Training Gsm Basic[1]

7/31/2019 Training Gsm Basic[1]

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GSM Foundation Course

Course Content Basic Telephony & Cellular

Principal of Cellular Communication

GSM Features

GSM Network ComponentsGSM Terrestrial Interfaces

Basic GSM Processes

GSM Air Interface

Radio Interface Optimization, Supplementary services &

Contemporary Networks


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ESSAR Telecom

Telecom Service Provisions GSM Basic Internet

ESSAR GSM Service Provider in Punjab, Delhi,

Rajasthan, U.P (East) & Haryana Basic Service Provider in the state of Punjab.


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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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ESSAR CELLPHONE

Punjab

Haryana

U.P (East)Rajasthan

Delhi

Coverage Area


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ORGANISATION STRUCTURE

PROMOTERS

TECHNICALPLANNING

IMPLEMENTATION

OPERATIONS

OPERATIONS SYSTEM SUPPORT

BILLING

IT

ACTIVATIONS

MARKETING

CUSTOMER CARESALES

SUPPORT FUNCTIONS

HR, ADMIN, ACCOUNTS


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Basic Telephony

Off HookDial Tone

Dialing Digits

RBT

Conversation

Ring

Off Hook &Conversation

SignalingTraffic

SWITCH / EXCHANGE


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2 Mb E1 (PCM)

Sample Rate 8 kHz8 bits per sample 64 kbps

1

31

16

0

300 - 3400 Hz

1 st TCH

17 th TS

30 th TCH

15 th TCH


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Wireless Telephony

BSC

BTS BTS

Mobile Subscriber...

MSC


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Wireless Communication

Alternative means of wireless communication

Walkie - Talkie Pagers Trunked private radios

Mobile Phone - the magic technology that enableseveryone to communicate anywhere with anybody.


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Cellular Communication

A cellular system links Mobile subscribers to PublicTelephone 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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WHAT IS CELLULAR TELEPHONY ?

CONSIDERATIONS -

FREQUENCY

SUBSCRIBERDENSITY

COVERAGE

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 regions 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 reality 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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The CELL

What is a cell ?

A cell is a certain areathat can be reachedwith one transceiver

or A small collection oftransceivers ondifferent channels at asingle base site.

The hexagonal-shaped communication cells areartificial & are generated to simplify the planning &design of a cellular network.

BTS


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Coverage & Capacity

Coverage Percentage of the geographical area covered

by cellular service where mobile telephony isavailable

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 thatusers will be denied access to a system due tothe simple unavailability of radio channels.


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Cells


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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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MICRO CELL

Below Rooftop ~ Railway Platforms, Airports,~ Busy Shopping Bazaar etc.

Low Tx Power~ 1 Watt max.

Limited Coverage~ 200m - 500m

Hotspot Solution

Special Algorithms for HO


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PICO CELLS

Pico Cell

Inside offices, Buildings

Very Low Tx Power~ Less than 1 Watt

Limited Coverage~ 50 -100m

Capacity Solution

Special Algorithms for HO


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Analog Mobile Telephony

End of 1980s Analog Systems unable tomeet continuing demands

Severely confined spectrum allocations

Interference in multipath fading environment

Incompatibility among various analog systems

Inability to substantially reduce the cost ofmobile terminals and infrastructure required


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Digital Mobile Telephony

Spectrum space - most limited and preciousresource

Solution - further multiplex traffic (time

domain)

Can be realized with Digital Techniques only.


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Different Standards Worldwide

Till 1982 Cellular Systems were exclusivelyAnalog 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 MHzband


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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 Recommendationsfrozen

1991 GSM Committee renamed Special MobileGroup and GSM renamed as GlobalSystem for Mobile Communication

1992 GSM is launched for commercial

operations


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GSM - IN CELLULAR TELEPHONY

Each Cell in the Cellular Network consists of oneor 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 a gap of 45 MHz in GSM of 75MHz in DCS.

