Journal of Global Positioning Systems (2004)
Vol. 3, No. 1-2: 40-44
JAMFEST - A Cost Effective Solution to GPS Vulnerability Testing
Lt Col Eric Lagier
46th Test Group, 871 DeZonia Ave, Holloman AFB, NM 88330
email: Eric.Lagier@46tg.af.mil; Tel: (505) 572-1367; Fax: (505) 572-1575
Capt Desiree Craig
46th Test Group, 871 DeZonia Ave, Holloman AFB, NM 88330
email: Desiree.Craig@46tg.af.mil; Tel: (505) 572-1243; Fax: (505) 572-1575
Paul Benshoof
746th Test Squadron, 1644 Vandergrift Rd, Holloman AFB, NM 88330
email: Paul.Benshoof@46tg.af.mil; Tel: (505) 679-1769; Fax: (505) 679-1759
Received: 15 Nov 2004 / Accepted: 3 Feb 2005
Abstract. From May 24-28, 2004, the 746th Test
Squadron, located at Holloman Air Force Base (AFB),
New Mexico (NM), planned and executed an innovative
Global Positioning System (GPS) jamming program at
White Sands Missile Range, NM. This program, known
as JAMFEST, was aimed at providing low to no cost,
realistic, GPS jamming scenarios for testing GPS-based
navigation systems, as well as, training personnel in
unique GPS denied environments. Through sponsorship
from the GPS Joint Program Office, White Sands Missile
Range, and the 46th Test Group, the 746th Test Squadron
was able to provide this opportunity at a significantly
reduced cost to each participant. During JAMFEST, the
746th Test Squadron hosted twelve simultaneous, yet
very diverse customers, including multi-service
Department of Defense (DoD) organizations, several
defense contractors, and civil organizations. Their
objectives ranged from training personnel on the effects
of GPS jamming to characterizing the performance of
prototype advanced anti-jam technologies against
operationally realistic threats. To accomplish these goals,
participants drove, flew, or walked through 59 jamming
scenarios specifically tailored to stress the systems under
evaluation. These tests would have cost a total of
$660,000 or more if conducted separately. However,
JAMFEST achieved the same objectives for
approximately $85,000 in available funds coupled with
discounted or donated services totaling $175,000. This
paper details overall test and participant objectives,
strategies, conduct, and addresses future JAMFEST
activities.
Key words: JAMFEST, vulnerability, test, GPS
1 INTRODUCTION
The 746th Test Squadron (746 TS) has conducted
complex GPS jamming experiments since the early 1990s
and played a key role “behind the scenes” creating
multiple high-profile jamming environments for
programs such as the Joint GPS Combat Effectiveness
(JGPSCE) exercises and Quick Reaction Tests. These
programs, conducted to support real-world operations,
enhanced the 746th TS’s ability to recreate realistic
jamming environments and resulted in the 746 TS
earning the reputation as the recognized experts for open-
air GPS vulnerability testing.
The 746 TS conducted JAMFEST as an opportunity to
broaden both the operational and test communities’
awareness of GPS vulnerabilities by offering a cost-
effective, operationally realistic venue to facilitate testing
and training objectives. This opportunity was truly
important to the operational and test communities
because GPS signals use very low power and are
vulnerable to both intentional and unintentional
interference. These effects can adversely impact the
position and timing accuracy of various receivers and
navigation devices employed by military and civilian
users.
Because of this adverse impact, it was critical to the
Lagier et al: A Cost Effective Solution to GPS Vulnerability Testing 41
success of the program that the jamming environment be
both operationally realistic and beneficial to the military
and civilian users. Specifically, it involved coordinating
frequency clearances, securing range space, developing
jamming scenarios, deploying personnel and equipment,
operating the threat assets, data reduction and analysis,
reporting, and securing funding for the program. By
capitalizing upon their unparalleled experience base, the
746 TS easily met and overcame these tasks.
The 746 TS designed innovative vulnerability scenarios
that streamlined test conduct into a one-week event that
maximized set-up efficiency and significantly reduced
costs to the participants. In doing so, the May 04
JAMFEST capitalized on the ability to share common
jamming scenarios, which enabled users to participate in
unique environments at a fraction of the normal cost and
allowed organizations that normally would not consider
participating in such an event the opportunity to take part.
