SIEMENS
CF62 Level 2 Service Manual
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1.2 GSM Network Architecture
GSM network can be broadly divided into three broad parts, namely:
1. Mobile Station(MS) carried by the subscriber
2. Base Station Sub-system(BSS) which controls the radio link with the mobile station.
3. Mobile Switching Center(MSC) which performs the switching of calls between the
mobile users, and between mobile and fixed network users.
FIGURE 1.2 GSM ARCHITECTURE
Each mobile station is given a unique identity. As soon as the mobile phone is turned on,
it registers with the network and is authenticated, as such the network could always find
the mobile phone. Larger amount of data is being exchanged to and from the following
functional blocks in the MSC:
Visitor Location Register, VLR
Contain relevant data of all mobiles located in the serving MSC, but not belong to the
area.
Home Location Register, HLR
Stores identity and user data of all the mobile users belonging to the area.
Authentication Center, AUC
Provides the HLR with different sets of parameters to complete the authentication of the
mobile station.
Equipment Identity Register, EIR
An option the network operator can use to enforce security. With this feature the network
can identify defective or stolen mobile that may not be used in the network.
