1 Introduction to GSM

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    System Model

    9804649

    AUC

    H LR E IR

    SS

    BSS

    M S C

    B T S

    M S

    N M C and O M C

    Swi tching System

    S igna ling transmissio n

    Cal l conn ections and

    signa ling tran smissio n

    B ase S ta tion System

    O ther

    n etworks

    B S C

    G M S C

    V LR

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    Network elements in GSM

    MS

    PLMN

    PSTN

    ISDN

    AUC

    EIRHLR

    VLR

    MSC

    BSC

    BTS

    GMSC

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    SA2

    MSC

    VLR

    MSCMSC

    VLR

    BSC BSC

    LA1LA2

    GMSC

    MSC

    BTS

    SA1

    HLR

    AUC

    EIR

    SA - Service Area

    LA - Location Area

    BTS - Base Transceiver Station

    BSC - Base Station Controller

    MSC - Mobile Switching Center

    VLR - Visitor Location RegisterGMSC - Gateway MSC

    EIR - Equipment Identity Register

    AUC - Authentication Center

    HLR - Home Location Register

    Mobile identity

    SIM card

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    Base Station System

    Ba se S ta tio n System

    B S C

    BTS

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    BSS in Ericssons GSM Systems

    9805050

    MSC TRC BSC

    BSSSS

    RBS

    BSC/

    TRC RBS

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    Transmission Rates in BSS

    9805051

    M SC /

    V LR

    TR C

    B SC

    RB S

    B SC /

    TR C

    RB S

    R B S

    RB SRB S

    R B S RB S

    R B S

    B SC

    RB S

    RB SRB S

    RB S

    M SC /V LR

    B S C

    RB SR B S

    64 kbits/sp e rcal l

    16 K b /sfu ll- ra te

    3 3 .8 Kb /s p e rfu ll- ra te cal l

    16 Kb /s

    fu ll- ra te

    16 Kb /s

    fu ll- ra te

    16 Kb /sfu ll- ra te

    64 kbits/sp e rcal l

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    Switching System

    S S

    M S C /V LR

    E IR

    IL R

    G M S C

    D TI

    AUC

    H LR

    S M S -G M S C

    S M S -IW M S C

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    VLR-HLR Interaction

    9805099

    H LR

    UpdateD

    ele

    te

    M S C/VLR M S C/VLR

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    HLR interrogationPSTN/

    ISDNGMSCHLRMSC/VLR

    IAMSend Routing

    Information

    Send Routing

    Information

    IAM

    Provide

    Roaming Number

    ProvideRoaming Number

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    Mobile Station

    9600279

    M EM o b ile

    E q u i p m en t

    S IM Subscr iber Id en tity

    M od u le

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    GSM interfaces

    M S BTS B SC M S C HLR

    VLR

    M S C

    EIR

    VLR

    Um Ab is A

    B

    C

    E

    F

    D

    G

    AUC

    H

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    A Cell

    9600270

    Cell

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    Macro, Mini, Micro and Indoor Cells

    960022 3

    A n te nn a posit io ns

    M ac ro

    M in i

    MicroPico

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    MSC Service Area

    9600271

    ce ll 6

    ce ll 1 ce ll 5

    ce ll 4 ce ll 2 ce ll 3

    M S C

    LA 1LA 3

    LA 5

    LA 4

    V LR

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    Relation Between Areas in GSM

    9600 3 67

    GSM Service Area

    PLMN Service Area

    (one per operator)

    MSC Service Area

    Location Area

    Cell

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    "Hardware" view of a Sample Network

    HLR

    EIR

    AUC

    GMSC

    ILR

    MSC/VLR 1PSTN

    MSC Service Area 2

    MSC Service Area 1

    LEGENDMSC Boundary

    BSC BoundaryPCM LinksBase Station

    MSC/VLR 2

    BSC 1B

    BSC 1C

    BSC 2B

    BSC 1A

    BSC 2A

    BSC 2C

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    "Software" view of a Sample Network

    LA 1-B

    LA 1-A

    LA 2-D

    LA 2-ACell 2-A-25

    LA 2-B

    HLR

    EIR

    AUC

    GMSC

    ILR

    MSC/VLR 1PSTN

    MSC Service Area 2

    MSC Service Area 1

    LEGENDMSC Boundary

    BSC BoundaryPCM LinksBase Station

    MSC/VLR 2

    LA 2-C

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    Authentication Procedure

    MSC/VLR

    1. RAND

    3.SRES

    MS2.MS calculates SRES using RAND + Ki(SIM-card) throug A3 and Kc using RAND+Kithrough A8.

