A US Program to Identify, Geolocate, and Mitigate Sources of GPS Interference

1
A US Program to Identify, Geolocate, and Mitigate
Sources of GPS Interference

• But are we serious?
• Terry McGurn/Consultant
• Presented to the EXEC PNT Advisory Board
• Meeting of 5-6 November 2009

2
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

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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.

4
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 Ive contacted them to
  obtain information on their program. But we
  differ greatly on the proper approach.

5
So Whats 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.

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So Whats 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.

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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
• Lets develop a capability to minimize the
  occurrence of unintentional jamming?
• You dont get partial credit if you lose a
  critical function unintentionally.

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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.
• Lets Get a Significant Start. First Address the
  Unintentional Jamming Issue.

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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)

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Interference Case Study
General AviationPilot Report GPS Malfunction
AIS Display Console Anomaly
Medical Services Paging Provider Network
Inoperative 1.5 Hours 20 sites
Potential for First Responder Impacts
DGPS Site Inoperative 2 Hours
Cell Provider Network 150 sites detected error 2
sites inoperative
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Introduction - Typical digital GNSS receiver
block diagram
RF front end
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Introduction - GNSS receiver front end with
Digital Gain Control
Antenna
Analog IF
J/N Meter
Digital Gain Control
Down Converter
Digital Attenuator
Preamp
Digital IF
ADC
Gain Controlled Analog IF
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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.

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Final Thoughts (Continued)

• When everyones in charge, no ones 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.