Thursday, February 10, 2011

A Permanent GPS Timing Outage?

Remember the late alerts from DHS ICS-CERT last month (see my posts of 01-25-11 and 01-26-11) about the tests being conducted by the Air Force that might (but it turned out not really) affect the timing signals for certain SCADA devices? Well, according to an article at there might be an even more serious problem when a new 4G Broadband Network by LightSquared goes online later this year.

According to the article, the GPS industry claims that the L Band frequencies approved by the FCC for the LightSquared project (1525 MHz—1559 MHz) are very close to the frequencies being used by the GPS system (1559—1610 MHz). Apparently at least one GPS device (a Garmin 430) looses its GPS fix within about 5 miles of a 4G transmitter on the nearby approved frequencies.

LightSquared reportedly disputes the potential of problems with ‘properly filtered’ GPS devices, but is required by the FCC to test devices against their actual transmission system. That testing is supposed to be done by the end of June. Nothing in the article indicates that there are any plans for testing ICS devices that use GPS signals for timing purposes.

Hmmm. It would sure be nice to hear that ICS-CERT was getting involved in this testing issue before the end of June. Or, are we going to have to wait to see an ICS-CERT alert that there are reported problems with ICS outages because of unidentified transmitters near facilities?

Once again this is a demonstration of the potential problems that arise when someone develops an unauthorized (not illegal, just not specifically authorized) usage of a ‘free’ resource like the GPS timing signal. Since no one (read FCC) officially knows of the usage, they are under no requirement to take that usage into account when making official decisions affecting that resource.

As the RF spectrum is getting more and more crowded because of the new communications devices being used, how many more frequency interference issues will be affecting ICS devices? Have all of these devices been ‘properly filtered’ to avoid interference from transmitters on nearby frequencies? Has anyone bothered to do the necessary testing to determine how much of a problem this could be?

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