1.Oma000001 Gsm Fundamentals Issue3.2

7/31/2019 1.Oma000001 Gsm Fundamentals Issue3.2

1/103

Huawei Confidential. All Rights Reserved

ISSUE 3.2

OMA000001

GSM Fundamentals


2/103

Internal Use 2

Objectives

Upon completion this course, you will beable to:

Name the frequency spectrum used inGSM

Name the concept of frequency reused. Name the two different cell types and

understand why and when each wouldbe used.


3/103

Internal Use 3

Chapter 1 Basic Concept of Cellular

Mobile System

Chapter 2 GSM Network Components

Chapter 3 Terrestrial Interface

Chapter 4 Service Area And Number Planning

Chapter 5 Channels On Air Interface

Chapter 6 Radio Technologies

Chapter 7 The Future Development


4/103

Internal Use 4

GSM 900

The Frequency Spectrum

Total bandwidth: 25MHz

Bandwidth/channel: 200KHz

Channel availability: 124 ARFCN (1-124)


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Internal Use 5

DCS 1800

The Frequency Spectrum

Total bandwidth: 75MHz

Bandwidth/channel: 200KHz

Channel availability: 374 ARFCN (512-885)

95MHz spacing

Base Station Receive

1710 1785 1805 1880MHz

Base Station Transmit


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Internal Use 6

New standard

GSM 900

876 880 890 915 921 925 935 960

GSM 900EGSMRGSM RGSM EGSM

EGSMExtra 10MHz, therefore total available ARFCN become 174.

RGSMExtra 15MHz, therefore total available ARFCN become 199.


7/103Internal Use 7

Calculation of Carrier Frequencies

GSM900

Fuplink (n) = 890 + (0.2 x n) MHz

Fdownlink (n) = Fuplink (n) + 45MHz

Where, 1 < n < 124

GSM1800

Fuplink (n) = 1710.2 + (0.2 x (n-512)) MHz

Fdownlink (n) = Fuplink (n) + 95MHz

Where, 512 < n < 885


8/103Internal Use 8

Frequency spectrum

dB

Noise

floor

Frequencyf1 f2

-Bandwidth is from f1 to f2

-Clean signal can be obtained if only one user using this spectrum and the signal

energy must higher than the noise floor.

Wanted signal


9/103Internal Use 9

Frequency spectrum

dB

Noise

floor

f1 f2

-Interference occur when two signal are transmitting at the same frequency

spectrum.

-Signal with higher energy will win.

10dB

20dB

Wanted signal

Interfering

signal


10/103Internal Use 10

How to maximize the spectrum utilization

Adopt multiple access techniques

Adopt frequency reuse



GSM Multiple Access Methods

Frequency

Division Multiple

Access

Time Division

Multiple Access

GSM system

Time

ff

Time



GSM Multiple Access Method

dB

200kHz

frequency0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

200kHz

ARFCN 1 ARFCN 2

.8 Users/timeslots

Note: Max number of users can only support up to 8Ts x 124ARFCN=(992 users). [for GSM900]



Frequency Re-Use

Why need Frequency Re-Use?

Frequency resources are very expensive.

Frequency resources are very limited.

However maintain the quality of service.



Frequency Re-Use

How can we reuse frequency?

7(Site)X 1(Cell)Re-use 2

1

2

3

4

5

6

7



Frequency Reuse

How can we reuse frequency?Larger cluster size

Longer distance

between interferers

1

34

21

34

2

1

34

21

3 42

1

34

2

k=4

1

54

3

6

72

1

54

3

6

7 2

1

54

3

6

72

1

54

3

6

72

k=7

1

54

3

6

72

8

9 1

54

3

6

72

8

9

1

543

67

28

9

1

54

3

6

72

8

9 k=9

15

4

3

6

72

89

1011

12 15

4

3

6

72

89

1011

12

1

54

3

6

72

89

1011

12

k=12

1

32

1

3

21

3

2

1

32

1

3

2

k=3

Less interferenceBUT

Reduced capacity



Controlling Co-channel interference

Carried-to-co-channel interference ratio

C/I = 1.5(k2)

Where, k = Cluster size

e.g. k=3, C/I = 1.5(3)2 = 11.3 dB

k=4, C/I = 1.5(4)2 = 13.8 dB

Note: - GSM standard required C/I > 9 dB. Thats meanminimum number of reuse pattern is k=3.



