Gsm mobile communication basic

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					                       Basics

        Objectives
   Understand   Concept of Cellular
   Understand   the functional blocks in a GSM Network
   Understand   the Air Interface with Channels
   Understand   Mobile Call Setup Operations
Agenda
     Need for Cellular
     Introduction to Cellular
     Channelization Concept
     GSM Evolution and Markets
     GSM Network Arhcitecure
     GSM Air Interface Parameters
     GSM Speech Coding
     Physical and Logical Channels
     Frames and MultiFrames
     GSM Basic Operations
            Telephony
 Communication is today's basic need
 Telephone has become part of life
 Fixed Line Telephones

What are the drawbacks ?
     Fixed Line Telephones
   No Mobility


   Delay in New Connections


   Security Hazards


   Prone to Failures ( Line Disconnection,
    etc )

   Very less value added services
Mobile Communications
   Drawbacks of Fixed Phones have
    triggered wireless communications

    "Call People , Not Places "
                               Wireless Access Methods


                                First Wireless Signal




Postcard: Chicago Daily News

                                 MCG Spokane Division   RTEd Sem, 1000-1268   3
                     H           9/93
                                 Company Confidential
      Wireless Communication Model




    Source
                                Receiver
                                               Display
                 Transmitter

                Media of transmission is Radio Frequency
H                                                Authoring Division Name File Name
                                                 Security Notice (if required)
        Types of Wireless Communications
    Simplex
     The direction of transmission is in one direction
     only




                   BEEP

     Ex : Broadcast Services ( AM/FM Radios, Television )
           Paging Services
H                                                           Authoring Division Name File Name
                                                            Security Notice (if required)
        Types of Wireless Communications
    Half - Duplex
The direction of transmission is alternate in both directions

           "A"                                     "B"

          Tx                                     Tx

          Rx                                     Rx

               A transmits -- B receives, then
               B transmits -- A receives


           Ex : PTT Handsets, Trunked Radios

H                                                 Authoring Division Name File Name
                                                  Security Notice (if required)
         Types of Wireless Communication
    Duplex
    The direction of transmission is simultaneous in both
    directions




      Ex : Cordless Telephones, Mobile Phones, Microwave
      Radios
      Is there separate frequency of transmission at both
      ends ?
H                                                     Authoring Division Name File Name
                                                      Security Notice (if required)
                                 The Electromagnetic Spectrum
                                 Wireless Communication !!! At what frequency ?
     AM BROADCAST RADIO




                                                                                                                                               VISIBLE
                                                                       VHF TV
                                                    VHF TV




                                                                                                                                               LIGHT
                                                                                       MICROWAVE
                                                                                       S




                          1MHz         10MHz            100MHz                  1GHz         10GHz    100    12
                                                                                                            10
                                                                                                                      14                              15
                                                                                                                  1                               1
                                                                                                      GHz         0                               0


                      MF                HF                   VHF                UHF             SHF         EHF

1000                             100           10                  1                   10c             1c                  1m                         1µ
m                                m             m                   m                   m               m                   m                          m
 H                                                                                                                Authoring Division Name File Name
                                                                                                                  Security Notice (if required)
    Selection of Band for Wireless
    Communication
Properties of Radio Frequencies
      Low Frequency - Less Loss ,,, High Frequency - More Loss
      To overcome loss , more power required,
      More Power - Health hazards
      Low Frequency - High Beamwidth - Wider and Deeper Coverage

             MF : 300 KHz - 3 MHz ( Domestic Radios )
             HF : 3 MHz - 30 MHz
             VHF : 30 MHz - 300 MHz ( FM, Paging, PTT )
             UHF : 300 MHz - 3 GHz ( Mobile Radios, Cordless Phones )
             SHF : 3 GHz - 30 GHz ( Microwave Band )


    Selection of Band will depend on Application
    Frequency Band is subdivided into Application Band
    Application Band is further divided into Technology Channels
H                                                             Authoring Division Name File Name
                                                              Security Notice (if required)
            Channelization
       Frequency Band has several application segments
       Certain blocks of the Band are reserved for certain applications by
        regulating authorities and as well by standard Technologies
       Technologies have decided on fixed bandwidth Channels within these bands

          Example : Mobile Communications
        AMPS / DAMPS : 824 MHz -- 894 MHz ( 50 MHz + 20 MHz
        separation)
        GSM : 890 MHz -- 960 MHz -- ( 50 MHz + 20 MHz separation)
        These 50 Mhz are bands are further divided into
        Channels
              Channelization can be done by three
              methods
                          --- FDMA
                          --- TDMA
                          --- CDMA
H                                                                Authoring Division Name File Name
                                                                 Security Notice (if required)
      Channelization Methods
    FDMA
           Power
                                 Time




                            FDMA          Frequency


Ex: AMPS / DAMPS band is divided into 30 Khz Channels ( 1666 Freq
Chs)
     GSM band is divided into 200 Khz Channels ( 250 Freq Chs ).
       Television Channels ( Star, Zee, Sony, MTV, BBC, CNN etc. )

H                                                     Authoring Division Name File Name
                                                      Security Notice (if required)
        Channelization Methods
    TDMA
              Power                  Time




                        FDMA/TDMA                         Frequency

         Each FDMA Channel is divided into Timeslots
         Each Timeslot is of fixed period

         This method increases the number of Channels in a

          system
    Ex: DAMPS has 3 timeslots on each 30 Khz Channel ( 4998
    Channels)
         GSM has 8 timeslots on each 200 Khz Channel ( 2000
H
    Channels )
                                                       Authoring Division Name File Name
                                                       Security Notice (if required)
           Channelization Methods
    CDMA
                               Time
                Power




                            CDMA       Frequency



       Frequency Channel is divided into Code Channels
       1.25 MHz of FDMA Channel is divided into 64 Code
        Channels

H                                                  Authoring Division Name File Name
                                                   Security Notice (if required)
      Mobile Telephony -- Channelization

     Mobile   Telephony needs Duplex Communication



    How many Channels will be required for one call ?


    What type of Channels ?
       -- FDMA, TDMA, FDMA/TDMA , FDMA/CDMA or something
    else




H                                              Authoring Division Name File Name
                                               Security Notice (if required)
    Duplex Access Methods

     Frequency Division Duplex
              (FDD)
     Amplitude

                 Time

                   Tx        Rx
                                          Time Division Duplex
            F1          F2   Frequency           (TDD)
                                         Amplitude

                                                     Time
                                                                        Rx
                                                                      Tx
                                                                 Rx
                                                            Tx          Frequency
                                                       F1


H                                                                       Authoring Division Name File Name
                                                                        Security Notice (if required)
Introduction to Cellular
Communications
Need for Cellular
         Cellular structure
Cellular network has cells of different
  sizes. Bigger cells are used where
subcriber density is low. Smaller cells
 are used where subscriber density is
                 high.
  Cell Configuration

Omnidirectional Cell   Sectorial Cell




               BTS
                                        BTS
    Frequency Reuse
                                                   F= 1,2,3,4,5,6,7,8,9,10
                                Clusters
   GSM uses concept of cells
   One cell covers small part of network                   F=2
   Network has many cells                          F=7               F=3
   Frequency used in one cell can be used
                                                             F=1
     in another cells
   This is known as Frequency Re-use              F=6,10            F=4,8
                                          F=2               F=5,9
                                  F=7                 F=3            F=2
                                             F=1            F=7               F=3

                                 F=6,10             F=4,8            F=1
Co-Channel ( Re-use ) Cells               F=5,9                              F=4,8
                                                            F=6,10
                                                                     F=5,9
Distance between two cells
  using same frequencies
D=R x SQRT( 3 x N )
N= Cluster size ( 7 in this case )
R=Radius of one cell
D=Dist between two cells using same channels




           DD       R              1,13,29
1,13,29          1,13,29
                 1,13,29
  Cell Splitting



                                               Micro
Macro Cell                                     Cells

             Macro Cell


                      Micro
                      Cells
                              Macro Cell
                                           Pico Cell
Mixed Cell Structure

                        Macrocell
                                                       Indoor
                       base station
                                                      Picocell
         Indoor
        Picocell




                                        Microcell
                                      base stations




                   Microcell network
                                                                 Macrocell network

                             Authoring Division Name File Name
H                            Security Notice (if required)
GSM TECHNOLOGY - Standards &
Implementation.




