6949178 GSM Fundamentals RF

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    GSM Fundamentals & RF

    GTL welcomes you to the Basiccourse on GSM Fundamentals &

    RF(GTL-GSM RF-001)

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    What you will learn here? Basic Telecom concepts

    Various Wireless Technologies

    Cellular concepts & Principal of cellular Comm.

    GSM Network Architecture

    GSM channel Architecture

    Call Flows in GSM

    GSM Planning steps (Nominal Plan & RF surveys)

    GSM Optimization Steps ( Performance, Drive testing &

    Benchmarking)

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    BASIC Telephony

    Off Hook

    Dial Tone

    Dialing Digits

    RBT

    Conversation

    Ring

    Off Hook &

    Conversation

    SignalingTraffic

    SWITCH / EXCHANGE

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    Wireless Communication

    Alternative means of wireless communication

    Walkie - Talkie

    Pagers

    Trunked private radios

    Mobile Phone - the magic technology that enables

    everyone to communicate anywhere with anybody.

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    Wireless Telephony

    BSCBTS BTS

    Mobile Subscriber...

    MSC

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    Different Standards Worldwide

    Till 1982 Cellular Systems were exclusively Analog Radio

    Technology.

    Advanced Mobile Phone Service (AMPS)

    U.S. standard on the 800 MHz Band

    Total Access Communication System (TACS)

    U.K. standard on 900 MHz band

    Nordic Mobile Telephone System (NMT)

    Scandinavian standard on the 450 & 900 MHz band

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    Different Standards Worldwide

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    GSM - 900GSM - 900

    The term GSM-900 is used for any GSM system which operates in any 900 MHz band.

    P-GSM - 900

    P-GSM-900 band is the primary band for GSM-900 Frequency band for primary GSM-900 (P-GSM-900) : 2 x 25

    MHz

    890 915 MHz for MS to BTS (uplink)

    935 960 MHz for BTS to MS (downlink)

    E-GSM - 900

    In some countries, GSM-900 is allowed to operate in part or in all of the following extension band. E-GSM-900

    (Extended GSM-900) band includes the primary band (P-GSM-900) andthe extension band :

    880 890 MHz for MS to BTS (uplink)

    925 935 MHz for BTS to MS (downlink)

    R-GSM-900R-GSM-900

    R-GSM-900 (Railway GSM-900) band includes the primary band (P-GSM-900) and the following extension

    band:

    876 890 MHz for MS to BTS (uplink)

    921 935 MHz for BTS to MS (downlink)

    GSM-1800GSM-1800

    Frequency band: 2 x 75 MHz

    1710 1785 MHz for MS to BTs (uplink)

    1805 1880 MHz for BTS to MS (downlink)

    Different Standards Worldwide

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    Industry Vs Technology Spread

    Telecom Service Providers/Operators

    GSM

    CDMA

    Basic-WLL

    Internet Services

    Long Distance

    Vendor

    Telecom Consultancy

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    Analog Mobile Telephony

    End of 1980s Analog Systems unable to meet continuing

    demands

    Severely confined spectrum allocations

    Interference in multipath fading environment

    Incompatibility among various analog systems

    Inability to substantially reduce the cost of mobile

    terminals and infrastructure required

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    Digital Mobile Telephony

    Spectrum space - most limited and precious resource

    Solution - further multiplex traffic (time domain)

    Can be realized with Digital Techniques only

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    GSM History and Organization

    1979 Europe wide frequency band reserved for

    Cellular

    1982 Groupe Speciale Mobile created within

    CEPT

    1986 GSM had full time in Paris

    1988 ETSI takes over GSM Committee

    1990 The phase 1 GSM Recommendations

    frozen

    1991 GSM Committee renamed Special Mobile

    Group and GSM renamed as Global

    System for Mobile Communication

    1992 GSM launched for commercial

    operations

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    Service Industry Service Provider is not a Equipment Manufacturer.

    The Service Provider has a license to operate in a

    geographical boundary (state/circle/ country).

    It buys equipment from OEM Suppliers (Vendors).

    Installs & commissions the equipment thus making its own

    Network.

    Provides the desired service to its subscribers.

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    Vendor

    Vendor is a Equipment Manufacturer.

    It supplies Product, Consultancy and Trainings

    Service provider has the option of taking the Consultancy

    and Training

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    Cellular Communication A cellular system links Mobile subscribers to Public

    Telephone System or to another Mobile subscribers.

