gsm+overview 1

8/2/2019 Gsm+Overview 1

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Global System

for Mobiles

GSM


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TOPICS

GSM CONCEPTS

GSM SYSTEM ARCHITECTURE

IDENTITIES USED IN GSM GSM CHANNELS

GSM RADIO LINK

MOBILITY MANAGEMENT CALL MANAGEMENT

RADIO RESOURCE MANAGEMENT


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3

TOPICS

GSM CONCEPTS



GSM RADIO LINK

MOBILITY MANAGEMENT CALL MANAGEMENT



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5

Background to GSM

1G : Advanced Mobile Phone Service (AMPS) Analog, Circuit Switched, FDMA, FDD

2G : Digital Advanced Mobile Phone Service (D-AMPS)

Digital, Circuit Switched, FDMA, FDD 2G : Global System for Mobile (GSM)

Digital, Circuit Switched, FDMA and TDMA, FDD

2G : Code Division Multiple Access (CDMA) Digital, Circuit Switched, FDMA, SS, FDD


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GSM History


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1982: Groupe Spcial Mobile (GSM)created

1984: Description of GSM features

1985: List of recommendations settled

1987: Initial MoU (Memorandum ofUnderstanding) aside the draftingof technical specifications wassigned by network operators of 13countries:

1988: Validation and trials, of the radio

interface.

1991: First system trials aredemonstrated at the Telecom 91exhibition.

1992: Official commercial launch ofGSM service in Europe. First

Launch in Finland

1993: The GSM-MoU has 62signatories in 39 countriesworldwide.

1995: Specifications of GSM phase 2are frozen.

1999: GSM MoU joins 3GPP (UMTS)GPRS Trials begins

2000: 480M GSM subscribersWorldwideFirst GPRS Networks roll out

End 2002: 792M GSM subscribersWorldwide

Development of the GSM Standard


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12 SERIES

OPERATION ANDMAINTENANCE

01 SERIES

GENERAL 02 SERIESSERVICE ASPECTS

03 SERIES

NETWORK ASPECTS

04 SERIESMS-BSS INTERFACE AND

PROTOCOLS

05 SERIES

PHYSICAL LAYER ON THERADIO PATH.

06 SERIESSPEECH CODINGSPECIFICATIONS

07 SERIESTERMINAL ADAPTERSFOR MOBILE STATIONS

11 SERIESEQUIPMENT AND TYPE

APPROVAL SPECIFICATIONS

10 SERIESSERVICE INTERWORKING

09 SERIESNETWORK

INTERWORKING

08 SERIES

BSS TO MSC INTERFACES

GSM Specifications


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Increasing GSM Data Rates

TransmissionTimeGPRS = GeneralPacketRadioServiceHSCSD=HighSpeedCircuit SwitchedDataEDGE=Enhanced Data rate for GSM EvolutionUMTS = Universal Mobile Telecommunication System

10 sec 1 min 10 min 1 hour0

UMTS

E/GPRS

ISDN

PSTN

GSM

webe-mail photo

web photoe-mail

web photo

video

clipreportphoto

web photoe-mail

videoclipreport

video

clipreport

videoclipreport

video

clipreport


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10

throughputkbps

10 k

100 k64 k

1 M

2 M

1 k 1998 1999 2000 2001 2002

Time frame

UMTS

GPRS

HSCSD

9.614.4

GPRS=GeneralPacketRadioServiceHSCSD=HighSpeedCircuit SwitchedDataEDGE=Enhanced Data rate for GSM EvolutionUMTS = Universal Mobile Telecommunication System

EDGE

Wireless Data Technology Options


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11

Circuit mode

Packet mode

AFDHCG

CG

CGCG

CG

DH

DH

AFDH

DH

AF

AF

AF

A

B

C

D

E

F

G

H

Circuit-Switched or Packet-Switched


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Multiple Access Technique

Multiple Access Achieved by dividing the availableradio frequency spectrum, so that multiple users canbe given access at the same time.

FDMA - Frequency Division Multiple Access

( eg: GSM each Frequency channel is 200KHz)

TDMA - Time Division Multiple Access

( eg: GSM each frequency channel is divided into8 timeslots)

CDMA - Code Division Multiple Access

(eg: IS95- Each User data is coded with a unique

code)


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Duplex Technique

Duplex - How the up link and Down link of a useris separated

FDD - Frequency Division Duplex

(eg:In GSM the up link and down link of a user isseparated by 45MHz )

TDD - Time Division Duplex

(the up link and down link of a user will be at the same

frequency but at different Time )


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What are the types in

GSM Network?

GSM-900 (Channels 125 operating band 900Mhz

carrier spacing 200khz spacing 45Mhz)

GSM -1800 (Channels 374 spacing 95Mhz)

GSM -1900(Used in USA)


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GSM Band Allocations (MHz)

Carrier frequency = ARFCN =Absolute Radio Frequency Channel Number

Frequencies are in MHz

GSM systems Uplink Downlink Band DuplexSpacing DuplexchannelsGSM 450GSM 480GSM 850

450.4-457.6478.8-486824-849

460.4-467.6488.8-496869-894

2x7.22x7.22x25

101045

3535124

GSM 900E-GSM (900)R-GSM (900)

890-915880-915876-880

935-960925-960921-925

2x252x352x04

454541

12417440

GSM 1800GSM 1900 1710-17851850-1910 1805-18801930-1990 2x752x60 9580 374299

GSM F il R di B d S


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GSM Family Radio Band Spectrum

Uplink

Downlink

880 890 915 1710 1785

925 935 960 1805 1880MHz

P-GSM

GSM 1800 GSM 1900

1850 1910

1930 1990

R-GSM

876

921

960

960

915

915

E-GSM

Uplink

Downlink

824 849

869 894 MHz

GSM 850

478.8 486

488.8 496

450.4 457.6

460.4 467.6

GSM 450 GSM 480


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Traffic/Signaling

Signaling

bla bla bla...

RING !

riiiiing

Network

Traffic


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AuC

MS

MS

BTS

BTS

BTS

BSC

BSC

MSC

MSC

VLR

VLR

GMSC

HLR

PSTN

EIR

Um

Abis

Abis

A

A

OMC Server

Um

GSM - Network Structure

B

E

E

X.25

C

F

H

X.25


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Frequency bandUplink 890 - 915 MHzDownlink 935 - 960MHz

Duplex Frequency Spacing 45MHz

Carrier separation 200KHzFrequency Channels 124Time Slots /Frame(Full Rate) 8Voice Coder Bit Rate 13Kbps

Modulation GMSKAir transmission rate 270.833333 KbpsAccess method FDMA/TDMASpeech Coder RPE-LTP-LPC

GSM System specifications


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890 MHz 915 MHz 935 MHz 960 MHz

Uplink Downlink

Example:

Channel 48

0 124channel # 0 124channel #

Frequency Frequency

Duplex spacing = 45 MHzFrequency band spectrum = 2 x 25 MHzChannel spacing = 200 kHz

BTS

Paired Radio Channels in GSM

Case of GSM 900

GS


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GSM Time Division MultiplexFrame and Physical Channels

TS TS TS TS TS TS TS TS

0 1 2 3 4 5 6 7

Time4.615 ms

TDMA frame

Physical channel # 2 = recurrence of time-slot # 2

TDMA frame

0 9.23 ms

Time-slot

(frames repeat continuously)

TS TS TS TS TS TS TS TS

0 1 2 3 4 5 6 7


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Physical Channel

MS3

//ARFCN1 2 124FDMA

BTSWithout FH

0

TDMAs

TS7

n

n-1

n+1

MS2

MS1

timeBTSWith FH


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Radio Link Aspects

From Speech to RF SignalBlah Blah Blah...Blah... Blah... Blah...

Digitizing andSource Coding

Channel Coding

Interleaving

Ciphering

Burst Formatting

Modulating Demodulating

Burst De-formatting

Deciphering

De-interleaving

Channel Decoding

Source Decoding


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Uplink 890 MHz to 915 MHzDown Link 935 MHz to 960 MHz

25 MHz divided into 125 channels of 200 KHzbandwidth

890.0 890.2 890.4 914.8 915.0

935.0 935.2 935.4 959.8 960.0

UP

DOWN

Access Techniques


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Time Division Multiple AccessEach carrier frequency subdivided in time domaininto 8 time slots

Each mobile transmits data in a frequency, in itsparticular time slot - Burst period = 0.577 milli secs.8 time slots called a TDMA frame. Period is .577 * 8= 4.616 milli secs

0 1 2 3 4 5 6 7

4.616 ms

0.577 ms

Access Techniques ...


