Charging Requirements for UMTS Packet-Switched Data Services
`
`Charging Requirements for UMTS Packet -Switched
`Data Services
`
`Report Number: EX 001/2001
`
`By
`Taiwo Oyedele
`
`A Thesis work in Mobile Communications for the
`Department of Computing and Electronic Engineering
`Chalmers University of Technology
`Gothenburg, Sweden
`
`Chalmers University of Technology
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`Page 1
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`Intellectual Ventures Inc. LLC Ex. 2010
`Ericsson Inc. v. Intellectual Ventures
`IPR2018-01380
`
`

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`Charging Requirements for UMTS Packet -Switched Data Services
`
`Acknowledgement
`
`I would like to express my gratitude and appreciation for the invaluable guidance, helpful suggestions,
`encouragement and support given by Pete Barron. I would also like to thank Nigel Lobley, Nadir El
`Yakhlifi, Uduak Ekpe and all the members of the Mobile Network Design group at BT Adastral Park,
`who have in one way or the other influenced and contributed positively to the project work presented in
`this thesis.
`
`I also express thanks to all my lecturers both at Chalmers University of Technology and at University
`College London for the knowledge I gained from the course, which has been invaluable to the
`completion of this project. Special thanks to Erik Ström for his outstanding guidance and
`encouragement throughout the project phase.
`
`Gratitude and appreciation is also extended to my family for the support provided to me throughout the
`duration of my Masters course. Above all I would like to show my thanks and appreciation to God for
`enabling me to successfully complete my Masters programme.
`
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`Charging Requirements for UMTS Packet-Switched Data Services
`
`Abstract
`
`Why do we need new charging mechanisms? Packet-Switched services do not require a dedicated path
`for the duration of the call. Instead, they rely on a virtual connection with the network setting up a real
`connection only when there is data to be sent/received, and then dropping the connection until more
`data is ready to be transmitted or received. As a result, network resources are used only when packets
`are in transmission, and there is thus no clear notion of “the duration of a call”. Hence, users may no
`longer wish to be charged in the traditional duration-based manner. Besides, in contrast to today’s
`dedicated networks, (e.g. PSTN, Frame Relay and even GSM) which carry a single application type at
`a fixed duration-based price, General Packet Radio Service (GPRS) and UMTS are multi-service
`networks. These require flexible pricing models, where price is a function of data volume, QoS
`provisioned, packet content, etc. For example, voice and video data is more or less continuous, thus
`requiring network resources more or less for the entire duration of its transfer. Consequently, we can
`expect voice and video to have a flat per-minute rate, whereas other services, such as, Resource (e.g.
`file) Access and fax/email applications may be charged on a volume basis, i.e. charged per MB of data
`transferred. Moreover, voice and video applications require bi-directional latency and bandwidth
`guarantees, whereas Resource Access and fax/email applications do not have the latency constraint, but
`may require significant bandwidth depending on the resource being accessed. Hence, QoS plays a
`significant role in most new charging mechanisms. In other words, a flexible charging mechanism
`capable of measuring and rating services under various usage-based metrics is paramount.
`
`Due to the packet-based nature of the underlying network technology, these services require novel
`charging mechanisms, which in turn require extensive data-extraction from various network service
`elements. This document is not intended to be a technical specification sufficient for practical
`implementation of network-usage data extraction among service elements participating in the delivery
`of UMTS IP-based services. Such a technical specification is left to standards bodies and associations
`like 3GPP, IPDR.org GBA etc. Instead, it is intended to highlight the possible mechanisms that may be
`implemented for charging UMTS services. It also identifies the network requirements, the limitations
`and more importantly the possibilities these new charging schemes open up for Mobile Network
`Operators also known as PLMN operators. Some of these possibilities include additional revenue
`streams like acquisition of financial transactions, as opposed to solely being a voice/data ‘carrier
`provider’, as is the case with traditional PLMN operators. The project involved lots of information
`gathering from the Internet, technical papers, magazines and suppliers. It also required a need to work
`with people from across BT, Adastral Park to determine their views on how technology will affect the
`future user experience, and hence, future charging schemes for packet based services.
