Feb2010 ims vo_ip_3g_lte_strategic_swp

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 con fusion

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 services

that include partnering with application and content providers, realize the benefits of

LTE’s all-IP network, and preserve global roaming and interoperability that we have

achieved in today’s 2G/3G networks.

What’s Next for Mobile Voice? The case for IMS VoIP in 3G/LTE

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 voice

4 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

What’s Next for Mobile Voice? | Strategic White Paper 1

1. Introduction

LTE will solve today’s pressing needs for increased mobile data bandwidth. The popularity of devices such as the iPhone®, Android™ and BlackBerry®, and services such as video and social networking are rapidly outpacing 3G’s ability to effectively deliver services, causing some operators to reconsider pricing plans for mobile data. Instead of reducing service usage, most operators prefer to increase subscribers’ usage of mobile data by deploying LTE.

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

LTE is designed to be a flat, all-IP network, from the handset, through the radio access, across the packet core and into the services layer. The all-IP network provides operators with economic benefits from both the simplified network’s operations (lower costs) and the new services created with IP’s inherent flexibility and utility (improved revenues). In such an all-IP network, voice is provided as Voice over IP (VoIP). However, some operators and vendors are considering interim methods so they can focus on LTE’s initial service as a data-only overlay.

There are several methods for LTE to deliver voice and short message service (SMS), such as the two 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 packet access. Except for IMS VoIP, all methods rely heavily on reusing the existing 2G/3G MSC. Reusing the exist ing 2G/3G MSC provides benefits such as complete feature transparency plus leveraging the MSC’s already established integration into the Operational Support Systems and Business Support Systems (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 for CSFB causes the LTE data session, during voice calls, to fall back to 3G’s lower data rates, or is even suspended 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, reduce the 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 capabilities enabled for the subscriber; these factors are evaluated in this paper. The essential LTE voice question that operators ask themselves is which method should they use initially, to provide LTE voice? While IMS VoIP is regarded as the desired end state, should and can they avoid investments in an interim method by proceeding directly to IMS VoIP?

This paper examines the options for providing voice with LTE; and it builds the case for starting with or rapidly moving to IMS VoIP as the best method to help operators realize LTE’s potential for innova-tive and all-IP operational savings, preserve LTE’s bandwidth during voice calls, minimize call setup delays, assure global roaming and interoperability, and avoid the loss of lucrative voice services to third-party ACPs who can readily provide VoIP service in LTE, much as they have in fixed 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 with their friends, families and colleagues. People are eager to connect with each other and are willing to 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 the primary revenue contributor for the next several years. Add into this that approximately half of data revenues come from texting (SMS) [2] and it is clear that the contributions of voice and texting are fundamental to operators’ continued commercial success.

What’s 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 predominant sources of mobile operators’ revenues? No, because data services are increasingly popular. The number of data subscribers and their data usage continues to grow rapidly. This behavior is fueled by the proliferation of 3G data networks, the widespread availability of multimedia and smartphones, the availability of content and social networking sites using mobile devices, and affordable mobile data services. However, voice and SMS are fundamental services in the operator’s portfolio because of their significant revenues plus voice’s role as the base application on which to build further services, such as GSMA RCS, high-definition voice and blending with social networking sites. The realization of enhanced voice relies upon VoIP, not circuit switched voice. It is with IMS and VoIP that the operators can compete and partner with the ACPs.

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

In contrast to 3G networks’ usage of circuit-switched voice and SMS, plus packet-switched data, an LTE network is all-IP. All traffic in an LTE system is carried as IP, providing seamless, high-speed connections between a handset or user equipment (UE), and various packet data networks, such as the Internet, IMS, and Content Delivery Networks (CDNs). The various IP bearers in the LTE system are assigned specific QoS Class Identifiers (QCIs) that correspond to specific treatment levels for connection types, priority, delay budgets and packet error loss rates. A single handset or UE may have 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 efficient and therefore more economical network for mobile data, it also provides enhanced performance for the people who use its services. Gartner depicts LTE as being well into a broadband-like experience zone, providing data service that was previously only available on fixed broadband [4].


