- The document describes a presentation given by Animesh Lochan on his industrial training at Ericsson India Pvt. Ltd. regarding the Global System for Mobile Communication (GSM). - It provides an overview of GSM, including its architecture, frequency bands, components like the mobile station, base station subsystem, network switching subsystem, and interfaces. Diagrams and explanations of network identifiers like IMSI, IMEI, and MSISDN are also included.

1. 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

2. 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.
GSM- Animesh Lochan (11) 2

3. 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- Animesh Lochan (11) 3

4. GSM ARCHITECTURE
GSM- Animesh Lochan (11) 4

5. 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

6. 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

7. 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 BSC
2. 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

8. 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.

9.  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

10.  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
)

11.  (Um) Air interface - MS to BTS
 A bis interface - BTS to
BSC
 A Interface - BSC to MSC
 B Interface - MSC to VLR
 C interface - MSC to HLR
GSM- Animesh Lochan (11) 11

12.  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.
GSM- Animesh Lochan (11) 12

13.  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)
GSM- Animesh Lochan (11) 13

14.  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.
GSM- Animesh Lochan (11) 14

15. CC NDC SN
98 XXX 12345
CC = Country Code
NDC = National Destination Code
SN = 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.
GSM- Animesh Lochan (11) 15

16.  IMSI (International Mobile Subscriber Identity) Network Identity Unique To A Sim.
MCC MNC MSIN
404 XX 12345..10
SIM = Subscriber Identity Module
MCC = Mobile Country Code
MNC = Mobile Network Code
MSIN = Mobile Subscriber Identity Number
GSM- Animesh Lochan (11) 16

17. IMEI
 IMEI : Serial number unique to each mobile
TAC FAC SNR SP
6 2 6 1
IMEI = International Mobile Equipment Identity
TAC = Type Approval Code
FAC = Final Assembly Code
SNR = Serial Number
SP = Spare
GSM- Animesh Lochan (11) 17

18.  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.
GSM- Animesh Lochan (11) 18

19. 
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- Animesh Lochan (11) 19

20. • GSM 900 and GSM 1800 are twins
GSM 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- Animesh Lochan (11) 20

21. GSM- Animesh Lochan (11) 21

22. Definitions
 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
0 7 0
TDMA frame  4.615 ms
BURST PERIOD

23. Summary
 Same in GSM900 and
GSM1800
FCCH
Dedicated Channels
Traffic Channels
(TCH)
TCH/9.6F
TCH/ 4.8F, H
TCH/ 2.4F, H
(DCH)
Common Channels
Broadcast Channel
(BCH)
Logical Channels
Common Control Control Channels
Channel (CCCH)
SCH BCCH
(Sys Info)
(CCH)
PCH AGCH RACH SDCCH FACCH TCH/F TCH/H
SACCH
GSM- Animesh Lochan (11) 23

24.  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.
GSM- Animesh Lochan (11) 24

25. FCCH
SCH
SDCCH
PCH
AGCH
BCCH
CCCH
Common
Channels
Dedicated
Channels
SACCH
FACCH
SDCCH
TCH/F
TCH/H
DCCH
TCH
GSM- Animesh Lochan (11) 25

26. RACH CCCH
Common
Channels
SDCCH
SACCH
FACCH
TCH/F
TCH/H
DCCH
TCH
Dedicated
Channels
GSM- Animesh Lochan (11) 26

27. 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
'off' state
idle mode
dedicated
mode
idle mode
GSM- Animesh Lochan (11) 27

28. GSM- Animesh Lochan (11) 28

29. T
15
26 FRAME MULTIFRAME STRUCTURE
T
5
T
9
T
10
T
11
S
12
T
13
T
14
T
6
T
7
T
8
T
0
T
1
T
2
T
3
T
4
T
16
T
17
T
18
T
19
T
20
T
21
T
22
T
23
T
24
I
25
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
120 msec
4.615 msec
• 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.

30. Hyperframe = 2048 Superframes  3.5 h
26 Multiframe = 120 ms 51 Multiframe  235 ms
TCH 0 1 2 24 25 0 1 2 49 50 SIGN.
0 7
TDMA frame  4.615 ms
Superframe =
26x51 or
51x26 Multiframes
= 6.120 sec