Feb2010 Ims Voip 3g Lte Strategic Swp

8/8/2019 Feb2010 Ims Voip 3g Lte Strategic Swp

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S T R A T E G I C W H I T E P A P E R

Although the industry is trialing and preparing to commercialize Long Term Evolution (LTE)

as the next-generation mobile technology, what are the plans for voice? The confusion

and misinformation about this is partly due to the tremendous revenues mobile operators

derive from mobile voice and the opportunity to create disruptive approaches in the

marketplace. This paper evaluates the methods operators use for voice to compete with

alternative providers. The result is clear IMS best enables operators to create voice servicesthat include partnering with application and content providers, realize the benets of

LTEs all-IP network, and preserve global roaming and interoperability that we have

achieved in todays 2G/3G networks.

Whats Next for Mobile Voice?The case for IMS VoIP in 3G/LTE


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Table of contents

1 1.Introduction

1 2.Mobilevoice:past,presentandfuture

2 2.1 Long Term Evolution

3 2.2 Subscribers expectations for LTE mobile voice4 2.3 Mobile voice competition

6 3.Comparison

7 3.1 IMS

9 3.2 CSFB

10 3.3 Custom methods (circuit core, LTE packet access)

11 3.4 Summarizing the three methods and recommendations

12 4.ThePathtoLTEandtheOneVoiceInitiative

13 5.Alcatel-Lucentleadership

13 5.1 Alcatel-Lucent end-to-end LTE

13 5.2 Alcatel-Lucent end-to-end IMS

15 6.Conclusion

15 7.Contacts

16 8.Acronyms

16 9.References


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Whats Next for Mobile Voice? | Strategic White Paper 1

1. Introduction

LTE will solve todays pressing needs for increased mobile data bandwidth. The popularity of devicessuch as the iPhone, Android and BlackBerry, and services such as video and social networkingare rapidly outpacing 3Gs ability to effectively deliver services, causing some operators to reconsiderpricing plans for mobile data. Instead of reducing service usage, most operators prefer to increasesubscribers usage of mobile data by deploying LTE.

LTE will provide an experience that was previously available only in xed broadband, owing toLTEs high bandwidth and Quality of Service (QoS) which surpasses that available in 3G. Unlikexed broadband, it will be an untethered experience that people can take with them anywhere, andit will be personal instead of being shared with other household members. Clearly, the improveddata service is extremely benecial to consumers and enterprise users.

LTE is designed to be a at, all-IP network, from the handset, through the radio access, across thepacket core and into the services layer. The all-IP network provides operators with economic benetsfrom both the simplied networks operations (lower costs) and the new services created with IPsinherent exibility and utility (improved revenues). In such an all-IP network, voice is provided asVoice over IP (VoIP). However, some operators and vendors are considering interim methods so they

can focus on LTEs initial service as a data-only overlay.

There are several methods for LTE to deliver voice and short message service (SMS), such as thetwo leading methods, IMS VoIP and Circuit Switched Fallback (CSFB), as well as other custom,non-standard methods characterized by a 2G/3G circuit MSC linked to VoIP over the LTE packetaccess. Except for IMS VoIP, all methods rely heavily on reusing the existing 2G/3G MSC. Reusingthe existing 2G/3G MSC provides benets such as complete feature transparency plus leveraging theMSCs already established integration into the Operational Support Systems and Business SupportSystems (OSS/BSS). However, it limits the introduction of new IP services (such as video telephony)and prevents operational savings based on an all-IP LTE network. Reusing the 2G/3G network forCSFB causes the LTE data session, during voice calls, to fall back to 3Gs lower data rates, or is evensuspended in 2G due to a lack of simultaneous voice and data capability. The remaining methods

either limit the ability to retain LTE service while roaming or, due to a smaller ecosystem, reducethe selection and variety of LTE handsets available to support that custom method.

Each of these methods has different characteristics for deployment, total costs and the capabilitiesenabled for the subscriber; these factors are evaluated in this paper. The essential LTE voice questionthat operators ask themselves is which method should they use initially, to provide LTE voice? WhileIMS VoIP is regarded as the desired end state, should and can they avoid investments in an interimmethod by proceeding directly to IMS VoIP?

This paper examines the options for providing voice with LTE; and it builds the case for starting withor rapidly moving to IMS VoIP as the best method to help operators realize LTEs potential for innova-tive and all-IP operational savings, preserve LTEs bandwidth during voice calls, minimize call setup

delays, assure global roaming and interoperability, and avoid the loss of lucrative voice services tothird-party ACPs who can readily provide VoIP service in LTE, much as they have in xed broadband.

2. Mobile voice: past, present and future

How do people use their mobile phones? For most people, it is used for talking and texting withtheir friends, families and colleagues. People are eager to connect with each other and are willingto pay for it. Figure 1 shows that voice currently provides the majority of operators revenues [1].Although voice revenues as a portion of total revenues are steadily declining, voice remains theprimary revenue contributor for the next several years. Add into this that approximately half of datarevenues come from texting (SMS) [2] and it is clear that the contributions of voice and texting arefundamental to operators continued commercial success.


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Whats Next for Mobile Voice? | Strategic White Paper2

Figure 1. Mobile services forecast for voice

Does this mean the future remains the same as the past, that voice and texting are the predominantsources of mobile operators revenues? No, because data services are increasingly popular. The numberof data subscribers and their data usage continues to grow rapidly. This behavior is fueled by theproliferation of 3G data networks, the widespread availability of multimedia and smartphones, theavailability of content and social networking sites using mobile devices, and affordable mobile dataservices. However, voice and SMS are fundamental services in the operators portfolio because oftheir signicant revenues plus voices role as the base application on which to build further services,such as GSMA RCS, high-denition voice and blending with social networking sites. The realizationof enhanced voice relies upon VoIP, not circuit switched voice. It is with IMS and VoIP that theoperators can compete and partner with the ACPs.