Figure 2. LTE network architecture

2.2Subscribers’expectationsforLTEmobilevoiceWith LTE providing a broadband-like experience, how does this affect the immense voice revenues and profits that mobile operators today reap from 2G and 3G services? The erosion in fixed operators’ revenues that began approximately ten years ago stemmed from technology competition for their core voice services. This technology competition came about from both mobile substitution for fixed voice services plus innovative voice over IP (VoIP) services from ACPs such as Vonage® and Skype™. Both of these were so attractive to consumers and enterprises that they changed a century of past practices and shifted to mobile phones and fixed VoIP services that often came with more dropped calls, poor mobile voice quality and extra steps needed in order to place a call. But the new 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 to people? They seek services that:

• Providehigh-speedInternetaccess: to preserve LTE’s data rates during voice calls

• Blendmyvoicewithotherservices: such as presence, messaging and social networking

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

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

Voice is fundamentally human, yet the mobile voice experience has not made much improvement over 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 created by 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 to some 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 fixed broadband.

When mobile operators launch the initial LTE data-only services, such as a laptop with an LTE dongle, there is no guarantee that the LTE-enabled laptop will be used only for data services. An ACP-provided VoIP service can be readily extended to the laptop. And while the ACP’s VoIP service might suffer from some drawbacks, such as being delivered using best effort data instead of conversational voice, it will appeal to some key subscribers, just as it has in fixed broadband. Hence, the initial subscribers to an LTE data-only service could very well be the start of a shift of voice usage 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 SGii IP services:IMS


this shift are those who are most valuable to the mobile operators — volume callers, global callers and young millennials who bring with them the habits of fixed broadband (messaging, social networking, and “free” is the new price).

Just as surely as fixed broadband created a new market of alternative voice providers, so too will mobile 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?

2.3MobilevoicecompetitionTo answer these questions, it is also necessary to consider capabilities that we take for granted today. A 2G/3G mobile service allows a person to call anyone on the planet who has fixed or mobile service — 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 access these same 2G/3G voice and texting services in another network’s service area or when they are in another country. They retain their telephone number while roaming so that even while on vacation or working elsewhere, their social circle still calls the same number. Given these considerations, let’s examine the various options for LTE services in more detail. A summary is shown in Table 1, and the points are discussed further in the subsequent text and in Section 3.

Table 1. Services comparison

• ACP’s mobile VoIP

¬ Pros: The ACP’s mobile VoIP service will resemble their fixed 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 voice service is priced relatively low or even free if supported by some alternative revenue source such as advertising or fees on advanced services. And wideband audio is possible between two users served by an all-IP path. The typical circuit mobile voice service, using 3GPP’s Adaptive Multi-Rate coder-decoder (AMR CODEC) ranges from 300 to 3400 Hz. In contrast, wideband CODECs such as 3GPP’s AMR-Wideband (AMR-WB) extend the frequency range to 50 to 7000 Hz, and Skype’s SILK CODEC further extends the upper frequency to 12,000 Hz.

LTE-baSEd SErvicES acP’S MobiLE voiP MobiLE oPEraTor’S cSFb MobiLE oPEraTor’S iMS voiP

Preserve LTE’s data rates during voice calls

Blending GSMA RCS begins to blend voice

Pricing

Wideband voice

Roaming Might be prohibitive due to data roaming tariffs and perhaps the lack of conversational voice QCI

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

Handset variety and supply Limited – requires laptop or smartphone and software client installation


¬ Cons: Although technically an ACP’s mobile VoIP subscriber could roam anywhere there is a mobile data connection, the price may be prohibitive due to relatively high-priced data roaming tariffs. While LTE solves the packet bandwidth problem, if the ACP mobile VoIP user leaves LTE coverage and encounters either 2G service or over-occupied 3G packet services, they will not be able to use their packet-based service. Currently, the ACP-based VoIP services have limited interoperability, requiring the voice calls to transit the circuit PSTN, losing many of its 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 which a soft client can be installed by the user; this expense and limited selection appeals to a narrower audience.

• Mobile operators’ CSFB

¬ Pros: With a well developed ecosystem, the subscriber benefits from excellent roaming, global interoperability and an extensive selection of handsets. Techniques exist for the LTE voice service to be served by the existing 2G/3G circuit voice network, using 3GPP’s Circuit Switched Fallback (CSFB).

