Wednesday, November 19, 2008

China Mobile: Voice over LTE... via UMA/GAN?

As covered by Michelle Donegan at Unstrung, China Mobile is prepping their network for LTE, and voice will be an important element.

Bill Huang, general manager of China Mobile Research Institute, said that the company is well prepared to move to LTE, and stressed the importance of supporting voice. Mr. Haung went on to say that one option for Voice over LTE was the UMA/GAN protocol.

“We could carry voice over UMA” said Mr. Huang. “We will have an LTE network that supports voice…”. To clarify, what Mr. Huang is referring to is not the traditional ‘home zone’ UMA deployment involving Wi-Fi or femtocells.

The 3GPP UMA/GAN (Generic Access Network) standard provides a generic method for extending 2G and 3G circuit (and packet) services over any broadband access network. Until now, the standard had been used to enable mobile operators to extend their services over fixed broadband networks (DSL, cable,…). However, now with a high-speed, low latency *mobile* broadband network, GAN can be used to extend existing mobile services (like telephony) over LTE.

Clearly for the mobile operator, this is a very low-risk, low-cost method of bringing their voice services (and revenues) to their LTE network deployments.


Anonymous said...

The exact statements of Bill Huang were “We could carry voice over UMA," ..."We will have an LTE network that supports voice -- it doesn't matter what protocol we'll use. We'll use voice as the application."

Thus, China Mobile may or maynot favor this approach.

In my view, the choice of GAN for realtime service delivery over LTE is no more than an quickfix interim option. Mobile operators should support development of multimedia services and not merely replicate the traditional CS network services. GAN based approach is not a future proof solution and will lead to sunk investments . It is no comparison to flexibility of Multi-Service IMS Architecture with open and standard interfaces and SIP based Clients for multimedia support. With maturity of ICS and SC standards in 3GPP R8, IMS Centralized Service Architecture provides the best option for future network evolution of full service operators. ICS/SC solutions will be ready in time and therefore a short term quickfix solution should be avoided.

Steve said...

Good point. Certainly Mr. Huang with China Mobile did not commit to GAN or any other solution for voice. Moving to LTE gives them a very fast pipe on which to carry a myriad of new services.

Moving into LTE, I think operators will be faced with three options with regard to voice. One, do nothing. Just make LTE a mobile broadband service akin to DSL with no operator specific services. I don’t think this will be the norm, but certainly operators can simply deploy LTE dongles and laptop data cards, leaving ‘voice’ on their 2G or 3G networks.

Two, move to IMS for voice services on LTE. To me, this seems like the highest risk approach. It’s clearly a large investment, on top of the already committed LTE investment. All the services of the circuit world today will have to be re-created in IMS on day 1. The investment comes with the promise (hope?) that there are new revenue generating applications on the horizon to justify it. With voice revenues declining, it will be interesting to see what operators are willing to invest in ‘new’ voice services. But even at a purely tactical level, putting IMS on LTE handsets means that the handset needs to support two telephony clients, one for LTE and one for 2G/3G. More complexity for handsets means a longer delay until devices are available, pushing LTE out farther.

Three, of course, is to re-use the existing circuit core. There is GAN as well as other approaches (CS fall-back, …). The risk for GAN is very low. It’s a well defined, proven 3GPP standard. It maintains a clear separation between RAN and the service network (MSCs) so that OSS/BSS changes are minimal.

From the device standpoint, the protocol stack has already been implemented/integrated with all the largest handset manufacturers. Because it uses the same 2G/3G telephony application, complexity in the handset is significantly minimized.

For voice over LTE, there are definitely decisions that operators will need to make.

Anonymous said...

I beg to disagree on a few points.

1. Contrary to popular perception, investments in IMS are small, and certainly represent a very small fraction of the LTE/SAE investments. Furthermore, operator can build small scale systems and scale based on service uptake, thus minimizing risks. Thus, I disagree with you on the risk with IMS path.

2. I disagree with you on the interpretation of different complexity for GAN client and IMS Client support on handsets. There is no additional complexity in providing support for IMS. Recent initiatives of IMS RCS (Rich Communication Suite), Standardization of IMS Service APIs (JSR 289, JSR 325) in JCP will solve any remaining issues. I don't agree that support for IMS will add any delay to the availability of LTE Handsets.

3. By deploying LTE alone, mobile operators face a significant risk of becoming a fat dumb pipe, and loosing large part of revenues from messaging and even voice services - to over the top players. The solution lies in building a flexible service delivery architecture with IMS. I agree with the re-use of CS Core infrastructure and leveraging these investments. The re-use of MSC-S as ICS Enhanced MSC Servers or MGCFs or IBCFs can provide some investment protection. Operators can also avoid recreating all CS services in IMS domain, by adopting a smooth service driven migration from 2G/3G to LTE. This approach will focus on offerring subscribers a new multimedia telephony experience and not merely a replication of CS voice services.

Having said that, I full agree with you that operators definitely have some tough decisions to make, and only time will tell.

Steve said...

Now we’ve got a discussion going!

I think you make some good points. Let me offer my thoughts too.

The size of an IMS investment: I suspect a CSCF to support 100,000 users is not too expensive. (neither is a GAN controller, I should point out). I’m thinking more of the investment the operator needs to make to turn it into a viable service platform. This is an entirely new voice switch which cannot be installed in isolation. It must integrate with the existing service core to provide session and service continuity. And here’s the catch, if the CSCF supports the exact same features/functions/capabilities such that it can simply slide into the operator’s existing OSS/BSS/NMS infrastructure, then it does the exact same as the MCSs already in the network. Why not use the old MSCs? If it offers more/better/different functions, then there is going to be a significant back-end investment to support it.

Complexity of GAN clients: It is interesting that you point out RCS. My understanding is that RCS today relies on circuit services for voice and uses IMS for ‘multi-media’ applications. In fact that would work just fine with GAN for circuit services over LTE.

Deploying LTE with voice: I think we agree here. I think that your comment “operators can avoid recreating all CS services in the IMS domain by adopting a smooth service driven migration from 2G/3G to LTE” is exactly what we’re hearing from operators interested in voice over LTE via GAN. The point is to start with what the subscribers and operators already know, and then move to a multi-media telephony experience (a la RCS?)

Anonymous said...

Thanks for a very fruitful discussion on this topic. Let us see how the operator and vendor community reacts to the various approaches.

I believe that there will be co-existence of different approaches and much will depend on how the business case of different operators works out in their specific competitive and regulatory environment.