GSM Fundamentals

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Transcript of GSM Fundamentals

GSM FundamentalsISSUE

Wireless Curriculum Development Section

Engr Chinonso Ezeobi

INTRODUCTION,

GSM-FUNDAMENTALS SOCIETY NIGERIAN OF

PRESENTED OF

TO

NIGERIAN DIVISION( AND

ENGINEERS-

ELECTRICAL

INSTITUTION

ELECTRICAL

ELECTRONICS ENGINEERS-NIEEE) BY

ENGR CHINONSO EZEOBI2

Contents

Basic Concepts of Cellular Mobile System GSM Network Components Terrestrial Interface Service Area and Number Planning Channels on The Air Interface

3

Engr

The Frequency Spectrum

GSM 900EGSM 880 890 GSM 915 925 EGSM 935 GSM 960 MHz

Duplex Separation: Channel Bandwidth: Engr

45MHz 200KHz4

The Frequency Spectrum

DCS 1800Base Station Receive1710

Base Station Transmit1785 1805 1880MHz

Duplex Separation: Channel Bandwidth: Engr

95MHz 200KHz5

Frequency Re-Use

What is Frequency Re-Use?Because frequency resource of mobile system is very limited, different Subscribers must use the same frequency in different place. Of course, the quality of communication must be ensured.

6

Frequency Re-Use

How can we reuse frequency?2

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

7 1 6 5

3 2

4

7

Engr

Frequency Re-Use

4(Site)X 3(Cell) Re-use3 5 1 9 11 4 1 7

5 9 2 8 12 3 10 1 98

6 10 7 11

62

5

Engr

CELL

Omni-Directional Cells

Omni

1 1120 degree

120 Degree Sectors

29

3Engr

Contents

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 Development10

GSM Network Components

NSS OSSOMC

AUC HLR EIR MSC/VLR PSTN

ME

SIM

BTS

BSC11

MS

BSS

Engr

Mobile StationMS

MS=ME+SIMInternational Mobile Equipment Identity (IMEI) Mobile Equipment International Mobile Subscriber Identity (IMSI) Subscriber Identity Module12

Engr

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.13

Engr

Base Station Subsystem BSS

MSC The Base Station Controller BSC The Base Transceiver Station BTS The Trans-coder TC and Sub multiplexer (SM)

BSS TC/SMBSC BTS14

Engr

The Network Switching System

NSSOMC

AUC HLR EIR EC MSC/VLR IWF PSTN

Mobile Switching Center Home Location Register Visitor Location Register Equipment Identity Register Authentication Center Inter-Working Function Echo Cancellor

MSC HLR VLR EIR AUC IWF EC

BSS15

Engr

Mobile Service Switching Center MSC

Call Processing Operations and Maintenance Support Inter-network & Inter-working Billing

16

Engr

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

17

Engr

Visitor Location Register VLR

Mobile Status(IMSI detached/ attached) Location Area Identity(LAI) Temporary Mobile Subscriber Identity(TMSI) Mobile Station Roaming Number(MSRN)

18

Engr

Equipment Identity Register EIR

White List Black List Grey List

IMEI Is Checked against White 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

IMEI Is Checked against Black/Grey List

19

Engr

Operation and Maintenance Sub System

OSS(NMC)

OMC

OMC

OMC

Region2

Region 3 Region 120

Engr

Operation and Maintenance Center OMC

OMC R: OMC assigned specifically to the Base Station Subsystem

OMC S: OMC assigned specifically to the Network Switching Subsystem

21

Engr

OMC Functional Architecture

Event/Alarm Management

Security Management

MMI OSFault Management Performance Management22

DBConfiguration Management

Engr

GSM InterfaceD VLR B MSC E EC EC A TC MS Um BTS Abis BSC MSC G VLR C

HLR H AUC F EIR

IWF

IWF

23

Engr

SigL1: 2MBps TrunksHLR AUC EIR MSC/VLR EC EC TC BSC BTS BTS24

IWF MSC/VLR

OMC

PSTN

Engr

2MBps Trunks

Typical Configuration TS 0 TS 1-15 TS16 TS 17-31

TS = Time slot TS# 0 1-15 16 Traffic CCS7 Signaling (Other TS may also the used) Used for Frame Alignment /Error Checking /Signaling

17-31 Traffic25

Engr

Contents

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 Development26

Engr

Physical and Logical ChannelsThe physical channel is the medium over which the information is carried The logical channels consist of the information carried over the physical channel TDMA FRAME

0

1Timeslot

2

3

4

5

6 0

7

The information carried in one time slot is called a burst27

Engr

Traffic Channel

TCH Traffic ChannelsNormal Burst

Speech TCH/FS TCH/HS

Data

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

TCH/9.6

TCH/2.4

TCH/4.828

Engr

Control Channel

CCH Control ChannelsDCCH SDCCH ACCH BCCH

BCCH CCCH SCH

Synch. CH.

FACCH

SACCH

FCCH

Broadcast Control Channel BCCH RACH CBCH Common Control Channel CCCH Dedicated Control Channel DCCH Associated Control Channel ACCH PCH/AGCH

29

Engr

Broadcast Control Channel BCCH

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 Channel Correction

CCH BCCH downlink only

BCCH

Synch. Channels

SCH: Synchronization Channel SCH FCCH30

Engr

Common Control Channel CCCH

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 RACH uplink

CCH

CCCH

CBCH downlink

PCH/AGCH downlink31

Engr

Dedicated Control Channel DCCH

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

CCH DCCH

SDCCH

ACCH

FACCH

SACCH32

Engr

How to use these channel?

Power-off state

Search for frequency correction pulse Search for synchronous pulse Unscramble system informationIdle state

FCCH SCH BCCH PCH RACH AGCH SDCCH FACCH TCH FACCH33

Snoop into paging message Send access pulse Allocate signaling channelDedicated mode

Set up the call Allocate voice channel Conversation Release the callIdle state

Engr

GSM Multiframe

TDMA Frames 00

1

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

0

1

2

3

4

46 47 48 49 50

51 Frame Multiframes

CONTROL CHANNELS34

Engr

Timeslots and TDMA Frames Higher Capacity Cell 0 1 2 3 4Traffic

5

6 0 6 0

7

Broadcast Dedicated

0

1

2

3Traffic

4

5

7

Low Capacity Cell 0Combined

1

2Traffic

3

4

5

6 0

735

Engr

GSM MultiframeTDMA Frames 00

1

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

0

1

2

3

4

21 22 23 24 25

26 Frame Multiframes

TRAFFIC CHANNELS36

Engr

Contents

Basic Concepts of Cellular Mobile System GSM Network Components Terrestrial Interface Service Area and Number Planning Channels on The Air Interface Radio Technologies

37

Engr

Modulation Techniques

Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM) phase modulation can be implemented easily for digital signals, this is the method used for the GSM air interfaces. Phase Modulation is known as Phase Shift Keying when applied to digital signals38

Engr

Gaussian Minimum Shift Keying (GMSK)

1 0 0 1 1

Gaussian Digital Filter

Phase Modulator

39

Engr

Battery Life

Power ControlVoice Activity Detection VAD Discontinuous Transmission DTX Discontinuous Reception DRX40

Engr

Power Control

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

8W

0.8W 5WSaves radio battery power Reduces co-channel and adjacent channel interference41

Engr

VAD & DTX

Without DTX Encoding the speech silences at a rate of 500 bit/s rather than the full 13Kb/s. If the mobil