The GPS Assimilator: A Method for Upgrading Existing GPS User Equipment to Improve Accuracy, Robustness, and Resistance to Spoofing

T.E. Humphreys, J.A. Bhatti, B.M. Ledvina

Abstract:	A conceptual method is presented for upgrading exist- ing GPS user equipment, without requiring hardware or software modi¯cations to the equipment, to improve the equipment's position, velocity, and time (PVT) accuracy, to increase its PVT robustness in weak-signal or jammed environments, and to protect the equipment from coun- terfeit GPS signals (GPS spoo¯ng). The method is em- bodied in a device called the GPS Assimilator that cou- ples to the radio frequency (RF) input of an existing GPS receiver. The Assimilator extracts navigation and timing information from RF signals in its environment|including non-GNSS signals|and from direct baseband aiding pro- vided, for example, by an inertial navigation system, a frequency reference, or the GPS user. The Assimilator optimally fuses the collective navigation and timing infor- mation to produce a PVT solution which, by virtue of the diverse navigation and timing sources on which it is based, is highly accurate and inherently robust to GPS signal ob- struction and jamming. The Assimilator embeds the PVT solution in a synthesized set of GPS signals and injects these into the RF input of a target GPS receiver for which an accurate and robust PVT solution is desired. A proto- type software-de¯ned Assimilator device is presented with three example applications.
Published in:	Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010) September 21 - 24, 2010 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	1942 - 1952
Cite this article:	Humphreys, T.E., Bhatti, J.A., Ledvina, B.M., "The GPS Assimilator: A Method for Upgrading Existing GPS User Equipment to Improve Accuracy, Robustness, and Resistance to Spoofing," Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010), Portland, OR, September 2010, pp. 1942-1952.
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