exchange for Tetra (DXT), and the Dispatcher Station( DST).
The transition of a mobile station to another base station occurs automatically when a base station with higher field strength is detected. Roaming between different Tetra networks is possible via the Inter System Interface( ISI), a unified interface for communication between different Tetra networks.