                GSM900
                DCS1800

                  Authoring Division Name File Name
  H               Security Notice (if required)
GLOBAL System for Mobiles

           239 licenses in 109 countries now

           44 million subscribers now

           One New subscriber Every Second !

           > 200 million subscribers by Year 2000




                               GSM900
H                  Authoring Division Name File Name
                   Security Notice (if required)
         Personal Communications
         Networks
                                                             UK: DCS1800
                                                             Mercury One-2-One
                                                             Microtel-Orange



                                                                       Hong Kong:
USA: PCS1900                                                           DCS1800
for new PCS                                                            for 6 New PCNs

   France:
   DCS1800                                                               Australia:
   For new PCN   Germany:   Thailand:
                                                                         DCS1800
                 DCS1800    DCS1800
                                                                         for new PCN
                 E Net      AIS
                                            DCS1800
                                            PCS1900
                             Authoring Division Name       File Name
        H                    Security Notice (if required)
         Evolution of GSM
GSM Requirements
   Good subjective speech quality
   Encryption of user information
   Must operate in the entire 890 - 960 Mhz frequency band
   Spectral efficiency
   Support for international roaming
   Minimize modifications to the existing fixed public networks
   Low handsets and service cost
   ISDN compatibility
   Support for range of new services and facilities




                                  Authoring Division Name File Name
         H                        Security Notice (if required)
                                                    The Global Standard
             •   Full Urban coverage in Western
                 Europe


             •   WW Roaming available

             •   Subscribers can utilize multiple
                 networks

             •   First dualband networks
                 appearing in Europe and Asia




• Full Urban coverage in Western
  Europe                        •                           Full Urban coverage in Western
                                                            Europe
• WW Roaming available
                                                        •   WW Roaming available
• Subscribers can utilize multiple
  networks                         •                        Subscribers can utilize multiple
                                                            networks
• First dualband networks
  appearing in Europe and Asia •                            First dualband networks
                                                            appearing in Europe and Asia


                                                               Authoring Division Name File Name
         H                                                     Security Notice (if required)
            Other GSM standards
    DCS 1800

   GSM 900 and DCS 1800 use the same standards
   DCS 1800 specs are defined as a delta standard to GSM specs
   Same GSM switches can be used for DCS 1800
   Some software upgrading may be required ( if RR are manged by switch )
   Dual Mode handsets will be required to support both




    PCS 1900
ETSI has assisted ANSI T1 and
TIA TR-46 committees to formulate
specs for PCS 1900.

                                       Authoring Division Name       File Name
           H                           Security Notice (if required)
                                                                                      •   Full Urban coverage in Western
           Evolution of GSM                                                           •
                                                                                          Europe

                                                                                          WW Roaming available
      The History                                                                     •   Subscribers can utilize multiple
                                                                                          networks

                                                                                      •
    1982 : Group Special Mobile formed within CEPT appearing in Europe and Asia
                                                                                          First dualband networks

   1986 : A permenent Nucleus formed
   1987 : Radio transmission Techniques are chosen.Field
      trials completed
   1987 : GSM becomes ETSI technical committee
   1987 : 13 Operators sign a memorandum of uderstanding
   1989 : Prototype ( validation ) systems are on the air
   1990 : GSM Phase I specifications are finalised
   1991 : UK,France,Germany andItaly introduce GSM services
   1992 : Motorola cuts over the first commercial system built
      for COMVIQ on Sept 1
   1994 : GSM Phase 2 specifications released
   1996 : GSM Phase 2+ specs are now defined
   GSM Phase I specification document has 5230 pages !!!

                                            Authoring Division Name       File Name
            H                               Security Notice (if required)
         •   Full Urban coverage in Western




                                                Growth
             Europe

         •   WW Roaming available

         •   Subscribers can utilize multiple
             networks

         •   First dualband networks
             appearing in Europe and Asia




•   Full Urban coverage in Western                               • Full Urban coverage in Western
    Europe                                                         Europe

                                                                 • WW Roaming available
•   WW Roaming available
                                                                 • Subscribers can utilize multiple
•   Subscribers can utilize multiple                               networks
    networks
                                                                 • First dualband networks
                                                                   appearing in Europe and Asia
•   First dualband networks
    appearing in Europe and Asia



                                                     Authoring Division Name       File Name
         H                                           Security Notice (if required)
       Technology Evolution
                                                 •   Full Urban coverage in Western
                                                     Europe

                                                 •   WW Roaming available

                                                 •   Subscribers can utilize multiple
                                                     networks

                                                 •   First dualband networks
                                                     appearing in Europe and Asia




•   Full Urban coverage in Western
    Europe

•   WW Roaming available

•   Subscribers can utilize multiple
    networks

•   First dualband networks
    appearing in Europe and Asia



                                   Authoring Division Name       File Name
        H                          Security Notice (if required)
        GSM 2G+
• HSCSD - High Speed Circuit Switched Data
  – Multiple TDMA timeslots allocated for data transmission
  – Bandwidth on demand, up to 64kBit/s
  – Compatible with existing GSM network infrastructure

• HSCSD - High Speed Circuit Switched Data
  – Multiple TDMA timeslots allocated for data transmission
  – Bandwidth on demand, up to 64kBit/s
  – Compatible with existing GSM network infrastructure

• HSCSD - High Speed Circuit Switched Data
   – Multiple TDMA timeslots allocated for data transmission
   – Bandwidth on demand, up to 64kBit/s
   – Compatible with existing GSM network infrastructure

                                          Authoring Division Name       File Name
         H                                Security Notice (if required)
    IMT-2000 / 3G+
    (International Mobile Telecommunications -2000)




•     HSCSD - High Speed Circuit Switched Data
                                                                                    erutcurtsarfni krowten MSG gnitsixe htiw elbitapmoC –
                                                                                                     s/tiBk46 ot pu ,dnamed no htdiwdnaB –
        –   Multiple TDMA timeslots allocated for data transmission
                                                                                  noissimsnart atad rof detacolla stolsemit AMDT elpitluM –
        –   Bandwidth on demand, up to 64kBit/s                               ataD dehctiwS tiucriC deepS hgiH - DSCSH •
        –   Compatible with existing GSM network infrastructure




             H                                                        Authoring Division Name   File
                                                                      Name
    GSM Standards structure

 01 Series : General
 02 Series :   Service aspects
 03 Series :   Network aspects
 04 Series :   MS-BS interface and
  protocols ( air interface layer 2 & 3)
 05 Series : Physical layer on the

  Radio path ( air interface layer 1)
 06 Series : Speech coding specs.




                    Authoring Division Name File Name
     H              Security Notice (if required)
    GSM STANDARDS - Continued

07 Series : Terminal adaptation for
mobile stations
08 Series : BSS - MSC interfaces ( A
& Abis)
09 Series : Network interworking
10 Series : Empty - For future use
11 Series : Equipment and Type
approval specifications
12 Series : Operation & Maintenance
                   Authoring Division Name File Name
    H              Security Notice (if required)
      GSM Network Architecture
                              BSC
                                    OML
                                            OMC

                                                          VMSC
             BTS                    A
                                                         AUC
                        BTS               MSC     HLR
BTS                           TRAU
                                                         EIR
                  BTS                             VLR

      BTS               BTS                                SMSC
            BTS
                   MS
                                                    BC
BTS                            BSC


                                            PSTN
     MS - Mobile Station
        Mobile station provides user access to GSM network for Voice & Data.
        All GSM mobiles comply to the GSM standards.
        Subscriber data is read from a SIM card that plugs into MS.
        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 a BTS serving the cell.
        Mobile also scans neighbouring cells and reports signal strength.
        Network knows whereabouts of mobiles from HLR & VLR databases.
        Mobile Transmit and Receive voice at 13 KB/s over air interface.