    It removes the fixed wiring used in a traditional telephone

    installation.

    Mobile subscriber is able to move around, perhaps can travel

    in a vehicle or on foot & still make & receive call.

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    Advantage of Cellular

    Communication Mobility

    Flexibility

    Convergence

    Greater QOS

    Network Expansion

    Revenue/Profit

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    WHATIS CELLULAR TELEPHONY ?

    CONSIDERATIONS -

    TFREQUENCY

    TSUBSCRIBER

    DENSITY

    TCOVERAGE

    Base Station

    Base Station

    Base Station

    Base StationBase Station

    Base Station

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    The Cell Cellular Radio involves dividing a large service area into region

    called cells.

    Each cell has the equipment to switch, transmit and receive calls

    Cells - Reduce the need of High powered transmission

    Cells - Conventionally regarded as being hexagonal, but in reali

    they are irregularly shaped.

    Cell shape is determined by the nature of the surrounding

    area e.g. Hills , tall building etc.

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    Cell Size

    Large Cells

    35 Km

    Remote Areas

    High TransmissionPower

    Few subscribers

    Small Cells

    Near about 1 KM

    Urban Areas

    Low TransmissionPower

    Many Subscribers

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    Coverage & Capacity

    Coverage

    Percentage of the geographical area covered by cellular

    service where mobile telephony is available

    Capacity -

    Number of calls that can be handled in a certain area

    within a certain period of time. Capacity can also refer to the probability that users will

    be denied access to a system due to the simple

    unavailability of radio channels.

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    Frequency Spectrum

    Designation Abbrevia tion Frequencies F ree-space Wavelengths

    Very Low Frequency VLF 9 kHz - 30 kHz 33 km - 10 km

    Low Frequency LF 30 kHz - 300 kHz 10 km - 1 km

    Medium Frequency MF 300 kHz - 3 MHz 1 km - 100 mHigh Frequency HF 3 MHz - 30 MHz 100 m - 10 m

    Very High Frequency VHF 30 MHz - 300 MHz 10 m - 1 m

    Ultra High Frequency UHF 300 MHz - 3 GHz 1 m - 100 mm

    Super High Frequency SHF 3 GHz - 30 GHz 100 mm - 10 mm

    Extremely High Frequency EHF 30 GHz - 300 GHz 10 mm - 1 mm

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    GSM - IN CELLULAR

    TELEPHONY Each Cell in the Cellular Network consists of one or more

    RF carriers.

    An RF carrier is a pair of radio frequencies

    One used in upward direction by MS - Uplink

    Other used in downward direction by BTS - Downlink

    The transmit and receive frequencies are separated by agap of 45 MHz in GSM of 75 MHz in DCS.

    There are 124 carries in GSM Band. With each carriercarrying 7 timeslots, only 124 x 7 = 868 calls can be made!

    Frequency Reuse is the solution

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    Frequency & ARFCN

    ul=

    89

    0to

    915

    MH

    z

    dl=

    935

    to96 0

    MH

    z

    Ful(n) = 890.0 + (0.2) *n MHz

    Fdl(n) = Ful + 45 MHz

    where n =ARFCN ; 1 n 124

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    Power

    Frequency

    Time

    FDMA

    Frequency

    Power Time

    TDMA

    FrequencyCDMA

    Power

    Time

    Multiple Access

    Methods

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    Frequ

    ency

    Time

    Power

    TDMA

    Frequ

    ency

    Time

    Power

    FDMA

    Frequ

    ency

    Time

    Power

    CDMA

    CODE

    FDMA: AMPS & NAMPS

    Each user occupies a private Frequency,protected from interference through physicalseparation from other users on the samefrequency

    TDMA: IS-136, GSM

    Each user occupies a specific frequency butonly during an assigned time slot. Thefrequency is used by other users duringother time slots.

    CDMAEach user occupies a signal on a particularfrequency simultaneously with many otherusers, but is uniquely distinguishable bycorrelation with a special code used only bythis user

    Multiple Access Methods

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    Frequency Reuse Pattern

    Three types of frequency reuse patterns

    7 Cell reuse pattern

    4 cell reuse pattern

    3 cell reuse pattern

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    3 Site Reuse Patternc2

    c1

    c3

    a1

    a2

    a3

    b1

    b2

    b3

    c1c2

    c3

    Cell Re-use

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    Cell Dia = R

    FREQUENCY RE - USE

    Frequency Re-use

    7/21 cell cluster

    1

    2

    3

    4

    5

    6

    7

    D D=R (3N)where N is Cluster size

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    Principal Of Sectorization

    Omni Directional Cells

    120 degree Sectors

    60 Degree sectors

    Each Sector in a Site has its own allocation of Radio

    Carriers

    Advantage

    By frequent reuse of frequency more capacity can be

    achieved

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    5 Multipath Fading results in variations in signal strength which is known as

    Rayleigh Fading.

