• Adaptive Estimation of Signals of Opportunity 

      Kassas, Zaher M.; Ghadiok, Vaibhav (2014-04)
      To exploit unknown ambient radio frequency signals of opportunity (SOPs) for positioning and navigation, one must estimate their states along with a set of parameters that characterize the stability of their oscillators. ...
    • Analysis of Ionospheric Scintillations using Wideband GPS L1 C/A Signal Data 

      Humphreys, Todd E.; Ledvina, Brent M.; Psiaki, Mark L.; Kintner, Paul M. (2004)
      A non-real-time GPS receiver has been developed and tested for use in scintillation analysis. The receiver consists of a digital storage receiver and non-real-time software acquisition and tracking algorithms. The goal ...
    • Assessing the Spoofing Threat: Development of a Portable GPS Civilian Spoofer 

      Humphreys, Todd E.; Ledvina, Brent M.; Psiaki, Mark L.; O'Hanlon, Brady W.; Kintner, Paul M. (2008)
      A portable civilian GPS spoofer is implemented on a digital signal processor and used to characterize spoofing effects and develop defenses against civilian spoofing. This work is intended to equip GNSS users and receiver ...
    • A Blueprint for Civil GPS Navigation Message Authentication 

      Kerns, Andrew J.; Wesson, Kyle D.; Humphreys, Todd E. (2014-05)
      A proposal for civil GPS navigation message authentication (NMA) is presented with sufficient specificity to enable near-term implementation. Although previous work established the practicality and efficacy of NMA for ...
    • CASES: A Novel Low-Cost Ground-based DualFrequency GPS Software Receiver and Space Weather Monitor 

      Crowley, Geoff; Bust, Gary S.; Reynolds, Adam; Azeem, Irfan; Wilder, Rick; O'Hanlon, Brady W.; Psiaki, Mark L.; Powell, Steven; Humphreys, Todd E.; Bhatti, Jahshan A. (2011)
      GPS receivers can be used for monitoring space weather events such as TEC variations and scintillation. This paper describes the new GPS sensor developed by ASTRA, Cornell and UT Austin. The receiver is called “Connected ...
    • CASES: A Smart, Compact GPS Software Receiver for Space Weather Monitoring 

      O'Hanlon, Brady W.; Psiaki, Mark L.; Powell, Steven; Bhatti, Jahshan A.; Humphreys, Todd E.; Crowley, Geoff; Bust, Gary S (2011)
      A real-time software-defined GPS receiver for the L1 C/A and L2C codes has been developed as a low-cost space weather instrument for monitoring ionospheric scintillation and total electron content. The so-called CASES ...
    • Centimeter Positioning with a Smartphone-Quality GNSS Antenna 

      Pesyna, Kenneth M. Jr; Heath, Robert W. Jr.; Humphreys, Todd E. (2014-09)
      This paper demonstrates for the first time that centimeteraccurate positioning is possible based on data sampled from a smartphone-quality Global Navigation Satellite System (GNSS) antenna. Centimeter-accurate ...
    • Characterization of Receiver Response to Spoofing Attacks 

      Shepard, Daniel (2011-05)
      Test procedures are developed for characterizing the response of civil GPS receivers to spoofing attacks. Two response characteristics are analyzed in detail for four representative GPS receivers: (1) the aggressiveness ...
    • Characterization of Receiver Response to Spoofing Attacks 

      Shepard, Daniel; Humphreys, Todd (The Institute of Navigation, 2011-10)
      Test procedures are developed for characterizing the response of civil GPS receivers to spoofing attacks. Two response characteristics are analyzed in detail for four representative GPS receivers: (1) the spoofer power ...
    • Characterization of Receiver Response to Spoofing Attacks 

      Shepard, Daniel P.; Humphreys, Todd E. (2011)
      Test procedures are developed for characterizing the response of civil GPS receivers to spoofing attacks. Two response characteristics are analyzed in detail for four representative GPS receivers: (1) the spoofer power ...
    • Civilian GPS Spoofing Detection based on DualReceiver Correlation of Military Signals 