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

Frequency Reuse is the solution


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Uplink-Downlink

Downlink = 935 to 960 MHz

Uplink = 890 to 915 MHz

BTS Tx MS Rx

BTS Rx MS Tx

dl

ul


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Frequency & ARFCN

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

Fdl(n) = F ul + 45 MHz

where n =ARFCN ; 1 n 124


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0 7

3

0

5

0 1

2

0 7

3

0

5

0 1 2

TDMA & FDMA

F D M A

200KHz

Uplink - MS Tx890MHz to 915MHz

Downlink - BTS Tx935MHz to 960MHz


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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 sequence Information Information

GUARD PERIOD GUARD PERIOD

TAIL BITS TAIL BITS


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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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Cell Dia = R

FREQUENCY RE - USE

Frequency Re-use

7/21 cell cluster

1

23

45

6

7

Two re-use distances

D D/R = (3N) 1/2

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 ofRadio Carriers.

Advantage

By frequent reuse of frequency morecapacity can be achieved .


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a1 a2

a3 a3

a4a6

a5

Cell Sectorisation

OMNI CELL

1 ANTENNA

b1

b2

b3

120 O CELLS

3 ANTENNAS

60 O CELLS

6 ANTENNAS


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3 Site Reuse Pattern

c2

c1c3

a1

a2

a3

b1

b2

b3

c1c2

c3Cell Re-use


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Cellular 1Planning Steps

Cellular Topology Cell splitting & Cell Repeat Patterns

3 cluster site 3/9 cell cluster 4 cluster site 4/12 cell cluster

Sites in the middle


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GSM Antennas

Directional Antennas Vertically Polarized.

Collinear Dipole Array with

8 to 12 elements. Beam Width 45 o, 60 o, 90 o.

High Gain Antennas with

gain of 16 to 18 dbi. Mechanically/Electrically

Downtiltable.


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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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Compatibility

With rapid Developments

there was a need for acommon Standard forMobile Communication.

With GSM, one coulddrive from Germany toSpain without a CallDrop.

Due to versatility of GSM,it was adopted by manycountries, even outsideEurope.


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Noise Robust

To combat the problems

due to Noise-Digital Interface is used .

Digital Interface

Protect these errorsusing Error Detection &Correction Techniques.

Immune to higher levels

of noise and interference Improvements in Quality

as well as Efficiency-Robust Air Interface.


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Increased Capacity and Flexibility

Analogue Air Interface

Every connection requires aseparate RF carrier and thusRF hardware.

System Expansion Time Consuming

Costly & Labor Intensive.

Intricate RF Planning.

Digital Interface

8 simultaneous conversationson one RF carrier.


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Standardized Open Interfaces

Low Price

Uses standard interfaces like C7, X.25 etc.

Versatility to choose equipment from different

manufacturer thereby reducing the pricingmonopoly.

Flexibility

Great flexibility in situating Networkcomponents because of Standard Interfaces.

Efficient use of terrestrial links.

f


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Better Security & Confidentiality

High Security risk for

Analogue System operators.

GSM

No Eavesdropping

High speech and data

confidentiality.

Digitized, Encoded and

Encrypted (A8 algorithm)

Subscriber Authentication

(A3 algorithm)

l d


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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

d


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Base Station 2

Base Station 3

Base Station 1

Handovers

ISDN C ibili


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ISDN Compatibility

ISDN (Integrated Services Digital Network)

Advanced Telecom Network designed to carry

voice and user data over the standard

telephones lines. 2B+D Signalling and information on ISDN line.

The GSM Network is designed to operate within

the ISDN System.

GSM provides features compatible with ISDN.


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GSM NETWORK ELEMENTS


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GSM NETWORK ELEMENTS

PSTNEC

MSC

HLR

AUCVLR

EIRIWF

TRAU BSC

BTS

Network Switching System

BSS

SIM

ME

MS

GSM N t k C t


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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. NETCOMP

M bil E i t (ME)


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Mobile Equipment (ME)

ME are of three types- Vehicle Mounted

Portable Mobile Unit Handportable Unit

MEs have distinct features -Classmarks sent in

initial message to Network.

NETCOMP

ME (Cl k I f ti )


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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 NETCOMP

M bil E i t


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TypicalSettings

Mobile Equipment

Class Power O/p

1 20 W

2 8 W

3 5 W

4 2 W

5 0.8 W

NETCOMP

SIM


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SIM

Subscriber Interface IdentityModule

The SIM stores

Subscriber Parameters

Personal Data for identifying

Subscriber to the Network.

