Mobile station

A mobile station (MS)^[1][2] comprises all user equipment and software needed for communication with a mobile network.

The term refers to the global system connected to the mobile network, i.e. a mobile phone or mobile computer connected using a mobile broadband adapter. This is the terminology of 2G systems like GSM. In 3G systems, a mobile station (MS) is now referred to as user equipment (UE).

In GSM, a mobile station consists of four main components:

• Mobile termination (MT) - offers common functions of a such as: radio Transmission and handover, speech encoding and decoding, Error detection and correction, signalling and access to the SIM. The IMEI code is attached to the MT. It is equivalent to the network termination of an ISDN access.
• Terminal equipment (TE) - is any device connected to the MS offering services to the user. It does not contain any functions specific to GSM.
• Terminal adapter (TA) - Provides access to the MT as if it were an ISDN network termination with extended capabilities. Communication between the TE and MT over the TA takes place using AT commands.
• Subscriber identity module (SIM) - is a removable subscriber identification token storing the IMSI a unique key shared with the mobile network operator and other data.

In a mobile phone, the MT, TA and TE are enclosed in the same case. However, the MT and TE functions are often performed by distinct processors. The application processor serves as a TE, while the baseband processor serves as a MT, communication between both takes place over a bus using AT commands, which serves as a TA.

Working of Mobile Station

The complete operation of a Mobile Station can be divided into four different phases of operation:

1. Initialization Phase

2. Cell Selection Phase

3. Idle Phase

4. Dedicated Mode

Initialization Phase: Initialization of Mobile Station is the first phase that prepares the mobile for further phases of operation. Initialization phase begins as soon as the mobile is switched on. Initialization can be accomplished with or without SIM (Subscriber Identity Module). However, initialization without SIM does not allow mobile to initiate or receive any calls. Some mobile operators allow emergency calls even without SIM. In the case of initialization with SIM, the mobile station uses this identity of the SIM to establish a connection with the home network. SIM can be set to ask for a PIN number every time it is inserted into a new mobile station.

Cell Selection Phase: A mobile station can receive signals from more than one transmitting stations but it connects to a single network that has the strongest signal. Each cell has its unique transmitting station and thus by selecting the strongest network, a mobile station selects the nearest cell.

Idle Phase: Once a mobile station is connected to the strongest network, it goes into an ideal phase where it waits for the network to initiate any incoming calls.

Dedicated Mode: When a mobile station receives an incoming call and accepts it, a communication channel is reserved between the mobile station and the network as long as the call continues. Thus, the communication channel works as the dedicated channel and this mode is referred as the dedicated mode.

See also

References

1. "GSM 04.02, V3.0.2". ETSI. February 1992.
2. "3GPP 24.002, V9.0.0". ETSI. January 2010.