Point of Beginning

Professionals Called to Action on Issue Threatening GPS

February 16, 2011
In January, the Federal Communications Commission (FCC) granted a conditional waiver to LightSquared, a company with ambitions to be in the business of providing wholesale mobile broadband service.

In January, the Federal Communications Commission (FCC) granted a conditional waiver to LightSquared, a company with ambitions to be in the business of providing wholesale mobile broadband service. LightSquared has radio spectrum licenses originally intended 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 the FCC for a change in the way the section of the frequency band allocated for the satellite signals is to be used. The conditional waiver already granted allows LightSquared to continue development of the terrestrial network because they 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 is immediately adjacent to the section of the L-band used by GPS. Most people have experienced trying to listen to their favorite FM radio station as they drive, when another station on a different frequency causes interference, usually because the other transmitter is so powerful, or nearby, or both. This is what researchers expect would happen with GPS should LightSquared ever be allowed to go operational. Only the problem is much more severe-some estimates put the LightSquared signal at more than 1 billion times the power of signals from GPS as received at the GPS receiver. 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. The GPS system has served us all extremely well for the last 30 years, in part because the nearby frequencies have also been preserved solely for space-to-earth communications. Protection of the GPS service for all users has to be the No. 1 priority in the FCC process.

The FCC has mandated GPS interference research. In response, LightSquared, the U.S. 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 the FCC from issuing a Final Order in favor of LightSquared and prevent repurposing of the section of the L-band immediately adjacent to GPS.

So 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, faxes or call upon 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 the FCC at: fccinfo@fcc.gov. Don’t forget to include the FCC File No. SAT-MOD-20101118-00239 in your correspondence.

See more in April’s POB.

Related article: FCC Decision Could Impact GPS Users