2008 Whitepaper Migrations to Ngn-ims

8/2/2019 2008 Whitepaper Migrations to Ngn-ims

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C O N N E C T I N G B U S I N E S S & T E C H N O L O G Y

Devoteam

Devoteam Knowledge CommunitiesOctober 2008

Mi rations to NGN/IMS

Devoteam white paper


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Migrations to NGN/IMS white paper

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MIGRATION TO NGN/IMSDEVOTEAM WHITE PAPER

OCTOBER 2008


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Table of contents

Table of contents...............................................................................................................................................................3List of figures.....................................................................................................................................................................51. Introduction ..........................................................................................................................................................61.1. Purpose of the document....................................................................................................................................61.2. How to read this White Paper .............................................................................................................................61.3. About Devoteam...................................................................................................................................................71.4. About the authors ................................................................................................................................................72. Driving forces in the Telecoms industry in Europe........................................................................................102.1. Markets insights and trends .............................................................................................................................112.1.1. A gradually eroding European fixed revenue .......................................................................................................112.1.2. Near saturation on mobile markets has spurred competition ..............................................................................122.2. Future of technology and usages in the Telecoms industry.........................................................................13 2.2.1. Changing end-user expectations, behaviours and usage patterns......................................................................132.2.2. Advanced technological tools, telecom and media convergence........................................................................132.2.3. Transformation of Telco players positioning and business models......................................................................142.2.4. Globalisation transitions.......................................................................................................................................143. Regulatory intervention in NGN .......................................................................................................................153.1. A market view on regulatory approach............................................................................................................153.2. Acting on control points....................................................................................................................................153.3. Possible regulatory implications of the technical differences between circuit switching and IP.............173.4. Evolutions of charging models ........................................................................................................................203.4.1. Charging principles ..............................................................................................................................................203.4.2. Charging options for IP-interconnection ..............................................................................................................21

4. Regulatory evolutions in Europe .....................................................................................................................224.1. A short history of EU regulation in telecommunications ..............................................................................224.2. Current regulatory framework ..........................................................................................................................234.3. Current rules.......................................................................................................................................................244.4. Regulatory evolutions proposed by the EU ....................................................................................................255. Trends in architectures and migration strategies ..........................................................................................295.1. Reminder of PLMN migration milestones .......................................................................................................295.2. Trends in architectures .....................................................................................................................................325.3. Trends in session control protocols................................................................................................................346. Core network migrations...................................................................................................................................376.1. Overall strategies...............................................................................................................................................376.2. MSC-Server evolutions towards NGN interconnections................................................................................417. Service migration...............................................................................................................................................44

7.1. Legacy services continuity with IM-SSF .........................................................................................................447.1.1. Migration of PSTN/ISDN/Mobile Supplementary Services ..................................................................................457.1.2. Migration of IN services using OSA/Parlay..........................................................................................................487.1.3. Interactions between Legacy Services and OSA/SIP applications......................................................................497.1.4. IM-SCF: Smooth migration towards SIP applications..........................................................................................527.2. Mobility and voice call continuity.....................................................................................................................527.3. IMS service example: the emergency call service..........................................................................................557.4. Service enablers: the presence server use case............................................................................................577.4.1. Background and concepts ...................................................................................................................................577.4.2. PIDF/RPID protocols............................................................................................................................................597.4.3. XCAP protocol......................................................................................................................................................607.4.4. Example of service improvement with presence: call filtering .............................................................................617.4.5. Migration for legacy user to the IMS service........................................................................................................62


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7.4.6. References...........................................................................................................................................................63

8. Fixed-Mobile Convergence and access migrations .......................................................................................648.1. Overview of Fixed-Mobile Convergence technologies ..................................................................................648.2. A FMC experience: BT Fusion ..........................................................................................................................678.3. Access migration procedures ..........................................................................................................................678.3.1. Architecture & Design ..........................................................................................................................................698.3.2. Migration Preparation...........................................................................................................................................708.3.3. Lab Verification of Migration Strategy ..................................................................................................................718.3.4. Pilot site migration................................................................................................................................................718.3.5. Migration procedure (D Day)................................................................................................................................728.3.6. Post migration ......................................................................................................................................................739. Messaging, transport and service access migrations ...................................................................................749.1. Messaging evolutions .......................................................................................................................................749.1.1. Sending messages...............................................................................................................................................74

9.1.2. Receiving messages............................................................................................................................................749.1.3. Legacy mobile messaging interworking (SMS & MMS).......................................................................................759.1.4. Specific SIP based messaging.............................................................................................................................769.2. Signalling transport ...........................................................................................................................................789.3. Access to Legacy services from NGN network ..............................................................................................809.3.1. Optimized routing with non migrated MNP database ..........................................................................................819.3.2. Further applications of the SIP INAP interworking ........................................................................................839.4. Access to NGN services from legacy network ...............................................................................................849.4.1. Optimized routing with migrated NP database.....................................................................................................849.4.2. Access to Diameter based NGN online charging system....................................................................................8610. An operator migration use case: BT21C's network transformation.............................................................8810.1. BT21C network goals.........................................................................................................................................8810.2. BT21C network evolution in UK .......................................................................................................................88

10.3. BT21C architecture ............................................................................................................................................8910.4. Network migration strategy ..............................................................................................................................9110.5. Customer Premises Equipment compatibility testing strategy ....................................................................9111. IMS simulation and test tools developed by Devoteam.................................................................................9211.1. IMSLoader...........................................................................................................................................................9211.2. SITT tool..............................................................................................................................................................9411.3. Conclusion (comparison IMSLoader / SITT tools)..........................................................................................97


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List of figures

Figure 1 PLMN migration from GSM to GPRS 30Figure 2 PLMN migration from GPRS to UMTS Release 99 / Release 4 31Figure 3 PLMN migration from UMTS Release 4 to UMTS Releases 5/6 32Figure 4 Core Network architecture evolution timeline 33Figure 5 Session Control Evolution (interconnection) 34Figure 6 - Migration to NGN (first step of a 2-stage evolution strategy) 38Figure 7 - Integration of IMS after NGN migration (second step of a 2-stage evolution strategy) 39Figure 8 Interconnection between MSC-C and SIP TPO 42Figure 9 Interconnection between MSC-C and SIP-I TPO 43Figure 10 Interconnection between MSC-C and SIP-I TPO in BCS architecture 43Figure 11 IM-SSF role in the network 44Figure 12 Network elements impacted by service migration 45Figure 13 AGCF role in the network 46Figure 14 - Smooth evolution to IN 48Figure 15 - Fixed-Mobile convergent services in OSA architecture 49Figure 16 Service components in IMS Architecture 50Figure 17 - SCIM integration in the network 50Figure 18 - SCIM as Single Point of Orchestration in IMS architecture 51Figure 19 SDP usage in both 2G and IMS architecture 52Figure 20 - VCC: Routing MT call from CS to IM CN 54Figure 21 Voice Call Continuity scenarios 55Figure 22 - General Architecture for Emergency Call 56