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`Charging Requirements for UMTS Packet -Switched Data Services
`
`Table of Contents
`
`Definitions and Abbreviations ………………………………………...6
`Introduction……………………………………………………………..9
`1 GSM ........................................................................................... 11
`1.1
`HISTORY..................................................................................................................................................11
`1.2
`CELLULAR SYSTEMS.............................................................................................................................12
`1.3
`GSM FEATURES AND SERVICES..........................................................................................................13
`1.3.1
`Bearer services ............................................................................................................................ 14
`1.3.2
`Tele Services ................................................................................................................................ 14
`1.3.3
`GSM Supplementary Services................................................................................................... 14
`1.3.4
`Advanced Supplementary Services........................................................................................... 15
`1.4
`GSM NETWORK ARCHITECTURE AND FUNCTIONAL ELEMENTS....................................................15
`1.4.1
`The Mobile Station (MS)............................................................................................................ 15
`1.4.2
`The Base Station Subsystem (BSS)........................................................................................... 16
`1.4.3
`The Network Switching Subsystem (NSS)............................................................................... 16
`PRE-PAID SERVICE (PPS)......................................................................................................................18
`1.5
`1.5.1
`Benefits of Pre-paid.................................................................................................................... 19
`1.5.2
`Network Structure....................................................................................................................... 19
`CALL SCENARIOS...................................................................................................................................19
`1.6
`1.6.1
`Mobile Originated call............................................................................................................... 20
`1.6.2
`Mobile Terminated Call............................................................................................................. 21
`GSM CHARGING ARCHITECTURE .......................................................................................................22
`1.7
`1.7.1
`Mobile Originated Calls............................................................................................................ 22
`1.7.2
`Mobile Terminated Calls........................................................................................................... 23
`1.7.3
`Call Data Record Parameters................................................................................................... 25
`1.7.4
`Pre-paid Service Charging........................................................................................................ 25
`SUMMARY OF THE GSM CHARGING SCHEME....................................................................................26
`1.8
`2 GPRS.......................................................................................... 28
`2.1
`GPRS OVERVIEW...................................................................................................................................28
`2.2
`MIGRATION FROM CIRCUIT -SWITCHED TO PACKET-SWITCHED NETWORKS...............................30
`GPRS FEATURES AND SERVICES, BENEFITS AND REQUIREMENTS................................................33
`2.3
`2.3.1
`Features and Services ................................................................................................................ 33
`2.3.2
`Benefits.......................................................................................................................................... 34
`2.3.3
`GPRS Requirements.................................................................................................................... 34
`GPRS NETWORK ARCHITECTURE AND FUNCTIONAL ELEMENTS..................................................35
`2.4
`2.4.1
`GPRS Mobile Terminal.............................................................................................................. 35
`2.4.2
`Serving GPRS Support Node (SGSN)...................................................................................... 36
`2.4.3
`Gateway GPRS Support Node (GGSN)................................................................................... 37
`2.4.4
`Domain Name Server (DNS)..................................................................................................... 38
`2.4.5
`HLR................................................................................................................................................ 38
`CONNECTING TO THE NETWORK..........................................................................................................38
`2.5
`2.5.1
`GPRS Attach ................................................................................................................................ 38
`2.5.2
`PDP Context Activation............................................................................................................. 39
`2.5.3
`Packet Transfer ........................................................................................................................... 40
`2.6
`CALL SCENARIOS...................................................................................................................................42
`3 UMTS......................................................................................... 44
`3.1
`UMTS OVERVIEW.................................................................................................................................44
`3.2
`UMTS FEATURES AND SERVICES, REQUIREMENTS AND BENEFITS...............................................45
`3.2.1
`UMTS Features and Services.................................................................................................... 45
`3.2.2
`UMTS Requirements................................................................................................................... 46
`3.2.3