¬ Cons: During a voice call the LTE data service is suspended. Along with the voice, the data also falls back to 3G which has a lower data rate. If the call falls back to 2G, the data service is suspended altogether due to a lack of simultaneous voice and data in 2G. Starting from LTE and falling back to 2G/3G, the voice call’s setup delay adds from approximately 1.5 seconds for 3G to 2.5 seconds for 2G, and adds a further 3 seconds for some calls if the LTE and 2G/3G coverage areas were not precisely engineered to match. The standard 2G/3G circuit voice service is siloed from other services, in that it is not blended with messaging, presence or social networking sites. The Global System for Mobile Communications Association Rich Communication Suite (GSMA RCS [12]) initiative uses IMS to overcome these limits in 3G to create enhanced services using circuit voice, but aside from this the 2G/3G network does not 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 high priced and generally uses narrowband voice (300 Hz to 3800 Hz) because of the prohibitive cost of implementing AMR-WB CODECs in an end-to-end network. Some exceptions to that exist, such as Orange’s 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, avoids excessive voice call setup delay, provides a flat, all-IP network for operational savings, and provides the basis for new IP-based services. Furthermore, as championed in the recent One Voice [6] initiative, IMS VoIP for LTE enables the subscriber to continue benefiting as they have in 2G/3G with voice and texting services’ global roaming, interoperability and a wider selection of handsets, due to the creation of an industry ecosystem. 3GPP’s IMS enables voice to 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, enabling many 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 as video communications and social networking interaction, with standards-based global interop-erability. This single, consolidated mobile network enables operational savings. Because it is an all-IP network, wideband audio service is economically deployable for end-to-end IP connections where both parties (LTE, 3G packet switched, or fixed broadband) are served by VoIP.


¬ 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 fixed VoIP, Class 5, or mobile services such as GSMA RCS, and can therefore readily extend their existing network and operational investment to LTE VoIP. However, for those who have not, they must construct the business and deployment plans which support their first usage of IMS, including operational integration, and providing a method used to ensure ubiquitous voice coverage for areas not served by LTE.

The ACPs are already providing some initial mobile VoIP services using 3G packet switched networks prior to LTE. While these do not have a significant market share yet, due to 3G’s limited data bandwidth and QoS controls, these services will be enhanced with the deployment of 3G’s Enhanced High-Speed Packet Access (eHSPA) because of its improved 3G packet data service. Already we can see the emergence of ACP-based mobile VoIP in 3G. During the last quarter of 2009, Apple® added the Skype 3G VoIP client to the iPhone’s application store for AT&T™ services [7] and Verizon is partnering with Google for the Android including Google Voice [8]. This trend is not limited to North America; other examples include:

• Hutchison 3’s 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, file transfer and integration with social networking sites.

• T-Mobile (Europe) allows ACP-based VoIP service for a tariff of €9,95 per month.

So why is 3G-based ACP mobile VoIP not more prevalent? There are several factors that are holding it back. Probably the most important among these are the 3G network’s packet-switched QoS. While fine for content downloading and similar activities, it does not provide sufficient bandwidth with satisfactory QoS for multiple simultaneous users. Furthermore, because many of the mobile VoIP services are from ACPs and not the operator or handset vendors, the user must manually add the VoIP client and set up the service. Finally, operators’ pricing plans and regulators’ actions such as the European Commission’s Roaming Regulation relieves some of the price pressure. With the 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 a viral 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 the ACP-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 into the 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 operator’s busi-ness and technical challenges are characterized by reusing a 2G/3G circuit core served by LTE packet access. An operator’s preferred method will be determined by network capabilities and competitive challenges. In this section, we briefly explore these various methods. Further discussion is available in the Alcatel-Lucent whitepaper, “Options for Providing Voice over LTE.” [9]

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


Table 2. comparing the methods and expectations

3.1IMSIMS provides VoIP and SMS service in LTE using a fully packet switched network, and is a 3GPP standard [10] for LTE voice. Unique among the methods, it is the only method that is all-IP. It is the ultimate destination for LTE voice for nearly all operators, as reported by several analyst firms, such as Current Analysis, Stratecast, Yankee Group and Infonetics, and embraced by the “One Voice” initiative’s operators: AT&T, Orange, Telefónica, 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. Regardless of how voice service is provided, the RCS services such as presence, content sharing and unified network address book are available for deployment by the operator with all three methods. It is with IMS VoIP that the subscriber’s RCS experience is enhanced in LTE. Unlike CSFB, with IMS VoIP the subscriber retains LTE’s higher bandwidth during RCS sessions involving voice, such as video sharing, instead of falling back to 3G data rates. A wider selection of handsets plus global roaming is assured with IMS VoIP, unlike VoLGA. Recognizing that GSMA RCS services are becoming table stakes [18, 19] and are likely to be deployed anyway, the same IMS used for GSMA RCS services can also be used for IMS VoIP services in LTE.

