wp voice migration

8/2/2019 WP Voice Migration

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White Paper

2008-09-17 KEYMILE 2008

Migration scenarios of voice

on broadband access networks


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White PaperVoice Service Migration

2008-09-17 KEYMILE 2008 Page 2

Table of content

1 Abstract 4

2 Introduction 4

2.1 Voice over IP (VoIP) Considerations 4

2.1.1 VoIP implementation approaches 4

2.1.2 Quality of service and VoIP 4

2.2 Evolution towards the Next Generation Network (NGN) 5

2.2.1 Technical background 5

2.2.2 Commercial background 5

2.2.3 NGN requirements 6

2.2.4 Migration principles and procedures 6

2.3 Explanation of Terms 6

2.3.1 What is VoBB? 6

2.3.2 Voice over Internet 7

2.3.3 Voice over NGN 7

2.4 A closer Look at the NGN 7

2.4.1 NGN network elements 7

2.4.2 NGN protocols 9

2.4.3 PSTN replacement 9

2.4.4 What is IMS? 10

2.4.5 Use of IMS in NGN 11


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3 Migration Scenarios 12

3.1 Evolving from PSTN to NGN 12

3.2 Migration Steps for Telephony Networks 12

3.3 Existing Networks: PSTN for TDM Voice and Internet Access 12

3.4 PSTN Consolidation: High Capacity Exchanges 14

3.5 NGN in the Core Network: Class 4 Switch replacement 16

3.6 NGN in the Residential Area: CPE replacement 17

3.7 NGN in the Access Network: Class 5 Switch replacement 18

3.8 Shutdown of PSTN 19

4 How KEYMILE supports Voice Migration 20

5 Summary 20

5.1 Step by Step Migration 20

5.2 NGN is not only Voice 20

6 Abbreviations 21


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Abstract1

This paper presents an overview of the avail-

able and widespread public switched tele-phone network and also at the emerging nextgeneration network (NGN) under the aspect oftelephony services in the wireline access

network. It examines possible migration

scenarios from the TDM-based PSTN to thepacket-based NGN.

The terms VoBB, NGN and IMS are clarified inseparate sections.

Voice over IP (VoIP) Considerations2.1

VoIP implementation approaches2.1.1

Legacy TDM-based PSTN voice networksevolve to packet-based networks, where voiceover IP (VoIP) can be offered by two differentapproaches:

Next Generation Network (NGN):

NGN as a service application transportsvoice over managed and secured IP net-works with well defined guarantees for enduser reachability, communication quality,reliability and connectivity, while supportingservices inherited from the PSTN.

Voice over Internet:

Internet telephony with voice traffic routedon a best effort basis as an end-user orpeer-to-peer application on top of theInternet, providing only limited servicequality.

From an incumbent telephone service provid-ers perspective, as they adopt the migration toan end-to-end IP-based infrastructure, the NGNapproach becomes a more efficient way ofrouting and delivering voice traffic, as Internetcalls share bandwidth on the network with

other applications. The focus of this paper isthe NGN approach.

Quality of service and VoIP2.1.2

Looking at quality of service (QoS) in the VoIPapplication, the core IP network and the accessnetwork have to be distinguished.

Concerning the core network, IP QoS is basedeither on MPLS or can be accomplished byover-provisioning of bandwidth.

Guaranteeing QoS in the access networkrequires more attention as the available band-width is in general much lower than in the corenetwork. The traffic requirements for the voiceservice are quite predictable, enabling serviceproviders to introduce QoS by static provision-ing in the network.

Voice over Internet using SIP allows a clear

differentiation between services, which nor-mally will result in a good quality, but qualityremains unpredictable and varies over timeeven during a call.

On the other hand only a call with predictablebehaviour can have the guaranteed QoS. Thischaracteristic will be the main differentiationbetween voice over Internet and voice overNGN.