`UMTS benefits ............................................................................................................................. 46
`UMTS NETWORK ARCHITECTURE AND FUNCTIONAL ELEMENTS.................................................47
`3.3
`3.3.1
`UMTS Subscriber Identity Module (USIM)............................................................................ 47
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`Node B........................................................................................................................................... 48
`3.3.2
`Radio Network Controller (RNC)............................................................................................. 48
`3.3.3
`Media Gateway and The Media Gateway Control Function (MGCF).............................. 48
`3.3.4
`Call Server Control Function (CSCF)..................................................................................... 48
`3.3.5
`4 PACKET-BASED CHARGING................................................. 49
`4.1
`GPRS/UMTS CHARGING ARCHITECTURE ........................................................................................49
`PACKET-BASED BILLING ISSUES.........................................................................................................50
`4.2
`4.2.1
`Volume and complexity of Charge Data Records.................................................................. 51
`4.2.2
`Complexity and Flexibility Requirement of Packet-Based Billing Systems...................... 51
`4.2.3
`GPRS/UMTS Pre-Paid charging.............................................................................................. 52
`4.3
`POTENTIAL REVENUE OPPORTUNITIES FOR GPRS/UMTS NETWORK OPERATORS......................53
`4.3.1
`Legacy ‘Carrier’ or ‘Data pipe provider’.............................................................................. 53
`4.3.2
`Provider of Personalised and Location-based “push” services......................................... 53
`4.3.3
`Internet Service Provider or Portal-type service provider.................................................. 54
`4.3.4
`Partnerships with Content providers....................................................................................... 55
`4.3.5
`Payment Method Provider......................................................................................................... 55
`RECORD TYPES.......................................................................................................................................57
`4.4
`4.4.1
`S-CDR ........................................................................................................................................... 57
`4.4.2
`M-CDR .......................................................................................................................................... 58
`4.4.3
`G-CDR .......................................................................................................................................... 58
`4.4.4
`S-SMO-CDR and S-SMT-CDR ................................................................................................. 58
`4.5
`RECORD CONTENTS...............................................................................................................................59
`4.5.1
`Charging ID (CID) ..................................................................................................................... 59
`4.5.2
`List of Traffic Data Volumes ..................................................................................................... 59
`4.5.3
`Access Point Name (APN)......................................................................................................... 60
`4.5.4
`Charging Characteristics.......................................................................................................... 60
`4.5.5
`Quality of Service (QoS)............................................................................................................ 61
`NETWORK INFRASTRUCTURE REQUIRED FOR BILLING PURPOSES.................................................65
`4.6
`4.6.1
`Charging Gateway Functionality............................................................................................. 66
`4.6.2
`Mediation...................................................................................................................................... 67
`PACKET BASED CHARGING MODELS..................................................................................................70
`4.7
`4.7.1
`Duration based ............................................................................................................................ 71
`4.7.2
`Subscription-based...................................................................................................................... 73
`4.7.3
`Volume Based .............................................................................................................................. 75
`4.7.4
`Combination of Subscription and Volume-based or duration-based................................. 77
`4.7.5
`Event-based.................................................................................................................................. 79
`4.7.6
`Content value based.................................................................................................................... 80
`SUMMARY OF PACKET-SWITCHED CHARGING MODELS..................................................................82
`4.8
`5 CONCLUSION........................................................................... 84
`6 APPENDICES ............................................................................ 86
`
`7 REFERENCES........................................................................... 99
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`Charging Requirements for UMTS Packet -Switched Data Services
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`Definitions and Abbreviations
`
`Network Operator: A company providing the network infrastructure required for administering
`various telecommunications services.
`
`Node: Part of the Network infrastructure. Could be a host, server, switch, router or a base station.
`
`Service Provider: A company administering the services provided by the Network Operator. May or
`may not be a Network Operator.
`
`R99 and R00: The specifications are grouped into 'Releases'. The original specifications were
`published by ETSI in 1994 and are now known as 'Phase 1'. The next releases were known as 'Phase 2',
`and 'Phase 2+' respectively. Within Phase 2+, there have been annual releases since 1996, which are
`known as R96, R97, R98, R99 and R00.