      Psiaki, Mark L.; O'Hanlon, Brady W.; Bhatti, Jahshan A.; Shepard, Daniel P.; Humphreys, Todd E. (2011)
      Cross-correlations of unknown encrypted signals between two civilian GNSS receivers are used to detect spoofing of known open-source signals. This type of detection algorithm is the strongest known defense against so ...
    • Considerations for Future IGS Receivers 

      Humphreys, Todd E.; Young, Larry; Pany, Thomas (2008)
      Future IGS receivers are considered against the backdrop of GNSS signal modernization and the IGS’s goal of further improving the accuracy of its products. The purpose of this paper is to provide IGS members with a guide ...
    • Constructing a Continuous Phase Time History from TDMA Signals for Opportunistic Navigation 

      Pesyna, Kenneth M. Jr; Kassas, Zaher M.; Humphreys, Todd E. (2012-04)
      A technique is developed for reconstructing a continuous phase time history from the noncontinuous phase bursts of time division multiple access (TDMA) signals. A continuous phase time history facilitates exploitation ...
    • Constructing a Continuous Phase Time History from TDMA Signals for Opportunistic Navigation 

      Pesyna, Kenneth; Kassas, Zaher; Humphreys, Todd (Constructing a Continuous Phase Time History from TDMA Signals for Opportunistic NavigationIEEE/ION PLANS Conference, 2012-04)
      A technique is developed for reconstructing a continuous phase time history from the noncontinuous phase bursts of time division multiple access (TDMA) signals. A continuous phase time history facilitates exploitation of ...
    • Data-Driven Generalized Integer Aperture Bootstrapping for Real-Time High Integrity Applications 

      Green, G. Nathan; King, Martin; Humphreys, Todd E. (2016-04)
      A new method is developed for integer ambiguity resolution in carrier-phase differential GPS (CDGPS) positioning. The method is novel in that it is (1) data-driven, (2) generalized to include partial ambiguity resolution, ...
    • A Dense Reference Network for Mass-Market Centimeter-Accurate Positioning 

      Murrian, Matthew J.; Gonzalez, Collin W.; Humphreys, Todd E.; Novlan, Thomas D. (2016-04)
      The quality of atmospheric corrections provided by a dense reference network for centimeter-accurate carrierphase differential GNSS (CDGNSS) positioning is investigated. A dense reference network (less than 20 km ...
    • Development and Demonstration of a TDOA-Based GNSS Interference Signal Localization System 

      Bhatti, Jahshan A.; Humphreys, Todd E.; Ledvina, Brent M. (2012)
      Background theory, a reference design, and demonstration results are given for a Global Navigation Satellite System (GNSS) interference localization system comprising a distributed radio-frequency sensor network that ...
    • Development and Field Testing of a DSP-Based Dual-Frequency Software GPS Receiver 

      O'Hanlon, Brady W.; Psiaki, Mark L.; Kintner, Paul M.; Humphreys, Todd E. (2009)
      A real-time software GPS receiver for the L1 C/A and L2 C codes has been implemented on a Digital Signal Processor (DSP) and tested in both scintillating and nonscintillating environments. This receiver is being developed ...
    • Evaluating GPS Receiver Robustness to Ionospheric Scintillation 

      Hinks, Joanna C.; Humphreys, Todd E.; O'Hanlon, Brady; Psiaki, Mark L.; Kintner, Paul M. (2008)
      A method for testing GPS receivers for ionospheric scintillation robustness has been implemented using a GPS signal simulator and a statistical model that captures the characteristics of scintillation relevant to ...
    • Evaluation of Smart Grid and Civilian UAV Vulnerability to GPS Spoofing Attacks 

      Shepard, Daniel P.; Bhatti, Jahshan A.; Humphreys, Todd E.; Fansler, Aaron A. (2012)
      Test results are presented from over-the-air civil GPS spoofing tests from a non-negligible stand-off distance. These tests were performed at White Sands Missile Range (WSMR) against two systems dependent on civil GPS, ...