AT&T this week again filed complaints against T-Mobile with the FCC, arguing T-Mobile is poised to gain too much valuable midband spectrum for 5G.

"There is already a substantial imbalance in the midband spectrum holdings of leading 5G providers, the result of historical accident and past commission policies," AT&T told the agency. "T-Mobile holds a vast percentage of such spectrum because, over the years, its corporate predecessors Sprint and Clearwire quietly accumulated enormous EBS/BRS assets in the 2.5GHz band."

Today, thanks to T-Mobile's merger with Sprint and its subsequent winnings in the recent C-band midband spectrum auction, AT&T warned that T-Mobile now owns roughly 40% of all available midband spectrum in the US. "T-Mobile already has far more midband spectrum than any other provider – and could easily accumulate more unless the commission adopts and enforces reasonable spectrum-aggregation policies."

All eyes on 2.5GHz

At issue is the FCC's upcoming 2.5GHz spectrum auction. The agency is still finalizing the rules for that auction, which may happen next year, and AT&T is hoping to convince the agency to prevent T-Mobile from dominating the event.

"AT&T strongly disagrees that the upcoming auction for 2.5GHz spectrum presents a competitive opportunity for any provider except T-Mobile," AT&T wrote.

In order to prevent T-Mobile from gaining too much spectrum, AT&T argued the FCC should limit the amount of midband spectrum that any one carrier can own.

Importantly, AT&T acknowledged that its petition to the FCC will not affect the agency's upcoming Auction 110 in October. That auction – which covers 100MHz in the 3.45GHz band, an event Light Reading has dubbed the "Andromeda auction" – is designed to prevent any one company from acquiring more than 40% of the total spectrum available.

Thus, AT&T's petition is mostly focused on the agency's next auction, of the 2.5GHz spectrum licenses around the country that are not owned by T-Mobile.

Ongoing capacity concerns

This isn't the first time AT&T has voiced concerns over T-Mobile's spectrum holdings. In 2020 AT&T warned that T-Mobile owned an "unprecedented" amount of midband spectrum. At that time, both AT&T and Verizon both hoped to limit the amount of C-band spectrum T-Mobile could purchase in an auction that started at the end of 2020.

Although T-Mobile ultimately ended up purchasing only a small portion of the spectrum licenses up for grabs in the C-band auction, AT&T argued this week that T-Mobile "bid up [auction] prices by placing substantial bids of its own" in the C-band auction.

The issue is critical for AT&T and the rest of the nation's 5G network operators considering spectrum ownership is a critical element in any wireless network. In general, the more spectrum an operator has, the more network capacity they command, which directly equates to the number of customers they can support and the connection speeds they can provide. And, considering all of the 5G operators in the US are using the same basic standards and vendors, the only real way for them to separate themselves from their rivals is by gaining more spectrum.

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