Introduction2


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Evolution towards the Next2.2Generation Network (NGN)

Technical background2.2.1Looking back 10 years ago the only telephonyservice a residential customer had available wasvoice service. With an analogue wire line orwith ISDN basic access the connection to thetelephony network was restricted to one or twonarrow band voice channels.

With the advent of the Internet the demand fordata transport increased. In the first years,Internet access was restricted to the narrowband voice channel transport. The drawback ofthis solution for the customer was twofold: First

the bandwidth for data transport was verylimited, and second the usage of Internet wasonly possible as an alternative to telephonyusage, at least for analogue wire line access.

Bringing DSL to the customers solved thistwofold problem with increasing bandwidthand now concurrent use of telephony andInternet services.

On the other hand Internet service provisioningimplied for the service providers the build-upof a data network based on packet transport in

parallel to the voice network based on TDMtransport.

The ever increasing data bandwidth of broad-band access lines brings now the potential ofnew services and also the possibility of voiceover IP (VoIP) transport.

Commercial background2.2.2

Traditional network and service providers arenowadays confronted with the risk of loosingtheir revenue by the following factors:

Competition from new market entrants anddecreasing customer loyalty

Increasing replacement of the fixed wire lineaccess by mobile access

Substitution of revenue generating TDMservices such as leased lines and telephonyaccess by packet based services (e. g. VoIP)

To remain competitive the network and serviceproviders are forced to take the followingmeasures:

CAPEX reduction by converging the TDM-based telephony and packet-based Internetnetworks, i. e. by sharing one commonnetwork infrastructure

OPEX reduction by simplified operation andmaintenance

Increasing the revenue by offering new(multimedia) services

In other words the two existing parallel net-works have to be converged to a single anduniversal network offering all services a cus-

tomer needs now and in the future. Thisnetwork is, from todays point of view, the nextgeneration network (NGN).

The ITU-T organisation has taken the effort toprovide a recommendation framework coveringthe next generation network in the Y.2000series.


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NGN requirements2.2.3

What conditions does the NGN need to fulfil toprovide the customers their requested servicesand to give the network and service providers

the competitive advantage over their competi-tion?

Continuity of the existing carrier-gradeservices offered to customers with the samequality, security and reliability

Interworking and interoperability betweenexisting and new networks and systems

Flexibility to incorporate new services

Quality of service (QoS) to guarantee theservice level agreements (SLA) for different

traffic conditions and servicesService continuity in the presence of faultswithin the network (survivability), offering oflife-lines (e. g. for emergency phones)

Generalised mobility for consistent andubiquitous provision of services

Migration principles and procedures2.2.4

A successful migration towards the NGN has tofollow some principles:

The migration of the legacy telephonynetwork to the NGN has to preserve theexisting investments as much as possible,e. g. reuse of the copper wires for DSLaccess, no replacement of the customertelephone sets and PABXs (at least in aninitial phase).

Cost control of the migration process.Bringing broadband data access to thecustomers also means bringing accessnetwork elements closer to the customers. Abig amount of network provisioning cost lies

in the network access area. Rolling outbroadband access should therefore bejustified by appropriate services with corre-sponding revenues. This implicates a step-wise migration procedure.

The migration steps depend on the specificservice provider and market situation, e.g.developing vs. developed country, or actualstate of the deployed copper network. Themigration steps presented in this whitepaper are not all mandatory and also havenot to be followed in the proposed order.

The migration procedure can be structured inthree main steps:

Optimization and preparation

Optimize the existing telephone network bya reduction of the number of local and trunkexchanges. Newly deployed access networkelements should be prepared for the NGN,e. g. Multi-Service Access Nodes (MSAN)which can realise both, TDM access andpacket access.

Capacity increase

Deploy NGN network elements to expandthe telephone network. NGN and PSTNnetworks coexist side by side.

PSTN replacement

Replace existing PSTN network elementswith their equivalent NGN network ele-ments. Customer equipment is replaced bypacket based and eventually multimediaservice capable equipment. The PSTN willcease to exist.

