Sprint (NYSE: S) and T-Mobile have weighed in on the debate over the so-called “white spaces” spectrum that’s in between frequencies used by TV broadcasters, urging the FCC to license the spectrum for fixed backhaul use. In a letter (PDF link) to the commission, the operators say they need cheaper backhaul alternatives to the special-access connections they buy from incumbent local exchange operators, and that need will intensify as they build out their 3G and 4G networks and consumer uptake of mobile data services increases. As RCR notes, it’s unlikely that this push will get a lot of support from other major US operators, given that AT&T (NYSE: T) Mobility and Verizon Wireless’ (NYSE: VZ) parent companies are the main suppliers of the ILEC special-access lines Sprint and T-Mobile say are too expensive.

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The operators also say that implementing licensed, fixed-wireless services in the spectrum could be done without causing interference to existing TV broadcasts. This plays on the Commission’s earlier findings that test devices from a coalition including Google (NSDQ: GOOG), Microsoft (NSDQ: MSFT), Phillips and others—which want to open the white spaces for unlicensed use—didn’t work as intended and interfered with existing signals. Sprint and T-Mobile contend that requiring licenses for the white spaces would provide a better means for the FCC to protect incumbent operations around the white spaces, and would also allow for for more efficient use of them in rural areas. This debate is far from over, as Google and its cronies say they’ve now got prototypes that work without interference, while an overall scarcity of low-frequency spectrum means corporate interests will continue to press for the FCC to only allow licensed, exclusive access to the white spaces.