04/2009
Overview
1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK
ORGANIZATION4. GSM NUMBERING5. GSM CALLING (MOC, MTC)
Overview
1. INTRODUCTION TO GSMa. What is GSMb. GSM servicesc. Historyd. GSM advantages and
disadvantages
What is GSM? 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
GSM Subscriber Services
Two basic types:
1. Telephony (Teleservices)Mainly voice services providing capability to communicate with other subscribers2. Data (Bearer services)Capacity necessary to transmit appropriate data signals between two access points creating an interface to the network
GSM Subscriber ServicesGSM 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 IIIGSM supports CCITT group III FacsimileSpecial fax converter forms junction
between standard analogue fax and GSM FAX
GSM Subscriber Services3. Short Message Services (SMS)Messaging facility consisting of maximum 160 alphanumeric characters to or from a mobile station to another
4. Cell BroadcastVariation of SMS where maximum number of alphanumeric characters is 93Can be broadcast to users in a certain geographical area. E.g. Traffic congestion warnings
GSM Subscriber Services5. Voice Mail
Answering machine within the network controlled by the subscriber
Security code needed to access
6. Fax MailSubscriber can receive fax messages at any fax
machine
7. Emergency numbercommon numbermandatory for all service providersfree of chargeconnection with the highest priority (pre-emption of
other connections possible)
GSM Supplementary 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)
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
Analogue Networks
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
1st Generation Analogue Networks
Japan1978/88NTT/NTT Hi Cap
Japan1991NTACS/JTACS
UK, Ireland, Spain1985TACS
Italy1985RTMS
France1985RadioCom
Scandinavia + 30 other countries1981/86NMT450/900
UK, 1987ETACS
Germany, Austria, Portugal, South Africa
1981C-Netz
USA, Australia1983AMPS
How did GSM get established 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.
Objectives of GSM To provide a European “second
generation” digital network standard
Increase the market for Equipment Manufacturers
Allow Manufacturing to establish economy of scale.
Development Timeline 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
First portable units First portable
units were really big and heavy.
Called transportables or “luggables”.
“Curt” – The Hotline Pocket 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.
“Olivia” - Hotline 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
“Sandra” 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
“Jane” Introduced by
Ericsson in 1996 Several version
manufactured for AMPS, GSM, DCS, PCD1900/GSM
GSM Specification
Channel coding, Interleaving, Frequency hopping, Adaptive equalization
Diversity
Regular Pulse Excitation - Long Term Prediction (RPE-LPC) 13kbit/s
Speech coder
Time Division Multiple Access (TDMA) (narrow band)Access Method
270 kbit/sTransmission rate
Gaussian Minimum Shift Keying (GMSK)Modulation
200 kHzCarrier Separation
45MHz / 95MHzDuplex distance
Uplink: 890 MHz – 915 MHz / 1710 MHz – 1785 MHzDownlink: 935 MHz – 960 MHz / 1805 MHz – 1880 MHz
Frequency Band
GSM compared to 1G Systems 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
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
Overview
1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK
ORGANIZATION4. GSM NUMBERING5. GSM CALLING (MOC, MTC)
Overview
1. INTRODUCTION TO GSM2. GSM ARCHITECTURE
a. Componentsb. Interfaces
Components
ComponentsGSM 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
PLMN : Public Land Mobile Network
BSC : Base Station ControllerBTS : Base Transceiver StationMS : Mobile Station
Radio Subsystem
Radio Subsystem
Components
PLMN : Public Land Mobile Network
ISC : International Switching CenterMSC : Mobile Switching CenterGMSC : Gateway Mobile Switching CenterHLR : Home Location RegisterVLR : Visitor Location Register
Network and Switching Subsystem
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
ComponentsAuC : Authentication Center
EIR : Equipment Identity Register
OMC : Operation and Maintenance Center
PLMN : Public Land Mobile Network
Operation SubsystemThe 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
Network Databases
Summary
Interfaces
Interfaces
Interfaces
Interfaces
Overview
1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK
ORGANIZATION4. GSM NUMBERING5. GSM CALLING (MOC, MTC)
Geographical network organization
MSC region•The International GSM/DCS system area comprises all countries where PLMN is implemented•Within these countries, the PLMN are further subdivided into MSC areas
Location area (LA)•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.
Overview
1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK
ORGANIZATION4. GSM NUMBERING5. GSM CALLING (MOC, MTC)
GSM numbering
Permanent subscriber numbering
MSRN & TMSI
IMEI, LAI & CI
Summary
Overview
1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK
ORGANIZATION4. GSM NUMBERING5. GSM CALLING (MOC, MTC)
Overview
1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK
ORGANIZATION4. GSM NUMBERING5. GSM CALLING (MOC, MTC)
a. MOC (Mobile Originated Call)b. MTC (Mobile Terminated Call)
Mobile Originated Call
1, 2: connection request
3, 4: security check
5-8: check resources (free circuit)
9-10: set up call
Mobile Originated Call
Mobile Terminated 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
Detail Sequence of MTC
Future mobile telecommunication networks