LightSquared blames GPS industry for interference, network remains in limbo

LightSquared, along with a technical working group of GPS industry experts, submitted its final report to the FCC on potential GPS interference caused by its planned wholesale LTE network. However, the fate of the company's network remains uncertain, and a resolution on the issue is likely weeks away, if not longer.

The company also filed a separate report with the FCC outlining its proposed plan to mitigate the GPS interference concerns. The plan was first announced June 20. In that report, LightSquared placed the blame for the current state of affairs on the GPS industry, allegations the GPS industry said are false.

According to FCC spokesman Neil Grace, there will now be a 30-day public comment period on the technical working group's report and a 15-day reply period. While this is going on, the FCC's Spectrum Policy Task Force will review that report and LightSquared's new plan to try and determine whether LightSquared can proceed with its network deployment.

Jim Kirkland, vice president and general counsel to Trimble, and a member of the Coalition to Save Our GPS, which is opposed to LightSquared's plans, said that the coalition wants the full commission vote on any proposed solution. Grace said a vote by the full commission is possible.

In a separate filing from the technical working group's report, LightSquared said the GPS industry bears responsibility for the current impasse. "Despite the commercial GPS device industry's best efforts to rewrite the record and obfuscate the nature of the problem, the simple fact remains that GPS receivers do not adequately reject base station transmissions in the adjacent band," LightSquared said in its filing. "The receivers have been designed, sometimes deliberately, with the assumption that there would be no adjacent-band transmissions. While the commercial GPS device industry has offered many justifications for its design decision--justifications that are not supported by the plain facts of the FCC record or, for that matter, by the FCC--it is inescapable that this is the source of the problem of overload of GPS devices."

Kirkland and other members of the coalition disagree with LightSquared's arguments. In a conference call with reporters, Kirkland said that because LightSquared's spectrum was originally designed for satellite transmissions with an ancillary terrestrial component, GPS receivers were designed against those kinds of transmissions, and not transmissions from base stations. "Now they're saying we should have understood the rules were going to change later on, and that's just revisionist history," he said.  

The voluminous technical working group report found that LightSquared's network, as currently designed, cause significant interference with GPS receivers, especially in the upper portion of LightSquared's L-band MSS spectrum. However, LightSquared and the GPS industry remain at odds over whether there can be a technical solution to the issues, and each side continues to blame the other for the state of affairs. LightSquared contends that filtering technology can mitigate GPS interference concerns, but the GPS industry maintains that such filtering technology does not yet exist and was not tested as part of the report.  "If there are no filters available today to support this, then there's nothing the GPS industry could have done in the past to make this compatible," Kirkland said.

At issue is a waiver the FCC granted LightSquared in January to allow LightSquared's customers to provide terrestrial-only service in its L-band spectrum, which had previously been allocated mainly for satellite use with an ancillary terrestrial component. The spectrum sits adjacent to frequencies used by GPS receivers and the GPS community is concerned that the powerful signal produced by LightSquared's base stations will knock out GPS.

In its separate report, in which it criticized the GPS industry, LightSquared formally presented its plan to mitigate interference to the FCC. Under the proposed solution, the company will no longer launch its network in a 10 MHz chunk of its spectrum that tests showed caused interference with many GPS receivers. Instead, LightSquared said it recently inked a deal with Inmarsat, the satellite firm that controls the lower spectrum band, which will allow LightSquared to get access to the lower spectrum band--the channel from 1526 to 1536 MHz--sooner than it initially planned. LightSquared also said it will modify its FCC license to reduce the maximum authorized power of its base-station transmitters by more than 50 percent. However, representatives from the GPS industry said LightSquared's proposed solution will still cause significant interference and has not been adequately tested.

In the meantime, LightSquared said it will not use the spectrum it originally planned to use for the launch of its network. The company said it will work closely with the FCC and the National Telecommunications and Information Administration, as well as the relevant U.S. government agencies and commercial GPS users, to explore "mitigation possibilities and operational alternatives" that will allow LightSquared to expand its business into the contested spectrum.

For more:
- see these links to the FCC report (PDF) (Part 1) (Part 2) (Part 3) (Part 4) (Part 5)
- see this LightSquared release
- see this LightSquared filing (PDF)
- see this Coalition to Save Our GPS release

Related Articles:
U.S. officials call for more LightSquared GPS testing
LightSquared plans to submit GPS interference report by June 29
LightSquared reworks network plans to avoid GPS interference
Sprint consummates LTE network-sharing deal with LightSquared
LightSquared's GPS interference plan leaves more questions than answers
LightSquared gets extension on GPS report, inks deal on Sprint network sharing