AT&T (NYSE: T) provided more details about its 5G tests during sessions of the Brooklyn 5G Summit last week, saying it will extend its current lab testing to an outdoor test in Austin, Texas, this summer, predominantly focusing on fixed wireless.
"We'll start with 15 GHz tests and then move to 28 GHz. It will predominantly be fixed wireless," said Tom Keathley, SVP, wireless network architecture and design, according to Mobile World Live. "A main aim is to find out how millimeter wave technology works and then we'll pour back the learnings into the standards work."
Separately, Arun Ghosh, director of wireless communications at AT&T Labs, said during the last session of the summit that the tests start off as fixed as they need to make sure the base stations and devices are interoperable. While the standard for 5G has yet to be written, "we have to do a whole lot of interoperability testing," he said. Vehicular applications and high-speed mobility are part of the plan, but fixed is easier to do in the beginning, he said.
As for why AT&T is using 15 GHz, Keathley said the reason is pretty simple. "It's what we could get, it's what we could actually start with. When you look at the equipment available, the 28 equipment wasn't really going to come until later this year and we didn't want to wait to start. That's really the reason why we did that."
In response to a question from the audience during his keynote, Keathley declined to talk about 600 MHz because it's in a quiet period, but he did say it's possible and probably likely that the same air interface can be used for both millimeter wave and sub 6 GHz spectrum.
"I don't think that's locked in yet, I think there's still debate around that, but from our discussions with our supplier community and our other technology partners, we believe it's possible… I think it's likely that will happen but until it's locked in and until the standards are set, it could go a different way. If we come up with something that says there's an optimal air interface for IoT, for instance, in sub 6 GHz, there's no reason we couldn't go implement that if that made sense. But it's a little bit obscure because we don't know at the moment, but it would sure be great if we could use the same air interface there."
Filtered OFDM is the air interface that most people are talking about. But Cohere Technologies, for example, is proposing a 5G air interface based on Orthogonal Time Frequency and Space (OTFS) that it says co-exists nicely with OFDM.
During an earlier session at the summit, which was co-hosted by NYU Wireless and Nokia (NYSE:NOK), Keathley and other panelists were asked what pitfalls should be avoided in 5G. "I think what we need to avoid is fragmentation for 5G," Keathley said. "I think that's maybe the biggest danger we face right now and one we should all be cognizant of and trying to make sure we avoid."
Stephen Bye, CTO of C Spire, said the industry has to be careful not to try to boil the ocean for 5G, a sentiment others expressed as well. "When I look at the list of all the things we're trying to do with 5G, it's going to take forever," he said. "We're very keen to get better spectral efficiency and drive capacity in networks. LTE can get us so far, but we need wider band channels, we need to tap into the millimeter wave spectrum and we cannot wait five years for the standards process to try and solve everything… We've got to find a way to get the technology deployed faster." At the same time, the industry needs to get the economies of scale that the technology affords. "It's a challenge the whole industry has."
- see this Mobile World Live article
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