2. Introduction
A cellular network is a radio network
distributed over land through cells where
each cell includes a fixed location
transceiver known as base station.
5. System Architecture
Mobile Station (MS)
The Mobile Station is made up of two entities:
1.Mobile Equipment (ME)
-Portable,hand held device .
-Uniquely identified by an IMEI (International Mobile Equipment Identity)
-Voice and data transmission
-Monitoring power and signal quality of surrounding cells for optimum handover.
2.Subscriber Identity Module (SIM)
1. SIM Card carries the user's identity for accessing the network and
receiving calls.
2. All calls are charged against SIM card account.
3. It is equipped with a memory to store telephone numbers along with
names.
4. It also enables to send and receive short messages ( SMS)..
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6. System Architecture
Base Station Subsystem (BSS)
Base Station Subsystem is composed of two parts
1. Base Transceiver Station (BTS)
- Amplifiers, Antennas that relay radio messages,
transceivers (TRX).
2. Base Station Controller (BSC)
- allocation of radio channels.
-controls handovers from BTS to BTS
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7. System Architecture
Network Switching Subsystem(NSS)
Mobile Switching Center (MSC)
Heart of the network
Manages communication between GSM and other networks
Call setup function and basic switching
Call routing
Billing information and collection
Mobility management
- Registration
- Location Updating
- Inter BSS and inter MSC call handoff
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8. System Architecture
Network Switching Subsystem
Home Location Registers (HLR)
- permanent database about mobile subscribers in a large service
area(generally one per GSM network operator)
- database contains IMSI, prepaid/postpaid,roaming
restrictions,supplementary services.
Visitor Location Registers (VLR)
- Temporary database which updates whenever new MS enters its
area, by HLR database
- Controls those mobiles roaming in its area
- Reduces number of queries to HLR
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9. o Equipment Identity Register (EIR)
-Equipment Identity Register is a database that
contains a list of all valid mobile equipment on the
network.
o Authentication Center (AuC)
-Each network SIM card is assigned an individual
authentication key for security to ensure that third
parties are unable to use network subscriber
services.