gsm

BUNDELKHAND INSTITUTE OF ENGINEERING AND

TECHNOLOGY, JHANSI

PRESENTATION ON INDUSTRIAL TRAINING( 2014-15)At

ERICSSON INDIA PVT. LTD, LUCKNOW

STUDY OF GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM)

BY-ANIMESH LOCHAN

7th semester ECE- 1104331011

COMPANY PROFILE

Communication is changing the way we live and work. Ericsson plays a key role in this evolution, using innovation to empower people, business and society. Ericsson provides communications networks, telecom services and support solutions, making it easier for people all over the globe to communicate.

Approximately 40 percent of the world’s mobile traffic passes through network equipment supplied by Ericsson.

The networks Ericsson supports for operators serve more than 2.5 billion subscribers.

Ericsson has over 64,000 services professionals. Ericsson has customers in more than 180 countries. Ericsson has been in the telecoms market for 138 years. Ericsson is the fifth largest software supplier in the world.

2GSM- Animesh Lochan (11)

GSM Overview • Global System for Mobile (GSM) is a second

generation cellular standard developed to cater voice services and data delivery using digital modulation

• GSM operating frequencies:- 850 MHz- 1900 MHz- America 900 MHz- 1800 MHz- Rest of world• Uplink frequency – 890MHz- 915 MHz Downlink frequency – 935MHz- 960 MHz


GSM ARCHITECTURE


Contd… Mobile Station (MS)

Mobile Equipment (ME)Subscriber Identity Module (SIM)

Base Station Subsystem (BSS)

Base Transceiver Station (BTS)Base Station Controller (BSC)

Network Switching Subsystem(NSS)

Mobile Switching Center (MSC)Home Location Register (HLR)Visitor Location Register (VLR)Authentication Center (AUC)Equipment Identity Register (EIR)

GSM- Animesh Lochan (11) 5

Mobile Station (MS)1. Mobile Equipment

◦ Portable, hand held device ◦ Uniquely identified by an IMEI (International Mobile

Equipment Identity)◦ Voice and data transmission ◦ Power level : 0.8W – 20 W◦ 140 character long SMS.

2. Subscriber Identity Module (SIM)◦ Smart card contains the International Mobile

Subscriber Identity (IMSI)◦ Allows user to send and receive calls and receive other

subscribed services◦ Protected by a password or PIN◦ Can be moved from phone to phone – contains key

information to activate the phone

Base Station Subsystem (BSS)1. Base Transceiver Station (BTS)

◦ Encodes, encrypts,multiplexes,modulates and feeds the RF signals to the antenna.

◦ Communicates with Mobile station and BSC2. Base Station Controller (BSC)

◦ Assigns Frequency and time slots for all MS’s in its area

◦ Handles call set up◦ It communicates with MSC and BTS

Network Switching Subsystem(NSS)Mobile Switching Center (MSC)

Heart of the network Manages communication between GSM and other

networks Call setup function and basic switching Call routing Billing information and collection Mobility management

- Registration- Location Updating

MSC does gateway function while its customer roams to other network by using HLR/VLR.

Home Location Registers (HLR)

- permanent database about mobile subscribers in a large service area (generally one per GSM network operator)

- database contains IMSI, prepaid/postpaid, roaming restrictions, supplementary services.

Visitor Location Registers (VLR)

- Temporary database which updates whenever new MS enters its area, by HLR database

- Controls those mobiles roaming in its area

Authentication Center (AUC)

- Protects against intruders in air interface- Maintains authentication keys and algorithms

and provides security.- Generally associated with HLR

Equipment Identity Register (EIR)- Database that is used to track handsets using

the IMEI (International Mobile Equipment Identity)

- Only one EIR per PLMN (public land mobile network )

GSM Interfaces

(Um) Air interface - MS to BTS

A bis interface - BTS to BSC

A Interface - BSC to MSCB Interface - MSC to VLRC interface - MSC to HLR


(Um) Air Interface

This is the interface between the mobile station and the Base station.

The Air interface uses the Time Division Multiple Access (TDMA) technique to transmit and receive traffic and signalling information between the BTS and MS.

The TDMA technique is used to divide each carrier into eight time slots.These time slots are then assigned to specific users,allowing up to eight conversations to be handled Simultaneously by the same carrier.


A-bis Interface

The A-bis interface responsible for transmitting traffic and signalling information between the BSC and the BTS.

The transmission protocol used for sending signalling information on the A-bis interface is Link Access Protocol on the D Channel (LAPD)


A Interface

A interface between the BSC and the MSC

The A interface provides two distinct types of information, signalling and traffic, between the MSC and the BSC.


MSISDN

CC NDC SN

98 XXX 12345

CC = Country CodeNDC = National Destination CodeSN = Subscriber Number

• The Mobile Subscriber ISDN (MSISDN) number is the telephone number of the MS. This is the number a calling party dials to reach the subscriber. It is used by the land network to route calls towards the MSC.


IMSI

IMSI (International Mobile Subscriber Identity) Network Identity Unique To A Sim.

