On Monday evening, Re/code wrote about the complicated set of rules that the FCC's wireless bureau is hoping will be adopted for the TV spectrum auction that will take place in 2015. According to these restrictions, carriers with lots of spectrum like AT&T, Verizon, and Sprint, could be prohibited from bidding on up to one-third of the auctioned-off spectrum in a given area, at least when the bidding in that area reaches a particular price.

The auction rules would dictate how many licenses a wireless company could purchase by creating two classes of spectrum licenses: restricted and unrestricted. According to Re/code, all companies would be allowed to bid on the available spectrum at first, generally in blocks of 5 MHz. Then if the bidding reaches a “threshold price,” 30 MHz of the spectrum in that market would be reserved for smaller competitor companies.

Additionally, the FCC is looking to adopt new “spectrum screens” which would limit how much spectrum a wireless carrier could hold in a certain market. Under the rules, if a carrier tried to buy up more than a certain amount of spectrum in the market, that would trigger extra scrutiny at the FCC before the deal could go through. The upcoming availability of spectrum, combined with new rules for who can own it, has garnered a lot of attention.

The rules that Re/code's sources spoke about aren't set in stone yet and still need to be shown to other members of the FCC to get their approval. But the FCC's wireless bureau may be trying to strike compromises before the proposal has even drawn objections. Re/code explains the tension:

The proposal represents an effort by Wheeler’s aides to meet two broad, conflicting goals of the auction: Raise as much money as possible (by selling licenses to wireless giants AT&T and Verizon) while increasing competition in the wireless market (by selling licenses to smaller carriers that need more prime airwaves to compete for subscribers).

The TV spectrum auction has been in the works for many years and will involve TV stations voluntarily giving up some of their high-value broadcast spectrum in exchange for a check from the auction proceeds. Participating stations will either have to go off the air, or they can share spectrum with another station. That arrangement is currently being tested in Los Angeles with some success, although at the National Association of Broadcasters conference last week, attendees seemed reluctant to embrace the idea of sharing their airwaves.

The spectrum auction is also getting a lot of attention because it's likely the last of its kind for a while. “I caution you that the incentive auction opportunity is going to happen about a year from now and is unlikely to happen again,” Wheeler told an audience of broadcasters at the NAB conference.

Re/code notes that the FCC estimates that it will have about 85 MHz of spectrum in the 600 MHz band to auction off in urban areas, and possibly more in rural areas.

Critics also say that the auction and its rules will only be a partial solution to an underlying problem: that two cell carriers dominate the US market, and their competitors are largely priced out of the game. While smaller carriers will have some help in securing spectrum with the new “restricted license” designation, Public Knowledge Senior Staff Attorney John Bergmayer pointed out that competitors like Sprint might get cut out of bidding for restricted licenses because it owns a lot of high-band spectrum, which can't penetrate walls like the more valuable, low-band 600mHz spectrum can.

“[The FCC counts] all megahertz as being equal,” Bergmayer explained. “Sprint, after it bought Clearwire, has tons of spectrum, but it's not very useful. There's only so much that, say, T-Mobile can do with wild crazy price cuts and promotions. At a certain point if they don't have the network for customers, it's going to hurt them.”

One industry source told Ars that Verizon and AT&T currently account for about 80 percent of the low-band spectrum holdings. “There's a widespread recognition in the wireless industry that this current screen is broken; [the screening process] is not triggered in transactions that clearly do cause a threat to consumers,” the source, who asked not to be named, told Ars.

For now, though, there's little that interested parties can do besides adopt a holding pattern until the FCC's official rules come out, which is expected to be in mid-May. The FCC will have to vote on the rules as well, so revisions are likely in order.

Update: Ars has learned that the FCC is considering reserving up to 30 MHz of spectrum in urban markets for small carriers. This story originally said that the commission would reserve up to 30 percent of the available spectrum.