AT&T is preparing to embark on a major 5G network buildout leveraging its vast midband spectrum holdings. However, a top company official said the operator won't implement cloud radio access network (RAN) technology as part of that effort.

"The evolution to the cloud is not really mature yet," Gordon Mansfield, AT&T's VP of mobility and access architecture, told Light Reading recently. "And so right now it's more important to get our [midband] spectrum in use. So we're building it in a more traditional fashion."

Mansfield said that AT&T hopes to implement cloud-based designs into its RAN during the company's next upgrade cycle, though he declined to speculate on when that would be.

"What ends up happening is, your baseband components typically have a relatively short lifespan," he explained. "We're constantly getting new capabilities with every new release. And at some point the compute capabilities of the existing baseband will exhaust. And it's our goal to make sure that we're ready in the next upgrade cycle to start to convert that to cloud. Exact timing of that is a little bit TBD [to be determined]."

He continued: "We're confident that when we do our next upgrade cycle we will do it in a more cloud-like configuration."

Figure 1: An AT&T technician installs a 5G radio.
(Source: AT&T)

AT&T spent a total of around $36 billion during the FCC's two recent midband spectrum auctions for licenses around the country. The company expects to spend another $8 billion over the next few years installing midband 5G radios from Nokia and Ericsson to put that spectrum into use on its cell towers. The company has said that project will get underway in the coming months.

A question of processing power

"We're using the latest and greatest radios for all of our midband deployments," Mansfield said, adding that the radios would sport 64x64 Massive MIMO capabilities.

However, such radios require substantial processing that cloud RAN designs cannot yet support, he said.

"When you start thinking about Massive MIMO capabilities, the timing and synchronization required to support that requires an accelerator, even before you worry about scale," Mansfield said, noting that radios in lowband spectrum don't require as much processing and therefore might more readily support cloud designs.

"And so, candidly, you wouldn't get the performance out of the network if you tried to do it with the cloud today," he said. "That's why I'm not doing it. I'm not going to take a step backwards. Everything that we do has to be additive."

But cloud RAN technology is improving, Mansfield said, noting that vendors showed off cloud-based Massive MIMO acceleration technologies during the recent MWC Barcelona trade show. However, those offerings will take 12 to 18 months to mature and scale, he added.

"Directionally, that's where I see it now," he said. "There's a lot of proof of concepts that you'll see this year."

Companies including Dish Network have touted the savings and flexibility they're deriving from cloud RAN technologies. However, Dish has not yet begun to deploy its own midband spectrum holdings.

As for AT&T's move to the standalone version of 5G, Mansfield said the company will eventually do so. However, he declined to say when that would happen. That represents a delay from the company's earlier plans to launch standalone 5G in 2020.

Related posts:

— Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano