04/2009
1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK
Overview
ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)
1. INTRODUCTION TO GSM
a. What is GSM b. GSM services c. History d. GSM advantages and disadvantages
Overview
GSM (Global System for Mobile communication) is a Worldwide Digital Cellular Communications Network
formerly: Groupe Spéciale Mobile (founded 1982)
used in over 184 countries
The GSM network provides for
mobile voice communication international roaming mobile fax text messaging data services
What is GSM?
GSM is a Second Generation (2G) digital radio
cellular network
Time Division Multiplexing / Multiple access
(TDM/TDMA) are employed
TDM / TDMA allows:
One frequency channel to be subdivided Multiple conversations over a single physical
channel
What is GSM?
Two basic types:
1. Telephony (Teleservices)
Mainly voice services providing capability to communicate with other subscribers
2. Data (Bearer services)
Capacity necessary to transmit appropriate data signals between two access points creating an interface to the network
GSM Subscriber Services
GSM supports the following subscriber services:
1. Dual tone multi frequency (DTMF)
tone signaling scheme used for control purposes E.g. Remote control of an answering machine
2. Facsimile group III
GSM supports CCITT group III Facsimile Special fax converter forms junction between standard analogue fax and GSM FAX
GSM Subscriber Services
3. Short Message Services (SMS)
Messaging facility consisting of maximum 160 alphanumeric characters to or from a mobile station to another
4. Cell Broadcast
Variation of SMS where maximum number of
alphanumeric characters is 93
Can be broadcast to users in a certain
geographical area.
E.g. Traffic congestion warnings
GSM Subscriber Services
5. Voice Mail
Answering machine within the network controlled by the
subscriber
Security code needed to access
6. Fax Mail
Subscriber can receive fax messages at any fax machine
7. Emergency number common number mandatory for all service providers free of charge connection with the highest priority (pre-emption of other
connections possible)
GSM Subscriber Services
GSM supports comprehensive list of supplementary services supporting both data and voice services
The following compromises a partial list:
1. Call forwarding
2. Barring of outgoing calls
3. Advice of charge (AoC)
GSM Supplementary Services
4. Call hold
5. Call waiting
6. Multiparty service
7. Calling line identification presentation / restriction
8. Closed user groups (CUGs)
GSM Supplementary Services
Multiple incompatible networks
Before GSM, the technical incompatibilities
between networks were due to: operation on different radio frequencies use of incompatible signals to control the call setup,
handoff and end of the connection.
Even when the same technological standard
existed between countries: there were usually organisational barriers
pricing / charging schemes were incompatible
An analogue cellular system:
uses frequency modulation (FM) to send data and
signals
Divides the spectrum only into physical channels
of different frequency
Does not offer added services such as Caller ID or
Messaging
Analogue Networks
1st Generation Analogue Networks
USA, Australia
AMPS
1983
C-Netz
1981
Germany, Austria, Portugal, South Africa
1987
UK,
ETACS
1981/86
Scandinavia + 30 other countries
NMT450/900
RadioCom
1985
France
RTMS
1985
Italy
TACS
1985
UK, Ireland, Spain
NTACS/JTACS
1991
Japan
NTT/NTT Hi Cap
1978/88
Japan
CEPT formed a technical study group named
Groupe Spécial Mobile.
The group’s mandate was to:
formulate a specification for a pan-European mobile cellular radio system in 900MHz band Tackle the associated technical, economic and
logistical problems.
How did GSM get established
To provide a European “second
generation” digital network standard
Increase the market for Equipment
Manufacturers
Allow Manufacturing to establish
economy of scale.
Objectives of GSM
1985 – Digital Coded Speech over radio link
chosen as basis for GSM
1986 – Validation Trials held in Paris
1988 – Following successful validation multiple invitations to tender issued
1992 – Commercial Networks Launched
Development Timeline
First portable units were really big and heavy. Called
transportables or “luggables”.
First portable units
The first Ericsson
Handheld introduced in 1987
Adapted from a
police radio design firstly into a NMT- 900 compatible unit.
Later adapted for
the ETACS network.
“Curt” – The Hotline Pocket
Introduced in 1989 Originally introduced in 1989 for the NMT- 900, ETACS and AMPS networks Later adapted for
GSM, and is the first Ericsson GSM phone.
