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Future Directions in GNSS Research. Todd Humphreys | Aerospace Engineering The University of Texas at Austin GPS World Webinar | November 15, 2012. Acknowledgements. - PowerPoint PPT Presentation
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Future Directions in GNSS Research
Todd Humphreys | Aerospace EngineeringThe University of Texas at Austin
GPS World Webinar | November 15, 2012
• University of Texas Radionavigation Lab graduate students Jahshan Bhatti, Kyle Wesson, Ken Pesyna, Zak Kassas, Daniel Shepard, and Andrew Kerns
Acknowledgements
PNT DesiderataAvailable Everywhere
Instantaneous Fix
Secure & RobustLow Power
Cost Effective
Precise and Accurate
Kanwar Chadha, Texas Wireless Summit, Oct. 26, 2012
State of Art: uBlox UC530MAvailable Everywhere
-148 dBm acq, -165 dBm trk
Instantaneous Fix
1 second hot TTFF
Secure & Robust
CW interference removal
Low Power
66 mW continuous
Cost Effective
~$30 - $50
Precise and Accurate
2.0 m CEP with SBAS
Promising Directions for University Research
Available Everywhere
-148 dBm acq, -165 dBm trk
Instantaneous Fix
1 second hot TTFF
Secure & Robust
CW interference removal
Low Power
66 mW continuous
Cost Effective
~$30 - $50
Precise and Accurate
2.0 m CEB with SBAS
(Practically) Closed Problems
Available Everywhere
Instantaneous Fix
Secure & Robust
Low Power
Precise and Accurate 2-meter insecure rural outdoor location Elimination of ionospheric delay
– Multi-frequency open civil signals eliminate 1st-order effects
– 2nd-order effects at mm level– Ray-tracing models available for single-freq.
networked RX– Broadcast model obsolete
Data-aided carrier tracking– Half-cycle carrier tracking (e.g. Costas-loop
tracking) is outmoded– GPS L1 C/A is >99% predictable – build on-the-
fly database or get one over network – Other GNSS signals have pilot channels– One remaining open problem: Exploit coding
on L2 CM to improve L2C carrier tracking
Open Problems (1 of 4)
Available Everywhere
Instantaneous Fix
Secure & Robust
Low Power
Precise and Accurate Move sub-centimeter positioning into the mainstream– Precise positioning applications are much
bigger than surveying, mining, and geodesy – there are myriad consumer applications
– Precise positioning is not intrinsically expensive – primary cost is in non-recurring engineering
– Mainstreaming of cm-positioning will be enormously disruptive for established precise positioning providers
CDGNSS-EnabledPrecise Augmented Reality
AR Video
Open Problems (1 of 4)
Available Everywhere
Instantaneous Fix
Secure & Robust
Low Power
Precise and Accurate Move sub-centimeter positioning into the mainstream– Robustify and increase sensitivity of carrier-phase
differential GNSS (current state of art can’t handle even heavy foliage)• Overlay CDGPS engine on vectorized tracking (VDLL/VFLL
+ phase recovery), or, better yet … • Integrate CDGPS engine within vector tracking
architecture• Difference correlators offer improved robustness and
greater sensitivity. See T. Pany et al. “Difference Correlators,” May/June 2012.
– Exploit non-RF sensors to move indoors• IMUs• Cameras are cheap, pervasive. Camera central to precise
augmented reality, for which IMUs may be unnecessary.
– “Green” carrier-phase recovery – low power will enable consumer applications
Open Problems (2 of 4)
Available Everywhere
Instantaneous Fix
Secure & Robust
Low Power
Precise and Accurate Move toward cooperative signal-opportunistic PNT– Indoor problem won’t be solved by GNSS signals
alone– Might as well assume all future PNT devices will
be networked– Natural evolution of processing platform:
• Navigation processing on chip • Navigation processing on host processor • Navigation processing on cloud
– Natural evolution of tracking architecture: • Single-channel scalar tracking • Single-receiver vector tracking• Multi-receiver vector tracking
Cooperative Opportunistic Vectorized Tracking for Robust PNT
Open Problems (3 of 4)
Available Everywhere
Instantaneous Fix
Secure & Robust
Low Power
Precise and Accurate Civil GNSS receivers insecure– No commercial GNSS receiver has yet
been built with security in mind– Open GNSS signals are predictable
spoofable– Vast majority of receivers in critical
national infrastructure are GPS L1 C/A receivers
– Securing GNSS across a wide variety of application domains (e.g., low-power, low-cost, space-constrained) will remain a challenge for years to come
GNSS Spoofing
UT June 2012 Spoofing Demo
Spoofing DefensesCryptographic Non-Cryptographic
Stan
d-Al
one
Net
wor
ked
J/N Sensing(Ward, Scott, Calgary)
SSSC or NMA on WAAS(Scott, UT)
Single-Antenna Spatial Correlation(Cornell, Calgary)
SSSC on L1C(Scott)
Correlation Anomaly Defense(TENCAP, Ledvina, Torino, UT)
Sensor Diversity Defense(DARPA, BAE, UT)
NMA on L2C, L5, or L1C(MITRE, Scott, UT)
P(Y) Cross-Correlation(Stanford, Cornell)
Multi-Element Antenna Defense(Keys, Montgomery, DLR, Stanford)
Open Problems (4 of 4)
Available Everywhere
Instantaneous Fix
Secure & Robust
Low Power
Precise and Accurate Move GPS dot from fiction to non-fiction– Dime-sized tracking device accurate to two feet
anywhere on the globe
The GPS Dot
Open Problems (4 of 4)
Available Everywhere
Instantaneous Fix
Secure & Robust
Low Power
Precise and Accurate Move GPS dot from fiction to non-fiction– Dime-sized tracking device accurate to two feet
anywhere on the globe– Competing goals ensure that dots will offer
interesting research challenges for years to come:• High sensitivity vs. small size• High sensitivity vs. low-power
– Dots could cooperate in a wireless sensor network
radionavlab.ae.utexas.edu