Over the past 21 months, T-Mobile has slowly but surely overcome most of the obstacles blocking its proposed merger with Sprint. The carrier now expects to close the deal by April.

As a result, all eyes have begun to turn to T-Mobile's network team, which will be charged with combining the networking and spectrum assets of T-Mobile and Sprint into a merged offering company executives have promised will be "the world's best 5G network."

Indeed, in its initial merger announcement in April 2018, T-Mobile promised to invest $40 billion over three years to combine its network with Sprint's network – T-Mobile added that the resulting offering will provide nationwide average 5G speeds of 450 Mbit/s.

In an interview with Light Reading, Karri Kuoppamaki, T-Mobile's VP of network development and strategy, said one new element the operator might consider in its 5G buildout is open radio access network (RAN) technology. "We are doing a technology due diligence on O-RAN to be able to quantify and understand its benefits relative to the classical network architecture," he said. "And where it makes sense and provides some benefits, we will be looking at potentially implementing it."

However, Kuoppamaki cautioned that T-Mobile hasn't made any firm decisions about open RAN, and that it will need to consider how the technology might interact with its legacy 4G and 5G networks.

"As a company we've always embraced and supported open interfaces. I think there's a lot of value in having that. And that's what this industry is based on," he said. "We already have a network in place today, and so you have to also consider where in the network and how open RAN might provide benefits over what's in place today."

He added: "We don't have any firm plans as of today to move away from the network architecture that we have in place for 4G and 5G."

Open RAN's potential
Open RAN technology promises cost savings and flexibility by allowing operators to use general-purpose hardware and more open interfaces. In theory, that means more than one vendor could supply the components and products used at a given site – something not possible in today's networks.

Indeed, Rakuten in Japan said its embrace of open RAN technology is part of why it expects to cut 40% from standard cellular capital expenses and 30% from standard cellular operating expenses with its forthcoming 4G and 5G networks.

Further, open RAN interest isn't exclusive to new market entrants. Wireless giant Vodafone recently put its entire European footprint – comprising 100,000 mobile sites – up for a possible redesign based on open RAN technology.

But others have argued the technology isn't necessarily ready for prime time. "The reality is that fully compliant open interfaces as specified by the ORAN Alliance, the most relevant in this context, have not been deployed anywhere in the world yet. These are new grounds for the industry. In fact, it is uncertain whether the most critical interface specified by ORAN will be deployed widely, as alternatives are already being proposed by several contributing, significant members," Nokia's CTO Michael Murphy recently told US lawmakers.

Those are undoubtedly the factors that Kuoppamaki and the rest of the operator's networking team are evaluating. On one hand, they surely want to use the best and cheapest equipment available. On the other hand, they want to move quickly, and may not want to test out unproven products in a commercial setting.

The open RAN decision is one that Kuoppamaki will make with Neville Ray, T-Mobile's president of technology, alongside the operator's new CTO, Abdul Saad. Kuoppamaki and other top T-Mobile networking executives like Mark McDiarmid, Grant Castle report to Saad, while former Ericsson exec Ulf Ewaldsson – hired roughly a year ago as T-Mobile's SVP of technology transformation – reports to Ray.

T-Mobile executives could also work with some of Sprint's networking executives on the project, including CTO John Saw. Already Sprint is a member of the Telecom Infra Project (TIP), which is working on open RAN technology.

Kuoppamaki said that T-Mobile is ahead of the game in combining its network with Sprint's network. He confirmed that Samsung's new Galaxy S20 5G phones can support 5G in the spectrum bands that both T-Mobile (600MHz and millimeter wave bands) and Sprint (2.5GHz) are already using for 5G. He said that, if the operator successfully closes its merger with Sprint, it will be able to remotely update the phones so that they can access the 5G networks that T-Mobile and Sprint have separately activated already.

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