T-Mobile's president of technology and chief technology officer John Saw has warned SpaceX that it will take more than just spectrum to establish a competitive network in the US.

Saw's comments last Friday came after the announcement that SpaceX has struck a deal to snap up Grain Management's nationwide 800MHz spectrum portfolio.

Although the financial details of that deal were not disclosed, it's estimated that the acquisition is worth $8 billion, and will support SpaceX's ambitions to offer next-generation satellite direct-to-device (D2D) services for its Starlink Mobile service.

Elon Musk's SpaceX is pushing to compete with the likes of AT&T, Verizon, and T-Mobile, and also secured the go-ahead to deploy 15,000 high-capacity D2D satellites last week.

These announcements have emboldened Musk and SpaceX, with Musk even noting the spectrum is the “last critical piece of the spectrum puzzle needed for SpaceX to provide complete phone coverage in America."

Unsurprisingly, all this noise has drawn a response from the carriers, with Saw taking to LinkedIn last week to offer his view.

In his detailed post titled "Spectrum alone doesn't make a network," Saw said he welcomed the competition.

"If this is truly the beginning of a new wireless provider in America, we welcome competition. It's good for innovation, good for the industry, and most importantly, good for customers," said Saw. "But great wireless networks aren't built with headlines or spectrum licenses alone. They're built site by site, neighborhood by neighborhood, in subway tunnels, office buildings, stadiums, and communities across America."

Spectrum is only the starting point

Others have tried and failed to become a fourth mobile carrier, usually due to being unable to compete with the Big 3 carriers, with EchoStar the most notable recent example, though SpaceX has snapped up significant spectrum from EchoStar to support its ambitions.

But that spectrum coupled with the Grain deal, which adds 14MHz of paired 800MHz, won't be enough, notes Saw. Saw highlights that spectrum is "just the starting point" and points out that SpaceX's total of roughly 80MHz portfolio is significantly less when compared to T-Mobile's nearly 400MHz of mid-band and low-band spectrum holdings.

"You can acquire spectrum in a single transaction. You cannot acquire a nationwide, high-performing wireless network overnight," added Saw.

Saw adds that building a network takes years of engineering, site acquisition, network optimization, technology innovation, and relentless execution. "It also takes the stores, customer care, distribution, and relationships that customers depend on every day."

He's also keen to point out the challenges that satellites face when providing mobile coverage, including the significant distances that this connectivity has to travel from Space.

"Lower-frequency spectrum can help improve satellite connectivity, but it doesn't change the fundamental physics. A satellite signal traveling hundreds of kilometers simply faces challenges that a nearby cell tower doesn't," he adds.

Saw is sure that direct-to-cell has a key role to play in supporting connectivity, but is adamant it won't come at the expense of terrestrial networks, highlighting that the technology will fall short in supporting indoor connectivity on a consistent basis.

"Covering a geographic area is one thing. Delivering the speed, responsiveness, and capacity customers expect from a modern 5G-Advanced network is another. Direct-to-cell has an important role to play in extending coverage. But it is a complement to terrestrial networks, not a replacement for the capacity of a dense 5G-Advanced network," he said.

T-Mobile has notably worked with SpaceX to support its own D2D offering, a partnership which dates back to 2022. Quite what that partnership looks like long-term is unknown, and even more so since T-Mobile formed a D2D satellite-focused spectrum-pooling joint venture (JV) earlier this month with AT&T and Verizon.