US wireless network could drown out GPS, experts warn

LightSquared's system would give US a nationwide wireless broadband network but clash with GPS could cost billions to fix
Cessna Citation
Cessna Citation
Clouds on the horizon ... experts warn a new wireless network could drown out GPS signals for US aircraft. Photograph: George Hall/Corbis

A new ultra-fast wireless internet network being built in the US could drown out GPS signals and interfere with everything from aircraft to police and civilian navigation devices, experts are warning.

The network, under construction by a company from Virginia called LightSquared, would provide a nationwide wireless broadband network – but using frequencies close to those on which the time signals from the Global Positioning System (GPS) satellites are transmitted. GPS equipment manufacturers say that any strong signals from the LightSquared system could drown out the incredibly faint signals from the orbiting satellites.

A technical fix could cost billions of dollars, according to one estimate, and it is unclear who would have to pay. US government officials say they will block LightSquared from activating the network unless they get assurances that GPS will still work.

In response LightSquared has set up a working group to report every month to the US Federal Communications Commission (FCC) which is trying to establish the risk. The group includes representatives from LightSquared, the GPS receiver industry and a number of US government bodies which rely on GPS.

The FCC granted the licence to LightSquared on the explicit requirement that it should not cause any GPS jamming. The aim of the network is to boost wireless competition and bring faster, cheaper internet links to rural and other parts of the US. LightSquared and the FCC both insist the new network can coexist with GPS systems.

But device makers fear GPS signals will be wiped out. The power of a GPS timer signal received at the ground is actually less than the background "noise" from electronic systems; only careful amplification makes it detectable. A GPS navigation device has to detect multiple signals, amplify them and distinguish the differences in their timing to determine its own location on the ground. Adding extra noise in a frequency close to the GPS one could increase the challenge.

LightSquared intends to build a network using as many as 40,000 transmitters. "The potential impact of GPS interference is so vast, it's hard to get your head around," said Jim Kirkland, the vice-president and general counsel of Trimble Navigation, which makes GPS systems. "Think 40,000 GPS dead spots covering millions of square miles in cities and towns throughout the US."

One of the biggest risks is to the GPS navigation systems used by about 40% of commercial and private planes. Backup systems that rely on ground-based radio signals are not as accurate and have coverage gaps. Some older private planes have no backup at all. GPS interference could mean a pilot "may go off course and not even realise it", said Chris Dancy, a spokesman for the Aircraft Owners and Pilots Association.

LightSquared's network could also undermine the Federal Aviation Administration's (FAA) multibillion-dollar program to upgrade the US's air-traffic control system, which is based on secondworld war-era radar technology.

The new GPS-based system is more precise and lets planes fly more direct routes. That will save airlines time, money and fuel and cut pollution. It is also key to accommodating projected increases in airline traffic by enabling planes to fly safely closer together.

Public-safety officials, too, are nervous about LightSquared because they rely on GPS to track and dispatch police cars, fire trucks and ambulances. Many 911 systems also use GPS to help locate people. Disruptions could delay responses to emergencies, said Harlin McEwen, an official with the International Association of Chiefs of Police. Even the Pentagon has expressed concern as it relies on GPS to guide planes, ships, armoured vehicles, weapons and troops.

"We have every reason to resolve these concerns because we want to make sure there is a robust GPS system," LightSquared executive vice-president Jeffrey Carlisle said.

Dan Hays, a consultant with the firm PRTM, insists the technical solution is straightforward: GPS devices need to include better filters to screen out the LightSquared signals. But estimates on the costs of a fix vary hugely. Hays believes it will cost no more than $12m, or $0.30 per device, to install better filters in roughly 40m standalone GPS units made worldwide each year. Mobile phones, he said, won't need it because they don't rely solely on GPS to determine location and have better filters. But Tim Farrar, a consultant with TMF Associates, insists cellphones need upgrades too, raising the annual cost to as much as $1bn.

LightSquared plans to compete nationally with super-fast, fourth-generation wireless services being rolled out by the likes of AT&T and Verizon Wireless. It won't sell directly to consumers, though. Instead, LightSquared will provide network access to companies including Leap Wireless, parent of the Cricket phone service, and Best Buy, which will rebrand the service under its own name.

The bigger challenge though may be in financing the scheme. The estimated cost of building the entire network is put at $7bn, but so far the company has raised only about $2bn, including $586m of debt in February.

LightSquared has its roots as a satellite-phone operator, but in January the FCC gave it permission to build a broader, conventional wireless data network. Although the company will continue to offer satellite service, it plans to cover at least 92% of Americans by 2015 with high-power wireless signals transmitted by base stations on earth.

Hays said the real problem is that GPS receivers are "eavesdropping on signals outside of where they are supposed to be" in LightSquared's space. That was not a problem until now. LightSquared and the FCC say the GPS industry should have been preparing for a ground-based network nearby since the FCC first allowed backup wireless systems in that space in 2003.

All of which leads Hays to portray the problem this way: "This is a situation where the neighbour [GPS] built the fence too far over the property line and may not have realised it at the time. Now the other neighbour wants to build a pool and there is not enough space. So the question is: who has to pay to move the fence?"

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