T-Mobile's technology president raised some eyebrows this month when he declared that a key 5G technology isn't ready for prime time.

"We are seeing some vendor delays there" in Dynamic Spectrum Sharing (DSS), T-Mobile's Neville Ray warned during his company's quarterly conference call with analysts, according to a Seeking Alpha transcript of the event. "It's to be a tough year on DSS."

But the other two US operators planning to use DSS have strongly disagreed with that assessment.

Specifically, AT&T's top networking executive, Jeff McElfresh, said the technology is performing well in lab tests, and that AT&T is now testing it in select markets.

"McElfresh was supportive of the DSS readiness for primetime," wrote the analysts at Wall Street research firm Wells Fargo of their discussions with McElfresh.

Verizon offered a similar outlook in comments to analysts at its recent investor event. "Management was dismissive of delay concerns (voiced by T-Mobile) as the market will not be truly ready for nationwide 5G anyway until the iPhone launch, in which case Verizon remains confident in its timeline," wrote the Wall Street analysts at Cowen.

While it's clear DSS is not available today in the US, most major players continue to promise that the technology will be commercially launched sometime this year. And that effort will likely coincide with the introduction of a 5G iPhone from Apple, widely expected this fall.

Thus, DSS could help usher in nationwide 5G coverage offerings from all the major wireless network operators in the US, just in time for the widely anticipated launch of a 5G iPhone. That's because DSS – an official part of the 3GPP's 5G standard – promises to allow operators to simultaneously transmit 4G and 5G signals in the same spectrum band. For operators like Verizon that don't have a lot of unused lowband spectrum, that's clearly better than taking chunks of spectrum away from 4G customers so that a few new 5G customers can use it.

Meantime, T-Mobile and AT&T are doing exactly that as they wait for DSS. T-Mobile is reserving most of its largely unused 600MHz spectrum exclusively for 5G, while AT&T is doing the same with portions of its 850MHz spectrum. With DSS, these operators will be able to run 4G and 5G concurrently in those bands, thereby using the spectrum more efficiently.

Vendor infighting
The warning of a vendor delay by T-Mobile's Ray raises the obvious question: Who's late to the DSS game? Industry observers have widely pointed the finger at Nokia, which has a history of missing 5G launch goals.

"Nokia will be commercially launching its Dynamic Spectrum Sharing solution this year," a company representative told Light Reading.

Meantime, an Ericsson official confirmed to Light Reading the company plans to launch its "Ericsson Spectrum Sharing" sometime in the first quarter of 2020.

Verizon "is trialing with Ericsson and Qualcomm (the SDX 55 chipset), while its other suppliers (Nokia and Samsung) also have a roadmap," wrote the Cowen analysts, noting that Verizon said a "majority" of its network footprint is now prepared for a DSS software update.

"I do think the vendors are late in delivering DSS, but at the same time, I think Verizon's later-this-year timetable is doable," explained analyst Chris Nicoll with ACG Research.

A number of analysts point out that the DSS debate appears to mostly boil down to market posturing. While Verizon waits for DSS to launch 5G nationwide, T-Mobile can continue to boast that it already offers nationwide 5G using a dedicated slice of its 600MHz spectrum.

Meanwhile, Verizon continues to argue that its highband, millimeter wave (mmWave) 5G is dramatically faster than T-Mobile's lowband 5G, even though it's only available in parts of about 30 US cities.

DSS capacity issues
That said, there do appear to be some issues around the use of DSS. "Some of the early rollouts and workarounds and pieces that we've seen are pretty corrosive and they would suck up capacity just by rolling out the feature," T-Mobile's Ray explained.

Omdia analyst Daryl Schoolar agreed that DSS could affect operators' overall network capacity. He said more network resources could need to be devoted to the control plane with DSS, thus reducing the overall amount of capacity available to users' downloads and uploads.

"There certainly is a capacity hit when it comes to DSS, but I think Verizon is in a better position to absorb the hit than T-Mobile is, who is already battling slower recorded speeds ... for its 5G compared to Verizon," noted Nicoll with ACG Research.

The analysts at Cowen point out that Verizon is likely to deploy DSS across its 850MHz, PCS and AWS spectrum bands. Thus, Verizon may have several ways to address capacity issues if it uses DSS across multiple spectrum bands. T-Mobile has only discussed using DSS in its 600MHz holdings.

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