2.1LongTermEvolutionData services rapid growth places stress on 3G networks, thereby driving the emergence of LTEas the means to deliver greater quantities of mobile data affordably. LTE enhances the UniversalMobile Telecommunications System (UMTS) architecture, providing both improved bandwidthand an improved Quality of Service (QoS) for these data-intensive services. LTE is based on anEvolved UMTS Terrestrial Radio Access Network (eUTRAN) and an Evolved Packet Core (EPC),which incorporate new modulation techniques and a at, all-IP architecture for the efcient deliveryof mobile data services. The LTE network is shown in Figure 2 and discussed in the Alcatel-Lucentwhitepaper, LTE Network Architecture: A comprehensive tutorial [3].

In contrast to 3G networks usage of circuit-switched voice and SMS, plus packet-switched data, anLTE network is all-IP. All trafc in an LTE system is carried as IP, providing seamless, high-speedconnections between a handset or user equipment (UE), and various packet data networks, suchas the Internet, IMS, and Content Delivery Networks (CDNs). The various IP bearers in the LTEsystem are assigned specic QoS Class Identiers (QCIs) that correspond to specic treatment levelsfor connection types, priority, delay budgets and packet error loss rates. A single handset or UE mayhave multiple IP bearers serving it, where individual bearers serve conversational voice, gaming ses-sions, streaming video, e-mail or messaging, for example.

Not only does LTE provide a more efcient and therefore more economical network for mobile data,it also provides enhanced performance for the people who use its services. Gartner depicts LTE asbeing well into a broadband-like experience zone, providing data service that was previously onlyavailable on xed broadband [4].


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Figure 2. LTE network architecture

2.2SubscribersexpectationsforLTEmobilevoice

With LTE providing a broadband-like experience, how does this affect the immense voice revenuesand prots that mobile operators today reap from 2G and 3G services? The erosion in xed operators

revenues that began approximately ten years ago stemmed from technology competition for theircore voice services. This technology competition came about from both mobile substitution forxed voice services plus innovative voice over IP (VoIP) services from ACPs such as Vonage andSkype. Both of these were so attractive to consumers and enterprises that they changed a centuryof past practices and shifted to mobile phones and xed VoIP services that often came with moredropped calls, poor mobile voice quality and extra steps needed in order to place a call. But thenew services were important in fundamental ways that outweighed the negatives, such as mobility,personalization and pricing.

Considering what comes next for mobile voice, what are some key voice factors that appeal topeople? They seek services that:

Providehigh-speedInternetaccess: to preserve LTEs data rates during voice calls

Blendmyvoicewithotherservices: such as presence, messaging and social networking

ReducehowmuchIspendonvoice: avoid the high fees caused by international calling orby exceeding monthly usage limits

Movevoicequalityoutofthe1950s: utilize high-denition voice (HD voice) for noisy environments,speakers of different native languages, whisper privacy, auto-speech recognition, young childrenshigh-pitched voices and other such situations

Voice is fundamentally human, yet the mobile voice experience has not made much improvementover the past 15 years except for price bundling, discounts on volume plans and fewer dropped calls.This is extremely risky for the mobile operator when we consider the competitive situation createdby LTE. With LTE, the voice competition comes not only from other mobile operators, but also from

ACPs. People spend a lot on voice service. LTE creates a broadband-like experience, comparable tosome digital subscriber line (DSL) or cable modem services, so an ACP, using the mobile Internet,can readily extend VoIP services much as they did with xed broadband.

When mobile operators launch the initial LTE data-only services, such as a laptop with an LTEdongle, there is no guarantee that the LTE-enabled laptop will be used only for data services. AnACP-provided VoIP service can be readily extended to the laptop. And while the ACPs VoIPservice might suffer from some drawbacks, such as being delivered using best effort data instead ofconversational voice, it will appeal to some key subscribers, just as it has in xed broadband. Hence,the initial subscribers to an LTE data-only service could very well be the start of a shift of voiceusage from the mobile operator to an ACP-based service. The people who would most likely begin

UE eNodeB

eUTRAN EPC

MME PCRF

HSS

S-GW P-GWLTE-Uu SI-U

S1-MME S11 Gx Rx

Cx, ShS6a

S5/S8 SGi IP services:

IMS


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this shift are those who are most valuable to the mobile operators volume callers, global callersand young millennials who bring with them the habits of xed broadband (messaging, socialnetworking, and free is the new price).

Just as surely as xed broadband created a new market of alternative voice providers, so too willmobile broadband. The questions are:

What will the ACPs mobile voice offerings look like?

How will people react to these new services?

Can the mobile operator respond?

2.3Mobilevoicecompetition

To answer these questions, it is also necessary to consider capabilities that we take for grantedtoday. A 2G/3G mobile service allows a person to call anyone on the planet who has xed or mobileservice this is a remarkable accomplishment. The public network has achieved global intercon-nectivity for voice and texting service. People can travel outside their home network and still accessthese same 2G/3G voice and texting services in another networks service area or when they are inanother country. They retain their telephone number while roaming so that even while on vacationor working elsewhere, their social circle still calls the same number. Given these considerations, lets

examine the various options for LTE services in more detail. A summary is shown in Table 1, andthe points are discussed further in the subsequent text and in Section 3.

Table 1. Services comparison

ACPs mobile VoIP

Pros: The ACPs mobile VoIP service will resemble their xed services. The ACPs, such as Skype

and Google

, are well versed at blending voice with other services such as messaging, social net-working sites, or providing innovative features such as converting voicemail to e-mail. The voiceservice is priced relatively low or even free if supported by some alternative revenue source such asadvertising or fees on advanced services. And wideband audio is possible between two users servedby an all-IP path. The typical circuit mobile voice service, using 3GPPs Adaptive Multi-Ratecoder-decoder (AMR CODEC) ranges from 300 to 3400 Hz. In contrast, wideband CODECssuch as 3GPPs AMR-Wideband (AMR-WB) extend the frequency range to 50 to 7000 Hz, andSkypes SILK CODEC further extends the upper frequency to 12,000 Hz.