Figure 23 - Emergency call setup 56Figure 24 Presence server concepts 58Figure 25 Enhanced call filtering with presence awareness 62Figure 26 Legacy user migration to IMS presence service 63Figure 27 Universal Mobile Access architecture 65Figure 28 Devoteam OnePhone FMC solution 66Figure 29 - Access migration concept 68Figure 30 - Example of migration methodology phases 69Figure 31 - SGW usage 78Figure 32 - SS7 / SIGTRAN Protocol Family 79Figure 33 - SIGTRAN protocol usage in Voip environment 79Figure 34 IMS PSTN interworking without early NP access 81Figure 35 - IMS PSTN interworking with early NP access via originating S-CSCF trigger point 82

Figure 36 - IMS

PSTN interworking with early NP access via ENUM (DNS) 83Figure 37 - Legacy 0800 service accessed from IMS 84Figure 38 - PSTN IMS interworking without early ENUM access 85Figure 39 - PSTN IMS interworking with early ENUM access 86Figure 40 - Camel Diameter IW for online charging 87Figure 41 - BT's UK network before 21CN 89Figure 42 - BT's 21CN domains 90Figure 43 - BT's 21CN protocols used between domains 90Figure 44 - IMSLoader architecture 93Figure 45 - SITT architecture 94Figure 46 - SITT GUI 96


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1. Introduction

1.1. Purpose of the document

The migration to next generation networks will be a change with many challenges. The existing blue print scenarios will

never cover all the expected migration environments. There are many combinations possible between legacy networks

and all-IP networks. Also, the motivations and functionality requirements often differ in every project. Devoteam has build

up experience in many migration scenarios and is able to help customers from the initial phase with requirements,

concepts and solution selection towards realization and validation afterwards.

Within this white paper, the landscape in which migration scenarios will take place is described. Also the involved

technology and standardization is explained more in detail. The detailed information on migration paths and test strategies

show the competence and value Devoteam can offer to customers. With several study cases, the hands-on experience is

explained in more detail.

1.2. How to read this White Paper

The document's ambition is to lead a reader who has knowledge of the existing circuit-switched telephony networks

through their migration to NGN and IMS-based architectures. As such, its scope is very wide and ambitious, as it attempts

to describe the various challenges the industry has to overcome with overall the circuit packet paradigm shift, ranging

from the technological issues to evolutions in business models and including regulatory changes.

The first sections (2, 3, and 4) describe the overall landscape evolutions caused by the circuit packet paradigm shift in

the telecoms industry from a business and regulatory perspective.

Section 5 presents the general trends in telecommunications architectures and protocols.

Sections 6 to 10 cover the migration strategies in various domains (core, access, services, messaging, transport, service

access between legacy and NGN networks), a detailed migration procedure (access migration), and an operator use case.

Section 11 describes some of the test tools developed within Devoteam group to test NGN / IMS networks.


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1.3. About Devoteam

13 years after its creation in 1995, Devoteam Group has become the number one consultancy and engineering company

in information technologies in Europe, specializing in information system infrastructures. Combining consulting and

technology solutions offers enables Devoteam to provide its customers with independent advice and effective solutions

that meet their strategic objectives (IT performance and optimization) in complementary areas: networks, systems

infrastructure, security and e-business applications.

Devoteam achieved a turnover of 370 million in 2007, up 39% over the period, with a 29.2 million operational margin,

up 40%, amounting to 8.3% of turnover. The group counts 4,000 employees through over 20 countries in Europe, Middle

East and Africa. Listed on the Euronext Eurolist B compartment since October 1999, it is part of the NextEconomy, CAC

SMALL 90, IT CAC 50, SBF 250 indexes of Euronext Paris.

In 2008, following the acquisition of the international divisions of auSystems formerly owned by Teleca, Devoteams

telecom business unit counts 500 consultants in France alone, and over 1000 in Europe. Telecoms now represent 33% of

the groups activity.

1.4. About the authors

Devoteam provides an efficient global knowledge management environment (knowledge communities, forums, document

databases, workgroup collaboration tools, continuous education including e-learning courses, etc), allowing consultants

to share their experience.

The NGN/IMS work group was formed on an international basis by the Telecom, Networks & Media Knowledge

Community and globally coordinated by the community leader, Franois Mouillaud. Its purpose was to leverage the

experience of Devoteams telecom community into a state-of-the-art study that can address the operators' issues related

to NGN migrations.


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Franois Mouillaud ([email protected]) has 18 years experience in the telecom industry and joined

Devoteam Solutions in 2000. His assignments in the telecom services area include Sigtran M3UA introduction in a service

platform providers portfolio, support of SMS services in production and introduction of the Color Ring Back Tone IN

service for a mobile operator, specification of a major evolution of the pre-paid IN service and MVNO offer for a leading

manufacturer, validation of Push To Talk services in IMS environment, and specification of Full IP interconnection

architectures between operators. An active member of the Telecom Knowledge Community, he created and contributed to

several Devoteam University courses and is currently the Community Leader. Since 2006, he is based in Lannion, a

Brittany-based Telecom BU division that bears telecom integration and development offers for operators and equipment

providers. He was recently on assignment studying Full IP architecture evolutions for a global operator.

Patrice Crutel ([email protected]) has 22 years experience in the Telecom industry and joined Devoteam

Solutions in 2007. He has been member on behalf of Ericsson of the ETSI group responsible of the INAP protocol

specification during 8 years; He was at the same time one of the Product Managers of the SSF Functional Entity within

the Ericsson Switch AXE10, contributing to the creation of the Ericsson INAP CS1+ protocol. He has been then member

of the OSA group in ETSI contributing to the MPCC API. He is responsible within the Business Unit Telecom of Devoteam

of a department of architects and experts in the Core Network and Service Network layer for both 2G and 3G (IMS). He is

one of the creators of the product developed in partnership with Teligent group called Service Interaction Manager and its

evolution towards IM-SSF, IM-SCF and/or SCIM and was recently responsible for all development and integration

activities of IN, OSA/Parlay, Parlay X and SIP applications for both network operators and Application Servers providers.

Frdric Martelli ([email protected])participated to the implementation of the SIEMENS OMA push-to-talk

service platform and studied for French operator many IMS service implementations (telephony, SMS, MMS, Video

Sharing and Instant Messaging) based on the ETSI NGN TIPSAN architecture.

Maarten Verlinden ([email protected]) has 10 years experience in the telecom industry and joined

Devoteam Telecom & Media in 2007. His expertise lies in the core signaling network area, both legacy SS7 and

interworking towards IMS/NGN. Practical experience includes development, system/solution architecture and technical

sales in the area of GSM & Telephony Signalling protocols (SS7 MAP/INAP/TCAP/SCCP/MTP ), STP/SRP/ R4 CMN

(signaling routing), SMS based security, Mobile Number Portability, EIR, SIGTRAN, Online Charging (DIAMETER),

INSIP interworking, SMSSIP /SMPP interworking.

Dirk Raeymaekers ([email protected]) has 20 years experience in the telecom industry and joined

Devoteam Telecom & Media in 2007. His expertise lie in the areas of GSM & Telephony networks and architecture, GSM

protocols and routing, GSM rating & billing, Mobile Data access via WAP & WAP GWs, Enabling services with OMA


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Presence and Messaging technologies like SMS /MMS/ Mobile IM (IMPS) / OMA IM in 2G & 3G networks and

interworking between legacy & IP based services.

