GSM(Global System For Mobile) Communication

1. GSM
Presented by-
Navin
A
Seminar
on

2. GSM (Global System for Mobile Communications, originally Groupe
Special Mobile), is a standard developed by the European
Telecommunications Standards Institute (ETSI) to describe the protocols for
second-generation (2G) digital cellular networks used by mobile, first
deployed in Finland in July 1991.
What is GSM ?
"GSM" is a trademark owned by the GSM Association.

3. The GSM study group aimed to provide the followings through
the GSM:
 Improved spectrum efficiency.
 International roaming.
Low-cost mobile sets and base stations (BSs).
 High-quality speech.
Compatibility with Integrated Services Digital Network
(ISDN) and other telephone company services.
Support for new services
Why GSM ?

4.  Tele-services
 Bearer or Data Services
 Supplementary services
GSM SERVICES

5. • Telecommunication services that enable voice
communication via mobile phones
• Offered services
- Mobile telephony
- Emergency calling
Tele Services

6.  Voice mailbox
 Electronic mail
 Include various data services for information transfer
between GSM and other networks like PSTN, ISDN etc. at
rates from 300 to 9600 kbps
 Short Message Service (SMS),alphanumeric data transmission
to/from the mobile terminal.
Bearer Services

7. 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
Supplementary Services

8. GSM Specification
Two main standard of GSM :-
1. GSM 900 – Designed for extensive radio coverage in rural areas
2. GSM 1800 – Designed for radio coverage in areas with very high subscriber
density.
RF Spectrum
GSM 900
Mobile to BTS (uplink): 890-915 MHz
BTS to Mobile(downlink):935-960 MHz
Bandwidth : 2* 25 MHz
GSM 1800
Mobile to BTS (uplink): 1710-1785 MHz
BTS to Mobile(downlink) 1805-1880 MHz
Bandwidth : 2* 75 MHz

9. Cell
is the radio coverage area of
one base transceiver station
Cellular
Networking technology that
breaks geographic area into
cells shaped like honey
comb
1
2
3
4
5
6
7
6
7
2
1
5
GSM Concepts -
Cellular Structure

10. Why a hexagon and not other geometrical shape
represent cells?
• When showing a cellular system we want to depict an area totally
covered by radio, without any gaps.
• The circles leave gaps
• Also for a given area, among square, triangle and hexagon, radius
of a hexagon will be the maximum which is needed for weaker
mobiles.

11. GSM SYSTEM ARCHITECTURE

12. 4 Basic interconnected Subsystem :
Mobile Station (MS)
Base station Subsystem (BSS)
Network and Switching Subsystem (NSS)
Operation Support Subsystem (0SS)

13. Mobile Station (MS)
The Mobile Station is made up of two entities:
1. Mobile Equipment (ME)
2. Subscriber Identity Module (SIM)
Mobile Equipment
 Voice and data transmission
 Portable, vehicle mounted, hand held device
 Uniquely identified by an IMEI (International Mobile
Equipment Identity).

14. Subscriber Identity Module (SIM)
• Portable Smart Card with memory (ROM-6KB to
16KB-A3/A8 algorithm, RAM- 128KB TO
256KB, EEPROM- 3KB to 8KB )
• Static Information
International Mobile Subscriber Identity(IMSI)
is the unique 15 digit( 3 for country code, 3 for mobile
network code and 9 for mobile ID )identity number
resides in SIM.
Personal Identification Number (PIN)
Authentication Key (Ki)
• Dynamic Information
Temporary Mobile Subscriber Identity(TMSI)
Location Area Identity (LAI)
Phone memories, billing information
Ability to store Short Messages received

15. Base Station Subsystem is composed of
two parts that communicate across the
standardized Abis interface allowing
operation between components made by
different suppliers
1. Base Transceiver Station (BTS)
2. Base Station Controller (BSC)
Base Station Subsystem (BSS)
Base Transceiver Station (BTS)
Base Station Controller (BSC)

16.  Base Transceiver Station (BTS):
• Encodes, encrypts, multiplexes, modulates and feeds the RF signals to the
antenna.
• Communicates with Mobile station and BSC
• Consists of Transceivers (TRX) units
 Base Station Controller (BSC):
• Manages Radio resources for BTS
• Assigns Frequency and time slots for all MS’s in its area
• Handles call set up
• Transcoding and rate adaptation functionality
• Handover for each MS
• Radio Power control
• It communicates with MSC and BTS

17.  Mobile Switching Centre (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
- Inter BSS and inter MSC call handoff
Network Switching Subsystem(NSS)
MSC

18. Home Location Registers (HLR)
• Permanent database about mobile subscribers in a large service
area(generally one per GSM network operator)
• database contains IMSI ,MSISDN , prepaid/post-paid , 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
• Reduces number of queries to HLR
• Database contains IMSI , TMSI,MSISDN,MSRN,Location Area,
authentication key

19.  The OSS (Operation Subsystem) enables centralized operation,
management, and maintenance of all GSM subsystems
Components
 Operation and Maintenance Center (OMC)
Mainly does three operation
1.To maintain all telecommunication hardware and network operation
with a particular market.
2. Manage all charging and billing procedure
3.Manage all mobile equipment in the system.
Operation Support System (OSS)