    5 Rayleigh Fading phenomenon is dependent on path difference and hence

    frequency of reception.

    5

    A fast moving mobile may not experience severe effect of this fading sincethe path difference is continuously changing.

    5A slow moving mobile ( or a halted mobile ) may experience severe

    deterioration in quality.

    5 But, if the frequency of reception is changed when this problem occurs,

    could solve it.5 The fading phenomenon is fast and almost continuos, this means the

    frequency change should also be continuos.

    5 This process of continuously changing frequency is known as Frequency

    Hopping.

    FrequencyHopping

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    5 Frequency Hopping is done in both Uplink and Downlink .

    5 Frequency is changed in every TDMA Frame

    5 Mobile can Hop on maximum 64 frequencies

    5 The sequence of Hopping can be Cyclic or Non-Cyclic

    5 There are 63 Non-Cyclic Hopping sequences possible

    5 Different Hopping sequence can be used in the same cell.

    5 BCH Timeslot can never HOP, but the remaining Timeslots can

    very well hop.

    FrequencyHopping

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    Reduction in Average Interference

    5 With Frequency Hopping consistent interference will become bursty.

    5 So even though, both the co-channel cells will be using the same set of ARFCN's for

    Hopping, interference will not be continuos.

    5 This is because, GSM cells are not Frame synchronized, and change in frequency isrelated to Frame nos.

    5 If same HSN is used in two cells, then either the interference will be nil , or if a phase

    correlation exists then it will be continuos.

    5 So the two cells should preferably use different HSN's .

    5 Sectorial cells ( controlled by the same BTS) can use same HSN, since the sectors don't

    come up at the same time.5 Cells if they are synchronized, can use same HSN, if each cell has an offset of some

    TDMA frames.

    5 Offset of TDMA frames is also required to avoid SACCH occurring at the same time in all

    synchronized cells, as they kills away the objective of DTX.

    FrequencyHopping

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    a1

    a2

    a3a3

    a4a6

    a5

    Cell Sectorisation

    OMNI CELL

    1 ANTENNA

    b1

    b2

    b3

    120O CELLS

    3 ANTENNAS

    60O CELLS

    6 ANTENNAS

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    Features of GSM Compatibility

    Noise Robust

    Increased Capacity & Flexibility

    Use of Standard Open Interfaces

    Improved Security & Confidentiality

    Cleaner Handovers

    Subscriber Identification

    ISDN Compatibility

    Enhanced Range of Services

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    Handovers

    Hard Handoff

    Analog, TDMA and GSM

    Soft Handoff

    CDMA

    Break before Make Make before Break

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    120

    181

    198

    200

    132

    41

    44

    69

    75

    113

    28

    71

    73

    70

    80

    7

    8

    1112

    13 1617

    18

    19

    20

    22

    25

    32

    171

    173

    175

    182

    187

    199

    201

    213

    214

    215

    216

    218

    219

    220

    221

    222

    225

    Handovers

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    Cleaner Handovers The mobile measures up to 32 adjacent cells for

    Signal Strength (RxLevel)

    Signal Quality (RxQual)

    updated every 480 mS and sends to BTS Sophisticated Handover based on

    RxLevel

    Interference

    RxQual

    Timing Advance

    Power Budget

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    BT

    S

    BT

    S

    BT

    S

    BT

    S

    BT

    S

    BTS

    BT

    S

    BT

    S

    BSC

    VL

    R

    HL

    R EI

    R

    OM

    C

    SMS

    CBC

    AU

    C

    VMSC

    MS

    C

    Abi

    s

    A

    MS

    BTS

    BTS

    BTS

    BTSBTS

    BTS

    BTS

    BTS

    BSC

    BSC

    PSTN

    VLR

    TRAUHLR

    EIR

    OMC

    SMSC

    BC

    AUC

    VMSC

    MSC

    Abi

    s

    A

    OML

    GSM NETWORK ELEMENTS

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    Mobile Station Identities

    MSISDN : Human Identity used to call a Mobile Station

    IMEI: Serial number unique to every Mobile Station

    IMSI : Network Identity unique to a SIM

    3

    digits

    2

    digits

    10

    digits TMSI : Identity unique in a LAI

    MSRN : Mobile Station

    Roaming NoCC NDC SN

    98 XXX 12345

    MCC MNC MSIN

    404 XX 12345

    TAC FAC SNR S

    6 digits 2 digits 6 digits 1 digit

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    GSM Network Components

    Mobile Station consists of two parts-

    Mobile Equipment (ME)

    Subscriber Identity Module (SIM)

    ME

    Hardware e.g. Telephone, Fax Machine, Computer.