LTE-SE SEES PS MLE oP MLE PETS SF MLE PETS MS oP

Preserve LTEs data rates during voice calls

Blending GSMA RCS begins to blend voice

Pricing

Wideband voice

Roaming Might be prohibitive due to dataroaming tariffs and perhaps the lackof conversational voice QCI

Global interoperability Requires the circuit PSTN forin-calling and out-calling of voice;other services problematic

Handset variety and supply Limited requires laptop orsmartphone and software clientinstallation


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Cons: Although technically an ACPs mobile VoIP subscriber could roam anywhere there is amobile data connection, the price may be prohibitive due to relatively high-priced data roamingtariffs. While LTE solves the packet bandwidth problem, if the ACP mobile VoIP user leavesLTE coverage and encounters either 2G service or over-occupied 3G packet services, they willnot be able to use their packet-based service. Currently, the ACP-based VoIP services havelimited interoperability, requiring the voice calls to transit the circuit PSTN, losing many ofits IP-based service and pricing advantages. Similarly, other services such as video telephony

are not available between two ACPs. The handset supply is limited to devices onto whicha soft client can be installed by the user; this expense and limited selection appeals to anarrower audience.

Mobile operators CSFB

Pros: With a well developed ecosystem, the subscriber benets from excellent roaming, globalinteroperability and an extensive selection of handsets. Techniques exist for the LTE voice serviceto be served by the existing 2G/3G circuit voice network, using 3GPPs Circuit SwitchedFallback (CSFB).

Cons: During a voice call the LTE data service is suspended. Along with the voice, the dataalso falls back to 3G which has a lower data rate. If the call falls back to 2G, the data serviceis suspended altogether due to a lack of simultaneous voice and data in 2G. Starting from LTE

and falling back to 2G/3G, the voice calls setup delay adds from approximately 1.5 secondsfor 3G to 2.5 seconds for 2G, and adds a further 3 seconds for some calls if the LTE and2G/3G coverage areas were not precisely engineered to match. The standard 2G/3G circuitvoice service is siloed from other services, in that it is not blended with messaging, presenceor social networking sites. The Global System for Mobile Communications Association RichCommunication Suite (GSMA RCS [12]) initiative uses IMS to overcome these limits in 3Gto create enhanced services using circuit voice, but aside from this the 2G/3G network doesnot readily provide new IP-based services with global interoperability and quality of service,such as video services require. However, the 2G/3G circuit voice service is relatively highpriced and generally uses narrowband voice (300 Hz to 3800 Hz) because of the prohibitivecost of implementing AMR-WB CODECs in an end-to-end network. Some exceptions tothat exist, such as Oranges recent launch of HD voice in their newly installed 3G network

in Moldava [5]. Mobile operators IMS VoIP

Pros: IMS VoIP solves the challenges of retaining LTE data rates while in voice calls, avoidsexcessive voice call setup delay, provides a at, all-IP network for operational savings, andprovides the basis for new IP-based services. Furthermore, as championed in the recent OneVoice [6] initiative, IMS VoIP for LTE enables the subscriber to continue beneting as theyhave in 2G/3G with voice and texting services global roaming, interoperability and a widerselection of handsets, due to the creation of an industry ecosystem. 3GPPs IMS enables voiceto be blended with other services. An early example of this blending is the GSMA RCS ini-tiative. Alcatel-Lucent also extends IMS service creation to the ACP community, enablingmany developers to create innovative IMS applications. With the all-IP LTE network, the old

circuit network is no longer used; instead, the new all-IP services are readily created, such asvideo communications and social networking interaction, with standards-based global interop-erability. This single, consolidated mobile network enables operational savings. Because it is anall-IP network, wideband audio service is economically deployable for end-to-end IP connectionswhere both parties (LTE, 3G packet switched, or xed broadband) are served by VoIP.


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Cons: Although there are no competitive drawbacks to using IMS (unlike the other two methods)there are challenges. Some operators have already deployed IMS for xed VoIP, Class 5, or mobileservices such as GSMA RCS, and can therefore readily extend their existing network andoperational investment to LTE VoIP. However, for those who have not, they must construct thebusiness and deployment plans which support their rst usage of IMS, including operationalintegration, and providing a method used to ensure ubiquitous voice coverage for areas notserved by LTE.

The ACPs are already providing some initial mobile VoIP services using 3G packet switched networksprior to LTE. While these do not have a signicant market share yet, due to 3Gs limited data bandwidthand QoS controls, these services will be enhanced with the deployment of 3Gs Enhanced High-SpeedPacket Access (eHSPA) because of its improved 3G packet data service. Already we can see the emergenceof ACP-based mobile VoIP in 3G. During the last quarter of 2009, Apple added the Skype 3G VoIP clientto the iPhones application store for AT&T services [7] and Verizon is partnering with Google for theAndroid including Google Voice [8]. This trend is not limited to North America; other examples include:

Hutchison 3s partnership with Skype. Although this uses circuit voice over the radio link,it provides Skype services such as blending and free Skype-to-Skype calling.

Spice Mobile (India) breaks new ground by having an ACP voice application preloaded on

new handsets. This is provided by Nimbuzz, which provides voice calling, texting, messaging,le transfer and integration with social networking sites.

T-Mobile (Europe) allows ACP-based VoIP service for a tariff of9,95 per month.

