gps-networkGlobal Positioning System receivers remain wary of the plan by 4G network provider LightSquared to create a wireless broadband network to serve every nook and cranny of the U.S.

In testimony June 23 before a House subcommittee, opponents of the LightSquared system said it would endanger the GPS navigation systems that aircraft and ships depend upon. “LightSquared’s proposal is sort of like driving a lawn mower in a library,” Philip Straub, a vice president of GPS manufacturer Garmin, reportedly testified to a joint House subcommittee.

The testimony came just a few days after LightSquared CEO Sanjiv Ahuja announced a technical fix that, he said, would “resolve 99.5 per cent of the GPS receiver problems.” The remaining half a percent, according to Ahuja, are “precision GPS receivers” used on farm equipment from signals transmitted by existing satellites operated by LightSquared.

He said LightSquared would work with the commercial manufacturers of the agriculture equipment makers to resolve those interference issues.

In response to Straub’s lawn mower comment, LightSquared VP Jeffrey J. Carlisle reiterated that his company does not pose a threat to vital maritime and aeronautical communications and navigational tools. “LightSquared has no intention of operating a system in any way that will compromise government or commercial aviation operations,”

However, Margaret T. Jenny, president of the Radio Technical Commission for Aeronautics, echoed Straub’s alarm. She is reported to have testified to the committee that “the impact of the LightSquared upper-channel spectrum deployment is expected to be complete loss of GPS receiver function.”

Jenny went on to say that the impact would be less if LightSquared restricted its operations to the portion of the bandwidth farthest from the GPS.

That is precisely what LightSquared has elected to do, Carlisle responded. A frequency shift following tests that showed the conflict in frequencies immediately adjacent to GPS.

“The vast majority of GPS receivers look only at that portion of LightSquared’s spectrum that is immediately adjacent to GPS,” he said. “Our operation in the lower portion of our band, furthest from GPS, does not cause interference. Operation at the far end of the spectrum will avoid overload for 99 percent of the receivers, including those used for aviation and maritime operations.”

Another issue is who will incur the cost of modifying GPS equipment if such modifications are needed to make the two systems compatible. The GPS industry is already on record as demanding that it shouldn’t have to bear any of the burden of accommodating LightSquared if a solution to the interference is actually found.

Virginia-based LightSquared will begin rolling out its national 4G broadband network later this year, subject to approval by the Federal Communications Commission.

About The Author

LBA Group

LBA Group, Inc. has 50 years of experience in providing RF asset solutions and risk management for industrial and telecommunications infrastructure assets. The group is comprised of LBA Technology, a leading manufacturer and integrator of radio frequency systems, lightning protection, and EMC equipment for broadcast, industrial and government users worldwide; the professional engineering consultancy Lawrence Behr Associates, and LBA University, providing on-site and online professional training. The companies are based in Greenville, N.C., USA.

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