First all digital
mobile
“Olivia” - Hotline
First introduced by Ericsson in 1991
First version used in NMT-900 networks, followed by version for ETACS, D- AMPS/AMPS
Adapted for GSM in
1993
“Sandra”
Introduced by
Ericsson in 1996 Several version
manufactured for AMPS, GSM, DCS, PCD1900/GSM
“Jane”
Frequency Band
Uplink: 890 MHz – 915 MHz / 1710 MHz – 1785 MHz Downlink: 935 MHz – 960 MHz / 1805 MHz – 1880 MHz
45MHz / 95MHz
Duplex distance
200 kHz
Carrier Separation
Gaussian Minimum Shift Keying (GMSK)
Modulation
270 kbit/s
Transmission rate
Time Division Multiple Access (TDMA) (narrow band)
Access Method
Speech coder
Regular Pulse Excitation - Long Term Prediction (RPE-LPC) 13kbit/s
Diversity
Channel coding, Interleaving, Frequency hopping, Adaptive equalization
GSM Specification
Communication
mobile, wireless communication; support for voice and data services
Total mobility
international access, chip-card enables use of access points of different providers
Worldwide connectivity
one number, the network handles localization
High capacity if needed
better frequency efficiency, smaller cells, more customers per cell
High transmission quality
high audio quality and reliability for wireless, uninterrupted phone calls at higher speeds (e.g., from cars, trains)
Security functions
access control, authentication via chip-card and PIN
GSM compared to 1G Systems
What are some of disadvantages of GSM?
There is no perfect system!!
no end-to-end encryption of user data reduced concentration while driving
electromagnetic radiation abuse of private data possible roaming profiles accessible high complexity of the system
several incompatibilities within the GSM standards
What are the trends with mobile phone subscribers worldwide?
Development of mobile telecommunication systems
1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK
Overview
ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)
1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE
a. Components b. Interfaces
Overview
Components
GSM is a PLMN (Public Land Mobile Network)
RSS (Radio Subsystem): covers all radio aspects
BSS (Base Station Subsystem): BSC, BTSs MS (Mobile Station)
NSS (Network and Switching Subsystem): call forwarding,
handover, switching MSC (Mobile Switching Center) HLR (Home Location Register) VLR (Visitor Location Register)
OSS (Operation Subsystem): management of the network
OMC (Operation and Maintenance Center) AuC (Authentication Center) EIR (Equipment Identity Register)
Components
BSC : Base Station Controller BTS : Base Transceiver Station MS : Mobile Station
PLMN : Public Land Mobile Network
Components
Radio Subsystem
Radio Subsystem
ISC : International Switching Center MSC : Mobile Switching Center GMSC : Gateway Mobile Switching Center HLR : Home Location Register VLR : Visitor Location Register
PLMN : Public Land Mobile Network
Components
NSS is the main component of the public mobile
network GSM switching, mobility management, interconnection to other networks, system control
What are the components of the NSS? Mobile Services Switching Center (MSC)
controls all connections via a separated network to/from a mobile terminal within the domain of the MSC - several BSC can belong to a MSC
Home Location Register (HLR)
central master database containing user data, permanent and semi-permanent data of all subscribers assigned to the HLR (one provider can have several HLRs)
Visitor Location Register (VLR)
local database for a subset of user data, including data about all user currently in the domain of the VLR
Network and Switching Subsystem
Network and Switching Subsystem
AuC : Authentication Center
EIR : Equipment Identity Register
OMC : Operation and Maintenance Center
PLMN : Public Land Mobile Network
Components
The OSS (Operation Subsystem) enables centralized operation,
management, and maintenance of all GSM subsystems Components
Authentication Center (AuC)
generates user specific authentication parameters on request of a VLR authentication parameters used for authentication of mobile terminals and encryption of user data on the air interface within the GSM system
Equipment Identity Register (EIR)
registers GSM mobile stations and user rights stolen or malfunctioning mobile stations can be locked and sometimes even localized
Operation and Maintenance Center (OMC)
different control capabilities for the radio subsystem and the network subsystem
Operation Subsystem
Network Databases
Summary
Interfaces
Interfaces
Interfaces
Interfaces
1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK
Overview
ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)
Geographical network organization
•The International GSM/DCS system area comprises all countries where PLMN is implemented •Within these countries, the PLMN are further subdivided into MSC areas
MSC region
•The MSC service areas, in turn, consists of cells which are organized as Location Areas (LA) •Allows MS to move freely without updating location information •System uses LA’s to locate a MS using broadcast messages.
Location area (LA)
1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK
Overview
ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)
GSM numbering
Permanent subscriber numbering
MSRN & TMSI
IMEI, LAI & CI
Summary
1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK
Overview
ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)
INTRODUCTION TO GSM
1. 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK
ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)
a. MOC (Mobile Originated Call) b. MTC (Mobile Terminated Call)
Overview
1, 2: connection
request
3, 4: security check 5-8: check resources
(free circuit) 9-10: set up call
Mobile Originated Call
Mobile Originated Call
1: calling a GSM subscriber 2: forwarding call to GMSC 3: signal call setup to HLR 4, 5: request MSRN from VLR 6: forward responsible MSC to
GMSC
7: forward call to current MSC 8, 9: get current status of MS 10, 11: paging of MS 12, 13: MS answers 14, 15: security checks 16, 17: set up connection
Mobile Terminated Call
Mobile Terminated Call
Detail Sequence of MTC
Future mobile telecommunication networks
