A US Program to Identify, Geolocate, and Mitigate Sources of GPS Interference
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Transcript of A US Program to Identify, Geolocate, and Mitigate Sources of GPS Interference
A US Program to Identify, Geolocate, and Mitigate
Sources of GPS Interference
But are we serious?
Terry McGurn/ConsultantPresented to the EXEC PNT Advisory BoardMeeting of 5-6 November 2009
Background & Motivation
• Motivation: NSPD-39, Dec 2004– Maintain Continuity of GPS service in an
interference environment– Deny hostile exploitation of this service.
• NSPD-39 Actions (From Fact Sheet)– Establish a PNT EXCOM to address these issues,
among others– Establish the EXCOM Advisory Board– Establish Agency Roles
CONCLUSIONS
• Language of the NSPD-39 Fact Sheet is vague.
• Open to Various Interpretations of Assignments.
• NSPD-39 Muddies the Issues (friendly protection & hostile denial).
• I Believe The Program is Headed in the Wrong Direction.
• But I believe we can get back on track.
DHS: The Action Agency• DHS has taken action on this program.
– DHS developed an IDM paper to address
this issue, published in 2007. Largely reflects NSPD-39
– The DHS, as well as its contractors, have been very forthcoming when I’ve contacted them to obtain information on their program. But we differ greatly on the proper approach.
So What’s Wrong?
• No one is tasked to develop and array sensors to detect/geolocate interferers.
• The fact sheet, as well as responses to it, reflect a belief that we have these assets already in place, and the task is primarily to coordinate these assets.
• There are assets available that could be netted to support the program, but these are only mentioned in passing.
So What’s Wrong? (Cont,d)• The responsible DHS body for this program
appears to be the Office of Infrastructure Protection within the Directorate for National Protection & Programs, and several of its high level appointees are not yet in place.
• I believe the present DHS approach puts the cart before the horse. (i.e., developing the “data repository” before developing the sensors that will provide the “reposing” data.)
• In fact, the sensors should dictate the degree of processing to be done at the repository vice in the field.
So: What Can We Do Now?• DHS should address the pieces of the issue.
The “one size fits all” approach not practical• Intentional jamming, spoofing, unintentional
interference are different problems. • But, at present, unintentional jamming
appears to be the most frequent source of signal loss.
So• Let’s develop a capability to minimize the
occurrence of unintentional jamming? • You don’t get partial credit if you lose a
critical function unintentionally.
Recommendations• Define Specific Responsibilities for the
Various Components of the Network. (An EXCOM role?)
• Suggest Several Small Funded Efforts. (Requires more selective expertise/less PPT.)
• Responsible Dept/Agency should have System Engineering Support.
• Let’s Get a Significant Start. First Address
the Unintentional Jamming Issue.
Examples of Unintentional Jamming
• Rome, NY, ADC (3 days/5 watts/ several hundred kilometers) (1997-1998)
• St. Louis Airport (1990s)• Butte, Montana (? days, spurious
harmonics)• Monterey Bay (many months/ VHF/UHF
TV antenna radiating above the L-band noise floor) (~2001)
• San Diego Navy Test Center (4 hrs, 500 mw) (2004)
DGPS SiteInoperative
2 Hours
AIS Display ConsoleAnomaly
Cell Provider Network150 sites detected error
2 sites inoperative
Medical Services Paging Provider Network
Inoperative
1.5 Hours – 20 sites
General AviationPilot Report GPS
Malfunction
Potential for First Responder Impacts
Interference Case Study
Introduction - Typical digital GNSS receiver block diagram
RF
Antenna
LOs
Digital IF
Analog IF
N2
Regulated DC power
Unregulated input power
Navigation processing
User interface
Power supply
Receiver processing
AGC
Frequency synthesizer
Reference oscillator
1 Digital receiver
channel
A/D converter
Down converter
Pre amp
RF front end
Introduction - GNSS receiver front end with Digital Gain Control
ADC
Digital Gain
Control
Analog IF
J/N Meter
Digital IF
DownConverter
Antenna
PreampDigital
Attenuator
Gain Controlled Analog IF
Final Thoughts
• Mitigation:– Where possible, geolocate and prosecute– Otherwise:
• Back-up Systems– Inertial (short term only. Present inertial trends
are for poorer performance, low-cost systems.– eLoran: Provides high availability, good anti-
jam, and good timing performance (sigma about 30 nsec).
– Smart receivers, for situational awareness.
Final Thoughts (Continued)
• “When everyone’s in charge, no one’s in charge”.
(A retired Russian Colonel, in discussing the problems in the GLONASS program)
• This is a hard problem. But a challenging one. Tackle it bit by bit.