20.  Authentication Centre (AUC)
• Protects against intruders in air interface
• Maintains authentication keys and algorithms and provides
• security triplets ( RAND , SRES ,Kc)
 Equipment Identity Register (EIR)
• Database that is used to track handsets using the IMEI
(International Mobile Equipment Identity)
• Made up of three sub-classes: The White List, The Black List and
the Grey List

21. GSM Frame Structure

22. Speech decoding
Channel decoding
De-interleaving
Burst Formatting
De-ciphering
DemodulationModulation
Ciphering
Burst Formatting
Interleaving
Channel Coding
Speech coding
Radio Interface
Speech Speech
13 Kbps
22.8 Kbps
22.8 Kbps
33.6 Kbps
33.6 Kbps
270.83 Kbps
GSM Operation from transmitter to receiver

23. Example: GSM location update (1)
ME
SIM
HLR
MSC
VLR 1
Most recently allocated Temporary Mobile Subscriber Identity (TMSI) and
last visited LAI (Location Area ID) are stored in SIM even after switch-off.
After switch-on, MS monitors LAI. If stored and monitored LAI values are
the same, no location updating is needed.
(most generic scenario)
MSC
VLR 2
LAI 1
IMSI
TMSI
LAI 1
IMSI
TMSI
IMSI
LAI 1
(in broadcast messages)

24. GSM location update (2)
ME
SIM
MSC
VLR 1
Different LAI values => location update required !
MSC
VLR 2
LAI 2
HLR
IMSI
LAI 1
IMSI
TMSI
LAI 1
IMSI
TMSI
(in broadcast
messages)

25. GSM location update (3)
ME
SIM
MSC
VLR 1
SIM sends old LAI and TMSI to VLR 2.
VLR 2 does not recognize TMSI since there is no TMSI-IMSI context. Who
is this user?
MSC
VLR 2
LAI 1, TMSI
HLR
IMSI
LAI 1
IMSI
TMSI
LAI 1
IMSI
TMSI
No TMSI - IMSI
context

26. GSM location update (4)
ME
SIM
MSC
VLR 1
However, VLR 2 can contact VLR 1 (address: LAI 1) and request IMSI.
IMSI is sent to VLR 2.
MSC
VLR 2
HLR
IMSI
LAI 1
IMSI
TMSI
LAI 1
IMSI
TMSI IMSI
TMSI
IMSI address:
LAI 1

27. GSM location update (5)
ME
SIM
MSC
VLR 1
Important: HLR must be updated (new LAI). If this is not done, incoming
calls can not be routed to new MSC/VLR.
HLR also requests VLR 1 to remove old user data.
MSC
VLR 2
HLR
IMSI
LAI 1
LAI 2
IMSI
TMSI
LAI 1
IMSI
TMSI
IMSI
TMSI
LAI 2

28. GSM location update (6)
ME
SIM
MSC
VLR 1
VLR 2 generates new TMSI and sends this to user. User stores new LA2
and TMSI safely in SIM.
Location update successful !
MSC
VLR 2
HLR
IMSI
LAI 2
LAI 1
IMSI
TMSI
LAI 2
TMSI
IMSI
TMSI
TMSI
LAI 2
TMSI

29. MS sends dialled number to BSS
BSS sends dialled number to MSC
MSC checks VLR if MS is allowed the
requested service.
If so, MSC asks BSS to allocate resources for
call.
MSC routes the call to GMSC
GMSC routes the call to local exchange of
called user.
Answer back(ring back) tone is routed from
called user to MS via GMSC,MSC,BSS
Outgoing Call
 Call Originating from MS
 Call termination to MS

30. Incoming Call
Calling a GSM subscribers
Forwarding call to GSMC
Signal Setup to HLR
5. Request MSRN from VLR
Forward responsible MSC to GMSC
Forward Call to current MSC
9. Get current status of MS
11. Paging of MS
13. MS answers
15. Security checks
17. Set up connection

31. ADVANTAGES OF GSM :-
 It can be use repeaters.
 It is easy to implement.
 International roaming is not a big problem.
DISADVANTAGES OF GSM:-
 Manufactures are not release IS-95 devices due to the lack
of the big market and it come in late in market.
 GSM has fixed max call sites range up to 35 km that is very
limited.

32. Development of the Market Share of Mobile Standards
Mobile phone subscribers by technology (left Y axis) and
total number of subscribers globally (right Y axis)
In a fast-growing market, GSM/3GSM (red) grows faster than the market and is
gaining market share, the CDMA family (blue) grows at about the same rate as the
market, while other technologies (grey) are being phased out.

33. GSM in India

34. 2nd Generation
GSM -9.6 Kbps (data rate)
2.5 Generation ( Future of GSM)
HSCSD (High Speed ckt Switched data)
Data rate : 76.8 Kbps (9.6 x 8 kbps)
GPRS (General Packet Radio service)
Data rate: 14.4 - 115.2 Kbps
EDGE (Enhanced data rate for GSM Evolution)
Data rate: 547.2 Kbps (max)
 3 Generation
WCDMA(Wide band CDMA)
Data rate : 0.348 – 2.0 Mbps
 3.5 Generation
High Speed Downlink Packet Access(HSDPA)
Data rate : 1.4– 5.8 Mbps
 4 Generation
Long Term Evolution (LTE)
Data rate : up to 20.0 Mbps
FUTURE OF GSM