More on GSM architecture

Mobile station (MS):
The MS comprises all user equipment and software needed for communication with GSM network .An MS consist of user independent hard end software and of the subscriber identity module(SIM), which stores all the user-specific data that is relevant to GSM .While an MS can be identified via international mobile equipment idenetity (IMEI), a user can personalize any MS using his/her SIM.i.e user-specific mechanism like charging and authentication are based on SIM,not on the device itself.Device -specific mechanism,e.g theft protection ,use the device specific IMEI.Without the SIM,only emergency calls are possible .The SIM contains many identifiers and tables ,such as card type ,serial number ,a list of subscribed services , a personal identity number (PIN),a PIN unblocking key(PUK),an authenticatin key and international mobile subscriber identity (IMSI).The PIN is used to unlock the MS .Using the wrong PIN three times will lock the SIM.Insuch cases,the PUK is needed to unlock the SIM .The MS stores dynamic information while logged into the GSM systems,such as ,e.g the cipher key and location information consisting of temporary mobile subscriber identity (TMSI)and the loacation area identification (LAI).Typical MSs for GSM 900 have a transmit power of upto 2 W ,whereas the GSM for 1800 1 W is enough due to the smaller cell size .Apart from telephone interface ,MS can also offer other type of interfaces to users with display ,loudspeaker, microphone ,and programmable soft keys .Further interfaces comprise many more vendor specific functions and components ,such as cameras ,finger printsensors,calenders,address books ,games,internet browsers.Personal digital assistants (PDA) with mobile phone functions are also available .The reader should be aware that an MS could also be integrated into a car or be used for location tracking of a container.