LightSquared Says it Can Fix GPS Interference Problem

LightSquared says it has a solution to the problem of interference with Global Positioning System (GPS) receivers that will allow LightSquared to proceed with its business plan. 


LightSquared says 99.5 percent of U.S. GPS receivers will be interference-free, while there are technical solutions for the other 0.5 percent Of GPS receivers. 


One of LightSquared’s 10-MHz blocks of frequencies poses interference to many GPS receivers, and happens to be the spectrum LightSquared originally hoped to use to launch it service initially. 

LightSquared says it can use another 10-MHz block of the spectrum lower on the spectrum band and located further away from the GPS frequencies, greatly reducing the risk for interference. That move requires negotiations with Inmarsat, the satellite company that controls the alternative block of spectrum in the L Band, but LIghtSquared says it has such agreeement. If I understand correctly, that means shifting to the left hand red frequencies, rather than the right hand red frequencies, as illustrated in the first chart. 


See http://www.lightsquared.com/press-room/press-releases/. 


The generic problem is that radio signals, even when carrying digital information, are analog sine waves. As the second chart shows, a signal on a center frequency also emits lesser amounts of energy off frequency. If LightSquared shifts its frequencies away from any of the GPS center frequencies, it will reduce the amount of potential interference. 


LightSquared also says it will modify its Federal Communications Commission license to reduce the maximum authorized power of its base-station transmitters by over 50 percent. This move will provide additional protection to GPS receivers. 


LightSquared believes it still will have enough spectrum to serve its customer base for the next several years.


See also  http://www.engadget.com/2011/06/20/lightsquared-announces-solution-for-gps-issue-says-lte-networ/.