    4. CompareSRESreceived fromMSwithSRESin triplet. Iftheyareequal accessis granted.

    MSC/VLR MobileserviceSwitching CenterMS MobileStation

    RAND Random numberSRES Signed Response

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    Authentication in GSM

    VLR

    MSC

    HLRAUC

    Subscriber number (IMSI)Code key (Ki)

    Random number (RAND)Signal response (SRES)

    RAND / SRES

    RAND

    SRES

    Figure D.6.4

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    Equipment Identification

    27

    M S C/VLR

    M S

    EIR

    3. C heck IM EI

    4 . Access /ba rr ing in fo

    1 . IM EI request

    2 . IM EI

    IM EI In te rna ti onal M o b ile sta ti on Equipmen t Id en tity

    EIR Equ i p m en t Id en tity R eg ister

    M SC/VLR M o b ile servicesSwitch ing C en te r

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    OSS CNA

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    OSS Provides Central Supervision of all Network

    9804645

    OMC OMC

    H LR

    AUC/EIR

    TR C

    MSC

    BSC

    BTS

    Operat ion and

    Suppo rt Sys tem

    NMC

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    Gateway productsfor billing information

    and service

    SOG and BGW

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    GSM Modes

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    Operation Overview

    Attached (On)

    Detached (Off)

    Idle

    Busy

    Roaming

    Paging

    Handover

    Mr. Bond!!

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    Roaming

    9600275

    M S C/VLR

    M S C/VLR

    LA 1

    LA 2

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    The RBS Listening for Channel Requests and

    Measuring the Uplink on an Established

    Connection

    Signal strength!Quality!Timing!

    Accessburst!

    MS

    MS

    MS MS

    RBS

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    Monitoring BCCH Carriers

    9600479

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    GSM Frequency Bands

    9805092

    0 .8GHz 0 .9 1 .0 1 .1 1 .2 1 .3 1 .4 1 .5 1 .6 1 .7 1 .8 1 .9 2 .0

    GSM 900 GSM 1800 GSM 1900

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    Frequency bands for the different GSM-based

    networks. (Values within brackets refer to E-GSM)

    Network type

    GSM 900 (880)890-915/(925)935-960 MHz GSM 900

    GSM 1800 1710 - 1785/1805 -1880 MHz GSM 1800

    GSM 1900 1850 - 1910/1930 -1990 MHz GSM 1900

    EricssonsImplementations

    Frequency bandUL/DL

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    Uplink and Downlink on a Radio Channel

    9804646

    U p lin k

    D o w nlink

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    System Parameters

    f

    up link down link

    Carrier spacing

    Duplex spacing

    Bandwidth spacing

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    Duplex Distance

    9805042

    890 960915 93 5M H z

    U p link D ow nlink

    D u p lex D is tan ce (4 5 M H z)

    Band w id th (2 x 25 M H z)

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    Duplex distances for different frequency bands

    S tandard GSM 900 GSM 1800 GSM 1900

    Dup lex dis t. 45 MHz 95 MHz 80 MHz

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    Carrier Separation

    9805041

    C a rrierS e p a ra tio n (200 KHz)

    895 .4 895 .6M H z

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    Neighboring Cells Cannot Have the Same

    Frequency (Simplified)

