Would-be 4G wholesale provider LightSquared says it's still on track to launch initial Long Term Evolution (LTE) markets in the U.S. by the end of 2011 despite renewed interest from some government bodies about the potential for interference to GPS receivers from the new network.

The Harbinger Capital Partners LP -backed venture has previously said it wants to launch its first LTE markets in the third quarter of 2011, with up to nine markets expected to be active by the end of the year. (See LightSquared Confident in Q3 Launch Schedule.)

"Our launch is still on track. We're looking for a launch by the end of the year certainly," Jeff Carlisle, executive vice president for regulatory affairs and public policy at LightSquared, told Light Reading Mobile during a call Thursday.

LightSquared's goal is ambitious, as it plans to build out the first wide-scale hybrid LTE terrestrial and satellite network using L-Band spectrum. In return for the use of 59MHz of the 1.6GHz spectrum, the Federal Communications Commission (FCC) has mandated that the operator must cover 100 million Americans by the end of 2012, 145 million by the end of 2013, and 250 million by the end of 2015. (See Harbinger Hatches LTE Challenger in US.)

The 1.6GHz L-Band, however, sits adjacent to frequencies used by global positioning satellites (GPS) to broadcast triangulated location data to earth-bound receivers. That data is used by the U.S. military, the Federal Aviation Authority (FAA) and emergency services as well as many mobile mapping applications.

The worry is that the GPS receivers will pick up interference from the L-Band network, since signals from a terrestrial LTE cell site -- particularly in a dense urban environment with multiple radios -- will be much stronger than the signals the receiver is tuned to grab from satellites. That interference could disrupt GPS services.

The FCC has already mandated that LightSquared works with the United States Global Positioning System Industry Council (USGIC) to form a technical working group to report back on any interference issues discovered and fixes required. The initial report has been filed, with another due on April 15. The FCC wants the final report by June 15. (See LightSquared Files First Report to FCC.)

The speed of this process clearly has some in Washington worried. On Wednesday it emerged that the Deputy Defense Department Secretary William J. Lynn and Transportation Department Deputy Secretary John Porcari sent a joint letter to the FCC on March 25 calling for a "comprehensive review" of the GPS issue. (See Pentagon Calls Interference on LightSquared.) If LightSquared's Carlisle is worried by the additional government interest, however, it doesn't show. He tells LR Mobile that the technical group looking at the potential issue now has representatives from the DoD, the FAA and NASA onboard.

"All have had valuable input," Carlisle says.

Nonetheless, although Carlisle says the group is "making good progress," he admits "there's a lot of work left to be done." Namely, the group has to figure out which categories of "legacy receivers" are affected by the LightSquared network, if any, and establish how these receivers are being used.

"We really won't know what kind what kind of mitigation is necessary without a datasheet," Carlisle says. The group has selected independent testing firms and is "close to starting testing," according to the LightSquared representative.

At least one testing firm tells us that interference could be an issue, particularly in cities like New York where GPS systems can already struggle to triangulate location data because skyscrapers block the signals. In this situation, stronger RF signals from multi-radio L-Band cell-sites in the adjacent band could be an issue for receivers looking for weaker communications from satellites in orbit around the earth.

"Theoretically, that possibility definitely exists," Nigel Wright, vice president of wireless for Spirent Communications plc told LR Mobile recently. "GPS signals are weakest in the areas where you're most likely to have the greatest concentration of base stations."

Spirent is working on test equipment that could prove the interference issue one way or the other. For the moment, Wright says he'd be "foolish" to predict what the results of any tests may be before seeing any hard data.

Others, however, are much more vocal about what they perceive as the threat to critical GPS infrastructure. The coalition to Save Our GPS was launched on March 11 and claims representatives from a range of industries, including aviation, agriculture, transportation and GPS equipment makers and service providers. The group worries that the 40,000 base stations that LightSquared plans to eventually deploy will mean the equivalent number of "dead spots" in GPS services.

LightSquared's Carlisle says the fledgling operator is "cognizant" of opposition to its plans, but doesn't believe the deployment of the earthbound LTE network will be slowed while it waits for the results of the GPS testing.

"There are any number of things that can be done in the meantime," Carlisle explains. LightSquared has been developing tower agreements "for many months" while working on zoning agreements, he says.

Meanwhile, the operator has been co-operating with its network equipment vendor Nokia Networks on completing development of the L-Band-suitable base station it will use in the rollout. Decisions are also being made on what kind of backhaul it will need for the network. (See NSN: We're Still in at LightSquared.)

The FCC mandate means that LightSquared has to keep the pace up whatever happens, Carlisle reminds us: "We've still got to have 100 million covered by [the end of] 2012."

— Dan Jones, Site Editor, Light Reading Mobile