IMSI,, MSISDN, PIN, PUK, Ki,A3, A8 (for Kc generation)

Space reserved for TMSI &

LAI

--------------

--------------

Small SIM

Full Size SIM Card

----------------------------

NETCOMP

SIM Internal Structure


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SIM - Internal Structure

CPU

EEPROM

RAM

ROM

I/O8

User Data 16 kB

Basic Operating Syste16 to 24 kB

Working Area for CP256 to 512 bytes

NETCOMP

SIM(IMSI)


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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

MCC (3) MNC (2) MSIC (10)

NETCOMP

SIM (LAI)


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LAI (Location Area Identity)

MCC 3 digit number (BCD), two Octets ( A & B)

MNC 2 digit number (BCD), one Octet LAC 3 digit number (Binary) , two Octets

0-65535

CI 5 digit number (Binary) , two Octets0-65535

SIM (LAI)

LACMCC MNC CI

NETCOMP

SIM


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SIM

MSISDN

10 digit number to which a subscriber is beingcalled.

PIN (Personal Identification Number) Four digit PIN An internal security to Protect the SIM from

illegal use. Card blocks itself after three wrong entries

PUK (Personal Unblocking Key) 8 digit code to unblock the SIM Card

Ki (Authentication Key), A3 & A8 AlgorithmsNETCOMP

SIM (TMSI)


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SIM (TMSI)

Temporary Mobile Subscriber Identity

Periodically changed by the SystemManagement on instances like location updateetc.

Reason for use of TMSI

To prevent a possible intruder from identifyingGSM users, TMSI is used

Management

Assignment, Administration & Updating isperformed by VLR.

NETCOMP

Transcoder


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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 120GSM - specified voice channels.

NETCOMP

Transcoder


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Transcoder

MSC BSS

XCDR120 GSM TCH

1 2 3 4

Transcoder Information from FOUR calls (4x16 KBPS put into ONE 64 KBPS timeslot

30 Channel PCM1234

NETCOMP


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Base Station System (BSS)


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BSS (Base Station System) BSC (Base Site Controller) BTS (Base Transceiver Station)

XCDR (Transcoder)

NetworkSwitchingSystem(NSS)

XCDR

BSC

BTSNETCOMP

BTS



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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

NETCOMP

BTS

A BTS Cabinet


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A BTS Cabinet

OUTER VIEW INNER VIEW NETCOMP

BSS Configuration


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BSS Configuration

Collocated BTS

Remote BTS

Daisy Chain BTS

Star Configuration

Loop Configuration

NETCOMP

BTS

Daisy Chain Configuration


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Daisy Chain Configuration

BSC

BTS

BTS

BTS NETCOMP

A l l B T

S on1 E 1

Star Configuration


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Star Configuration

BSC

BTS

BTS BTS

BTS

NETCOMP

Loop Configuration


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Loop Configuration

BSC

BTS

BTS BTS

BTS

Loop Configuration

NETCOMP

Network Switching System(NSS)


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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)

NETCOMP

MSC

MOBILE SWITCHING CENTRE


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MOBILE SWITCHING CENTRE

NETCOMP

GSM Network Component


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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.

NETCOMP

Home Location Register (HLR)


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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

MSRNNETCOMP

Visitor Location Register (VLR)


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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)

NETCOMP

Equipment Identity Register (EIR)


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qu p e t de t ty eg ste ( )

Contains Database for validating IMEI

White List (valid ME)

Black List (Stolen ME)

Grey List (Faulty ME)

NETCOMP

Inter Working Function


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Provides function to enable the GSM

System to interface with Public/PrivateData 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

g

NETCOMP

Echo Canceller


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Echo is apparent only in Mobile - Land

conversation & is generated at the 2 wire to 4 wireinterface.

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

NETCOMP

Operation & Maintenance Centre


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p

Event & Alarm Management

Fault Management

Performance Management Configuration Management

Security Management

Operation & Maintenance Centre


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o The OMC has access to the (G)MSC, BSC.o Handles error messages being reported from the

Networko Controls the traffic load of the BSC, and the BTS.

p

NETWORK MANAGEMENT CENTRE


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o NETWORK MANAGEMENT CENTRE (NMC) Offers Hierarchical Regionalised Network

Management of a complete GSM system.

