While the FCC’s efforts to release more millimeter wave spectrum are all fine and dandy, T-Mobile is concerned that auctioning off spectrum in a piecemeal fashion is not the best way to go about it, and the company is reiterating calls to combine millimeter spectrum bands into one big auction.

T-Mobile executives met with FCC staff this week to discuss their concerns. The “uncarrier” recently announced plans to deploy 5G infrastructure in 30 markets this year using both 600 MHz and millimeter wave spectrum.

Specifically, T-Mobile suggests that the 37 GHz, 39 GHz and 47 GHz bands be combined with the 24 GHz band to foster competition. Preferably, the FCC would throw the 28 GHz band in that auction as well, but if not, T-Mobile argues there’s no reason the FCC could not conduct two simultaneous auctions, one with 28 GHz and the other with multiple bands.

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Even though equipment manufacturers have been focused on the 28 GHz and 39 GHz bands, T-Mobile sees little opportunity for acquiring much 28 GHz spectrum because Verizon already has 76% of it in the top 50 markets, leaving T-Mobile with 12% and the “other” category with just 10%, according to T-Mobile’s ex parte filing (PDF). That leaves just 2% of the 28 GHz spectrum available for auction in the top 50 markets.

“With the limited amount of spectrum left in 28 and 39 GHz bands, auctioning only those bands will further entrench Verizon and AT&T at the expense of competition,” T-Mobile stated. In the 39 GHz band, Verizon holds 46% in the top 50 markets while AT&T holds 30%, leaving 22% up for auction in those markets.

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A familiar theme in T-Mobile’s comments has been to auction off all the available bands as soon as possible. The reasoning, in part, goes as follows: If the commission announces that it plans to auction the remainder of the millimeter wave bands, then standards-setting organizations and others will direct attention to technology development in those bands.

However, if the commission auctions only the 24 GHz band, where there has been little product development, it will further entrench the licensees that hold 28 GHz and 39 GHz spectrum—that is, Verizon and AT&T—where product development has already occurred.

Interestingly, rival AT&T also has urged the commission to adopt auction rules for one single auction involving the 24 GHz, 28 GHz, 37.6-40 GHz and 47 GHz bands, saying it’s critical to maintain 5G leadership in the U.S. AT&T also argues against imposing spectrum caps on millimeter wave bands.

Meanwhile, T-Mobile is advocating (PDF) for coexistence in the 32 GHz band between 5G operators and the radio astronomy community. Its analysis shows that the relatively small number of radio astronomy sites that use spectrum next to the 32 GHz band can be fully protected without significantly impairing use of the spectrum for mobile broadband.

Indeed, the National Radio Astronomy Observatory (NRAO), along with sister observatories Green Bank Observatory and the Long Baseline Observatory, operates most of the U.S. radio telescopes that stand to be affected by 5G mobile services. NRAO submitted comments in February pointing out some problems it saw with T-Mobile’s proposition, but T-Mobile says they both reached the same conclusion—that 5G deployments and radio astronomy can coexist in the 32 GHz band by adopting exclusion zones around radio astronomy sites.