Tom Van Pelt ([email protected]) has 9 years experience in the telecom industry and joined Devoteam

Telecom & Media in 2007. His area of expertise lie in the voice services on access devices, Cellular Data access control

and session handling, Messaging technologies like SMS, MMS and OMA IMPS (Wireless Village), OMA IMS enabling

services like Presence and Group Management and IMS applications like PoC, OMA SIMPLE IM, GSMA Video Share and

Image Share. He has also had a strong focus on the interworking between messaging services using different

technologies and on the packaging of several services in an integrated offering.

Ludovic Bourdin ([email protected]) has been working for 4 years in the field of value-added services

(Voice mail, SMS, MMS, chat) in various levels: tendering management on IN services, technical project management

on a prepaid billing platform and lately marketing studies (benchmark of communication suites and Content business

analysis) for mobile operators..

Sylvain Weyl ([email protected]) has 20 years experience in the telecom industry. He has worked

successively for TRT/Philips, Lucent Technologies, Siemens, and joined Devoteam Solutions in 2005. His telecom

expertise lies in the areas of equipments for transmission and telecom network management as well as in telephony &

GSM/UMTS architectures and NGN/IMS evolutions.

Thierry Hardy ([email protected]) has 10 years experience in telecom industry and joined Devoteam

Solutions in 2005. He has built an expertise in GSM, PSTN, intelligent network, and on IMS network and architecture,

especially on services and charging domain.

Damien Boutoille ([email protected]) has 10 years experience in the telecom industry. He worked for

major manufacturers in the ATM, H.323, video over IP, SIP, IMS, including presence service. In parallel he is teaching

VoIP in several French engineering universities ("Grandes coles").


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2. Driving forces in the Telecoms industry in Europe

The telecom & media market has radically evolved during recent years, as far as infrastructure, services and contents are

concerned.

Convergence has linked elderly-dissociated segments like fixed telephony, mobile and broadband and competition has

increased between different players.

This world is likely to go on changing in the next years, driven by the competition dynamics as well as exogenous factors,

which can be gathered in 3 categories:

End user expectations, behaviours and usage patterns

Technological progresses

Globalisation, regulation and public policy

At the end of an investment cycle and at the beginning of a new era, IMS is likely to be presented as the universal

underlying tool for service design and implementation.

Multi

servicesconvergence

Broadcastinggroups

Contentmajors

Webplayers

Telecomactors

Electronicmanufacturers

ITsphere

Networksphere

Multi

servicesconvergence

Broadcastinggroups

Contentmajors

Webplayers

Telecomactors

Electronicmanufacturers

ITsphere

Networksphere


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2.1. Markets insights and trends

Over the past decade, growth of the European telecom services market has gradually eroded from 2-digit growth rate at

the end of the 90s, to 3% estimated in 2006. It is due to the conjunction of two main factors:

The decrease of fixed voice revenues (still 1/3 of the total telecom service revenues), which have fallen by an

average 2% per year since 2001, whereas the wireline data services (including Internet Access) dont compensate

the decline of fixed voice.

A slower growth rate in the mobile sector (2/3 of the total telecom service revenues), coming from a near

saturation of the market and a reduction of ARPU.

2.1.1. A gradually eroding European fixed revenue

Within Europe-top5 (France, UK, Spain, Italy, and Germany), the fixed voice market has declined 5.9% in value between

2001 and 2005, resulting from:

Pricing pressure, due to the arrival of alternative operators since the early 2000s. The lower usage costs were not

compensated by the rise in subscription costs.

Access line losses, through a dial-up to broadband migration and an increased number of households having only a

mobile phone access.

Fixed line usage decline. This decline was exclusively driven by the decline in dial-up Internet usage while fixed

telephony usage has been fairly stable.

This strong attrition of the fixed voice market is unfortunately not compensated by the strong growth in broadband.

Between 2001 and 2005, Internet revenues in EU-25 more than doubled, 95% of which generated in EU-15

markets. The expansion of the broadband subscriber base has fuelled the increase in revenues. Its impact on revenues

has been partly limited by the parallel decrease in dial-up Internet revenues (subscriptions and communications). The fall

in tariffs, through enriched bundles, price reductions and promotions, has indeed permitted to create a mass-market.

Along with customer base expansion, the broadband market has seen a swift development in service availability and

quality. In many Western European countries, DSL is already available to over 90% of households

Incumbents' market share on broadband has steadily declined in recent years, with less than 1 subscriber out of 2 (in

retail). Broadband accesses are shared between DSL and cable:


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The DSL still counts for 80% of the whole broadband access. Broadband access through wholesale or unbundled

lines are growing at a fast pace.

The situation on cable depends widely on the country. Some cable operators are unable to provide a competing

broadband offer (due to infrastructure upgrade costs) while other already reach a high market share. The

consolidation on this market is likely to reinforce the role of cable in the future.

2.1.2. Near saturation on mobile markets has spurred competition

With an equipment rate in Western Europe now averaging 100%, competition between operators to acquire and retain

customers has increased. Generally, new 3G operators havent dramatically changed the landscape. MVNOs have

grabbed a noticeable share too (12% in 2007), but only on the mobile market due to them being unable to sign

commercial agreements with network operators. At last, the mobile number portability has had a major impact on

competition, when the duration and complexity of the procedure wasnt prohibitive.

With a mobile penetration now close to 100% (and even above in

western E-U countries), the customer base wont grow much more.

Operator will soon have to rely on usage and tariffs trends to increase

their profits. But even so usage continues to increase at a good pace

(+5% per year between 2001 and 2005), operators competition and

reinforced regulation have made prices drop. As a result, the ARPU,

after peaking in 2004, is slowly decreasing.

Indicators 2006 2012

Act ive mobile subscribers penetra tion 101,6% 120,1%

ARPU voice communications 24,4 22,6

Share of ARPU voice communications 80,7% 67,6%ARPU data 5,8 10,8

Share of ARPU data 19,3% 32,4%Total ARPU 30,3 33,4

Source: Analysys

Estimation of mobile ARPU in Western Europe

As a potential source of increased profit, the launch of 3G services hasnt come up with the operators expectations.

Despite significant progress, the 3G market is growing slowly, and the base of 3G customers barely reaches 11% in

Europe (mid 2008). In the next years, the competition is expected to take place more on the data market than on the voice

market.


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2.2. Future of technology and usages in the Telecoms industry

This section briefly goes through the multiple forces that will shape the future of the market.

2.2.1. Changing end-user expectations, behaviours and usage patterns

Telco operators will have to adapt their offer to meet the needs of different kinds of users. On one hand, younger people,

more tech savvy, have a wide appetite for innovation but arent loyal to a definite brand and easily switch from a service to

another. They dont like the all-in-one packages for communicating and prefer a do-it-yourself approach, mixing different

(cheap) services that best suit their changing lifestyle. On another hand, the ageing population, afraid by tech-complexity,is more interested in plug-and-play products, even at higher price.

