GPS Is Being Threatened
By Joseph Paiva
In January, the Federal Communications Commission (FCC) granted a conditional waiver to LightSquared, a company with ambitions of providing wholesale mobile broadband service. LightSquared has radio spectrum licenses for use in communication satellites and now intends to install up to 40,000 high-powered, land-based transmitters that broadcast in the same band that its communications satellite channels now use. To do this, LightSquared needs approval from FCC to change the way the section of the frequency band allocated for satellite signals is to be used. The conditional waiver already granted allows LightSquared to continue development of the terrestrial network, and it can now broadcast high-powered signals in a section of the band formerly reserved for low-power signals from space.
Unfortunately for GPS, the section of the spectrum, referred to as the L-band, in which LightSquared will provide broadband service is immediately adjacent to the section of the L-band used by GPS. As people listen to their favorite FM radio station as they drive, they may experience interference when another station's transmitter is powerful, or nearby, or both. This is what researchers expect would happen with GPS should LightSquared ever be allowed to go operational. But the problem is much more severe—some estimates put the LightSquared signal at more than one billion times the power of signals from GPS as received by GPS receivers. Are there technical solutions? The fact is that any technical theory at this point is just that—a theory, untested, unproven, and unverified. The laws of physics make solving this problem very difficult. GPS has served us all extremely well for the last 30 years, in part because nearby frequencies have also been preserved solely for space-to-earth communications. Protection of the GPS service for all users has to be the number- one priority in the FCC process.
FCC has mandated GPS interference research. In response, LightSquared, the US GPS Industry Council, and others, are working on this study. One problem created by the FCC conditional waiver is that LightSquared is able to move ahead with its infrastructure development assuming that viable solutions to the jamming issue will be found. For many users of GPS, theoretical fixes may not be sufficient.
What Can Be Done About It?
Stop FCC from issuing a Final Order in favor of LightSquared and prevent repurposing of the section of the L-band immediately adjacent to that used by GPS.
What Can You Do to Help?
Contact Congress. Members of the GPS survey community who are concerned by the proposal can send letters, e-mails, or faxes or call on their congressional representatives to contact the FCC chairman directly or the chairman of the Senate and House Commerce Committee. You can also voice your concerns about GPS interference by sending comments directly to FCC at fccinfo@fcc.gov. Don't forget to include FCC File No. SAT-MOD-20101118-00239 in your correspondence.
About the Author
Joseph Paiva, PS, PE, is a consultant to the geomatics industry—practitioners, manufacturers, and developers; educator; and writer. Dr. Paiva's experience includes private engineering, surveying, and mapping consulting practice; university educator; developer; and general manager for two leading geomatics products corporations.