Note that network and service providers arenot able to control the replacement pace oflegacy telephones. Many customers requir-ing telephone service only will not be willingto replace their familiar handset. Services

handling this equipment must be maintainedby implementing media gateways in theaccess network or at the subscriberspremises.

Explanation of Terms2.3

What is VoBB?2.3.1

VoBB stands for voice over broadband. VoBBrefers to VoIP services that allow end users tomake and receive calls over a broadbandconnection, e. g. a DSL or cable TV connection.End users have direct access to the IP networkeither with IP capable terminals or with terminaladapters.

VoBB can be used as voice over Internet or asvoice over NGN.


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Voice over Internet2.3.2

Voice over Internet is Internet telephony usingVoIP routed on a best effort basis providingonly limited quality and guarantees. With

increasing competition, quality of servicebecomes an issue. Network congestion andoutages do occur and affect VoIP quality andreliability. When downloading a large file andmaking a simultaneous VoIP phone call, inter-ferences may be heard or the call even may bedropped.

Voice over Internet also lacks regulatory andlegal requirements such as emergency calls orlawful interception.

Voice over NGN2.3.3What is NGN?

ITU-T Y.2001 defines the next generationnetwork (NGN) as follows:

NGN is a packet-based network able to pro-vide telecommunication services and able tomake use of multiple broadband, QoS-enabledtransport technologies and in which service-related functions are independent from under-lying transport related technologies. It enablesunfettered access for users to networks and to

competing service providers and/or services oftheir choice. It supports generalized mobilitywhich will allow consistent and ubiquitous pro-vision of services to users.

One of the main characteristics of NGN is thedecoupling of services and transport, allowingthem to be offered separately and to evolveindependently. NGN allows the provisioning ofboth existing and new services independentlyof the network and the access type used.

In NGN the functional entities may be distrib-uted over the infrastructure. When they arephysically distributed, they communicate overopen interfaces. Standardised protocolsprovide the communication between functionalentities. Interworking between NGNs ofdifferent service providers and between NGNand existing networks such as PSTN, ISDN andGSM is provided by means of gateways.

NGN supports both existing and NGN awareend terminal devices. Hence terminals con-nected to NGN include e. g.

analogue telephone sets

fax machines

ISDN sets

cellular mobile phones

GPRS terminal devices

SIP terminals

Ethernet phones through PCs

digital set top boxes

cable modems

NGN supports quality of service related toreal-time voice services (with guaranteedbandwidth, guaranteed delay, guaranteedpacket loss, etc.) as well as security.

A major feature of NGN will be generalisedmobility, which will allow consistent provision-

ing of services to a user, i. e., the user will beregarded as a unique entity when utilisingdifferent access technologies, regardless oftheir types. This feature is also called nomad-ism.

A closer Look at the NGN2.4

NGN network elements2.4.1

NGN makes use of standards based networkelements. The following network elements have

been introduced by NGN:

Gateway (GW):

The GW is responsible for the media streamconversion, i. e. the conversion of TDMbased voice signals into IP packets and thesignalling protocol conversion. There arethree main GW types:

Residential Gateway (RG)A RG is located at the subscribers homeand provides packetisation of traditionaltelephone services. It supports a small

number of legacy line side interfaces suchas POTS or ISDN-BA. Existing telephonescan be reused with a RG. Upon receivingthe appropriate instructions from the callserver (CS), the RG sets up the media pathfor the voice traffic and performs addi-tional functions such as echo cancellation,compression and tone generation. The RGis connected to the broadband IP accessline. A RG is sometimes referred to asintegrated access device (IAD).

Media Gateway (MG)

An MG is located at the IP network edgetowards the subscriber and provides the


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same functions as a RG. An MG con-nects several hundred subscribers of theresidential area it is placed in. Beside thelegacy line side interfaces it also supports

ISDN primary rate interfaces for TDMPABXs.The MG is typically deployed withinclass 5 switch replacement scenarios. Aclass 5 NGN offers a future-proof networkexpansion and reduced maintenancecosts.