Communication is becoming more and more personal. Where some years ago the

household communication was exclusively bound to the fix phone, it relies today on personal

devices (mobile phones) or accounts (Internet). Users now make personal choices about

their own consumption, expecting the best possible personalized services. Thus, Telco will

need to adjust their model to potentially address hundreds of niches.

With more and more time spent away from home or from office, nomadism and hyper

mobility will become the new norm. Telecommunication will have to adapt and develop as much as possible the mobilitymarket, allowing clients to call, browse, watch TV and keep in touch with their community at every moment.

2.2.2. Advanced technological tools, telecom and media convergence

Progresses in processing and storage capacity, as well as miniaturization, pave the way for a proliferation of connected

edge devices. Emerging technologies like nanotechnologies and energy management shall play a major role in

tomorrows communication services.The IP protocol, originally confined to the Internet world, is now spreading over all

communication technologies and is becoming the new norm. IP-based networks offer an opportunity to carry numerousand different services over a single network, sharing the same bandwidth. This implies that the cost of distribution of a

service or an application can be mutualised and therefore significantly reduced.

In addition, network and wireless technologies are becoming more efficient, allowing an ever increasing bandwidth, thus

accelerating the rise of new technologies and services. The development of optical multiplexing is even expected to boost

this bandwidth to very high values. Telco operators next challenge is to get ready to monetize abundance (rather than

price capacity scarcity), with further massive price drops.


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With digitalization of contents, a new era of media consumption has arrived. It is the end of the one device, one

application paradigm, with customer able to read a content on different devices and able to read several contents on the

same device (e.g. mobile phone). The digital information marginal costs are almost nil, and technology progresses allow a

reduction of the application/service production costs.

Concerning the TV, new technologies have made it possible to broadcast high-def TV (larger and better picture and better

sound), with large impacts on the telecom/internet/media area: development of pay-TV, replacement of home equipment

and a growing need in bandwidth. TV on mobile is slowly emerging and is going to be a major market in the short to

medium term.

2.2.3. Transformation of Telco players positioning and business models

Technology, regulatory and globalisation disruptions are weighing on carriers' traditional revenue model based on

distance and/or duration pricing of a scarce resource (network capacity). These pressures and the severe pricing

dynamics observed call for an evolution of carriers' revenue model along multiple possible dimensions:

New pricing schemes for existing services: transition to fixed or flat rate (e.g. for VoIP), additional services for free

More value for money.

Larger service and content offering with new end-user services, even outside the telecom business (e.g. m-payment).

Expanded wholesale strategies to rely on 3rd parties to resell (e.g. unbundlers)

or use (e.g. application providers) enriched connectivity.

Developing new funding mechanisms for services. Advertising has attracted

the attention of almost every player from the extended Telco world. Online

advertising is on the rise: from 9% in 2006, its share in the European

advertising market is expected to reach 18% in 2012. Meanwhile, the global

amount of advertisement expenses should double from 7.5 billion dollar in 2006 to 16 billion dollars in 2012.

2.2.4. Globalisation transitions

In the coming years, the reshuffle in regional balances will produce new industrial giants both in telecom services and

equipment (the prominence of Chinese equipment vendors already being a reality). For the moment, mobile carriers in

emerging countries rather address their domestic market (where they find plenty of growth opportunities), but they could

soon address the Western markets where the average ARPU is much higher. These globalisation transitions will influence

future technology standards, as industrial giants eager to push a home-made technology may weight a lot on the

international normalisation process.


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3. Regulatory intervention in NGN

3.1. A market view on regulatory approach

The rationale for regulatory intervention during the transition from monopoly to competition ensures a level playing field for

all market participants by regulating the main control points passed forward from the monopoly era residual market

power and network bottlenecks. Learning from these experiences, regulators may view their job in the NGN marketplace

as something similar: identifying control points and applying the appropriate regulation. They have to distinguishing

between potential control points that promote normal competitive activity, and those that may harm competitive activity,

and must be cautious when putting in place ex-ante measures, ex post tools being seen by a large part of the industry as

sufficient in a mature market.

Ex ante tools include regulations put in place in anticipation of a problem, such as those to ensure cost-based, non-

discriminatory access to the incumbents bottleneck facilities by competitors, and the blocking of alliances seen as anti-

competitive. Ex ante tools could be interesting in an NGN environment as competition law has proven to be too slow.

Ex post tools are mainly antitrust remedies under competition law applied after an abuse of market power is alleged or

demonstrated. Regulators should be careful of not regulating too early and the long-term risk and reward aspect must be

taken into account. Players should be allowed a certain level of freedom when building services and gaining market. In a

mature market, competition law (ex post) is seen by many as sufficient although it is recognized that operators need to be

careful in such an environment. Ex post tools could represent a financial risk to players in a fast moving market like NGN

where a significant part of an operators revenue could be put at risk if a dominant or abusive position is alleged or proved.

3.2. Acting on control points

The NGN environment includes a wide range of facilities that in theory could have open interfaces and/or could be

provided competitively. Each could be seen as candidates for being considered as relevant markets, but most would

normally be subject to competitive pressures without a need for regulatory intervention.

Only where there are significant bottlenecks or control points that threaten to block the development of the market can ex

ante regulation be justified as a means to achieve fair competition. The real challenge posed by NGN is to understand

where these can appear in an environment that will be quite different from the PSTN and mobile environments, which are

familiar to regulators. They could well be related not to the transmission layer but to some other aspects of service


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creation. The potential control point need not be owned by the operator, and could equally well be a critical software

platform controlled by a software vendor.

There is no consensus in the market that such control points will emerge with NGN, nor a common understanding of what

the potentially harmful control points would be. It would be important for regulators to understand where to look for those

control points that can become sustainable and/or irreversible sources of dominance and which would lead to market

failure unless addressed by ex ante regulations. Such control points would involve ownership of elements necessary to

provide certain services and that could not easily be replicated. The local loop is a classic example of such an element.

In an IP setting, there could be other elements equally critical for the provision of a certain set of services. They would

probably be strongly related to individual customers. Control points could also take the form of market power that would

enable an operator to impose bundling and/or interoperability limitations reducing customer choice and competitive

alternatives.

Below are a number of examples of functions that are expected to play important parts of the NGN environment and

which therefore could provide basis for control points.

Network capabilities. What can be done with the infrastructure and how can dominant operators limit infrastructure

capabilities for competition?

Elementary Services and NGN capabilities. What services can be built and how can a dominant operator restrain

competitive servicealternatives? Accessing services and content. What services can a user access and how can operators and service providers limit

hischoice?

User information. What can providers know about a user which facilitates service provision?

If dominance over a given control point is achieved, a next step for the regulator is to consider whether some type of ex

ante action is necessary. Under the new regulatory framework, such action can only be contemplated after having

followed the procedure for definition of a new relevant market. The European Commission plays a strong role in this

process through its recommendations on relevant markets, as well as its power to veto markets defined at the national

level.

Leaving the procedural issues aside, the assessment of whether to introduce an ex ante regulatory requirement can be

extremely difficult because of the complexity of the NGN environment and because the consequences of regulatory action

cannot be entirely foreseen. This is the basic challenge for regulators in the NGN environment where there are risks

associated with any course of regulatory action or indeed inaction.

