Huawei Gsm Fundamentals

Huawei Confidential. All Rights Reserved

ISSUE 3.2

OMA000001GSM Fundamentals

2Internal Use

ObjectivesObjectives

Upon completion this course, you will be able to:

Name the frequency spectrum used in GSM

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

understand why and when each would be used.

Name the frequency spectrum used in GSM

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

understand why and when each would be used.

3Internal Use

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

4Internal Use

GSM 900GSM 900

The Frequency SpectrumThe Frequency Spectrum

Total bandwidth: 25MHz

Bandwidth/channel: 200KHz

Channel availability: 124 ARFCN (1-124)

5Internal Use

DCS 1800DCS 1800

The Frequency SpectrumThe 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

6Internal Use

New standardNew standard

GSM 900

876 880 890 915 921 925 935 960

GSM 900EGSM RGSM RGSM EGSM

EGSM – Extra 10MHz, therefore total available ARFCN become 174.

RGSM – Extra 15MHz, therefore total available ARFCN become 199.

7Internal Use

Calculation of Carrier FrequenciesCalculation 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

8Internal Use

Frequency spectrumFrequency 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

9Internal Use

Frequency spectrumFrequency 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

10Internal Use

How to maximize the spectrum utilizationHow to maximize the spectrum utilization

Adopt multiple access techniques Adopt frequency reuse

11Internal Use

GSM Multiple Access MethodsGSM Multiple Access Methods

Frequency Division Multiple

AccessTime Division

Multiple Access

GSM system

Time

ff

Time

12Internal Use

GSM Multiple Access MethodGSM 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]

13Internal Use

Frequency Re-Use

Why need Frequency Re-Use?Why need Frequency Re-Use?

• Frequency resources are very expensive.

• Frequency resources are very limited.

• However maintain the quality of service.

14Internal Use

Frequency Re-UseFrequency Re-Use

How can we reuse frequency?How can we reuse frequency?

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

1

2

3

4

5

6

7

15Internal Use

Frequency ReuseFrequency Reuse

How can we reuse frequency?How can we reuse frequency?Larger cluster size

Longer distance between interferers

13

42 1

342

13

42

13

42

13

42

k=4

15

4

367

2

15

4

367

2

15

4

367

2

15

4

367

2

k=7

15

4

367

28

9 15

4

367

28

9

15

4

367

28

9

15

4

367

28

9 k=9

15

4

367

28

910

1112 1

54

367

28

910

1112

15

4

367

28

910

1112

k=12

13

213

213

2

13

213

2

k=3

Less interferenceBUT

Reduced capacity

16Internal Use

Controlling Co-channel interferenceControlling 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. That’s mean minimum number of reuse pattern is k=3.

17Internal Use

Carrier to Interference ratio (C/I)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

18Internal Use

Frequency Re-UseFrequency Re-Use

4(Site)X 3(Cell)

Re-use

5

1

9 6

10

2

7

3

115

9

1

10

212

8

4

11

7

3

9

5

1

6

19Internal Use

CELLCELL

Omni

1

120degree

1

23

Omni-Directional CellsOmni-Directional Cells

120 Degree Sectors120 Degree Sectors

20Internal Use

Comparison between Omni / Sectorised Comparison between Omni / Sectorised CellsCells

1 1

1

1

1

1

1

1

11

First tier

Second tier

Omni cells

1 43

23

2

1 43

2

1 43

2

1 43

2

1 43

2

120 deg. Directional Antennas

First tier

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

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

Ex.3x4

21Internal Use

Controlling Co-channel interferenceControlling 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

22Internal Use








23Internal Use



Draw the structure of GSM

Identify the functions of each component

24Internal Use

AUCAUC

MEME SIMSIM

OMCOMC

HLRHLR

MSC/VLRMSC/VLR

BTSBTS BSCBSC

PSTN

OSS

MS

NSS

BSS

EIREIR

GSM Network ComponentsGSM Network Components

25Internal Use

Mobile Station—MSMobile Station—MS

International Mobile Equipment Identity (IMEI)

– Mobile Equipment

MS=ME+SIMMS=ME+SIM

International Mobile Subscriber Identity (IMSI)

– Subscriber Identity Module

26Internal Use

Subscriber Identity Module – SIMSubscriber Identity Module – SIM


Temporary Mobile Subscriber Identity (TMSI)

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

Data Network (MSISDN), it is optional.


Temporary Mobile Subscriber Identity (TMSI)

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

Data Network (MSISDN), it is optional.