Functionality of the NMC Monitors Nodes on the Network

Monitors Network Element Statistics

Monitors OMC regions & provides

information to OMC staff Enables Long Term Planning for

entire Network

MMI RAM>MMI RAM>MMI RAM>

NETWORK MANAGEMENT CENTRE


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NMC

OMC OMC

OMC

REGION 2 REGION 3

REGION 1

NETWORK

GSM Terrestrial Interfaces


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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

GSM Interfaces


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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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Basic Processes


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AUTHENTICATION

CIPHERING

REGISTRATION

CALL ESTABLISHMENT

HANDOVER / HANDOFF

ROAMING

AUTHENTICATION ALGORITHM


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NSS

MS

HLR

AUC

AUTH.ALGORITHMS

A3

SIM

MS

AUTH.ALGORITHMS

A3

Ki

RAND

RAND

COMPARE

SRES

SRES

Ki

AIR INTERFACE

Ciphering


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Data protection is required on air interface.

A5 algorithm is used. A specific key called Ciphering Key (Kc) , is

generated from RAND and A8 algorithm . A8 is on the SIM.

A8

RANDKi

Kc

Ciphering


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A5Data

Kc

Ciphered

Data A5

Kc

Data

ROAMING


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MSC

ME

ME

PSTN

MSC

VLR

HLR

INDIA

UK

ROAMING


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o The mobile roams to another country (UK) and requests a

Location Update when switched ON.o The VLR (UK) informs the home HLR (India) of the mobiles

new location (UK).

o The HLR updates its location information and sends the

subscriber information to the VLR (UK). o The HLR requests the subscriber information be removed

from the VLR (India).

o The VLR (India) acknowledges, and removes the subscriber

information from its database.

o After the mobiles registration is completed in UKs

MSC/VLR, the mobile is able to use network services (MOC,

MTC etc.)

Transmission Media


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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)

Access Microwave ( 15 GHz)


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14.250 to 14.500 MHz and14.400 to 15.350 MHz

4 QAM & 16 QAM Modulation

Split Mount Version with Hot

Standby Facility Bandwidth ranging from 1.25

MHz to 28 MHz dependingupon Data Rate andModulation type

4 E1 Radio with 3 spotfrequencies in our case

Backbone Microwave (7 GHz)


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7.125 to 7.850 MHz and 7.725

to 8.500 MHz 4 QAM & 16 QAM Modulation

Split Mount Version with hot

standby facility Bandwidth ranging from 1.25

MHz to 28 MHz dependingupon Data Rate and

Modulation type 16 E1 Radio with 1 spot

frequencies in our case

Optical Fiber


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Low Losses 0.5 dB/km & High Data Rates

Types of Fiber Step Index Graded Index

# Graded Index are better.Modes of Light in fiber

Mono Mode

Multi Mode# Mono Mode has less losses than Multi

Mode.

Optical Fiber


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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 beenthe best but fabrication not possible

140 Mbps OLTE , Mono Mode Step Index in our case


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Channels On Air Interface


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Physical Channel

Logical Channel

Physical Channel

Physical channel is the medium over which theinformation is carried.

Logical Channel

Logical channels consists of the informationcarried over the Physical Channel.

TDMA & FDMA


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0 7

3

0

5

0 1

2

0 7

3

0

5

0 1 2

F D M A 200KHz

Uplink - MS Tx 890MHz to 915MHz

Downlink - BTS Tx935MHz to 960MHz

LOGICAL CHANNELS


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0 1 2 3 4 5 6 7

3

57encrypted

57encrypted

26training

1S

1S

3T

8.25GP

3T

577 S

577 S x 8 = 4.615mS

TDMA Frame

Normal Burst

26 Frame Multi-frame

BURST


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Time is divided into discrete periods

called Timeslots

The Time Slots are arranged in a sequence, conventionally numbered 0 to 7.

Each repetition of this sequence is calleda TDMA Frame.

