UMA vs VCC: Approaches for Dual Mode Handset Services

By Steve Shaw

Fixed/mobile convergence (FMC) is an exciting opportunity for operators. The ability to bring together fixed and mobile products into service bundles to reduce churn, or to leverage fixed-line IP networks to deliver mobile services, offers strategic and tactical advantages. However, different types of operators have varied motivations for bringing FMC services to market. Depending on the operator type and the service requirements, some technologies are more appropriate than others to meet operators’ service needs and goals.

For operators contemplating an FMC service, two technologies - UMA and VCC - are at the center of a debate for dual-mode handset (DMH) service based on the new generation of Wi-Fi enabled mobile phones. While often viewed as alternatives to one another, in reality, their capabilities are not entirely comparable.

Defining UMA and VCC

UMA, also known as ’universal’ mobile access, is a 3GPP standard defined by the mobile community to extend voice, data, and IMS services over IP access networks. The most popular application of UMA is for dual-mode cellular/Wi-Fi handsets. With UMA-enabled dual mode phones, subscribers receive seamless mobility and handover between the GSM network and WiFi in the home, office or public hotspot.

UMA is focused on delivering the mobile experience (services, user interface, and other capabilities) seamlessly to subscribers over the IP network. It is a solution for mobile and integrated (fixed and mobile) operators.

Voice call continuity (VCC), on the other hand, is an ongoing standards effort in the 3GPP and is not yet finalized. Estimates are that it should be completed (Stage 3) by the end of 2007. Some view VCC as an alternative to UMA for dual-mode handset service.

VCC uses SIP for call control. Because of this, its proponents say that a primary advantage of VCC is that it is “IMS-centric.”

Because VCC relies on SIP, the ideal candidate for a VCC solution is an operator which has already installed/invested in SIP/VoIP infrastructure for voice and is looking to leverage mobile services. Today, this is typically a fixed operator, or the fixed division within an integrated operator.

Fixed operators have invested in SIP/VoIP as a response to alternative fixed line voice providers like Vonage and Skype because they are anxious to find a way to stem the loss of voice revenue to the mobile network. Because fixed operators have an immediate and pressing need to compete, work continues to develop the specification.

Evaluating the Approaches

For operators looking at a mobile/Wi-Fi convergence service, it’s important to determine evaluation criteria for framing the decision. Chief among these decisions is to determine the service expectation for the subscriber. Does the subscriber have the same user experience on the fixed network as well as the mobile network? If not, why?

This is an extremely important point. Sales people must be able to sell around these issues and support/customer care teams need to be knowledgeable about service differences. Any service differences must be explained to the subscriber, and he or she must be re-trained to understand the new functionality. In the end, changing subscriber behavior is difficult, and any differences in service functionality should be considered carefully.

With UMA, the user experience is exactly the same. All services (voice, packet, and IMS) work the same on the GSM network and the WiFi network. The subscriber uses the same address book and the same interface/menus on the device. The primary difference is that packet services run faster over the broadband/Wi-Fi access network than over the existing EDGE/GPRS/UMTS network.

Additionally, with UMA the handset moves seamlessly between networks with mobility for voice as well as packet data services (streaming audio, video). Once configured, the handset automatically detects and attaches to the appropriate WiFi access points, thus providing a truly seamless experience.

For VCC, however, there are some glaring holes in the user experience. VCC provides for ’voice’ call continuity. There are no provisions for delivering supplemental services (SMS, MMS, or ringtones) to subscribers when on the fixed network. It is clearly a different experience for the user.

Additionally, there is no support of packet services continuity with VCC. A key ’advantage’ of VCC is its native SIP/IMS support, which should be ideal for new value-added applications like streaming audio or video; yet seamless mobility for packet services is not supported.

Another criteria to evaluate with both UMA and VCC is the state of the standard and support for the standard. Every year, hundreds of standards are ratified yet never commercialized. Success in the standards arena is no guarantee of commercial success.