MS                                                          VLR

                                                                               EIR
                         BTS
                                                                               AUC
                          BTS
MS
                                   BTS                                          HLR
                        SIM
     MS - Mobile Station
    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
         CLASS 5      0.8 watts    Hand-held

       Output Power determines:
                 ---- Accessibility in areas of
            coverage
                 ---- Talk time and Standby Time
 Output Power on call is varied as commanded by BTS
H                                                         GSM Course
      Mobile Station Identities

     MSISDN : Human Identity used to call a Mobile
     Station
                CC NDC      SN

                 98 XXX          12345



    IMEI: Serial number unique to every Mobile
    Station      TAC    FAC    SNR     SP
               6 digits   2 digits   6 digits   1digit




H                                                        GSM Course
            SIM - Subscriber Identity Module

 Removable Module inserted when the subscriber wants to use the
    MS
    Two Sizes
   Credit Card                                         4-8 digits PIN code
   Stamp Size                                          3 false entries - blocks
                                     GSM                8 digit PUK
                                                        10 false entries -
                                                         disabled
                                                               MS
IMSI : Network Identity unique to a
SIM
  3     2       10
        MCC
        digits   MNC
                 digits    MSIN
                          digits
                                   ROM      = 6kb to 16kb
        404       XX      12345    RAM      = 128 byte to 256
                                   byte
                                   EEPROM   =   3 kb to 8 kb
    H                                                                GSM Course
       SIM - Subscriber Identity Module

Contents of
SIM          Serial Number
                   IMSI, Subscriber Key ( Ki )
                   Algorithms for Authentication, Ciphering
                   Network Code
                   PIN, PUK
                   Charging Information
                   Abbreviated Dialling
                   Supplementary Features ( e.g. call barring
                    )

     SIM features and contents are personalized by the Service
      Activator
     MS also stores some temporary data on SIM during operation


H                                                            GSM Course
     Base Station Cell Site
     Architecture
                             BTS
                             Cabin/Shelter/Room
GSM Antenna          AirCo
System               n




                                                  Mains
                                                  Powe
                                                  r
                                                  Panel


                     BTS       DC
    DM                        Power
    R                         Suppl
                              y         Batter
                              Unit      y
              Abis                      Backu
                                        p
H                                                  GSM Course
        BTS - Base Transceiver
         Station
   BTS has a set of Transceivers to communicate with mobile's in its area
   One BTS covers one or more than one cell
   The capacity of a cell depends upon number of tranceivers in a cell.
   BTS is connected to the BSC through Abis Interface, which is a 2Mb/s
   BTS transmit and receive voice at 13 kbps over air interface to the
    mobiles.
   BTS commands mobiles to set Tx. power, timing advance and Handovers




                                 BTS



       MS

                                                  BSC             MSC
                      RF
               CELL   Channels         Abis - 2
H                                      MBits/s                   GSM Course
    BTS Architecture 1
                                Rx A        Tx       Rx B




                                                                       BSC


            BPF         RFU

                    Splitte     T                                 PCM
           COM                         Fr
                                                 T              Interface
      A1            r A2        R      R         S    P     P
                                       e
       B1                       A      f         B
                                                                  Alarm
                         B2     U                               Interface
      TRX         TRX
       1           2                Processor
                              BTS   Modules

H                                                                    GSM Course
         BTS Architecture 2

                    BTS Cabinet. 3 Channel. Single
                    Sector
   NEM
Proprietary
 Interfac                                     TRX Unit
                              Backplane
 e
                                              TRX Logic
                                                                Combiner / Distribution
   BTS                                                                                                          Antenn
         Interfac                                               Unit
  Alarms e              CPU               I     Q I       Q                                                     a
                                               TRX RF




                                                                Splitte
  ABIS
over                                                                        LNA   Rx Filter
G703                                               RF




                                                                r




                                                                                                 Duplexe
                                               Power
          Frequency                           Amplifier
                                                                            Combiner




                                                                                                 r
          Reference
                                                                                       Coupler
                 Unit                                             Coupler



                                                PSU & Climate
                                                Control




H                                                                                                          GSM Course
             BSC - Base Station Controller

       Several BTS's are connected to one BSC
       BSC manages channel allocation,handovers and release of channels at connected
        BTS's
       BSC connects to each BTS on an Abis interface & to the MSC on A interface
       BSC has the entire database for all cell parameters associated with the BTS's.

                                              Abis
                                                                     A


                                                                           MSC




    H                                                                         GSM Course
        Base Station
        Controller
                                   BTS


                                         MSC


    P    P    P   T                T
                       T
    C   C     C   R        P   P   M
                  A    S
    M   M     M        B           G
                  U

                      Processor
        BSC           Modules



H                                        GSM Course
    Abis Interface


                                        E1 / T1




       Abis is a G.703 interface. It could be E1 or T1
       Abis carrries Traffic information of all the mobiles in the cells controlled by
        the BTS.
       Abis also carriers signalling information between BTS and BSC
       Signaling over Abis is done by LAPD protocols
       LAPD has several modes of implementation
             --- LAPD
             --- LAPD Concentrated
             --- LAPD Multiplexed




H                                                                          GSM Course
    Abis Interface
LAPD Modes
       LAPD
       Signaling for each TRX is on a dedicated 64 Kbps circuit

       Maximum Signalling for 10 Transceivers on 1 E1 link




                         64 kbps   0    Sync
                         64 kbps   1    TRX Signaling
                         64 kbps   2    4 Traffic Channels
                         64 kbps   3    4 Traffic Channels
                                                             } 1 TRX
                         64 kbps   4    TRX Signaling
                         64 kbps   5    4 Traffic Channels
                         64 kbps   6    4 Traffic Channels
                                                             } 1 TRX
                         64 kbps   7    TRX Signaling
                         64 kbps   8    4 Traffic Channels
                         64 kbps   9    4 Traffic Channels   } 1 TRX
H                                                                      GSM Course
    Abis Interface
LAPD Modes
      LAPD Concentrated mode 1
      Signaling for 4 TRX's is on a dedicated 64 Kbps ciruit

      Maximum Signalling for 13 Transceivers on 1 E1 link




                        64 kbps   0    Sync
                        64 kbps   1    4 x TRX Signaling
                        64 kbps   2    4 Traffic Channels
                        64 kbps   3    4 Traffic Channels
                                                            } 1 TRX
                        64 kbps   4    4 Traffic Channels
                        64 kbps   5    4 Traffic Channels
                                                            } 1 TRX
                        64 kbps   6    4 Traffic Channels
                        64 kbps   7    4 Traffic Channels
                                                            } 1 TRX
                        64 kbps   8    4 Traffic Channels
                        64 kbps   9    4 Traffic Channels   } 1 TRX
                     64 kbps      10   4 x TRX Signaling
H                                                                     GSM Course
    Abis Interface
LAPD Modes
      LAPD Concentrated mode 2
      Signaling for All TRX's is on a dedicated 64 Kbps ciruit

      Maximum Signalling for 15 Transceivers on 1 E1 link




                         64 kbps   0    Sync
                         64 kbps   1    ALL TRX Signaling
                         64 kbps   2    4 Traffic Channels
                         64 kbps   3    4 Traffic Channels
                                                             } 1 TRX
                         64 kbps   4    4 Traffic Channels
                         64 kbps   5    4 Traffic Channels
                                                             } 1 TRX
                         64 kbps   6    4 Traffic Channels
                         64 kbps   7    4 Traffic Channels
                                                             } 1 TRX
                         64 kbps   8    4 Traffic Channels
                         64 kbps   9    4 Traffic Channels   } 1 TRX
                      64 kbps      10   4 Traffic Channels
H                                                                      GSM Course
    Abis Interface
LAPD Modes
      LAPD Multiplexed
      Signaling for each TRX is on 16kbps subchannel.

