Controls GSM's Base Station System. It is responsible for controlling many radio related functions, for example the allocation of radio channels to calls. The BTS is the functional entity in GSM's Base Station System which handles the radio interface to the Mobile Station. The BTS is the functional entity in GSM's Base Station System which handles the radio interface to the Mobile Station. MSC communicates with an RBS in service areas that do not have their own switch. Controls GSM's Base Station System. It is responsible for controlling many radio related functions, for example the allocation of radio channels to calls. Provide special services including emergency handling, short messaging, call waiting, call barring, call forwarding and the ability to communicate with other subscribers. Two directional channel. Uplink and Downlink. In digital transmission, the quality of the transmitted signal is often expressed as the Bit Error Rate. The BER is the percentage of faulty bits detected out of the total number of bits transmitted. Information sent during a time slot on a TDMA channel. Ericsson systems and services for transmitting voice, data, text and images over private networks, wireless business communication, data networks and telephone equipment, planning and installing communications and data networks, network products.