The Coalition to Save Our GPS declared that test data shows “substantial interference to GPS if LightSquared turns on high-powered terrestrial facilities. The data are said to confirm what the industry told the FCC before it granted the waiver, and also confirms that there is no viable technical fix. The joint LightSquared/GPS Working Group report is due June 15, 2011.
LightSquared may very well be forced to use just the lower portion of its 1.6 GHz Mobile Satellite spectrum for terrestrial base stations to avoid interference, says Fierce Wireless. While LightSquared has access to a total of 59 MHz of spectrum, it only has current access to the 1525-1559 MHz band, which is the band next to the GPS bands.
LightSquared intends to propose that it should initially use the lower part of its L-band spectrum, but that GPS users should be required to fit filters so that after a multi-year sunset period, LightSquared would be able to use the full 40MHz of MSS-ATC spectrum in its terrestrial network.
LightSquared will be using part of the L-band downlink frequencies in the 1525-1559 MHz band, while GPS (and GLONASS) operates in the 1559-1610 MHz band. LightSquared already plans to outfit its base stations with filters that cut off the signal at the top of the L-band to keep its signals from leaking into the GPS band. The issue, however, is that most GPS devices don’t have strict filtering at the bottom of the GPS band and therefore could be overwhelmed by the high-power transmissions coming from LightSquared’s terrestrial transmissions.
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