Carrier to Interference ratio (C/I)

dB

Noise

floor

Frequencyf1

9dB

Wanted signal

Interfering signal/Co-

channel Signal

Note: In practical C/I should be greater than 12 dB



Frequency Re-Use

4(Site)X 3(Cell)

Re-use

5

1

9 6

10

2

7

3115

9

1

10

212

8

4

11

7

3

9

5

1

6



CELL

Omni

1

120degree

1

23

Omni-Directional Cells

120 Degree Sectors



Comparison between Omni / SectorisedCells

1 1

1

1

1

1

1

1

11

First tier

Second tier

Omni cells

14

32

32

14

32

14

32

14

32

14

32

120 deg.DirectionalAntennas

First tier

for first tier KI = 6 (theoretically) for first tier KI = 2 - 3

narrow beam antennas (e.g. 60)better than wide beam antennas (e.g.120)

Ex.

3x4



Controlling Co-channel interference

Hence,

C/I = 1.5 (K2) x S

Where, S = sectorization

e.g. for 3 Sectorization (4x3)

C/I = 1.5k2 x 3 = 4.5 K2

= 1.5x (4)2 x 3

= 10 log 72 = 18.6 dB

9

5

1


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Internal Use 22


Mobile System








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Internal Use 23

Objectives


Draw the structure of GSM

Identify the functions of each component


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Internal Use 24

AUC

MESIM

OMC

HLR

MSC/VLR

BTS BSC

PSTN

OSS

MS

NSS

BSS

EIR

GSM Network Components


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Internal Use 25

Mobile StationMS

International Mobile Equipment Identity

(IMEI) Mobile Equipment

MS=ME+SIM

International Mobile SubscriberIdentity (IMSI)

Subscriber Identity Module


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Internal Use 26

Subscriber Identity Module SIM

International Mobile Subscriber Identity(IMSI)

Temporary Mobile Subscriber Identity

(TMSI) Location Area Identity (LAI) Subscriber Authentication Key (Ki) Mobile Station International Standard

Data Network (MSISDN),

it is optional.

GSM


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Internal Use 27

Authentication

A3

=?

A3

RANDRANDKi Ki

MS NetworkUm interface

Accept /

reject?

SRES

SRES

Ki = authentication key

RAND = random number

SRES = Signal Response


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Internal Use 28

The Base Station

Controller BSC

The Base Transceiver

Station BTS

The Trans-coder TC

and Sub multiplexer(SM)

BTS

BSC

TC/SMBSS

MSC

Base Station Subsystem BSS


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Internal Use 29

Mobile Switching Center MSCHome Location Register HLRVisitor Location Register VLREquipment Identity Register EIRAuthentication Center AUCInter-Working Function IWF

Echo Cancellor EC

AUCHLR

MSC/VLR

PSTN

NSS

EIROMC

BSS

EC

IWF

The Network Switching System


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Internal Use 30

Mobile Service Switching Center MSC

Call Processing Operations and Maintenance

Support Inter-network & Inter-working

Billing


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Internal Use 31

Home Location Register HLR

Subscriber ID (IMSI and MSISDN) Current subscriber VLR (current location) Supplementary service information

Subscriber status (registered/deregistered) Authentication key and AuC functionality


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Internal Use 32

Visitor Location Register VLR

Mobile Status(IMSI detached/ attached)

Location Area Identity(LAI)

Temporary Mobile Subscriber Identity(TMSI)

Mobile Station Roaming Number(MSRN)