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Fundamentals


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GSM utilizes two bands of 25 MHz. 890-915MHz band is used for uplink while the 935-960 MHz is used for downlink.

The frequency bands are divided into 200KHz wide channels called ARFCNs (AbsoluteRadio Frequency Channel Numbers) i.e.there are 125 ARFCNs out of which only 124are used.

Each ARFCN supports 8 users with each usertransmitting / receiving on a particular time

slot (TS).

Fundamentals

124

123

.

2

1

124

123

.

2

1

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

Data burst = 156.25 bit periods = 576.9s

960 MHz

959.8MHz

200KHz

935 MHz

935.2 Mhz

915 MHz

200KHz

45 MHz

Downlink (TDMA frame) = 8 TS

Uplink (TDMA frame)

Delay

TS: Time slot

914.8 MHz

890.2 MHz

890 MHz

DOWNLINK

UPLINK

Therefore 1 TDMA frame = 156.25 x 8 = 1250 bits

and has a duration of 576.92s x 8 = 4.615 msThe technology


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GSM Delays Uplink TDMA Frames

Downlink TDMA

T T T T T T T T

R TMS1

R TMS2

Downlink

Uplink

Fixed transmitdelay of three

time-slots

R R R R R R R R

0 1 2 3 4 5 6 7

The start of the uplink TDMAis delayed of three time-slots

BTS side

MSs side

BTS

TDMA Frame (4.615 ms)


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Timing Advance

1 - Propagation Delay

M2 M1d1>>d2d2

BTS Frame reference

MSs transmit

Propagation Delay tp

TS0 TS1 TS2 TS3 TS4 TS6TS5 TS7

Bits Overlapping

Timing Advance


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TX BTS CAN WHAT GSM HOW WHEN WHAT

RX BTS yes the ms-isdn

RX MS1 CAN

TX MS1 yes

RX MS2 WHAT

TX MS2 the

RX MS3 GSM

TX MS3 ms-isdn

RX MS4 HOW

TX MS4

RX MS5 WHEN

TX MS5

RX MS6 WHATTX MS6

RX MS7

TX MS7

RX MS8

TX MS8

PropagationDelay

DD

+3TS

TA

Timing Advance2 - Without Timing Advance: Collision

Ti i Advance


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CAN WHAT HOW WHEN WHAT

CAN

WHAT

HOW

WHEN

WHAT

TX BTS

RX BTS

RX MS1TX MS1

RX MS2TX MS2

RX MS3TX MS3

RX MS4TX MS4

RX MS5TX MS5

RX MS6TX MS6

RX MS7TX MS7

RX MS8TX MS8

yes

the

PropagationDelay

DD

+3TS - TA

yes the

Timing Advance = 2 * Propagation Delay

GSMms-isdn

ms-isdn

GSM

Timing Advance3 - With Timing Advance: No Collision


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GSM in comparison with other

Standards GSM gives mobility without any loss in Audio quality

Encryption techniques used gives high security in theair Interface and also use of SIM.

Bit Interleaving for high efficiency in Transmission.

Variable Power (Power budgeting- extend battery life)

Minimum Interference.

Features-CCS7 Signaling SMS (Short Message Services)

Emergency Calls

CELL Broadcast


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TOPICS

GSM CONCEPTS



GSM RADIO LINK

MOBILITY MANAGEMENT

CALL MANAGEMENT



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AuC

MS

MS

BTS

BTS

BTS

BSC

BSC

MSC

MSC

VLR

VLR

GMSC

HLR

PSTN

EIR

Um

Abis

Abis

A

A

OMC Server

Um

GSM - Network Structure

B

E

E

X.25

C

F

H

X.25


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GSM Network

OMC

AUC

HLR

MSC

EIRVLR

BSC

BTS

MS

ExternalPSTN &PDN N/W

SS

BSS

Switching

System

Base StationSystem

MS Mobile StationBTS Base transceiver SystemBSC Base Station Controller

MSC Mobile Switching CenterHLR Home Location RegisterVLR Visitor Location RegisterEIR Equipment Identity RegisterAUC Authentication CenterOMC Operation And Maintenance Center

GSM Architecture


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GSM Architecture

HLR

VLR

EIR

AUC

MSC

B

S

C

B

S

C

SMSC

PSTN

VMSC

Mobile

Station

GSM

Air interface

OMCR

TRAU

Base Station System

Network and switching

subsystemA interface SS7 / speech

SS7

X.25

BTSBTS

BTS

BTS

BTSBTS

Abisinterface

Ainterface

OMCS


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Mobile Equipment(ME)

Frequency and Time Synchronization

Voice encoding and transmission

Voice encryption/decryption functions

Power measurements of adjacent cells

Display of short messages

International Mobile Equipment Identifier (IMEI)


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SIM Portable Smart Card with memory (ROM-6KB to

16KB-A3/A8 algorithm, RAM- 128KB TO 256KB,EEPROM- 3KB to 8KB )

Static Information

International Mobile Subscriber Identity(IMSI)

Personal Identification Number (PIN)

Authentication Key (Ki)

Dynamic Information

Temporary Mobile Subscriber Identity(TMSI) Location Area Identity (LAI)

Phone memories, billing information

Ability to store Short Messages received


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SIM-Card and GSM Mobile

Equipment

G S M

Global GSM MobilityCardThe Smart Card to use

+

SIM-Card

Contains:- IMSI

=


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The SIM-Card Functions

Microchip with storeduser information

Credit Card Size

Permanent data:- Unique mobile subscriber identitythrough IMSI number and PIMSI

for Packet Mode

- Authentication parameter Ki,

- Authentication algorithm A3,

- Generating encryption key Kcalgorithm A8,

- PIN code.

Removable data:- Temporary Mobile Subscriber Number,- Location Area Identification- Routing Area Identification (Packet mode)

SIM-Card

G S M

Global GSM MobilityCardThe Smart Card to use

25 mm

15 mm


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Subscriber Identification

NatureInternational Mobile Subscriber Identity

Conformity with E212

Mobile Station -Integrated Services DigitalNetwork Nb

Similar to ISDN,Conformity with E164/E213

Nb. digits 3 2 max 10 1 to 3 2 to 4 total max 15

*This code does not identify a geographical areabut an operator

MS - ISDN

FormatMCC MNC MSIN

H1 H2 x x x ......... x x xCC NDC SN

M1 M2 x x x x x x x x

MeaningMobile

CountryCode

MobileNetwork

Code

Mobile SubscriberIdent. Nb

H1 H2 = Identity of HLR

within the home PLMN

CountryCode

(wheresubscription

has been made)

NationalDestination

Code *

Mobile Subscriber(national definition)

M1 M2 = nbr of logical HLR

IMSI

National Significant Mobile NumberIdentify a PLMN

worldwideIdentify the subscriber

of a PLMN


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Description Stored in SIM Card

MobileCountryCode

3 digits

MobileNetworkCode

2 digits

Mobile SubscriberIdentification Number (MSIN)

H1 H2 X X X X X X10 digits max

Location Area CodeLAC

Temporary MobileSubscriber Identity

4 octets

G S M

Global GSM MobilityCardThe Smart Card to useMCC

=208 (France)

234 (G-B)262 (Germany)404,405(India)

MNC=

71(APBSNL)72(TNBSNL)

20 (Bytel) IMSI = 15 digits max

NMSI

LAI

MobileCountryCode

3 digits

MobileNetworkCode

2 digits

Routing Area CodeRAC

RAI


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CountryCode

3 digits max

NationalDestinationCode2 or 3 digits

Subscriber Number (SN)

Roaming Number (RN)

HO-number

Must be dialed tomake a call tomobilesubscriber

Is a PSTN-likenumber to track theMS that hands overto another MSCduring call-in-state

Is a PSTN-likenumber used toreach a roamingMS

CC= 33 (France)091(India)001(US)

NDC = 9448(BSNL-karnataka)9845,9880(Airtel)

9886(Hutch)

= 660, 661, 618 (Bytel)

M1 M2 X X X X X X X X X X X X X10 digits max

CountryCode

NationalDestinationCode

CountryCode

National

DestinationCode

MS-ISDN (15 digits max)

