Failure by GPS manufacturers to utilize recommended filtering techniques is the primary reason for the industry having such significant interference projections with LightSquared’s planned terrestrial LTE network that would utilize nearby spectrum, according to a recent LightSquared filing with the FCC.

“Had the GPS industry complied with [Department of Defense’s] recommended filtering standards for GPS receivers, there would be no issue with LightSquared’s operations in the lower portion of its downlink band,” Jeff Carlisle, LightSquared’s executive vice president for regulatory affairs and public policy, stated in the FCC filing that was submitted last week.

Instead of using the DOD standard — a technique that effectively requires only a 4 MHz guard band — GPS manufacturers opted “to take a calculated risk” and build products that requires a 34 MHz guard band, Carlisle said during an interview with Urgent Communications.

While there are more than 400 million GPS devices in use today, LightSquared’s offer to use only spectrum that is farthest away from GPS operations would ensure that no GPS devices would have to be replaced in all but a few cases, Carlisle said.

“The one subset of GPS receivers that are not completely addressed by this proposal are high-precision devices, which are used for agriculture, surveying, construction,” he said. “These are very highly sensitive devices that look all the way across our band. So, it doesn’t really matter where we move; they’ll still have the potential of seeing our signal.

“For 400 million devices, you’re solving the problem without the need for any additional filtering in the devices. For the much smaller number — 500,000, or much less than 1% — you have to do additional work on those, but the problem is solvable.”

With this in mind, LightSquared is willing to absorb all of the research-and-development costs needed to produce filtering products that will address the interference concerns, Carlisle said.

“If we’re absolving them of the responsibility for the research-and-development cost, that eliminates a significant amount of the incremental cost of adding these filters to the devices,” he said.

Mobile wireless consultant Andrew Seybold said he disagrees with LightSquared’s contentions, particularly the criticism of the filtering used in commercial GPS devices that were designed years ago.

“When people design systems, they look at the spectrum next to them and they design with regard to what’s operating next to them,” Seybold said. “What was operating next to them were satellite uplinks and downlinks, which is a totally different situation [than a terrestrial LTE network].”

Carlisle said GPS industry officials have known about LightSquared’s terrestrial-network vision for several years but only began expressing opposition to the plan recently.

A satellite provider, LightSquared received FCC approval to build a terrestrial LTE network on the same spectrum it uses for satellite operations — airwaves that are located near the spectrum used for GPS, which has generated considerable controversy within the GPS industry and several federal government organizations.

LightSquared does not plan to use the LTE network to compete directly with established carriers such as Verizon Wireless and AT&T Mobility. Instead, the company plans to operate as a wholesale partner to smaller carriers, allowing them to be more competitive with the carrier behemoths.

“I want to be clear that I’m not opposed to allowing somebody to sell wholesale LTE, so the smaller carriers can become involved — but not on that spectrum,” Seybold said

Seybold said he believes LightSquared should conduct testing of a 50-site LTE system to demonstrate that its terrestrial networks will not interfere with GPS operations before being allowed to deploy 4G terrestrial technology on a broader scope.