      Maximum signalling for 15 TRX's on




                        64 kbps   0    Sync
                        64 kbps   1    TRX Signaling/ 3 Traffic Channels
                        64 kbps   2    4 Traffic Channels
                                                                           } 1 TRX
                        64 kbps   3    TRX Signaling/ 3 Traffic Channels
                        64 kbps   4    4 Traffic Channels
                                                                           } 1 TRX
                        64 kbps   5    TRX Signaling/ 3 Traffic Channels
                        64 kbps   6    4 Traffic Channels
                                                                           } 1 TRX
                        64 kbps   7    TRX Signaling/ 3 Traffic Channels
                        64 kbps   8    4 Traffic Channels
                                                                           } 1 TRX
                        64 kbps   9    TRX Signaling/ 3 Traffic Channels
                     64 kbps      10   4 Traffic Channels
                                                                           } 1 TRX
H                                                                          GSM Course
TRAU - Transcoder / Rate Adaptation Unit

   The MSC is based on ISDN switching. The Fixed Network is also ISDN based
   ISDN has speech rate of 64kbps. Mobile communicates at 13 Kbps
   TRAU converts the data rates between 13 KB/s GSM rate to 64 Kbits /s Standard
    ISDN rate
   TRAU can be colocated with the BTS,BSC or MSC or it can be a separate unit.




MS
                                                                                               P
                                                                                               S
                                                                A            MSC
                                            Abis
                                                                interface                      T
                        RF Channels         interface
                                                         BSC     2 MBits/s                     N
MS                                    BTS    2 MBits/s                       TRAU



          VOICE      13 KBits/sec      16 KBits/sec            16 KBits/sec         64 KBits/sec
    LOCATION OF TRANSCODER

          Colocated with MSC,BSC,BTS
          Separate Unit




          64
          kbps              16
    MSC          Transcoder
                            kbps   BSC




H                                        GSM Course
          MSC - Mobile Switching Centre
        Exchange where calls are established,maintained and released.
        Database for all subcribers and their associated features.
        Communicates with BSC's on MS side and with PSTN on fixed line
         side.
        MSC is weighted on the number of subcribers it can support
                                          MSC
                                                                    HLR
        BTS's


                                                                    VLR




                   BSC's

H                                                                GSM Course
      MSC - Mobile Switching Centre
    Multiple MSC's

                      MSC

           BSC's
                                  GMSC



            BSC's


                      MSC

More subscribers ? More MSC's
!
H                                        GSM Course
        HLR - Home Location Register

 MSC has all subscriber database stored in HLR
 HLR has all permanent subscriber database
 MSC communicates with HLR to get data for subscribers on
    call
                                                     HLR




   HLR will have the series of all subscriber numbers, which may not be activated or
    issued .




H                                                                         GSM Course
         VLR - Visiting Location Register

 A subscribtion when activated is registered in VLR
 VLR has all the subscriber no's which are activated
 VLR also has temporary database of all activated subscribers ( on/off,
     location )
                                             HLR


                                                     VLR



     MSC communicates with HLR for susbcribers coming from different
      MSC's
      and if found valid, then registers them in its VLR




H                                                               GSM Course
          AUC - Authentication Centre

       Authentification is a process by which a SIM is verified
       Secret data and the verification process alogorithm are stored at
        AUC
       AUC is the element which carries out the verification of SIM
       AUC is associated with the HLR




                          MSC                       HLR              AUC
MS




H                                                                    GSM Course
      EIR : Equipment Identity Register

 EIR is the Mobile Equipment Database which has a series of
  IMEI's
 MSC asks the Mobile to send its IMEI
 MSC then checks the validity of IMEI with the EIR
 All IMEI are stored in EIR with relevant classfications
        Classifications of IMEI( Mobile Stations
        )
White List                       Grey List

                               Black List
                                                            EIR


                    MSC
H                                                                 GSM Course
    BC - Billing Centre

       BC Generates the Billing Statement for each Subscriber
       BC may be directly connected to the MSC
       MSC sents the billing information ( duration of call ) to BC
       BC then produces the billing amount based on the units
        set




                                                       BC




H                                                                      GSM Course
          OMC - Operations & Maintenance
           Centre

   It is central monitoring and remote maintenance centre for all network
    elements
   OMC has links to BSC's and MSC
                   BSC's

                                                                             MSC
        BTS'
        s

                                      OMC
        BTS'                          System
        s

        BTS'
        s
                           asasasaaaaa         asasasaaaaa    asasasaaaaa
                           aqwtttsssdfa        aqwtttsssdfa   aqwtttsssdfa
                           a                   a              a
                           qwrqrncncea         qwrqrncncea    qwrqrncncea
                           s                   s              s




    H
                                          OMC Terminals
                                                                             GSM Course
      OMC - Operations & Maintenance Centre


              BSC's

                                                  MSC
    BTS'
    s


    BTS'
    s

                      OMC
                      System                  s
                                              qwrqrncncea
                                              a
                         s                    aqwtttsssdfa
                                              asasasaaaaa


           OMC -
                         qwrqrncncea
                         a
                         aqwtttsssdfa


                                          OMC -
                         asasasaaaaa


           R
H
                                          S         GSM Course
                OMC - RADIO
    BTS         BTS         BTS         BTS


          BSC                     BSC

                  TRANSCODER


                      MSC
                MUX / DEMUX
                X.25 SWITCH
                  SERVER                      OMC -
                                              R



H                                                     GSM Course
              OMC - Functions

                                                OMC Functions


                  Alarm Monitoring                        Configuration Changes       Performance Analysis


Environmental Alarms        Equipment Failure Alarms          Add new hardware          Cell Traffic Analysis
Power , Fire, Security,      BTS, BSC site Failures       Modify control parameters     No of calls, o/g ,i/c
     Aircons, etc.         MSC and pheripheral failures    other software changes.     PSTN, Call drops etc.



   H                                                                                                    GSM Course
              Equipment Alarms


    BTS , BSC , Transcoder Failures

    Link Failures

    Module Failures ( Transceiver,Processors)

                                  Transceiver 1
                                  Fail
    17:35hrs Site A
     Transceiver 1 Fail                       BTS
                           Network
                                                A



H                                                 GSM Course
            Cell Traffic


    TCH TRAFFIC IN ERLANGS FROM 09:00 to 21:00hrs

    8
    7
    6
    5
    4
    3                                               1

    2
    1
    0
        A1 A2 A3 B1 B2 B3 C1 C2 C3 D1 D2 D3
                     cell names




H                                                       GSM Course
      SMSC - Short Message Service Centre


 Message is sent to a particular mobile.
 Message transfer takes place through SMSC
 Messages are be sent through a Manual Terminal connected to
    SMSC


                     MSC


                                             SMSC




H                                                          GSM Course
        VMSC : Voice Mail Service
         centre
     It has a database for all Voice Mail Subscribers
     It also stores all the Voice Mail - Voice
     Messages


                                  MSC
                                                         VMSC




H                                                         GSM Course
       GSM Signaling Interfaces

A,B,C,D,E,F,G,H,I = SS7
Abis = LAPD                                                                     VLR
OML = X.25                                                            G
                                       MSC                                  D            HLR/
                 BSC                                B           VLR
                                                                                         AUC
                                                                          HLR/AUC
                                                                      C
       Abis                  A
                                                        F
BTS
                                                                EIR
                                                    I
                                 OML         E
                       OMC
                                                            SUPP

                                                            H
                                  SS7/R2
                          PSTN                   GMSC            GSMSC



 H                                                                                  GSM Course
   A GSM Cell
BCH
Broadcast
CHannel




