SEMINAR ON
GSM-Global System for Mobile
Communication
Presented by:- Pratibha
ECE
Vth sem
WHAT IS GSM ?
Global System for Mobile (GSM) is a
second generation cellular standard
developed to cater voice services and
data delivery using digital modulation
GSM:History
• Developed by Group Spéciale Mobile (founded 1982) which was an
initiative
of CEPT ( Conference of European Post and Telecommunication )
• Aim : to replace the incompatible analog system
• Presently the responsibility of GSM standardization resides with special mobile
group under ETSI ( European telecommunication Standards Institute )
• Full set of specifications phase-I became available in 1990
• Under ETSI, GSM is named as “ Global System for Mobile communication “
• Today many providers all over the world use GSM (more than 135
countries in Asia, Africa, Europe, Australia, America)
• More than 1300 million subscribers in world and 45 million subscriber in India.
Tele Services
• Telecommunication services that enable
voice communication
via mobile phones
• Offered services
- Mobile telephony
- Emergency calling
Bearer Services
• Include various data services for information transfer
between GSM and other networks like PSTN, ISDN etc at
rates from 300 to 9600 bps
• Short Message Service (SMS)
–up to 160 character alphanumeric data transmission
to/from the mobile terminal
• Unified Messaging Services(UMS)
• Group 3 fax
• Voice mailbox
• Electronic mail
Supplementary Services
Call related services :
• Call Waiting- Notification of an incoming call while on the handset
• Call Hold- Put a caller on hold to take another call
• Call Barring- All calls, outgoing calls, or incoming calls
• Call Forwarding- Calls can be sent to various numbers defined by
the user
• Multi Party Call Conferencing - Link multiple calls together
• CLIP – Caller line identification presentation
• CLIR – Caller line identification restriction
• CUG – Closed user group
GSM Specifications-1
System
Uplink
GSM 900
890-915 MHz
MHz
GSM 1800 1710-1785 MHz
1880MHz
GSM 1900
1850-1910MHz
1990MHz

Downlink
935-960
18051930-
GSM is a typical 2nd generation system
Performance characteristics of
GSM
Communication
Mobile, wireless communication; support for voice and data
srvices
Total mobility
International access, chip-card enables use of access points of
different providers
Worldwide connectivity
One number, the network handles localization
GSM System Architecture
OMC
HLR
UM Interface
B
T
S
PSTN
ISDN
B
T
S
BSC
BSC
MSC VLR
A Interface
B
T
S
Air interface
(
A-bis interface
VLR
Data
Networks
GSM Applications
1.Mobile telephony
2.Telemetry System
- Fleet management
- Automatic meter reading
- Toll Collection
- Remote control and fault reporting of stolen sets
3.Value Added Services
Mobile Station (MS)
A Typical Handset Consists of the
following parts:
◦ A microscopic microphone
◦ A speaker
◦ An LCD or plasma display
◦ A mini keyboard
◦ An Antenna
◦ A battery
◦ A Circuit board
◦ SIM
Mobile station (MS)
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MS is the radio mobile terminal carried by the subscriber
MS comprises of all user equipment and software needed for
communication with GSM end-point of the radio interface (Um)
MS consists of
◦ User independent HW and SW
◦ SIM (Subscriber Identity Module)
MS can be identified by IMEI (Intl Mobile Equipment Identity)
MSs have transmit power of 2W and 1W
SIM
Subscriber Identity Module (SIM)
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•
•
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Smart card contains the International Mobile Subscriber
Identity (IMSI)
Allows user to send and receive calls and receive other
subscribed services
Encoded network identification details
- Key Ki,Kc and A3,A5 and A8 algorithms
Protected by a password or PIN
Can be moved from phone to phone – contains key
information to activate the phone
What is SIM capable of ?
Display text from the SIM on the Mobile
Equipment's display.
Set up a voice or data call to a number held in the
SIM
Send an SMS message.
Play a tone in the Mobile's ear-piece or ringer
CONTINUED
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Establish an interaction with the user.
Provide local information from the ME to the SIM.
Allow help text to be displayed for the user if
requested.
Encrypt data being sent via handset whenever
needed.
SIM cards were perceived as Security modules for
authentication of user with some extra memory
System Architecture
Base Station Subsystem (BSS)
Base Transceiver Station (BTS):
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•
•
•
Encodes,encrypts,multiplexes,modulates and feeds the
RF signals to the antenna.
Frequency hopping
Communicates with Mobile station and BSC
Consists of Transceivers (TRX) units
Base Transceiver Station (BTS)
 Comprises of all radio specific functions and
components including antennas, amplifiers,
signal processing (houses all transceivers)
 If directed antennas are used, one BTS can
cover several cells
 Connected to MS via Um interface and to BSC
via Abis interface
 GSM cell can measure between 100m to 35
kms depending on environment
Some functions of BTS
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Ability to manage Full Rate and Half Rate
channels.
Supervision of Stationary Wave Report
(SWR) on the antenna
Frequency Hopping
Antenna Diversity
Discontinuous Transmission (DTX) both in
the Uplink and Downlink
Base Station Controller (BSC)
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Governs the radio resources for one or more BTSs
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Controlling connection between the BTSs and MSCs
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Managing of network resources, administrating radio
channels, signaling, frequency hopping anad handovers
Mapping of radio channels (Um) onto terrestrial channels
(A interface).
 Performs paging of MS
 Functions of transforming the Full Rate (16 KBPS) or
Half Rate (8 KBPS) radio channels into 64 KBPS
channels
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Handover
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Cellular systems require handover procedures, as single
cells do not cover the whole service area, but, e.g., only up
to 35 km around each antenna . The smaller the cell size
and the faster the movement of a mobile station through
the cells (up to 250 km/h for GSM), the more handovers
of ongoing calls are required. However, a handover should
not cause a cut-off, also called call drop.
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There are two basic reasons for a handover (about
40 have been identified in the standard):The mobile station
moves out of the range of a BTS or a certain antenna of a
BTS respectively. Thus, the received signal level becomes
lower continuously until it falls underneath the minimal
requirements for communication. Or the error rate may
grow due to interference, the distance to the BTS may be
too high (max. 35 km) etc. - all these effects may diminish
the quality of the radio link and make radio transmission
impossible in the near future.
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HANDOVER
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Cellular systems require Handover
procedures
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Two basic reasons
– MS moves out of the range of a BTS - Signals
becoming weaker
– Interference cause errors
What is CDMA?
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Code Division Multiple Access (CDMA)
◦ Digital Wireless Technology
◦ Pioneered and commercially developed by
QUALCOMM.
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CDMA was adopted by the
Telecommunications
Industry Association
(TIA) in 1993.
◦ Commercially introduced in 1995
◦ May 2001 there were 35 million
subscribers on cdmaOne systems
worldwide.
◦ As of Dec 2002,There were 127 million
CDMA users worldwide.
◦ Fastest-growing wireless technologies
◦ Provides greater total capacity than other
technologies
◦ Choice new 3G systems
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The original CDMA(IS 95) is now known as
CDMAOne.
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We now have cdma2000 and its variants like 1x
EV, 1xEV-DO, and 3x.
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The refer to variants of usage of a
◦ 1x uses a 1.25Mhz channel.
◦ 3X uses a 3.75 Mhz channel
Advantages of CDMA
◦ Huge Bandwidth
◦ Voice clarity
◦ Less call drops (almost zero) during the
peak period
◦ Efficient power control methods (even in
the handsets)
◦ More security