MSRN

Description Stored in the Network


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Descriptor Embodied in the MobileEquipment

Type ApprovalCode

TAC FAC SNR SP

Final AssemblyCode

Serial NumbeR (SPare)

IMEI enables the operator to checkthe Mobile Equipment Identityat call setup and make surethat no stolen or unauthorized MSis used in the GSM network


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International Mobile Equipment Identity (IMEI)

Type ApprovalCode

TAC FAC SNR SP

Final AssemblyCode

Serial number (SPare)

IMEI: * # 0 6 #351475 60 926514 4


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MS Classmark

Revision level

RF power

Encryption algorithm

Frequency

Short message

LoCation Services

MS Positioning Method

8-PSK modulation

Multi-slot class

Multi-band

Classmark

Power classes

Class GSM400/850/900

1

2

3

45

8 W*

5 W

2 W**0.8 W

GSM1800

GSM1900

1 W**

0.25 W

4 W

1 W**

0.25 W

2 W

* Typical value for car mounted** Typical value for handheld

Class

GSM

400/850/900

GSM

1800

GSM

1900E1

E2

E3

2 W

0.5 W

0.2 W

1 W

0.4 W

0.16 W

1 W

0.4 W

0.16 W

For GMSK modulation

For 8-PSK modulation


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Base Transceiver Station

(BTS) Handles the radio interface to the mobile station.

Consists of one or more radio terminals fortransmission and reception

Each Radio terminal represents an RF Channel

TRX and MS communicates over Um interface

Received data transcoding

Voice encryption/decryption Signal processing functions of the radio interface

Uplink Radio channel power measurements


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Base Station Controller (BSC) Provides all the control functions and physical links

between the MSC and BTS

External Interfaces

Abis interface towards the BTS

A interface towards the MSC

Monitors and controls several BTSs

Management of channels on the radio interface

Alarm Handling from the external interfaces Performs inter-cell Handover

Switching from Abis link to the A link

Interface to OMC for BSS Management


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Mobile Switching Center

(MSC) Performs call switching

Interface of the cellular network to PSTN

Routes calls between PLMN and PSTN

Queries HLR when calls come from PSTN to mobileuser

Inter-BSC Handover Paging

Billing


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Home Location Register

(HLR) Stores user data of all Subscribers related to the

GMSC

International Mobile Subscriber Identity(IMSI)

Users telephone number (MS ISDN)

Subscription information and services

VLR address

Reference to Authentication center for key (Ki) Referred when call comes from public land network


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Visitor Location Register

(VLR) Database that contains Subscriberparameters and location information for allmobile subscribers currently located in thegeographical area controlled by that VLR

Identity of Mobile Subscriber

Copy of subscriber data from HLR

Generates and allocates a Temporary

Mobile Subscriber Identity(TMSI) Location Area Code

Provides necessary data when mobileoriginates call


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Authentication Center (AuC)

Stores Subscriber authentication data called Ki, acopy of which is also stored in in the SIM card

Generates security related parameters to authorize a

subscriber (SRES-Signed RESponse)

Generates unique data pattern called Cipher key (Kc)for user data encryption

Provides triplets - RAND, SRES & Kc, to the HLR on

request.


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EIR (Equipment Identity

Register) EIR is a database that contains a list of all valid

mobile station equipment within the network,where each mobile station is identified by its

International Mobile Equipment Identity(IMEI). EIR has three databases.,

White list - For all known,good IMEIs

Black list - For all bad or stolen handsets

Grey list - For handsets/IMEIs that areon observation


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Location Area Identity

LAI identifies a location area which is a group ofcells..

It is transmitted in the BCCH.

When the MS moves into another LA (detected by

monitoring LAI transmitted on the BCCH) it mustperform a LU.

LAI = MCC + MNC + LAC

MCC= Mobile Country Code(3 digits), identifies the country

MNC= Mobile Network Code(1-2 digits), identifies the GSM-PLMN

LAC= Location Area Code, identifies a location area within aGSM PLMN network. The maximum length of LAC is 16bits,enabling 65536 different location areas to be defined in

one GSM PLMN.


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Interfaces and Protocols

Um

Abis A

C

B

E

D

F

DigitalNetworks

POTS

TUP

ISUP

MAP

MAP

MAP

BSSAPLAPD

LAPDm

G


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GSM Entities and SignalingArchitecture


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GSM Protocols

CM - Connection Management

MM - Mobility Management

RR - Radio resource

LAPDm - LAPD for mobile

LAPD - Link Access Procedure for D channel

BTSM - BTS Management Part BSSAP - BSS Application Part (BSC - MSC)

DTAP - Direct Transfer Application Part (MS - MSC)

MAP - Mobile Application Part

MTP - Message Transfer part of SS7 SCCP - Signalling Connection Control Part of SS7

TCAP - Transaction Capabilities Application Part

ISUP - ISDN User Part


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Functional Plane of GSM

MS BTS BSC MSC/ HLR GMSCVLR

MS BTS BSC MSC/VLR HLR GMSC

CC

MM

RR

Trans

TOPICS


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TOPICS

GSM CONCEPTS


IDENTIFIERS USED IN GSM

GSM CHANNELS GSM RADIO LINK

MOBILITY MANAGEMENT

CALL MANAGEMENT RADIO RESOURCE MANAGEMENT

TOPICS


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TOPICS

GSM CONCEPTS


IDENTITIES USED IN GSM

GSM CHANNELS GSM RADIO LINK

MOBILITY MANAGEMENT



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Channels : differentiating

between Physical and LogicalchannelsPhysical channels : The combination of an ARFCN

and a time slot defines a physical channel.

Logical channels : These are channels specified byGSM which are mapped on physical channels.


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Physical channel:One timeslot of a TDMA-frame on one carrieris referred to as a physical channel.There are 8 physical channels per carrier in

GSM,channel 0-7(timeslot 0-7)

Logical channel:A great variety of information must be

transmitted between BTS and the MS,for e.g.user data and control signaling.Dependingon the kind of information transmitted werefer to different logical channels.These logical

channels are mapped on physicalchannel.

Channel concept

Logical Channels on Air interface


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Logical Channels on Air interface

LOGICAL

CHANNELS

COMMON

CHANNELS

DEDICATED

CHANNELS

BROADCASTCHANNELS

COMMONCONTROL

CHANNELS

DEDICATEDCONTROL

CHANNELS

TRAFFICCHANNELS

FCCH BCCHSCH SDCCH SACCH FACCH

PCH AGCHRACH TCH/F TCH/EFRTCH/H


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FCCH

Logical channelsLogical channels

Control channels Traffic channels

BCH CCCHDCCH

Half

rate

Full

rate

SCH BCCH PCH AGCH RACH SDCCH SACCHFACCHCBCH


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Broadcast channels BCH Broadcast Channel-BCH

Alloted one ARFCN & is ON all the time in every cell.Present in TS0 and other 7 TS used by TCH.

Frequency correction channel-FCCH

To make sure this is the BCCH carrier. Allow the MS to synchronize to the frequency.

Carries a 142 bit zero sequence and repeats once in every10 frames on the BCH.

Synchronization Channel-SCH This is used by the MS to synchronize to the TDMA framestructure within the particular cell.

Listening to the SCH the MS receives the TDMA framenumber and also the BSIC ( in the coded part- 39 bits).

Repeats once in every 10 frames.


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Broadcast channels BCH ... BCCH

The last information the MS must receive in order to receivecalls or make calls is some information concerning the cell.This is BCCH.

This include the information of Max power allowed in the cell.

List of channels in use in the cell.

BCCH carriers for the neighboring cells,Location AreaIdentity etc.

BCCH occupies 4 frames (normal bursts) on BCH and

repeats once every Multiframe. This is transmitted Downlink point to multipoint.

Cell Broadcast Channel - CBCH

Used for the Transmission of generally accessibleinformation like Short Message Services(SMS)


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Common Control Channels

CCCH CCCH- Shares TS-0 with BCH on a Multiframe.

Random access channel-RACH:

Used by Mobile Station for requesting for a channel. Whenthe mobile realizes it is paged it answers by requesting asignaling channel (SDCCH) on RACH. RACH is also usedby the MS if it wants to originate a call.

Initially MS doesnt know the path delay (timing advance),

hence uses a short burst (with a large guard period = 68.25bits).

MS sends normal burst only after getting the timing advanceinfo on the SACCH.

It is transmitted in Uplink point to point.


