Mumbai University > Computer Engineering > Sem6 > Mobile Communication and Computing

Marks: 5M

Year: Dec 2015

• The Um interface is the air interface for the GSM mobile telephone standard. It is the interface between the mobile station (MS) and the Base transceiver station (BTS).

• It is called Um because it is the mobile analog to the U interface of ISDN.

• This Air interface (RF Interface) uses the Time Division Multiple Access (TDMA) technique to transmit and receive traffic and signaling information between the GSM’s BTS and the GSM Mobile Station.

• The TDMA technique is used to divide each carrier into eight time slots. These time slots are then assigned to specific users, allowing up to eight conversations to be handled

simultaneously by the same carrier

• The international telecommunication union (ITU) which manages the allocation of radio spectrums has allocated the following bands for GSM air interface:

  • Uplink: 890-915 MHz (Mobile station to Base station)

  • Downlink: 935-960 MHz (Base station to mobile station