T-Mobile US bolstered its already robust 2.5 GHz spectrum holdings that power its 5G network, running away as the biggest spender in the Federal Communications Commission (FCC) Auction 108 proceedings.

The carrier is on the hook for more than $304 million to pay for the 7,156 licenses it won during the auction, which ended Sept. 1. The carrier was far-and-away the biggest winner in the auction, picking up more than 89% of the total licenses up for bid.

That result is not unexpected as T-Mobile US currently controls a significant swath of 2.5 GHz licenses it received when it acquired Sprint. Those licenses provide significant capacity for the carrier’s 5G network.

The new licenses are focused in rural areas, with FCC Chairwoman Jessica Rosenworcel noting they provide a “unique opportunity to fill” in current broadband coverage gaps. That opportunity will fall most heavily on T-Mobile US, which is the only nationwide operator currently using the 2.5 GHz band for its 5G network.

T-Mobile US’ current 2.5 GHz-powered 5G service covers 235 million people across the country, or around 71% of the population. The new licenses cover 81 million people.

Nationwide rivals Verizon and AT&T did qualify for the auction but did not end up as significant players. AT&T did not win any licenses, and Verizon spent $1.5 million for 12 licenses.

Those two carriers are more heavily invested in the C-band spectrum residing between 3.7 GHz and 3.98 GHz, which the two carriers spent a combined $69 billion in acquiring.

T-Mobile US’ latest spectrum haul comes on the heels of the carrier agreeing to pay $3.5 billion for 600 MHz spectrum licenses it has been leasing to provide broad 5G coverage. The carrier had been leasing those licenses from Channel 51 License Co and LB License Co, which are both controlled by Columbia Capital.

“This was a spectrum portfolio that we had been leasing at a very small rate of dollars, and the lease was coming up, and so it had presented an opportunity for us to purchase the spectrum,” T-Mobile US CFO Peter Osvaldik explained during an Oppenheimer technology conference last month. He added that, “yes, that’s a big check to write.”

Observers noted that T-Mobile US paid around twice as much on average in this deal compared with what that spectrum initially cost during the FCC's 600 MHz auction in 2017.

“If you look at historically and maybe what the 600 auction … back in the day brought, certainly this is a little bit of a premium to that, as you’d expect,” Osvaldik said. “Spectrum values have gone up, usage has just gone up, our ability to utilize it in a different way in a 5G world is definitely there. I’m sure we would have bought a lot more of it had we had the opportunity and the means back during the 600 auction, but we’re very excited now to be able to add to our strategic holdings with this.”