Performance Evaluation of LEO-Aided GPS Direct Position Estimation in Degraded Signal Environments

J. Tanner Koza, Samuel Morgan, and Scott Martin

Peer Reviewed

Abstract: Due to their low received signal power, Global Navigation Satellite Systems (GNSS) are easily subject to radio frequency interference (RFI). Subsequently, extensive research regarding advanced receiver designs that mitigate RFI is ubiquitous. Among these designs is the Direct Position Estimation (DPE) architecture, which addresses the shortcomings of conventional receivers by jointly processing all channels and estimating the receiver state in a single step. Combining each channel’s received power, this single-step methodology proves more robust than receivers that fuse measurements from independently processed channels in two steps. Despite this robustness, DPE can still succumb to the effects of RFI. This paper discusses the performance capabilities of a DPE architecture that utilizes low Earth orbit (LEO) positioning, navigation, and timing (PNT) signals to supplement the Global Positioning System (GPS) in various RFI scenarios. The architecture’s performance is evaluated using a Monte Carlo analysis that employs a correlator-level simulation of GPS L1 C/A and a dedicated LEO PNT signal. It is shown that including this LEO signal substantially reduces the root-mean-squared errors (RMSE) associated with the estimated position, velocity, and timing (PVT) states in high GPS attenuation regimes compared to other architectures. Specifically, the proposed architecture is compared to standalone GPS DPE, LEO-aided GPS Vector Processing (VP), and standalone GPS VP. The VP comparison is included to gauge performance against a two-step methodology. The subsequent results also indicate that the probability of tracking GPS in the scenario with the highest RFI increases by up to 85.12 % compared to these architectures. In addition, a methodology that prevents the obfuscation of GNSS information by high-powered LEO signals in a DPE architecture is presented. Furthermore, the open-source navigation simulation library navsim is introduced.
Published in: Proceedings of the ION 2024 Pacific PNT Meeting
April 15 - 18, 2024
Hilton Waikiki Beach
Honolulu, Hawaii
Pages: 745 - 757
Cite this article: Koza, J. Tanner, Morgan, Samuel, Martin, Scott, "Performance Evaluation of LEO-Aided GPS Direct Position Estimation in Degraded Signal Environments," Proceedings of the ION 2024 Pacific PNT Meeting, Honolulu, Hawaii, April 2024, pp. 745-757.
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