Martin Harriman, LightSquared's EVP, Ecosystem, Development & Satellite Business delivered a presentation to the Space-based Positioning, Navigation and Timing (PNT) Meeting, briefly showing LightSquared's solution to the problem of base station interference to GPS reception.
The most convincing presentation, however, came from Javad Ashjaee, whose company came up with a fix for the interference. The American Surveyor describes Javad's presentation in the article Javad Ashjaee's LightSquared Solution Presentation at the PNT Meeting.
There are actually two issues with LightSquared interference to GPS. One is overload interference to the signals from the GPS satellite. That affects everyone, and LightSquared has come up with a temporary fix of avoiding spectrum use adjacent to the GPS band. The other interference issue is with the correction signals high-precision GPS receivers need to deliver results accurate enough for agriculture, construction and other applications. The fix here is to use the LightSquared network to provide the correction signals, rather than the current dedicated satellite link.
Filters are also part of the solution, and The American Surveyor article describes Ashjaee's approach to the problem. One is a $30 ceramic filter in the LNA, and the rest are four tiny 24-cent surface acoustic wave (SAW) filters. Ashjaee said his company will begin manufacturing "LightSquared-integrated" receivers in May 2012 using the LightSquared network for high-speed communication.
The PNT meeting did not cover consumer devices, only expensive, high precision GPS units, and it remains unclear how the problem of LightSquared interference to these receivers will be resolved if LightSquared were to use its entire 1,5 GHz MSS allocation for terrestrial communications.