IEEE - Aerospace and Electronic Systems - July 2022 - 4

Feature Article:
DOI. No. 10.1109/MAES.2022.3154110
I Am Not Afraid of the GPS Jammer: Resilient
Navigation Via Signals of Opportunity in GPS-Denied
Environments
ZaherM. Kassas , Joe Khalife , and Ali A. Abdallah , University of
California, Irvine, CA 92697, USA
Chiawei Lee
, U.S. Air Force Test Pilot School, Edwards, CA 93524, USA
INTRODUCTION
Global navigation satellite systems (GNSS) are at the heart
of numerous technologies that fuel our modern day life. It
is estimated that there are currently about 8 billion GNSS
devices worldwide, reaching 9 billion by 2025. The economic
benefits of GPS to the U.S. private sector between
1984 and 2017 is estimated to be nearly $1.8 trillion, and
15 ofthe 18 U.S. critical infrastructures rely on GPS. While
losing accurate positioning, navigation, and timing (PNT)
can be a nuisance in nonsafety critical applications, the
impact can be catastrophic in safety-critical applications,
such as transportation, aviation, military operations, among
others. Over the last few years, GNSSjamming and spoofing
incidents have been happening with increasing frequency,
exposing the inherent vulnerabilities of GNSS,
and rendering them a single point of failure [1]-[4]. GNSS
jamming and spoofing have affected hundreds ofvessels in
South Korea; disrupted navigation over the South China
Sea islands; caused chaos on smartphones and rideshares in
Moscow; put tens of vessels into disarray in the Black Sea;
caused dozens of unmanned aerial vehicles (UAVs) to
plummet during a Hong Kong air show, resulting in hundreds
of thousands of dollars in damages; are suspected to
have been utilized to hijack UAVs and oil tankers in the
Authors' current addresses: Zaher M. Kassas, Joe Khalife,
and Ali Abdallah are with the Department of Mechaincal
andAerospace Engineering, University of California, Irvine,
Irvine, CA 92697 USA (e-mails: zkassas@ieee.org; jjkhali
fe@gmail.com; abdalla2@uci.edu); Chiawei Lee is with the
U.S. Air Force Test Pilot School, Edwards, CA 93524 USA
(e-mail: chiawei.lee@us.af.mil).
Manuscript received June 8, 2021, revised October 23,
2021; accepted February 2, 2022, and ready for publication
February 22, 2022.
Review handled by Jason Gross.
0885-8985/22/$26.00 ß 2022 IEEE
4
Persian Gulf; disrupted airport operations around the
world; and are becoming commonplace in military conflict
[5]. What is particularly alarming is that jamming and
spoofing are no longer confined to sophisticated rogue
organizations, with jammers being sold online and marketed
as personal privacy devices, and hackers publishing
spoofing software-defined radio (SDR) code online.
Today's navigation systems, particularly those onboard
ground, aerial, and surface vehicles, fuse information from
a GNSS receiver and an inertial measurement unit (IMU)
[6]. The integration ofthese two systems, typically referred
to as a GNSS-aided inertial navigation system (INS), takes
advantage ofthe complementary attributes ofeach system:
the long-term stability of a GNSS navigation solution aids
the short-term accuracy of an INS. Sensors (e.g., cameras,
lasers, sonar, and odometers) have been commonly adopted
to supplement a navigation system for the inevitable event
that GNSS signals become unreliable or unavailable. These
sensors could be used to extract relative motion information
to reduce the INS's error divergence rate. However,
they are still dead-reckoning-type sensors; therefore, during
prolonged periods of GNSS outage, the error would
eventually diverge. Moreover, these sensors only provide
local position estimates, may not properly function in all
environments (e.g., fog, snow, rain, dust, nighttime, etc.),
and are still susceptible to malicious spoofing attacks [7].
Signals of opportunity (SOPs) have been considered to
enable navigation whenever GNSS signals become
unavailable or unreliable [8]. SOPs are ambient radio signals
that are not intended for navigation or timing purposes,
such as AM/FM radio [9], [10], WiFi [11], [12],
cellular [13]-[16], digital television [17], [18], and lowEarth
orbit (LEO) satellite siganls [19]-[21]. In contrast to
the aforementioned dead-reckoning-type sensors, absolute
position information could be extracted from SOPs to provide
bounded INS errors. Moreover, many SOPs are practically
unaffected by dense smoke, fog, rain, snow, and
other poor weather conditions.
IEEE A&E SYSTEMS MAGAZINE
JULY 2022
https://orcid.org/0000-0002-4388-6142 https://orcid.org/0000-0003-3519-256X https://orcid.org/0000-0002-6364-3818 https://orcid.org/0000-0003-2426-0934
IEEE - Aerospace and Electronic Systems - July 2022

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