huawei gsm principles

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GSM Principles


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Objectives

Upon completion of this course, you will be able to:

Grasp basic idea of GSM system such as frequency spectrum,

frequency reuse etc.

Grasp the structure of the GSM system and the protocol used.

Grasp certain numbers that refer to BSS

Grasp the 4 kinds of channel combination and understand the idea

of multi-frame.

Know some radio techniques

Get the idea of EDGE


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References

BSS Feature Description

BSS Signaling Analysis Manual

BSC Technical Manual


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Contents

1. GSM System Overview

2. GSM Network Structure

3. Service Area and Number Planning

4. Channels on the Wireless Interface

5. Radio Techniques

6. GPRS & EDGE Introduction


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Contents





5. Radio Techniques



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GSM system overview

The GSM system is a frequency- and time-division cellular system,

each physical channel is characterized by a carrier frequency and a

time slot number

Cellular systems are designed to operate with groups of low-power

radios spread out over the geographical service area. Each group of

radios serve MSs presently located near them. The area served by each

group of radios is called a CELL

Uplink and downlink signals for one user are assigned different

frequencies, this kind of technique is called Frequency Division Duplex

(FDD)

Data for different users is conveyed in time intervals called slots ,

several slots make up a frame. This kind of technique is called Time

Division Multiple Access (TDMA)


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GSM Development

Standard Protocol for GSM take effect

System was named as Global System for

Mobile Communication

GSM system began to provide service in Europe(2G)

Provide services for the whole world

Micro Cell Technique is used in GSM system

1989

1991

1992

1994

1996


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Cell Technique

Macro Cell and Micro Cell

A certain radio coverage area formed by a set of transceivers that

connected to a set of antennas is called a CELL.

Macro Cell

In the beginning , High-Power BTSs are adopted to provide services. The

BTS covers a wider area , but its frequency utilization is not efficient. So , it

can only provide a few channels for subscribers.

Micro Cell

Later the Low-Power BTS joins the system for getting a better service area

with high capacity . At the same time it adopts the frequency reuse

technique to improve the efficiency of the frequency utilization and also

the whole capacity of the network.


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Multiple Access Technique

Multiple Access Technique allows many subscribers to

use the same communication medium.

There are three kinds of basic Multiple Access Technique :

FDMA , TDMA and CDMA.

GSM system adopt FDD-TDMA (FDMA and TDMA

together).


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FDMA

FDMA uses different frequency

channels to accomplish

communication.

The whole frequency spectrum

available is divided into many

individual channels (for

transmitting and receiving)，

every channel can support the

traffic for one subscriber or some

control information.

Frequency

Time


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TDMA

TDMA accomplishes the

communication in different

timeslot.

A carrier is divided into

channels based on time.

Different signals occupy

different timeslots in certain

sequence , that is , many

signals are transmitted on the

same frequency in different

time.

Time

Frequency


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CDMA

CDMA accomplishes the

communication in different code

sequences.

Special coding is adopted before

transmission, then different

information will lose nothing

after being mixed and

transmitted together on the

same frequency and at the same

time. Time

Frequency


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GSM 900

Duplex Separation: 45MHz

Channel Bandwidth: 200KHz

The Frequency Spectrum

Uplink

890 915 935 960MHz

Downlink


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Duplex Separation: 95MHz

Channel Bandwidth: 200KHz

Base Station Receive

1710 1785 1805 1880MHz

Base Station Transmit

DCS 1800



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Frequency

Spectrum

Range

(MHz) Uplink Frequency

Frequency

Point

Available

Downlink

Frequency

GSM 450

450.4~457.

6

460.4~467.