`
`3G
`3GPP
`AAA
`ADSL
`AMPS
`ARPU
`ATM
`AUC
`BS
`BSC
`BSS
`BTS
`CCCH
`CDMA
`CDR
`CEPT
`CGF
`CID
`CL
`CO
`CS
`CSCF
`DHCP
`ECSD
`EDGE
`EIR
`ETSI
`FDD
`FTP
`G-CDR
`GGSN
`GMSC
`GPRS
`GSM
`GSN
`GTP
`HLR
`HSCSD
`HTML
`IETF
`IMEI
`IMSI
`IN
`IP
`IPDR
`
`3rd Generations
`3G Partnership Project
`Authentication, Authorisation, and Accounting
`Asymmetric Digital Subscriber Line
`Advanced Mobile Phone System
`Average Revenue Per User
`Asynchronous Transfer Mode
`Authentication Centre
`Billing System or Base Station depending on context
`Base Station Controller
`Business Support System
`Base Transceiver System
`Common Control Channels
`Code Division Multiple Access
`Call Detail Record
`Conference of European Posts and Telecommunications
`Call Gateway Functionality
`Charging Identity
`Connectionless
`Connection Oriented
`Circuit Switched
`Call Server Control Function
`Dynamic Host Configuration Protocol
`Enhanced Circuit Switched Data
`Enhanced Data rates for GSM Evolution
`Equipment Identification Register
`European Telecommunications Standards Institute
`Frequency Division Duplex
`File Transfer Protocol
`GGSN CDR
`Gateway GPRS Support Node
`Gateway Mobile Switching Centre
`General Packet Radio Service
`Global System for Mobile Communications
`GPRS Support Node
`GPRS Tunnelling Protocol
`Home Location Register
`High Speed Circuit Switched Data
`Hyper Text Mark-up Language
`Internet Engineering Task Force
`International Mobile Equipment Identity
`International Mobile Subscriber Identity
`Intelligent Network
`Internet Protocol
`Internet Protocol Detail Record
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`Charging Requirements for UMTS Packet-Switched Data Services
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`ISDN
`ISP
`ITU-T
`IWF
`LAN
`M-CDR
`ME
`MGCF
`MM
`MO
`MS
`MSC
`MSISDN
`MT
`MTU
`MoU
`NAMTS
`NAS
`NE
`NMT
`NSS
`OLO
`OMC
`OSI
`PBX
`PCM
`PDA
`PDN
`PDP
`PDU
`PLMN
`PPS
`PS
`PSTN
`PTM
`P-TMSI
`PTP
`QoS
`RA
`RAB
`RAI
`RAN
`RADIUS
`RLA
`RNC
`RSVP
`SACCH
`S-CDR
`SDU
`SIM
`SGSN
`SMS
`TACS
`TAP
`TBF
`TCP
`TDD
`TDMA
`TID
`UDP
`
`Integrated Services Digital Network
`Internet Service Provider
`International Telecommunications Union –Telecommunications Sector
`Inter-Working Functions
`Local Area Network
`Mobility CDR
`Mobile Equipment
`Media Gateway Control Function
`Mobility Management
`Mobile Originated
`Mobile Station
`Mobile Switching Centre
`Mobile Subscriber ISDN number
`Mobile Terminated or Mobile Terminal depending on context
`Maximum Transmission Units
`Memorandum of Understanding
`Nippon Advanced Mobile Telephone System
`Network Access Server
`Network Element
`Nordic Mobile Telecommunications
`Network Switching Subsystem
`Other Licensed Operators
`Operations & Maintenance Centre
`Open Systems Interface
`Private Branch Exchange
`Pulse Code Modulation
`Personal Digital Assistant
`Packet Data Network
`Packet Data Protocol
`Packet Data Unit
`Public Land Mobile Network
`Pre-Paid Service
`Packet Switched
`Public Switched Telephone Network
`Point-to-Multipoint
`Packet-Temporary Mobile Subscriber Identity
`Point-to-Point
`Quality of Service
`Routing Area
`Radio Access Bearer
`Routing Area Identity
`Radio Access Network
`Remote Access Dial-In User Service
`Remote LAN Access
`Radio Network Controller
`Resource reSerVation Protocol
`Slow Associated Control Channel
`SGSN CDR
`Service Data Unit
`Subscriber Identity Module
`Serving GPRS Support Node
`Short Message Service
`Total Access Telecommunications Systems
`Transfer Accounting Procedure
`Temporary Block Flow
`Transport Control Protocol
`Time Division Duplex
`Time Division Multiple Access
`Tunnelling Identity
`User Datagram Protocol
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`UE
`UMTS
`USIM
`USSD
`UTRAN
`VLR
`VMSC
`VoIP
`VoD
`WAP
`W-CDMA
`WML
`
`User Equipment
`Universal Mobile Telecommunications System
`UMTS SIM
`Unstructured Supplementary Services Data
`UMTS Terrestrial Radio Access Network
`Visitor Location Register
`Visited Mobile Switching Centre
`Voice Over IP
`Video on Demand
`Wireless Application Protocol
`Wide-band CDMA
` Wireless Mark-up Language
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`Charging Requirements for UMTS Packet-Switched Data Services
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`Introduction
`
`High-bandwidth networks with sophisticated security features and fast evolving Quality of Service
`(QoS) mechanisms, enables Service Providers (both fixed wire-line and wireless) to offer packet-based
`services, traditionally provided by Circuit-Switched networks. Already, we see services such as,
`telephone, fax, pay-per-view-movies, video-conferencing, secure remote access, secure corporate
`network interconnection (VPN services), electronic commercial transactions, TV and radio broadcasts,
`all carried over IP networks. The Universal Mobile Telecommunications System (UMTS) network
`providing very high data rates and enabling end-to-end QoS is intended to support all of these services
`and applications – thus, enabling complete wireless Internet access. Since the existing flat-rate pricing
`model, usually applied for IP services, simply does not apply to these resource-hungry, performance-
`oriented applications, a comprehensive IP-metering system coupled with the UMTS-Call Detail Record
`system is required to bring these services to market. Furthermore, customers need to control their
`communications expenses and will choose providers not just based on cost, QoS options etc but also on
`their ability to measure and rate services under various usage-based metrics. Apart from the off-peak
`discounts existing in traditional billing and rating systems, UMTS billing systems will include a QoS
`discount, since the network may fail to meet the QoS level specified by the application. This inability
`of the network to meet the QoS profile requested is likely, particularly in early network deployments.