UMA was ratified by the 3GPP in April 2005. It is a mature specification that has been vetted through multi-vendor interoperability testing and commercial deployments. Within the GERAN group that manages the specification, updates and modification continue. UMA is a vibrant specification with an ongoing life driven primarily by operators choosing to deploy it.

VCC however, is still working through the standards process. While there are claims from some vendors of products that are “VCC-compliant,” it is difficult to meet that requirement until the final specification is agreed upon. More importantly, vendor interoperability can not begin until the specifications are finalized.

Next to consider is, what is the state of the ecosystem for the technology? Are there handsets? Are major operators deploying? How much pioneer work will be required to bring the first products to market?

With UMA, handsets are available today from brands that consumers know and trust, including Nokia, Motorola, Samsung, LG, BenQ, and HP. Due to UMA’s position as a ratified 3GPP standard, most handset vendors have developed UMA into their base code platform and can build the protocol into handsets as required.

For VCC, handsets are available from UTStarcom, Paragon Wireless, and others — not exactly mainstream consumer brands.

With UMA, Orange/France Telecom has deployments in its four largest markets - France, UK, Spain, and Poland) T-Mobile, Telecom Italia, TeliaSonera, and British Telecom have deployments of UMA-based dual-mode handset service. There is clear and certain operator momentum behind UMA.

Today, there are no announced VCC deployments.

The final evaluation to consider is how the technology supports the future evolution of the network. Specifically, how does the technology support IMS services and applications in the short-term, and how does it fit with most operators’ longer term evolution to IMS telephony?

Today, UMA transports packet services, including IMS/SIP based services, with seamless session mobility between the two networks. UMA is a radio access technology, completely agnostic to the services which run over it, whereas IMS is famously agnostic to the underlying radio access technology. Therefore, UMA transports and provides seamless mobility for IMS applications just like it supports other mobile voice and packet services.

In the long term, operators are looking to de-commission circuit voice services in favor of an all-IP IMS network. Yet the fundamental principles which compel operators to deploy UMA today - low-cost, high-performance mobile services in home - still apply with IMS/SIP telephony.

It is important to note that this evolution requires an upgrade to today’s 3G radio access network (UMTS/WCDMA) to 4G/LTE technology capable of supporting packet voice services. When this RAN upgrade is complete, operators will still need to leverage the Wi-Fi/broadband in subscribers’ homes and continue to use UMA to provide seamless mobility between the two networks.

For VCC, as discussed above, mobility for IMS applications is a short-term problem as the functionality is not defined in the specification today. However, in the long run, VCC actually becomes a transitional technology which must be phased out as IMS telephony phases in. Because VCC is providing a bridge between the GSM/circuit core network and the IMS/SIP/VoIP core, as the circuit core is decommissioned in favor of the packet core, there is no need for the bridge.

Which Will Win Out?

With so many advantages for UMA, one may wonder who is driving the VCC specification today. Frankly, it is fixed operators. Fixed-line revenues have been under enormous pressure from substitution to the mobile network and disruptive VoIP competitors. Some fixed operators are pushing the VCC specification forward as a way to pull voice minutes off the mobile network and onto the fixed SIP/IMS network when subscribers are indoors.

Thus, VCC has its roots with fixed operators and the fixed divisions within integrated operators. UMA however, is a mobile-centric solution, designed to connect to a mobile core network and deliver mobile services over the fixed network.

Within integrated operators, eventually a decision must be made as to the future of indoor voice service revenues. Is the investment made in the fixed network (VCC) or mobile network (UMA) to deliver in-home voice services? In the future, will consumers use their fixed phone or mobile phone more?

Integrated operators like Orange/France Telecom, Telecom Italia/TIM, and TeliaSonera have all come to the same conclusion: mobile is the future and UMA is the technology for mobile operators to accelerate fixed-mobile substitution. IT

Steve Shaw is the Associate Vice President of Marketing for Kineto Wireless and an evangelist for UMA technology. Steve is a frequent contributor to articles on UMA and writes the UMA Today blog.

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