    SIM

    Smart Card which plugs into the ME.

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    ME (Classmark Information)

    Revision Level

    Phase of the GSM specs ME comply with.

    RF Power Capability

    Max power ME is able to Transmit.

    Ciphering Algorithm Used

    Presently A5

    Phase 2 specifies Algorithms A5/0 to A5/7.

    Frequency Capability

    SMS Capability

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    Typical

    Settings

    Mobile Equipment

    Class Power O/p

    1 20 W

    2 8 W

    3 5 W

    4 2 W

    5 0.8 W

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    SIM(IMSI)

    IMSI(International Mobile Subscriber

    Identity)

    Transmitted over Air Interface on initialization

    Permanently stored on SIM card

    15 digit Decimal

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    SIM (TMSI)

    Temporary Mobile Subscriber Identity

    Periodically changed by the System Management on

    instances like location update etc.

    Reason for use of TMSI

    To prevent a possible intruder from identifying GSM

    users, TMSI is used

    Management

    Assignment, Administration & Updating is performed

    by VLR.

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    Transcoder

    Converts 64 Kbps PCM circuits from MSC to 16 Kbps BSS

    circuits.

    Each 30 channel 2 Mbps PCM link can carry 120 GSM -

    specified voice channels.

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    Base Station System (BSS)

    BSS (Base Station System)

    BSC (Base Site Controller)

    BTS (Base Transceiver Station)

    XCDR (Transcoder)

    Network

    Switching

    System

    (NSS)XCDR

    BSC

    BTS

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    Base Station System (BSS)

    BSC

    Controls upto 40 BTS

    Conveys information to/from BTS

    Connects terrestrial circuits & Air Interface Channels

    Controls handovers between BTSs under itself

    BTS

    Contains RF Hardware

    Limited control functionality

    1 - 6 carriers in a BTS Cabinet

    7 - 48 simultaneous calls per BTS

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    BSS Configuration

    Collocated BTS

    Remote BTS

    Star Configuration

    Daisy Chain BTS Loop ConfigurationBSC

    BTS

    BTS

    BTS

    AllBTS

    on1E1

    BSC

    BTS

    B

    TS

    BTS

    BTS

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    Network Switching System(NSS)

    NSS (Network Switching System)

    MSC (Mobile Switching Centre)

    HLR (Home Location Register)

    VLR (Visitor Location Register)

    EIR (Equipment Identity Register)

    AUC (Authentication Centre)

    IWF (Interworking Function)

    EC (Echo Canceller)

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    GSM Network Component

    MSC

    Call Switching

    Operation & Management Support Internetwork Interworking

    Collects call billing data

    Gateway MSC MSC which provides interface between PSTN & BSSs

    in the GSM Network.

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    Home Location Register (HLR)

    Reference database for the Subscriber profiles-

    Subscriber ID (IMSI & MSISDN)

    Current VLR Address Supplementary Services subscribed

    Supplementary Service Information

    Subscriber Status (Registered/deregistered) Authentication Key and AUC functionality

    TMSI

    MSRN

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    Visitor Location Register (VLR)

    Temporary Data, which exists as long as the subscriber is

    active in a particular Coverage area.

    Contains the following- Mobile Status (Busy/ Free/ No Answer/etc.)

    Location Area Identity (LAI)

    TMSI MSRN (Mobile Station Roaming Number)

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    Equipment Identity Register (EIR)

    Contains Database for validating IMEI

    White List (valid ME)

    Black List (Stolen ME)

    Grey List (Faulty ME)

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    Provides function to enable the GSM System to

    interface with Public/Private Data Networks.

    The basic feature of the IWF are Rate Conversion

    Protocol adaptation

    IWF incorporates Modem Bank.e.g. GSM DTE PSTN DTE

    IWF Analogue Modem

    Inter Working Function

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    Echo Canceller

    Echo is apparent only in Mobile - Land conversation &

    is generated at the 2 wire to 4 wire interface.