    9600 3 68

    B

    G

    A

    C

    G

    AD

    F

    F

    E

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    TDMA

    9805008

    0

    F re q ue ncy 1

    1 2 3 4 5 6 7

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    Basic TD

    MA frame, timeslot, and burst structures

    0 1 2 3 4 5 6 7

    4 .615 m s

    3 57 1 26 1 57 3

    B urst

    148 B it s

    156 .25 B it s

    0 .577 m s

    D a taT ra in ingD a ta

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    Analog Signal

    9805018

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    Digital Signal

    9805019

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    A/D Conversion

    9600 3 71

    Analo g

    A/D C o nversio n

    D ig it al

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    Analog Signal Sampling

    9600372

    t

    Analog ue signa l

    t

    S am p ling

    T s

    t

    S am p le d signa l

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    Regeneration ofDigital Signal

    9805020

    T ran smit ted R eceived R e ge n e ra te d

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    Quantization

    9600 373

    q 7

    q 6

    q 5

    q 4

    q 3

    q 2

    q 1

    q 0

    T s 2 T s 3 T s 4 T s 5 T s 6 T s 7 T s 8 T st ime

    }

    S am p le d

    va lu e

    Q u an tize d

    va lu e

    D = Q ua n tize d error

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    Path loss

    Shadowing

    Rayleigh fading

    Signal strength Time dispersion

    Time Alignment

    Radio Parameters that are important for GSM

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    Problems Solution Fading

    Distance Eventually leading to handover

    Shadowing Make a better coverage of the cell or smaller cells

    Rayleigh Antenna diversity- two antennas on the BS, 5-6 m apartRepeated change offrequencies after each frame

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    Shadowing

    9600 3 77

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    Rx Signal Strength

    9600 380

    F ad ing

    m a rg in

    S S (dB)

    D is tanc e (met ers )

    G lob a l m ean va lu e

    F ad ing d ip (R ay le igh )

    R eceiver s e n sit ivity

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    Rx Signal Strength Versus Distance

    9600379

    log (d is tan ce )

    S

    ignallevel(dB

    )

    P a th lo ss ( )

    R ay le igh fad ing (-)

    L og no rm al

    fad ing ( )

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    Rayleigh Fading

    9600378

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    Time Dispersion

    9600521

    1

    1

    1 .

    0

    0

    2 .

    1

    1

    3.

    1

    0

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    The Time Alignment Problem

    A. Close to BTSBTS

    T DMA-frameB . Far away

    from BTSA .

    B .

    TS0 TS1 TS2

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    Intermodulation in a 900 MHz cellular system

    890 900 910 920 93 0 940 950 960 M H z

    RX band

    Dup lex d is tance (D )

    TX band

    Alloca te d R X band (B)

    (1 0 M H z in

    this e xam p le )

    Alloca te d TX band (B)

    (1 0 M H z in this exam p le )IM 7 IM 5 IM 3

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    System

    GSM900

    DCS1800

    PCS1900

    NMT450

    Duplex

    distance,

    D, (MHz)

    45

    95

    80

    10

    IM3

    22.5

    47.5

    40.0

    5.0

    IM5

    15.0

    31.7

    26.7

    3.3

    IM7

    11.3

    23.8

    20.0

    2.5

    IM9

    9.0

    19.0

    16.0

    2.0

    Maximum band, B, (MHz) to avoid IM order:

    Worst-case relations

    IM3 in Rx band ifD/B < 2

    IM5 in Rx band ifD/B < 3

    IM7 in Rx band ifD/B < 4

    IM9 in Rx band ifD/B < 5

    Definitions:IM3, IM5, etc.=Intermodulation products of 3rd, 5th, etc.,

    D = Duplex distance (MHz)

    B = Allocated band (MHz)

    Worst case = IM from the lowest and

    the highest frequencies in the allocated band

    Intermodulation (IM) in cellular systems

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    Co-Channel InterferenceCarrier

    Interference

    Distance

    f1 f

    1dB

    C I

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    Reuse distance and carrier-to-interference ratio

    S (dB)

    S(A,f1) S(B,f1)

    Reuse distance for f1 Distance from A

    >18 dB in analog systems

    >7 dB in digital systemsC

    I

    Figure D.5.4

    I C

    A B

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    Co-channel interference

    f1

    f1

    B

    A

    Figure D.5.3

    Acceptable

    Speech quality

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    Adjacent Channel Interference

