GPS may not work if interference problem isn't fixed

SAN JOSE, Calif.

Satellite based navigation, or GPS, has become a big tool for drivers and for pilots, who can chart their location on iPads. However, an interference problem has surfaced as a new generation of high-powered wireless network is being built.

"At around 10 miles or so, they see jamming of the satellite signals and at about three or four miles, a complete loss of fix, so you don't know where you are anymore," said Peninsula Avionics president Art Vartanian.

A letter documenting these problems has been submitted to government regulators. Private pilot Kevin Morris says a jammed or lost signal could have serious consequences.

"That can be a matter of seconds before you're into a dangerous situation where you may end up hitting terrain or some type of obstruction," said Morris.

Engineers say the interference may be due to the GPS and the cell networks operating on adjacent frequencies.

San Jose-based Symmetricom is part of a working industry group studying the problem and working on a solution. It can't be solved simply by moving the new cell networks to a different frequency.

"The radio spectrum, the frequencies in which these services operate, is actually the most expensive, the most limited commodity, and it's not easy to find another location for these new services to operate in," said Symmetricom vice president Manish Gupta.

Gupta says interference could also lead to dropped cellphone calls. That's because GPS is used to switch a conversation from one tower to the next.

Solutions will surface because better cell networks and reliable GPS devices are both needed.

The working committee's report will be submitted to the Federal Communications Commission on Wednesday. Pilots and others who rely on GPS devices will be watching closely.

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