    To avoid it, Echo Canceller (EC) is used.

    Echo is irritating to MS Subscriber

    Total Round Trip delay of 180 ms in the GSM system

    EC is placed on the PSTN side of the Switch

    Cancellation up to 68 ms with EC

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    Operation & Maintenance Centre

    Event & Alarm Management

    Fault Management

    Performance Management

    Configuration Management

    Security Management

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    GSM Terrestrial Interfaces

    Broadly classified into two types of interfaces-

    Standard Interfaces

    2 Mbps Trunks (E1)

    Signalling System No. 7 SS7 ( CCS7)

    X.25 (Packet Switched Mode)

    GSM Interfaces

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    GSM Interfaces

    Um MS - BTS

    Abis BTS - BSC

    A BSC - MSC

    B MSC - VLR

    C MSC - HLR

    D VLR - HLR

    E MSC - MSC

    F MSC - EIR

    G VLR - VLR

    H HLR - AUC

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    GSM protocols are basically divided into three layers:

    Layer 1: Physical layer Enables physical transmission (TDMA, FDMA, etc.) Assessment of channel quality Except on the air interface (GSM Rec. 04.04), PCM 30or ISDN

    links are used (GSM Rec. 08.54 on Abis interface and08.04 onA to F interfaces).

    Layer 2: Data link layer Multiplexing of one or more layer 2 connectionson control/signaling channels Error detection (based on HDLC) Flow control Transmission quality assurance Routing

    Layer 3: Network layer Connection management (air interface) Management of location data Subscriber identification Management of added services (SMS, call forwarding,

    conferencecalls etc.

    GSM Protocol Layers

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    Basic Processes

    AUTHENTICATION

    CIPHERING

    REGISTRATION

    CALL ESTABLISHMENT

    HANDOVER / HANDOFF

    ROAMING

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    AUTHENTICATION ALGORITHM

    NSS

    MS

    HLR

    AUC

    AUTH.ALGORITHMS

    A3

    SIM

    MS

    AUTH.ALGORITHMS

    A3

    Ki

    RAND

    RAND

    COMPARE

    SRES

    SRES

    Ki

    AIR INTERFACE

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    Ciphering Data protection is required on air interface.

    A specific key called Ciphering Key (Kc), is generated

    from RAND and A8 algorithm.

    A8 is on the SIM.

    A8

    RANDKi

    Kc

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    Ciphering

    A5Data

    Kc

    Ciphered

    Data A5

    Kc

    Data

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    Transmission Media

    Access Network

    Microwave 15 /23 GHz

    Backbone Network

    Microwave 7 GHz

    Optical Fibers

    Leased Line( From Dot or any other service provider on

    any media)

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    Optical Fiber

    Different Possible Combinations

    Mono Mode Step Index 10 / 125 m

    Mono Mode Graded index

    Multi Mode Step Index 100 / 300 m

    Multi Mode Graded Index 75 / 130 m

    Mono Mode Graded Index would have been the bestbut fabrication not possible

    140 Mbps OLTE , Mono Mode Step Index in our case

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    Channels On Air Interface

    Physical Channel

    Logical Channel

    Physical Channel

    Physical channel is the medium over which theinformation is carried.

    Logical Channel

    Logical channels consists of the information carried overthe Physical Channel.

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    LOGICAL CHANNELS

    0 1 2 3 4 5 6 7

    3

    57

    encrypted

    57

    encrypted

    26

    training

    1

    S

    1

    S

    3

    T

    8.25

    GP

    3

    T

    577S

    577S x 8 = 4.615mS

    TDMA Frame

    Normal Burst

    26 Frame Multi-frame

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    GSM Channels

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    Traffic Channel

    TCH carries payload data - speech, fax, data

    Connection may be:

    - Circuit Switched - voice or data or - Packet Switched data

    TCH may be:

    Full Rate (TCH/F)

    - one channel per user

    - 13 kb/s voice, 9.6 kb/s data or

    Half Rate (TCH/H)