                      BTS
                            Abis
                            Interface
            TCH
            Traffic              To BSC
            CHannel
    GSM Air Interface
 Separate Bands for Uplink and Downlink
  Down link : 935 - 960 MHz ( E-GSM 925 - 960
  MHz )                            Uplink     :
  890 - 915 MHz ( E-GSM 880 - 915 MHz)
 TDMA and FDMA Multiplex

   – 124 Frequency Channels (ARFCN) for
     GSM900
   – 1 to 124 for current band
   – 975 to 1023 for E-GSM
   – 200kHz Channels
   – 8 Mobiles share ARFCN by TDMA


   0.3 GMSK Modulation
     – 270.833 kbits/sec. rate
     TDMA and FDMA
Physical Channel is an        Time
ARFCN and Timeslot                                        7
                                                      6

                                                  5

Amplitude                                     4

                                          3   Timeslot
                                      2
                                  1

                              0
                          7
                                      Frequency
 1   2   3    4   5   6
             ARFCN
The GSM Burst
                     Time




  Amplitude




         Frequency
Speech
Coding          PCM Coding - 64 KB/s

                      PSTN




                     Air Interface



         RPE-LTP Coding in GSM - 13 KB/s
    Speech Coder -                  Defined under GSM TS 6.10


                                         RPE and LTP Coder ( Regular
                 20 ms Blocks
                                     

                                         Pulse Excited - Long Term
                                         Prediction )

                                        RPE-LTP is a combination of
                   Speech Coder          RELP and MPE-LTP codecs.
                      260 Bits          Coverts Speech to Low Data Rate

                    Bits Ordered        20ms Speech makes 260 Bits

                      260 Bits          Output 13 kbit/s




       50           13              7
Very Important   Important         Other
Bits                2
                 Bits               8
                                   Bits
   Error Correction

        Type Ia
                50           Type Ib
                                          132       Type II
                                                                78              262 Bits in
          Block Code
        Type Ia        CRC         Type Ib                  Type II
            50         3            132                         78

                  Re-ordering
Type Ia    Type Ib    CRC Type Ib         Type Ia     Tail            Type II
   25        66        3      66             25         4             78


        Half rate convolutional code
                                                                      Type II          456 Bits O
                       378                                              78

                           456     Bits from 20ms of Speech
       Diagonal Interleaving
456         Bits from 20ms of Speech
                                                    456      Bits from 20ms of Speech


57     57   57   57    57     57    57     57      57   57   57   57   57   57   57   57      57




                      57 57        57 57        57 57   57 57     57 57     57 57     57 57

            TCH
     Traffic Channel (TCH) Bursts Carry Two 57 Bit Blocks (114) Each
     120ms of Speech = 456x6 = 2736 bits
     2736 / 114 = 24 bursts i.e. 24 frames (mobile Tx once per frame)
     Multiframe has 26 frames in 120ms
     There are 2 spare frames ......One SACCH, One Idle
    Convolutional Coding & Interleaving
                         Example:




                                             ..
                                             Hello... Encode
Bits to be              HELLO FOLKS




                                                    al
                                                           Convolution
Txed:




                                                       r
Convolutionally
Encoded           HHEELLLLOO FFOOLLKKSS




                                                 er
                                                 Interleav
:
Interleaved
:
                  ELSOLHLOFK LEOLSHOLKF

Bits
Rxed:             EL SOL HLOFK LEOLSHOLKF




                                             er
                                             Interleav
                                                -
                                                De
De-
Interleaved:      HHEELLL -OO FFO -LLKK -S
Viterbi
Decoded:                HELLO FOLKS
                    Speech coding Process


                                                           22.8 Kbps
        20ms                                        456
                                                    bits
     Speech Coder
                                            Tranceiver ( BTS
       260 bits   13 kbps                   )                 13 kbp
                                                     260 bits

50        132        78                     Transcoder Handler
1a         1b        11
                                                             16 kbps
                                            260 + 60 = 320
      Channel                               bits
      Coder
                                              TRAU Frame
       456        22.8
       bits       Kbps                           Abis
                  TRAU Frame
                               Abis
  T0       T1       T2        T3                      T30    T31

Synch     Sign             T T T T



                              T = 16 Kbps


260 bits info + 60 TRAU bits = 320 bits/ 20ms = TRAU Frame
60 bits contains Frame Information data which indicates
speech,data,idle,O & M , full-rate/half-rate.


   60 bits = 35 synchronization + 21control + 4 timing
      Midamble or Training Bits

                        57             26           57     3 8.25
  Timeslot        3
                        bits
                                1
                                       bits
                                                1
                                                    bits     bits
(normal burst)   Tail        Control          Control    Tail
                 bits   Data  bit               bit Data bit    Guard
                                                                Period
                          Midamble
    8 Midamble Patterns (Colour Codes) of 26 bits
    RACH and SCH have Longer 41 and 64 bit
     Midambles
    Equalizer Estimates Channel Impulse Response
     From Midamble
    Mathematically Construct Inverse Filter
    Uses Inverse to Decode Data Bits
         GSM TDMA Power Burst
 Power                   +4 dB
                                            +1.0 dB
                                            -1.0 dB                           -6 dB
           -6 dB




    -30 dB                                                                            -30 dB
                                   147 "Useful" Bits
                                       542.8ms
-70 dB                                                                                    -70 dB
         10ms 8ms 10ms                                                   10ms 8ms 10ms
                         3   57       1      26       1         57   3


                                  148 "Active" Bits, 546.42ms
                                                                                Time
       0.3 GMSK Modulation

Data                    270.833kB/s


                        +67.708 kHz

Frequency
                        -67.708 kHz   Q

                                          I
Phase          +90deg   -90deg
      Downlink and Uplink
                              Downlink
            0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1


       45 MHz
                                    Uplink                     2
                                                               5
                 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1




   Uplink Lags Downlink by 3 Timeslot periods
   Uplink and Downlink use same Timeslot Number
   Uplink and Downlink use same Channel Number (ARFCN)
   Uplink and Downlink use different bands (45MHz apart for
    GSM900)
    Measurements by MS and BTS




                                                                RXQUAL
   RXLEV is the received power level                       0
   RXQUAL is the received quality.                         1       < 0.2 %
          It is the bit errorr measured on the M idamble   2     0.2 - 0.4 %
                                                            3     0.4 - 0.8 %
                                                            4     0.8 - 1.6 %
                                                            5     1.6 - 3.2 %
                                                            6     3.2 - 6.4 %
                                                            7    6.4 - 12.8 %
    Measuring Adjacent Cell BCH Power
DOWNLINK




UPLINK




DJACENT CELL
   BCH         RXLEV   RXLEV   RXLEV   RXLEV   RXLEV
Mobile Power Control

   Mobile is commanded to change its Transmit Power
   Change in Power is proportionate to the Path Loss
   Change is Power is done in steps of 2 dbs




                                          Tx Level      Power dBm
                                              5            33
                                              6            31
                                              7            29
                                              .             .
                                             14            15
                                             15            13
Timing Advance


    TDMA approach requires signals to arrive at BTS at
    the correct time. They must not overlap.




                                 BTS
       Concept of Channels in
    Concept of Channels in GSM GSM
A company vehicle is used for several purposes in a day..