E i Id i R i EIR


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Internal Use 33

IMEIIs Checked against White List

IMEIIs Checked against Black/Grey List

If NOT found,checked againstGrey/Black List

If NOT found, checkedagainst White Listindications

If found, returns a Blackor Grey List indicator

White List

Black List

Grey List

Equipment Identity Register EIR

I W ki F i IWF


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Internal Use 34

Rate Conversion Protocol Adaptation

PSTN

MSC

EC IWF

Inter-Working Function IWF

O ti d M i t S b S t


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Internal Use 35

OSS(NMC)

M2000M2000

M2000

Region2

Region 1

Region 3

Operation and Maintenance Sub System

O ti d M i t C t OMC


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Internal Use 36

Operation and Maintenance Center OMC

OMC/iManager M2000: OMC assigned

specifically for GSM, CDMA & WCDMANEs.

OMC F ti l A hit t


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Internal Use 37

OMC Functional Architecture

OS

MMI

DB

Event/AlarmManagement

SecurityManagement

ConfigurationManagement

PerformanceManagement

FaultManagement


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Internal Use 38


Mobile System







Obj ti


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Internal Use 39

Objectives


Identify the protocols used on theterrestrial interfaces between theGSM system entities

GSM Interface


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Internal Use 40

HLR

VLR

MSC

EIR

AUC

EC IWF

TC

VLR

MSC

IWF EC

BTS BSCMS

B

H

F

G

A

E

C

D

Um Abis

GSM Interface

GSM Protocol


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Internal Use 41

GSM Protocol

SigL1: 2MBps Trunks


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Internal Use 42

HLR

MSC/VLR

EIR

AUC

EC

OMC

MSC/VLR

TC

IWF

EC

BSC PSTN

BTS BTS

SigL1: 2MBps Trunks

2MBps Trunks


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Internal Use 43

Typical Configuration

TS 0 TS 1-15 TS16 TS 17-31

TS = Time slot

TS# Used for

0

1-15

16

17-31

Frame Alignment /Error Checking /Signaling

Traffic

CCS7 Signaling (Other TS may also the used)

Traffic

2MBps Trunks

Abis (LAPD) Interfaces


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Internal Use 44

Abis (LAPD) Interfaces

FlagAddressControlInformationFrame check

SequenceFlag

last bit first bit

ITU Signaling System CCS7


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Internal Use 45

OSI Layers

7. Application

6. Presentation

5. Session

4. Transport

3. Network2. Link

1 Physical

CCS7 Levels

MTP Level 1 2 Mb/s Trunk

MTP Level 3

TUP

SCCP

BSSAP

(DTAP+BSSMAP)ISUP

MAP

TCAP

MTP Level 2

ITU Signaling System CCS7

Abbreviation of CCS7


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Internal Use 46

Abbreviation of CCS7

MTP Message Transfer Part

TCAP Transaction Capabilities Application Part

SCCP Signaling Connection Control Part

TUP Telephone User Part

ISUP ISDN User Part MAP Mobile Application Part

BSSAP Base Station System Application Part

BSSMAP BSS Management Application Part

DTAP Direct Transfer Application Part


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Internal Use 47


Mobile System







Objectives


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Internal Use 48

Objectives


Identify the system identificationnumber

Identify the of mobile identificationnumber

Identify the cell identificationnumber

Service Area


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Internal Use 49

Service Area

PLMN service area

......

System areaPLMN service area

MSC service area...

Location area...Base station area...

Radio cell

...... ......

MSC service area...

Location area...

Base station area...

Radio cell

PLMN service area

MSC/VLR Number


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Internal Use 50

MSC/VLR Number

The format is CC+NDC+LSPCC Country Code.For example: The CC of China is "86".

NDC National Destination Code.For example: The NDC of China Mobile is 139 138 137136 135.

LSP(locally significant part): is defined by Telecom operator.For example: 86-139-00311

CC NDC LSP

MSC/VLR number

HLR Number


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Internal Use 51

HLR Number

The format is CC+NDC+H0 H1 H2 H3 0000.CC Country Code.For example: The CC of China is "86".

NDC National Destination Code.For example: The NDC of China Mobile is 139138 137 136 135.

