CG to Study Alternatives to GPS Timing

Today the Coast Guard published a notice in the Federal Register (77 FR 1708-1710) of their intent to enter into a “Cooperative Research and Development Agreement (CRADA) with UrsaNav, Inc., to research, evaluate, and document at least one alternative to  Global Positioning Systems (GPS) as a means of providing precise time” (77 FR 1708).

One would assume that this is in response to the studies that indicate that the LightSquared broadband system deployment may cause significant interference with GPS signals; signals that are used in some control system applications to link physically separated timing events. I’m not sure what the Coast Guard’s interest is in these timing services and it is surely not discussed in this notice.

This CRADA envisions the testing of timing signal transmissions on four separate frequency ranges:

• LORAN frequencies (90-110 kHz);

• dGPS frequencies (283.5-325 kHz);

• HA-dGPS frequencies (435-490 kHz); and

• Former international calling and distress frequency (500 kHz).

On-air testing will be conducted with transmissions from former Long Range Navigation (LORAN) sites and “other sites as deemed necessary” (77 FR 1709). Reception will be evaluated at both off-shore and on-shore sites.

Public comment on this CRADA notice is being solicited. Comments may be submitted via the Federal eRulemaking Portal (www.Regulations.gov; Docket # USCG-2011-1167). Comments should be submitted by February 10^th, 2012. Notice of interest in participating in a separate CRADA addressing the same issue may be submitted to the same place with the same time limit; detailed CRADA proposals would be submitted separately to LT Helen Y. Millward (Helen.Y.Millward@uscg.mil), U.S. Coast Guard Research and Development Center.

GPS Interference from New Cell Service

Readers may remember that back in January there was a ‘mysterious’ report of expected GPS outages by the FAA that were re-broadcast by ICS-CERT because of their potential for interfering with certain timing signals used by some SCADA systems. I never did see a good explanation for the cause of the problem until early this morning when I was looking over the late news from yesterday.

An interesting article over on NextGov.com was discussing a test conducted by LightSquared, a new cell service provider, to see if their cell phone broadcasts interfered with GPS reception on nearby frequencies in areas near the cell towers. Low and behold, in a limited area right near the tower they completely scrambled some GPS receivers and just threw off the accuracy of other receivers. There is still some debate apparently whether the broadcast signal broadcast outside of the allowed spectrum, which borders the frequency allotted for GPS receivers; or if the receivers were too sensitive to signals outside of the allotted GPS spectrum.

I see no mention in this report of whether or not any SCADA devices were tested to see if LightSquared’s signal interfered with the GPS timing signal used by those devices to coordinate timing of actions at multiple, remote locations. From the scope of the tests reported in this article it would seem that the SCADA device would have to be close to the cell phone tower, but I know of two pipe line pumping stations near where I live that appear to have cell towers within the station perimeter.

I am absolutely sure (SARCASM Warning) that the ICS-CERT, PHMSA and TSA Pipeline Security have all been intimately involved in these studies, as have the appropriate vendors and anyone else with an interest at SCADA operations at remote locations. Everyone is too smart and communicates too well for something like this to have fallen through the cracks.

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 AVWeb.com 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?