In fact, by streamlining the program in this highly
efficient manner, the team reduced a $660,000 program
into a $175,000 program. After excluding donated
services and benefits from the White Sands Missile
Range, and the GPS Joint Program Office, the total
program cost was $85,000.
This was the first in a series of recurring events; the next
event is scheduled in Nov 04.
2 OBJECTIVES & RESOURCES
The overall objective of JAMFEST was to provide and
characterize the GPS jamming environment in multiple
configurations to enable the participants to test, train, or
gain experience in a GPS jammed scenario. Each
participant used JAMFEST to execute their own
objectives, which included the following:
Evaluate the effects of jamming on a representative set of
GPS receivers to determine the effective range from the
jammers and the power level that disrupts GPS tracking;
Evaluate potential benefits of anti-jam technology
available to civil operators;
(1.) Collect performance data against specific
targets/environments that will confirm proper
operation of the overall locator system and sub-
system;
(2.) Subject anti-jam systems under test to high GPS
jamming/Signal (J/S) environments and compare
results;
(3.) Collect jamming environment truth data to
improve and verify laboratory modeling and
simulation tools, vulnerability prediction
analysis, and mission planning software;
(4.) Validate tactics, techniques and procedures
(TTPs) using hand held receivers (HHRs).
To effectively execute these objectives, the 746 TS
employed multiple test assets to configure an
operationally representative GPS jamming environment.
The ground jamming configuration was set up on White
Sands Missile Range (WSMR).
One of the primary test resources used to create the
jamming environment was the Portable Field Jamming
System (PFJS). The PFJS (see Figure 1) is a modified
Ford 350 van with a full suite of GPS Electronic Warfare
(EW) equipment, which included TMC Advanced Threat
Emulators (TATEs) and TAVIA-32 Emulators (TAVIAs)
as well as a variety of high power adjustable amplifiers.
The onboard EW equipment was programmed to provide
a wide range of jamming scenarios and signal
modulations. The system records time-tagged amplifier
power output for test analysis and time correlation to the
test item.
Another key resource employed was the Tactical Field
Jamming System (TFJS). The TFJS (see Figure 2) is
designed to supply the same capabilities as the PFJS, but
in a vehicle capable of accessing terrain that is more
rugged. Each TFJS is a modified High Mobility Multi-
Purpose Wheeled Vehicle (HMMWV) that comes
equipped with a full suite of GPS EW equipment, which
includes TATEs and TAVIAs, as well as a variety of high
power adjustable amplifiers. Due to the TFJS’s ability to
be positioned in areas inaccessible to most vehicles, these
jammers were set up in remote territory and controlled
via radio modem.
Figure 1 Portable Field Jamming System
(PFJS)
42 Journal of Global Positioning Systems
Portable Box Jammers (PBJ) (see Figure 3) in
conjunction with the PFJSs and TFJSs, were set up along
designated range roads and remote locations to help
create the jamming environment. Each PBJ is a stand-
alone jamming system designed to supply the same
capabilities as the PFJS and TFJS, but in a smaller, more
versatile package. Each system was equipped with
portable generators, a portable antenna mast and tower,
and a full suite of GPS EW equipment that included
TATEs and TAVIAs, as well as a variety of high power
adjustable amplifiers.
Figure 3 Portable Box Jammer
The 586th Flight Test Squadron (586 FLTS), a sister
squadron to the 746th TS, characterized the jamming
field using the C-12J (see Figure 4). The C-12J is a
Beechcraft 1900 twin turbo-prop aircraft that has been
modified to for GPS/inertial guidance and navigation
components and systems tests. Its capacities include a
16,600-pound maximum gross weight and a maximum of
four test stations or equipment pallets. The aircraft was
configured with controlled reception pattern antenna
(CRPA) ports and fixed reception pattern antenna
(FRPA) ports on the top and bottom of the fuselage.
During JAMFEST, the C-12J carried 746 TS equipment
designed to collect airborne reference measurements of
the GPS jamming environment. It flew data collection
sorties that spanned the airspace and altitudes used by the
systems under test.