The primary advantages of IMS voice for LTE are that it

• Preserves LTE’s 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 and multivendor 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 construct competitive services, including partnering with ACPs for services such as blending voice with social networking sites.

Alcatel-Lucent facilitates this through our Applications Enablement vision and the High Leverage Network™. 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 to establish a roadmap for IMS adoption. IMS is a prerequisite for supporting Rich Communication Suite (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 these universal services could remain competitive, similar to the way a mobile operator could not compete in today’s market if it offered only proprietary SMS services.” [18]

SubScribErS’ ExPEcTaTionS iMS cSFb cuSToM METHodS; circuiT corE, PackET accESS

Preserve LTE’s 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


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

Figure 3. iMS voiP

This implementation is the only all-IP method. It enables the full spectrum of IMS services, including GSMA 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 in LTE coverage, the LTE’s 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 a voice client on the LTE device. All affect the EPC’s Mobility Management Entity (MME). Of course the significant difference with IMS is that the IMS infrastructure must be deployed and integrated into the operator’s network and operations. If the operator already has an IMS (such as for fixed VoIP, Class 5 or GSMA RCS) this is readily extended to LTE. If not, the operator must undertake the planning and business justification needed to support the deployment, justified by the additional revenues from new services and offset by the operational expense savings of a flat, 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 LTE’sbandwidth duringvoice calls

Network change• IMS (new or reuse)• SRVCC if 2G/3G circuit voice needed• MME software and interfaces• eUTRAN software and interfaces plus VoIP QoS• IMS client

IMS core


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

3.2CSFBCircuit Switched Fallback (CSFB) provides voice service for LTE by reusing the existing 2G/3G network and is a 3GPP standard [10] for providing voice for LTE (see Figure 4). It is an interim method preferred by most operators who do not yet have an IMS infrastructure for their initial LTE launch. The 2G/3G network is reused so that the initial LTE deployment focuses solely on providing an improved mobile data service, such as LTE as a data-overlay. The mobile devices are normally served by LTE for the data services. During voice calls, the mobile device reverts or falls back to 2G/3G service, suspending LTE data service; and due to the limitation of only one active radio at a time in the handset, falls back to either 3G data rates or, in the case of of fallback to 2G, suspends the data service altogether due to 2G’s lack of simultaneous voice and data. Hence voice service is 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 communication services beyond GSMA RCS.

The primary advantages of CSFB voice for LTE are that it is readily deployable for those operators who have not already deployed IMS, and that it provides complete feature transparency to current 2G/3G services, including global roaming and interoperability.

Figure 4. cSFb 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 software and interfaces• MME software and interfaces• CSFB client

Core network applications

SMS center HSS


By relying on the existing 2G/3G circuit core, the CSFB method assures the ready availability of legacy mobile voice services. If IMS is deployed for non-voice services, services such as GSMA RCS will be available also. However, this method suffers from two notable service drawbacks: during a voice call, the mobile device’s data service is de-rated from LTE back to 2G/3G data rates and QoS because there are two radios in the device, but only one (LTE or 2G/3G) may be active. The second drawback is the increased call setup time that is required for the device to switch from LTE to 2G/3G service, 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 VoIP’s 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 VoIP’s QoS requirements). A key consideration is that all Mobile Switching Centers (MSCs) in the serving area must be upgraded with a software release in order to accommodate interworking of the CSFB calls between LTE and 2G/3G. Those operators who deploy and integrate IMS for GSMA RCS service are well positioned to 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 circuit MSC either using an interworking function or by adding a VoIP telephony server to the MSC. These methods are not 3GPP standards. One such example is VoLGA, whose specification is provided by the VoLGA Forum [11], and is an interim method selected by very few operators because of the needs of their networks and business environments. It is particularly useful to operators who have a predominantly 2G network, because it enables simultaneous voice and data services they cannot offer 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 can use only one radio for both voice and data services, remaining entirely on LTE radio access instead of falling back to 2G/3G radios. This means LTE’s high data rates are always available, even during voice calls. Hence, these methods provide voice service for LTE, but with limitations on global roaming and interoperability, and a limited selection of handsets because of the lack of a significant subscriber 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 the benefits that subscribers of IMS VoIP and ACP-based voice obtain with all-IP are not available. For example, wideband audio and services such as video telephony that rely on an end-to-end IP path will not work.

