AT&T's Donovan: We'll deploy carrier aggregation where we can, based on spectrum availability

AT&T Mobility (NYSE:T) is going to deploy carrier aggregation technology where it can, depending on how much spectrum it has available to meld together, according to a senior company executive.

AT&T John Donovan


AT&T's John Donovan said each carrier faces unique circumstances for how they can use carrier aggregation technology, which bonds together disparate bands of spectrum to create wider channels and produce more capacity and faster speeds. Donovan, senior executive vice president of AT&T Architecture, Technology and Operations, noted that some carriers could aggregate low-band spectrum for coverage and higher-band spectrum for capacity.

"And so we're going to do it in different sequences across carriers depending on availability of spectrum," he said in an appearance at the Barclays 2014 Global Technology Conference, according to a Seeking Alpha transcript of his remarks. "I think our team has done a great job with a spectrum portfolio that has a lot of spectrum across different bands. So I think we stand to gain more than most out there as carrier aggregation goes from two to three to four to infinity."

Currently, AT&T is using carrier aggregation on a small scale by combining its 700 MHz spectrum and its 2100 MHz AWS spectrum in a handful of markets. However, next year AT&T plans to deploy LTE on its 2.3 GHz WCS spectrum and is also refarming its 1900 MHz PCS spectrum for LTE service, opening up other potential avenues for carrier aggregation in the future.

Other U.S. carriers are also moving ahead with carrier aggregation plans. Verizon Wireless (NYSE: VZ) plans to launch carrier aggregation for its 700 MHz and AWS spectrum in 2015. Sprint (NYSE: S) has indicated it plans to deploy the technology for its 2.5 GHz TD-LTE service by year-end. And T-Mobile US (NYSE:TMUS) too is planning to implement carrier aggregation.

Donovan also touched on other key technology areas and developments for AT&T. In terms of Voice over LTE, which AT&T now has running in parts of 19 states, Donovan said the reliability of VoLTE on AT&T's network is going to be an advantage because it has built out a dense network. He noted that "it's always risky to take the most important service that you deliver, voice service, and throw it over an IP network where you might have some holes."

So far, Donovan said, AT&T's dropped call rates on VoLTE "have been extraordinary by our internal measure, we're ahead of where we thought we would be. I think we are going to have a reliability advantage in VoLTE and so now it's a question of devices."

AT&T has said it will continue to optimize, test and expand VoLTE coverage throughout 2015, and that it will release more VoLTE-capable devices.

Donovan said that although AT&T still has millions of customers on 2G phones, it wants to migrate as many of those customers as possible to LTE before AT&T shuts down its 2G network at the end of 2016. Doing so will let AT&T free up anywhere from an extra 5 to 15 MHz of PCS spectrum depending on the market, Donovan said. "The trip from 2G to HSPA+, it's six to eight times more efficient, and then the move from HSPA+ to LTE gets you another 50 percent efficiency or so," he said. "For us it's really an important play to run given the spectrum efficiencies that are available."

Donovan also said that AT&T may work to expand the reach of its network to new areas, but would mainly focus on increasing the density of its network.

In terms of his stance on "5G" networks, Donovan said that AT&T would like 5G to represent a significant advancement in air interfaces. Currently, most network advancements have moved away from the radio access network to the core network, he said, to handle traffic from video and the Internet of Things.

"Can we benefit from standards? Yes. Can we flatten the network? Yes. Can we reduce components? Yes," he said. "But I'm more enthused about making that stuff software defined than I am next-gening it, and I'm really kind of pushing towards getting an air interface leapfrog that would allow us to carry more bits per hertz, so that we can gain more efficiency in our spectrum. So I don't want you to think that that's a lukewarm response, it's sort of a high bar saying if you can clear this, then it might make sense to take a look. Absent that, then it's good to sit and talk and plan, but it's not going to trigger any sort of investment cycle."

For more:
- see this Seeking Alpha transcript
- see this Wireless Week article

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