Figure 4 C-12 J Aircraft
In any test environment where navigation aids are
evaluated, it is paramount that the truth reference data is
preserved and collected. This is particularly difficult to
achieve in a live GPS jamming environment, because
many reference systems use GPS to obtain an accurate
truth source. To overcome this obstacle, the 746 TS
developed the CIGTF Reference System (CRS); this was
the reference system used for JAMFEST. The CRS is a
rack-mounted (see Figure 5), loosely/tightly-integrated
system, consisting of navigation sensors/subsystems,
Data Acquisition System (DAS), and post-mission
processing mechanization (see Figure 6). Figure 5 CIGTF
Reference System
Figure 5 CIGTF Reference System
The DAS, a DOS-based computer, performs the primary
functions of data collection and real-time control for the
following subsystems: (1) Embedded Global Positioning
System (GPS)/Inertial Navigation System (INS) (EGI)
navigation system, (2) GPS receiver/receivers, (3)
Standard Navigation Unit (SNU) INS, and (4) Cubic CR-
100 Range/Range Rate Interrogator/Transponders System
(RRS). Other subsystems supported in the CRS
Figure 2 Tactical Field Jamming System
Lagier et al: A Cost Effective Solution to GPS Vulnerability Testing 43
architecture are the GPS Environment Monitoring System
(GEMS), data link, altitude encoder, and Satellite
Reference Station (SRS) receiver supporting differential
GPS (DGPS) algorithms. The post-mission processing
mechanization utilizes combinations of the subsystem
measurements in an extended Kalman filter/smoother
algorithm to produce an optimal reference trajectory.
Data Link
Real-Time
RRS [4]
Interrogator
( CR-100 )
DAS
Data
Acquisition
System
( PC-104 )
Reference Pallet ConfigurationSatellite Reference Station (SRS)
Post-Mission Processing
GPS
Receiver
Code / Carrier
Satellites
Display
Real-Time
Altitude
Encoder
BM
Refer e nc e
Survey
INS
DGPS
RRS
INS
DGPS
RRS
Post-Process
Post-Process
Pre-Process
Pre-Process
Extended
Kalman Filter
Smoother
Extended
Kalman Filter
Smoother
Reference
Trajectory
GEMS
GPS Environment
Measurement
System
INS [3]
Enhanced SNU
EGI [1]
INS
GPS Receiver
Code / Carrier
Loosely/Tightly Integrated System
GPS [2]
Receiver
Code / Carrier
Figure 6 CRS Processing Mechanization
Nominal performance accuracies of the reference
trajectory characterized for JAMFEST are detailed in
Figure 7.
1.701.001.40[4] RRS
SRS Range Constraints: 1 300-500 nm 2 50-100 nm
3.252.252.00[1] [2] GPS Code
[1] [2] DGPS Code1
Carrier 2
Subsystem
Configuration3DVertHorz
0.350.200.30
2.501.751.75
RMS Position (m)
0.0100.0050.0050.005[3] INS/ESNU
Attitude Accuracy: 20 arcsec ( Roll,Pitch,Heading )
RMS Velocity (m/s)
Subsystem
Configuration
0.0170.0100.0100.010[1] INS/EGI
3DUpNorthEast
Figure 7 Reference System Accuracies
3 EVENT CONDUCT
JAMFEST testing began on 24 May 04 at 2000 MST and
spanned 5 days. A total of 12 military organizations,
DoD contractors, and civil agencies participated, all with
very different goals and objectives.
During the test week, 746 TS engineers conducted GPS
jamming operations from 2000 to 0400 hours on each test
day, and characterized the jamming field with ground and
aviation monitoring equipment. Additionally, the 746 TS
deconflicted all customer flight and ground operations
and provided on-site technical experts to help resolve
customer difficulties and ensure each objective was met.
In some cases, this required significant instrumentation
and analysis support.
On each test day, two types of scenarios were offered:
(1) Operationally realistic and (2) Experimental
scenarios. Operationally realistic scenarios included
threat laydowns consisting of one, four, and seven
jammers broadcasting on L1 and L2 frequencies and
using a variety of waveforms and power levels.
Experimental scenarios, on the other hand, were useful
for research and development efforts requiring high
jamming levels capable of stressing robust anti-jam
electronics. These scenarios were achieved by using
seven close-proximity jammers focused in the same
direction.