    AC

    CarrierAdjacent

    Distance

    f1 f2

    dB f2

    = f1

    + 200 kHz

    -9 dB

    3 dB

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    Locating the BTS close to the reflecting object to

    combat ISI

    D 2

    D 0

    D 1

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    Pointing the antenna away from the reflecting object

    to combat ISI

    M o un ta in Site with an te nna

    po in ting aw ay

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    Space Diversity

    9805015

    T xR x (B )R x (A )

    A n te nnaD iversity

    D iversity

    System

    O utput

    R eceiver

    S e n sivity

    L e ve l

    R eceived

    S igna l

    L e ve l

    A, B c o m b in ed

    R ec eiv er A

    R ec eiv er B

    N o D iversity

    T x R x

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    Block coding

    In form a tion

    B lo ck

    In form a tion

    B lo ck

    R edundan t

    d ig its

    B lo ck

    cod ing

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    Interleaving

    P E TES TA NA N NAV E R AM e s sage

    b lo ckP

    S

    A

    V

    ?

    ?

    ?

    ?

    T

    A

    N

    R

    E

    N

    A

    A

    P ?TES ?ANA ?NAV?RA

    S ing le

    b it

    errors

    P SAV

    E T N E

    TA N R

    E NA A

    T x s ide R x s ide

    P

    S

    A

    V

    E

    T

    N

    E

    T

    A

    N

    R

    E

    N

    A

    A

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    Interleaving for full rate speech1

    9

    17

    25

    449

    2

    10

    450

    3

    11

    451

    4

    12

    452

    5

    13

    453

    6

    14

    454

    7

    15

    455

    8

    16

    456

    8 fram es

    57 bits

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    Second level of interleaving1st C O L U M N IN A

    2 n d C O L U M N IN A

    3rd C O L U M N IN A

    4 th C O L U M N IN A

    5 th C O L U M N IN A+1st C O L U M N IN B

    LA S T B U R S T W I T H IN FO R MATIO N

    B IT S F R O M T H E A - B L O C K

    LA S T B U R S T W I T H IN FO R MATIO N

    BIT S F R O M T H E B - B L O C K

    A1 A17 A3 3 ... A9 A25 A41...

    A4 A 20 A3 6 ... A12 A28 A44...

    B1 A5 B1 7 A2 1 B 3 3 A 3 7 ... B9 A1 3 B2 5 A2 9 B4 1 A4 5 ...

    B4 A8 B2 0 A2 4 B 3 6 A4 0 ... B12 A16 B28 A 3 2 B4 4 A4 8 ...

    C1 B5 C1 7 B2 1 C 3 3 B 3 7 ... C9 B1 3 C2 5 B2 9 C4 1 B4 5 ...

    C4 B8 C2 0 B2 4 C 3 6 B4 0 ... C12 B16 C28 B 3 2 C4 4 B4 8 ...

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    Channel Coding

    9805016

    B lock

    coder 5 0 V ery impor tan tbits

    1 32 Im p o r tan tbits

    7 8 N o ts o impor tan tbits

    1 :2

    Conv o lu t ional

    Code r

    4 56

    4 Ta il bits

    5 3 b its 3 78 bits

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    Channel coding and interleaving for control

    channels

    23 octets 21 octets 2 octets

    BCCH, CCCH, SDCCH, FA C C H SA C C HL2 b loc k L2 b loc k

    18 4 18 4

    184 40

    224 4

    22 4

    22 8

    L2 b lo ck

    E rror D etection (FIRE)

    45 6

    2 x 228 = 456

    57 57 57 57 57 57 57 57

    45 6 bits in te rlea ve d o ve r 8 hal fbursts

    BCCH, CCCH, SDCCH, SACCH/C

    4 fram es 8 fram e s

    FA C C H

    10 4 fram es , 480 m s

    L2 b lo ck + F IRE

    L2 b lo ck + F IRE co ded wi th R = 1 /2

    TAIL

    SACCH/T

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    Frequency Hopping

    9600535

    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

    D ow nlink C 1

    U p lin k C 1

    N N + 1

    T D MA fram e no .