H0H1H2H3 is defined by Telecom operator.For example: 86-139-0666-0000.

LAI


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Internal Use 52

LAI

Location Area Identification

The LAI is the international code for a location area.

MCC Mobile Country Code It consists of 3 digits .For example: The MCC of China is "460"

MNC Mobile Network Code It consists of 2 digits .For example: The MNC of China Mobile is "00"

LAC Location Area Code It is a two bytes BCD code(hex).The value 0000 and FFFF is invalid.

For example: 460-00-0011

MCC MNC LAC

CGI


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Internal Use 53

CGI

The CGI is a unique international identification for a

cell

The format is LAI+CI

LAI: Location Area Identification

CI Cell Identity. This code uses two bytes BCD

code(hex) to identify the radio cells within an LAI.

For example : 460-00-0011-0001

CGI: Cell Global Identification

BSIC


54/103

Internal Use 54

BSIC

NCC PLMN network color code. It comprises 3 bit. Itallows various neighboring PLMNs to be distinguished.

BCC BTS color code. It comprises 3 bit. It allowsdistinctionbetween different radio frequency channels using the samefrequency in neighboring cells.

NCC BCC

BSIC

BSIC Base Station Identification Color Code)

MSISDN


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Internal Use 55

CC Country Code. For example: The CC of China is "86".

NDC National Destination Code. For example: The NDC ofChina Telecom is 139, 138, 137, 136, 135.

SN Subscriber Number. Format:H0 H1 H2 H3 ABCD

Example: 86-139-0666-1234

MSISDN

CC NDC SN

National (significant)Mobile number

Mobile station internationalISDN number

IMSI


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Internal Use 56

MCC Mobile Country Code It consists of 3 digits .For example: The MCC of China is "460"

MNC Mobile Network Code It consists of 2 digits .

For example: The MNC of China Telecom is "00" MSIN Mobile Subscriber Identification Number. H1H2H3 S ABCDEF

For example: 666-9777001NMSI National Mobile Subscriber Identification MNC and MSIN

form it together.For Example of IMSI : 460-00-666-9777001

Not more than 15 digits

3 digits 2 digits

IMSI

MCC MNC MSIN

NMSI

IMSI

TMSI


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Internal Use 57

The TMSI is assigned only after successful

subscriber authentication. The VLR controls the allocation of new TMSInumbers and notifies them to the HLR.

TMSI is used to ensure that the identity of themobile subscriber on the air interface is kept

secret. The TMSI consists of 4 bytes( 8 HEX numbers)

and determined by the telecom operator.

TMSI

TMSI: Temporary Mobile Subscriber Identification)

IMEI


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Internal Use 58

IMEI

TAC FAC SNR SP

IMEI

TAC Type approval code. It is administered by the typeapproval center.

FAC Final assembly code.It is administered by themanufacturer.

SNR Serial number.It is issued by the manufacturer of the MS.SP Not used.

IMEI: International Mobile Station Equipment Identification


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Internal Use 59


Mobile System







Objectives


60/103

Internal Use 60

Objectives


Understand the structure of multiframes

Name the 4 most commonly usedchannel combinations

Identify the types of physical

channels and logical channels

Physical and Logical Channels


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Internal Use 61

The physical channel is the medium over whichthe information is carriedThe logical channels consist of the informationcarried over the physical channel

00 1 2 3 4 5 6 7

TDMA FRAME

Timeslot

The information carried in one timeslot is called a burst

ys ca a d og ca C a e s

Burst Mapping on physical channel


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Internal Use 62

pp g p y

Burst (148 bits)GuardInterval

(8.25 bits)

0 7

TDMA frame = 4.615 ms

0

f s

7 0

s

7

577s

(156.25 bits)

BURST


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Internal Use 63

8bit 41 synchronousbits

36 encryptedbits 3bit 68.25bit

Tail bit Tail bit Guard intervalData

Random Access burst (RACH): Used in MS initial access

Guard interval

3bit 142bit 3bit 8.25bit

Tail bit Tail bitData

Frequency correction burst (FCH): Used in frequency synchronization

between MS and BTS

3bit 39 encryptedbits

39 encryptedbits

3bit 8.25bit

Tail bit Tail bit Guard intervalDataData

64 synchronous bits

Synchronous burst (SCH): Used in timing synchronization between MSand BTS

Burst


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Internal Use 64

3bit 142 modulation bits 3bit 8.25bit

Tail bit Tail bit Guard interval

Dummy burst (BCH): Used in transmission of filling framesby BTS at timeslots when there is no information delivered

3bit 57 encrypted bits 57 encrypted bits 3bit 8.25bit

Tail bit Tail bit Guard intervalDataData

26bit1 1

Training sequence

Framestealing

flag

Normal burst (TCH): Used to carry the information of the traffic channeland the control channel.

Logical Channel Type


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Internal Use 65

g yp

Broadcast control channel

(BCCH) Control channelCommon control channel

(CCCH)

Voice channel

(TCH)

FCH SCH BCCH

(system information)

TCH/FAGCH RACH SDCCH FACCH

SACCH

TCH/H

TCH/9.6F

TCH/ 4.8F, H

TCH/ 2.4F, H

PCH

Common channel

(CCH)

Dedicated channel

(DCH)

Logical channel

GSM900 and DCS1800 have the same logical channel category

Traffic Channel


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Internal Use 66

TCHTraffic Channels

Speech

TCH/FS

Data

TCH/HS

TCH/9.6 TCH/2.4

TCH/4.8

Normal Burst

TCH Traffic ChannelTCH/FS Full rate Speech ChannelTCH/HS Half rate Speech ChannelTCH/9.6 Data Channel 9.6kb/sTCH/4.8 Data Channel 4.8kb/sTCH/2.4 Data Channel 2.4Kb/s

Control Channel


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Internal Use 67

FCCH

SCH

CCH Control Channels

DCCH

SDCCH

BCCH

BCCH Synch. CH.ACCH

SACCHFACCH CCCH

RACH

CBCH

PCH/AGCH

Broadcast Control Channel BCCHCommon Control Channel CCCHDedicated Control Channel DCCHAssociated Control Channel ACCH

Broadcast Control Channel BCCH


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Internal Use 68

CCH

BCCHdownlink only

BCCHSynch.

Channels

SCH FCCH

The information carried on the

BCCH is monitored by the mobile

periodically when it is switched

on and not in a call

BCCH:Broadcast Control Channel

FCCH: Frequency Correction

Channel

SCH: Synchronization Channel

Common Control Channel CCCH


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Internal Use 69

CCH

CCCH

RACHuplink

CBCHdownlink

PCH/AGCHdownlink

The CCCH is responsible fortransferring control informationbetween all mobiles and theBTS.

RACH: Random Access ControlChannel

PCH: Paging Channel

AGCH: Access Grant ControlChannel

CBCH:Cell Broadcast Channel

Dedicated Control Channel DCCH


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Internal Use 70

CCH

DCCH

SDCCH

FACCH SACCH

DCCH is assigned to a singlemobile connection for call setupor for measurement and handoverpurpose.

SDCCH: Standalone DedicatedControl ChannelACCH: Associated ControlChannelSACCH: Slow Associated ControlChannelFACCH:Fast Associated ControlChannel

ACCH

How to use these channel?


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Internal Use 71

Search for frequency correction pulse

Search for synchronous pulse

Unscramble system information

Snoop into paging message

Send access pulse

Allocate signaling channel

Set up the call

Allocate voice channelConversation

Release the call

FCCH

SCH

BCCH

PCH

RACH

AGCH

SDCCH

FACCHTCH

FACCH

Power-off state

Idle state

Dedicated mode

Idle state

Call Setup Flow


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Internal Use 72

MS BTS BSC MSCChannel_req Channel_Required

Channel_Active

Channel_Active_Ack

IMMEDIATE ASSIGN COMMAND

Establish_IND(CM Service Req)First SABM

CM Service Accepted

CR(Complete_L3_information)

CC

Setup

Call Processing

ASSIGNMENT COMMAND

First SABM Establish_IND

Channel_Active

Channel_Active_Ack

Assignment_Req

Assignment_CMPASSIGNMENT CMP

Alerting

Connect

Connect AckDisconnect

ReleaseRelease Complete

Clear_CMD

Clear_CMP

Conversation

SABM: Set asynchronousbalanced mode command--Initial access frame

UA: Unnumberedacknowledgement response

GSM Multiframe


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Internal Use 73

TDMA Frames

0 1

0 1 2 43 46 47 48 5049

51 Frame Multiframes (235.3ms)

0 1 10

CONTROL CHANNELS

2 3 4 5 6 7 2 3 5 764

GSM Logical Channel


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Internal Use 74

Channel CombinationBCH combination BCCH + CCCH

DCH combination SDCCH8 + SACCH8

Combined Channel Combination BCCH +CCCH +SDCCH4 + SACCH4

TCH combination TCH8/FACCH + SACCH

BCCH/CCCH Multiframe


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Internal Use 75

F SB B B B

C C C C F F S C C C C C C C CI

Downlink

0 10 20 30 40 50

S C C .. F S C C .. F S C C ..

R R R R R R R R R R R R R R R R R R R R R R

Uplink

R R R .. R R R ..R R R ..

0 10 20 30 40 50

F = FCCH (Frequency)S = SCH (Sync.)C = CCCH (Common)I = IdleR = RACH (Random)

SDCCH Multiframe


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Internal Use 76

D0 D1 D7 A0 A3 I I I

D0 D1 D6 D7 A4 A7 I I I

A5 A6 D0 D7 A0A7 I I I

A1 A2 D0 D7 A4A3 I I I

Downlink

0 7 24 32 44 50

0 7 12 15 44 50

Uplink

D = SDCCH/8 (Dedicated)A = SACCH/C8(Associated) I = Idle

D6

Timeslots and TDMA Frames


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Internal Use 77

Higher Capacity Cell

Broadcast Traffic

Dedicated

Traffic00 1 2 3 4 5 6 7

00 1 2 3 4 5 6 7

Low Capacity Cell

Combined Traffic

00 1 2 3 4 5 6 7

Combined Multiframe


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Internal Use 78

BSF C CSF C D0SF D1 D2SF D3 A0S A1F I

BSF C CSF C D0SF D1 D2SF D3 A2S A3F I

0 2 6 10 20 30 40 50

Downlink

D3 RR A2 A3 RR R D0 D1 RR D2R

0 4 6 10 20 30 40 50

D3 RR A2 A3 RR R D0 D1 RR D2R

Uplink

R = RACH (Random) B = BCCH (Broadcast)F = FCCH (Frequency) S = SCH (Sync.)C = CCCH (Common) D = SDCCH/4 (Dedicated)A = SACCH/4 (Associated) I = Idle

GSM Multiframe


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Internal Use 79

TDMA Frames

0 1

0 1 2 43 21 22 23 2524

26 Frame Multiframe (120ms)

0 1 10

TRAFFIC CHANNELS

2 3 4 5 6 7 2 3 5 764

TCH Multiframe


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Internal Use 80

IDLE

SACCH

IDLE

SACCH

25

12

0

This is used to transmit a

Traffic Channel Combination

(TCH/ SACCH/FACCH). The

FACCH is not showed in the

diagram as it does not receiveits own time allocation. The

FACCH steals a time period

from the TCH is required.

The 13th frame is used by the

SACCH which carriers linkcontrol information to and

from the mobile and BTS.

The 26th frame is idle.