Trunking Gateway (TG)A TG is located between the PSTNnetwork and the packet network. A TGpacketises circuit-switched trunks in thePSTN and vice versa. It terminates both

the PSTN trunks and packet streams in thepacket network, and manages the mediaconnections for the termination of thePSTN trunks as commanded by the callserver. It offers no POTS or ISDN line sideinterfaces, but n x E1 or STM-1 interfaces.By installing TGs as part of new networks,service providers can interconnect existingPSTN TDM networks with the NGN packetnetworks.

Call Server (CS) (or softswitch or mediagateway controller (MGC))

The CS provides the control and resourceallocation plus overall management of aNGN call. A CS processes the messagesreceived from the GWs using a standardisedmedia gateway control protocol. It alsocommunicates with other CSs to set-upend-to-end calls.

A CS typically controls several GWs. As thiscontrol function is centralised for mostservices, the CS resides on a powerful serverplatform.

A GW normally connects to one primary CS.If GWs are controlled by different CSs,control information is exchanged betweenthe CSs by means of the BICC (BearerIndependent Call Control) or SIP-T (SIP fortelephones) protocols.

Signalling Gateway (SG)

A SG interconnects the NGN with the PSTNsignalling network, i. e. it connects a CS tothe signalling network SS7, allowing end-to-end signalling for calls between NGN andPSTN. The SG receives ISUP (ISDN User Part)messages and forwards them to the CS byusing the SIGTRAN protocols.

Application Server (AS)

An AS implements a software applicationproviding information required by a remoteor local application. This application istermed the client. A typical example is anemail server that passes email data to anemail client on request.

Other applications can be announcementservices or other intelligent network (IN)

services.


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Highlights for the CS-based PSTN emulationare:

Provides current PSTN and ISDN serviceswith an unchanged presentation for allinterfaces.

Services and features are provided by thecall control of the CS.

The CS uses the H.248/MEGACO protocolfor the control of the media or residentialgateways.

Emulation domain (CS) and IMS sessioncontrol interwork via SIP.

Possibility to re-use installed access equip-ments (POTS, ISDN, PRI, CAS etc).

Retain existing subscriber base throughimmediate migration.

PSTN simulation

PSTN simulation refers to the provisioning ofPSTN- and ISDN-like services to legacy termi-nals and advanced terminals such as IP phones.However, there is no guarantee that PSTNsimulation would provide all features that havebeen available to the PSTN user. On the otherhand, PSTN simulation may provide additional

features and capabilities that have not beenavailable to the users of PSTN.

Contrary to the CS based service controlconcept of PSTN emulation, the PSTN simula-tion uses the IP multimedia service component.The application server (AS) houses the servicecontrol logic and service execution environ-ment behind CS entities.

Highlights for the IMS based PSTN simulationare:

Voice service is limited to simulation, withSIP based voice application server.

Most commonly used and popular voiceservices are simulated, e. g. CLIP, CallForwarding etc.

Focus on new multimedia services.

Advanced multimedia services like push-to-talk, video conferencing, IP Centrex etc.

Converged services across different accessdomains, e. g. mobile networks, broadbandwireline networks (DSL, FTTH, etc.), WiFi

Interworking with the PSTN emulationdomain via SIP.

The figure 1 below shows a high-level presen-tation of how emulation and simulation isperformed and the relationship betweendifferent networks and NGN. As shown in thefigure, there are several ways how user equip-ment can be connected to an NGN providingeither emulation or simulation of PSTN.

What is IMS?2.4.4

Introduction to IMS

The IP multimedia subsystem (IMS) is anarchitectural framework for delivering Internetprotocol (IP) multimedia services to end users.

IMS is defined with open standards from 3GPPand ETSI and is based on IETF protocols (SIP,RTP, RTSP, COPS, DIAMETER, etc.). IMS isdesigned for both wireless and wireline net-works and is the basis for fixed and mobileconvergence (FMC).

IMS supports operation and interworking with a

variety of external networks via defined refer-ence points. Specifically it is capable of inter-working with the PSTN.