So why is 3G-based ACP mobile VoIP not more prevalent? There are several factors that are holdingit back. Probably the most important among these are the 3G networks packet-switched QoS.While ne for content downloading and similar activities, it does not provide sufcient bandwidthwith satisfactory QoS for multiple simultaneous users. Furthermore, because many of the mobileVoIP services are from ACPs and not the operator or handset vendors, the user must manuallyadd the VoIP client and set up the service. Finally, operators pricing plans and regulators actionssuch as the European Commissions Roaming Regulation relieves some of the price pressure. Withthe advent of LTE, the status quo will be upset due to the relative ease with which ACPs can offer

mobile VoIP services in LTE. The emergence of successful ACP VoIP services in LTE could have aviral effect in extending these services into 3G packet switched networks.

With IMS VoIP from Alcatel-Lucent, the 3G and LTE operator can respond to and exceed theACP-based VoIP service. Using IMS VoIP as a base application, innovative services are created,whether through GSMA RCS, or by leveraging the Alcatel-Lucent extension of IMS services intothe Application Enablement vision of enabling a partnership between the operators and the ACPs.

3. Comparison

The primary methods for LTE voice are recognized as 3GPP IMS and 3GPP Circuit Switched Fallback(CSFB). Other methods that are non-standard and sometimes focused on a particular operators busi-

ness and technical challenges are characterized by reusing a 2G/3G circuit core served by LTE packetaccess. An operators preferred method will be determined by network capabilities and competitivechallenges. In this section, we briey explore these various methods. Further discussion is availablein the Alcatel-Lucent whitepaper, Options for Providing Voice over LTE. [9]

How do these methods perform in terms of delivering the subscribers expectations for mobile voice?Their performance is summarized in Table 2.


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Table 2. omparing the methods and expectations

3.1IMS

IMS provides VoIP and SMS service in LTE using a fully packet switched network, and is a 3GPPstandard [10] for LTE voice. Unique among the methods, it is the only method that is all-IP. It is theultimate destination for LTE voice for nearly all operators, as reported by several analyst rms, suchas Current Analysis, Stratecast, Yankee Group and Infonetics, and embraced by the One Voiceinitiatives operators: AT&T, Orange, Telefnica, TeliaSonera, Verizon and Vodafone. Furthermore,the One Voice initiative transferred to the GSMA in January 2010, showing the global breadth of

support for IMS VoIP in LTE.

Notably, non-voice IMS services such as GSMA RCS are available in all three methods. Regardlessof how voice service is provided, the RCS services such as presence, content sharing and uniednetwork address book are available for deployment by the operator with all three methods. It is withIMS VoIP that the subscribers RCS experience is enhanced in LTE. Unlike CSFB, with IMS VoIPthe subscriber retains LTEs higher bandwidth during RCS sessions involving voice, such as videosharing, instead of falling back to 3G data rates. A wider selection of handsets plus global roamingis assured with IMS VoIP, unlike VoLGA. Recognizing that GSMA RCS services are becoming tablestakes [18, 19] and are likely to be deployed anyway, the same IMS used for GSMA RCS services canalso be used for IMS VoIP services in LTE.

The primary advantages of IMS voice for LTE are that it Preserves LTEs bandwidth during voice calls while minimizing call setup delay

Assures global interoperability and roaming

Provides the largest possible ecosystem which affects such matters as handset supply andmultivendor interworking

Provides an all-IP network for operational savings and HD voice

Enables full blending of voice with advanced services beyond GSMA RCS

Because voice and other communications services are under IMS control, operators can constructcompetitive services, including partnering with ACPs for services such as blending voice with socialnetworking sites.

Alcatel-Lucent facilitates this through our Applications Enablement vision and the High LeverageNetwork. The value that IMS creates for operators is described by Current Analysis as:

Operators without plans to move to IMS should seriously reconsider that approach and begin toestablish a roadmap for IMS adoption. IMS is a prerequisite for supporting Rich CommunicationSuite (RCS)-based services, and is likely to be a prerequisite soon for delivering universal supple-mental voice services, such as MMTel. It is doubtful that an operator that is unable to support theseuniversal services could remain competitive, similar to the way a mobile operator could not competein todays market if it offered only proprietary SMS services. [18]

SSES EPETTS MS SF STM METHS;

T E, PET ESS

Preserve LTEs data rates during voice calls, plus minimize call setup delay Yes No Yes

Global roaming and interoperability Yes Yes Problematic

Blending Yes Limited Limited

Pricing Yes No No

HD voice Yes No No


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Figure 3 depicts an IMS VoIP deployment for LTE. Details on how this and the other two solutionsare deployed plus their functioning are contained in Options for Providing Voice over LTE [9].

Figure 3. MS oP

This implementation is the only all-IP method. It enables the full spectrum of IMS services, includingGSMA RCS, blending voice with other services including social networking, rich multimedia commu-nications such as video telephony and wideband audio (HD voice). Because the LTE device remains inLTE coverage, the LTEs high bandwidth and QoS are retained, even during voice calls (unlike CSFB).

As for the network deployment, all three solutions have some effects that are similar. All require avoice client on the LTE device. All affect the EPCs Mobility Management Entity (MME). Of coursethe signicant difference with IMS is that the IMS infrastructure must be deployed and integratedinto the operators network and operations. If the operator already has an IMS (such as for xedVoIP, Class 5 or GSMA RCS) this is readily extended to LTE. If not, the operator must undertakethe planning and business justication needed to support the deployment, justied by the additionalrevenues from new services and offset by the operational expense savings of a at, all-IP network.

