LightSquared: Be careful of reading into GPS interference claims

Lynnette LunaJeff Carlisle, executive vice president of regulatory affairs at LightSquared, held a teleconference yesterday and cautioned the media not to jump to conclusions about the various independent tests floating around that warn of his company's potential interference with GPS systems.

"There are going to be a lot of reports of testing, but the important thing is to understand the types of receivers," he said. "It's not sufficient to identify interference and say there is interference. You have to take the step of how it is caused and then fix it."

Indeed, a plethora of reports continue to pop up claiming LightSquared poses problems to various GPS receivers. The latest: RTCA Special Committee 159 released an executive summary of a special report that says GPS aviation receivers would be faced with serious interference from transmissions planned by LightSquared in the upper portion of the 1525-1559 MHz band, where LightSquared plans to operate and is adjacent to the GPS band. RTCA is an organization that writes GPS avionics specifications for the Federal Aviation Administration.  

LightSquared plans to launch wholesale terrestrial services using L-band satellite spectrum, which sits next to GPS spectrum and it must adhere to certain restrictions, which include keeping signals within their assigned frequencies in the L-band.

LightSquared also must work with the GPS sector to test existing GPS-enabled devices to determine what type of interference its transmissions might cause. The FCC has mandated that LightSquared and the U.S. Global Positioning System Industry Council (USGIC) establish a technical working group (TWG) to investigate the issues. A final report is due on June 15 of this year. Carlisle pointed out that the technical working group has tested more than 150 different devices to obtain a broad view of how the systems operate together.

LightSquared has believed for some time that some interference issues will present themselves for highly sensitive GPS receivers such as those used in aviation. Those problems come about because the receivers are actually looking into the L-band.

Yet, the company remains confident that GPS and LightSquared signals can peacefully coexist.

"Let me make one thing clear. Regardless of how the issue has come up and when it was brought up, we have never taken any potential solutions off the table," Carlisle said. "We are open to examining receiver side and transmission side fixes for this. So that is something that is an important point. We are open to talking about it. Really that is how it moves forward and efficient and fair way."

Talking about the fixes may be the easiest part, however. Who is going to pay for any fixes will likely be the complex part. As Carlisle pointed out, the GPS community knew since 2005 that operations could come into the L-band, and the FCC said in its rulemaking proceeding last year that GPS interference mitigation would be the responsibility of both the new entrant and the incumbent in the surrounding band.-Lynnette

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