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IMS features

IMS delivers IP-based multimedia communi-cations: Person-to-person and person-to-machine.

IMS fully integrates real-time with non-real-time multimedia communications, e. g. livestreaming and chat.

IMS enables different services and applica-

tions to interact, e. g. combined use ofpresence and instant messaging.

IMS provides control of the IP connectivity inaccess networks (QoS, admission control,authentication, etc.).

IMS enables interworking and interoperabil-ity with legacy and other networks.

IMS is access technology independent forsession/call control and applications.

Use of IMS in NGN2.4.5

In the NGN environment the IMS servicecomponent supports the provision of SIP-basedmultimedia services to NGN terminals. It alsosupports the provisioning of PSTN simulationservices.

In other words, NGN provides the communica-tion network infrastructure while IMS is respon-sible for the service control.

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Evolving from PSTN to NGN3.1

A main target for a network operator is the

reduction of parallel communication networks,i. e. TDM for voice and IP for data, to a singlenetwork, preferably based on IP transport. Thisgoal can be achieved by extending the IPnetwork reach into the access network area, i. e.by implementing IP based multiservice accessnodes (MSAN) close to the subscribers loca-tions.

The advantages of one common IP networkare:

The cost for the evaluation, commissioning

and operation of a single network is lowerthan for two or more parallel networks.

Operational costs in IP networks tend to belower than in PSTN.

The IP transport network is future-proof.

The IP network is a key component of a NGN.It provides clearly separated transport, controland service layers. The coupling of the differentlayers is assured through open and standardsbased interfaces.

An NGN is prepared for future multimedia

services based on the IP multimedia subsystem(IMS).

Migration Steps for Telephony3.2Networks

Having in mind the three main steps asdescribed in the section Migration principlesand procedures:

optimisation and preparation,

capacity increase, and

PSTN replacement,

these main steps are broken down into fivemore detailed migration steps. The proposedmigration procedure primarily targets incum-bent local exchange carriers (ILEC) operatingfixed networks.

Note that there is no standard procedure fittingevery network deployment or service provider

demand. There may be many differences in theareas of geographical coverage, network growrate, aging legacy equipment or demand fornew services. The extent and sequence ofmigration steps can therefore vary and somesteps even may be omitted.

Voice migration steps:

Migration Migrationstep

Network

Start Existingnetworks

PSTN for TDM voice and nar-rowband Internet access andbroadband Internet access viaDSLAMs.

Step 1 PSTN con-solidation

Introduction of high capacitylocal and trunk exchanges,replacement of DSLAM andDLC network elements byintegrated MSANs.

Step 2 NGN inthe corenetwork

Replacement of trunk ex-changes (class 4 switches) byclass 4 call servers and trunk-ing gateways (TG).

Step 3 NGN in theresidentialarea

Deployment of residentialgateways to connect tolegacy telephones, and CPEreplacement with soft clientsor IP phones.

Step 4 NGN inthe accessnetwork

Replacement of local ex-changes (class 5 switches) byclass 5 call servers and mediagateways. Media gatewayscan be integrated intoMSANs.

Step 5 Shutdownof PSTN

Replace remaining TDMexchanges

Existing Networks: PSTN for TDM3.3Voice and Internet Access

The public switched telephone network (PSTN)is a hierarchical network built around call-processing and routing units known asexchanges. The PSTN provides carrier-gradequality with well defined QoS criteria andstandardised engineering rules.

Local exchanges (LE), also known as class 5switches, provide switched services to the

Migration Scenarios3


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subscriber device, e. g. a telephone set. A LEcommonly handles 10,000s to 100,000s of linesdepending on whether it is a rural or urbanswitch.

Trunk exchanges (TE), also called class 4switches, provide routing/switching betweenLEs. Arranged in a hierarchical architecture,there can be two levels of TE: Primary TE andsecondary TE. There is typically 1 secondary TEto every 10 LE, and 1 primary TE to every 6 or7 secondary TE. There is also a small number ofTEs used as international gateways, about 1 forevery 2 primary TE.