6

Fu(n)=450.6+0.2(n-

259) 259<=n<=293

Fd(n)=Fu(n)+1

0

GSM 480 478.8~486

488.8~496 Fu(n)=479+0.2(n-306) 306<=n<=340

Fd(n)=Fu(n)+1

0

GSM 850 824~849

869~894

Fu(n)=824.2+0.2(n-

128) 128<=n<=251

Fd(n)=Fu(n)+4

5

E-GSM

900

880~915

925~960

Fu(n)=890+0.2n

Fu(n)=890+0.2(n-1024)

0<=n<=124

975<=n<=102

3

Fd(n)=Fu(n)+4

5

R-GSM

900

876~915

921~960

Fu(n)=890+0.2n

Fu(n)=890+0.2(n-1024)

0<=n<=124

955<=n<=102

3

Fd(n)=Fu(n)+4

5

PCS 1900 1850~1910

1930~1990

Fu(n)=1850.2+0.2(n-

512)

512<=n<=810

Fd(n)=Fu(n)+8

0


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Frequency Reuse

The frequency resource of mobile system is very limited.

The different Subscribers can use the same frequency in

different places.

The quality of communication must be ensured.


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Frequency Reuse

7(Site)X 1(Cell) reuse

2

1

2

3

4

5

6

7


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4 site X 3 cells reuse

1

8

9

2 10

4 6

5 3

7

11

12

R

Frequency Reuse


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Cell Types

Omni

1

120 degree

1

2 3

Omni-directional Cell

120 Degree Cell


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Contents





5. Radio Techniques



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GSM-GPRS Network Component

GSM /GPRS BSS

BTS

BSC

BTS

BSC

PCU

SS7

SMS system

PSTN

ISDN

Internet,

Intranet

MSC/VLR GMSC

HLR/AUC

SGSN

CG BG

GGSN

GPRS Backbone

Other PLMN

MS

MS

OMC


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Interface Between Different Entities

GSM /GPRS BSS

BTS

BSC

BTS

BSC

PCU

SS7

SMS system

PSTN

ISDN

Internet,

Intranet

MSC/VLR GMSC

HLR/AUC

SGSN

CG BG

GGSN

GPRS backbone

Other PLMN

A

Gb

Gi

Gp

C/D/Gs

Gr/Gs/Gd/Ge Gc

Ga

Abis

Um

MS

MS

OMC


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Mobile Station—MS

International Mobile Equipment Identity

(IMEI)

– Mobile Equipment

MS=ME+SIM

International Mobile Subscriber Identity (IMSI)

– Subscriber Identity Module


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Subscriber Identity Module – SIM

International Mobile Subscriber

Identity (IMSI)

Temporary Mobile Subscriber

Identity (TMSI)

Location Area Identity (LAI)

Subscriber Authentication Key (Ki)

SIM


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BTS

BSC

TC/SM

BSS

MSC

Base Station Subsystem – BSS

The Base Station Controller

– BSC

The Base Transceiver Station

– BTS

The Trans-coder – TC and

Sub multiplexer (SM)


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BTS

BSC

TC/SM

BSS

MSC

Packet Control Unit-----PCU

Packet data

switching

Bridge between

SGSN and BSC

Provide Pb and Gb

interface GPRS

Backbone

PCU SGSN


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Mobile-service Switching Center – MSC Home Location Register – HLR Visitor Location Register – VLR Equipment Identity Register – EIR Authentication Center – AUC

Echo Cancellor – EC

AUC HLR

MSC/VLR

PSTN

NSS

EIR OMC

BSS

EC

The Network Switching System


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Mobile-service Switching Center –

MSC Call Processing

Operations and Maintenance Support

Interface management

Inter-network & Inter-working

Billing


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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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Visitor Location Register – VLR

Mobile Status (IMSI attached / detached / busy / idle etc.)

Location Area Identity(LAI)

Temporary Mobile Subscriber Identity(TMSI)

Allocating the Roaming Number


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IMEI is Checked In White List

IMEI is Checked in Black/Grey List

If NOT found

EIR focus on the

equipment , not the

subscriber!

Equipment Identity Register – EIR

White List

Black List

Grey List


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OMC Functional Architecture

OS

MMI

DB

Event/Alarm

Management

Security

Management

Configuration

Management

Performance

Management

Fault

Management


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Contents





5. Radio Techniques



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Service Area

PLMN service area

......

Service Area

MSC service area...

Location area...

cell

PLMN service area PLMN service area

MSC service area...

Location area...

cell


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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 hex code.

The value 0000 and FFFF is invalid.

For example: 460-00-0011

MCC MNC LAC


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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 hex code to

identify the cells within an LAI.