GS

M

27Internal Use

AuthenticationAuthentication

A3A3

=?=?

A3A3

RANDRANDKi Ki

MSMS NetworkNetworkUm interface

Accept / reject?

SRES

SRES

Ki = authentication key

RAND = random number

SRES = Signal Response

28Internal Use

The Base Station

Controller – BSC The Base Transceiver

Station – BTS The Trans-coder – TC

and Sub multiplexer

(SM)

The Base Station

Controller – BSC The Base Transceiver

Station – BTS The Trans-coder – TC

and Sub multiplexer

(SM)

BTSBTS

BSCBSC

TC/SMTC/SMBSS

MSC

Base Station Subsystem – BSSBase Station Subsystem – BSS

29Internal Use

Mobile Switching Center – MSC Home Location Register – HLR Visitor Location Register – VLR Equipment Identity Register – EIR Authentication Center – AUC Inter-Working Function – IWFEcho Cancellor – EC

Mobile Switching Center – MSC Home Location Register – HLR Visitor Location Register – VLR Equipment Identity Register – EIR Authentication Center – AUC Inter-Working Function – IWFEcho Cancellor – EC

AUCAUCHLRHLR

MSC/VLRMSC/VLR

PSTN

NSS

EIREIROMC

BSS

ECEC

IWFIWF

The Network Switching SystemThe Network Switching System

30Internal Use

Mobile Service Switching Center – MSC Mobile Service Switching Center – MSC

Call Processing Operations and Maintenance

Support Inter-network & Inter-working Billing

Call Processing Operations and Maintenance

Support Inter-network & Inter-working Billing

31Internal Use

Home Location Register – HLR 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

Subscriber ID (IMSI and MSISDN) Current subscriber VLR (current location) Supplementary service information Subscriber status (registered/deregistered) Authentication key and AuC functionality

32Internal Use

Visitor Location Register – VLR Visitor Location Register – VLR

Mobile Status(IMSI detached/ attached)

Location Area Identity(LAI)

Temporary Mobile Subscriber Identity(TMSI)

Mobile Station Roaming Number(MSRN)

Mobile Status(IMSI detached/ attached)

Location Area Identity(LAI)

Temporary Mobile Subscriber Identity(TMSI)

Mobile Station Roaming Number(MSRN)

33Internal Use

IMEIIs Checked against White List

IMEIIs Checked against Black/Grey List

If NOT found, checked against Grey/Black List

If NOT found, checked against White List indications

If found, returns a Black or Grey List indicator

•White List•Black List•Grey List

Equipment Identity Register – EIR Equipment Identity Register – EIR

34Internal Use

• Rate Conversion• Protocol Adaptation

PSTN

MSCMSC

ECEC IWF

Inter-Working Function – IWFInter-Working Function – IWF

35Internal Use

OSS(NMC)

M2000M2000

M2000

Region2

Region 1

Region 3

Operation and Maintenance Sub SystemOperation and Maintenance Sub System

36Internal Use

Operation and Maintenance Center – OMC Operation and Maintenance Center – OMC

OMC/iManager M2000: OMC assigned specifically for GSM, CDMA & WCDMA NEs.

37Internal Use

OMC Functional ArchitectureOMC Functional Architecture

OS

MMI

DB

Event/AlarmManagement

SecurityManagement

ConfigurationManagement

Performance Management

Fault Management

38Internal Use








39Internal Use



Identify the protocols used on the terrestrial interfaces between the GSM system entities

40Internal Use

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 InterfaceGSM Interface

41Internal Use

CM

MM

RR

LAPDm

SigL1

L3

L2

L1

MS

RR BTSM

LAPDm

SigL1

LAPD

SigL1

LAPD

SigL1

BTSM

RR

SCCP

MTP

BSSMAP

CM

MM

BSSMAP

SCCP

MTP

MSCBSCBTS

Um½Ó¿Ú A½Ó¿ÚAbis½Ó¿Ú

GSM ProtocolGSM Protocol

42Internal Use

HLR

MSC/VLR

EIRAUC

EC

OMC

MSC/VLR

TC

IWF

EC

BSC PSTN

BTSBTS BTS

SigL1: 2MBps TrunksSigL1: 2MBps Trunks

43Internal Use

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 Trunks2MBps Trunks

44Internal Use

Abis (LAPD) InterfacesAbis (LAPD) Interfaces

FlagAddressControlInformationFrame check Sequence

Flag

last bit first bit

45Internal Use

OSI Layers

7. Application

6. Presentation

5. Session

4. Transport

3. Network

2. 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 ITU Signaling System CCS7

46Internal Use

Abbreviation of CCS7Abbreviation 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

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

47Internal Use








48Internal Use



Identify the system identification number

Identify the of mobile identification number

Identify the cell identification number

49Internal Use

Service AreaService Area

PLMN service area

......

