Analysis of the Multipath Meter Performance in the Presence of Anomalous Satellite Signals

Andy Jakab and Bryan Townsend

Abstract:	Anomalous GPS satellite signals can have a very unfavorable impact on GPS receiver integrity. In either a wide area augmentation system (WAAS), or local area augmentation system (LAAS) any differential corrections sent to other users must accurately reflect the current satellite signal integrity. Users of these systems must be warned of potentially misleading information, including both satellite failures and / or multipath, by a specific scheme designed for satellite failures detection (SFD) in the event of such an occurrence. Excessive multipath at the reference station antenna may also have an adverse impact on users of WAAS and LAAS. The Multipath Estimating Delay-Lock-Loop (MEDLL) is a method for mitigating the effects due to multipath within the receiver tracking loops. The traditional implementation of the MEDLL has been with a narrower RF bandwidth receiver that is adequate for multipath estimation but limits the detectability of anomalous satellite signals. By implementing the MEDLL algorithms on a wider bandwidth receiver, the ability to estimate multipath signals should improve as well as the ability to detect anomalous satellite signals. A theoretical multipath error envelope for this new implementation is presented. The Multipath Meter (MPM) has been described in previous papers and been shown to be a good tool for real time signal quality monitoring (SQM) and multipath detection. In order to measure multipath the MPM outputs the delay, relative amplitude, and phase of the multipath signal along with the residual values for each of correlator used in the estimation process as well as its raw and multipath corrected correlator measurements. The results show a theoretical analysis of how the multipath meter outputs are affected by various GPS satellite signal failures and the ability of the MPM to detect these satellite failures.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	541 - 551
Cite this article:	Jakab, Andy, Townsend, Bryan, "Analysis of the Multipath Meter Performance in the Presence of Anomalous Satellite Signals," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 541-551.
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