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Common Control Channels

CCCH .. Access Grant Channel-AGCH

On request for a signaling channel by MS the networkassigns a signaling channel(SDCCH) through AGCH. AGCH

is transmitted on the downlink point to point. Paging Channel-PCH

The information on this channel is a paging messageincluding the MSs identity(IMSI/TMSI).This is transmitted on

Downlink, point-to-multipoint.


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Dedicated Control Channels-

DCCH Stand alone dedicated control channel(SDCCH)

AGCH assigns SDCCH as signaling channel onrequest by MS.The MS is informed about which

frequency(ARFCN) & timeslot to use for traffic. Used for location update, subscriber authentication,

ciphering information, equipment validation andassignment of TCH.

This is used both sides, up and Downlink point-point.


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Dedicated Control Channels-

DCCH Slow associated control channel-SACCH

Transmission of radio link signal measurement, powercontrol etc.

Average signal strengths(RXLev) and quality of service(RXQual) of the serving base station and of the neighboringcells is sent on SACCH (on uplink).

Mobile receives information like what TX power it has totransmit and the timing advance. It is associated with TCH

or SDCCH Fast associated control channel-FACCH

Used for Hand over commands and during call setup andrelease. FACCH data is sent over TCH with stealing flag set


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Traffic Channels-TCH

TCH carries the voice data.

Two blocks of 57 bits contain voice data in the normalburst.

One TCH is allocated for every active call.

Full rate traffic channel occupies one physicalchannel(one TS on a carrier) and carries voice dataat 13kbps

Two half rate (6.5kbps) TCHs can share one physicalchannel.

GSM Channels


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GSM Channels

Control ChannelsTraffic Channels(TCHs)

Fullrate

Halfrate

Dedicated ControlChannels

(DCCHs)

SlowFast

Downlink

BroadcastChannels

(BCHs)

Common ControlChannels

(CCCHs)

Downlink Uplink

TCH /F TCH /H FCCH SCH BCCH PCH CBCH RACHAGCH SDCCH SACCHFACCH

Traffic Multiframing Signaling Multiframing Traffic Multiframing

(down uplink)

C a e s

The Logical Channels on Radio Interface


72/169

75FACCH

BTS

0 1 2 3 4 5 6 7TS

MS

FCCH

SCH

BCCH

PCH

AGCH

CBCH

SDCCH

SACCH

TCH

TCH

FACCH

SDCCHSACCH

FCCH

SCH

BCCH

RACH

PCH

AGCH

RACH

CBCH

Synchronization

Frequency correction

Broadcast control

Access request

Subscriber paging

Answer to Access request

Broadcast info

Dedicated Signaling

Sys InFo 5, 6 + SMS

Traffic (speech data)

Associated Signaling

Associated Signaling

Traffic (speech-data)

Radio Measurement + SMS

Dedicated Signaling

Broadcast info

M.S. Pre-synchronization

Access request

Subscriber paging

Answer to Access request

The Logical Channels on Radio Interface

Logical Channel Description


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76

FACCH MESSAGES

Connection establishment fromSDCCH to TCH

End validation of a SDCCH-TCHcommutation

Characteristics of the future used BSafter handover

Connection establishment to BS afterhandover

Validation of an handover

SACCH MESSAGES

Measures:

-power level of the communication-quality level of the communication

- level on the beacon frequency ofthe neighboring cells

Timing Advance

Power Control

SMS

TCH MESSAGES

Speech Data

Handover Access message (uplink)

SDCCH MESSAGES

Request for a SDCCH assignment

Request for the end of channelassignment

Order of commutation from SDCCH toTCH

SMS


(1/2)



74/169

77

FCCH MESSAGES

no message is sent (all bits 0)

BCCH MESSAGES

System Information type 1, 2, 2bis,2ter, 3, 4, 7, 8

(idle mode)

SCH MESSAGES

Frame Number

Base Station Identity Code (BSIC)

AGCH MESSAGES

For dedicated channel assignment:-frequency number

-slot number-frequency hopping description-Timing Advance (1st estimation)-MS identification

PCH MESSAGES

messages containing a mobileidentity for a call, a short messageor an authentication

RACH MESSAGES

Service request:

-emergency call-answer to an incoming call-outgoing call-short message-call re-establishment- inscription

CBCH MESSAGES

Specific information(weather, road information


(2/2)

Traffic and Control Multiframing


75/169

79

0 1 2 3 4 21 22 23 24 25 0 1 2 3 4 46 47 48 49 50

26 traffic frames = 120 ms

1 Hyperframe = 2,715,648 frames= 3h 28 min. 53 s 760 ms

0 1 2 3 5 2042 2043 2044 2045 2046 20474

1326frames

0 1 2 3

46 47 48 49 500 1 3 42

22 23 2524

TS0

TS1

TS2

TS3

TS5

TS6

TS7

TS0

TS1

TS2

TS3

TS4

TS5

TS6

TS7

TS0

TS1

TS2

TS3

TS4

TS5

TS6

TS7

TS4

TS0

TS1

TS2

TS3

TS4

TS5

TS6

TS7

TS0

TS1

TS2

TS3

TS4

TS5

TS6

TS7

Frame4.615 ms

Control channelTraffic channel

51 x 26 traffic frames = 6.12 s

26 x 51 control frames = 6.12 s

g


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80

Logical Channel Mapping


77/169

82

Full Rate - Downlink & Uplink

T : TCH A : SACCH : IDLETi: TCHsub-channel no. i

Ai: SACCHsub-channel no. i

time

26 frames = 120 ms

T0 A0T0 T0 T0 T0 T0 T0 T0 T0 T0 T0 T0T1 T1 T1 T1 T1 T1 T1 T1 T1 T1 T1 T1 A1 time

Half Rate - Downlink & Uplink

T AT T T T T T T T T T TT T T T T T T T T T T T

T

26 frames = 120 ms

g pp g1 - Traffic Channel Combination

Logical Channel Mapping2 Dedicated Signaling Channel Combination


78/169

83

A : SACCH D : SDCCH : IDLE

51 frames = 235 ms

A1 A2 A3A0D7D6D5D4D3D2D1D0

A5 A6 A7A4D7D6D5D4D3D2D1D0

time

Downlink

51 frames = 235 ms

A5 A6 A7 A0

A4

D7D6D5D4D3D2D1D0

D7D6D5D4D3D2D1D0A1 A2 A3

time

Uplink

AAAA

2 - Dedicated Signaling Channel Combination



79/169

84

51 frames = 235.38 ms

Downlink

time

51 frames = 235.38 ms

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 R R R R R

Uplink

time

B : BCCHS : SCHF : FCCH : IDLE: PCH /AGCHC R : RACH

BTS MSPhysical Channel

ARFCN (n) TS (s)

FCCH

SCH BCCH

PCH/AGCH

Frames repeat continuously

Multiframe

m+1

Multiframem-1

Multiframe m

C CF SC CF SC CF SC CCBF S F S BF SC

g g3 - Common Channel Combination



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85

A3A2

A1D3D2

D3D2

D1

D1

D0

D0 F SF SF SC CC F SBF S

F SF SF SC CC F SBF S

51 frames = 235 ms

A0

time

Downlink

R R

R R D2

D2

D1

D1

D0

D0A1

A3

A0

A2R

R

R

R

D3

D3

51 frames = 235 ms

time

Uplink

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

A : SACCH D : SDCCH : IDLEB : BCCHS : SCHF : FCCH: AGCH/PCHC R : RACH

g g4 - Common Channel Combination


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86

Why 26 and 51 Frames per Multiframe?


