AT&T said it has made significant steps toward implementing cloud-based open RAN technologies in its mobile network.

Specifically, the company said it used Intel's FlexRAN software stack and Xeon processors to develop an "Advanced DU pooling" technology that can distribute baseband processing across multiple servers.

"AT&T is working with our RAN [radio access network] suppliers to incorporate DU pooling technology into commercial RAN software products," Gordon Mansfield, AT&T's VP of mobility access and architecture, wrote on the company's website.

Broadly, the announcement marks yet another milestone for AT&T as it shifts network operations from closed, proprietary, hardware-based technologies to open, software-based networking services running in the cloud. The transition started in 2014 when the company said it would virtualize 75% of its core network functions and accelerated last year when the company announced it would shift its 5G core into Microsoft's cloud.

Now, according to Mansfield, that work is expanding into AT&T's RAN. "The RAN basestation distributed units (DUs) are one of the most distributed, resource intensive, and complicated parts of a wireless network," he wrote. "Due to these hyper-stringent requirements, radios have traditionally needed to be physically connected to baseband equipment dedicated to the radio and ready to go at a microsecond's notice even if it's the middle of the night and nobody is using the radio. And so, the mapping between radios and servers was not very elastic. At least until now."

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

Mansfield explained that AT&T's new Advanced DU pooling technology essentially collects complex signal processing information from AT&T's radios and runs it through a collection of general-purpose processors in far edge data centers or central offices.

"It gives unprecedented elasticity and flexibility to the network to distribute (and redistribute) traffic instantly," Mansfield wrote. "If a baseband server becomes overloaded or fails, all impacted user sessions can be moved to a different server without any disruption to customers."

Other operators and vendors globally have been touting similar efforts, so AT&T is not alone in working to shift its radio processing operations into a more open, flexible and cloud-based platform.

Moreover, AT&T has previously hinted at plans to push its 5G equipment vendors to support open RAN specifications. Doing so will allow operators to mix and match products from a variety of vendors, according to open RAN proponents. Indeed, for its part, Intel's FlexRAN software and Xeon processors have powered many of the market's initial open RAN offerings.

Nonetheless, AT&T's work on its Advanced DU pooling technology suggests that large, incumbent mobile network operators want to embrace the kinds of software-based, open RAN network architectures that upstarts like Dish Network and Rakuten have been promoting.

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