System area PLMN 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

50Internal Use

MSC/VLR NumberMSC/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 、 137 、 136 、 135.

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

CC NDC LSP

MSC/VLR number

51Internal Use

HLR NumberHLR Number

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


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

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


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

52Internal Use

LAILAI

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 ： 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

53Internal Use

CGICGI

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

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

54Internal Use

BSICBSIC

NCC ： PLMN network color code. It comprises 3 bit. It allows various neighboring PLMNs to be distinguished.BCC ： BTS color code. It comprises 3 bit. It allows distinction between different radio frequency channels using the same frequency in neighboring cells.

NCC ： PLMN network color code. It comprises 3 bit. It allows various neighboring PLMNs to be distinguished.BCC ： BTS color code. It comprises 3 bit. It allows distinction between different radio frequency channels using the same frequency in neighboring cells.

NCC BCC

BSIC

BSIC （ Base Station Identification Color Code)

55Internal Use

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

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

SN ： Subscriber Number. Format:H0 H1 H2 H3 ABCDExample: 86-139-0666-1234

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

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

SN ： Subscriber Number. Format:H0 H1 H2 H3 ABCDExample: 86-139-0666-1234

MSISDNMSISDN

CC NDC SN

National (significant)Mobile number

Mobile station internationalISDN number

56Internal Use

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

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 IMSI

57Internal Use

The TMSI is assigned only after successful subscriber authentication.

The VLR controls the allocation of new TMSI numbers and notifies them to the HLR.

TMSI is used to ensure that the identity of the mobile subscriber on the air interface is kept secret.

The TMSI consists of 4 bytes( 8 HEX numbers) and determined by the telecom operator.

The TMSI is assigned only after successful subscriber authentication.

The VLR controls the allocation of new TMSI numbers and notifies them to the HLR.

TMSI is used to ensure that the identity of the mobile subscriber on the air interface is kept secret.

The TMSI consists of 4 bytes( 8 HEX numbers) and determined by the telecom operator.

TMSITMSI

TMSI: Temporary Mobile Subscriber Identification)

58Internal Use

IMEIIMEI

TAC FAC SNR SP

IMEI

TAC ： Type approval code. It is administered by the type approval center.

FAC ： Final assembly code.It is administered by the manufacturer.

SNR ： Serial number.It is issued by the manufacturer of the MS.

SP ： Not used.

TAC ： Type approval code. It is administered by the type approval center.

FAC ： Final assembly code.It is administered by the manufacturer.

SNR ： Serial number.It is issued by the manufacturer of the MS.

SP ： Not used.

IMEI: International Mobile Station Equipment Identification

59Internal Use








60Internal Use



Understand the structure of multi frames

Name the 4 most commonly used channel combinations

Identify the types of physical channels and logical channels

61Internal Use

The physical channel is the medium over which the information is carriedThe logical channels consist of the information carried over the physical channel

The physical channel is the medium over which the information is carriedThe logical channels consist of the information carried over the physical channel

00 1 2 3 4 5 6 7

TDMA FRAME

Timeslot

The information carried in one time slot is called a “burst”

The information carried in one time slot is called a “burst”

Physical and Logical ChannelsPhysical and Logical Channels

62Internal Use

Burst Mapping on physical channelBurst Mapping on physical channel

Burst (148 bits)Burst (148 bits)Guard

Interval

(8.25 bits)

Guard

Interval

(8.25 bits)

0 7

TDMA frame = 4.615 ms

0

f s7 0

s7

577µs (156.25 bits)

63Internal Use

BURSTBURST

8bit 41 synchronous bits

36 encrypted bits 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 encrypted bits

39 encrypted bits

3bit 8.25bit

Tail bit Tail bit Guard intervalDataData

64 synchronous bits

• Synchronous burst (SCH): Used in timing synchronization between MS and BTS

64Internal Use

BurstBurst

3bit 142 modulation bits 3bit 8.25bit

Tail bit Tail bit Guard interval

• Dummy burst (BCH): Used in transmission of filling frames by 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

Frame stealing

flag

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

65Internal Use

Logical Channel TypeLogical Channel Type

Broadcast control channel (BCCH) Control channel

Common control channel (CCCH)