There are several good reasons why regulators should be reluctant to step in:


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which are accessible through normal IP addressing. There are more opportunities for open interfaces in

IP networks. This provides a potential for wider participation and more competition in advanced

communications services.

- Interoperability and open interfaces will become important issues as there will be many more forms of

interconnection and access than in the CS environment. There is a potential for more geographic

independence as a server can be located anywhere in the global IP network, whereas in the SS7 network

only interconnected operators can have access.

Network centric service creation vs. network independent service creation

- The creation of network services in a CS network is largely under the control of operators of the CS

network. In an IP environment services can be created by integrating service components from various

independent service providers distributed across networks and geography independently of the

underlying network infrastructure

- Physical presence can no longer be used to determine where a service is located in terms of networks

and geography.

- It may be difficult to determine the country in which a service originates and thus to identify the applicable

national law.

- Regulators have to assess whether open interfaces to service components are necessary or if

interoperability can be implemented through gateways that perform conversion between interfaces.

Switching vs. routing

- Basic components of a CS network are the switches that perform service and management related

functions, in addition to establishing the transmission path from caller to receiver.

- The basic components in the IP environment are routers, which forward packets toward their destination,

and servers which perform service functions. Servers can be addressable units in the network and

communicate using the same protocols as user terminal equipment.

- There is a potential for clearer separation between the transmission / control layers and the service

creation layer, as functions in these layers are carried out by different equipment types.

- In open IP networks, there is the potential for more geographic independence between the user location

and service creation. This could lead to more international competition for communications services, for

example, through sophisticated forms for call-back services capable of dynamic optimization based on

real-time tariffs and currency rates.


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Clear vs. blurred boundaries

- In CS networks, there is a distinction between the network and the user equipment attached to it.

Functions carried out in user equipment are normally not covered by telecommunications regulations

beyond technical compliance requirements. CS networks provide a clear boundary between network and

user terminal equipment, and intelligence is mainly centralized.

- The boundary between network and terminal equipment is less clear in the IP environment, and

intelligence is distributed between end-points and control devices within or at the edge of the network.

New criteria may be required for determining whether a given function belongs to the network, and

therefore may or may not be covered by its regulations.

Connection-oriented vs. connection-less

- CS is connection oriented, meaning that a signaling phase takes place before the communication starts in

order to trigger preparatory actions at the receiver end as well as along the transmission path. Signaling

can also occur during the communication to adjust parameters, and occurs at the end of the

communication to release resources.

- In the lower layers, IP operates in a connection-less manner meaning that packets are sent out and

received without any prior warning or preparation.

- Connection-less communications don't have clearly defined start or end times. One consequence is that

time-based tariffs become unsuitable where cost orientation is a regulatory requirement.

Dedicated circuits vs. different routes

- CS is based on the set-up of a dedicated circuit for the duration of a call, while IP will transmit packets

using several different routes and infrastructure for a single communication

- In CS, time can be related directly to network usage while in IP networks this is not possible. Time based

tariffs become unsuitable where cost orientation is a regulatory requirement.

Numbering vs. names and addresses

- The CS numbering system is based on ITU Recommendation E.164 numbers. The numbering system is

controlled jointly by ITU and national authorities.

- The IP addressing system is based on IPv4 or IPv6 addresses in combination with domain names. It is

controlled by ICANN, which is a non-governmental international organization.

- With the transition to IP, control over numbering resources is being transferred from governmental to non-

governmental organizations.


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3.4. Evolutions of charging models

3.4.1. Charging principles

Charging principles can be based on different measurements:

Element Based Charging (EBC): the interconnection rates depend on the number of network elements as well as

distance.

Capacity Based Charging (CBC): the central feature distinguishing CBC from EBC is that, under CBC, system

bandwidth is bought in advance by competitors. This leads to a more adequate risk sharing between incumbent and

competitors

Distance Independent Charging

Charges based on grades of service

Charging principles in telephony networks or IP networks can be seen from two levels, retail and wholesale.

At the retail level, there are generally two methods of payment:

Calling Party Pays (CPP): the calling party pays for the call.

Receiving Party Pays (RPP): the calling party and the called party share the cost of the call.

CPP is the most common charging principle for charging voice calls, while RPP is used both for the retail billing in the

Internet and in the mobile market in North America.

At the wholesale level, three billing models exist:

Calling Party Network Pays (CPNP): the network of the sender pays to send.

Bill and Keep (B&K): each network bears the costs of terminating traffic coming from other carriers. There is no

interconnection charge.

Receiving Party Network Pays (RPNP): the network of the receiver pays to receive.

CPNP applies to both the calls in the PSTN and the European mobile sector, while B&K applies to both the Internet traffic

and the mobile sector in the USA.

CPNP might cause termination monopoly (arbitrage problem). B&K, on the other hand, makes operators have an

incentive to hand over their traffic into another network for termination as close as possible to the point of origination ("Hot

potato" problem). It also provides less incentives for operators to monitor inbound traffic for assuring a guaranteed level of

QoS, as no payments are made for carrying this traffic. One feasible solution for the "Hot potato" problem is to require a

minimum number and location of POIs.


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3.4.2. Charging options for IP-interconnection

As charging principles used in the telephony networks are different from those used in the IP networks, charging issues

arise when interconnecting PSTN and IP networks.

While conceiving the charging principle for IP interconnection, two cases should be distinguished: the all-IP world and the

transition phase. Key factors to be considered are:

Termination monopoly at the wholesale level

Familiarity of end-users with CPP and RPP

Relationship between wholesale and retail pricing

Compatibility with retail tariff schemes

Network and usage externalities

In the all-IP world, three variants of dual regime using different principles in accordance with the type of networks, the

services or the network levels have been conceived:

Different regimes for different types of networks: B&K for the IP network and EBC/CBC for the PSTN.

Different regimes for different services: differentiation according to services or QoS classes.

Different regimes for different network levels: B&K on the access/backhaul level (between customer and POI), and

EBC/CBC for transit in the core network.

The first type of dual regime is not viable in the long run, as VoIP calls give rise to arbitrage opportunity. The second type

requires clear distinction between different services and that the usage of services be measurable. The third one helps

minimizing the "hot potato" problem. For this type, determining the number of POIs at the access/backhaul level is crucial.

The options for managing the transition phase towards all-IP infrastructures are considered in two conditions:

When "Pure" B&K is the long-run target regime, options to soften the transition process include the following (either

way, it is preferable to keep the period where PSTN and IP networks run in parallel as short as possible):

o IP-based networks simply substitute for the PSTN, preferable if the transition to all-IP networks comes

quickly.

o The interconnection regime is adapted to B&K for the PSTN.

When EBC/CBC is the long-run target regime:

o Elements of these regimes are present in transit agreements.

o The assurance of QoS might increase the willingness to pay for network usage.


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4. Regulatory evolutions in Europe

4.1. A short history of EU regulation in telecommunications

Over the past two decades the European telecommunications sector has moved from a tradition of strong public service

monopolies, often twinned with national postal services, to one of increasing privatisation and competition. EU policy has

evolved with the sector supporting common development, promoting competition and harmonisation.

