Future Directions in GNSS Research Todd Humphreys | Aerospace Engineering The 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 Desiderata Available Everywhere Instantaneous Fix Secure & Robust Low Power Cost Effective Precise and Accurate Kanwar Chadha, Texas Wireless Summit, Oct. 26, 2012

State of Art: uBlox UC530M Available Everywhere -148 dBm acq, -165 dBm trk Available Everywhere -148 dBm acq, -165 dBm trk Instantaneous Fix 1 second hot TTFF Instantaneous Fix 1 second hot TTFF Secure & Robust CW interference removal Secure & Robust CW interference removal Low Power 66 mW continuous Low Power 66 mW continuous Cost Effective ~$30 - $50 Cost Effective ~$30 - $50 Precise and Accurate 2.0 m CEP with SBAS Precise and Accurate 2.0 m CEP with SBAS

Promising Directions for University Research Available Everywhere -148 dBm acq, -165 dBm trk Available Everywhere -148 dBm acq, -165 dBm trk Instantaneous Fix 1 second hot TTFF Instantaneous Fix 1 second hot TTFF Secure & Robust CW interference removal Secure & Robust CW interference removal Low Power 66 mW continuous Low Power 66 mW continuous Cost Effective ~$30 - $50 Cost Effective ~$30 - $50 Precise and Accurate 2.0 m CEB with SBAS 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 1 st - order effects – 2 nd -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-Enabled Precise 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 – 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 Defenses Cryptographic Non-Cryptographic Stand-Alone Networked 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

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