In this network, all voice traffic is transportedover TDM. The digital loop carrier nodes (DLC)perform the concentration of the subscribersvoice traffic to higher capacity links.

The voice related signalling is handled by theSS7 signalling network. The signalling transferpoint (STP) provides the transfer of signallingmessages. A service control point (SCP) imple-ments the intelligent networks (IN) value-addedservices.

With the adoption of Internet usage, localexchange operators provide connectivity toInternet service providers (ISP) to their subscrib-ers.

In a communication network the Internet accessis provided either through narrowband dialupservices using the inband bearer channel, orthrough broadband DSL, using splitters toseparate the voice signal from the data signal.

The data gateway between the PSTN and theIP network is a narrowband access server (NAS).The DSL line is connected to a DSLAM and isterminated in a broadband remote accessserver (BRAS).

In general telecom service providers offer their

subscribers DSL for broadband data access.Due to the limited reach of DSL, the digitalsubscriber line access multiplexers (DSLAM),terminating the digital signal at the networkside, must be brought closer to the subscriber.

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PSTN and IP network architecture for voice and data applicationsFigure 2:


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When deploying an MSAN, a network operatorhas to keep in mind that he will migrate thisMSAN to NGN one day. A product offering thereuse of the POTS, ISDN and DSL line cards will

be preferred.In an MSAN prepared for NGN, the TDM voicepart can be upgraded to VoIP by simplyreplacing or even upgrading the protocolconversion unit (e. g. V5.2) to an media gate-

way. All other units can be reused. The TDMuplink unit will not be used anymore.

An MSAN upgrade is a fast and cost effectiveway of the migration to NGN in the access

area.

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DSL Line Card

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MSAN migration with reuse of the POTS/ISDN line cards, the DSL line cards and the IP uplink unitFigure 4:


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NGN in the Core Network: Class 43.5Switch replacement

Replacing the trunk exchanges (TE, class 4

switch) at the core of the PSTN by a class 4 callserver and trunking gateways (TG) is the firststep towards a true NGN. TGs are mainly usedto offload long distance calls from the PSTN.The PSTN edge, i. e. the local exchanges, is nottouched.

A Trunking Gateway

emulates a TE and the value added services.

replaces a TE or increases the traffic handling

capacity of a TE.interfaces to the LE and TE on the PSTNside.

communicates with a class 4 call serverthrough H.248/MEGACO protocols.

Implementing the PSTN emulation service willkeep the subscribers unaware of the migrationto NGN.

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TG Trunkting Gateway

PSTN and IP network architecture using trunking gatewaysFigure 5:


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NGN in the Residential Area: CPE3.6replacement

The introduction of broadband access networks

enables the deployment of voice and multime-dia IP clients at the subscribers location. Asubscriber using an IP phone or a legacy phoneconnected to a residential gateway (RG)disposes of a pure IP access towards thetelecommunication network.

The subscriber can be connected to a DSLAM,handling pure IP traffic, or he can be connectedto a MSAN offering new multimedia services.These new services will allow service providers

to differentiate and compete with alternativecarriers.

It is assumed that voice service is implementedas PSTN simulation, using SIP instead of H.248/MEGACO as the control protocol. Using SIPalso enables the seamless evolution towardsthe IMS.

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PSTN and IP network architecture using residential gateways and IP phonesFigure 6:


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NGN in the Access Network:3.7Class 5 Switch replacement

Class 5 call servers and media gateways (MG)

replace local exchanges (LE, class 5 switch) atthe edge of the PSTN. This extends the NGNcloser to the subscribers location. MGs aremainly used to increase the network capacity orto replace obsolete LEs.

A Media Gateway

emulates a LE, its supplementary servicesand optionally the value added services.

replaces a LE or increases the traffic handlingcapacity of the access network.

interfaces to the subscribers on the PSTNside.

communicates with a class 5 call serverthrough H.248/MEGACO protocols.