For example : 460-00-0011-0001

CGI: Cell Global Identification


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BSIC

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, used to

distinguish different cells assigned the same

frequency!

NCC BCC

BSIC

BSIC（Base Station Identification Color Code)


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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 ABCD

Example: 86-139-0666-1234

MSISDN

CC NDC SN

National (significant)

Mobile number

Mobile station international

ISDN number


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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: 666-9777001 NMSI: 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


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TMSI

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 operator.

TMSI: Temporary Mobile Subscriber Identification)


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IMEI

TAC FAC SNR SP

IMEI

IMEI: International Mobile Station Equipment Identification

TAC: Type approval code, 6 bit, determined by the type approval center

FAC: Final assembly code, 2 bit, It is determined by the manufacturer.

SNR: Serial number, 6 bits, It is issued by the manufacturer of the MS.

SP: 1 bit , Not used.

Check the IMEI in your MS : *#06#


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Contents





5. Radio Techniques



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2 3 0 1 6 7 4 5 2 3

The physical channel is the medium over which the

information is carried: 200KHz and 0.577ms

0 1

TDMA FRAME

Timeslot The information carried in one time

slot is called a “burst”

Physical Channel and Logical Channel

The logical channel consists of the information carried

over the physical channels

TDMA FRAME


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Two types of Logical Channel

Traffic Channel (TCH) :

Transmits traffic information, include data

and speech.

Control Channel (CCH) :

Or Signaling Channel, transmits all kinds of

control information.


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Traffic Channel (TCH)

TCH

Traffic Channels

Speech

TCH/FS

Data

TCH/HS TCH/9.6 TCH/2.4

TCH/4.8

TCH Traffic Channel

TCH/FS Full rate Speech Channel

TCH/HS Half rate Speech Channel

TCH/9.6 Data Channel 9.6kb/s

TCH/4.8 Data Channel 4.8kb/s

TCH/2.4 Data Channel 2.4Kb/s


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FCCH SCH

CCH (Control Channels)

DCCH

SDCCH

BCH

BCCH Synch. CH. ACCH

SACCH FACCH CCCH

RACH CBCH

PCH/AGCH

Broadcast Control Channel – BCCH

Common Control Channel – CCCH

Dedicated Control Channel – DCCH

Associated Control Channel – ACCH

Control Channel (CCH)


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CCH

BCH

BCCH Synch.

Channels

SCH FCCH

The information carried on the BCCH

is monitored by the MS

periodically when it is in idle mode

BCCH: Broadcast Control Channel

FCCH: Frequency Correction Channel

SCH: Synchronization Channel

Broadcast Control Channel –

BCCH


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CCH

CCCH

RACH

uplink CBCH

downlink

PCH/AGCH

downlink

The CCCH is responsible for

transferring control information

between all mobiles and the

network.

RACH: Random Access Channel

PCH: Paging Channel

AGCH: Access Granted Channel

CBCH: Cell Broadcast Channel

Common Control Channel – CCCH


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CCH

DCCH

SDCCH

FACCH SACCH

DCCH is assigned to a single

wireless connection for

measurement and handover

purpose.

SDCCH: Stand-alone Dedicated

Control Channel

ACCH: Associated Control Channel

SACCH: Slow Associated

Control Channel

FACCH: Fast Associated Control

Channel

ACCH

Dedicated Control Channel –

DCCH


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RACH CCCH CCH

SDCCH

SACCH

FACCH

TCH/F

TCH/H

DCCH

TCH

DCH

Uplink Logical channel


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FCCH

SCH

BCCH

PCH

AGCH

BCCH

CCCH

CCH

SDCCH

SACCH

FACCH

TCH/F

TCH/H

DCCH

TCH

DCH

Downlink Logical channel


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Allocate signaling channel

FCCH

SCH

BCCH

PCH

RACH

AGCH

SDCCH

SDCCH

TCH

FACCH

Power-off

Idle mode

Dedicated mode

Idle mode

How to use these channels?