`
`The UMTS network preceded in most cases by GPRS integrates two of the world’s fastest growing
`industries – mobile communications and the Internet. It is intended to support a wide range of voice,
`data, and multimedia services and applications. Since GPRS/UMTS is IP-based, it is fully compatible
`with the Internet and truly provides the capability to extend the Internet to the mobile phone. The
`UMTS network can be viewed as a sub-network of the Internet with UMTS-capable handsets being
`viewed as mobile hosts. The implementation of a fully functional and commercially viable UMTS
`network is however faced by technological and commercial challenges, some of which include
`
`
`
`Issues such as battery life, cost, monitoring of paging channels etc associated with its “Always on”
`“Always connected” functionality.
` Billing issues - How do we charge for packet-based services and who is billed for Mobile
`Terminated traffic.
`Security concerns (Spam/Viruses) – Unwanted/unsolicited data, pushing information to UMTS-
`handsets could result in virus threat, etc.
` Radio resource usage and optimisation
`
`
`
`The main subject of this document however, is the billing issue. This document has been divided into
`four main chapters – GSM, GPRS, UMTS and Packet-Based Charging. For those with prior
`knowledge/experience in GSM and/or GPRS, refer to chapter 4 for packet-based billing issues.
`
`The GSM chapter gives a brief summary of the history of GSM; includes an overview of general
`cellular concepts and describes some of the features and services supported by the GSM network
`infrastructure. Then, a description of the separate but dependent network subsystems and individual
`components is given before moving on to address the charging scheme employed within GSM. Billing
`within the Pre-Paid Service is also discussed.
`
`The GPRS chapter aims to give a general overview of the GPRS network, identify the key differences
`between GPRS and GSM standards and technologies, and briefly discusses the services intended to be
`supported by GPRS, and the network requirements to support these services.
`
`The UMTS chapter describes the network infrastructure and the new network elements and thus new
`services and applications supported by UMTS. It also identifies the main differences between GPRS
`and UMTS, i.e. radio modulation technique and its ability to support real-time- as well as non-real-time
`applications, as opposed to the constraint imposed on GPRS to only support non-real-time applications.
`This additional functionality requires enhanced network requirements to enable the production and
`collection of relevant Call Detail Records (CDRs) for flexible charging mechanisms.
`
`Chapter 4 describes the charging functionality within GPRS and UMTS. GPRS and UMTS intend to
`support an ‘always on, always connected’ functionality, a distinguishing property of packet-based
`services and as such require new and innovative charging mechanisms.
