The Federal Communications Commission has declared victory after the release of an engineering study on whether its proposed free and smut-free broadband service will harm mobile phone use in other bands. "We will be able to move forward with broadband services as proposed by FCC Chair Kevin Martin without causing undue interference to licensed users of adjacent spectrum," Commission spokesperson Rob Kenny told Ars Technica on Friday. "This is good news for everybody interested in bringing free broadband to those without access to the Internet."

As Ars has reported, on Friday, September 5, the FCC's Office of Engineering and Technology concluded a battery of wireless interference tests to determine whether the FCC's proposal is technically doable. The Commission is considering auctioning off the AWS-3 (2155-2180 MHz) band for a national, free broadband service that filters out smut. The winner of the sale would be required to roll out the program over 10 years and pay a small portion of its revenue each year to the United States Treasury.

But the big wireless companies, led by T-Mobile, charged that the service could cause interference in the nearby AWS-1 band, where the firm paid billions for spectrum in 2006. The company asked for a delay in the proceeding pending a series of interference tests.

Following the experiments, a T-Mobile official declared that they "verified there would be widespread, harmful interference to customers of AWS-1 operators, including T-Mobile's customers, from the adjacent AWS-3 band under the FCC's proposed rules." But that does not appear to be what the Commission's OET has concluded in its report.

The summary says that "AWS-3 devices could operate at a power level of up to 23 dBm/MHz equivalent isotropic radiated power (EIRP) and with out-of-band emissions (OOBE) attenuated by 60 + 10*log(P) dB without a significant risk of harmful interference." That's pretty similar to what the FCC originally proposed in its original Further Notice of Proposed Rulemaking outlining the plan.

The report also adds that in the past the FCC has "adopted less stringent OOBE standards under flexible service rules whereby the licensees and industry work together cooperatively to manage potential interference."

Needless to say, the latest news was warmly received by M2Z Networks, the biggest booster of this proposal and the most likely bidder for the service. M2Z CEO John Muletta told Ars that the "public interest has been held hostage for six months," as a result of T-Mobile's and AT&T's "unfounded claims of interference to disguise their intent to prevent the introduction of new broadband competition in the AWS-3 band."

"We think that now is the time to make a decision," Muletta added. "This will really change the opportunities for broadband."

But T-Mobile's circumspect response to the OET's conclusions suggests that the company isn't throwing in the towel yet. The company's regulatory affairs Vice President Kathleen Ham told us that the firm "will read the report in detail to determine if [the OET has] correctly evaluated the extensive record for multiple parties that have expressed concern about interference. Given the importance and complexity of these technical issues, the FCC needs to provide for sufficient time for comment on the report before any FCC action on these rules."

The OET's report will now be added to the proceeding record, and further comments will be considered. Among other sticky questions to be grappled with is the First Amendment constitutionality of the FCC requiring the service to be filtered for smut. Civil liberties groups have emphatically told the agency that the proposal as outlined will not survive court scrutiny.

The current proposal requires an "always on" network-based filtering mechanism. The FCC's Kenny says that Commission Chair Martin is willing to consider proposals to let adults opt-out of the filter, but wants the essence of the plan to be "mindful of the fact that we need to protect children from questionable content."