2. WHAT IS MOBILITY ?
• Access the Technology everywhere whether
we are work or play, in the office, grounds or
at home. To meet this demand the GSM
(Global System for Mobile Communication) for
mobile telephony was introduced in the mid-
1980s. A boom is underway, such that many
GSM user find life without their phone
practically inconceivable.
4. Broad Band
4G
Service type
Narrow Band Wide Band
1G 2G 3G
Multi
media
Wireless
Internet
Mobile
IMT
Digital system
2000
Voice IS 95
Analog
IS 136
AMPS
GSM
~ 24kbps ~64kbps ~2Mbps ~20Mbps
1980 1990 2000 2010
Years
5. Freq PN Code
Freq Freq
Time Time Time
FDMA TDMA CDMA
6. FDMA ( FREQUENCY DIVISION
MULTIPLE ACCESS )
• In FDMA, the entire allocated cellular
frequency spectrum is divided into a
number of 30-kHz channels .
• The power transmitted by a cell is only
large enough to communicate with mobile
stations located near the edge of the cell’s
coverage area.
• The radius of a cell might be one mile or
less-referred to as a small cell
7. TDMA (TIME DIVISION MULTIPLE
ACCESS)
• TDMA is a digital wireless air interface .
• It divides each carrier frequency into a
number of time slots, each of which
constitutes an independent telephone
circuit.
8. CDMA (CODE DIVISION MULTIPLE
ACCESS)
• A digital multiple access technique
specified by the Telecommunications
Industry Association (TIA) as "IS-95."
• One of the unique aspect of CDMA is that
while there are certainly limits to the
number of phone calls that can be handled
by a carrier, this is not a fixed number .
• Code division multiple access (CDMA) is a
digital air interface standard, claiming eight
to fifteen times the capacity of analog.
9. GSM IS A TDMA TECHNIQUE
HISTORY OF GSM
What ?
•GSM: Global System for Mobile
Communications
•Formerly: Group Special Mobile
When ?
• 1982: GSM created to set
standard.
• 1988: Industrial development
started.
• 1991: First Systems Deployed.
10. Why ?
•Higher digital voice quality.
•Low cost alternatives to making calls such as SMS .
•Ability to deploy equipment from different vendors.
GSM
Services
• Tele-services
• Bearer or Data Services
• Supplementary services
11. Tele Services
• Telecommunication services that
enable voice communication via
mobile phones
• Offered services
- Mobile telephony
- Emergency calling
12. BEARER SERVICES
• Short Message Service (SMS)
o up to 160 character alphanumeric data
transmission to/from the mobile terminal
• Unified Messaging Services(UMS)
• Group 3 fax
• Voice mailbox
• Include various data services for information
transfer between GSM and other networks
like PSTN, ISDN etc at rates from 300 to 9600
bps
• Electronic mail
13. 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
15. SYSTEM ARCHITECTURE
Mobile Station (MS): • Mobile Equipment
(ME)
• Subscriber Identity
Module (SIM)
Base Station Subsystem (BSS):
• Base Transceiver Station
(BTS)
• Base Station Controller (BSC)
Network Subsystem:
• Mobile Switching Center (MSC)
• Home Location Register (HLR)
• Visitor Location Register (VLR)
• Authentication Center (AUC)
• Equipment Identity Register (EIR)
16. MOBILE STATION (MS)
• The Mobile Station is made
up of two entities:
• Mobile Equipment (ME)
o The Mobile Equipment is the
hardware used by the subscriber to
access the network .
o Uniquely identified by an IMEI
(International Mobile Equipment
Identity)
o Subscriber Identity Module (SIM)
o Smart card containing the
International Mobile Subscriber
Identity (IMSI)
o Allows user to send and receive calls
and receive other subscribed services
o Protected by a password or PIN
17. BASE STATION SUBSYSTEM
Base Station Subsystem is
composed of two parts :
1) Base Transceiver Station
(BTS)
2) Base Station Controller
(BSC)
• Base Transceiver
Station (BTS)
Houses the radio transceivers
that define a cell
Handles radio-link protocols
with the Mobile Station
18. • Base Station Controller
(BSC)
Manages Resources for BTS
Handles call set up
Location update
Handover for each MS
19. NETWORK SUBSYSTEM
Mobile Services Switching Center (MSC)
Major MSC Functions :
Switching and call routing
Charging
Service provisioning
Communication with HLR
Communication with the VLR
Communication with other MSCs
Control of connected BSCs
Direct access to Internet services
Home Location Registers (HLR) :
Contains administrative information of
each subscriber
Most important database
20. Visitor Location Registers (VLR)
- Integrated with MSC
o tracks which customers have the phone on and
ready to receive a call
o periodically updates the database on which
phones are turned on and ready to receive calls
Authentication Center (AUC)
o mainly used for security
o data storage location and functional part of the
network
o Ki is the primary element
Equipment Identity Register (EIR)
- Database that is used to track handsets using
the IMEI ,Made up of three sub-classes: The
White List, The Black List and the Gray List
o Optional database
21. GSM FREQUENCY ALLOCATION
• GSM systems use radio frequencies
between 890-915 MHz for receive and Downlink
between 935-960 MHz for transmit.
• RF carriers are spaced every 200 kHz,
allowing a total of 124 carriers for use. Uplink
• An RF carrier is a pair of radio frequencies,
one used in each direction.
• Transmit and receive frequencies are
always separated by 45 MHz
UPLINK FREQUENCIES DOWNLINK FREQUENCIES
890 915 935 960
UPLINK AND DOWNLINK FREQUENCY SEPARATED BY 45MHZ
22. GSM SECURITY
GSM Security
MS NETWORK
Random no
Ki Ki Ki Ki
A3 A8 A3 A8
SRES
Kc Kc
SRES Equal
23. EXPLANATION
• On air interface, GSM uses encryption
and TMSI instead of IMSI.
• SIM is provided 4-8 digit PIN to validate
the ownership of SIM
• 3 algorithms are specified :
- A3 algorithm for authentication
- A5 algorithm for encryption
- A8 algorithm for key generation