PCRF

eUTRAN

LTE

SGW MME GGSN

PDN GW MGWMSC server

MGW

GERAN/UTRAN

Terminal: IMS client

IMS voice

Extensibleto 3G packet

switched

Terminal: IMS clientand SRVCC client

SRVCC onlyneeded for 2G/3GCS handoff

Evolved packet core Circuit core; packet core

IMS core and applications

Telephonyserver

HSS

2G/3G

SGSN

SMS center

RCS, others

SRVCCapp server

MGC

Services IMS VoIP, SMS

GSMA RCS

Voice blending

Video telephony

Others

Data retains LTEsbandwidth duringvoice calls

Network change IMS (new

or reuse)

SRVCC if 2G/3Gcircuit voiceneeded

MME softwareand interfaces

eUTRANsoftware andinterfaces plusVoIP QoS

IMS client

IMS core


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As for roaming and handoff between LTE and legacy mobiles 2G/3G circuit switched voice, SRVCCis needed if the operator does not have complete LTE coverage or is not able to plug the gaps incoverage with adequate 3G packet switched (3G PS) coverage, or when roaming globally. TheeUTRAN must include the enhancements to serve VoIP, such as robust header compression andsemi-persistent scheduling.

3.2CSFB

Circuit Switched Fallback (CSFB) provides voice service for LTE by reusing the existing 2G/3Gnetwork and is a 3GPP standard [10] for providing voice for LTE (see Figure 4). It is an interimmethod preferred by most operators who do not yet have an IMS infrastructure for their initial LTElaunch. The 2G/3G network is reused so that the initial LTE deployment focuses solely on providingan improved mobile data service, such as LTE as a data-overlay. The mobile devices are normallyserved by LTE for the data services. During voice calls, the mobile device reverts or falls back to2G/3G service, suspending LTE data service; and due to the limitation of only one active radio ata time in the handset, falls back to either 3G data rates or, in the case of of fallback to 2G, suspendsthe data service altogether due to 2Gs lack of simultaneous voice and data. Hence voice serviceis readily provided for LTE, though with service limitations; CSFB provides complete and transpar-ent service to current 2G/3G services, though without supporting much further IP communicationservices beyond GSMA RCS.

The primary advantages of CSFB voice for LTE are that it is readily deployable for those operatorswho have not already deployed IMS, and that it provides complete feature transparency to current2G/3G services, including global roaming and interoperability.

Figure 4. SF voice

eUTRAN

LTE

SGW MME GGSN


GERAN/UTRAN

Terminal: CSFB client

Legacyvoice

Terminal: CSFB client


2G/3G

SGSN

Services

2G/3G voice, SMS

GSMA RCS

Others

Data reverts to2G/3G serviceduring voice calls

Network change

MSC softwareand interfaces


CSFB client

Core network applications

SMS center HSS


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By relying on the existing 2G/3G circuit core, the CSFB method assures the ready availability oflegacy mobile voice services. If IMS is deployed for non-voice services, services such as GSMA RCSwill be available also. However, this method suffers from two notable service drawbacks: during avoice call, the mobile devices data service is de-rated from LTE back to 2G/3G data rates and QoSbecause there are two radios in the device, but only one (LTE or 2G/3G) may be active. The seconddrawback is the increased call setup time that is required for the device to switch from LTE to 2G/3Gservice, which ranges from approximately 1.5 seconds for 3G to 2.5 seconds for 2G, with perhaps a

further 3-second delay for some calls if the LTE and 2G/3G coverage areas are not precisely aligned.

As for the network deployment, CSFB does avoid IMS VoIPs deployment and integration. However,CSFB also requires clients on the devices and upgrades to the mobility management entity (MME),plus the eUTRAN (though not as extensive because it need not serve VoIPs QoS requirements). Akey consideration is that all Mobile Switching Centers (MSCs) in the serving area must be upgradedwith a software release in order to accommodate interworking of the CSFB calls between LTE and2G/3G. Those operators who deploy and integrate IMS for GSMA RCS service are well positionedto extend that same IMS to provide VoIP in LTE, allowing them to bypass CSFB.

3.3Custommethods(circuitcore,LTEpacketaccess)

These methods provide voice service in LTE by reusing the existing circuit 2G/3G MSC, with voice

provided as VoIP over the LTE radio link and packet core; however, it is interworked to the circuitMSC either using an interworking function or by adding a VoIP telephony server to the MSC. Thesemethods are not 3GPP standards. One such example is VoLGA, whose specication is providedby the VoLGA Forum [11], and is an interim method selected by very few operators because of theneeds of their networks and business environments. It is particularly useful to operators who havea predominantly 2G network, because it enables simultaneous voice and data services they cannotoffer without LTE.

Similar to CSFB, these custom methods, illustrated in Figure 5, reuse the existing 2G/3G network,but the difference is that voice is carried as VoIP over the radio links; and so the LTE device canuse only one radio for both voice and data services, remaining entirely on LTE radio access insteadof falling back to 2G/3G radios. This means LTEs high data rates are always available, even duringvoice calls. Hence, these methods provide voice service for LTE, but with limitations on globalroaming and interoperability, and a limited selection of handsets because of the lack of a signicantsubscriber base when compared to IMS VoIP and CSFB.

Although VoIP is used over the radio link, voice is converted to circuit in the middle. Hence thebenets that subscribers of IMS VoIP and ACP-based voice obtain with all-IP are not available. Forexample, wideband audio and services such as video telephony that rely on an end-to-end IP pathwill not work.

As for the network deployment, these custom methods defer IMS deployment and integration, butlike CSFB, require the deployment of new network elements or signicant upgrades to existing net-work elements that are done only to provide legacy voice service. Similar to IMS VoIP and CSFB, thecustom methods also require a voice client for the device, but are further challenged by the relativelysmall subscriber base that these methods will attract, which limits the ability of handset manufactur-ers to provide a wide selection of handsets. Also similar with the other two solutions, they may requireadditional capabilities in the MME and eUTRAN. Similar to IMS VoIP, the eUTRAN must supportVoIP. Those operators who deploy and integrate IMS for GSMA RCS service are well positioned toextend that same IMS to provide VoIP in LTE, allowing them to bypass these methods.