   1.   To pick up employees in the morning
   2.   To receive company guests from airport
   3.   To carry material to the site / stores
   4.   To Collect mail/courier
   5.    To drop the employees back home
   6.    To get a doctor in case of emergency
   7.    To carry company gusts for a dinner


If there were two vehicles, we can allocate a set of tasks
 to one , and rest to the other. However, since both are
identicle vehicles, there is greater flexibility in usage.
Time Sharing by Channels



                                                    7

                                                6
                                            5

                                        4
                                    3

                                2

                            1
                        0
 0   1   2   3   4
                     FRAME NUMBER
     Concept of Frames
Time slot Number..
  0   1     2   3          4           5       6       7
 C    T    T       T       T           T       T       T                       Frame No. 1


               0       1       2       3       4           5       6       7
           C       T       T       T           T       T           T   T                        Frame No. 2



                               0       1       2       3           4       5        6   7
                           C       T       T       T           T       T        T       T             Frame No. 3



                                       C       T       T           T       T        T       T     T      Frame No. 4
       CHANNEL ALLOCATIONS IN A CELL

                              FRAME Number


0       C                         C                                     C               C    C
              C     C     C             C             C        C              C
1
        U1    U1    U1   U1                                             U8    U8    U8       U8
2                                                          U2       U2       U2     U2      U2
3
                                 U3     U3       U3        U3      U3        U3    U3
4
              U4   U4    U4     U4     U4        U4       U4       U4
5
                          U5      U5        U5    U5       U5       U5       U5    U5       U5
6
        U6   U6    U6    U6      U6     U6       U6        U6
7

                                                  U7       U7       U7        U7    U7
     Frames and Multiframes

 Control Channel Multiframe                              Traffic Channel Multiframe

 0                                 50                         0                  26




                                        4.615ms
Frame                    0                                          7
                               1                         5    6
                                   2     3       4                       8 Timeslots
                                        576.92 us
Timeslot          3
                                          26
                                                     1 3 8.25
                        Data        1                        Data        156.25 Bits
                                          bits            bits
normal burst)    Tail           Control   Control     Tail
                 bits            bit         bit      bit Guard
                        57 bits      Midamble 57 bits         Period
   Channels in GSM Air Interface
                                            PHYSICAL CHANNELS
                                            ARFCNs - 1 to 124 ( D & U )
                                    5       Timeslots - 0 to 7 ( D & U )
                                4
                            3               Total of 124 x 8 = 992 Channels
                        2
                    1
                0
12 3 4 56

                                                   LOGICAL CHANNELS
                                                   ARFCN - X , Timeslot - Y
                                                   Frame Number - N



                     CONTROL CHANNELS                                          TRAFFIC CHANNELS


  BCH -                             CCCH -                DCCH -
                                    COMMON                                         TCH -
  BROADCAST                                               DEDICATED
                                    CONTROL                                        TRAFFIC
  CHANNELS                                                CONTROL
                                    CHANNELS                                       CHANNEL
                                                          CHANNELS


   FCCH -                                                   SDCCH -
                                    PCH -
   Frequency
     SCH -                                                  Standalone              TCH - F
                                    PAGING
   Correction
     Synchronisation                  AGCH -
                                    CHANNEL
                                                               SACCH
                                                            Dedicated -             FULL RATE
   Channel
     Channel                          ACCESS                   Slow
                                                            Control                 TRAFFIC
                                         RACH -                                        TCH - H
         BCCH -                       GRANT
                                                                  FACCH
                                                               Associated -
                                                            Channnel                CHANNEL
                                         RANDOM                   FAST                 HALF RATE
         Broadcast                    CHANNEL                  Control
                                         ACCESS                   ASSOCIATED           TRAFFIC
         Control Channel                                       Channnel
                                         CHANNEL                  CONTROL              CHANNEL
    BCH - Broadcast CHannel
   One ARFCN, On all the time, in every cell
   Uses Timeslot 0 on a channel, in Downlink.
   Allows Mobiles to tune to BTS freq. - FCCH
    This channel carries a 142 bit zero sequence
    and repeats once in every 10 frames on BCH       BCH
   Allows Mobile to Synchronise - SCH
    This channel carries the Frame number and
    BSIC in encrypted data format. Amidamble of
    64 bits helps mobiles to synchronize. SCH also
    repeats once every 10 Frames.
   Allows Mobiles to identify Network - BCCH
    Used to broadcastl Cell and Network identity.
    BCCH occupies 4 frames on BCH. and repeats
    once every Multiframe.
   BCH Sub channels
        3                  142 bits - all 0's                3 8.25
FCCH   Start                                                Stop Guard
       Bits                                                 Bits Bits



                 39                  64          39           3 8.25       BCH
SCH     3                                       Encrypted   Stop Guard
       Start   Encrypted         Training
                                 Sequence       Data Bits   Bits Bits
       Bits    Data Bits


        3                                                     3    8.25
       Start                                    57          Stop   Guard
                      57             26
       Bits                                                 Bits   Bits
        3                                                     3    8.25
BCCH   Start          57             26          57         Stop   Guard
       Bits                                                 Bits   Bits

         3                                                    3    8.25
       Start          57             26          57         Stop   Guard
       Bits                                                 Bits   Bits

        3                                                     3    8.25
       Start          57             26          57         Stop   Guard
       Bits                                                 Bits   Bits
      CCCH - Common Control CHannel

   CCCH shares Timeslot 0 with BCH on a Multiframe
   CCCH consists of PCH , RACH & AGCH.
   PCH - Paging Channel is used to alert mobiles on
    incomming calls. PCH carries IMSI to page for Mobiles BCH
    in the cell. PCH is Downlink channel.
   RACH - Random Access Channel - is a short burst
    sent by mobile to BTS , to initiate a call request .
    RACH uses Timeslot 0 on reverse BCH channel on
    Uplink.
   AGCH - Access Grant Channel - When mobile sends a
    RACH to BTS, BTS responds by allocating a SDCCH
    channel to mobile over AGCH.
      RACH - Random Access CHannel

                       88 bits
      8           41                36        3      68.25
             Synchronisation     Encrypted   Stop   Extended
     Start
             Bits                Data Bits   Bits   Guard Period
     Bits



   Used by the MOBILE to get attention from
    BASE STATION in the Uplink.
   Several mobiles might originate RACH
    simultaneously.
   RACH uses a Slotted ALOHA access scheme.
   Mobile doesn't know path delay
      –So RACH has to be a special SHORT BURST
      –Mobile sends normal burst only after
       getting Timing Advance on Downlink
       SACCH
   BCH & CCCH              - 51 Frame structure - DOWNLINK
      Frame number ( DOWN LINK )
Time 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
slots F S B B B B A A A A F S P P P P P P P P F S
   0
   1
   2
   3


       26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
                   F   S                           F   S                            I
   0
   1
   2
   3

                   FCCH - Frequency correction Channel
                   SCH - Synchronisation Channel
                   BCCH - Broadcast Control Channel
                   AGCH - Access Grant Chan
                   PCH - Paging Channel
        BCH & CCCH           - 51 Frame structure - UPLINK
        Frame number ( UP LINK )
         0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Time
                     RA RA                           RA RA RA RA RA RA RA RA    R     R   R   R
slots                CH CH                           CH CH CH CH CH CH CH CH    A     A   A   A
   0                                                                            C     C   C   C
                                                                                H     H   H   H
   1
   2


         26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
        RA RA RA RA RA RA RA RA RA RA RA                            RA RA
         CH CH CH CH CH CH CH CH CH CH CH                            CH CH
   0

   1
   2



         RACH - Random Access Channel
         ( A short burst is transmitted by mobile towards BTS on RACH)
DCCH      - Dedicated Control Channels

   Dedicated Control Channels have a TCH like
    allocation. DCCH have three Sub Channels.
   SDCCH - Standalone Dedicated Control Channel
    This is used as an interim channel before final
    assignment of TCH. SDCCH is used for signalling
    and Authentication message transfers.
   FACCH - Fast Associated Control Channel . FACCH
    is used by BTS to command a handoff to the mobile.
    A TCH frame is used up by FACCH , since handoff has
    to take place on priority.
   SACCH - Slow Associated Control Channel - SACCH
    flows at a slower rate on Uplink & Downlink along
    with TCH or SDCCH. During a call, SACCH flows once
    for every 24 Frames of TCH .
SDCCH - Stand-alone Dedicated Control
CHannel



   USED DURING CALL SET-UP

   Stepping Stone between BCH and TCH

   Used for Authentication Etc.
                                           TCH

                                   SDCCH         SDCCH

                             BCH           BCH       BCH
    SACCH - Slow Associated Control CHannel



   DOWNLINK ( BTS - MS )
     – Mobile Tx Power Commands
     – Mobile Timing Advance
     – Cell's Channel Configuration


