GSM Architecture A

8/8/2019 GSM Architecture A

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October 30, 2010, Slide No 1

GSM... a Global Mobile Communication System

> GSM System Architecture> Mobile Billing System

> Operational Support Platform &> GrameenPhone Network


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> Network Elements> An example: Call setup

> Running a GSM network> Present and Future...

GSM System Architecture


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Network Elements an overview


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MS Mobile Station = phone + SIM

card

MSC

VLR

PSTN

Fixed networkBSC

SMSC

EIR

INTERNET

PABXPSTN

International

BSC

Telenor Nett

IN

PrePaid

Node

VMS

HLR

MSC

AUC


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Mobile Station (MS)

MS consists of the mobile equipment (the terminal) and a smartcard called the Subscriber Identity Module (SIM).

The SIM provides personal mobility, so that the user can haveaccess to subscribed services irrespective of a specific terminal. Byinserting the SIM card into a GSM terminal, the user is able to

receive and make calls at that terminal, and receive othersubscribed services. Without the SIM, the terminal will not work. The mobile equipment is uniquely identified by the International

Mobile Equipment Identity (IMEI). The SIM card contains the International Mobile Subscriber Identity

(IMSI) used to identify the subscriber to the system, a secret key

for authentication, and other information. The IMEI and the IMSI are independent, thereby allowing personalmobility.

The SIM card may be protected against unauthorized use by apassword or personal identity number (PIN).


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card

BTS Base Transceiver Station

MSC

VLR

PSTN

Fixed networkBSC

SMSC

EIR

INTERNET

PABXPSTN

International

BSC

Telenor Nett

IN

PrePaid

Node

VMS

HLR

MSC

AUC


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Base Transceiver Station (BTS)

The BTS corresponds to the transceivers and antennas used ineach cell of the network.

It handles the radio-link protocols with the Mobile Station.

A BTS may be placed in the center of a cell (omni-directional)or shooting in one or more specific directions (sectorized). Itstransmitting power defines the size of a cell.

Each BTS has typically between one and sixteen transceiversdepending on the density of users in the cell.

In a large urban area, there will potentially be a large numberof BTSs deployed, thus the requirements for a BTS areruggedness, reliability, portability, and minimum cost.


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Cell concept

Dominant coverage areaof one BTS sector

A sectorized BTS typicallyshoots in 3 antennadirections, thus covering3 sectors or cells

Because of limitedbandwidth, frequencychannels have to bereused

Identical andneighboring frequencies

need to be distributedaway from each other inorder to avoid noise interms of interference.


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card


BSC Base Station Controller

MSC

VLR

PSTN

Fixed networkBSC

SMSC

EIR

INTERNET

PABXPSTN

International

BSC

Telenor Nett

IN

PrePaid

Node

VMS

HLR

MSC

AUC


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Base Station Controller (BSC)

The BSC controls a group of BTSs andmanages their radio resources.

The physical area the BSC covers is dividedinto one or more Location Areas.

BSC handles radio-channel setup, handover,frequency hopping and the radio frequencypower levels of the BTSs.

The BSC is the connection between the mobilestation and the Mobile service Switching Center(MSC).

Before transmitting speech or data to the MSCthe information is transformed and coded in anTRANSCODER.


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Handover (HO)

BSCBSC

-Intra BSC Handover

- Inter BSC Handover (as illustrated)

- Inter MSC Handover


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card



HLR Home Location Register

MSC

VLR

PSTN

Fixed networkBSC

SMSC

EIR

INTERNET

PABXPSTN

International

BSC

Telenor Nett

IN

PrePaid

Node

VMS

HLR

MSC

AUC


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Home Location Register (HLR)

The HLR is a network database that contains all theadministrative information of each subscriber registered in theGSM network, along with the current location of the mobile.

Subscription data states the logical identity of each subscriber(MS) and which services that are accessible or barred for the

respective subscriber. The location of the mobile is typically in the form of the address

of the Visitor Location Register (VLR) associated with the mobilestation. This information is used to route calls and SMS to theMSC/VLR where the mobile station is currently located.

The HLR also contains a number of functions for managing these

data, controlling services and enabling subscribers to access andreceive their services when roaming within and outside theirhome GSM network.


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card




MSC Mobile services Switching

Centre

VLR Visitor Location RegisterMSC

VLR

PSTN

Fixed networkBSC

SMSC

EIR

INTERNET

PABXPSTN

International

BSC

Telenor Nett

IN

PrePaid

Node

VMS

HLR

MSC

AUC


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Mobile Switching Centre (MSC) /

Visitor Location Register (VLR) The MSC is a very central component of the GSM network. The MSC

performs the switching functions of the network and also providesconnection to other networks.

It additionally provides all the functionality needed to handle a mobile

subscriber, such as registration, authentication, location updating,handovers, and call routing to a roaming subscriber.

The VLR is always implemented together with a MSC; so the areaunder control of the MSC is also the area under control of the VLR.

The VLR contains selected information from a subscriber's HLR

necessary for call control and provisioning of the subscribed servicesto the visiting user.

Signaling between functional entities in the Network Subsystem usesSignaling System Number 7 (SS7).


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card




MSC Mobile services Switching

Centre

VLR Visitor Location Register

UC uthentication Centre

MSC

PSTN

Fixed networkBSC

SMSC

EIR

INTERNET

PABXPSTN

International

BSC

Telenor Nett

IN

PrePaid

Node

VMS

HLR

MSC

AUC


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Authentication Centre (AUC)

The AUC generates authentication and ciphering data.

The purpose of the authentication security feature is toprotect the network against unauthorized use. It also

protects subscribers by denying the possibility for intrudersto impersonate authorized users.

The ciphering data is used to ensure that confidentialityand integrity is kept on the physical radio channels.Ciphering prevents user information and signalling to be

available or disclosed to unauthorized individuals.


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MS Mobile Station = phone + SIM card BTS Base Transceiver Station BSC Base Station Controller

HLR Home Location Register MSC Mobile services Switching Centre VLR Visitor Location Register AUC Authentication Centre EIR Equipment Identity Register

For blacklisting stolen and unwanted

equipment

SMSC Short Message Service Support Centre VMS Voice Messaging System PrePaid Node Hosting GP Prepaid services IN Intelligent Network PSTN Public Switched Telephone Network PABX Private Automatic Branch Exchange

MSC

PSTN

Fixed networkBSC

SMSC

EIR

INTERNET

PABXPSTN

International

BSC

Telenor Nett

IN

PrePaid

Node

VMS

HLR

MSC

AUC

Documents

GSM Architecture A