AT&T, Verizon Inch Toward Open RAN

Mike Dano
9/9/2019
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The nation's two biggest wireless network operators continue to move toward technologies that promise to make wireless networking components cheaper and more interchangeable. The actions could allow wireless network operators to reduce the money they spend on networking equipment and to pit vendors directly against each other in terms of performance and price.

The clearest indication yet of this trend comes from AT&T, which announced that it successfully tested enhanced Common Public Radio Interface (eCPRI) connections on its 5G millimeter-wave (mmWave) spectrum using equipment from Nokia and Samsung Electronics America.

"The CPRI interface today has proprietary aspects which can result in a slower or more costly network build as we increase the bandwidth served requiring more fibers per radio," wrote AT&T's Gordon Mansfield in a post to the company's website, though he did not provide details on exactly which eCPRI specifications AT&T is implementing, or whether the operator might deploy it commercially. "eCPRI is an enhancement of that technology. It'll increase the efficiency to support higher bandwidth across fewer fibers. It is also what open interfaces are being built on, making it easier to use multiple vendors in a build. The benefits of this expanded flexibility and capacity will make it easier to deploy mmWave in markets where laying fiber is difficult or impractical, and promote cost effective operations by giving carriers the flexibility to use a variety of vendors to help bring fastest deployments at the best cost."

Analysts have long speculated about the possibility of operators severing vendors' proprietary CPRI connections between the radio and the base station, often referred to as "fronthaul." Due to that proprietary connection, an Ericsson radio can only work with an Ericsson base station, for example. But an eCPRI connection could, for instance, allow a Nokia radio to connect with a Samsung base station. And that could allow an operator such as AT&T to purchase the cheapest or most capable components, and to plug them into each other, regardless of which vendors' brand is displayed.

Thus, it's no surprise eCPRI topped the list of the most important technologies for 5G in a recent Heavy Reading survey of operators' 5G needs. Forty-eight percent of respondents picked eCPRI as "highly important."

But eCPRI is just one piece of a much broader and more complex puzzle that wireless operators are working to assemble, here at the outside of 5G. Under the banner of "open RAN," operators including AT&T, Deutsche Telekom, Telefonica and a wide range of others are working to overhaul key design elements of wireless networks. Specifically, they're pushing vendors to adopt software-powered, virtualized network elements, white-box hardware and standardized interfaces in place of expensive, specialized bits of hardware that lock operators into one vendor's ecosystem of products.

Part of that trend includes a move to cloud processing, which vendors have touted as a way for operators to reduce costs. Along these lines, Nokia recently announced that its AirScale products now power a "commercially deployed cloud-based 5G radio access network," and that it's "in one of the busiest cities in the US."

"This 5G milestone was made possible by our cloud base station, which splits traffic to ensure each connection gets the service it needs -- time-critical functions are processed at the cell site by our high performance AirScale distributed units (DU) close to the radios, connected via Ethernet fronthaul, while the centralized control unit (CU) performs non-real-time functions fully virtualized and more cost-effectively in a centralized data center," wrote Nokia's Mark Atkinson on the company's website.

Nokia did not name the operator that deployed its cloud RAN architecture, but a widely reported Tweet from the company appeared to indicate that Verizon was running the system in Dallas. A Verizon representative declined to comment on the situation, and a Nokia representative did not respond to questions on the topic.

To be clear, some analysts have argued that vendors will never fully embrace a completely open, cloud-based RAN, partly due to the fact it could cut into their profits and party because they wouldn't be able to eke out the performance enhancements that could be obtained through a tighter integration between hardware and software. Nonetheless, operators like AT&T and Verizon appear keen to push the notion of open RAN, via cloud deployments and eCPRI, as far as they can.

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

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