82/169

87

Downlink

message

Uplinkmessage

Neighboring BTS(downlink)

Measurement Windows

C CF SC CF SC CF SC CCBF S F S F S

0 1 12 25 0 1 12 25

0 1 10 20 30 40 50 0 1

T AT T T T T T T T T T TT T T T T T T T T T T T T AT T T T T T T T T T TT T T T T T T T T T T T

Mobile

activity

Rx Rx Tx Rx Rx Tx Rx Rx Tx

(n) (n) (n)

TOPICS


83/169

88

TOPICS

GSM CONCEPTS



GSM CHANNELS

GSM RADIO LINK

MOBILITY MANAGEMENT


From Speech to Radio Transmission


84/169

89

Speech

Sourcedecoding

Channeldecoding

De-interleaving

Burst deformatting

Deciphering

Demodulation

equalization

Digitizing andsource coding

Channelcoding

Modulation

Ciphering

Burst formatting

Interleaving

Step 1

Step 2

Step 3

Step 4

Transmission

Step 5

Step 6 Diversity


85/169

90

GSM Radio Link

Speech Coding -Done at Transcoder of BSC and MS

The Linear Predictive Coder uses RPE-LTP(Regular PulseExcitation- Long Term Prediction)

Converts 64kbps voice to 13kbps(260 bits every 20ms) Channel Coding - Done at BTS and MS

Uses Convolution Coding and CRC (Cyclic RedundancyCheck)

Converts 13 kbps to 22.8 kbps (456 bits per 20ms)


86/169

91

GSM Radio Link

Bit Interleaving - Done at BTS and MS

Encryption - Done at BTS and MS

EX OR data with cipher block, which is generated by

applying A5 Algorithm to the Ciphering Key(Kc) Multiplexing - Done at BTS

Modulation - Done at BTS and MS

GMSK(Gaussian filtered Minimum Shift Keying)

Phase change of +90 for 0 and -90 for 1

Speech Coding


87/169

94

BP A/D SPEECHENCODERCHANNEL

CODING

LP D/A SPEECHDECODERCHANNELDECODING

BANDPASS

300 Hz -3.4 kHZ

Every 125 s value issampled from analogsignal and quantised by13 bit wordData rate = 13/125*10 -6

= 104 kbps

Every 20ms 160 samplestakenData rate = 160 * 13/20ms

= 104 kbps

Linear Predictive Coding & RegularPulse Excitation Analysis

1. Generates 160 filter coeff2. These blocks sorted in 4 sequence

1,5,9,37 / 2,6,10----38/3,7,1139/8,12,1640

3. Selects the sequence with mostenergy

So data rate = 104/4 = 26 kbps

Long term prediction analysis1. Previous sequences stored in memory2. Find out the correlation between thepresent seq. And previous sequences3. Select the highest correlation sequence4. Find a value representing the differencebetween the two sequences.

Reduces data rate = 26 kbps/2 = 13 kbps

ie 260 bits in 20ms

50 132 78

1A 1B 2

1A = Filter Coeffblock ampl, LTPparams

1B = RPE pointers &pulses2 = RPE pulse & filterparams

50 3 132 4

3 crc bitsFour 0 bits for codec

378 coded bits

Conv coding rate = 1/2 delay = 4

78

456 bits in 20 ms = 22.8 kbps57 x 8 = 456

To modulator

Channel Processing in GSM


88/169

95

C

20 ms20 ms

A

A8

A7

A6

A5

B4

B3

B2

B1

B8

B7

B6

B5

C4

C3

C2

C1

57 bits

Information

1 1

CRL CRL

3 3

Tail Tail

26 bits

Training

8 Bursts

8 Sub blocksof 57 bits

Source coding

Channel coding

Interleaving

Normalburst

20 ms

B

456 bitsA 456 bitsB 456 bitsC

57 bits

Information

A8B4A7B3A6B2A5B1 B8C4B7C3B6C2B5C1

Speech blocks

Codec dependent Codec dependentCodec dependent

Overview for Full Rate


89/169

96

Channel Processing in GSM


90/169

97

C

20 ms20 ms

A

A4

A3

A2

A1

B2

B1

B4

B3

C4

C3

C2

C1

4 Bursts

4 Sub blocksof 57 bits

Source coding

Channel coding

Interleaving

20 ms

B

228 bitsA 228 bitsB 228 bitsC

A4B2

A3B1

B4C2

B3C1

Speech blocks

Codec dependent Codec dependentCodec dependent

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

Overview for Half Rate

Interleaving: TCH Full Rate


91/169

98

0 1 2 3 4 5 6 7 8 ... ... 452 453 454 455

0 1 2 3 4 5 6 78 9 10 11 12 13 14 15

448 449 450 451 452 453 454 455

57Rows

Divide 456 bits in 8 sub-blocks

765432107654 0 1 2 3

reordering&

partitioningout

diagonalinterleaving

456coded bits

burst

b0 b1 b56 b1 b56b0

bitinterleaving

Burst Formatting


92/169

99

1 frame:4.615 ms

0 1 2 3 4 5 6 7

Guard

157 126 57

DATA

156.25 bits duration(0.577 ms)

Trainingsequence

33

DATA

8.25

S SGuardBand

Burst

148 bits

Normal Burst

Burst Formats


93/169

100

Synchronization Burst(SCH)

Tail Data Extended Training Sequence Data Tail


3 bits 39 encrypted bits 64 synchronization bits 39 bits 3 bits 8.25 bits

GuardPeriod

Frequency Correction Burst(FCCH)

Tail Data Tail


3 bits 142 fixed bits (0) 3 bits 8.25 bits

Guard

Period

N l B

Burst Formats


94/169

101

Access Burst

TailTraining

Sequence Guard PeriodTail

156.25 bits (0.577 ms)

8 bits 36 encrypted bits 68.25 bits3 bits41 synch bits

Data

Dummy Burst

Tail Dummy Sequence Training Sequence Dummy Sequence Tail

3 bits 58 mixed bits 26 midamble bits 58 mixed bits 3 bits 8.25 bits

Guard

Period

156.25 bits (0.577 ms)

156.25 bits (0.577 ms)

13 bits 57 encrypted bits 1 26 bits 57 encrypted bits 3 bits 8.25 bits

Tail Data Training Sequence Data Tail GuardPeriod

Normal Burst

B b

Ciphering


95/169

102

Plain data: 0 1 1 1 0 0 1 0.....Ciphering sequence: 0 0 0 1 1 0 1 0.....XOR:Ciphered data (transmitted): 0 1 1 0 1 0 0 0.....

Ciphered sequence: 0 0 0 1 1 0 1 0.....XOR:Recovered data: 0 1 1 1 0 0 1 0.....

Data S S DataBurst to betransmitted

Data S STraining

sequenceData

Receivedburst

Interleaving


96/169

103

g

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

57 57 57 57

57 57 57 57

57 57 57 57

57 57 57 5757 57 57 57

57 57 57 57 57 57 57 57

57 57 57 57

Encoded speech blocks - Diagonal Interleaving

Even bits

Odd bits

Tb3

Coded Data57

F1

Training Sequence26

F1

Coded Data57

Tb3

Gp8.25

Bn-4 Bn-3 Bn-2 Bn-1 Bn Bn+1 Bn+2 Bn+3

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

57 57 57 57

57 57 57 57

57 57 57 57

57 57 57 5757 57 57 57

57 57 57 57

Encoded control channel blocks - Rectangular Interleaving

Even bits

Odd bits

Bn-4 Bn-3 Bn-2 Bn-1 Bn Bn+1 Bn+2 Bn+3


97/169

104

Burst The information format transmitted during one

timeslot in the TDMA frame is called a burst.

Different Types of Bursts

Normal Burst

Random Access Burst Frequency Correction Burst

Synchronization Burst


98/169

105

Normal Burst

T3

Coded Data57

S1

T. Seq.26

S1

Coded Data57

T3

GP8.25

Tail Bit(T) :Used as Guard TimeCoded Data :It is the Data part associated with the burstStealing Flag :This indicates whether the burst is carrying

Signaling data (FACCH) or user info (TCH).Training Seq. :This is a fixed bit sequence known both to

the BTS & the MS.This takes care of thesignal deterioration.