   UPLINK ( MS - BTS )
     – Received signal quality report (RXQual)
     – Received signal level report (RXLev)
     – Adjacent BCH power measurements
     – Mobile's status
    FACCH - Fast Associated Control CHannel

                   57             26       1       57      3 8.25
             3             1
                   bits           bits             bits      bits
            Tail        Control          Control          Tail
            bits   Data  bit                bit           bit    Guard
                                                   Data
                               Miidamble                         Period

 INTERRUPTS TCH ON UPLINK AND
  DOWNLINK
 Rapid message exchange for handovers

 Control Bits either side of midamble:

   –Indicate TCH ( 0 ) or FACCH ( 1 )
SDCCH - Combined Channel Config
( Shares Time slot 0 with BCH and CCCH )

    Frame number ( DOWN LINK )
     0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
    F   S   B   B    B   B   A   A   A   A   F   S   P   P   P   P   P   P   P   P   F   S   D   D   D   D

0
1
2
3

     26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
    D   D   D   D    F   S   D   D   D   D   D   D   D   D   F   S   H   H   H   H   H   H   H   H   I
0
1
2
3


                    SDCCH ( D ) : Standalone Dedicated Control Channel
                    SACCH ( H ) : Slow Associated Control Channel
        BCH & CCCH              - 51 Frame structure - UPLINK
        Frame number ( UP LINK )
         0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Time
        S       S   S   S RA RA S SA SA SA SA SA SA SA RA RA RA RA RA RA RA RA     R     R   R   R
slots   D       D   D   D CH CH A CC CC CC CC CC CC CC CH CH CH CH CH CH CH CH     A     A   A   A
   0    C       C   C   C       C H H H H H H H                                    C     C   C   C
        C       C   C   C      CH                                                  H     H   H   H
        H       H   H   H
   1
   2


            26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
        RA RA RA RA RA RA RA RA RA RA RA SD SD SD SD SD SD SD SD RA RA SD SD SD SD
         CH CH CH CH CH CH CH CH CH CH CH CC CC CC CC CC CC CC CC CH CH CC CC CC CC
   0                                      H H H H H H H H               H H H H

   1
   2



         RACH - Random Access Channel
         ( A short burst is transmitted by mobile towards BTS on RACH)
   TCH - Traffic Channel
                         156.25 bits or 576.92 uS

                       57             26           57     3
                 3             1               1
                       bits           bits         bits        bits    One
                                                                      8.25 time burst
                Tail        Control          Control    Tail
                bits   Data  bit               bit Data bit       Guard
                                                                  Period
                                   Midamble
 Traffic Channel carries the Voice data.
 Two blocks of 57 bits contain voice data .
 One TCH is allocated for every active call. While call is in
  progress if there is degradation in quality of current channel,
  BTS may shift the communication to another TCH on a different
  Carrier and/or Time slot .
 A Full rate TCH carries 13 KB/s voice data , and Half rate TCH
  carries a 6.5 KB/s voice data.
    TCH Multiframe - TCH Full rate


               26 Frames - 120 ms
          24 Carry Speech, 1 Idle, 1 SACCH

0   1 2   3   4 5     6   7 8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25


T   T T   T   T   T   T T   T T    T T   A T T   T   T T   T T   T   T T T    T -



                          SACCH                                        Idle
    TCH Multiframe - TCH Half rate

    26 Frames - 120 ms
    24 Carry Speech , 2 SACCH
    ( shared by two mobiles - a & b )
0   1 2   3   4 5   6   7 8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25


Ta Tb Ta Tb Ta Tb Ta Tb Ta Tb Ta Tb Aa Ta Tb Ta Tb Ta Tb Ta Tb Ta Tb Ta Tb Ab



                        SACCH-a                                     SACCH-b
      TCH and SACCH - FRAMES

Time Frame number
Slots 0 1 2 3 4 5 6                7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
  0 F     S   B   B   B   B    A   A   A   A   A   A   A   A   F   S   P    P   P   P   D    D   D   D   D    D
             Click here to type bulleted text
  1 T     T   T   T   T   T    T   T   T   T   T   T   SA T    T   T   T    T   T   T   T    T   T   T       TIdle

  2
      T   T   T   T   T   T    T   T   T   T   T   T   SA T    T   T   T    T   T   T   T    T   T   T   T    Idle
  3
      T   T   T   T   T   T    T   T   T   T   T   T   SA T    T   T   T    T   T   T   T    T   T   T   T    Idle
  4

  5 T     T   T   T   T   T    T   T   T   T   T   T   SA T    T   T   T    T   T   T   T        T   T   T    Idle

  6 T     T   T   T   T   T    T   T   T   T   T   T   SA T    T   T   T    T   T   T    T   T   T   T   T    Idle

  7
      T   T   T   T   T   T    T   T   T   T   T   T   SA T    T   T   T    T   T   T   T    T   T   T   T    Idle

      T   T   T   T   T    T   T   T   T   T   T   T   SA T    T   T   T    T   T   T   T    T   T   T   T    Idle



                                                                           A delay of (12 * 8)+1 Timeslots
          T - TCH         SA - SACCH       I - Idle                        is kept between two successive
                                                                           SACCH .
            FRAMES
                       1 Burst =
                       577usecs
    1 TDMA           0 1 2 3 4 5 6          7       = 8 bursts = 4.616
    Frame                                           ms
                            Multiframe
0       1    2       23 24 25         0 1       2  4 4 5
1 TCH Multiframe = 26 TF =                         8 9 0
                                    1 CCH Multiframe = 51 TF =
120ms                               234.6ms
    0            1    2                     48         49      50
    0            1    2                     23         24      25
          1 Superframe = 51 x 26 CCH MF = 1326 6.12 sec
                                                   =
          TF
        0      1     2     3= 26 x 51 TCH MF =
                                         2044 2045 2046 2047
          1326 TF
        1 Hyperframe = 2048 Superframes = 2715648 TDMA Frames
                                    = 3 hrs 28 min 53 sec 760 ms
Timing Advance

 TDMA approach requires signals to arrive at BTS
 at
 the correct time. They must not overlap.




                            BTS
           Timing Advance
    RACH Burst

    T Synch         Encrypted T    Guard Period
    B Seq           bits 36 B         68.25 bp
        41 bits                       63 bits     5.25
                                    Timing Adv    GP

     BSS calculates access delay from RACH in terms of
      bits
     Informs Mobile to delay its timing in terms of
      bits
     Maximum Timing Advance of 63
H     bits
       Mobile Maximum Range
       Range = Timing Advance x bit period x velocity
                             2

    Range            = Distance between Mobile to Base Station
    Timing Advance = Delay of Bits ( 0 -- 63 )
    Bit period      = 577 / 156.25 = 3.693 usecs = 3.693 x 10e-6
    secs
    Velocity        = 3 x 10e5


    Range = ( 63 ) x ( 3.693 x 10e-6 ) x (3 x = 34.9
    10e5)                 2                   kms
H
     Hopping Traffic Channel
DOWNLINK
C1 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7


C2   0123456701234567012345670123456701234567

C3    0123456701234567012345670123456701234567

UPLINK
C1          0123456701234567012345670123456701234567


C2          0123456701234567012345670123456701234567


C3          0123456701234567012345670123456701234567


ADJACENT CELL
BCH
    GSM Operations
         Location Update           DTX

         Mobile Originated Call    Cell Broadcast

         Mobile Terminated Call    Short Message Service

         Handover                  Emergency Calls

         Security Procedures       Supplementary Services

         Cell Barring              Roaming




H
        Mobile Turn-On
       Mobile Searches for Broadcast
        Channels (BCH)

       Synchronises Frequency and Timing

       Decodes BCH sub-channels (BCCH)

       Checks if Network Allowed by SIM

       Location Update

       Authentication

H
Location Area
                                       BTS

                                                           BSC
                                             BTS
            Location Area 1
                                                   BTS




                                       BTS

                                                                        MSC
                                                            BSC
        Location Area 2         BTS


                                                   BTS

                                                            BSC
                                 BTS




                                BTS

         Location Area 3
                                 BTS

                                 BTS




                                                                  BSC

Location Area Identity
      MCC                     MNC                        LAC
    IMPORTANCE OF LOCATION AREA




      L.Area = 1         L.Area = 2
                                      L.Area = 3




                Reduce Paging Load

                Resource Planning


H
        What is Location Update


     MSC should know the Location of the Mobile for paging.
     Mobile is continously changing Location Area.
     Mobile when changes Location Area informs the MSC about its new
      L.A

     Process of informing MSC about new Location Area is Location Update


                                                    Location Update




        L.Area = 1        L.Area = 2        L.Area = 3




H
    Types of Location
    Update
            1. Normal Location
            Update.

