June 13, 2011 How Much Will it Cost LightSquared to Fix GPS Interference Problems?
By Gary Kim Satellite Spotlight Contributing Editor http://satellite.tmcnet.com/topics/satellite/articles/185422-how-much-will-it-cost-lightsquared-fix-gps.htm Sometime on June 15, 2011, we will find out what LightSquared (News - Alert) engineers believe must be done to comply with non-interference rules that the Federal Communications Commission says must be complied with, before LightSquared will be permitted to start building its terrestrial Long Term Evolution network. In all likelihood, the report will say that filtering techniques are available that will solve the problem of interference with GPS receivers. But the big issue will be the cost of doing so. LightSquared expects to operate as a wholesale provider of LTE (News - Alert) capacity, so the cost of its network, and the speed with which it can be built, have always been concerns, especially as rivals accelerate their own LTE network builds. FCC (News - Alert) Chairman Julius Genachowski has stated, obviously, that the FCC will not allow LightSquared to launch commercially until GPS interference concerns are resolved. Separately, two House Transportation and Infrastructure subcommittees will conduct an oversight hearing June 23 to discuss potential impacts on U.S. aviation safety in light of pending government action that may affect GPS reliability. The Federal Communications Commission (FCC) is considering an application to build out nationwide broadband Internet infrastructure, which would allow high-power Internet broadcast stations to be built across the country broadcasting on the spectrum neighboring the low-powered GPS signal, according to a June 10 government advisory. Genachowski’s June statement effectively rescinds the FCC’s January 2011 waiver to LightSquared for operation of its network on the L band, which is adjacent to the spectrum reserved for GPS. Sen. Charles Grassley (R-IA) began raising spectrum interference concerns this past April. Initial testing of GPS receivers confirms aircraft navigation systems will experience significant jamming from thousands of broadband-wireless transmitters planned to be deployed across the United States. The tests were conducted to determine the susceptibility of GPS receivers to interference from the high-power terrestrial transmitters LightSquared plans to deploy. All GPS receivers tested by the National Position, Navigation and Timing Engineering Forum (NPEF) were affected by the high-power transmissions, FAA’s Deane Bunce, NPEF co-chair, told a meeting in Washington. The Senate and House also expressed GPS interference concerns in bipartisan letters to the FCC. In May, 34 senators signed a letter to the FCC, which was similar in content to the letter sent later in the month by 66 House members (49 Republicans and 17 Democrats), which stated, “We request that the Commission only approve LightSquared’s waiver if it can be indisputably proven that there will be no GPS interference.” The FCC granted its integrated-service rule waiver this past January for LightSquared to operate a terrestrial-only LTE network on the L-band satellite spectrum. The company acknowledged at the time that its LTE network might interfere with GPS signals, but assured the interference could be addressed satisfactorily with technological fixes. In a recent interview, Nigel Wright, vice president of wireless for testing and measurement company Spirent (News - Alert), said that the working group will most likely identify some kind of filter that prevent GPS interference or bring it down to manageable levels. The question is how expensive such a filter or other fix would be, Wright said. In principle, what LightSquared needs are more-effective band-stop filters that will attenuate radio frequency energy from bleeding beyond the authorized bounds of the LightSquared bands. Engineers know how to build such filters. The only issue is what custom filters of this type will cost.
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