Graw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Introduction to GSM Introduction to GSM Figure 1-10 The added components of a PSPDN GSM network. SMS-SC Network Equipment Identity Register (EIR) Authentication Center (AuC) SMS Serving Center (SMS SC) Gateway MSC (GMSC) Charge Back Center (CBC) Operations and Support Subsystem (OSS) Transcoder and Adaptation Unit (TRAU) Mobile Equipment or Mobile Station The mobile station (MS) consists of the physical equipment, such as the radio transceiver, display and digital signal processors, and a smart card called the Subscriber Identity Module (SIM). It provides the air interface to the user in GSM networks. As such, other services are also provided, which include Voice Teleservices Bearer services Features Supplementary services Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Introduction to GSM Chapter 1 Subscriber Identity Module The SIM provides personal mobility, SO that the user can have access to all subscribed services irrespective of both the location of the terminal and the use of a specific terminal. By inserting the SIM card into another GSM cel- lular phone, as shown in Figure 1-11, the user is able to receive calls at that phone, make calls from that phone, or receive other subscribed services. The International Mobile Equipment Identity (IMEI) uniquely identifies the mobile equipment. The SIM card contains the International Mobile Sub- scriber Identity (IMSI), identifying the subscriber, a secret key for authen- tication, and other user information. The IMEI and the IMSI are independent, thereby providing personal mobility. A password or personal identity number may protect the SIM card against unauthorized use. The Mobile Station Function Different types of terminals are available that are distinguished principally by their powe