GSM/GPRS PROJECTS
Finland
Sonera, Elisa, DNA, Alcom
Greece
Cosmote, Vodafone, Wind, CYTA
Hungary
Telekom, Telenor, Vodafone
Norway
Telenor, Telia, Ice.net
Spain
Movistar, Vodafone, Orange, Yoigo
Portugal
MEO, Vodafone, NOS
Table 1.1 List of GSM operators in some European countries 1.2 GSM Network Architecture
The GSM network architecture is now a mature system and it consists of four main areas: • Mobile Station (MS) • Base-station Subsystem (BSS) • Network and Switching Subsystem (NSS) • Operation and Support Subsystem (OSS) Mobile Station (MS) Mobile station consists of the mobile phones and this is part of the network that users see and operate. The hardware consists of the mobile phone including an electronic processor, display, case, battery, and a Subscriber Identity Module (SIM) card. The SIM card stores various information such as the identity of the user on the network, phone book etc. Every mobile phone has a unique number known as the International Mobile Equipment Identity (IMEI) which is part of the phone and cannot be changed. Base Station Subsystem (BSS) The BSS is responsible for communicating with the mobile phones on the network. This unit consists of the Base Transceiver Station (BTS) and the Base Station Controller (BSC). BTS consists of the radio equipment used to communicate with the mobile phones. BSC is the interface between the BTS and the remainder of the GSM network. BSC controls a number of BTSs and it allocates channels and handles the handover mechanisms within the group of BTSs. Network Switching Subsystem (NSS) The NSS contains a number of modules such as the Mobile Services Switching Centre (MSC), Home Location Register (HLR), Visitor Location Register (VLR), Equipment Identity Register (EIR), Authentication Center (AC), Gateway Mobile Switching Center (GMSC), and the SMS Gateway (SMSG). The MSC performs tasks such as authentication, registration, call location, call routing to mobile phones and to landlines and so on. Links to other networks are also handled by the MSC. The HLR contains a database of all the details about each subscriber and there is only one HLR in a network. In addition to details, the last known locations of the subscribers are
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