This paper investigates the effectiveness of multipath-decorrelating antenna motion in reducing the initialization time of Global Navigation Satellite System (GNSS) receivers employing low-cost single-frequency antennas for carrier-phase differential GNSS (CDGNSS) positioning. Fast initialization times with low-cost antennas will encourage the expansion of CDGNSS into the mass market, bringing the benefits of globally-referenced centimeter-accurate positioning to many consumer applications, such as augmented reality and autonomous vehicles, that have so far been hampered by the several-meter-level errors of traditional GNSS positioning. Poor multipath suppression common to low-cost antennas results in large and strongly time-correlated phase errors when a receiver is static. Such errors can result in the CDGNSS initialization time, the so-called time to ambiguity resolution (TAR), extending to hundreds of seconds—many times longer than for higher- cost survey-grade antennas, which have substantially better multipath suppression. This paper demonstrates that TAR can be significantly reduced through gentle wavelength-scale random antenna motion. Such motion acts to decrease the correlation time of the multipath-induced phase errors. A priori knowledge of the motion profile is shown to further reduce TAR, with the reduction more pronounced as the initialization scenario is more challenging.

Cite and download the paper:
K. M. Pesyna, Jr., T. Novlan, C. Zhang, R. W. Heath, Jr., and T. E. Humphreys, "Exploiting antenna motion for faster initialization of centimeter-accurate GNSS positioning with low-cost antennas," IEEE Transactions on Aerospace and Electronic Systems, vol. 3, Aug. 2017


We propose a simple low-cost technique that enables civil Global Positioning System (GPS) receivers and other civil global navigation satellite system (GNSS) receivers to reliably detect carry-off spoofing and jamming. The technique, which we call the Power-Distortion detector, classifies received signals as interference-free, multipath-afflicted, spoofed, or jammed according to observations of received power and correlation function distortion. It does not depend on external hardware or a network connection and can be readily implemented on many receivers via a firmware update. Crucially, the detector can with high probability distinguish low-power spoofing from ordinary multipath. In testing against over 25 high-quality empirical data sets yielding over 900,000 separate detection tests, the detector correctly alarms on all malicious spoofing or jamming attacks while maintaining a <0.5% single-channel false alarm rate.

Cite and download the paper:
K. D. Wesson, J. Gross, T. E. Humphreys, and B. L. Evans, " GNSS Signal Authentication via Power and Distortion Monitoring," 2017. Submitted for review.


54 percent of the world’s population lives in urban areas, a proportion that is expected to increase to 66 percent by 2050. However, mobile positioning in urban environments continues to be a frustrating experience for users.

Dr. Humphreys recently spoke at the Urban Navigation Panel at the ION GNSS+ 2016 conference to discuss the problem of urban navigation.

Download the presentation.

Dr. Humphreys and Lakshay Narula recently presented this poster at the 2016 Texas Wireless Summit regarding Secure Perception in Connected Vehicles.

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Dr. Humphreys was recently invited to speak at the ION GNSS+ 2016 conference during the UAV Navigation Invited Speakers Session. Don't let the title mislead you: this presentation covers much more than just UAVs.

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