Most JAMFEST participants utilized their own test beds
and recorded their own receiver data and reference
information. These participants either mounted their
equipment in rental vehicles, government vehicles and
aircraft or walked through the jamming environments. In
other cases, the 746th TS provided support to participants
who could not supply their own test beds, data collection
systems, or reference data. In this situation, customer
assets were mounted into the 746 TS land navigation
vehicles. Customer assets were connected to FRPAs,
CRPAs or prototype antennas, depending on the
customer’s desires and asset availability.
The jamming scenarios were carefully developed to
maximize efficiency and meet everyone’s goals. A total
of 59 jamming scenarios with different threat laydowns
were executed during the test week. Jammer placement
was carefully planned to maximize the number and
variety of scenarios offered while minimizing relocation
and set-up time. Figure 8 depicts three sample jammer
placement scenarios.
Utilizing a configuration similar to the one depicted,
permitted the execution of one jammer, three jammer and
seven jammer scenarios without relocating any of the
jammers. This offered the most scenario flexibility while
limiting the number personnel required to operate the
jammers at these locations. For example, in a one
jammer scenario, only the jammer at TX 8 may be used
or in a three jammer scenario, the jammers at TX 6, TX 7
and TX 1 may be used. Lastly, in a seven jammer
scenario the jammers at TX 1, TX 2, TX 3, TX 4, TX 5,
TX 6, and TX 8 may be used. Typically, when these
jammers were turned on, vehicles would drive down the
corresponding range road, park at a predesignated
location or fly though the jamming field. While most
participants drove or flew during testing, other
participants tested hand-held receivers and walked near
the jamming field.
During testing, the jammer configuration alternated
between operationally realistic and experimental
scenarios. All scenarios utilized a variety of waveforms
44 Journal of Global Positioning Systems
at low, medium, high, and ramped power levels. The
specific waveforms broadcast included Bi-Phase Shift
Key, Broadband, Partial Band, Continuous Wave and
Swept Continuous Wave, and Pulsed Continuous Wave
on both L1 and L2 frequencies.
Figure 8 Sample Jammer Laydown
Another jammer laydown used, involved placing multiple
jammers along a predesignated range road all pointed in
the same direction. Participants drove into and out of the
field to test their equipment in a concentrated GPS
jamming environment. Regardless of the means or
scenarios used, the participants successfully met their
objectives.
Following each test day, 746 TS personnel checked
ground jammer logs and collected reference data for
accuracy and proper format and provided this information
to each participant in the form of a data package. The
purpose of the data package was to accurately document
the event, cite any necessary deviation(s) from the test
plan, detail exact scenarios as they are transmitted, and
provide reference data that describes the signals received.
Information in the data package was sufficient for each
participant to evaluate their own data and generate
defensible conclusions.
4 SUMMARY
JAMFEST serves as an affordable avenue to identify
system limitations in a GPS jamming environment so that
system designers and users can begin to identify and
mitigate vulnerabilities in their specific applications.
This is particularly valuable information to civil users
who otherwise would not have access to such
vulnerability scenarios. After participating in JAMFEST
customers are better armed with realistic vulnerability
data, to better understand their system limitations, work
to mitigate these effects, and apply backup systems or
procedures as appropriate.
In addition to civil GPS users, JAMFEST also benefited
operational military units who are likely to experience
GPS jamming during operational conflicts but may not
have actually experienced the effects of jamming during
training maneuvers. Training in such electronic warfare
environments raises vulnerability awareness and affords
the opportunity to devise, implement, and practice
countermeasures.
All participants reached their objectives and praised the
planning, organization and execution of JAMFEST. The
participants agreed that the event was worthwhile and
indicated that they would be interested in attending future
JAMFESTs.
As long as there is interest in GPS vulnerabilities, the 746
TS plans to conduct JAMFEST events. Although the first
JAMFEST was in essence “free” to the participants, there
may be a nominal fee associated with future test events.
The fee is contingent upon sponsorship from other
organizations and the complexity of testing or analysis
desired by the participants.
Future JAMFESTs will focus on expanding the
participant base to include not only the operational and
test communities, but add US allies, civil users such as
the Dept of Transportation, power and
telecommunications industries. The next JAMFEST is
planned for November 2004 with another following in
mid-May 2005.
ACKNOWLEDGEMENTS:
The authors would like to acknowledge the support of the
GPS Joint Program Office, White Sands Missile Range,
and the 46th Test Group.
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