The next round of testing on LightSquared's proposed LTE (Long-Term Evolution) network will start next week at an Air Force base, said Jim Kirkland, vice president and general counsel of Trimble Navigation, who spoke for the Coalition to Save Our GPS on the call. Those tests are scheduled to be finished by Nov. 30, but further testing is likely to be needed, Kirkland said. The U.S. Federal Communications Commission wants the interference issue resolved before it will approve LightSquared's network.

Timing is important for LightSquared, which has promised to make its network reach 100 million U.S. residents by the end of 2012.

"The current testing is re-testing of narrowband devices with some additional ones added. We are very confident this will be done by November 30," LightSquared said Thursday in a statement attributed to Martin Harriman, vice president of ecosystem development and satellite business. Filters from Javad GNSS, a partner of LightSquared, are available for testing now and have shown good results in laboratory testing, he said.

The Coalition, which represents manufacturers and users of GPS (Global Positioning System), has been among the most vocal critics of LightSquared's plan to operate a national LTE network on 40,000 terrestrial base stations, using frequencies near to those used for GPS. Tests conducted earlier this year showed the network would knock out GPS for many devices, which scan a wide band of frequencies for weak signals from GPS satellites.

LightSquared has since said it will shift to frequencies farther from the GPS band, but critics say solving interference even there would be expensive and time-consuming. In this lower band, the danger appears to be to high-precision GPS devices such as those used for surveying, agriculture and aviation.