Combating the Single Point of Failure

On 25-26 January 2016, many first responder radio systems across North America reported faults. The U.S. government received similar reports from cellular networks and digital broadcast companies around the world. A Federal Aviation Administration (FAA) flight safety system called ADS-B was also out of service for several hours. Some systems failed, some services were degraded, others just alarmed. All required human intervention and caused concern for the better part of a day.

The culprit of the January 2016 faults was a 13.7 microsecond error in the signals transmitted by about half of the global positioning system (GPS) satellites. The glitch unexpectedly appeared when the Air Force removed its oldest GPS satellite from service. The ensuing problems took around 11 hours to correct.

GPS Interdependencies

Although that particular problem may not occur again, a wide variety of other things can go wrong with GPS signals and the way they are used. In August 2017, Pennsylvania’s York and Dauphin Counties’ 911 paging systems were knocked out because of a problem with the GPS receivers embedded in their systems. According to one dispatcher, “Suddenly it was December 14, 1997.” Accounts of the core problem differed between the receiver manufacturer and system operator, but it was another stark example of the importance of GPS in first responder networks.

GPS signals have become essential to an incredible variety of services that everyone relies on: navigation, routing, common operational pictures, blue force, and asset tracking to name a few. But more subtly, GPS timing signals enable digital land mobile radios for multiple conversations on a single frequency. They synchronize wireless networks, allowing messages to be decoded and cell towers to talk to each other. GPS-based time stamps allow databases to know which is the most recent bit of information being stored. They also provide location data as a part of identity management and offender monitoring systems. The list is almost endless.

Deliberate & Accidental Interferences

Yet, essential GPS signals are very, very faint. As a result they are very easy to disrupt, either intentionally or accidentally. For $50, a concerned citizen can buy a personal GPS jammer to avoid being tracked by their employer or ex-spouse. The distortion field extends from 10 to 500 feet. They could impact a nearby cell tower where they are waiting for a red light, or a landing system at a nearby airport (as has happened twice at Newark International).

For $250, criminals can purchase a device that jams GPS, LoJack, and cellphones. These are particularly useful for stealing high-value cargo and expensive automobiles that may have embedded tracking devices. Thieves simply turn on the jammer, swipe the cargo, and, when they are in a safe location, find and disable the trackers before turning off the jammer.

In Europe, limited sampling has discovered over 50,000 deliberate jamming incidents in the past few years and more than 300 different kinds of jammers. The problem is at least as big in the United States.

Accidental interference is also a major concern. Signals can bounce off buildings and confuse receivers. Nearby electrical equipment can also be a problem. As an example, security contractors at the 2014 Superbowl reported privately that they found an elevator generated enough radio noise when it went up and down to interfere with GPS reception nearby.

Solutions at the Federal Level

All of these threats, combined with users’ deep dependence on the signals are why officials at the Department of Homeland Security have called GPS “a single point of failure for critical infrastructure.” Something that should make officials at every level of government lose sleep at night.

So, the question now is how first responders and other domestic preparedness professionals should address this significant threat and vulnerability. The Resilient Navigation and Timing Foundation supports policies and systems that protect GPS signals from disruption, toughen users and user equipment, and augment GPS signals with other sources (particularly the high-power, wireless, terrestrial system the U.S. government has promised to establish).

Normally, these recommendations focus on federal policy makers because GPS vulnerabilities can be most effectively addressed at the national level. However, “Protect, Toughen, and Augment” is good advice for everyone, especially domestic preparedness professionals:

  • Protect – GPS signals should be protected in the area of operation. These signals are essential to nearly every activity and, if there is interference, professionals would want to know about it and make it stop. Equipment to detect and locate interference is readily available, though it does vary in complexity and ease of use. Without making any recommendations, an internet search for “GPS interference detection” would produce many good hits.
  • Toughen – Toughening equipment is equally important. GPS receivers throughout an enterprise should be able to detect and resist many types of jamming (denial of service) and spoofing (false, misleading signals). Spoiler alert – these will cost more than a receiver at a discount store, but they are worth the cost in the end. Unfortunately, there are no industry standards for these kind of added security features, so it is helpful to work with a trusted professional in this field.
  • Augment – Both the Bush and Obama administrations promised to augment GPS with high-power eLoran signals so that the combined system would be virtually bullet proof (and it would also work indoors, underground, and under water). The Trump administration is “studying the issue” again.

Solutions at the State & Local Levels

State and local authorities are probably not going to want to set up their own eLoran networks (though they might consider talking to their elected federal representatives about GPS as a “single point of failure” and broken promises about augmenting it). However, jurisdictions can plan and prepare for what they would do during a GPS outage, whether local or widespread. Questions to answer include:

  • Do all vehicles and personnel have current paper maps?
  • How will blue forces communicate when land mobile radios and cellphones are not available or working poorly?
  • Do contingency plans and exercises even consider “no-GPS” scenarios?

GPS signals are a critical underpinning of everyday life. Responsible first responders need to ensure GPS use is as good as it can be when it is available, and they are prepared to continue operating when it is not.

Dana A. Goward

Dana A. Goward is the president of the Resilient Navigation and Timing Foundation, a scientific and educational charity in northern Virginia. He spent several decades as a first responder piloting Coast Guard helicopters, and was serving as the maritime navigation authority for the United States when he retired from federal service.



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