Voice channel(TCH)

FCH SCH BCCH(system information)

TCH/FAGCH RACH SDCCH FACCH

SACCH

TCH/H

TCH/9.6FTCH/ 4.8F, HTCH/ 2.4F, H

PCH

Common channel (CCH)

Dedicated channel (DCH)

Logical channel

GSM900 and DCS1800 have the same logical channel category

66Internal Use

Traffic ChannelTraffic Channel

TCHTraffic Channels

Speech

TCH/FS

Data

TCH/HSTCH/9.6 TCH/2.4

TCH/4.8

Normal Burst

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

67Internal Use

FCCHSCH

CCH Control Channels

DCCH

SDCCH

BCCH

BCCH Synch. CH.ACCH

SACCHFACCH CCCH

RACHCBCH

PCH/AGCH

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

Control ChannelControl Channel

68Internal Use

CCH

BCCH downlink only

BCCH Synch.

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

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

Broadcast Control Channel – BCCHBroadcast Control Channel – BCCH

69Internal Use

CCH

CCCH

RACHuplink

CBCH downlink

PCH/AGCHdownlink

The CCCH is responsible for transferring control information between all mobiles and the BTS.

RACH: Random Access Control Channel

PCH: Paging Channel

AGCH: Access Grant Control Channel

CBCH:Cell Broadcast Channel

The CCCH is responsible for transferring control information between all mobiles and the BTS.

RACH: Random Access Control Channel

PCH: Paging Channel

AGCH: Access Grant Control Channel

CBCH:Cell Broadcast Channel

Common Control Channel – CCCHCommon Control Channel – CCCH

70Internal Use

CCH

DCCH

SDCCH

FACCH SACCH

DCCH is assigned to a single mobile connection for call setup or for measurement and handover purpose.SDCCH: Standalone Dedicated Control Channel ACCH: Associated Control Channel SACCH: Slow Associated Control Channel FACCH:Fast Associated Control Channel

DCCH is assigned to a single mobile connection for call setup or for measurement and handover purpose.SDCCH: Standalone Dedicated Control Channel ACCH: Associated Control Channel SACCH: Slow Associated Control Channel FACCH:Fast Associated Control Channel

ACCH

Dedicated Control Channel – DCCH Dedicated Control Channel – DCCH

71Internal Use

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 channel

Conversation

Release the call

FCCH

SCH

BCCH

PCH

RACH

AGCH

SDCCH

FACCH

TCH

FACCH

Power-off state

Idle state

Dedicated mode

Idle state

How to use these channel?How to use these channel?

72Internal Use

Call Setup FlowCall Setup Flow

MS BTS BSC MSCChannel_req Channel_Required

Channel_Active

Channel_Active_Ack

IMMEDIATE ASSIGN COMMANDEstablish_IND(CM Service Req)First SABM

CM Service Accepted

CR(Complete_L3_information)

CC

Setup

Call Processing

ASSIGNMENT COMMANDFirst SABM Establish_IND

Channel_ActiveChannel_Active_Ack

Assignment_Req

Assignment_CMPASSIGNMENT CMP

Alerting

Connect

Connect Ack

Disconnect

Release

Release CompleteClear_CMDClear_CMP

Conversation

SABM: Set asynchronous balanced mode command--Initial access frame

UA: Unnumbered acknowledgement response

73Internal Use

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 MultiframeGSM Multiframe

74Internal Use

GSM Logical ChannelGSM Logical Channel

Channel CombinationBCH combination – BCCH + CCCH

DCH combination – SDCCH8 + SACCH8

Combined Channel Combination – BCCH +

CCCH +SDCCH4 + SACCH4

TCH combination – TCH8/FACCH + SACCH

75Internal Use

BCCH/CCCH MultiframeBCCH/CCCH Multiframe

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 = Idle R = RACH (Random)

76Internal Use

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

SDCCH MultiframeSDCCH Multiframe

77Internal Use

Timeslots and TDMA FramesTimeslots and TDMA Frames

Higher Capacity Cell

Broadcast TrafficDedicated

Traffic00 1 2 3 4 5 6 7

00 1 2 3 4 5 6 7

Low Capacity Cell

Combined Traffic00 1 2 3 4 5 6 7

78Internal Use

Combined MultiframeCombined Multiframe

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

79Internal Use

GSM MultiframeGSM Multiframe

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

80Internal Use

TCH MultiframeTCH Multiframe

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 receive its own time allocation. The FACCH steals a time period from the TCH is required.

