Gsm Fundamentals

GSM Fundamentals ISSUE 3.2

Wireless Wireless Curriculum Curriculum Development Development Section Section

Contents

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

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Objectives

On completion of this section you will be able to:  Name the two different cell types and understand why and when each would be used.  Get the concept of frequency reuse.  Name the frequency spectrum used in GSM Confidential Information of Huawei. No Spreading without Permission.

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CELL

Omni

Omni-Directional Omni-Directional Cells Cells

120 120 Degree Degree Sectors Sectors

1 1 120 degree

3 Confidential Information of Huawei. No Spreading without Permission.

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2

Cell concept Signal strength

Rural Highway Suburb

Town

distance

• Cell Flexible : basic network service planning area that based can on be efficiently location nature managed by the network • Smooth Handover (no service degradation while subscriber moves) • One base station (equipment to switch, transmit and receive calls) • Frequency reuse (same group of frequencies used in different cells) per cell for comm. between MS and the network • Cell boundaries are defined by BS signal strength Confidential Information of Huawei. No Spreading without Permission.

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Frequency Spectrum GSM 900 Physical channels 45 MHz duplex spacing

… …

890 MHz

1

f

T

A DM

fr

e= am

5 0.

77

s m

x

S 8T

200 KHz x 125 = 25 MHz

200 KHz

25 MHz Uplink (MS to BS) 890 MHz

t

…935 MHz …

915 MHz

… …

……

25 MHz Downlink (BS to MS) 915 MHz 200 KHz

For DCS1800: uplink from 1710 to 1785MHz, downlink is from 1805 to 1880MHz 75Mhz each / 374 RF carriers . 95MHz duplex spacing. Confidential Information of Huawei. No Spreading without Permission.

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960 MHz

f

Contents

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

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Security Level: Internal

Objectives

On completion of this section you will be able to:

Identify the types of physical channels and logical channels

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Logical channels Logical traffic channels Logical Channels SPEECH

TCH/H R 7kbps

CCH DATA

TCH

TCH/F R 13kbps

2.4/4.8kbps(FR&HR)

logical channels consist of the information carried over the physical channel. Confidential Information of Huawei. No Spreading without Permission.

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9.6kbps FR

Logical control channels CCH DCH SACC H

SDCC H

CCCH PC H

AGC H

BCH RAC H

Power & timing control RSSI & link quality

BCC H

FACC H

FCC H SC H

•Power Control indicator •cell ID , LAI , PLMN code •List of neighboring cells

Auth. and HO.

control channel, toused send cell information. --Broadcast - Frequency-correction MS frequency correction. Standalone dedicated channel :(alert) Supports the transfer of data during connection Slow/Fast Random access associated control forused channels dedicated :for channels carrying assignment information request associated with the Paging channel :channel, used tochannel, page MS - Synchronization channel, used for frame or synchronization BS MS setup -Access process being grantcarried channel, out used on to either assign theMS dedicated SDCCH control the TCH. channels and for the identification. Confidential Information of Huawei. No Spreading without Permission.

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Timeslots and TDMA Frames Low Capacity Cell / 1 RF carrier 0

1

Combined

3

2

4

5

6

7

Traffic

Higher Capacity Cell / more than 1 RF carrier 0

1

2

3

Broadcast Dedicated

0

1

4

60

7

5

60

7

Traffic

2

3

4

Traffic Confidential Information of Huawei. No Spreading without Permission.

5

Security Level: Internal

Contents

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

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Security Level: Internal

Service Area System area PLMN PLMN service service area area MSC service area... Location area... Base station area...

Radio cell

......

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PLMN service area MSC service area... Location area... Base station area...

Radio cell

......

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......

LAI

MCC

MNC

LAC

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

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CGI

CGI: Cell Global Identification

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

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MSISDN

CC

NDC

SN

National (significant) Mobile number Mobile station international ISDN number

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 Confidential Information of Huawei. No Spreading without Permission.

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IMSI Not more than 15 digits 3 digits

2 digits

MCC

MNC

MSIN NMSI

IMSI 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 Confidential Information of Huawei. No Spreading without Permission.

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IMEI

IMEI: International Mobile Station Equipment Identification

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. Confidential Information of Huawei. No Spreading without Permission.

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Contents

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

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Security Level: Internal

GSM network architecture Permanent White list : data: Temporary data: --copy IMSIofmobiles most of data for Valid

active -Suppl.subscribers service infoin. VLR Black coveragelist : -Authentication key -Mobileor status Stolen forbidden -Roaming & billing info -LAI Gray list :

Othe r GSM

OMC

Gray list : -TMSI

Faulty mobiles Temporary data: -MSC/VLR address

PSTN Base Transceiver Station : the first access point for mobile stations to access the Base Mobile Station Station : -Center Mobile : :controls Equipment one or more BTSs and ME interfaces identification BSS totoNSS. It is Mobile Switching controls onecontains or moreIMEI BSCsfor and manages switching network. TheController BTS is a radio equipment (transceivers & antennas) needed serve a high capacity switch - Subscriber that provides Identityhandover, module contains cell configuration IMSI,TMSI,LAI,Auth. data. key each cell in the network. Confidential Information of Huawei. No Spreading without Permission.

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Transcoder and submultiplexer

30 x 64k voice channels = 120 x 16k compressed/combined = 2Mbps PCM link Confidential Information of Huawei. No Spreading without Permission.

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Contents

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

Confidential Information of Huawei. No Spreading without Permission.

Security Level: Internal

Objectives

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

Diversity Frequency Hopping

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Diversity Approx. 10 wavelengths 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 or add signals

Resultant Signal Confidential Information of Huawei. No Spreading without Permission.

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Frequency Hopping

Each time the BTS or mobile transmits a burst, it does so on a different RF carrier frequency. Synthesizer Hopping:each timeslot on a given transceiver can transmit at a different frequency

frequency

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

time Confidential Information of Huawei. No Spreading without Permission.

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