Gsm Network Architecture PPT by anantarjanbhai

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									GSM Network Architecture
 BTS               BSC          EIR
       MS – Mobile Station


 SIM              ME
Mobile station provides user access to GSM
network for voice and data
All GSM mobiles comply to GSM standards
Subscriber data is read from a SIM card that
plugs into ME
            MS (cont..)
Each MS has a unique number called as
IMEI number, which is stored in EIR for
authentication purposes
Mobile camps on to the GSM network
through the BTS serving the cell
Mobile also scans neighboring cells and
reports signal strengths
Mobile transmits and receives voice at 13
kb/s over the air interface
      Mobile Station Output Power
CLASS 1               20 watts    Vehicle and Portable
CLASS 2               8 watts     Portable and Vehicle
CLASS 3               5 watts     Hand-Held
CLASS 4               2 watts     Hand-Held (GSM)
CLASS 5               0.8 watts   Hand-Held (DCS
Output power determines:
   Accessibility in areas of coverage
   Talk Time and Standby time
         Mobile Station Identities
MSISDN : Mobile Station ISDN Number
It is the human identity used to call a Mobile
    CC      NDC       SN        MSISDN
    98       250    00134
    CC – Country Code
    NDC – National Destination Code
    SN – Serial Number
     IMSI (International Mobile
       Subscriber Identity)
 3      2 or 3

MCC     MNC      MSIN        IMSI

Not more than 15

MCC – Mobile Country Code
MNC – Mobile Network Code
MSIN – Mobile Subscriber Identity Number
        IMEI (International Mobile
          Equipment Identity)

TAC        FAC      SNR        SP           IMEI
 6          2         6         1            15
     TAC – Type Approval Code
     FAC – Factory Assembly Code
     SNR – Serial Number
     SP – Spare digit (usually used to specify
          software version)
SIM ( Subscriber Identity Module)

Removable module inserted when the
subscriber wants to use the ME
Two sizes: credit card size and stamp size
SIM features and contents are
personalized by the Service Activator
ROM – 6kb to 16 kb
RAM – 128 bytes to 256 bytes
EEPROM – 3 kb to 64 kb
          Contents of SIM
Serial Number
IMSI, Subscriber Key Ki, Ciphering Key Kc
Algorithms for authentication and ciphering
Network Code
Charging Information
Abbreviated Dialling
Supplementary Features (e.g. Call barring)
           SIM Security
Two level protection
When mobile is turned on, it will ask for
user to enter PIN (Personal Id Number)
3 tries for PIN, after that PIN locked
To unblock PIN, there is PUK (Pin Unblock
10 attempts of PUK allowed
After that SIM is blocked
 BTS (Base Transceiver Station)
BTS has a set of Transceivers (TRXs) to
communicate with mobiles in its area
One BTS covers one or more than one cell
The capacity of a cell depends on number of
transceivers in the cell
BTS is connected to the BSC through Abis
Interface which is 2Mbps
BTS transmits and receives voice at 13kbps
over air interface to the mobiles.
BTS commands mobiles to set Tx. Power,
timing advance and Handovers
BSC – Base Station Controller
Several BTSs are connected to the BSC
BSC Manages channel allocation,
handovers and release of channels at
connected BTSs
BSC connects to the BTS via the Abis
interface and to the MSC on A interface
BSC has the entire database of cell
parameters associated with the BTSs.
No mobile data is stored in the BSC
Less connections for MSC as intelligence
is made common to all BTSs by the BSC
    TRAU – Transcoder Rate
       Adaptation Unit

                            MSC and TRAU

                      BSC               PSTN

13 kbps     16 kbps     16 kbps     64 kbps
         TRAU (cont..)
The MSC is based on ISDN switching.
The Fixed Network is also ISDN based.
ISDN has speech rate of 64 kbps.
Mobile communicates at 13 kbps.
TRAU converts the data rates between
13kbps GSM rate to 64kbps Standard
ISDN rate
TRAU can be collocated with the BTS,
BSC or MSC or it can be a separate
  Location of Transcoder

Collocated with MSC, BSC, BTS
Separate Unit

MSC                             BSC
MSC – Mobile Switching Centre



BTSs          PSTN
             MSC (cont..)
Exchange where calls are established,
maintained and released
Database for all subscribers and their
associated features.
Communicates with the BSCs on the A
interface and with PSTN on fixed line.
MSC is weighted on the number of subscribers
it can support. E.g. an MSC of 1 lac subscribers
means one MSC is enough till subscriber base
increases upto 1 lac, beyond which another
MSC is required.
            Multiple MSCs
 When there is more capacity, there are more
 than one MSCs.
 All MSCs have to communicate with one another
 and to the outside world.
 Very complicated to connect each MSC to each
 other and each MSC to PSTN
 So there is a concept of GMSC (Gateway MSC)

                       GMSC              PSTN
HLR – Home Location Register
 MSC has all subscriber database
 stored in HLR
 HLR has all permanent subscriber
 HLR has a database which describes
 the subscriber’s profile i.e. basic
 features and supplementary services
 MSC communicates with the HLR to
 get data for subscribers on call
VLR – Visiting Location Register
A subscription when activated is registered
in VLR
VLR has all the subscriber numbers which
are active.
VLR has a temporary database of all
active subscribers (on/off, location

           MSC              VLR
           VLR (cont..)


MSC       VLR           VLR       MSC

MSC communicates with HLR for
subscribers coming from different MSCs. If
the subscriber is found valid, then it
registers the subscriber in the VLR
 AUC – Authentication Centre
     Authentication is a process by which a
     SIM is verified
     Secret data and the verification process
     algorithm are stored in AUC
     AUC is the element which carries out the
     verification of the SIM
     AUC is associated with the HLR

MS           MSC           HLR            AUC
EIR (Equipment Identity Register)
EIR is the Mobile Equipment Database
which has a series of IMEIs
MSC asks the Mobile to send its IMEI
MSC then checks the validity of IMEI
with the EIR
All IMEIs are stored in EIR with
relevant classifications

         Classification of IMEIs
         White list: This contains the IMEI of
         type approved mobiles

Black List: List of IMEIs which should be
barred because either they are stolen or
are not functioning properly

         Grey list: List of IMEIs which are to be
         evaluated before they are put in black list
       Billing Centre (BC)
BC Generates the billing statement for
each subscriber
BC may be directly connected to the MSC
or through a mediation device
MSC sends CDRs (Call Detail Records) to
the BC
According to the template of pulse rates
and units set, BC creates a bill according
to the destination called and the call
Billing Centre (BC) (cont..)
                    Templates for unit costs

     OMC – Operations and
      Maintenance Centre

Also called the NOC (Network Operations
It is the central monitoring and remote
maintenance centre for all network
OMC has links to BSCs and MSCs


       BSC   OMC System


             OMC Terminals

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