GPS makers trade barbs with LightSquared

In the wake of test results, both sides said the other causes interference

A GPS industry group dismissed mobile startup LightSquared's alternative proposal for an LTE network that would operate on frequencies close to the GPS band, saying the company hasn't presented any clear plan to reduce interference.

LightSquared formally submitted its new proposal to the U.S. Federal Communications Commission on Thursday, along with test results that showed severe interference with GPS (Global Positioning System) receivers when an LTE (Long-Term Evolution) network was using some adjacent frequencies. LightSquared blamed GPS device makers for the problem, saying they did not build in strong enough filters.

The Coalition to Save Our GPS struck back immediately in a Thursday morning conference call, saying LightSquared's plans violate the laws of physics and can't be made to work in harmony with GPS.

"We do not see a solution other than putting these operations in a band where they won't interfere with GPS," said Jim Kirkland, vice president and general counsel of GPS equipment vendor Trimble, on the conference call.

LightSquared wants to supplement a satellite-based mobile service covering the whole U.S. with a faster LTE network that would reach 100 million people by the end of 2012. In January, the FCC granted the company a conditional waiver to operate that LTE network in spectrum bands that so far have been used for satellite services, which transmit at lower power.

The months of test results that were disclosed on Thursday, as expected, showed that GPS receivers were hobbled by LTE signals in the upper part of LightSquared's spectrum, which is directly below the GPS band. The carrier's alternative plan would leave that upper band alone while service is launched on lower frequencies, which LightSquared said won't affect 99.5 percent of all GPS receivers. The company said it also would transmit at lower power.

The FCC has put both documents out for public comment for 30 days, followed by 15 days for responses. At some point after that, the FCC's International Bureau, which regulates the satellite band, will issue an order on how LightSquared can proceed. That order could be appealed to the full commission.

"We will not permit LightSquared to begin commercial service without first resolving our concerns about potential harmful interference to GPS devices. Nevertheless, our nation cannot afford to let spectrum go underutilized," FCC spokesman Neil Grace said in a written statement.

The GPS group said LightSquared's proposal came too late for adequate testing to support the claim that most receivers wouldn't be affected, and said the plan for lower power needed more detail.

But the conflict goes deeper than that. LightSquared and the companies represented by the coalition, which include Garmin International, John Deere, FedEx, and the Aircraft Owners and Pilots Association, disagree about the fundamental cause of the interference. The Coalition said GPS receivers have to be sensitive enough across a wide band to pick up faint satellite signals, so they are overpowered by very strong signals even if they are in other frequency bands.

"There's no way you could design a receiver in order to block out a billions-of-times-stronger signal in that next band. It's just not possible," Trimble's Kirkland said.

LightSquared's deployment of an LTE network anywhere in the MSS (Mobile Satellite Service) band, if approved by the FCC, effectively would change the rules for that band after decades of GPS gear coexisting easily with satellite systems that have used it, he said.

"The GPS industry has invested billions and billions of dollars making very good equipment that is very precise, and now you've got a new use that's incompatible, and they're blaming the victim," Kirkland said.

LightSquared caught the industry off-guard by submitting its new plan after the testing program was finished, the Coalition said.

"LightSquared was supposed to put forward ideas for mitigation that could be tested, and for the first time now, after the results are in, they're making proposals for how to mitigate," Kirkland said.

The company disputed that charge. LightSquared changed its test plan to reflect the lower band and lower transmission power halfway through the testing program, and all 130 receivers involved were tested with those parameters, LightSquared Executive Vice President Martin Harriman said. In addition, LightSquared introduced vendors of GPS filters to the technical group, but GPS receiver makers showed little interest, he said.

Stephen Lawson covers mobile, storage and networking technologies for The IDG News Service. Follow Stephen on Twitter at @sdlawsonmedia. Stephen's e-mail address is

Join the PC World newsletter!

Error: Please check your email address.

Tags 4gtelecommunicationconsumer electronicssatelliteregulationLightSquaredGPSmobilegovernmentCoalition to Save Our GPS

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Stephen Lawson

IDG News Service
Show Comments


Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >


Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >


Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

Learn more >

Lexar® Professional 1800x microSDHC™/microSDXC™ UHS-II cards 

Learn more >

HD Pan/Tilt Wi-Fi Camera with Night Vision NC450

Learn more >


Back To Business Guide

Click for more ›

Most Popular Reviews

Latest News Articles


GGG Evaluation Team

Michael Hargreaves

Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Kathy Cassidy


First impression on unpacking the Q702 test unit was the solid feel and clean, minimalist styling.

Anthony Grifoni


For work use, Microsoft Word and Excel programs pre-installed on the device are adequate for preparing short documents.

Steph Mundell


The Fujitsu LifeBook UH574 allowed for great mobility without being obnoxiously heavy or clunky. Its twelve hours of battery life did not disappoint.

Andrew Mitsi


The screen was particularly good. It is bright and visible from most angles, however heat is an issue, particularly around the Windows button on the front, and on the back where the battery housing is located.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?