Since 1987 a policy phase saw liberalisation as the main focus and culminated with the liberalisation of all

telecommunications services and networks by 1 January 1998. The 1998 framework was reviewed in 2002, when growing

convergence between telecoms, broadcasting and information technology meant the rules had to be adapted. Today, with

the EUs emphasis on Growth, Competitiveness and Employment telecommunications policy is at the heart of Union

policy. The revision launched in 2007 seeks to bring the framework up to date for the fast-developing telecoms sector in a

Union which now has 27 Member States.

The regulatory process for telecommunications reflects the wider process of economic integration in Europe. The main

policy theme has been the move towards a single market for telecommunications services and equipment that

progressively removes barriers to pan-European operation and supply. This policy has seen an evolving interaction

between four elements: liberalization, harmonization, competition and public service.

Three instruments have been used to liberalise the sector in Europe: progressive liberalisation of former monopolies,

accompanying harmonization measures, and competition rules

The main mechanisms to promote liberalization were directives which abolished the special rights of certain public

enterprises to produce or supply telecommunications equipment or services, which then breached competition and

internal market rules. These Directives required Member States to allow competition in the market for telecommunication

services, but did not require the privatization of national public services.

To complement the liberalization directives, a series of harmonizing measures were also adopted. The 1990 Framework

Directive established the principle of Open Network Provision: essentially harmonized open access to public telecoms

networks. This directive was developed in the mid-1990s to adapt to the evolving competitive environment and together

with further Directives on Interconnection and Licensing made up the 1998 package of legislation which established the

basis for the full opening of EU telecoms markets on 1 January 1998. The legislative package was accompanied by

comprehensive guidelines on the application of EC competition law in this new business environment.


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The 1998 package was primarily designed to manage the transition from monopoly to competition. With rapidly changing

technology, convergence and the new challenges of truly liberalized markets a single, coherent framework of regulation

covering all electronic communication, including broadcasting networks, was agreed and applied from 2003. The 2003

policy framework largely replaced the 1998 package catering for a dynamic and potentially unpredictable market involving

more players and a more complex multi-faceted telecommunications market environment.

The review of the 2003 framework launched in November 2007 seeks to build on the gains that consumers have already

realised in the telecoms market. Competition has grown strongly in some cases, less so in others. Prices have fallen in

many sectors, and EU initiatives such as the Roaming Regulation have helped bring them down in others. But the market

is still largely fragmented, with few operators offering services across several Member States. The revised rules will focus

regulation on those market sectors where competition is still lacking, and develop stronger EU-level regulation to foster

the development of the internal market.

Since the last regulatory package was adopted in 2002, new developments in the telecoms sector have left the current

regulatory framework in need of updating. To take account of the changed sectoral landscape, the Commission launched

a review of the current regulatory rules in November 2007. The Commission's proposals for reform have yet to be

discussed and approved by the EU's decisional process.

4.2. Current regulatory framework

The European Unions new framework for regulation of electronic communications services became applicable in July

2003. Its purpose is to encourage competition, to improve the functioning of the internal market and to guarantee public

and user interests in the electronic communications sector.

This regulatory framework consists of one general Directive, Directive 2002/21/EC of the European Parliament and of the

Council of 7 March 2002 on a common regulatory framework for electronic communications networks and services

(Framework Directive) and four specific Directives:

Directive 2002/20/EC: Authorization Directive,

Directive 2002/19/EC: Access Directive,

Directive 2002/22/EC: Universal Service Directive,

Directive 2002/58/EC: Directive on privacy and electronic communications sector.

The Access Directive contains detailed rights and obligations for operators and undertakings seeking interconnection


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and/or access to their networks or associated facilities, and the Universal Service Directive describes the minimum scope

of universal service obligations and rules for its costing and financing. The Framework Directive provides the overall

structure for the new regulatory regime and sets out regulatory principles that NRAs must follow.

European Regulators Group (ERG)

In order to assist the European Commission and facilitate the implementation of the new regulatory framework, new

committees and working groups have been created: the Communications Committee, the Radio Spectrum Committee, the

Radio Spectrum Policy Group and the European Regulators Group (ERG).

The ERG has been set up by Decision 2002/627/EC. It aims to provide suitable mechanisms for encouraging cooperation

and coordination between National Regulatory Authorities (NRAs) and the Commission, in order to promote the

development of the internal market for electronic communications networks and services, and to achieve consistent

application of the Directives of the new regulatory framework in all Member States.

Independent Regulators Group (IRG)

The Independent Regulators Group (IRG) is a group of European NRAs established in 1997. Its objective is to share

experiences and points of views among its members on issues of common interest such as interconnection, prices,

universal service, and other important issues related to regulation and development of the European telecommunications

market. At present, the IRG includes NRAs of 33 countries, including France, Germany, Poland, Spain and the UnitedKingdom.

National Regulatory Authorities (NRAs)

National telecommunications Regulatory Authorities are the national regulatory institutions responsible for issues such as

licenses, price control, dispute resolving. The NRAs shall carry out the regulatory tasks specified by the five Directives.

4.3. Current rules

The EU legal framework for regulating telecoms services has been developed with the aim of developing a better-

functioning internal market for telecommunications networks and services. Last revised in 2002, this framework is

currently being updated, to take account of developments in this fast-moving field. In the Information Society, boundaries

between telephone, internet, television broadcast and mobile phone services are becoming blurred, even irrelevant.

Indeed, frontiers between Member States have also lost much of their significance when it comes to these services. The

regulatory approach to the different services has also to converge. In 2002, the European Union adopted a new regulatory

framework for electronic communications networks and services, covering all forms of fixed and wireless telecoms, data


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transmission and broadcasting. The regulation of the content carried by such services is, however, dealt with under

separate rules.

In the internal market, telecoms operators and service providers have the right to set up and offer their services throughout

the EU. Encouraging and enabling them to take advantage of those rights boosts the overall quality of telecoms services

for consumers, and reduces the prices they have to pay for them. The EUs regulatory framework aims to promote fair

competition, which will boost Europes economy by supporting activities which relies on telecoms, create a strong telecoms

industry in Europe, and make consumers the ultimate beneficiaries.

4.4. Regulatory evolutions proposed by the EU

The current rules which govern the telecoms sector in the EU were agreed in 2002. In this fast-developing sector, the

regulatory framework needs to be revised, to ensure it continues to serve the best interests of consumers and industry in

todays marketplace. The Commissions review proposals, adopted in November 2007, will bring the EUs rules up to date.

In economic terms, the telecoms sector is one of Europes most important, with annual turnover of around 290 billion,

and around 4% of the jobs in the Union. More widely, the prices charged by the telecoms sector represent a direct cost of

doing business in Europe. Liberalisation in the telecoms sector in the EU, launched in the mid 1980s, has brought

significant benefits for consumers. The price of telecoms services have fallen, on average, by around 30% in the past

decade. Moreover, the introduction of competition has raised standards of service all round, making former monopolies

much more respondent to the needs of consumers.

