T-Mobile's 6G test filing is a cheap option on 2028 spectrum

T-Mobile has asked the FCC for experimental licenses to test prototype equipment in the 2.7GHz and 4GHz bands, a filing dated September 17 that reads less like a network plan than a placeholder on spectrum the carrier cannot buy for two more years.

The 2.7GHz testing would span seven sites—six in and around T-Mobile's Bellevue, Washington headquarters and one in Kirkland—and run from November 16, 2026, to November 15, 2028, with up to seven temporary fixed base stations each operating as many as six experimental devices. T-Mobile told the commission that no new towers need to be built and no antenna would be installed more than six meters above an existing structure, while the 4GHz testing, confined to the 4.8GHz-to-4.9GHz slice, would run through the end of October 2028. The application was noted on X by Steven Crowley, whose posts have tracked these filings.

The two windows bracket the event that matters: the FCC plans to auction 2.7GHz in 2028, a year after a planned C-Band auction, and the calendar is the entry fee — the argument this publication made on September 18 about the agency's $100bn spectrum target. Licenses themselves are the small check; the auction schedule decides what capital is left for the towers, fiber and power underneath them.

T-Mobile's stated case for testing is that it serves the public interest: critical research and development, no harmful interference, and "valuable data" on coexistence with in-band and adjacent-band users, federal radar systems and radio astronomy operations among them. That last part is the interesting one: producing the sharing record is the cheapest form of influence available to a carrier before a band is sold, and usability is most of what a 2.7GHz license will be worth.

The filing landed days after Verizon sought to test 4GHz midband spectrum for potential 6G use cases. Verizon named Ericsson as its vendor partner; T-Mobile named none, which suggests the carrier is keeping its equipment options open while the band rules and its own 6G architecture settle.

The physical read is narrower than the spectrum story: six meters above existing structures and no new towers means the incremental infrastructure lands on rooftop leases, fiber backhaul and power at sites already standing — the same logic behind the conversion of former Sprint switching sites into edge data centers, covered in August. The record T-Mobile compiles over two years, on how 2.7GHz shares with radar and radio astronomy, is the kind of filing that surfaces later in the sharing rules. Macro tower landlords have little to sell into a test like this.