GPS World, January 2012
INNOVATION System Design Test Know Your Enemy Signal Characteristics of Civil GPS Jammers Ryan H Mitch Ryan C Dougherty Mark L Psiaki Steven P Powell Brady W OHanlon Jahshan A Bhatti and Todd E Humphreys T GPS IS AT WAR It is a major asset for United States and allied military forces in a number of operating theaters around the world in both declared and undeclared conflicts But GPS is at war on the domestic front too at war against a proliferation of jamming equipment being marketed to cause deliberate interference to GPS signals to prevent GPS receivers from computing positions to be locally stored or relayed via tracking networks There have been many notable examples of deliberate jamming of GPS receivers Many more likely go undetected each day In 2009 outages of a Federal Aviation Administration reference receiver at Newark Liberty International Airport close to the New Jersey Turnpike were traced to a 33 200 milliwatt GPS jammer in a truck that passed the airport each day The driver was reportedly arrested and charged In July 2010 two truck thieves in Britain were jailed for 16 years They used GPS jammers to prevent the trucks from being tracked after the thefts And in Germany some truck drivers have been using jammers to evade the countrys GPS based road toll system The U S and some foreign governments have enacted laws to prohibit the INNOVATION INSIGHTS with Richard Langley Many instances of jamming go undetected every day importation marketing sale or operation of these so called personal privacy devices Nevertheless a certain number of jammers are in the hands of individuals around the world and they continue to be available from manufacturers and suppliers in certain countries So GPS jamming is a continuing threat both at home and abroad and a detailed understanding of how the available jammers work is necessary to judge their effectiveness and limitations This information will also help in developing countermeasures that could be incorporated into GPS receivers to limit the impact of jammers Jammers constitute an enemy force and as the Chinese General Sun Tzu stated in the Art of War more than 2000 years ago battles will be won by knowing your enemy In the last verse of Chapter Three he states So it is said that if you know your enemies and know yourself you can win a hundred battles without a single loss If you only know yourself but not your opponent you may win or may lose If you know neither yourself nor your enemy you will always endanger yourself In this months column a team of researchers from Cornell University and the University of Texas at Austin reports on their analyses of the signal properties of 18 commercially available GPS jammers The enemy has been exposed GPS World January 2012 www gpsworld com 64
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