Rapid Direct P(Y)-Code Acquisition In a Hostile EnvironmentIn a Hostile Environment

Robert Wolfert, Steve Chen, Sanjai Kohli, Don Leimer, James Lascody

Abstract:	Due to its higher tolerance to intentional jamming and spoofing compared to the C/A-code, direct acquisition of the GPS P(Y)-code is a desirable capability for military users. In the past, direct acquisition of the P(Y)-code was impractical due to insufficient user time source accuracy, resulting in lengthy code searches due to the large time errors. Recent advances in the transfer of user time and improvements in time maintenance using stable, low power time sources have eliminated much of the user time uncertainty. These advances, coupled with the use of massively parallel correlator technology have made direct acquisition of the P(Y)-code possible. Difficulties still exist as even small time errors can lead to large search spaces for the P(Y)-code. Small errors in the user reference frequency compound the problem by requiring a frequency search since the long integration periods required to combat the effects of a hostile jamming environment necessitate narrower frequency coverage in each search pass. Using massively parallel correlator technology to implement a two-dimensional search, the STS Y-EXPRESS receiver can search 32,000 time-frequency bins in parallel to directly acquire the P(Y)-code in a short time. This paper examines the problems encountered with the practical implementation of massively parallel correlator technology. Data collected in simulations of the Y-EXPRESS signal processor under benign conditions is extrapolated for signal acquisition at J/S values in excess of 50 dB. Data analysis shows both benefits and limitations of massively parallel correlator technology and the feasibility of implementing two-dimensional searches.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	353 - 360
Cite this article:	Wolfert, Robert, Chen, Steve, Kohli, Sanjai, Leimer, Don, Lascody, James, "Rapid Direct P(Y)-Code Acquisition In a Hostile EnvironmentIn a Hostile Environment," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 353-360.
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