MCC MNC MSIN

404 XX 12345..10

SIM = Subscriber Identity ModuleMCC = Mobile Country CodeMNC = Mobile Network CodeMSIN = Mobile Subscriber Identity Number


IMEI

IMEI : Serial number unique to each mobile

TAC FAC SNR SP

6 2 6 1

IMEI = International Mobile Equipment IdentityTAC = Type Approval CodeFAC = Final Assembly CodeSNR = Serial NumberSP = Spare


SUBSCRIBER IDENTIFICATION MODULE (SIM)

By making a distinction between the subscriber identity and the mobile equipment identity, a GSM PLMN can route calls and perform billing based on the identity of the subscriber rather than the mobile equipment being used. This can be done using a removable Subscriber Information Module (SIM). A ”smart card” is one possible implementation of a SIM module.

IMSI. This is transmitted at initialization of the mobile equipment. TMSI This is updated periodically by the PLMN MSISDN This is made up of a country code, a national code and a subscriber

number. Location Area Identity (LAI) This identified the current location of the

subscriber. Subscriber Authentication Key (KI) This is used to authenticate the SIM.


EQUIPMENT IDENTITY NUMBER

International Mobile station Equipment Identity (IMEI)

Each MS is identified by an International Mobile station Equipment Identity (IMEI) number which is permanently stored in the mobile equipment. On request, the MS sends this number over the signalling channel to the MSC. The IMEI can be used to identify MS,s that are reported stolen or operating incorrectly.

Equipment Identity Register ( EIR ) A listing of the allowed IMEI is maintained by the PLMN’s in the

Equipment Identity Register (EIR) to validate the mobile equipment.


• GSM 900 and GSM 1800 are twinsGSM 900 GSM 1800

• Frequency band 890 - 960 MHz 1710 - 1880 MHz

• Number of channels 124 (125) 372 (375)

• Channel spacing 200 kHz 200 kHz• Multiplex technologies TDMA/FDMA TDMA/FDMA• Mobile power 0.8 / 2 / 5 W 0.25 / 1 W

There are no major differences between GSM 900 and GSM 1800

GSM Bandwidth & Main Parameters Summary


Logical Channel Structure


Logical ChannelsDefinitions

TDMA Frame = 8 Time Slots (0.577 ms each)

Physical Channel = 1 TS of the TDMA Frame on 1 specific carrier

Logical Channel = the "purpose" a physical channel is used for

0 0

TDMA frame - 4.615 msBURST PERIOD

0 7 0

Logical ChannelsSummary

Same in GSM900 and GSM1800

FCCH

Traffic Channels (TCH)

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

Dedicated Channels(DCH)

Broadcast Channel(BCH) Control ChannelsCommon Control

Channel (CCCH)

SCH BCCH(Sys Info)

TCH/FAGCH RACH SDCCH FACCH TCH/HPCH

Common Channels (CCH)

Logical Channels

SACCH


Mapping on Physical Channels

The Logical channels are mapped on the physical channels.

The TDMA frames are grouped together into multi-frame.26 TDMA multi-frame for Traffic.51 TDMA multi-frame for control

signal.


FCCHSCH

SDCCH

PCH

AGCH

BCCH

CCCH

Common Channels

Dedicated Channels

Logical ChannelsDownlink

SACCHFACCHSDCCH

TCH/F

TCH/H

DCCH

TCH


RACH CCCHCommon Channels

SDCCHSACCHFACCH

TCH/F

TCH/H

DCCH

TCH

Dedicated Channels

Logical ChannelsUplink


Logical ChannelsSummary

Search for frequency correction burst FCCH

Search for synchronisation sequence SCH

Read system informations BCCH

Listen for paging PCH

Send access burst RACH

Wait for signalling channel allocation AGCH

Call setup SDCCH

FACCH

Traffic channel is assigned TCH

Conversation TCH

Call release FACCH

idle mode

'off' state

dedicated mode

idle mode


Traffic Channel Multiframe


T15

T5

T9

T10

T11

S12

T13

T14

T6

T7

T8

T0

T1

T2

T3

T4

T16

T17

T18

T19

T20

T21

T22

T23

T24

I25

00 11 22 33 44 55 66 77 00 11 22 33 44 55 66 77 00 11 22 33 44 55 66 77

120 msec

4.615 msec26 FRAME MULTIFRAME STRUCTURE

• MS on dedicated mode on a TCH uses a 26-frame multiframe structure.• Frame 0-11 and 13-24 used to carry traffic.• Frame 12 used as SACCH to carry control information from and to MS to BTS.• Frame 25 is idle and is used by mobile to decode the BSIC of neighbor cells.

0 7

TDMA frame - 4.615 ms

26 Multiframe = 120 ms 51 Multiframe - 235 ms

TCH SIGN.0 1 2 24 25 0 1 2 49 50

Hyperframe = 2048 Superframes - 3.5 h

Superframe = 26x51 or 51x26 Multiframes= 6.120 sec

Logical ChannelsStructure

Thank you…

gsm

Engineering

mobile gsm

interface bsc

mobile station ms1

mobile subscribers

msc b interface msc

mobile equipment portable

hlrgsm animesh lochan

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