Although EU action has brought major benefits, there is still work to be done to create an effective internal market in

telecoms, which would bring even greater benefits to consumers and businesses alike. Today there are only a few

operators providing pan-European services, and one of the reasons is the different ways in which national regulators have

implemented the EU framework. The internal market is fragmented, with the result that operators have to package their

services in different ways in different Member States, and satisfy different regulatory requirements each time. That

fragmentation is hindering effective cross-border consolidation, and often blocking or delaying the entry of new

competitors to the market.

One aspect of the Commissions proposals is to review the regulatory approach, to ensure that national regulators have

the appropriate tools and powers to ensure fair competition. The successful introduction of the Roaming Regulation in

summer 2007 demonstrates that action at EU level can be effective in securing benefits for consumers. The Commission

is therefore proposing to create an EU-level telecom market body to complement the national regulators.


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The European Telecom Market Authority will build on the existing collaboration between national regulators in the

ERGhttp://www.erg.eu.int/, providing the power to act centrally when required. A new EU-level authority will make it easier

to coordinate action across the internal market. The new authority will also act as a European centre of excellence for

network and information security, helping the Commission to step up the fight against spam, and taking over the tasks of

the European Network and Information Security Agency (ENISA). A Chief Network Security Officer in the new authority will

have responsibility for this important task.

Whilst the reform will tackle some areas where the current rules have still not opened up the market to competition

notably where former incumbents continue to dominate the Commission recognizes that the rules have worked in others.

Therefore, it proposes to remove the requirements for ex anteregulation in major parts of the telecoms sector. In these

markets, ex post regulation will become the norm, i.e. operators will have to seek redress for any problems through

application to the competition authority and/or through the courts.

In the future, therefore, regulatory action will focus on those sectors of the telecoms market where competition has so far

been most restricted. That is not to say that we will allow the achievements in improving services and reducing costs to

consumers in those markets where regulation will become lighter to be reversed. Regulators will still monitor those sectors,

and take action if necessary and the picture will vary from Member State to Member State. By focusing regulatory efforts

and resources on the sectors where it is most needed, the Commission aims to win the greatest benefits for consumers,

in the shortest possible time.

The Commissions proposals for the review of the telecoms framework, adopted on 13 November 2007, are the result of

two years of consultations with stakeholders, with national regulators and with users of telecoms services. They will be

debated in the European Parliament, and by Member State governments in the Council. Once adopted at EU level, the

revised rules have to be incorporated into national law before taking effect. The Commission expects the new framework

to be in place from 2010. The proposals focus on four key areas.

More competition

Competition in the telecoms sector brought more choice to the markets. However, we need more competition for Europe's

telecoms sector to achieve more investment, greater innovation and lower prices. The Commission will maintain ex-ante

regulation in those markets where competition is not yet effective, and keep a close eye on those markets which are

crucial for Europe's competitiveness (such as broadband).

The reform will also give national regulators the possibility to introduce functional separation when necessary. That means

that an operator would have to split up its services division from the division managing the infrastructure, although both

would stay under the same ownership. This will ensure that competing operators have access to infrastructure without

discrimination.


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From country to country there are major differences in how the current rules are implemented. That is why the proposed

new rules give the Commission the power to oversee remedies proposed by national regulators, to help ensure a more

consistent, efficient and speedy application of these across the EU.

Better regulation

At the heart of all Commission action, the better regulation initiative means that regulatory action should only be taken

when justified, and should be proportionate. In the telecoms sector, the Commission proposes to remove ex-ante

regulation from 11 of the 18 markets within the telecoms sector, including both retail (from operators to consumers) and

wholesale (between telecoms operators) markets. In particular, retail regulation is not necessary where there is already

effective wholesale regulation, allowing new entrants to find acceptable terms for access.

In future, regulators will focus their resources on market sectors in which the dominance of incumbents has been least

challenged. In those markets, regulators need to continue their efforts to create conditions in which new entrants can

effectively stimulate competition, improve services and lower costs for consumers.

The Commissions proposals also seek to enable the telecoms sector to make better use of radio spectrum. Management

of radio spectrum will be made more flexible and market oriented, to make sure those industries dependent on spectrum

can reap the maximum economic benefits of this vital and scarce resource. Furthermore, the digital dividend the

valuable part of the spectrum released through the introduction of digital television broadcasting and resultant analogue

switch-off will be available for new uses. To take full advantage of this opportunity, the Commission proposes these

frequencies to be used more flexibly, so that service providers themselves decide on the value to be placed on the

different services that could use it.

Strengthening the internal market

The telecoms sector in Europe today is still largely fragmented on national lines. Few operators are active throughout the

internal market, and even fewer offer pan-European services. Regulatory inconsistency through different interpretations

and applications of EU rules is a major reason why the internal market in telecoms has not developed more strongly.

Operators seek certainty in the regulatory approach throughout the Union, and so the lack of consistency has been a

major barrier to their investment outside their home Member States. National markets are all distinct, and the Commission

underlines the necessity of independent national regulators who each know their own market taking responsibility in

each Member State, but coordination and consistency across the Union needs to be improved.

The ERG created under the current regulatory framework has encouraged national regulators to work together, and with

the Commission, to seek EU-level solutions to common problems. Indeed, the ERG has been central to initiatives such as

reducing the costs of roaming to mobile phone users. But achieving consensus in a body with representatives of 27

Member States is no easy task, and the ERG has no power to implement its agreements across the Union. The


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Commission is therefore proposing to create a European Telecom Market Authority, building on the coordination efforts

already established amongst regulators. National regulators will be at the heart of the new bodys work, but it will have the

power to act across the EU.

Protecting consumers better

The fast developing telecoms market has brought major benefits to consumers, and the EU has already legislated to

ensure all citizens have a basic set of rights, including access to a telephone/internet connection and protection of

personal data, as well as specific rights for people with disabilities to be able to gain access to telecoms services. The

Commission proposes to build on these existing rights, to ensure that consumers benefit from the development of

competition in the telecoms market. In particular, operators will be obliged to publish information on prices so that

consumers can more easily compare the different offers on the market.

Operators will also be obliged to facilitate transfer of customers from one service provider to another, so that they can

effectively take advantage of better prices and conditions. Member States must improve access to telecoms services for

people with a disability, including access to the single European emergency number, 112.

Security and privacy have become critical in the development of the Information Society, and therefore of the telecoms

services which provide its backbone. Consumers are becoming more and more concerned about possible misuse of their

data, including information which could be used to track their movements. In particular, consumers worry about criminal

misuse of their financial information, and so the Commission proposes that telecoms operators must inform customers in

the event that their personal data becomes compromised.

Spam, spyware and related malicious uses of the telecoms system threaten to stunt the growth of the Information Society,

and the proposals would step up EU efforts to combat them, in particular the creation of a Chief Network Security Officer

within the European Telecom Market Authority to work with telecoms regulators to identify and lead the response to all

threats to European telecoms networks.


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5. Trends in architectures and migration strategies

This chapter deals with general migration trends and strategies for various functional entities in the network. More detailed

migration procedures relative to a specific domain such as access, core network, messaging, or services will be

addressed specifically later in the document.