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Figure 5. ustom methods: ircuit core, packet access (oLG used as an example)

3.4SummarizingthethreemethodsandrecommendationsIMS provides the superior method for LTE voice and SMS because of what it enables:

The widest ecosystem, based on One Voice, assuring the subscribers global roaming andinteroperability and the widest selection of LTE devices

Competitive services, such as full blending of voice with other services and wideband audio

Partnering with the ACPs for the mid- and long-tail of applications

All-IP network operational savings

Individual operators network environments and competitive business situations may cause themto consider other methods. Table 3 summarizes the pros and cons of the methods; these factorsand impacts on network deployment are further discussed in Options for Providing Voice over

LTE and Their Impact on the GSM/UMTS Network [9].

eUTRAN

LTE

SGW MME GGSNSecurityGW


GERAN/UTRAN

Terminal: VoLGA client

Legacyvoice

Terminal: VoLGA client


2G/3G

AAA server VANC

SGSN

Services

2G/3G voice, SMS

GSMA RCS

Others

Data retains LTEsbandwidth duringvoice calls

Network change

VANC, AAAserver, securitygateway


eUTRANsoftware andinterfaces

plus VoIP QoS VOLGA client

Core network applications

SMS center HSS


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Table 3. omparison of impacts on the network

4. The Path to LTE and the One Voice Initiative

Given these justications for using IMS VoIP and SMS in LTE, the popular question is why arentmore operators implementing it earlier? Several factors drive this behavior.

First is the operators urgent need to improve mobile data services, in terms of the bandwidth for anindividual subscriber and the total bandwidth available to aggregate simultaneous users in the cellssector. Early efforts are focused on LTE as a data overlay, followed by voice and other services.

Second is the availability of the end-to-end ecosystem. Most apparent was the question of when LTEdevices such as smartphones and mass market phones with IMS voice clients would be available. Thereadiness of the network vendors and global roaming and interoperability were also critical. Thesereasons are why operators and vendors created One Voice: to foster a solution and promote the eco-systems availability.

The One Voice initiative uses the 3GPPs currently available, open standards and denes the minimummandatory set of functionality and options for interoperable IMS-based voice and SMS services in LTE.No new standards were created. Instead, this alignment on a common set of requirements enables theoperators, handset vendors and network vendors to create and deploy services more quickly. This avoidsthe fragmentation of the global mobile network, which would risk the ability for global roaming andinteroperability that people today enjoy with the 2G/3G networks.

One Voice created a technical prole covering the aspects that touch upon IMS-based VoIP andSMS across the LTE devices, eUTRAN, EPC and IMS. It aids the timely establishment of an industryecosystem across handset manufacturers, network equipment vendors and service providers.

IMS enables many sophisticated services based on many specications, often with multiple options

for enabling the same function. Not all of these many standards are necessary in order to providethe initial IMS VoIP and SMS in LTE service. Therefore, the One Voice initiative denes a common,recommended feature set and selects a recommended option when multiple options exist.

The One Voice technical prole is recommended but not mandatory. Anyone is free to use or notuse it; and anyone is free to build further services on top of it. The technical prole provides costand time-to-market advantages by establishing an industry ecosystem such that:

Handset manufacturers and software client vendors can provide a wider variety of LTE handsetsequipped with IMS VoIP and SMS by building toward a larger, well dened market

Network equipment manufacturers can build their systems to a common target, reducing theneed for always applying customization, unless required by an operator

SEE EPLyMET FTS MS oP SF STM METHS

(T E, PET

ESS)

Converged service control across fixed and mobile, voice, RCS and others? Yes No No

3GPP standards

Roaming, global interoperability

Ecosystem of network and handset vendors

Yes Yes No

Flat all-IP operational benefits Yes No No

Avoid LTE network upgrade for voice with LTE? No No No

Avoid 2G/3G MSC network upgrade for voice with LTE? Yes (VoIP in LTE and 3G PS) No Varies

Relative initial CAPEX Most Least Some


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Service providers can more readily perform interoperability testing (IOT) across handsets,network vendors and between networks

Subscribers obtain the benets of global roaming and interoperability, as they do today with2G and 3G services

The One Voice initiative transferred to the GSMA during January 2010.

5. Alcatel-Lucent leadership

LTE is a tremendous opportunity and a tremendous undertaking full of challenges that span tech-nology, business and planning. The Alcatel-Lucent value to operators is that we offer LTE, IMS andprofessional services.

5.1Alcatel-Lucentend-to-endLTE

Alcatel-Lucent has established an early leadership position in LTE, selected by Verizon Wireless one of the worlds rst movers in LTE as a key supplier for the operators planned LTE deployment.Alcatel-Lucent was chosen as a supplier for all areas of the operators LTE network radio access,IMS and Evolved Packet Core (EPC). [13]

Alcatel-Lucent is engaged in many LTE trials around the world involving LTE Time DivisionDuplex (TDD) (known commonly as TD-LTE) and LTE Frequency Division Duplex (FDD).

Alcatel-Lucent is bringing its leadership in broadband service delivery to drive the transition toall-IP wireless broadband, with LTE as a key step in this transition. LTE is therefore a strategicinvestment area for the company.

Alcatel-Lucent is fully committed to providing its customers with an industry leading end-to-endLTE solution. The Alcatel-Lucent Ultimate Wireless Broadband end-to-end solution [14] enableswireless and converged service providers to advance their business, operational model and end-to-endnetwork. It provides an end-to-end LTE network with a full set of radio, packet core, mobile backhaul

and IMS products, transformation and integration services, plus the ng Connect open ecosystemof devices, content and application partners. This solution leverages the Alcatel-Lucent broadbandand IP market leadership to deliver unprecedented scalability, quality of experience, business agilityand controlled network costs.