            2. IMSI Attach.

            3. Periodic Location
            Update.

              IMSI ATTACH
    Mobile turns off and sends an IMSI Detach to
    MSC.

    Mobile turns on again and compares LAI.


H   If same,sends an IMSI attach to MSC.
    NORMAL LOCATION UPDATE



        Mobile turns on power.

        Reads the new LAI.

        If different,does a Location Update.




H
       PERIODIC LOCATION UPDATE


    Mobile enters non-coverage zone.

    MSC goes on sending Pages

    Mobile has to inform MSC after a set period.




H
        Location Update
   Mobile Changes Location Area

   Reads the new Location Area from BCCH

   Sends a RACH ( request for channel )

   Gets a SDCCH on AGCH

   Sends its IMSI and new & old LAI in a Location Update Request to MSC on
    SDCCH

   MSC starts Authentication

   If successful, Updates the new Location area for the Mobile in the VLR

   Sends a confirmation to the Mobile

   Mobiles leaves SDCCH , and comes to idle mode

H
    Mobile Originated Call
              Channel Request

              Immediate Assign

              Service Request

              Authentication

              Ciphering

              Set Up

              Call Proceeding

              Assignment

              Alerting

              Connection
H
    MOBILE TERMINATED CALL
                 Paging

            Channel Request

            Immediate Assign

            Paging Response

            Authentication

            Ciphering

            Set Up

            Call Confirmed

            Assignment

            Alerting


H           Connection
        Security
        Features
    Authenticatio
    n
      --- Process to verify the Authenticity of SIM
      --- Mobile is asked to perform an operation using
      an identity unique to SIM.

Cipherin
g

    --- Process of coding speech for secrecy
    --- The speech bits are EXORed with bit stream unique
    to MS
H
     Security Features
TMSI Reallocation



                    Loc Upd ( IMSI
                    )
                    TMSI Allocation


                    Call Setup ( TMSI )


                     TMSI Reallocation




H
      Security Features
Identity Check



                 Identity Check ( IMEI )

                     Sends IMEI




                 White listed / Grey listed / Black listed
    EIR          ?????

H
                     HANDOVER




        Cell                                  Cell
        1                                     2



    --- Handover is a process by which the control/communic
       of a Mobile is transferred from one cell to another
H
               CRITERIA FOR HANDOVER


       Receive Quality (RXQUAL) on Uplink & Downlink.

       Receive Signal Strength (RXLEV) on Uplink & Downlink.

       Distance ( Timing Advance ).

       Interference Level.

       Power Budget.



H
            Handover Decision

    BSC processes the measurement reported by Mobile
    

       and the BTS.

    BSS performs averaging function on these measurements
    

      every SACCH frame ( 480ms).

    Handover Decision algorithm is activated after a set
    number of SACCH frame periods by comparison against
         Thresholds.




H
    TYPES OF HANDOVERS

     INTRA - CELL HANDOVER

     INTER - CELL HANDOVER

     INTRA - BSC HANDOVER

     INTER - BSC HANDOVER

     INTER - MSC HANDOVER


H
            INTRA - CELL HANDOVER




      BTS




    - Handover between channels / timeslots of same cell
H
     INTER - CELL HANDOVER



                                             BTS
         C
         0                     C
                               0




    --- Handover between cells of same BTS
H
            INTRA - BSC HANDOVER

                                 BTS


      MSC              BSC


                                 BTS

    --- This type of Handover takes place if the cell to which
        which handover is to be done belongs to the sameBSC.
    --- In this the BSC handles everything without involving MSC.
    --- The MSC will be informed by the BSC after Handover.
H
            INTER BSC HANDOVER


                 BSC           BTS


      MSC


                  BSC          BTS

    --- In this type of Handover,the Mobile is handed
    over
H
       to a cell which belongs to another BSC.
    --- The MSC is completely involved in this
           INTER - MSC HANDOVER


             MSC      BSC       BTS


    GMSC


             MSC      BSC       BTS

    --- If the cell belongs to another MSC,then it is
       Inter-MSC handover.
    --- In this case the handover takes place through the
H
       interconnecting element (PSTN) between the MSC's
     WHAT IS CELL BARRING ?




    BTS



H
        Cell Barring
     Every Mobile has an access class .

     Every cell defines the Mobile classes which are
    barred access.

    USE OF CELL BARRING

        --- Reserving Cells for Handovers.

        --- Reserving Cells for a certain Mobile
        Class.
H
                What is DTX ?


    Both users talk alternately.

    Each direction of Transmission is only 50 %


    Transmitter is switched ON for useful information
    frames.



H
      Need for DTX
    ---- To increase Battery Life

    ---- To reduce the average interference level




     DTX is done by DTX Handlers which
     have the following functions.


H
          Voice Activity Detector ( VAD )


    Senses for speech in 20ms blocks

    Removes stationary noise.


    VAD is an energy detector.

    Compares Energy of filtered speech threshold



H
       Evaluation of Background noise


    Background noise is always present with speech.

    DTX cuts off this noise with speech.

    Gives an uncomfortable feeling to the listener.

    VAD takes care by inserting comfort noise.




H
              CELL BROADCAST

Message is continously broadcasted in cell/or cells

Broadcast is done on SDCCH

BCCH informs the mobile the details of SDCCH for CBCH

Mobile tunes to SDCCH at certain intervals and reads
messages

All Mobiles dont support this feature

H
              Short Message Service




       SMS        MSC/
                             BSC        BTS
       Centre     VLR




    Short Message is sent to a particular Mobile
    Station
H
                 Emergency Calls
    -- GSM Specs define ' 112' as emergency
    number

    -- '112' is accessible with or without SIM

    -- Without SIM it is sent on the best channel

    -- Mobile on sensing '112' sets the
    establishment
      cause to emergency call in the RACH

    -- Routing of this call can be done to a desired
H
      location defined in the Switch.
     GSM Phase 2 features

    Extended Frequency Band ( 50 more channels )

    Multiple and Alternate Ciphering Algorithm

    Half - Rate Coding

    Compatibility with DCS 1800 Specifications

    Enhancement of SMS and SIM functions

    Additional functions for bearer services

H
       GSM Phase 2 + features

     Data transmission at 64 Kbps and above

     DECT access to GSM

     PMR/ Public Access Mobile Radio ( PAMR ) - like capabilities

     GSM in the local loop

     Packet Radio

     SIM enhancements

     Premium rate services ( e.g. Stock prices sent to your
     phone )
H
    Automatic National Roaming



                                 PLMN "B"
      PLMN
      "A"



                                            Roamer from
                                            "A"
                     STP



    PLMN
    "D"                          PLMN "C"
H
      Automatic International Roaming




                                              PLMN "A"
                            Interntl
                            Gateway

          Country
          Interntl
          Gateway                       Country
                                        Interntl
                                        Gateway



    PLMN "Z"




H

				
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posted:6/5/2010
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Description: Gsm mobile communication basic