    - one channel shared between two users

    Traffic Channels

    TCH/FFull rate 22.8kbits/s

    TCH/HHalf rate 11.4 kbits/s

    Time is divided into discrete

    periods called Timeslots

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    Control Channel

    DCCH(Dedicated Channels)Downlink & Uplink

    CCCH(Common Control Chan)Downlink & Uplink

    Synch.Channels

    RACHRandom

    Access Channel

    CBCHCell Broadcast

    Channel

    SDCCHStandalonededicated

    control channel

    ACCHAssociated

    Control Channels

    SACCHSlow associatedControl Channel

    FACCHFast AssociatedControl Channel

    PCH/AGCH

    Paging/Access grant

    FCCHFrequency

    Correction channel

    Control Channels

    BCH ( Broadcast channels )Downlink only

    BCCHBroadcast

    control channel

    SCHSynchronization

    channel

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    Common Control Channels (CCCH)

    CCCH contains all point to multi-point downlinkchannels (BTS to

    several MSs) and the uplinkRandom Access Channel:

    CBCH: Cell Broadcast Channel is an optional channel for general

    information such as road traffic reports sent in the form of SMS

    PCH: Paging Channel sends paging signal to inform mobile of a call

    RACH: Random Access Channel is sent by the MS to request a channel from

    the BTS or accept a handover to another BTS.

    A channel request is sent in response to a PCH message.

    AGCH: Access Grant Channel allocates a dedicated channel (SDCCH) to the

    mobile

    NCH:Notification Channel informs MS about incoming group or

    broadcast calls

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    Dedicated Control Channels (DCCH)

    SDCCH( Standalone Dedicated Control Channel )

    Uplink and Downlink

    Used for call setup, location update and SMS.

    SACCH( Slow Associated Control Channel )Used on Uplink and Downlink only in dedicated mode.

    Uplink SACCH messages - Measurement reports.

    Downlink SACCH messages - control info.

    FACCH( Fast Associated Control Channel )

    Uplink and Downlink.

    Associated with TCH only.

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    BURST

    The Time Slots are arranged in a sequence ,

    conventionally numbered 0 to 7.

    Each repetition of this sequence is called a TDMA

    Frame.

    The information content carried in one time slot iscalled a burst.

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    BURST Information

    Main Area where the Speech, Data or Control info is held

    Guard Period

    To enable the burst to hit the time slot (0.031ms)

    Stealing Flags

    2 bits are set when TCH is to stolen by a FACCH

    Training Sequence

    For estimation of transfer characteristics of physical media Tail Bits

    Used to indicate beginning and end of the burst.

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    GSM Burst & TDMA Frame

    0 1 2 3 4 5 6 7 2 4 5 6 730 1

    FRAME 1 FRAME 2

    Training Sequencenformation InformationGUARD

    PERIODGUARD

    PERIOD

    TAIL BITS TAIL BITS

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    Five Types of Burst Normal Burst

    Traffic & Control Channels Bi-directional

    Frequency Correction Burst

    FCCH Downlink Synchronization Burst

    SCH Downlink

    Dummy Burst

    BCCH Carrier Downlink

    Access Burst

    RACH Uplink

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    Call Scenarios

    Mobile to Mobile

    Intra-city

    Inter-city Mobile to Land

    Intra-city

    Inter-city

    Land to Mobile

    Intra-city

    Inter-city

    M bil T L d S

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    Mobile To Land Sequence

    1

    3

    CHANNEL REQUEST

    DCCH ASSIGN

    SIGNALLING LINK

    ESTABLISHED

    REQUEST FOR SERVICE

    SET CIPHER MODE

    SET-UP

    EQUIPMENT ID

    REQUEST

    AUTHENTICATION

    MS BSS MSC VLR HLR PSTNEIR

    RACH

    AGCH

    SDCCH

    SDCCH

    Call

    Info7

    4

    6

    5

    2 CR

    CC

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    8

    COMPLELTE CALL

    CALL PROCEEDING

    9 ASSIGNMENT COMMAND

    INITIAL & FINALADDRESS (IFAM)

    ASSIGNMENT COMPLETE

    (ACM)

    10

    ANSWER(ANS)11

    CONNECT ACKNOWLEDGE

    SDCCH

    SDCCH

    ASSIGNMENT COMPLELTE

    MS HEARS RINGTONE

    FROM LAND PHONE

    ALTERING

    RING TONE

    STOPS

    CONNECT

    (channel)

    (TCH)

    FACCH

    FACCH

    FACCH

    TCH

    (circuit)

    FAACH

    BILLING STARTS

    Hello!

    MS BSS MS

    C

    VLR HLR PSTN EIR

    Call Contt.

