LTE wireless could pose a threat to GPS devices

Could you live without your satellite navigation system? If we're to believe a new pressure group called Coalition to Save our GPS, it won't be long until we find out.

The group consisting of GPS manufacturers, airline trade organisations and other concerned parties, claims that a 4G LTE service is on the brink of breaking Global Positioning Systems for the population at large, including emergency responders such as ambulances and police.

LightSquared

The problem relates to the frequencies a startup called LightSquared intends to use for its 4G LTE phone service.

Earlier this year the US Federal Communications Commission approved LightSquared's plans to operate in the frequency range of 1525 to 1559MHz. GPS operates in the neighboring 1559-1610MHz band and, depending on who you speak to, it's all a little too close for comfort, not least because cell phone signals from towers are an order of magnitude stronger than GPS signals.

A few weeks ago GPS device manufacturer Garmin set up an experimental transmitter broadcasting on LightSquared's proposed frequencies. It caused havoc for several Garmin products. An aviation device lost its GPS fix at just under 14 miles away from the transmitter, and was totally jammed five and a half miles away. One of Garmin's most popular consumer devices lost its fix just over half a mile away.

Scary. The coalition points out that LightSquared plans to built up to 40,000 ground stations, potentially creating an equivalent number of GPS dead spots miles in diameter.

In response, LightSquared points out that the Garmin tests were "not made under appropriate circumstances" and that "tests must be conducted in the proper band and with the right filters." They add that they're running their own tests, supported by the government.

Indeed, the company was only able to receive its FCC approval by promising to address GPS interference issues, after concerns were raised by the National Telecommunications and Information Administration (NTIA).

Coalition of the unwilling

Included within the Coalition to Save our GPS are manufacturers Garmin, Trimble and OmniSTAR, as well as trade organisations like the Air Transport Association (ATA) and General Aviation Manufacturers Association (GAMA). The American Association of State Highway and Transportation Officials is also a member, as are a host of bodies representing sectors of the manufacturing industry.

The coalition refers to the FCC's approval for LightSquared's plans as "highly unusual." It claims the FCC usually conducts extensive tests before granting approval, but in this case turned that on its head, the FCC granted approval but insisted on follow-up tests.

Perhaps in an indication of its underlying intention, the coalition goes on to say that interference issues should be taken care of by LightSquared, which "must bear the costs of preventing interference of any kind resulting from operations on LightSquared's frequencies."

That could well be the meat of the argument: It might be that GPS and LightSquared's proposed service are able to co-exist only after modifications to GPS hardware, perhaps adding filtering circuits or shielding. And who will pick up the bill? Is it right, for example, if consumers have to pay for more expensive hardware just so another 4G LTE service joins the airwaves?

Regardless of who would pay for any necessary tweaks to new products, however, it wouldn't do anything to protect existing GPS hardware against interference issues. There would need to be a significant upgrade of global airline systems, for example. Firmware updates might be able to address the issue but again, the question of who will pay for the work is unanswered.

At the consumer level, GPS device users are perhaps less likely to upgrade firmware than users of other mobile equipment like cell phones, and older devices might not even offer a method of updating the software.