T-Mobile US is really looking forward to next year’s spectrum auction. Today, it doesn’t have enough low-band spectrum to match the networks of AT&T and Verizon Wireless, T-Mobile VP of Federal Regulatory Affairs Kathleen Ham wrote in a blog post.

“As our competitors well know, arming T-Mobile with low-band spectrum is a competitive game-changer, enabling our service to penetrate building walls better and travel longer distances than we can with the spectrum we have today,” Ham wrote. “Imagine a T-Mobile with even greater coverage, offering innovative Un-carrier deals to even more customers in even more places—in direct competition with the Twin Bells!”

The Federal Communications Commission plans to set aside spectrum for carriers that lack low-band frequencies (those under 1GHz) in the auction of 600MHz spectrum currently controlled by TV broadcasters. But T-Mobile says the FCC’s plan doesn’t go far enough.

“The FCC understands the importance of low-band spectrum to competition, which is why they established a ‘reserve’ for the upcoming incentive auction for carriers like T-Mobile that have little or no such spectrum,” Ham wrote. “We commend the FCC for this decision. It was not easy due to the strong opposition engineered by AT&T and Verizon. But the FCC, recognizing the importance of this spectrum to competition, did the right thing. We would ask, however, that a few small—but crucial—changes to the rules be made.”

AT&T and Verizon control nearly three-quarters of low-band spectrum in the US, she wrote.

AT&T CEO Randall Stephenson has pointed out that "Sprint and T-Mobile did not participate in the 2008 auction of 700 MHz spectrum," FierceWireless reported last year. AT&T and Verizon ended up dominating that auction, while T-Mobile bought more spectrum than its competitors in a 2006 auction for higher-band frequencies.

T-Mobile says its high-band spectrum is good for providing lots of capacity, but low-band spectrum is what carriers really want. "Spectrum below 1 GHz... has physical properties that increase the reach of mobile networks over long distances,” FCC Chairman Tom Wheeler wrote in a blog post about the incentive auction in April. “The effect of such properties is that fewer base stations and other infrastructure are required to build out a mobile network. This makes low-band particularly important in rural areas." Low-band spectrum is also better at penetrating obstacles such as walls.

T-Mobile asked the FCC to reserve at least 50 percent of the 600MHz spectrum “for competitors with little or no low-band spectrum in [each] market.” While this would benefit T-Mobile and Sprint more than the larger carriers, it would also help AT&T and Verizon in certain geographical areas where they lack low-band spectrum, Ham wrote.

“This change is critical to guarantee enough ‘reserve’ spectrum to sustain four strong national carriers into the future as the FCC has said is important,” Ham wrote.

The FCC’s current plan would reserve a maximum of 30MHz out of 70 to 100MHz of available spectrum, T-Mobile noted in a filing in August.

T-Mobile did buy $3 billion worth of 700MHz spectrum from Verizon this year and is trying to buy more from other sources before next year's FCC auction.

T-Mobile improving as best it can, but new spectrum is what it needs

T-Mobile’s need for low-band spectrum isn’t surprising, given that nationwide network tests have consistently shown the company lags behind AT&T and Verizon. T-Mobile’s poor performance indoors led it to expand usage of Wi-Fi calling.

T-Mobile’s statement today paints a different picture than the one it typically provides to customers and the press, however. The company has repeatedly claimed that its LTE network is actually better than AT&T’s and Verizon’s. When RootMetrics’ nationwide test declared T-Mobile to be lagging behind in March 2014, T-Mobile CTO Neville Ray called the results irrelevant and based on old data. “T-Mobile is the clear leader and has been for several months in terms of performance,” he said, GeekWire reported at the time.

CEO John Legere also scoffed at the RootMetrics results, tweeting, “Congrats to our competitors—you guys really knocked it out of the park on that report, LAST year when the tests were done.”

RootMetrics followed up with data collected in the first half of 2014. T-Mobile leapfrogged Sprint to take over third place overall but still lagged well behind the top two in reliability, speed, data performance, call performance, and text performance. T-Mobile again called the newest data “weak and outdated” and told Ars that “We think we’ll win in their studies in the future as their data catches up to where our network performance is today.”

Sprint, meanwhile, has conceded that its "network is behind" and that it has to "compete on value and price."

Before today, T-Mobile has argued that its higher-band spectrum combined with its network design gave it an advantage over AT&T and Verizon.

“T-Mobile insists it has a capacity advantage over AT&T and Verizon because of its denser network,” PCMag wrote in June after interviewing Ray. “Since T-Mobile was built with smaller cells to operate over 1700MHz and 1900MHz rather than 700MHz and 850MHz, the company has more cell sites per square mile and can pack more data capacity into each city," Ray said.

T-Mobile advertisements say its "data strong network" has "more data capacity than AT&T or Verizon."

“At T-Mobile we have the most dense network in the nation: we have more cell sites per customer than any other nationwide wireless company, and we’ve concentrated them where it really matters,” Ray wrote in June. “On top of this network we deploy the most data-friendly mid-band spectrum of any carrier in the US. The result: the best LTE performance in the industry.”

T-Mobile is probably doing the best it can with the spectrum it has. But Ham’s statement about T-Mobile needing different spectrum is the one that’s closer to the reality illustrated in independent network tests. While T-Mobile has good outdoor coverage in numerous big cities, it still has problems covering the insides of buildings and rural America. Unless T-Mobile gets a lot of low-band spectrum, it’s going to have a hard time matching the networks of its biggest rivals.