AT&T's Kris Rinne on the specifics of moving to VoLTE

with Kris Rinne, SVP of Network Technologies at AT&T Labs

Kris Rinne

      Kris Rinne

AT&T Mobility's (NYSE:T) LTE rollout has been slow and deliberate, but it is rapidly picking up steam. At the end of 2011, the operator had extended LTE coverage to 74 million POPs across the United States, and it is on track to double coverage this year to more than 150 million POPs. By the end of 2013, AT&T's LTE build-out will be substantially complete with the network covering more than 80 percent of the population.

FierceBroadbandWireless editor Tammy Parker caught up with Kris Rinne, senior vice president of network technologies at AT&T Labs, during the CTIA Wireless 2012 show, where Rinne discussed AT&T's plans for upgrading its mobile network as well as some of the things that make wireless competition in the United States particularly unique. This is an edited version of that conversation.

FierceBroadbandWireless: You've said that AT&T will deploy LTE-Advanced by 2013. Will that be across the entire LTE footprint?

Kris Rinne: LTE-Advanced is a very broad category of features and functionalities. There are aspects of that that we will deploy, such as utilizing the capability of the self-optimized network, some of the capabilities that were defined in the standard, such as how you reselect between the macro network and the small cell network and optimize that experience [ and] some of the carrier aggregation, which allows us to take disparate spectrum bands and bring them together and treat them from an aggregation standpoint to improve the overall throughput. So there will be various functionalities out of that whole LTE-Advanced capability. Generally, it would be deployed where you need to deploy it. Like the carrier aggregation, we may choose to do a combination that we don't necessarily have in every market, but that capability would allow us then to do two or three different combinations that would ultimately become the focus.

FierceBroadbandWireless: Would you really be able to do carrier aggregation by the end of this year?

Rinne: We would hope to have infrastructure in place to where we can start testing that. That's going to be a challenge in terms of how to optimize that across the ecosystem.

FierceBroadbandWireless: Regarding the deployments of SON that AT&T has with Intucell in California and Georgia, are those just trials?

Rinne: Those were trials, and now we're moving forward with nationwide implementation on the nationwide UMTS/HSPA network. There would still be work to do with multiple partners in terms of how that works across LTE and UMTS/HSPA.

FierceBroadbandWireless: Does AT&T have any plans for voice over HSPA?

Rinne: We're more focused on VoLTE. So we're looking at how do we take the QoS capabilities and map a subset of those into HSPA. But right now we're more focused on a feature called SRVCC, which would allow you to go from a VoLTE environment to the underlying circuit-switched environment on UMTS.

FierceBroadbandWireless: You said your VoLTE plans will be firmly in place for deployment in 2013. What exactly needs to happen for that to take occur?

Rinne: All of the feature functionalities that we support today on circuit-switched have to migrate to IP. So, how you do E911 location information in an IP environment, how you do your CALEA, how you do QoS getting back from an integrated standpoint between our core and our radio access so that you optimize that experience, [and] optimizing the radio access network within a coverage area so that your uplink and downlink capabilities are more symmetrical versus the way they're highly asymmetrical today. Those are all things that are part of the implementation in addition to just getting the IMS architecture pulling the data.

FierceBroadbandWireless: You've said you are bullish about the U.S. government's plans for spectrum auctions. Do you really think things such as incentive auctions are going to work?

Rinne: Well, if you're talking about, say,  specifically the broadcast spectrum, you've got to provide an environment where the current spectrum owner gets something out of it in order to move it forward. We think exploring different options like that so we do get that spectrum available for mobility services is important, and then, we also think it's very important that you have a broad number of participants in those auctions. We're supportive of keeping that process moving forward.

FierceBroadbandWireless: NTIA has recommended making available 95 MHz of spectrum but has also mentioned that the spectrum, as it's migrated from government to commercial use, might be shared. Do you think that's feasible?

Rinne: Spectrum sharing is a very, very broad term. Geographic partitioning can be a means of spectrum sharing, and we've made that work in the industry previously. [Regarding] spectrum sharing within a geographic footprint simultaneously, one way you make the network very efficient is end-to-end control in terms of knowing that I have interference in this space so I move to a different spectrum block. Sharing in that manner, I think, would make it much less efficient. [Sharing] is a very broad term and has to be more narrowly defined before you can say whether that's doable or not.

FierceBroadbandWireless: The topic of infrastructure sharing comes up a lot at the Mobile World Congress, so why hasn't the U.S. done more infrastructure sharing? Do you think there are possibilities for this?

Rinne: I think we're in a much different space in terms of when you look at the average U.S. consumer's voice consumption versus a European's, it's three to four times higher in the U.S. I think that's also true for data. So we're at a very different place in terms of the incremental capacity and capabilities that we need to introduce. There's also the challenge of the different spectrum bands, and so sometimes trying to support that very broad spectrum [across multiple operators] doesn't really reduce your costs versus supporting it individually.

It's the roadmap in terms of backwards compatibility, like in our case where the LTE network would need to be tightly integrated with the UMTS network in order to optimize the circuit-switched fallback experience because you have to know where to point the device from a UMTS standpoint. Some of those sorts of things make [infrastructure sharing] a bit more difficult in terms of where we are in the U.S. vs. other places. That said, we do access sharing in terms of common tower infrastructure and things like that.

FierceBroadbandWireless: Looking at AT&T and its network, what keeps you up at night?

Rinne: I sleep pretty well. And when you look at what we executed against last year for both the capacity growth, the migration of the spectrum from GSM to UMTS, the augmenting of backhaul capability, the initial introduction of LTE on a very broad scale [ and] the Ethernet deployment, we've demonstrated that we can execute. Continuing to scale that while we continue to optimize the experience from a customer standpoint and then begin to layer in these new capabilities and functionalities, I think we're well positioned, but there's always challenges ahead in terms of not knowing what you don't know.

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