Mobile Communication

1. GSM – GLOBAL SYSTEM FOR
MOBILE COMMUNICATION
Debby Nahl
Fall 2004

2. DISCUSSION TOPICS
• History
• Building Blocks
• System Architecture
• Features (Basic and Advanced)
• Advantages of GSM
• Future – what’s next

3. HISTORY
• Early 80’s Europe was experiencing rapid growth
in the analog cellular telephone systems
• 1982 Conference of European Posts and
Telegraphs (CEPT) GSM (Groupe Special Mobile)
group was formed to study and develop a pan-
European public land mobile system
• GSM mandate was to develop a standard to be
common for the countries that created it – provide
service to the entire European continent

4. HISTORY
contd.
• GSM criteria –
– Good subjective speech quality
– Low terminal and service cost
– Support for international roaming – one system for all of Europe
– Ability to support handheld terminals
– Support for range of new services and facilities
– Enhanced Features
– ISDN compatibility
– Enhance privacy
– Security against fraud

5. HISTORY
contd.
• Late 1980’s GSM work was transferred to the
European Telecommunication Standards Institute
(ETSI) and SGM (Special Mobile Group) was
created
• Document the functionality and interaction of every
aspect of the GSM network
• 1987 ETSI oversees the creation of GSM MoU
(Memorandum of Understanding) Association

6. HISTORY
contd.
• Formal objective of the GSM MoU Association is the
promotion and evolution of the GSM systems and GSM
platforms
• Concepts of a published international standard and a
constantly evolving common standard are unique to GSM
• Work groups throughout the world specifically designed to
allow interested parties to meet and work on finding
solutions to systems enhancements that will fit into
existing programs of GSM operators

7. HISTORY
contd.
• Phase I of GSM specifications was published in 1990
• International demand was so great that the system name
was changed from Groupe Special Mobile to Global
Systems for Mobile Communications (still GSM)
• Commercial service started in mid-1991
• 1992 first paying customers were signed up for service
• By 1993 there were 36 GSM networks in 22 countries
• Early 1994 there were 1.3 million subscribers worldwide
• By 1996 there were more than 25 million subscribers
worldwide
• By October 1997 it had grown to more than 55 million
subscribers worldwide

8. Building Blocks
• AMPS – Advanced Mobile Phone System
• TACS – Total Access Communication System
• NMT – Nordic Mobile Telephone System

9. Building Blocks
contd.
AMPS – Advanced Mobile Phone System
• analog technology
• used in North and South America and
approximately 35 other countries
• operates in the 800 MHz band using FDMA
technology

10. Building Blocks
contd.
TACS – Total Access Communication System
• variant of AMPS
• deployed in a number of countries
• primarily in the UK

11. Building Blocks
contd.
NMT – Nordic Mobile Telephone System
• analog technology
• deployed in the Benelux countries and Russia
• operates in the 450 and 900 MHz band
• first technology to offer international roaming – only within
the Nordic countries

12. System Architecture
• Mobile Station (MS)
Mobile Equipment (ME)
Subscriber Identity Module (SIM)
• Base Station Subsystem (BBS)
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)

13. System Architecture
Mobile Station (MS)
The Mobile Station is made up of two entities:
1. Mobile Equipment (ME)
2. Subscriber Identity Module (SIM)

14. System Architecture
Mobile Station (MS) contd.
Mobile Equipment
• Produced by many different manufacturers
• Must obtain approval from the standardization
body
• Uniquely identified by an IMEI (International
Mobile Equipment Identity)

15. System Architecture
Mobile Station (MS) contd.
Subscriber Identity Module (SIM)
• Smart card containing the International Mobile
Subscriber Identity (IMSI)
• Allows user to send and receive calls and receive other
subscribed services
• Encoded network identification details
• Protected by a password or PIN
• Can be moved from phone to phone – contains key
information to activate the phone

16. System Architecture
Base Station Subsystem (BSS)
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)

17. System Architecture
Base Station Subsystem (BSS) contd.
Base Transceiver Station (BTS)
• Houses the radio transceivers that define a cell
• Handles radio-link protocols with the Mobile Station
• Speech and data transmissions from the MS are
recoded
• Requirements for BTS:
ruggedness
reliability
portability
minimum costs

18. System Architecture
Base Station Subsystem (BSS) contd.
Base Station Controller (BSC)
• Manages Resources for BTS
• Handles call set up
• Location update
• Handover for each MS

19. System Architecture
Network Subsystem
Mobile Switching Center (MSC)
• Switch speech and data connections between:
Base Station Controllers
Mobile Switching Centers
GSM-networks
Other external networks
• Heart of the network
• Three main jobs:
1) connects calls from sender to receiver
2) collects details of the calls made and received
3) supervises operation of the rest of the network components

20. System Architecture
Network Subsystem contd.
• Home Location Registers (HLR)
- contains administrative information of each subscriber
- current location of the mobile
• Visitor Location Registers (VLR)
- contains selected administrative information from the HLR
- authenticates the user
- tracks which customers have the phone on and ready to
receive a call
- periodically updates the database on which phones are
turned on and ready to receive calls

21. System Architecture
Network Subsystem contd.
• Authentication Center (AUC)
- mainly used for security
- data storage location and functional part of the network
- Ki is the primary element
• 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 Gray List
- Optional database

22. System Architecture

23. Basic Features Provided by GSM
• 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

24. Advanced Features Provided by
GSM
• Calling Line ID
- incoming telephone number displayed
• Alternate Line Service
- one for personal calls
- one for business calls
• Closed User Group
- call by dialing last for numbers
• Advice of Charge
- tally of actual costs of phone calls
• Fax & Data
- Virtual Office / Professional Office
• Roaming
- services and features can follow customer from market to market

25. Future -- UMTS (Universal Mobile
Telephone System
• Reasons for innovations
- new service requirements
- availability of new radio bands
• User demands
- seamless Internet-Intranet access
- wide range of available services
- compact, lightweight and affordable terminals
- simple terminal operation
- open, understandable pricing structures for the whole spectrum of
available services

26. Advantages of GSM
• Crisper, cleaner quieter calls
• Security against fraud and eavesdropping
• International roaming capability in over 100 countries
• Improved battery life
• Efficient network design for less expensive system expansion
• Efficient use of spectrum
• Advanced features such as short messaging and caller ID
• A wide variety of handsets and accessories
• High stability mobile fax and data at up to 9600 baud
• Ease of use with over the air activation, and all account information
is held in a smart card which can be moved from handset to
handset