Downlink Uplink

25

12

0


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Internal Use 81


Mobile System







Objectives


82/103

Internal Use 82

On completion of this section you willbe able to know about the followingradio technologies :

GMSK Modulation Techniques

Power Control

VAD, DTX, DRX

Diversity

Frequency Hopping

Modulation Techniques


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Internal Use 83

phase modulation can be implemented easily for digital

signals, this is the method which is used for the GSM

air interfaces. Phase Modulation is known as Phase

Shift Keying when applied to digital signals

Amplitude Modulation (AM)

Frequency Modulation (FM)

Phase Modulation (PM)

Gaussian Minimum Shift Keying (GMSK)


84/103

Internal Use 84

1 0 0 1 1

Gaussian

Digital Filter

GMSK

Modulator

Gaussian Minimum Shift Keying

(GMSK)

Timing Advance (TA)


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Internal Use 85

burst delay t (e.g. PCH)

burst delay t e.g

(RACH)

TA

The mobile phone should

send the signal in advance!! Note: Max TA = 2t = 1/2*3.7s/bit*63bit*C=35km,

Not Applicable to RACH Bursts.

0 1 2 3 4 5 6 7TX

RX0 1 2 3 4 5 6 70

Total delay for round trip is t + t = 2t

Battery Life


86/103

Internal Use 86

Power Control

Voice Activity Detection VAD

Discontinuous Transmission DTX

Discontinuous Reception DRX

Power Control


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Internal Use 87

Saves radio battery powerReduces co-channel andadjacent channel interference

8W

0.8W

5W

Both Uplink and Downlinkpower settings can becontrolled independentlyand individually.

VAD & DTX


88/103

Internal Use 88

Encoding the speechsilences at a rate of500 bit/s rather than

the full 13Kb/s.If the mobile does not

transmit duringsilence there is areduction in theoverall power

output requirement

Without DTX

With DTX

ComfortNoise

DTX


89/103

Internal Use 89

Prolongbattery lifeand reduceinterference

DTX: Discontinuous Transmission

Shut off the transmission when no speech detected;

Only transmit SID frames

The transcoder at the RX terminal produces comfortable noise based onSID background noise.

Improvement on the C/I ratio.

VAD: Voice Activity Detection

Implemented in the transcoder.

Note: DTX is not used on a BCCH carrierand measurements must based no Sub

value.

DRX


90/103

Internal Use 90

DRX allows the mobile station to effectively switch offduring times when reception is deemed unnecessary.

P P P P P P BCCH P P

BCCH Multiframe P = Paging Channel

MS Beingpaged

MS inlisten mode

MS receive System

information

MS inlisten mode

DRX example


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Internal Use 91

Multipath Fading


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Internal Use 92

Diversity

FrequencyHopping

Time Dispersion

Diversity


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Internal Use 93

When diversity is implemented twoantennas are situated at thereceiver. These antennas areplaced several wavelengthsapart to ensure minimumcorrelation between the tworeceive paths.

The two signals are then

combined, this ensures that alow signal strength is less likelyto occur.

Compare oradd signals

Resultant Signal

Approx. 10

wavelengths

Frequency Hopping


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Internal Use 94

Synthesizer Hopping:each

timeslot on a giventransceiver can transmit ata different frequency

Baseband Hopping: eachtransceiver stays at the

same frequency and thedata is switched to theappropriate transceiver.

Each time the BTS or mobile transmits a burst, itdoes so on a different RF carrier frequency.

time

frequency

Frequency Hopping


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Vs

F1F3

F2

F1

F1 F1

Without FH With FH


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Mobile System







Objectives


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On completion of this section youwill be able to know :

State the future development of digitalcellular mobile system

GSM User World Wide


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GSM will stay in the Lead, all professional MarketForecasts say

GSM users world wide in millions

Voice and Data Service


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Serviceamout

i

Data

Vi

Today2000

Mobile Communication and Internet


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100

200

300

400

500

600

700

1995199619971998199920002

Mobile Internet

million

GSM Develop Path


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1999 2000 2001

57.6kbps

115kbps

384kbps

2Mbps

GSM

HSCSD

GPRS

EDGE

IMT-2000

9.6kbps

2G

2.5G

3G

Summary


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Summary

Basic Concepts of Cellular Mobile System

GSM Network Components

Terrestrial Interface

Service Area and Number Planning

Channels on The Air Interface

Radio Technologies

The Future Development


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1.Oma000001 Gsm Fundamentals Issue3.2

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