Trạm di động và Subscriber Identity Module Các thiết lập điện thoại GSM và SIM là những yếu tố hệ thống duy nhất mà hầu hết người dùng của GSM có tiếp xúc trực tiếp. Các điện thoại GSM thiết lập và hình thành một hệ thống GSM gần như hoàn toàn trong chính họ với tất cả các chức năng, từ mã hoá đến HLR SIM. Hình cho thấy một sơ đồ khối của một trạm điện thoại di động với một khe cắm SIM | 2 The Mobile Station and the Subscriber Identity Module The GSM telephone set and the SIM are the only system elements with which most users of GSM have direct contact. The GSM telephone set and the SIM form an almost complete GSM system within themselves with all the functionality from ciphering to the HLR. Figure shows a block diagram of a mobile station with a SIM slot. Subscriber Identity Module The SIM is a microchip that is planted on either a check card ID-1 SIM or a plastic piece about 1 cm square plug-in SIM . Figure shows both variants. Except for emergency calls a GSM mobile phone cannot be used without the SIM. The GSM terminology distinguishes between a mobile station and mobile equipment. The mobile equipment becomes a mobile station when the SIM is inserted. There is no difference in functionality between the ID-1 SIM and the plug-in SIM except for size which is an advantage for the plug-in SIM when used in a small handheld telephone. Today many network operators offer at an additional cost identical pairs of ID-1 SIM plug-in SIM so the same SIM can be used in a car phone and in a handheld telephone. 13 S SbirdiyMdl Figure Block diagram of a GSM MS. 14 GSM Networks Protocols Terminology and Implementation The Mobile Station and the Subscriber Identity Module 15 GSM SIM ID-1 SIM Plug-in SIM Figure Plug-in SIM and ID-1 SIM. The SIM as a Database The major task of a SIM is to store data. That does not mean that the data is only subscriber data. One has to differentiate between data types for various tasks. The most important parameters that a SIM holds are presented in Table . It should be noted that the list is not complete and that the SIM can also be used to store for example telephone numbers. Advantage for the Subscriber The SIM is one of the most interesting features for a user of GSM because it permits separation of GSM telephone equipment and the related database. In other words the subscriber to a GSM system .