The information content carried in onetime slot is called a burst.

BURST


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Information

Main Area where the Speech, Data or Control infois 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.

Five Types of Burst


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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

GSM Logical Channels


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TCH SACCH

FACCH

Control Channels BCCH

CCCH

ACCH

DCCH

LOGICAL CHANNELS


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TDMA Frame

26 Frame Multi-frame

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

Frames & Multiframes


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Several Logical channels share one time slot.

Individual channels are sequenced, & each

channel gets the time it requires.

Sequence is carried out using Multiframes. Traffic Channel occupy a 26-frame multiframe

(120 ms )

Control Channel occupy a 51-frame multiframe

(235 ms).

Traffic Channels - TCH


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TCH

TCH

TCH / FS 9.6

DATA

TCH / HS

4.8

2.4

FACCHSAACH

BCCH Channel


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CCH

BCCH

BCCHSynchronizing Channels

FCH SCH

Broadcast ControlChannel - Downlink only



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BCCH Transmitted at all times & conveys information

about Cell Timing and Configuration

BCCH, FCCH, SCH

CCCH Used by BSS & MS when trying to initiate a

connection over the air

RACH, PCH, AGCH, CBCH



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DCCH Used to convey signaling information during

call setup

SDCCH

ACCH Used to transmit signaling information when a

call is in progress

FACCH & SACCH



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ACCH SAACH

Conveys Power Control & TimingInformation in the downlink direction.

RSSI and Quality reports in the uplinkdirection.

FACCH

To carry out user authentication andhandovers. It steals the TCH burst andinserts its own information.



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Acronyms

BCCH Broadcast Control Channel

CCCH Common Control Channel

DCCH Dedicated Control Channel

ACCH Associated Control Channel

SDCCH Standalone Dedicated Control Channel

RACH Random Access Channel

PCH Paging Channel

AGCH Access Grant Channel



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BCCH Location Area Identity List of neighbouring cells, to be monitored

List of frequencies used in the cell

Cell Identity Power Control Indicator

DTX permitted

Access Control (e.g emergency calls, callbarring)



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Always transmitted at constant power at all

times Dummy burst are sent to ensure continuity

when no traffic information is sent.

FCCH Mobile corrects the frequency of its internal

time base by reading this logical channel.

Easily detected by the mobile.

After FCCH, mobile is able to detect SCHwhich contains timing information.



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SCH Carries the information for mobile to

synchronize to the TDMA frame structure &know the timing of the individual timeslots.

Frame Number & BSIC (Base Station IdentityCode)

CCCH

RACH Transmitted by the Mobile when it wishes to

gain access to the system



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PCH

Transmitted by the BTS when it wishes tocontact a specific mobile.

AGCH

Transmitted by the BTS to assign dedicatedresources to an MS such as SDCCH

CBCH

To transmit messages to all mobiles withina cell. CBCH will steal some time of anSDCCH to do this.

Channel Combinations


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Full rate Traffic Channel Combination

TCH8/FACCH + SACCH

Broadcast Channel Combination

BCCH + CCCH

Dedicated Channel Combination

SDCCH8 + SACCH8

Combined Channel Combination BCCH + CCCH + SDCCH4 + SACCH4

Channel Combinations (Timeslots)


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Traffic Channel Combination

TCH8/FACCH +SACCH Can be on any Time slot

Broadcast Channel Combination BCCH +CCCH

Can be on Timeslot 0, 2, 4, 6

Dedicated Channel Combination SDCCH8 + SACCH8 Any Time slot

Combined Channel Combination BCCH + CCCH +SDCCH4 + SACCH4 Can only be on 0 Timeslot

TCH Multiframe


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120

0 5 10

SACCH

15 20

IDLE

Downlink & Uplink SACCH

BCCH/CCCH Multiframe


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121

BCCH/CCCH

In Downlink direction the timeslot (physicalchannel) is shared by a different logicalchannels.

In the Uplink direction all timeslots areallocated to RACH.