An MG can be deployed as a separate networkelement or be integrated into an MSAN,offering also DSLAM and multimedia function-ality. Implementing the PSTN emulation servicewill still keep the subscribers connected to anMG unaware of the migration to NGN, aslegacy interfaces (POTS, ISDN) are providedover the MSAN.

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NT DSL Network TerminationRG Residential GatewaySCP Service Control PointSG Signalling GatewaySTP Signalling Transfer ProtocolTE Trunk Exchange (Class 4)TG Trunkting Gateway

PSTN and IP network architecture with Media GatewaysFigure 7:


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Shutdown of PSTN3.8

As a final migration step towards the all-embracing NGN, the remaining legacy PSTNequipment is replaced by NGN networkelements.

The target for this last step is the replacementof obsolete equipment, i. e. equipment reach-ing end-of-life, and cost reduction by havingone single network to maintain and operate.

Note that also in this scenario subscribers stillcan use their legacy equipment which isconnected to a residential gateway or to amedia gateway.

PSTN

SS7

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DSL

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NT DSL Network TerminationRG Residential GatewaySG Signalling GatewayTE Trunk Exchange (Class 4)TG Trunkting GatewayVoIP

Data

TDM Voice

Signalling

IP network architecture using IP phones, residential gateways and MSAN integrated media gatewaysFigure 8:


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2008-09-17 KEYMILE 2008 Page 20

KEYMILE is a leading manufacturer and sup-plier of next generation access systems with a

long history in providing voice applicationssupporting POTS, ISDN and V.5x services. Itsproduct spectrum covers IP based DSLAMs andTDM or IP based MSANs.

KEYMILE products are used as access platformsand allow seamless conversion from TDMtowards packet-oriented services. They com-bine carrier-grade broadband access, teleph-ony and data interfaces in a single compactnext generation access platform with effective

IP-DSLAM functionality. While supportinglegacy telephony with POTS, ISDN, V5.x and

broadband services, the MSANs can smoothlybe upgraded to the next generation networkbased on H.248/MEGACO or SIP protocols.Concurrently they provide high quality TriplePlay and broadband business services.

KEYMILE serves customers in over 100 coun-tries with subsidiaries worldwide and a globalnetwork of partners.

Step by Step Migration5.1

The PSTN will not be replaced by the voiceNGN from one day to another. There will be astepwise replacement of obsolete PSTNnetwork elements or a capacity expansion,introducing NGN network elements, as

trunking gateways in the network core,

residential gateways at the subscribershome,

media gateways at the network edge,together with

call servers controlling the deployed gate-ways.

Voice will be converted from TDM to IP first inthe core network. The TDM to IP conversionwill gradually continue at the subscriberslocation and finally expand to the edge of thenetwork.

The migration can be driven by cost, e.g. OPEXreduction, driven by increased capacity

demand or by the service providers aiming tooffer new (multimedia) services to their custom-ers. In any case the specific factors influencingthe migration must be considered carefully bythe service provider.

NGN in the access network is tightly coupledwith the deployment of broadband dataaccess. Digital loop carriers (DLC) and digitalsubscriber line access multiplexers (DSLAM) willconverge to multi-service access nodes (MSAN)offering the functionality of a DLC, DSLAM andmedia gateway in one network element.

MSANs will be placed close to the subscribers

homes to be able to deliver the high data ratesrequired for multimedia services.

NGN is not only Voice5.2

NGN not only delivers voice service butenables the deployment of multimedia serv-ices. Multimedia services using the IMS arebased on a NGN infrastructure. NGN is there-fore a precondition to IMS.