As for the network deployment, these custom methods defer IMS’ deployment and integration, but like CSFB, require the deployment of new network elements or significant upgrades to existing net-work elements that are done only to provide legacy voice service. Similar to IMS VoIP and CSFB, the custom methods also require a voice client for the device, but are further challenged by the relatively small 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 require additional capabilities in the MME and eUTRAN. Similar to IMS VoIP, the eUTRAN must support VoIP. Those operators who deploy and integrate IMS for GSMA RCS service are well positioned to extend that same IMS to provide VoIP in LTE, allowing them to bypass these methods.


Figure 5. custom methods: circuit core, packet access (voLGa 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 subscriber’s global roaming and interoperability 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 operator’s network environments and competitive business situations may cause them to consider other methods. Table 3 summarizes the pros and cons of the methods; these factors and 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 LTE’sbandwidth duringvoice calls

Network change• VANC, AAA server, security gateway• MME software and interfaces• eUTRAN software and interfaces plus VoIP QoS• VOLGA client

Core network applications

SMS center HSS


Table 3. comparison of impacts on the network

4. The Path to LTE and the One Voice Initiative

Given these justifications for using IMS VoIP and SMS in LTE, the popular question is why aren’t more operators implementing it earlier? Several factors drive this behavior.

First is the operator’s urgent need to improve mobile data services, in terms of the bandwidth for an individual subscriber and the total bandwidth available to aggregate simultaneous users in the cell’s sector. 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 LTE devices such as smartphones and mass market phones with IMS voice clients would be available. The readiness of the network vendors and global roaming and interoperability were also critical. These reasons are why operators and vendors created One Voice: to foster a solution and promote the eco-system’s availability.

The One Voice initiative uses the 3GPP’s currently available, open standards and defines the minimum mandatory 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 the operators, handset vendors and network vendors to create and deploy services more quickly. This avoids the fragmentation of the global mobile network, which would risk the ability for global roaming and interoperability that people today enjoy with the 2G/3G networks.

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

IMS enables many sophisticated services based on many specifications, often with multiple options for enabling the same function. Not all of these many standards are necessary in order to provide the initial IMS VoIP and SMS in LTE service. Therefore, the One Voice initiative defines a common, recommended feature set and selects a recommended option when multiple options exist.

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

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

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

SErvicE and dEPLoyMEnT FacTorS iMS voiP cSFb cuSToM METHodS (circuiT corE, PackET accESS)

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


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

• Subscribers obtain the benefits of global roaming and interoperability, as they do today with 2G 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 and professional services.

5.1Alcatel-Lucentend-to-endLTEAlcatel-Lucent has established an early leadership position in LTE, selected by Verizon Wireless — one of the world’s first movers in LTE — as a key supplier for the operator’s planned LTE deployment. Alcatel-Lucent was chosen as a supplier for all areas of the operator’s 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 Division Duplex (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 to all-IP wireless broadband, with LTE as a key step in this transition. LTE is therefore a strategic investment area for the company.

Alcatel-Lucent is fully committed to providing its customers with an industry leading end-to-end LTE solution. The Alcatel-Lucent “Ultimate Wireless Broadband” end-to-end solution [14] enables wireless and converged service providers to advance their business, operational model and end-to-end network. 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 ecosystem of devices, content and application partners. This solution leverages the Alcatel-Lucent broadband and IP market leadership to deliver unprecedented scalability, quality of experience, business agility and controlled network costs.

Alcatel-Lucent recently announced that FT/Orange has selected Alcatel-Lucent for an LTE field trial 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, using the Alcatel-Lucent e-nodeBs and evolved packet core. Alcatel-Lucent was also invited to participate in LTE trials by Telefónica and Etisalat [15] and Bouygues [16]. To date, the Alcatel-Lucent LTE solution has been selected by operators for trials around the globe, including both lab and field trials with Tier 1 operators in North America, Europe, the Middle East and Asia.