BCCH/CCCH Multiframe


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122

10 20 30 40 50

Downlink to MS

Uplink from MS

0 10 20 30 40 50

F S F S F S F S S I FCCCH8 TS

CCCH4 TS

BCCH CCCH8 TS

CCCH8 TS

CCCH8 TS

R R R RR R R R R R R R R R R R R R R R R R R R R R RR R R R RR R R R R R R R RR R R RR R R RRR

0

Combined Multiframe


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123

BCCH and SDCCH share a common timeslot

Less No. of subscribers support (as only 4SDCCH)

102 frame structure

Superframes And Hyperframes

1326 TDMA frames (26*51) make asuperframe

2048 superframes make one hyperframe,after which ciphering and frequency

hopping algorithm are restarted.

Combined Multiframe


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124

0 10 20 30 40 50

F

F

S

S

BCCH F

F

S

S F S F S

S

S A2

A0 A1

A3

I

I

F

FCCCH8 TS

F S F SCCCH8 TS

CCCH

4 TS

CCCH

4 TS

BCCH D2

D2 D3

D3

D0 D1

D0 D1

0 10 20 30 40

D3 R

R

R

R A2 A3D3

A0 A1 R

R

R

R D2

D2 R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

D0 D1

D1D0

50

Downlink to MS

Uplink from MS

SDCCH Multiframe


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125

0 10 20 30 40 50

I

I

Downlink to MS

Uplink from MS

I

I

I

I

D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A3

D0 D1 D2 D3 D4 D5 D6 D7 A4 A5 A6 A7

0 10 20 30 40 50

I

I

I

I

I

I

D0 D1 D2 D3 D4 D5 D6 D7 A1 A2 A3 A0

D0 D1 D2 D3 D4 D5 D6 D7 A5 A6 A7 A4

Voice Coding


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126

Block - 1 : 1, 5, 9 .. Samples

Block - 2 : 2, 6, 10, Samples

& so on for Block - 3 & Block - 4.

LPC

RPE

D i vi d

e d i n t o4 B l o

ck

s

of 4

0 S am pl e

s e a ch

LTP

Class Ia Class Ib Class II

50 bits 132 bits 78 bits

20 mS Sample Rate 8 kHz

13 bits per Sample 160 Samples

2080 bits

104 kbps

Reduction in Data Speech Encoder selects Blockwith Most Energy

Channel Coding


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127

Error Protection And Detection

To protect the logical channel fromtransmission errors by the radio path, differentcoding schemes are used.

Coding & Interleaving Schemes dependent uponlogical channel to be encoded.

3 Coding Protection schemes Speech Channel Encoding

Control Channel Encoding Data Channel Encoding

Speech Channel Coding


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128

Speech Information of 20 ms block is divided

over 8 GSM burst.

260 bits are grouped in three classes depending

upon the intelligible part of speech

After encoding 456 bits block is interleaved

Speech Channel Coding


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129

ParityCheck

456 bits

Class 1b132 bits

Class 1a50 bits

Class 278 bits

50 1323 4

Convolutional Code

378 78

Tail Bits

378 78

Convolutional Coding

Control Channel Encoding


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130

Control Channel Encoding

Block of 184 bits received by BTS Bits are protected by Cyclic Codes of Class

Fire Codes Adds 40 Parity Bits

4 Tail Bits are added Convolution Coding is done

O/p from 184 Signalling bits is 456 bits.

Control Channel Coding


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131

184

Coding

184 40Parity Bits


456

456 bits

4TB

Data Channel Coding


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132

240

184


488

4

Punctuate

456

Interleaving


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133

Responsible for Robustness of the GSM air

interface 10 -20 % burst destroyed or corrupted on the air

interface.