156.25 bits 0.577 ms

156.25 bits 0.577 ms


99/169

106

T3

Training Sequence41

Coded Data36

T3

GP68.25

Random Access Burst

T3

Fixed Bit Sequence142

T3

GP8.25

T

3

Coded Data

39

Training Sequence

64

Coded

Data 39

T

3

GP

8.25

Freq. Correc. Burst

Synchronization Burst

156.25 bits 0.577 ms

156.25 bits 0.577 ms

Transmission on the


100/169

107

radio channels A timeslot has a duration of .577 m seconds (148 Bits) 8 timeslots(8 x 0.577 = 4.62 ms) form a TDMA frame If a mobile is assigned one TS it transmits only in this timeslot and stays idle for the other 7 with its transmitter off, calledbursting

The start on the uplink is delayed from downlink by 3 TSperiods One TS = duration of 156.25 bits, and its physical contents is called a burst

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

DownlinkBTS > MS

UplinkMS > BTS

Offset


101/169

108

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

MS1near

MS2far

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

AtBTS

0 1 2 3 4 5 6 7MS1near

0 1 2 3 4 5 6 7MS2far

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

AtBTS

Timing Advance

Frames Types On Um


102/169

109

ypInterface TDMA Frame

8 Time slots (Burst Period)

Length is 4.62 ms(8 * 0.577ms)

26-TDMA Multiframe

26 TDMA Frames (24 TCH, SACCH, Idle)

120 ms (26 * 4.62ms)

51-TDMA Multiframe

26 TDMA Frames (FCCH, SCH, BCCH, SDCCH, CCCH)

235.6 ms (51 * 4.62ms)

Frames Types On Um


103/169

110

Frames Types On Um

Interface Super Frame 51* 26 TDMA Frames

6.12 S

Hyper Frame 2048 * 51* 26 TDMA Frames

3 Hours, 28 Minutes, 53 Secs and 760 ms

TOPICS


104/169

111

GSM CONCEPTS



GSM CHANNELS

GSM RADIO LINK

MOBILITY MANAGEMENT



105/169

112

Mobility Management

Mobility Management (MM)

Location updating- normal,periodic, IMSI attach

Paging

Security Management

Preventing unauthorized users- authentication

Maintaining Privacy of users- ciphering

Providing roaming facility

MM functionality mainly handled by MS, HLR,MSC/VLR.

Network Attachment


106/169

113

Cell Identification

MS scans complete GSM frequency band forhighest power

Tunes to highest powered frequency and looksfor FCCH. Synchronizes in frequency domain

Get training sequence from SCH which followsFCCH. Synchronizes in time domain.

Accesses BCCH for network id, location area andfrequencies of the neighboring cells.

Stores a list of 30 BCCH channels


107/169

114

Network Attachment..

PLMN Selection

Get the operator information from SIM.

Cell Selection

Selected cell should be a cell of the selected

PLMN

Signal strength should be above the threshold.

Cell should not be barred

Location Update

Register with the network by means of locationupdation procedures.

MS Location Update


108/169

115

MS BTS BSC (G)MSC VLR HLR

Action

Channel Request (RACH)

Channel Assignment (AGCH)

Authentication Request (SDCCH)

Authentication Response (SDCCH)

Comparison of Authentication para

Accept LUP and allocTMSI (SDCCH)

Ack of LUP and TMSI (SDCCH)

Entry of new area and identity intoVLR and HLR

Channel Release (SDCCH)

S ocat o Update(registration)

Location Update Request (SDCCH)TMSI + old LAI


109/169

116

Security - Authentication

Authentication centerprovides RAND to MobileAuC generates SRES using

Ki of subscriber and RANDMobile generates SRESusing Ki and RANDMobile transmits SRES toBTS

BTS compares receivedSRES with one generatedby AuC

MSKi RAND

A3

SRES

RAND

SRES

SRES

Auth Result

AuCBTSMS


110/169

117

Security - Ciphering

Data sent on airinterface ciphered

for securityA5 and A8algorithms used tocipher data

Ciphering Key isnever transmittedon air

MSKi RAND

A8

Kc

MS Network

Um interface

A5 A5

Kc Kc

Data DataCipheredData

TOPICS


111/169

118

GSM CONCEPTS



GSM CHANNELS

GSM RADIO LINK

MOBILITY MANAGEMENT


Communication Management


112/169

119

Communication Management

(CM) Setup of calls between users on request Routing function i.e. Choice of transmission

segments linking users

Point to Point Short message services

PLMN Selection


113/169

No

automaticmode

The MS selects the firstPLMN from the preferredPLMNs list (if it is not in

the forbidden PLMNs list)

The user selects aPLMN from the

displayed PLMNs

manualmode

YesYes

Creation of a foundPLMN list

Is there an up to datefound PLMNs list?

End of PLMNselection

YesNo (automatic)

Cell Selectionsucceed?

Selection of thenext preferredpossible PLMN

No (manual)

PLMN SelectionC


114/169

Listen to all the

frequencies of the GSMspectrum:

power level measurementand average on these

measurements

Select the best

frequenciesaccording to the

power level

(124 channels in GSM900, 374 in GSM 1800and 299 in GSM 1900

(30 in GSM 900 and 40 in GSM 1800)

Memorize thebeacon

frequencies in the

precedentselection

=> Create theFound PLMN list

Constitution of the "Found PLMN list"

Li f h

Initial Cell Selection


115/169

Suitable cell:

- cell of the selected PLMN- cell not barred- C1 > 0

Eligible cell

List of thefrequencies of the

selected PLMN

IMSI Attach

Look for the cell with the bestC1 in the suitable cells list

Eligible cell?

Yes

Selection ofanother PLMN

No

C1 Computation foreligible cells

Suitable cell?

Yes

No

Rejected?

Yes

PLMN set in the forbiddenPLMN list

End of Cell Selection

No

CellSelection


116/169

BTS-2

BTS-1

This cell

BTS-3

BTS-4

BTS-5

1

1

1

1

2

3

45

Purpose: get synchronizationwith the GSM networkprior establishing any communication.

1

Immediate Assignment


117/169

MS BSC MSC

CM SERVICE REQUEST

SDCCH or TCH6

CHANNEL REQUEST

RACH1

BTS

CHANNEL REQUIRED2

CHANNEL ACTIVATION3

IMMEDIATE ASSIGNMENTAGCH

5 IMMEDIATE ASSIGNMENTCOMMAND5

CHANNEL ACTIVATION

ACK.4

ImmediateAssignment

LOCATION UPDAT. REQU.

SDCCH or TCH6

OR

Registration: the Very First LocationUpdate


118/169

LAI HLR

IMSIVLR id

TMSI

IMSI

TMSI

Release

VLR

IMSITMSI

LAI

MSC

BTS

BSS

BSC

2

4

5

2

6

1

2

4

5

6

3

4TMSI

5

Intra VLR Location Update


119/169

Intra VLR Location Update

VLR

IMSITMSI

LAI

1

2

3

4

new TMSI

TMSI + old LAI 2

3

42

3TMSI

New TMSI

New LAI

MSC

BTS

BSS

BSC

IMSI not Required

BSS

Inter VLR Location Update


120/169

128

New LAI

newTMSI

TMSI + old LAI

TMSI New TMSI

MSC

BSS

BTS

BSC

1

2

5

7

2

57

2

IMSI,TMSILAI

New VLR

IMSI, TMSIOld LAI

Old VLR

RAND, SRES,Kc

HLR

newVLR id

subscriberdata

3

4

6

6

5

IMSI not Required

RAND, SRES,Kc

IMSI Attach


121/169

129

MSCBTS

BSS

BSC

VLR

3

4

5

4

6

1 CHANNELREQUEST

2IMMEDIATEASSIGNMENT

LOCATION UPDATINGREQUEST (IMSI Attach)

3

5LOCATION UPDATINGACCEPT (LAC, TMSI)

4AuthenticationProcedure

IMSI Attach

IMSI Detach


122/169

130

MSC

BTS

BSS

BSC

VLR

1 CHANNELREQUEST

2IMMEDIATEASSIGNMENT

IMSI DETachINDication

3

4CHANNELRELEASE

IMSI DETachINDication

3

IMSI Detach

BSS MSC PSTN

Mobile Originating Call


123/169

132

ACM = Address Complete MessageANM = ANswer MessageIAM = Initial Address Message

MS BSS MSC

CHANNEL REQUEST1

PSTN

CM SERVICE REQUEST2 CM SERVICE REQUEST2

CALL PROCEEDING7CALL PROCEEDING

7

Assignmentprocedure7

IAM6

IMMEDIATE ASSIGNMENT2

ACM8

VLR

Ring

ANM10

ALERTING

9

SETUP (basic) orEMERGENCY

4 SETUP4

CONNECT11

CONNECT ACKnowledge11

Authenticationprocedure3

Cipheringprocedure3

5

Dialing

Ringing

Path

Established

Ringing

SendingNumber

Mobile Terminating Call


124/169

133

PSTN

LA1

LA2

BTS11

BTS21

BTS22

BTS31

BTS12

BTS23

HLR

4

3

5

1

2

5

6

6

BSC1

BSC2

BSC3

MSC/VLR

GMSC

1 - Paging Principle

Mobile Terminating Call2 - Detailed Procedure


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134

VMSCBSS

VLR

Visitor PLMN

GMSC

HLR

Home PLMN

RoutingInformation

(MSRN)

