T-Mobile US president of technology Neville Ray (pictured) raised doubts about the maturity of open RAN systems and their ability to deliver promised cost savings, arguing key questions around system integration and R&D have yet to be answered.

During an investor conference, Ray acknowledged the appeal to greenfield operators, but said from T-Mobile’s perspective “it is not ready for prime time” despite it being “interesting” and the operator supporting development.

He noted T-Mobile is not adopting open RAN in any of the approximately 2,000 new cell sites it is adding each month.

Ray explained there is currently too much uncertainty over who ensures R&D alignment across the open RAN ecosystem and, critically, where operators should turn to resolve network issues when a complex web of vendors is involved.

“Who is ultimately responsible for all of the systems integration…And whose neck do you choke when things go wrong…I buy a solution from an Ericsson or a Nokia or a Samsung, it is warrantied. I have one neck to choke. If something goes wrong, I know where to go.”

He also expressed doubts about the associated cost benefits, “a big TBD” since it is unclear who will foot the bill for system integration and maintenance costs.

Ray said the “quickest, the most meaningful way I can rollout a 5G network at real pace is what we are doing today”.

“I’m not going to go and chase a bunch of capital efficiencies which I’m not sure exist at this point”.

Vodafone Group executives recently sought to rally operators around open RAN, but others including AT&T and Telus flagged integration complexity and costs as key hurdles to deployments.