04/2009

Overview 1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)

Overview 1. INTRODUCTION TO GSM a. What is GSM b. GSM services c. History d. 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 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 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

1 st 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/s Transmission rate Gaussian Minimum Shift Keying (GMSK) Modulation 200 kHz Carrier Separation 45MHz / 95MHz Duplex distance Uplink: 890 MHz – 915 MHz / 1710 MHz – 1785 MHz Downlink: 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 GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)

Overview 1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE a. Components b. Interfaces

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 PLMN : Public Land Mobile Network BSC : Base Station Controller BTS : Base Transceiver Station MS : Mobile Station

Radio Subsystem

Components PLMN : Public Land Mobile Network ISC : International Switching Center MSC : Mobile Switching Center GMSC : Gateway Mobile Switching Center HLR : Home Location Register VLR : 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

Components AuC : Authentication Center EIR : Equipment Identity Register OMC : Operation and Maintenance Center PLMN : Public Land Mobile Network

Operation Subsystem 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

Network Databases

Summary

Interfaces

Overview 1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK ORGANIZATION 4. GSM NUMBERING 5. 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 GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)

GSM numbering

Permanent subscriber numbering

MSRN & TMSI

IMEI, LAI & CI

Summary

Overview 1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK ORGANIZATION 4. GSM NUMBERING 5. GSM CALLING (MOC, MTC)

Overview 1. INTRODUCTION TO GSM 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)

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