In general, a migration strategy involves a choice between options such as:

An "island" solution involving overlay between a TDM component and an NGN component (each one serving differentpurposes and the NGN one being dedicated to limited load or functionality, for example NGN-specific features such as

new services)

General overlay between a TDM component and an NGN component (each one serving the same purposes, with

load sharing between the two) and gradual migration towards the NGN component following usage adoption

Complete replacement of the TDM component by an NGN component, with possible fallback upon failure

This approach is made complex by the fact that there is generally not a complete functional overlap between "equivalent"

components in the TDM and NGN architectures (the NGN adds new features and may cause the loss of legacy features

which need to be emulated or simulated), and by the interdependency between functional domains (e.g. the core network

and the service architecture).

Nevertheless, the migration is usually dealt with by functional domains. This is the approach retained in this chapter, which

we introduce by a reminder of PLMN migrations between GSM and UMTS architectures.

5.1. Reminder of PLMN migration milestones

From GSM 2G to 2.5G GPRS

The GSM standard has been built with the same focus as the PSTN network: it is a circuit-switched network, primarily

aimed at providing telephony services, with the added functionality of the radio access and of mobility. As in the case of

PSTN networks, data sessions have been made possible, but with the constraints of a circuit-switched network, e.g. poor

utilisation of the bandwidth utilisation from the operator's perspective and low data rates.

GPRS services have been launched from mid-2001 and provide a more efficient way of handling data traffic. As illustrated

in the figure below, the innovation of GPRS is to introduce a packet-switched core network in the mobile operator's

network, enabling the activation of packet-based "always on" data sessions.


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Figure 1 PLMN migration from GSM to GPRS

From 2.5G GPRS to UMTS release 99 and UMTS release 4

In the first release of UMTS, UMTS release 99, the core network principles remain the same: it uses a circuit-switched

core network for voice service and a packet-switched core network for data services. The main change lies in the radio

access part, called UMTS Terrestrial Radio Access Network (UTRAN), enabling higher data rates, as shown in the figure

below. Release 4 offers further services and features such as Virtual Home Environment (VHE) and Open Service

Architecture (OSA). Release 4 also fully supports Location Services.


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Figure 2 PLMN migration from GPRS to UMTS Release 99 / Release 4

From UMTS release 4 to UMTS release 5 and release 6.

UMTS release 5 introduces a major change in the core network: the circuit-switched core network disappears and the

architecture becomes all-IP. Voice calls can be carried on the converged IP network, using SIP as the signalling protocol

for call set-up, as has been specified by 3GPP, and IPv6 as the version of the IP protocol.

The access network and the packet-switched network remain the same, but UMTS release 5 introduces the concept of IP

Multimedia Subsystem (IMS). The IMS includes all new control and signalling functions for the management of multimediasessions, including voice calls and data sessions. It is functionally separated from the packet-switched core network,

which provides the transport functionality.


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Figure 3 PLMN migration from UMTS Release 4 to UMTS Releases 5/6

5.2. Trends in architectures

Circuit-switched architectures are today deployed with circuits and signalling managed by monolithic switches. ISUP

signalling and TDM links are used to carry voice calls between exchanges, which would be SSP in the fixed or transit

domain, and MSC in the mobile domain.

This situation has been quickly evolving in the last years, and the evolution from Circuit Switched into IMS architecture

can be depicted on an indicative timeline as follows.


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Figure 4 Core Network architecture evolution timeline

In NGN/soft switch architecture, circuits and signalling links are split and managed separately. Call Servers manage the

signalling and voice is transported via Gateways on packet backbone. NGN Call Servers control Gateways using Master-

slave protocols such as H.248 or MGCP. In most cases, the internal call control logic of NGN Call Servers is ISUP-based

and products are in most cases evolutions of corresponding circuit-switched architecture products.

NGN Call Servers usually reproduce the network experience of those legacy products. Typical NGN solutions are:

NGN call servers (and associated Gateways) in the international backbone for transit domain

VoIP call servers introduced on broadband lines in fixed domain

MSC R4 introduce NGN architecture in the mobile core network (air interface remaining TDM oriented)

IMS is a global, access-independent and standard-based IP connectivity and service control architecture that enables

various types of multimedia services to end-users using common Internet-based protocols. As such, it can meet all the

needs of fixed, mobile and interconnection models and describes a functional architecture, which means that several

physical implementations of IMS are possible.

Fixed

Transit

Mobile

ArrivalDate *

Circuit Switched NGN IMS

Cl5 subsSSP

Cl4 transitSSP

R99MSC

< 2005 2005-2010 > 2010

Cl5 subsNGN CS

Cl4 transitNGN CS

R4MSC

IMS


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5.3. Trends in session control protocols

Call control protocols play a key role in telephony system and the signaling interworking strategy is crucial for VoIP

interconnections. It has to closely follow the quickly-evolving interworking standardization.

The current industry trends can be described like this:

Circuit switched networks are widely deployed and ISUP (or variants) are still used today (TDM interworking will be

key in the signaling architecture)

BICC is today promoted by the mobile community for MSC R4 architecture

H323, designed by ITU-T to support VoIP technology, is progressively replaced on the access network by IETF SIP

IMS promotes SIP and other IMS-based protocols

SIP-I is currently implemented in NGN soft switches and is beginning to be present in MSC R4

Figure 5 Session Control Evolution (interconnection)

For mobile operators, BICC is the current session protocol Standardized in 3GPP R4 architecture. This protocol is used

and supported by all MSC R4 providers. But BICC is closely focused on GSM/UMTS and is not open to be extended to

NGN and IMS. BICC is not the target IP interconnection protocol but it is unavoidable in the context of MSC R4

interconnection.

Fixed and Transit networks are more SIP oriented but a transition will be mandatory to migrate from ISUP to SIP. This

transition could be supported by ISUP encapsulation in SIP (SIP-I). A common solution to support the PSTN/SDN services

between two NGNs is to develop a SIP-I specification based on ITU-T Q.1912.5, and address issues such as security, SIP

protocol profile and operator's specific ISUP variant.

Fixed

Transit

Mobile

Arrival Date

< 2005 2005-2010 > 2010

Domain

ISUP

BICC

H323

SIP-I

SIP-IMS

SIP

CircuitSwitched NGN IMS


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If the fixed-mobile convergence based on IMS is the target, SIP should become the protocol for fixed, mobile and transit

networks. But many efforts to standardize are yet to provide before they can use this protocol. Indeed, a number of SIP

profiles and SIP-I variants for interconnection have been proposed by different standardization bodies.

In ITU-T

TRQ.2815 defines the common capabilities supported by the interworking between SIP and BICC/ISUP for three SIP

profiles: Profiles A, B and C. Profile A makes reference to 3GPP TS 24.229 and was designed for use by 3GPP IMS

networks. Profile C, also called SIP-I refers to the use of SIP with a message body that encapsulates ISUP

information.

Q.3401 defines a SIP profile for NNI (Network-to-Network Interface) between two NGN operators, in order to support

voice service, e.g. VoIP (audio, text ), DTMF, T.38 fax, etc.. It contains a service-level signalling profile (i.e. SIP/SDP

profile) and

2008 Whitepaper Migrations to Ngn-ims

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