MS-Mobile Station Wireless communication devices that use the air interface which is the SIM (Subscriber Identity Module) that connects customers with the BTS. MS consists of:

ME (Mobile Equipment)
ME consists of the radio functions and user interface and terminal equipment to the other. ME identification have a serial number called IMEI.

SIM (Subcriber Identity Module)
Contains information about users that can be used with ME. Access to that used to form a GSM smart card that can control various functions. There are a number of others in the SIM IMSI, TMSI, Ki, Algorithm A3 and A8, memory phone number, PIN. Communication that occurs from the MS to the BTS (Base Station Transceiver) is a radio communication through electromagnetic waves, and in transmitter MS from the antenna to antenna receiver in the BTS through the air interface.

Consists of 2 channels on the air interface channel on the GSM namely:

• UP Link (MS to the BTS) 890 - 915 MHz.

• Down Link (BTS to MS) 935 - 960 MHz.