The focus of this white paper lies on theessential elements of a migration from TDMvoice to VoIP, mainly in the wireline access area.There are many other factors in the access orcore network influencing the migration strat-egy. Among them are:

Revenue from new services

Value-added NGN voice

Multimedia services

Segmentation and services

Enterprise voice, VoIP and hosted Centrex

servicesEnterprise IT outsourcing

Detailed CAPEX evaluation

Cost of NGN core network elements

Cost of converged multi-service accessnetwork elements (MSAN)

Cost of bringing fibre closer to thesubscribers

Detailed OPEX model

Staff training for new network elements

Increased efficiency through convergence

How KEYMILE supports Voice Migration4

Summary5


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2008-09-17 KEYMILE 2008 Page 21

Abbrevia-tion

Meaning

3G Third Generation mobile network orservice

3GPP Third Generation Partnership Project

AS Application Server

BB Broadband

BICC Bearer Independent Call Control

BRAS Broadband Remote Access Server

CAMEL Customized Application for Mobile net-work Enhanced Logic

CAP CAMEL Application Part

CAPEX Capital Expenditure

CAS Channel Associated SignallingCLIP Calling Line Identification Presentation

COPS Common Open Policy Services

CPE Customer Premises Equipment

CS Circuit Switched

CS Call Server

DIAMETER DIAMETER is a protocol intended foraccess, authorization and accountingsupport

DLC Digital Loop Carrier

DSL Digital Subscriber Line, e. g. ADSL orVDSL

DSLAM Digital Subscriber Line Access Mult i-plexer

E1 First level of PDH, 2048 kbit/s

ETSI European Telecommunications StandardsInstitute

FMC Fixed and Mobile Convergence

FTTx Fibre-to-the-x, x = Home or Curb or

GoS Grade of Service

GPRS General Packet Radio Service

GSM Global System for Mobile communication

H.248 Media gateway control protocol, identi-cal to MEGACO

IAD Integrated Access Device

IETF Internet Engineering Task Force

IFP Internet Facsimile Protocol (T.38)

ILEC Incumbent Local Exchange Carrier

IMS IP Multimedia Subsystem

IN Intelligent Network

IP Internet Protocol

ISDN Integrated Services Digital Network

ISDN-BA ISDN Basic Access

ISDN-PRA ISDN Primary Rate Access

ISP Internet Service Provider

Abbrevia-tion

Meaning

ISUP ISDN User PartIT Information Technology

ITU-T International Telecommunications Union Telecommunication standardizationsector

IUA ISDN Q.921-User Adaptation layer

IWF Interworking Function

LE Local Exchange (class 5 switch)

MEGACO Media Gateway Control protocol

MG Media Gateway

MGC Media Gateway Controller

MPLS Multi Protocol Label SwitchingMSAN Multi Service Access Node

NAS Narrowband Access Server

NGN Next Generation Network

OPEX Operational Expenditure

PABX Private Automatic Branch Exchange

PC Personal Computer

PDH Plesiochronous Digital Hierarchy

PLMN Public Land Mobile Network

POTS Plain Old Telephone Service

PRI Primary Rate Interface

PSTN Public Switched Telephone Network

Q.931 ISDN connection control protocol

QoS Quality of Service

RG Residential Gateway

RTP Real-time Transport Protocol

RTSP Real-Time Streaming Protocol

SCP Service Control Point

SCTP Stream Control Transmission Protocol

SDH Synchronous Digital Hierarchy

SG Signalling Gateway

SIGTRAN Signalling Transport (= IUA / SCTP)

SIP Session Initiation Protocol

SIP-T SIP for Telephones

SLA Service Level Agreement

SS7 Signalling System #7

STM-1 First level of SDH, 155520 kbit/s

STP Signalling Transfer Point

TDM Time Division Multiplexing

TE Trunk Exchange (class 4 switch)

TG Trunking Gateway

TISPAN Telecoms & Internet converged Services& Protocols for Advanced Networks

Abbreviations6


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2008-09-17 KEYMILE 2008 Page 22

Abbrevia-tion

Meaning

TV Television

UDP User Datagram Protocol

UDPTL UDP Transport Layer

V5.x V5.1 or V5.2

VoBB Voice over Broadband

VoIP Voice over IP


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Publisher

KEYMILE GmbHWohlenbergstrae 330179 Hanover, Germany

Phone +49 511 6747-0Fax +49 511 6747-450

Internet www.keymile.comMail [email protected]

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