6

IAM : Initial Address MessageMSISDN : Mobile Station Integrated Services Digital

network NumberMSRN : Mobile Station Roaming Number

IMSI : International Mobile Subscriber IdentityGMSC : Gateway MSCVMSC : Visitor MSCTMSI : Temporary Mobile Subscriber Identity

PN

InternationalSS7

ISDNIAM (MSRN)

7IAM

(MSISDN)2

Send

RoutingInformation(MSISDN)

3

Provide Roaming Number

(IMSI)4

PAGE(TMSI + LA)

9

Send infoto I/C(MSRN)

8

Roaming Number

(MSRN)5

PAGINGREQUEST

(TMSI + LA)10

PAGINGREQUEST

(TMSI)

11

MSISDN

1

Mobile Terminating Call


126/169

135

MS BSS VMSC

CHANNEL REQUEST

(LAC, Cell ID)5

PSTN

IMMEDIATE ASSIGNMENT

(SDCCH or TCH)

6

PAGING REQUEST4

PAGING REQUEST

(TMSI or IMSI, LA)3

GMSC

IAM(MSISDN)

1IAM

(MSRN)2

CM SERVICE REQUEST

(Paging Response)7 PAGING RESPONSE

(TMSI or IMSI, LA)7

Authenticationprocedure8

Cipheringprocedure9

Address Complete Message11

ANswer Message12

Setup, Assignment, Alerting10

CONNECT12

Dialing

Ringing

Path

Established

3 - End to End Procedure

Call Release


127/169

136

MS BSS MSC

Call in progress1

RELEASE COMPLETE4

PSTN

DISCONNECT2 DISCONNECT

2

RELEASE3RELEASE

3

RF Channel Releaseprocedure 8

Release5

RELEASE INDICATION7

CHANNEL RELEASE6

Release

tone9

1 - Mobile Initiated

Call Release


128/169

137

PSTN

On hook

Purpose:informs the mobilethen releases radio

and network resources.

REL

RLC

MSC

BTS

BSS

BSC

1

1 1

12

33

4

55

4

6

2

2 - PSTN Initiated

Mobile Originated Call


129/169

138

Mobile Originated Call

Request for Service

Authentication

Ciphering

Equipment Validation

Call Setup

Handovers

Call Release

Mobile Terminated Call


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139


Paging

Authentication

Ciphering

Equipment Validation

Call Setup

Handovers

Call Release


MS


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MS

MS

BTS

BTS

BTS

BSC

BSC

MSC

VLR

GMSC

HLR

PSTN

EIR

AuC

Land to

Mobile call

(MSISDN)

Query for

VLR info

Reply

(MSRN)

Route

to MSC

Query VLR

for LAC and

TMSIPagingthe area

(+TMSI)

TMSI Pagedon PCH

Paging

Ch. REQ

over RACH

Allocate SDCCH

over AGCH

Page RESP on SDCCH

( TMSI + LAI)Page RESPage RES

Authentication and Ciphering procedure done as seen in Location Updation

Assign. REQ

Assignment CMD(=TCH) on SDCCH

* MS tunes

* Assgn CMP

* Phone rings

Connect traffic Ch.to trunk

frees SDCCH

Assgn CMP

Network Alerting

TOPICS


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141

GSM CONCEPTS



GSM CHANNELS

GSM RADIO LINK

MOBILITY MANAGEMENT


Radio Resource Management


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Establish maintain and release stable connectionsbetween MS and MSC

Manage Limited Radio and Terrestrial resources

Handover process is the sole responsibility of the RRLayer

Functions of RR layer are performed by MS and BSCand partly by MSC



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Power Control

Hand over Control

Discontinuous Transmission

Frequency Hopping


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BTS commands MS at differentdistances to use different power levelsso that the power arriving at the BTSs Rx isapproximately the same for each TS

- Reduce interference- Longer battery life

Power Control

Handover


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Handover

Means to continue a call even a mobile crossesthe border of one cell to anotherProcedure which made the mobile station really

roamHandover causesRxLev (Signal strength , uplink or downlink)RxQual (BER on data)O & M interventionTiming AdvanceTraffic or Load balancing

Handover Types


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Handover Types

Internal Handover (Intra-BSS)

Within same base station - intra cell

Between different base stations - inter cell

External Handover (Inter-BSS)

Within same MSC -intra MSC

Between different MSCs - inter-MSC

Handover TypesGMSC


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BSC

BSC

BSC

BSC

MSC

MSC

GMSC

C-1 C-2

C-3

C-4

HO requiredActivate TCH(facch)with HoRef#

Acknowledges and

HO performed

BSC

Intra BSC handover


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Periodic MeasurementReports (SACCH)

Periodic MeasurementReports

if1. Check for HO passed2. Channel avail in new BTS

Acknowledges andalloctes TCH (facch)

HO cmd with HoRef#Receives new BTS data(FACCH)

MS tunes into new frequencyand TS and sends HO message tonew BTS (facch)

Periodic Measurement

Reports (SACCH)

Release TCH

Cell 1

Cell 2

BTS 1

BTS 2

requency p an an mpor ance oBCCH


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B3

B2

B9

B6 B4

B1

Sectored

antennas

MS ( monitoring the

broadcast radio B1 in idle

mode )

F S B B B B .. F S .. .. I

F0 F50F2 F3 F4 F5 F10 F11F1

F,S,B exist in time slot 0 of each frame

B7

B8

B5

B10

B11

B12

BPL frequency plan:

Broadcast frequencies :

15 Broadcast channels = 48-62

15 Hopping channels = 32-46

What information does Broadcast Control channel

(BCCH) contain?


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150

( CC ) co ta

Serves as a Beacon for the Cell

Country Code (CC) and the Network Code (NC)

Location Area Identity (LAI)

List of neighboring cells which should be monitored by MS

List of frequencies used in the cell

Cell identity

Back

Location Updates

Location Updates can be classified into


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151

Location Updates can be classified into

two:

Periodic Location Updates:

This occurs as per the timer set by the network operator.

If the MS does not perform this update the MSC marksthe MS as Detached on the VLR.

Location Update on a handover:

This occurs if during a handover the MS is moved into anew Location Area Code (LAC).

1 The MS is monitoring the BCCH and has all the decoded


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152Back

1. The MS is monitoring the BCCH and has all the decodedinformation stored on the SIM ( including the LAC)

2. As soon as the mobile is on a TCH it sends the signalstrength indication on the corresponding SACCH

3. The BSC monitors the signal strengths and on analysis

sends a handoff request on FACCH. The handoffprocess is completed on the FACCH.

4. After the completion of call, the MS starts monitoring theBCCH again. On finding the LAC (stored on SIM) and that

decoded from the BCCH to be different , the MS requestsa Location Update through SDCCH.

Discontinuous


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Transmission

Discontinuous Transmission(DTX) allows theradio transmitter to be switched off most of thetime during speech pauses.

A Silence Indicator Block is transmitted at500bps, which generates a comfort noise

Down Link interference is decreased.

Up link battery is saved

Frequency Hopping


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Frequency Hopping

Frequency Hopping permits the dynamic switching ofradio links from one carrier frequency to another.

Base Band Hopping

At the BTS each the timeslot is shifted to another

transceiver, which is transmitting at the hopfrequency. User will be connected to different

Transceivers depending on hop sequence.

Synthesis Hopping

At the BTS transceiver changes the frequencies used.The user will be connected to only one transceiver.

Decreases the probability of interference

Suppresses the effect of Rayleigh fading

Wireless Data

Add-on to GSM network :PCU; Packet Segmentation/re-assembly and scheduling Radio channel access control and management Transmission error detection and retransmission. Power control

Enhanced Data rate for GSM Evolution EDGE is an enhancement of GPRS and CSD technologies. Based on the current GSM technology - same TDMA frame structure,same bandwidth (200 kHz).