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    Supplementary Services Calling Line Identification

    Present

    Absent

    Connect Line Identification Present

    Absent

    Closed User Group - CUG

    Only incoming

    Only outgoing

    Operator Controlled Barring

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    Data Services

    Data rates supported as of today areData rates supported as of today are

    2.4 Kbps2.4 Kbps

    4.8 Kbps4.8 Kbps

    9.6 Kbps9.6 Kbps

    GPRS & EDGE implementation takes the dataGPRS & EDGE implementation takes the data

    capability to higher level of the order of 184capability to higher level of the order of 184

    kbps and morekbps and more

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    Customer..Expectation

    Good coverage where ever he goes

    Good quality

    No blocking

    Value added services SMS

    Voice mail

    MMS

    Call forward/call waiting

    Data/internet at high data rates

    prepaid

    Basic Network Design

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    Basic Network DesignObjectives

    The basic objectives of a wireless system are:

    COVERAGE: provide sufficient cell sites to deliver RF coverage ofthe entire desired area.

    BUILDING/VEHICLE PENETRATION: deliver sufficient signal levelsto adequately penetrate buildings and vehicles where

    appropriate. TRAFFIC: ensure that no cell captures more traffic than it can

    handle at the desired grade of service (i.e., blocking percentage)

    PERFORMANCE: design, construct, and adjust the network todeliver reliable service free from excessive origination and calldelivery failures, dropped calls, quality impairments, and service

    outages. ECONOMICS: provide return on investment sufficient to support

    operating and capital expenses, expand the network to takeadvantage of growth opportunities, and retire costs ofconstruction prior to depreciation of the network equipment.

    High Level Design

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    High Level Design

    Inputs

    Coverage objectives Area coverage objectives

    Coverage penetration objectives

    Morphology data/clutter information

    Terrain data and Vector maps

    Traffic objectives

    Number of subscribers defined

    Traffic per subscriber defined Desired grade of service defined

    City regulations

    BTS Hardware specifications

    Link Budget

    Business and Logistical objectives

    Capital budget

    Timing: launch data

    Operating revenue Vs. total costs

    Output

    Cell database and traffic model

    Composite coverage plot

    Equal power handoff boundaries plot

    Background Issues Impacting

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    Background Issues ImpactingSystem Design

    Site acquisition Availability of suitable candidate (building or land)

    Owner interest

    Cost of leasing

    Frequency clearance (SACFA)

    Government authority approval Space constraints and other construction issues

    Candidate Location line of sight to the objective

    Clutter type

    Terrain variations

    Physical Blocking buildings, hoardings

    Water

    Mumbai High end, high traffic areas are very close towater.

    Makes RF design much more challenging

    Deviation from desired location impacts surrounding

    site locations

    D i id ti f N t k

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    Design considerations of Network(GSM/CDMA)

    Understand geographical area as per license agreement

    Define coverage expectations in terms

    On road coverage

    In-building coverage (different penetration margins)

    Capacity considerations busy hour per subscriber call attempts andminutes of use (Erlangs)

    1 Erlang is 1 call of 1 hour duration

    Decide number of sites based on coverage capacity requirement

    Propagation tools used for this analysis

    Finalize exact site locations after field survey

    Initiate candidate identification process

    Site acquisition/antenna positioning

    Modify existing design if site location changes

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    Traffic &

    Growth

    Analysis

    System

    Optimisation

    Site Coverage

    Confirmation

    Site Search &

    Selection

    Propagationmodel

    verification

    System/SiteDimensioning

    RF &Network

    Planning

    Market

    Requirement

    Site Acquisition

    Site Build

    Operational

    Network

    Site Search

    Plan

    PerformanceMonitoring

    Flow Chart for Network Deployment

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    GSM Planning Steps Various steps are listed below

    CW survey

    Model Tuning

    Nominal Planning

    RF site Surveys

    Realized Planning

    Frequency Planning

    Implementation

    Optimization Drive Testing

    Performance Analysis

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    Nominal Planning

    It consists of planning a set of sites on planning

    tool so as to predict the coverage of the target area

    Tool needs to be made intelligent so as to predictthe coverage as close as possible to actual

    coverage

    Coverage plots are based on customer intension of

    providing indoor and outdoor coverage

    Mumbai Coverage

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    Mumbai CoverageExpectation Boundary

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    Coverage Maps Reverse Link.