5.2Alcatel-Lucentend-to-endIMSService providers are looking for ways to minimize expenses while optimizing value. At the same time, 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 services and 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 enhanced services such as the GSMA RCS services (such as presence, address book, messaging, file and content sharing). Other service providers that offer wireline services are starting with consumer VoIP or migrating off of their aging Class-5 networks. The Alcatel-Lucent End-to-End IMS solution [17] (see Figure 6) allows service providers to start with any combination of services, adding new ones as the market warrants.


Alcatel-Lucent is a clear leader in the IMS space, holding more than 45 end-to-end references — including AT&T, the world’s largest live IMS deployment. Alcatel-Lucent IMS spans the applica-tions that service providers need, from fixed consumer VoIP (AT&T), fixed business VoIP (Belgacom), Class-5 Migration (Enitel) and Enhanced Communications Services (AT&T Video Share) to the Rich 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 IMS scenario. Therefore, carriers can benefit from the breadth and depth of this experience in all phases of a network transformation to IMS. This spans product readiness; planning; program management; large network operation, growth, and maintenance; and more. The field-proven capability on both the product and services sides benefits carriers looking to transform their network with minimal risk.

Service providers can select Alcatel-Lucent as their IMS provider with confidence, knowing our IMS has the reliability, flexibility, 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 products in more than 275 fixed and mobile networks, and we are involved in more than 45 full IMS network transformation projects.

Figure 6. alcatel-Lucent End-to-End iMS solution

Convergedwireline access

Convergedmetro and aggregation

Convergededge

Converged service-aware network management

Convergedbackbone

ConvergedRAN

Convergedservice control

• Common session control across fixed and wireless providing seamless service access and mobility

• From voice to rich multimedia communications enabling seamless service interworking across service provider networks

• Rapid, economical service innovation with massive application scaling

Consumer and businessVoIP/enhanced

communications

POTS/ISDN

3G RCS, LTE,femto, WiMAX

and more

TDM GPON/DSL MobileTDM GPON/DSL M bil

Alcatel-Lucent end-to-end IMS

Alcatel-Lucent IMS powers competitive multimedia communication services


6. Conclusion

In this paper we examined the methods for providing voice and SMS service with LTE: IMS, Circuit Switched Fallback, plus non-standard custom methods characterized by a 2G/3G circuit core, served by 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 operator to create innovative services, realize all-IP operational savings, and makes it possible to collaborate with ACPs.

By understanding the benefits that each option provides, and understanding the transformation that is necessary as described in “Options for Providing Voice over LTE and Their Impact on the GSM/UMTS Network” [9], operators can make better informed decisions about how and when to 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 are uniquely positioned to aid your transformation to LTE. With the most comprehensive portfolio of telecommunications 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, leveraging our unique expertise in 2G/3G standards, LTE trial leadership with major operators, and active participation in leading LTE organizations and forums

• An unmatched end-to-end LTE solution that leverages our market leadership in next-generation IP transformation and service delivery, recognized expertise in packet transport, industry leadership in IMS service delivery platforms, next-generation wireless access technologies and Alcatel-Lucent Bell 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. Contacts

For more information on Alcatel-Lucent IMS in LTE solutions, please visit www.alcatel-lucent.com or contact your Customer Team representative.

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

EdElkin:[email protected]+1 630 224 8491

WimVanDaele:[email protected]+32 3 2404601


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 telecommunications

GSMA GSM Association

HD voice high-definition 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 Identifier

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 world’s first high-definition voice service for mobile phones in Moldava,” September 10, 2009, http://www.orange.com/en_EN/press/press_releases/cp090910en.jsp


[6] “Global Telecom Companies Announce a Standards Based Solution for Voice and SMS Services 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.fiercewireless.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/Specification-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] Telefónica, 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!!?LMSG_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, Current Analysis, November 5, 2009

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

www.alcatel-lucent.com Alcatel, Lucent, Alcatel-Lucent and the Alcatel-Lucent logo are 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 responsibility for inaccuracies contained herein. Copyright © 2010 Alcatel-Lucent. All rights reserved. CPG4688100102 (02)

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