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`Charging Requirements for UMTS Packet -Switched Data Services
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`In order to ease the understanding of the need for new innovative charging mechanisms required for
`GPRS/UMTS packet-based services, I have dedicated a section in each chapter to the Network and
`Service Element layer (NSE). This section describes the network architecture and the functions of
`major network nodes and how these inter-operate to enable the provision of IP-based services and also
`the production of CDRs and IPDRs (Internet Protocol Detail Records) for billing purposes. For
`example, routers (SGSN and GGSN), access devices (User Equipment – UE), and transmission
`facilities together provide basic connectivity; e-mail, and file servers provide application services;
`gateways provide a translation service from circuit to packet voice and so on. Also, the systems that
`configure and manage these devices like the RSVP policy server, bandwidth management system,
`H.323 gatekeeper, RADIUS authentication server etc. are part of the NSE. A section of chapter 4 has
`also been dedicated to mediation, which sits between the Network Elements/infrastructure and the
`Business Support System /Operating Support System (BSS/OSS). The goal of the mediation system is
`to capture all usage information required by the BSS systems, thus providing a single interface to the
`OSS/BSS. The mediation system must in some way determine the devices at the NSE layer and
`interface with that element to extract the relevant usage information. The BSS consists of the systems
`deployed by the service provider to support business operations. These include Billing System,
`Customer Care/Relationship Management, Fraud Detection, Market Analysis etc. Only the Billing
`System
`has
`been
`considered
`in
`this
`report.
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`GSM
`
`1 GSM
`
`Chapter 1
`
`This section gives a brief summary of the history of GSM, how and where it developed and who was
`responsible for its development. It also includes an overview of general cellular concepts and goes on
`to describe some of the features and services supported by the GSM network infrastructure. Then, an
`introduction to the GSM infrastructure and a description of the separate but dependent network
`subsystems and individual components is given before moving on to address the charging scheme
`employed within GSM. Finally, the fastest growing GSM account type, particularly among the younger
`GSM user base, - the prepaid service and the charging mechanism involved is briefly discussed. The
`subsequent chapters describe other digital mobile technologies to be employed in the future including
`GPRS and UMTS. GPRS opens up the mobile market to a wealth of data applications, with over 1
`billion people forecast to be accessing the Internet by 2004 – over half of these via wireless devices.
`
`1.1 History
`
`The need for people and businesses to be accessible at all times and outside the offices prompted the
`idea of manufacturing mobile telephones, which use radio waves as the communication medium. The
`idea was to provide the user with those facilities normally attributed to ‘wire-line’ networks, i.e. place
`and receive calls to/from other users connected either to fixed or mobile networks. Several cellular
`systems have existed, the very first ones using analogue technology. Some of these systems include
`TACS adopted in the U.K, AMPS in the U.S.A, NAMTS in Japan, NMT in the Scandinavian countries
`and Network C in Germany. Below is a brief history of GSM, the world’s fastest growing and most
`dynamic digital cellular technology.
`
`In 1982, Conference of European Posts and Telecommunications (CEPT) formed a new technical
`committee called the Groupe Special Mobile (GSM), whose task was to specify a new mobile
`communication system for Europe - The Second-Generation System. The system was given an English
`title, the Global System for Mobile Communication, thereby retaining the GSM logo.
`
`In the mid 1980s, it was planned that GSM, a digital communications system would be launched in
`1991 and that all major cities would be covered by 1993 and major trunk routes by 1995. Due to
`concerns about meeting this deadline, the introduction of GSM was phased. Phase 1 introduced the
`basic services in 1991 and other services were delayed until the later release of phase 2.
`
`In 1988, the European Telecommunications Standards Institute, (ETSI) was created and given the
`overall responsibility for GSM. Unlike CEPT, made up solely of Administrations, ETSI comprised of
`Network operators, Network manufacturers/vendors, administrations, user organisations etc.
`
`Another important body is the Memorandum of Understanding (MoU) who are concerned with global
`rather than technical issues such as international roaming, charging strategies, service requirements,
`security aspects, compatibility of numbering and routing plans, time scales for deployment of systems,
`etc. An extensive and detailed description of the system known as the GSM Technical Specification TS
`was produced to facilitate the production of system hardware and software. The TS was divided into 12
`aspects including Service Aspects, Network Aspects, Physical Layer in the Radio Path, Audio Aspects
`etc.
`
`As previously mentioned, GSM introduction was phased with phase 1 specifications defining the
`following “basic” Services – Telephony, Emergency calls, Short Message Service, and Bearer services
`300bps – 9.6kbps. Its Supplementary Services included, Call forwarding and Call Barring. Group 3
`Facsimile, Half-Rate CODEC, and other Supplementary Services were proposed for Phase 2
`
`GSM was officially launched on 1 July 1991 as planned but the services were not available until the
`following Spring due to unavailability of the mobile phones. They existed but had not completed the
`formal acceptance procedure. A new approval procedure known as Interim Type Approval (ITA) was
`employed and hence the first operational