Spreads the content of one information block

across several TDMA timeslots. Two types of Interleaving -

Diagonal Interleaving

Rectangular Interleaving

DIAGONAL INTERLEAVINGSPEECH


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134

Speech Blocks

456 bits

EIGHT blocks of 57 bits,

Sent on 8 ALTERNATE timeslots

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

456 bits

RECTANGULAR INTERLEAVINGCONTROL CHANNEL


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135

Data Blocks

456 bits

114Bits

Odd

114

BitsOdd

114

BitsEven

114

BitsEven

FOUR blocks of 114 bits,Sent on 4 timeslots

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

Interleaving


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136

Interleaving Depths

Speech - 8 blocks Control - 4 blocks Data - 22 blocks

Speech & Data blocks are diagonally interleaved

Control block is rectagularly interleaved

Interleaving


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137

TRAU Frame Type

Data

Control

Speech

Number of GSMBurst Spread Over

22

4

8

TRAU = Transcoder Rate Adaption Unit


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138


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139

MOBILE TO LAND


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140

MSC

BSC

BTS

PSTN

Multiple Point of Interconnect


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141

BSS TRAFIC POI TRAFIC

CITY A

CITY B

Call Scenarios


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142

Mobile to Mobile

Intra-city Inter-city

Mobile to Land

Intra-city Inter-city

Land to Mobile

Intra-city

Inter-city

Mobile To Land Sequence


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143

1

3

CHANNEL REQUEST

DCCH ASSIGN

SIGNALLING LINKESTABLISHED

REQUEST FOR SERVICE

SET CIPHER MODE

SET-UP

EQUIPMENT IDREQUEST

AUTHENTICATION

MS BSS MSC VLR HLR PSTN EIRRACH

AGCH

SDCCH

SDCCH

Call Info 7

4

6

5

2CR

CC

8 COMPLELTE CALL

CALL PROCEEDINGSDCCH

SDCCH ( i it)

MS BSS MSC VLR HLR PSTN EIR


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144

9 ASSIGNMENT COMMAND

INITIAL & FINAL ADDRESS(IFAM)

ASSIGNMENT COMPLETE(ACM)

10

ANSWER(ANS)

11

CONNECT ACKNOWLEDGE

SDCCH

ASSIGNMENT COMPLELTE

MS HEARS RINGTONEFROM LAND PHONE

ALTERING

RING TONESTOPS

CONNECT

(channel)

(TCH)

FACCH

FACCH

FACCH

TCH

(circuit)

FAACH

BILLING STARTS

Hello!

Land to Mobile SequenceInitial & Final Address Msg.

(IFAM) MSISDN

MS BSS MSC VLR HLR GMSC PST


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145

(IFAM)

Send Routing Information

Routing Information Ack

INITIAL & FINAL ADDRESS(IFAM)

Send Info for I/c Call Setup

Channel Request

Signalling Link Established

MSISDN

Paging Request

PAGE

DCCH Assign

PCH

AGCH

SDCCH

IMSI MSISDN

MSRN

MSRN

MSRN

TMSI

LAI &TMSI

TMSIRACH

Page ResponseSDCCH

TMSI

TMSI &

status

Status

Land to Mobile SequenceComplete Call

MS BSS MSC VLR HLR GMSC PST


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146

SETUP

CALL Confirmation

ADDRESS COMPLETE

Assignment Command

Ring Toneat MS

Alert

Assignment Complete

Connect

TMSI

SDCCH

SDCCH

TCH

FACCH

Connect ACK

Channel Circuit

FACCH

SubscriberPicks Up

FACCH

ANSWER TCH

BILLING STARTSFACCH

Ringing Stops atLand Phone

RingTone atLand Phone

Hello

Mobile Initiated Call Clearing

MS BSS MSC VLR HLR PSTN FACCH


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147

1 DISCONNECT

PSTN RELEASEMOBILE RELEASE

2 PSTN RELEASECOMPLETE

FACCH

FACCH

MOBILE RELEASE

COMPLETE

3 CLEAR COMMAND

CHANNEL RELEASE

5 RLSD

4UA

CLEAR COMPLETE

DISC

RELEASE COMPLETE

FACCH

FACCH

MS -MSC SignallingReleased

FACCH

FACCH

Inter-BSS Handover Sequence


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148

1

3

Periodic MeasurementReports

Handover Required

Handover Request

Handover Req Ack

Information Interchange

Handover Complete

Clear Command

Handover Command

MS BSS BSS MSC HLR PSTN

SAACH

7

4

6

5

2 TMSI Cct.Code

HO ref No.

HO Ref No.

