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GSM Seminar

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					   PRESENTED BY:-
           NIRAJ TIWARY
          COMPUTER SCIENCE AND
           ENGINEERING IIIrd SEM
   FACULTY OF ENGINEERING AND
    TECHNOLOGY
   GURUKUL KANGRI UNIVERSITY
    HARIDWAR
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects (Signaling Protocols)
   GSM security
   Conclusion and comments
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects
   GSM security (Signaling Protocols)
   Conclusion and comments
 GSM is the world’s most popular 2G
 technology.

 GSM was the first cellular system to specify
 digital modulation and network level
 architectures and services,

 Accunts 70% of world’s digital mobile phones.

 Serving over 190 countries worldwide.
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects (Signaling Protocols)
   GSM security
   Conclusion and comments
   Support of international roaming
   Distinction between user and device
    identification
   Excellent speech quality
   Internetworking(with ISDN)
   Extensive security features
   Call waiting , call forwarding , SMS
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects (Signaling Protocols)
   GSM security
   Conclusion and comments
           SIM
                                               BSC            HLR         VLR

                             BTS
                                                                                            PSTN
                                                                      MSC
            ME

                                               BSC
                             BTS                                EIR         AC
           Air
           interface

          Mobile               Base Station                      Network
          Station              Subsystem                         Subsystem
   SIM- Subscriber Identity Module                  •   HLR- Home Location Register
   ME – Mobile Equipment                            •   VLR- Visitor Location Register
   BTS- Base Transceiver Station                    •   MSC- Mobile Switching Center
   BSC- Base Station Controller                     •   EIR- Equipment Identity Register
   PSTN – Public Switched Telephone Network
                                                     •   AC- Authentication Center
MSC                                                 MSC




A location area is a set of cells (BST, BSCs) served by a MSC
(in GSM, it is simply a set of contiguous cells defined in
order to simplify keeping track of MS)
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects (Signaling Protocols)
   GSM security
   Conclusion and comments
   The international Telecommunication Union
    (ITU),which manages international
    allocation
    of radio spectrum,has allocated the
    following
     bands:

GSM900:
Uplink:890-915 MHz (Mobile Station to base
 station)
   Since radio spectrum is a limited resource , it is to be shared by as
    many users as possible
   GSM uses FDD and a combination of TDMA and FHMA schemes to
    provide multiple access.
   The FHMA part involves the division by frequency of the the 25
    MHz allocated bandwidth into 124 carrier frequencies spaced 200
    KHz apart.
   One or more carrier frequencies are assigned to each base station.
   Each of these assigned carrier frequencies are then divided in time
    ,using TDMA scheme.
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects (Signaling Protocols)
   GSM security
   Conclusion and comments
                         CM
                         MM
                         RR
                         TL
These are the four protocol layers that we find in a number of
mobile systems:
•Transmission Layer (TL)
•Radio Resource Management Layer (RR)
•Mobility Management Layer (MM)
•Communication Management Layer(CM)
 Transmission: low level protocols. Roughly corresponding to
  first 3 layers of OSI.
 Radio Resource: most relevant to the MS/BSC interface. Looks
  after ‘basic handoff’ where MSC is not involved.
 Mobility Management:
  ◦ Location Update Procedure & handoff, esp. when
   MSC is involved
 ◦ Security functions
     ciphering
     identity protection - authentication
 Communication Management: Setting up and
  maintaining the call.
Functional Layers of Mobile Systems and OSI/ISO
Reference Model (rough corresp.)


Communication Management


 Exchag.
                  Conn.
                                 Discon-
                                           Application (7)
  Info            Estab   .      nection
                                           Presentation (6)
   Mobility Management
                                           Session (5)

    Location                               Transport (4)
                          Authentication
   Registration


 Radio Resource Management


           Inter-system Handoff
                                           Network (3)
       Transmission Layer
                                           Link (2)

                                           Physical (1)
    Roaming & Handoff

Cells are grouped in Location Areas.
A LA is served by a MSC.
We say that a MS is roaming when it is not in its LA

We have three types of handoff:
   The one where MS stays in the same LA and only
   BTSs are involved

   The one where MS stays in the same LA: only BSCs
   are involved

   The one where MS changes LA: MSCs become
   involved
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects (Signaling Protocols)
   GSM security
   Conclusion and comments
   Authentication of registered subscribers only
   Secure data transfer through the use of
    encryption
   Subscriber identity protection
   Mobile phones are inoperable without a SIM
   Duplicate SIMs are not allowed on network
   Securely stored Ki
   Goal
     Generation of SRES response to MSC’s random
     challenge RAND
                          RAND (128 bit)



           Ki (128 bit)        A3



                           SRES (32 bit)
   Goal
     Generation of ciphering key Kc
      ▪ A8 specification was never made public
                          RAND (128 bit)



           Ki (128 bit)         A8



                            KC (64 bit)
 A5 is a stream cipher
  ▪ Implemented very efficiently on hardware
  ▪ Design was never made public

 Variants
  ▪ A5/1 – the strong version
  ▪ A5/2 – the weak version
  ▪ A5/3
    ▪ GSM Association Security Group and 3GPP design
    ▪ Based on Kasumi algorithm used in 3G mobile systems
  Mobile Station            Radio Link                  GSM Operator

                           Challenge RAND
SIM
  Ki                                                                   Ki
              A3                                            A3
                        Signed response (SRES)
       SRES                                                     SRES

              A8             Authentication: are SRES       A8
                                  values equal?
       Fn          Kc                                      Kc     Fn

  mi                       Encrypted Data                          mi
              A5                                            A5
Mobile Stations   Base Station            Network     Subscriber and terminal
                   Subsystem             Management    equipment databases

                                            OMC
                  BTS
                                       Exchange
                                        System
                                                           VLR
                  BTS            BSC        MSC
                                                           HLR       AUC

                  BTS                                      EIR

      A5 Encryption
 Subscriber Identification Module (SIM)
   ▪ Smart Card – a single chip computer containing OS, File System,
     Applications
   ▪ Protected by PIN
   ▪ Owned by operator (i.e. trusted)
   ▪ SIM applications can be written with SIM Toolkit
   Introduction
   Features of GSM
   GSM Architecture
   Radio link aspects
   Network aspects (Signaling Protocols)
   GSM security
   Conclusion and comments
 GSM has shown commitment to openness ,
 standards and interoperability is the
 compatibility with the ISDN that is evolving in
 most industrialized countries.

 GSM is very complex standard, but that is
 probably the price that must be paid to
 achieve the level if integrated service and
 quality offered while subject to the fairly
 severe restriction imposed by the radio
 environment.
Q&A
Global System For Mobile
    Communication




                       Seminar By:-
                       NIRAJ TIWARY
                       BTECH II ND YEAR
                       CSE

				
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