Evolution of GPS Systems Architecture and Its Impacts

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INTRODUCTION

There is no denying the impact that GPS has had on our daily lives both in the United States and worldwide. Far beyond the small screen on the dashboards of automobiles that many drivers have come to rely on in place of the paper road maps we grew up with, GPS is now a ubiquitous technology that is utilized for applications in transportation, financial systems, cell phone technology, air traffic communications, emergency services and many others. Over time, GPS has become something almost like a utility. Civil agencies, commercial firms and many individuals use some type of GPS receiver to navigate from one location to another. Firms in the private sector use the technology to route vehicles, not only in the maritime sector but in mass transit as well. The aviation industry has implemented its use to augment navigation and increase the safety and efficiency of commercial flight systems. The timing signal that GPS broadcasts has become critical various economic activities that include and as diverse as electrical power grids, financial networks and communication systems.

Figure 1 shows military and nonmilitary users of GPS technology reported by Bogosian (2003). Not too bad for a piece of technology that was originally intended for use only as a weapon system, but quite often much of the technology used by the U. S. milita ry today either starts out or ends up as what is called "dual use." This is not a new idea but in fact represents what has become a long term trend. Unfortunately, the very fact of GPS' utility in so many daily applications is the very reason that the United States Air Force (USAF), the Executive Agent for the management of the GPS constellation, is presently considering other technologies for its eventual replacement. The fact that it has become so widespread and the signal so open source also has increased its vulnerabilities to the point that many senior leaders in the USAF consider it to be too unreliable for long term use as a piece of a weapons delivery solutions. The situation has become serious enough that the USAF Chief of Staff Gen. Norton Schwartz has addressed the issue directly in his opening remarks at a national security conference in Washington D.C. on January 20, 2010 (Hoffman, 2010), where he stated:

[FIGURE 1 OMITTED]

  "Global positioning has transformed an entire universe of war-fighting
  capability. Our dependence on precision navigation in time will
  continue to grow," (Schwartz said in the opening address to the
  conference, sponsored by the Institute of Foreign Policy and Tufts
  University's Fletcher School). "It seems critical to me that the joint
  force reduce its dependence on GPS aid." (1)

General Schwartz went on to speak to the possibilities of an enemy jamming a GPS signal needed by the military or, alternatively and even worse, to make use of some type of spoofing technique to reroute a weapon to a location other than its intended target. This spawns the following questions: How likely are these scenarios? How big a threat is it to U. S. national security?

Manufacturing      7%
Tracking          10%
Vessel voyage      2%
Military affairs   1%
GIS                8%
Car navigation    35%
Survey             7%
Hand held         26%
Aviation           8%

Figure 2: Distribution of GPS Users in the United States
("GPS", 2006, July)

Note: Table made from bar graph.

The Air Force Institute of Technology (AFIT) is a leading source of research and development for the USAF. Located at Wright Patterson AFB, near Dayton, Ohio, it sponsors and educates the next generation of USAF technical leaders in areas of science and technology critical to the future of the force's ability to achieve and sustain air dominance. In a review of the list of Thesis titles (2) for work done in the last five years, the examples of an alternative to GPS are many, including in 2010 alone:

* Gravity Gradiometry and Map Matching: An Aid to Aircraft Inertial Navigation Systems.

* An Integrity Framework for Image-Based Navigation Systems.

* Satellite-Based Fusion of Imaging Sensors and Georegistered Map Data for Precise Geolocation and Target Tracking.

* Global Navigation Satellite System Software Defined Radio.

* Aiding GPS with Additional Satellite Navigation Services

* Broadcast Vs Precise GPS Ephemerides: An Historical Perspective

* Precision Navigation Using Pre-Georegistered Map Data

* Aiding GPS With Additional Satellite Navigation Services

There are multiple others which demonstrates the fact that the Air Force considers it a big enough issue to begin pouring money into researching potential solutions at this time. Defining the system of technologies as yet immature or even nonexistent that will augment or even completely replace the current system is not a trivial task. Is the Air Force overblowing the issue?

VULNERABILITIES--NATURAL AND OTHER

While there are natural sources such as solar flares that can interfere with a GPS signal, we need to understand that we are not talking about disrupting a very strong signal. "The strength of a GPS signal is about as strong as viewing a 25W light bulb from a satellite 10,000 miles away," said Bob Cockshott, a director of the Digital Systems KTN.

"It's no surprise then that GPS signals are vulnerable to natural and, increasingly, criminal interruptions." (3)

There are in fact GPS jammers available for sale now on the internet (4). A recent article by Fox News even provides links to sources where the devices can be purchased at http://www.jammer-store.com/gj6-all-civil-gps-signal-jammer-blocker.html and http://gadget.brando.com/car-cigarette-anti-gps-system_p00963c024d001.html for as little as $49 that can be shipped worldwide via UPS. On review of the sites, the capabilities of the devices seems limited to a 10-15 meter range. This by itself should not be too alarming to the AF which can provide a "kinetic solution" dropped from a fighter that will leave a crater twice this size, but there have been tests conducted in the United Kingdom that have demonstrated the ability to jam a signal for a radius as large as 30 kilometers and in fact has been shown to provide a way of "spoofing" the signal to provide erroneous position and velocity information. This research shows that this technology jams the L1/L2 and L5 bands currently broadcast or currently projected for adoption. (5)

The 30 km radius documented in the research combined with the multiband frequencies provide the answer to the question posed earlier about the problem being potentially overblown--we have to conclude that the issues posed by the Air Force do, in fact, present a very real loss of combat capability currently enjoyed and required by the U. S. military.

The GJ6, shown in Figure 3, is advertised to jam all civil GPS frequencies including GPS L1, GPS L2 and GPS L5 systems. After turning on the GJ6 jammer, all civil GPS signals will be blocked. The GJ6 has a cooler fan inside the housing. Not all GPS tracking devices are able to work in your car. A more mobile …