FACCH

FACCH

Periodic MeasurementsReports

SAACH

8

9


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149

Radio Interface Optimization


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150

Transmission Timing

Power Control

VAD and DTX

Multipath Fading

Equalization Diversity

Frequency Hopping

THREE TIMESLOT OFFSET


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151

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

Mobile Rx

Mobile Tx3 TS Offset

TIMING ADVANCE


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152

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 0 1 2 3 4 5

BURST arrivesLATE

BURST arrivesIN TIME

BURST sent early

T = 3.69 S to 233 S

Cell Radius = 35km

Power Control


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153

Cell Radius = 35km

In steps of 2dB

Enhances Battery Life

Reduces Interference

13 dBm (min)

33 dBm (max)

Dis-Continuos Transmission


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154

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

VAD - Voice Activity Detection MS identifies presence/ absence of speech

Generates Comfort noise

DTX - Dis-Continuous TransmissionMS does not TX during silence period

MULTI-PATH PROPAGATION


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155

DIVERSITY


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156

Approx. 10 Wavelengths 3.3 meters

Diversity Receiver

FREQUENCY HOPPING


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157

F0

F2

F3

F4

FN

F1

T I M E

F R E Q U E N C Y

FREQUENCY HOPPINGMobile Activity


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158

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

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

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

Mobile Rx

MONITORING Other Cell

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

Mobile Tx

Rx 1

Rx 2

Tx1

Tx2


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159

Speech Services

Telephony (13 kbps full rate)


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160

Telephony (13 kbps full rate)

Emergency Call (with/without SIM card in theMobile Station)

Short Message Services (SMS)

Point to Point (128 Byte Max.)

Cell Broadcast(75 bytes Max.)

Dual Personal and Business Numbers.

Allows calls to be made and billed, either tobusiness or personal numbers.

Data Services (Bearer Services)

D t t t d f t d


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161

Data rates supported as of today are

2.4 Kbps

4.8 Kbps

9.6 Kbps

Supplementary Service - Call Waiting


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162

Call in Progress

PSTN Phone

Supplementary Services - Call Hold


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163

1. Call in Progress2. Put on Hold

3. Calls another Mobile

Supplementary Services -Call Forwarding


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164

Incoming

Call

Voice Mail

System

PSTNPhone

AnotherMobile

Divert ifAll Calls

Busy

Not Reachable

No Answer

Supplementary Services

Calling Line Identification


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165

Calling Line Identification Present Absent

Connect Line Identification

Present

Absent Closed User Group - CUG

Only incoming

Only outgoing Operator Controlled Barring

Voice Mail System


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166

ANSWERING MACHINE

Voice Mail System


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167

MSC

Short Message Service


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168

SMSC

MSC

BTS

Short Message Service


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169

SMSC

MSC

BTS

Point to Multipoint

Point to Point

PRE - PAID SYSTEM

SIM BASED


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170

Data on SIM Decrements with use Over the air charging !!??

NETWORK BASED

Data secure on with the network Over the air re-charging Features

Inquiry Warnings ..


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171

SEPARATE GSM & WLL INFRASTRUCTER


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172

DUAL BAND / MODEHANDEST

MSC GSM BSC

GSM BTS

PSTN FIXED LINE SWITCH CDMA BSC

CDMA BTS

CDMA BTS

GSM BTS

SEPARATE GSM & WLL INFRASTRUCTER


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173

GSM + CDMA

GSM GSM

CDMA

Call Drop.Toggle to GSM

Still on GSM.Toggle to WLL

GSM

On WLL


GSMCoverage

CDMACoverage

Every individual is a WLL subscriberunder any and only one CDMA BTSand is a regular subscriber for the restof the GSM network in the whole ofPunjab.The subscriber also has the advantageof roaming within & outside thecountry.

COMMON GSM & CDMA INFRASTRUCTER

A - INTERFACE


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174


MSC

GSM BSCGSM BTS

PSTN

CDMA BSC CDMA BTS

A - INTERFACE

A - INTERFACE

IRRIDIUM

BTS in the Sky


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175

LEO ~1400km Inter Satellite Links - 22.55GHz to 23.55GHz L-Band (1616MHz to 1626.5 MHz) Band Width - 10.5MHz

Use TDM/FDMA scheme World-Wide Coverage

60+ Now Operational Small Hand held terminals Dual Mobiles under development


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Documents

Training Gsm Basic[1]