    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

    D ow nlink C 2

    U p lin k C 2

    N N + 1

    T D MA fram e no .

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    Timing Advance

    9600538

    0 1 2 3 4 5 6 7

    T im e

    0 1 2 3 4 5 6 7

    S ynchron iza tio n t ime

    S ta rt

    S e nd in g

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    Segmentation and Speech Coding

    9600522

    01100011000111110011100

    Speech Code

    20 ms

    Speech S ignal

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    Interleaving of 20 ms of Encoded Speech

    9600531

    1

    9

    1 7

    2 5

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    449

    2

    10

    I

    I

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    4 50

    3

    11

    I

    I

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    4 51

    4

    1 2

    I

    I

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    4 52

    5

    1 3

    I

    I

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    4 5 3

    6

    14

    I

    I

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    4 54

    7

    15

    I

    I

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    4 55

    8

    1 6

    I

    I

    I

    I

    I

    I

    II

    I

    I

    I

    I

    I

    I

    456

    8 b lo c k s

    5 7 bits

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    Speech Frame

    9600532

    2 0 m s s p e e c h

    4 56 bits = 8 x57

    A20 m s speech

    456 bi ts = 8x57

    B2 0 m s s p e e c h

    4 56 bits = 8 x57

    C20 m s s p e e c h

    456 bits = 8 x57

    D

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    Second Level of Interleaving

    9600534

    A/8

    A/8

    A/8

    A/8

    B/8 A/8

    B/8 A/8

    B/8 A/8

    B/8 A/8

    C /8 B/8

    C /8 B/8

    C /8 B/8

    C /8 B/8

    D /8 C /8

    D /8 C /8

    D /8 C /8

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    GSM Transmission Process

    9600539

    3 3.8 kbit/s

    22 .8 kbit/s

    1 3 kbit/s

    8 kHz1 3 bits

    Transmitting par t

    Receiving par t

    S p eake r

    R eceiver

    D em od u la to r

    Adaptive

    E q ual iza tion

    D e -ciphering

    D e - in te rlea v ing

    C hann e l deco d ing

    Speech de cod ing

    D/A-co nversion

    T ran smitter

    M od u la to r

    B urstform a tti ng

    C iphering

    In te rlea v ing

    C hann e l cod ing

    Speech co d ing

    S e gm en ta tio n

    A/D-co nversion

    Microphone

    1 3 kbit/s

    Transmitting part

    Receiving par t

    T ran smitter

    M od u la to r

    B urstform a tti ng

    C iphering

    In te rlea v ing

    C hann e l cod ing

    D/D-co n version

    8 kH z8 bits

    64 kbit/s P C M

    R eceiver

    D em od u la to r

    Adaptive

    E q ualiza tion

    D e -ciphering

    D e -in te rlea vi ng

    C hann e l D e co d ing

    G S M Network

    M o b ile equipmen t

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    GPRS Logical Architecture

    Traffic and signaling

    Signaling

    TE Terminal Equipment

    MT Mobile TerminalMS Mobile Station

    BSS Base Stat ion SystemBTS Base Transceiver Station

    BSC Base Station Controller

    GMSC Gateway Mobile Services SwitchingCenter

    MSC Mobile services Switching Center

    VLR Visitor Location RegisterHLR Home Location Register

    AUC Authentication Center

    EIR Equipment Identity RegisterSGSN Serving GPRS Support Node

    GGSN Gateway GPRS Support NodeUm Air Interface

    A, Abis Interfaces (GSM)

    Gx Interfaces (GPRS)

    ExternalIP Network

    (CorporateLAN)

    Gi

    TE MT

    MS

    BSC

    GMSC

    MSC/VLR

    SGSN

    EIR

    HLR

    AUC

    GGSNIP-BackboneNetwork

    External

    IP Network(Internet)

    External

    X.25 Network

    GsGf

    Gr

    BTS

    Gb

    UmISDN/PSTN

    Gn

    A

    Other

    PLMN

    Gp

    BSS Abis