    Colaba

    Malabar Hill

    Mazgaon

    >=30dB:: 3-4 wall coverage

    25-30dB : 3 Wall Coverage

    23-25 dB : 2-3 Wall Coverage

    18-23dB: 2-3 Wall Coverage

    16-18 dB : 2 Wall Coverage

    8-16dB : 1-2wall Coverage

    08 dB : On Road-1 Wall Coverage

    00 dB : On Road/No Coverage

    Indoor Coverage:

    Penetration Margin Legend

    Composite Coverage

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    Composite CoveragePlot

    Propagation models are used topredict coverage from a particularsite

    A composite coverage plot shows theoverall coverage produced by eachsector in the field of view

    The color of each pixel corresponds

    to the signal level of the strongestserver at that point

    Such plots are useful for identifyingcoverage holes and overall coverageextent

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    Clutter Types

    Clutter types

    Dense Urban

    Urban

    Sub Urban

    Rural

    Water

    Vegetation Industrial

    Forest

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    RF surveys

    Each nominal has a search ring defined by the RFPlanner

    Candidates needs to be identified as close as

    possible to the nominal within the search ring Height, orientations & antenna placement at site are

    the key RF parameter which are based upon thecoverage requirement in the area

    Major obstructions and clutter type in variousdirections to be observed on RF survey

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    RF surveys

    Equipment required for RF Survey GPS

    Digital Camera

    Binoculars Magnetic Compass

    There might be 3 or more candidates surveys forone site

    Each candidate would have an RF survey form andpanoramic associated with it

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    Drive Testing Drive testing is an important activity to get statistics & graphs oncoverage, quality & capacity in the downlink direction

    Drive test setup DT tool, Engineering Handset, GPS,

    accessories

    Call in 2 modesDedicated while the mobile is on call

    Idle while the mobile is idle

    Important parameters observed during drive testing

    Coverage Rx level (Full & Sub)

    Quality RxQual & SQI

    Handover, Dropped call, Neighbor list, TA

    Selecting and Tuning

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    g gPropagation Models

    Parameters of propagationmodels must be adjusted forbest fit to actual drive-testmeasured data in the areawhere the model is applied

    The figure at right shows drive-

    test signal strengths obtainedusing a test transmitter at anactual test site

    Tools automate the process ofcomparing the measured datawith its own predictions, and

    deriving error statistics Prediction model parameters

    then can be tuned tominimize observed error

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    Drive Test Screen

    What is Performance

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    What is PerformanceOptimization?

    The words performance optimization mean different things todifferent people, viewed from the perspective of their own jobs

    System Performance Optimization includes many different smallerprocesses at many points during a systems life

    recognizing and resolving system-design-related issues (cantbuild a crucial site, too much overlap/soft handoff, coverage

    holes, etc.) cluster testing and cell integration to ensure that new base

    station hardware works and that call processing is normal

    fine-tuning system parameters to wring out the best possiblecall performance

    identifying causes of specific problems and customer complaints,

    and fixing them carefully watching system traffic growth and the problems it

    causes - implementing short-term fixes to ease hot spots, andrecognizing problems before they become critical

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    Optimization

    Optimisation is an ongoing process of analysing network performance

    against Quality of Service targets:

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    Performance

    Measurements of network performance cover:

    Traffic in erlangs

    TCH and SDCCH Grade of Service (Congestion)

    Call success rate

    Handover failure

    Coverage area

    Coverage quality

    Subscriber base and growth

    Key Performance Indicators (KPI) are measurable dynamic

    parameters that help to target areas of concern

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    KPIs

    Appropriate KPIs to use depend on:

    The nature of the network

    Data sources available

    Measurement tools available

    Ability of engineering team

    Cost of network infrastructure

    Sources of data include:

    Surveyed data - from drive tests Network statistics - from OMC

    Field engineer reports

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    Radio Interface Optimization

    Transmission Timing

    Power Control

    VAD Voice Activity Detector and DTX

    Multipath Fading

    Equalization

    Diversity

    Frequency Hopping

    Antenna Parameters ( Height, Azimuth, Tilts )

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    Antenna Tilts

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    Antenna Tilts

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    BenchmarkingSurveyed data from test-mobile measurements can be used to

    benchmark system performance against that of a competitor

    Problems that may be identified from surveyed data:

    Poor coverage

    Unexpected interference

    Missing handover definitions

    Installation problems at BTS

    Test-mobile measurements should include:

    continuous calls to test coverage

    repetitive short calls to test call-success

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    Overview

    RF Planning Tool

    Drive Test Tool

    Optimization Tool

    MapInfo

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