DOD, DOT slam FCC over GPS interference concerns

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The US Department of Transportation and Defense Department on 25 March issued a strongly worded letter to the Federal Communications Commission (FCC) expressing concern over elements of an ongoing analysis on the potential effects on GPS of a newly approved broadband system.

FCC in January granted conditional approval of a L-band satellite-based broadband system to be deployed by wholesale provider LightSquared. Much of the aerospace industry says the network, which includes 40,000 transmitters that will rebroadcast the L-band signals at high power, will have significant interference effects on terrestrial and airborne GPS signals that operate in an adjacent frequency band. The aerospace industry had recommended that the approval process be based on the notice of proposed rulemaking process, a lengthy but thorough process with opportunities for public input.

The conditional approval requires that the FCC determine "that the harmful interference concerns have been resolved" before the network goes operational later this year, a determination the agency plans to make based on industry-led analyses to be completed by mid-June.

Meanwhile LightSquared is moving forward with agreements with broadband providers to use the new service. On 22 March, the company announced a roaming agreement with wireless provider Cricket. Caveats in the "forward-looking statements" section of the announcement do not include a mention of the successful resolution of GPS interference concerns.

The letter to FCC chairman Julius Genachowski from deputy DOT secretary John Porcari and deputy DOD secretary William Lynn opens with criticism of the interference analysis, which LightSquared is responsible for delivering. "First, DOD and DOT were not sufficiently included in the development of the LightSquared initial work plan and its key milestones," say Porcari and Lynn.

"We are concerned with this lack of inclusiveness regarding input from federal stakeholders. In particular, active engagement with DOD and DOT, the national stewards and global providers of [GPS], is essential to protect this ubiquitous defence, transportation and economic utility as the [work group] proceeds."

The agencies are also concerned that the FCC did not ask for a consensus opinion from the group at the conclusion of the analysis, nor did it "provide guidance regarding how differing technical viewpoints" from federal and private sector manufacturers and users will be reconciled.

"DOD and DOT need to understand how differing conclusions and recommendations developed during the [work group] process that could affect national security and transportation safety will be addressed," the letter reads.

The letter concludes with the agencies "strongly" advising the FCC to perform a "comprehensive study of all the potential interference" issues to GPS, an effort industry sources say is not possible in the short timeframe allowed for by the FCC's conditional approval to LightSquared.

The FCC has not yet responded.