Alcatel-Lucent recently announced that FT/Orange has selected Alcatel-Lucent for an LTE eldtrial in both FDD and TDD modes. This technical trial, which is attempting to gain full assess-ment of the end-to-end performance of LTE, will take place in the southern region of Paris, usingthe Alcatel-Lucent e-nodeBs and evolved packet core. Alcatel-Lucent was also invited to participatein LTE trials by Telefnica and Etisalat [15] and Bouygues [16]. To date, the Alcatel-Lucent LTEsolution has been selected by operators for trials around the globe, including both lab and eld trialswith Tier 1 operators in North America, Europe, the Middle East and Asia.

5.2Alcatel-Lucentend-to-endIMS

Service providers are looking for ways to minimize expenses while optimizing value. At the sametime, end-user demand is increasing for innovative services and anytime access from any location,often available already in the form of Internet-based applications. It is this demand for new servicesand the threat of over-the-top competition that is driving network transformation to IMS.

Different network transformation strategies exist, many service providers are starting with enhancedservices such as the GSMA RCS services (such as presence, address book, messaging, le and contentsharing). Other service providers that offer wireline services are starting with consumer VoIP or migratingoff of their aging Class-5 networks. The Alcatel-Lucent End-to-End IMS solution [17] (see Figure 6) allowsservice providers to start with any combination of services, adding new ones as the market warrants.


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Alcatel-Lucent is a clear leader in the IMS space, holding more than 45 end-to-end references including AT&T, the worlds largest live IMS deployment. Alcatel-Lucent IMS spans the applica-tions that service providers need, from xed consumer VoIP (AT&T), xed business VoIP (Belgacom),Class-5 Migration (Enitel) and Enhanced Communications Services (AT&T Video Share) to theRich Communication Suite (Bouygues Telecom).

The Alcatel-Lucent Services Group has been paramount in the planning, preparation and execution

of these deployments. They have also helped many operators transform networks beyond an IMSscenario. Therefore, carriers can benet from the breadth and depth of this experience in all phasesof a network transformation to IMS. This spans product readiness; planning; program management;large network operation, growth, and maintenance; and more. The eld-proven capability on boththe product and services sides benets carriers looking to transform their network with minimal risk.

Service providers can select Alcatel-Lucent as their IMS provider with condence, knowing our IMShas the reliability, exibility, scalability and applications support to carry them well into the future.

A leader in next-generation networks (NGN) and IMS, Alcatel-Lucent has deployed IP/NGN productsin more than 275 xed and mobile networks, and we are involved in more than 45 full IMS networktransformation projects.

Figure 6. lcatel-Lucent End-to-End MS solution

Convergedwireline access

Convergedmetro and aggregation

Convergededge

Converged service-aware network management

Convergedbackbone

ConvergedRAN

Convergedservice control

Common session control across fixed andwireless providing seamless service accessand mobility

From voice to rich multimedia communications enabling seamless service interworking

across service provider networks

Rapid, economical service innovationwith massive application scaling

Consumer and businessVoIP/enhanced

communications

POTS/ISDN

3G RCS, LTE,femto, WiMAX

and more

TDM GPON/DSL Mobile

Alcatel-Lucent end-to-end IMS

Alcatel-Lucent IMS powers competitive multimedia communication services


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6. Conclusion

In this paper we examined the methods for providing voice and SMS service with LTE: IMS, CircuitSwitched Fallback, plus non-standard custom methods characterized by a 2G/3G circuit core, servedby an LTE packet access. The three options competitive dynamics and network effects were assessed,leading to the conclusion that IMS provides the superior service because it best enables the operatorto create innovative services, realize all-IP operational savings, and makes it possible to collaborate

with ACPs.

By understanding the benets that each option provides, and understanding the transformationthat is necessary as described in Options for Providing Voice over LTE and Their Impact on theGSM/UMTS Network [9], operators can make better informed decisions about how and whento implement voice in LTE.

By virtue of Alcatel-Lucent end-to-end service offerings, we are a contributor to all three options.With our experienced employees and proven track record in wireless and IMS projects, we areuniquely positioned to aid your transformation to LTE. With the most comprehensive portfolio oftelecommunications products and services in the industry, Alcatel-Lucent has the expertise, products,services and global reach that have won us a leadership role in the LTE evolution. We provide:

A global LTE offer with service continuity and integration for 2G/3G networks, leveragingour unique expertise in 2G/3G standards, LTE trial leadership with major operators, andactive participation in leading LTE organizations and forums

An unmatched end-to-end LTE solution that leverages our market leadership in next-generationIP transformation and service delivery, recognized expertise in packet transport, industry leadershipin IMS service delivery platforms, next-generation wireless access technologies and Alcatel-LucentBell Labs innovations, such as self-optimized networks, next-generation multiple-input multiple-output (MIMO)

A broad and open ecosystem of compelling devices and applications

7. ContactsFor more information on Alcatel-Lucent IMS in LTE solutions, please visit www.alcatel-lucent.comor contact your Customer Team representative.