Universal Mobile Telecommunication Standards Innovative Service Architecture : VHE Concept - providing the usthe same look and feel of its personalized services independent of


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Wireless Data

98 99 2000 2001

GSMDATA

HSCSD

GPRS

EDGE

UMTS

SIMToolkit

WAP

Data Application

Time

Circuit Switched technology

Packet Switched technology

Technology for Applications

SMS Data: 160 -numeric charactersUser Data Rate : 9.6kbpsOne time slot over the air interface

High Speed Circuit Switched DataUser Data Rate:14.5kbpsUse multiple timeslots (max=8),hence max rate = 115.2kbps.Needs a duplexor in MS forsimultaneous Tx and Rx

Power controlSGSN: GPRS mobility Encryption

ChargingGGSN : Interface to the PDN, Internet

Max user data rate : 21.4 kbpsDynamic rate adaptation to suit the radio conditions atthat time ( 9.05 kbps, 13.4 kbps, 15.6 kbps 21.4 kbps)

W@P Gateway W@P ServiceW@P

Fone

InternetMobile Network

Surf the Internet while on the move

W@P Gateway : Adaptation of the information to the mobile Compression of the data Buffering of the information

Uses 8-PSK modulation instead of GMSK. Requires good propagation conditions. Allows upto 48 kbps (EGPRS) and upto 28.8 kbps (ECSD) on every

radio channel EDGE helps GSM-Only operators to compete with UMTS.

the same look and feel of its personalized services independent ofnetwork and terminal. Global Convergence : Fixed/Mobile, Telecom/Datacom, public/private

Mobile Multimedia driven market. Wideband bearers - 2GHz band ( 5 MHz per carrier), -max. 2Mbps

References


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References

Wireless and Personal Communication Systems.Vijay.K.Garg and Wilkes

Overview of the GSM System and ProtocolArchitecture, IEEE Comm. Magazine, Moe Rahnema.

The GSM System for Mobile Communications-Michel Mouly & Marie-Bernadette Pautet

Overview of the GSM Comm- John Scourias.

Coverage or Traffic LimitationsTRAFFIC-LIMITED


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LIMITEDAREA(10000

subscribersper km2)

COVERAGE-LIMITED

AREA(-75 dBm

at cell edge)

COVERAGE-LIMITED

AREA(-70 dBm

at cell edge)


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158

Erlang is the unit of statistical resource use

Erlang Concept


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Average number of busy channelsduring the period of observation

(usually, the peak hour).

Erlang BAt any time, more than 1 user may request the same resource simultaneously. The use of such aresource is associated with a blocking rate.

Erlang C

When more than 1 user request at the same time, instead of rejecting the extra calls, there is aqueuing system.

Different Types of CellsEXTENDED-CELL:macro cell with system coverage

CONCENTRIC-CELL:macro cell with system coverage
http://d/SIVAPRESENTATION/Erlang%20Concept.ppt


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High sensitivity tointerference

Requires "secured"Frequency reuse pattern

High isolation frominterferences

A few Frequenciesintensively reused

MACRO-CELL:antenna radiating above roofs---> Wide Coverage ( 35 km)

MICRO-CELL:Antenna below the roofs---> small coverage

PICO-CELL:Antenna inside building---> Very small coverage

macro cell with system coverageextension ( 120 km) for coasts...

macro cell with system coveragelimitation inside another macro

Cell Patterns


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Cell Sectorization


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TRI OMNI BI

Omnidirectional Site Antennas


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Bi and Trisectorial Site Antennas


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Link Budgeting


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Calculation of the maximum coverage range of each cell in a specific environment.

Definition of planning tools parameters.

Based on the path loss calculation between the MS and the BS in both ways.

This calculation considers:

RF parameters of MS and BS,

system parameters (diversity gains...),

propagation parameters (shadowing), physical installation parameters (antenna height),

environment classification.


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- What is the maximum EIRP?

- What are the losses intransmission and reception?

- Is diversity used? - What is the minimumequivalent sensitivity?

- What is the maximumequivalent output power?

- What are the body losses?

- Beyond which distance the

communication will cut off?- Is indoor coverage

guaranteed?

- Is frequency hopping used?

EIRP:Equivalent Isotropic Radiated Power

Link Budget Parameters Overview


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Duplexer

Combiner

Power Amplifier

DLNA:Diversity Low Noise Amplifier

Specific Tx CableLosses

Tx PA OutputPower

Combiner losses

Rx Sensitivity

Rx Diversity Gain

DLNA conf.Standard conf.

Base Station

Tx PA Output Power

Other factors for MSBody LossesCommon cable losses

Propagation Parameters:

- Incar, Indoor penetration factors- Frequency 900, 1800, 1900 MHz- Antenna Height- Environment

Design Parameters:Overlapping margin

Rx Sensitivity

Antenna Gain

MS

Rx Sensitivity

Common cable Losses

Antenna Gain

Radio Link

Link Budget Parameters BTS TX Power Amplifier
http://d/SIVAPRESENTATION/Path%20Loss%20Statistical%20Methods.ppt


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2.5W PA 25W PA 35W PA 20W PA 30W PA

GSM 900 S2000LS2000ES4000 Indoor

S4000 Outdoor

S4000 Indoor S2000HS8000 IndoorS8000 Outdoor

DCS 1800 S2000L S4000 IndoorS2000ES2000HS4000 Outdoor

S4000 IndoorS8000 IndoorS8000 Outdoor

PCS 1900 S2000L

S2000E

S2000HS4000 IndoorS4000 Outdoor

S8000 Outdoor

Link Budget Parameters Combiners


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D

H2D

Hy/2

2-Way Hybrid Combiner with Duplexer

4.5 dB Loss

allows Synthesized Frequency Hopping

4-Way Cavity Combiner withDuplexer

allows Baseband Frequency Hopping

4.9 dB Loss

C C C C

D

TX TX TX TXTXTX

Link Budget Parameters Cable Losses


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At the BS, for a 7/8 foam dielectric coaxial cable:

4 dB/100 m (900 MHz),

6 dB/100 m (1800 MHz),

Common cable losses for 40 meters: 2.5 dB (900 MHz) and 3.5 dB (1800 MHz).

Jumpers (up and down the feeder)

0.5 dB (800 MHz),

1 dB (1800 MHz).

Link Budget Parameters BTS Antenna Gain


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Omnidirectional antenna

Default 6.5 V with 11 dBi gain

Directional antenna for trisectorial site

Default 65 H / 6.5 V with 18 dBi gain

Link Budget Parameters Mobile Station Parameters


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900 MHz 1800/1900 MHz

TX PA OutputPower

33 dBm (2W) 30 dBm (1W)

RX Sensitivity -102 dBm

-2 dBi for Handheld2 dBi for Car Kit

Body Loss

Antenna Gain

Common CableLoss

-100 dBm

0 dB for Handheld2 dB for Car Kit

3 dB for Handheld0 dB for Car Kit

Link Budget PresentationParameters

Frequency 1800 MHzAntenna Gain (65 )

18 dBi


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q y

Base Height 40.0 m

Mobile Height 1.5 m

Environment Urban

RX TX

Mobile

Antenna Gain-2 dB

Cable Loss0 dB

Output Power

Sensitivity

-100 dBm

30 dBm

Jumper Loss

Feeder Loss

Sensitivity

-110 dBm

3 dB

Options

Rx Diversity Gain: 5 dB

Overlapping Margin: 0 dB

Penetration Factor

Body Loss 3 dB

15 dB

Outdoor Minimum Field

95%: -80 dBm

Coverage Range

95%: 810 m

0.5 dB

Base Station

Max TX Output Power

RXm RXd

44.8 dBm

Coupling system

Tx loss4.5 dB

Link Budget Calculation: S8000 INDOOR: OPERATING FREQUENCY 1800 MHz


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BTS MSTX OUTPUT POWER 30.00 W (44.8dBm) 1.00 W (30.0dBm)COMBINER LOSSES 5.0 dB NoneRX SENSITIVITY -110.0 dBm -102.0 dBmRX SENSITIVITY +DIVERSITY -115.0 dBm NoneCOMMON CABLELOSSES 3.0 dB 0.0 dBANTENNA GAIN 18.0 dBm -2.0 dBm

BODY LOSSES 3.0 dBOVERLAPPING MARGIN 0.0 dBINDOOR PENETRATIONFACTOR 18.0 dB

Exercise 1: S8000 INDOOR: OPERATING FREQUENCY 1800 MHz

FadingExample of Field Strength Variation for GSM 1800


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-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Distance (m)

FieldStrength

(dBm)

Measurement

Free Space

Zoom onShort Term Fading

Long Term Fading

2 m

/2

Clutters


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Mobile Station (MS)


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( )

Hand portable unit

Contains Mobile Equipment(ME) and

Subscriber Identity Module (SIM)

gsm+overview 1

Documents