The 13th frame is used by the SACCH which carriers link control information to and from the mobile and BTS.

The 26th frame is idle.

This is used to transmit a Traffic Channel Combination (TCH/ SACCH/FACCH). The FACCH is not showed in the diagram as it does not receive its own time allocation. The FACCH steals a time period from the TCH is required.

The 13th frame is used by the SACCH which carriers link control information to and from the mobile and BTS.

The 26th frame is idle.

Downlink Uplink25

12

0

81Internal Use








82Internal Use


On completion of this section you will be able to know about the following radio technologies :

GMSK Modulation Techniques

Power Control

VAD, DTX, DRX

Diversity

Frequency Hopping

83Internal Use

Modulation TechniquesModulation Techniques

– 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

– 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)

84Internal Use

Gaussian Minimum Shift Keying (GMSK) Gaussian Minimum Shift Keying (GMSK)

1 0 0 1 1

GaussianDigital Filter

GMSK Modulator

Gaussian Minimum Shift Keying

(GMSK)

85Internal Use

Timing Advance (TA)Timing Advance (TA)

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*3.7μs/bit*63bit*C=35km,

Not Applicable to RACH Bursts.

0 1 2 3 4 5 6 7TX

RX0 1 2 3 4 5 6 7

0

0

0

Total delay for round trip is t + t = ‘2t’

86Internal Use

Battery LifeBattery Life

Power ControlPower Control

Voice Activity Detection – VAD

Discontinuous Transmission – DTX

Discontinuous Reception – DRX

87Internal Use

Power ControlPower Control

Saves radio battery powerReduces co-channel andadjacent channel interference

8W

0.8W

5W

Both Uplink and Downlink power settings can be controlled independently and individually.

88Internal Use

VAD & DTXVAD & DTX

Encoding the speech silences at a rate of 500 bit/s rather than the full 13Kb/s.

If the mobile does not transmit during ‘silence’ there is a reduction in the overall power output requirement

Without DTX

With DTX

Comfort Noise

89Internal Use

DTXDTX

Prolong battery life and reduce interference

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 on

SID background noise. Improvement on the C/I ratio.

VAD: Voice Activity Detection Implemented in the transcoder.

Note: DTX is not used on a BCCH carrier and measurements must based no Sub value.

90Internal Use

DRXDRX

DRX allows the mobile station to effectively “switch off” during times when reception is deemed unnecessary.

P P P P P P BCCH P P

BCCH Multiframe P = Paging Channel

MS Being paged

MS in listen mode

MS receive System

information

MS in listen mode

91Internal Use

DRX exampleDRX example

92Internal Use

Multipath FadingMultipath Fading

•Diversity

•Frequency Hopping

Time Dispersion

93Internal Use

DiversityDiversity

When diversity is implemented two antennas are situated at the receiver. These antennas are placed several wavelengths apart to ensure minimum correlation between the two receive paths.

The two signals are then combined, this ensures that a low signal strength is less likely to occur.

Compare oradd signals

Resultant Signal

Approx. 10 wavelengths

94Internal Use

Frequency HoppingFrequency Hopping

Synthesizer Hopping:each timeslot on a given transceiver can transmit at a different frequency

Baseband Hopping: each transceiver stays at the same frequency and the data is switched to the appropriate transceiver.

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

time

frequency

95Internal Use

Frequency HoppingFrequency Hopping

Vs

F1F3

F2

F1

F1 F1

Without FH With FH

96Internal Use








97Internal Use


On completion of this section you will be able to know :

State the future development of digital cellular mobile system

98Internal Use

GSM will stay in the Lead, all professional Market Forecasts say

0

50

100

150

200

250

300

1996 1997 1998 1999 2000 2001

GSM users world wide in millions

GSM User World WideGSM User World Wide

99Internal Use

Service amout

Time

Data

Voice

Today 2000

Voice and Data ServiceVoice and Data Service

100Internal Use

Mobile Communication and Internet Mobile Communication and Internet

100200300400500600700

1995 1996 1997 1998 1999 2000 2001

Mobile Internet

million

101Internal Use

1999 2000 2001

57.6 kbps

115 kbps

384kbps

2Mbps

GSM

HSCSD

GPRS

EDGE

IMT-2000

9.6 kbps

2G

2.5G

3G

GSM Develop PathGSM Develop Path

102Internal Use

SummarySummary

SummarySummary

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

Huawei Confidential. All Rights Reserved

Huawei Gsm Fundamentals

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