You can also contact Alcatel-Lucent Marketing or Public Relations:

EdElkin:IMSMarketing

[email protected]+1 630 224 8491

WimVanDaele:PublicRelations

[email protected]+32 3 2404601


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8. Acronyms

2G Second Generation

3G Third Generation

3GPP Third Generation Partnership Project

3G PS 3G packet switched

ACP Application and Content Provider

AMR Adaptive Multi-Rate

AMR-WB AMR-Wideband

CAPEX capital expenditures

CDN Content Delivery Network

CODEC coder-decoder

CSFB Circuit Switched Fallback

DSL digital subscriber line

eHSPA Enhanced High-Speed Packet Access

EPC Evolved Packet Core

eUTRAN Enhanced UMTS Terrestrial Radio Access Network

FDD Frequency Division Duplex

GSM Global System for Mobile telecommunicationsGSMA GSM Association

HD voice high-denition voice

IMS IP Multimedia Subsystem

IOT interoperability testing

LTE Long Term Evolution

MIMO multiple input-multiple output

MME mobility management entity

MSC Mobile Switching Center

NGN next-generation network

QCI Quality Class Identier

QoS Quality of Service

RCS Rich Communication Suite

SMS Short Message Service

TDD Time Division Duplex

UE user equipment

UMTS Universal Mobile Telephone System

VANC VoLGA Access Network Controller

VoIP Voice over IP

VoLGA Voice over LTE Generic Access

9. References

[1] Forecast: Mobile Services, 2004-2013, Gartner, June to September 2009

[2] North America Mobile Data Forecast, Pyramid, December 2009

[3] The LTE Network Architecture: A comprehensive tutorial, Alcatel-Lucent, CPG0599090904(12), December 2009, http://www.alcatel-lucent.com/wps/ocumentStreamerServlet?LMSG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=White_Papers/CPG0599090904_LTE_Network_Architecture_EN_StraWhitePaper.pdf

[4] Dataquest Insight: LTE Market Update, Gartner, September 25, 2009

[5] Orange launches worlds rst high-denition voice service for mobile phones in Moldava,September 10, 2009, http://www.orange.com/en_EN/press/press_releases/cp090910en.jsp


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[6] Global Telecom Companies Announce a Standards Based Solution for Voice and SMSServices over LTE, Verizon et al, http://news.vzw.com/news/2009/11/pr2009-11-03a.html

[7] AT&T Extends VoIP to 3G Network for iPhone, AT&T, October 6, 2009,http://www.att.com/gen/press-room?pid=4800&cdvn=news&newsarticleid=27207

[8] Verizon opens door to Android, Google Voice, Fierce Wireless, October 6, 2009,http://www.ercewireless.com/ctialive/story/verizon-opens-door-android-googlevoice/2009-10-06

[9] Options for Providing Voice over LTE and Their Impact on the GSM/UMTS Network,Alcatel-Lucent, CPG1649091001 (11), August 2009, http://www.alcatel-lucent.com/wps/DocumentStreamerServlet?LMSG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=White_Papers/CPG1649091001_Options_for_Providing_Voice_as_LTE_is_Introduced_EN_StraWhitePaper.pdf

[10] 3GPP (http://www.3gpp.org/Specication-Numbering)

23.216: Single Radio Voice Call Continuity (SRVCC)

23.221: Architectural requirements

23.228: IP Multimedia Subsystem (IMS)

23.237: IMS Service Continuity (ISC)

23.272: CS Fallback

23.292: IMS Centralized Services (ICS)

23.401: GPRS Enhancements for Evolved Universal Terrestrial Radio Access Network(E-UTRAN) Access

23.879: Study on Circuit (CS) Domain Services over Evolved packet Switched (PS) Access

[11] VoLGA Forum. http://www.volga-forum.com/

[12] GSMA Rich Communication Suite.http://www.gsmworld.com/our-work/mobile_lifestyle/rcs/gsma_rcs_project.htm

[13] Verizon LTE press release, February 18, 2009. http://all.alcatel-lucent.com/wps/portal/!ut/p/kcxml/04_Sj9SPykssy0xPLMnMz0vM0Y_QjzKLt4w3czLXL8h2VAQA9ypdMQ!!?LMSG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=News_Releases_2009/

News_Article_001451.xml[14] Alcatel-Lucent Ultimate Wireless Broadband End to End LTE Solution,

http://www.alcatel-lucent.com/wps/portal/!ut/p/kcxml/04_Sj9SPykssy0xPLMnMz0vM0Y_QjzKLd4w3dnTUL8h2VAQAvhWwcA!!?LMSG_CABINET=Solution_Product_Catalog&LMSG_CONTENT_FILE=Solutions/Solution2_Detail_000119.xml

[15] Telefnica, Etisalat, FT/Orange, NTT DoCoMo LTE press release, November 19, 2009.http://all.alcatel-lucent.com/wps/portal/!ut/p/kcxml/04_Sj9SPykssy0xPLMnMz0vM0Y_QjzKLt4w3czLXL8h2VAQA9ypdMQ!!?LMSG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=News_Releases_2009/News_Article_001869.xml

[16] Bouygues LTE press release, December 8, 2009. http://all.alcatel-lucent.com/wps/portal/!ut/p/kcxml/04_Sj9SPykssy0xPLMnMz0vM0Y_QjzKLt4w3czLXL8h2VAQA9ypdMQ!!?LM

SG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=News_Releases_2009/News_Article_001890.xml

[17] Alcatel-Lucent End to End IMS Solution, http://www.alcatel-lucent.com/wps/portal/!ut/p/kcxml/04_Sj9SPykssy0xPLMnMz0vM0Y_QjzKLd4w3dnTUL8h2VAQAvhWwcA!!?LMSG_CABINET=Solution_Product_Catalog&LMSG_CONTENT_FILE=Solutions/Solution2_Detail_000044.xml

[18] One Voice Initiative: Clearing a Path for IMS-based Voice over LTE, Joe McGarvey, CurrentAnalysis, November 5, 2009

[19] RCS Market Outlook, Diane Myers, Infonetics, May 5, 2009


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www.alcatel-lucent.com Alcatel, Lucent, Alcatel-Lucent and the Alcatel-Lucent logoare trademarks of Alcatel-Lucent. All other trademarks are the property of their respective owners.The information presented is subject to change without notice. Alcatel-Lucent assumes no responsibilityfor inaccuracies contained herein. Copyright 2010 Alcatel-Lucent. All rights reserved.CPG4688100102 (02)

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