New Interference Test Results Create Setbacks for LightSquared

[Satellite News 06-15-11] LightSquared revealed early results of tests it has been required to undertake by the U.S. Federal Communications Commission (FCC), which show that the network’s hybrid ground- and satellite-based antennas could interfere with GPS and other signals.

            The testing, which was supervised by the U.S. National Coordination Office for Space-Based Positioning produced results that could be a setback for LightSquared, as it has been charged to ease fears and disprove claims from satellite navigation systems manufacturer Garmin and others in the satellite-guided navigation industry that the network’s infrastructure poses a threat to GPS devices. LightSquared is also trying to settle the issue to advance its negotiations with Sprint-Nextel.

LightSquared’s satellite beams utilize the 1525 to 1559 MHz frequency range, which is next door to the GPS range of 1559 to 1610 MHz. While the National Coordination Office’s results confirmed that interference occurred, the organization also said the science was not yet clear on the extent of the radio interference.

            LightSqured Vice President Jeff Carlisle said that the tests indicated that his company’s technology could interfere with other signals, “at some frequencies and power levels, however, adjustments could be made to safely bring the service to market. There are still ways we can co-exist.”

            Trimble Navigation spokesman James Kirkland was much more blunt about the results. “There is no viable technical fix,” Kirkland said in a June 15 press release from Save Our GPS.

            The LightSquared GPS issue began in January, when Garmin engineers filed a report with the FCC claiming that LightSquared’s 4G LTE interference would result in GPS dead zones across the United States. The report’s authors, Scott Burgett and Bronson Hokuf, told the FCC that the stronger signals created by the LightSquared mobile network base stations and the SkyTerra-1 satellite would "seriously limit GPS reception, causing widespread GPS jamming and depriving vast areas of the United States of GPS coverage.”

At the time, LightSquared had just received a conditional green light from the Federal Communications Commission to build a network that toggles between earthbound cell towers and satellite receivers. The combined ground-space network could theoretically deliver high-speed signals to mobile devices and give coverage to almost every nook and cranny of the United States. LightSquared plans to wholesale the service to carriers such as Sprint and electronics makers.

But FCC approval depends on further scientific study to make sure the LightSquared network won’t jam other signals. It has been assigned a little-used frequency that cell phones haven’t touched before. That frequency borders on, and runs the risk of bleeding into, wavelengths set aside for GPS signals. In March, LightSquared formed a working group with the U.S. Global Positioning System Industry Council (USGIC) to study potential interference problems the 4G LTE terrestrial-satellite network might pose on GPS systems.

“LightSquared can still make changes without destroying the economics of our network, and we still expected to meet an FCC mandate to deploy a service that reached 100 million Americans by the end of 2012,” Carlisle said.