Jamming GPS – No bad guys needed, the FCC will do it for you!

On 16-03-2011, in Satellite Navigation, by steve

Whenever a discussion is started about whether or not we should entrust aircraft navigation to GPS, there will be at least one person raising the issue of jamming. This is the specter of a single bad guy with a little black box purchased on eBay for a few bucks creating havoc in air navigation by jamming the signals of the GPS satellites. As you know, these signals coming from space are extremely weak and the system disengages and stops guidance the moment there is even the slightest doubt about their integrity. Hence the possibility of mischief with just the simplest means.

Losing GPS will not make any aircraft fall immediately from the sky but not having the precision guidance on which the new GNSS procedures rely is akin to having the ILS pulled from under you in Cat III conditions. It is survivable but traffic will be severely handicapped until the service is restored.

It looks now that we will not have to worry about the bad guys. A much bigger threat comes from the US Federal Communications Commission (FCC) and a company called LightSquared. Worse, if LightSquared has its way, scores of other companies rushing to satisfy mobile broadband services might all become potential threats to GPS. So what is the problem?

Companies like LightSquared provide mobile satellite services and there is of course big money in this. In order to increase the capacity of its service, LightSquared is planning to set up a huge number of terrestrial base stations that will operate in the part if the L-band just adjacent to the L1 frequency used by all GPS receivers. These ground stations (effectively a kind of cell-phone operation) transmit at powers that can effectively overload most GPS receivers.

How could something like this come to pass?

Originally the L-band frequencies concerned had been set aside for use by low-power space-to-Earth services and allowing high-power terrestrial signals to be transmitted on them is a completely new development. Apparently, the FCC thinks that giving LightSquared permission to use this spectrum on condition that they solve the GPS interference problem is enough to ensure safety and satisfy both sides of the user community. Apparently protests from the FAA, the Pentagon and the GPS users were not enough to make the FCC think before making its highly unusual ruling.

Of course there is an interesting kink to the story… and conspiration theorists will love this detail. When LightSquared came on the market with its wireless broadband offering, it got the nod after making a commitment to the FCC to provide the service to at least 260 million people by 2015… LightSquared now claims that it can only fulfill this commitment if it is allowed to use the spectrum adjacent to that used by GPS. LightSquared, heavily in debt to finance this project, is obviously also in a hurry, wanting to offer commercial service by the end of this year. Revenue must start rolling in as soon as possible, come hell or high water… or GPS jamming.

And it will come if tests done so far are anything to go by. Evidence indicates that in the wider vicinity of a LightSquared ground station that complies with all provisions regulating out-of-band emissions, even the best GPS receivers will lose their ability to provide a fix, being overwhelmed by the interference from the high power ground transmission.

A first class mess by any standard. Experts say that overcoming this interference is no simple matter even in new-build equipment and for retrofit, it is next to impossible even if the costs are not considered.

So, after years of worrying about the bad guys jamming GPS, here we are, nearly up against the wall caused by the very organization that is supposed to prevent this happening. Of course the professionalism of LightSquared should also be questioned. How could a company come so far up the wrong lane ignoring all warning signs?

Did they know something we do not?

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  1. Meyer says:

    And to top it off a google ad at the bottom of the article offers GPS jammers for 24 euros 😛

  2. steve says:

    Well, those ads are automatically generated and this shows just how good Google is at “reading” the articles:)))) On my PC here an Intertial Measurement Unit is being advertised… May be they know I am the author:))))

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