Search for frequency correction burst

Search for synchronous burst

Extract system information

Monitor paging message

Send access burst

Set up the call

Allocate voice channel

Conversation

Release the call


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Packet logic channel

Packet data channel (PDCH)

Comprising packet service channel and packet control

channel

Packet service channel (PDTCH)

Combined into the single-directional service channel

Packet control channel

Broadcast control channel: PBCCH

Public control channel: PPCH, PRACH, PAGCH

Private control channel: PACCH, PTCCH

TCH

BCCH

SACCH

CCCH

TCH


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GSM Logical Channel Combination

Main BCCH combination – FCCH + SCH + BCCH + CCCH

SDCCH combination – SDCCH/8 + SACCH/8

Combined BCCH – BCCH + CCCH +SDCCH/4 + SACCH/4

TCH/FR combination – TCH/F + FACCH/F + SACCH/F

TCH/HR combination – TCH/H + FACCH/H + SACCH/H


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Combination of packet logic

channel Packet logic channels (PDCH) can be combined via the

following three modes

Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCH;

Mode 2: PCCCH+PDTCH+PACCH+PTCCH;

Mode 3: PDTCH+PACCH+PTCCH

In case of small GPRS traffic, GPRS and circuit services use the

same BCCH and CCCH in the cell. In this case, only combination

mode 3 is needed in the cell

With the increase of traffic, the packet public channel should

be configured in the cell. Channel combination mode 1 and

mode 2 should be adopted


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TDMA Frames

0 1

0 1 2 4 3 46 47 48 50 49

51 – Frame Multi-frames

0 1 1 0

CONTROL

CHANNELS

2 3 4 5 6 7 2 3 5 7 6 4

GSM Multi-frames


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GSM Multi-frames

TDMA Frames

0 1

0 1 2 4 3 21 22 23 25 24

26 – Frame Multi-frames

0 1 1 0

TRAFFIC

CHANNELS

2 3 4 5 6 7 2 3 5 7 6 4


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Contents





5. Radio Techniques



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Power Control

Saves battery power

Reduces co-channel and

adjacent channel interference

8W

0.8W

5W

Both Uplink and Downlink

power settings can be

controlled independently and

individually.

BCCH -------

Does not attend Power

control


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DTX and VAD

Voice Activity Detection – VAD

Discontinuous Transmission – DTX

Battery Saving

Interference reduction


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Timing Advance (TA)

Transmission delay t

Transmission delay t

TA

The mobile phone should

send the signal in advance!


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Multi-path Fading

Diversity

Frequency Hopping

Time Dispersion


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Diversity – What’s Diversity?

Receive diversity provides an effective technique for both

overcoming the impact of fading across the radio channel

and increasing the received signal to interference ratio.

The former is achieved by ensuring “uncorrelated” (i.e.

low enough correlated) fading between antenna

branches i.e. not all antennas experience fades at the

same time.


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Kinds of Diversity

Time diversity

Coding, interleaving

Frequency diversity

Frequency hopping

Space diversity

Multiple antennas

Polarization diversity

Dual-polarized antennas

Multi-path diversity

Equalizer

t

f


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Frequency Hopping Frequency

f 0

Frame

f 1

f 2

f 3

f 4

Time


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Contents





5. Radio Techniques



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Page67

57.6 kbps

115 kbps

384 kbps

2 Mbps

GSM

HSCSD

GPRS

EDGE

IMT-2000

9.6 kbps

2G

2.5G

3G

GSM Development Evolution


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Data rate of EDGE and GPRS

8PSK GMSK

9.0

13.415.6

21.4

8.811.2

14.817.6

22.4

29.6

44.8

54.4

59.2

0.0

10.0

20.0

30.0

40.0

50.0

60.0

CS-1 CS-2 CS-3 CS-4 MCS-1 MCS-2 MCS-3 MCS-4 MCS-5 MCS-6 MCS-7 MCS-8 MCS-9

Kbps

GPRS

EGPRS


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Huawei EDGE Test Result

Downlink, 4 TS, MCS-9：


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Page70

Summary

The basic idea of GSM

The frequency spectrum used in GSM

The structure of GSM

Certain service area and numbers

Some radio techniques used in GSM

Evolution of GSM

Thank you www.huawei.com

huawei gsm principles

Engineering