Signal Amplitude-Based Multipath Envelope Fitting: A Promising Method for Short-Delay Multipath Mitigation in Space Applications

Rui Sun, Jian Guo, and Eberhard Gill

Abstract:	Multipath is one of most unpredictable error sources in precise positioning and navigation. Its geometry-dependent property makes it difficult to be mitigated using a single technique for all the possible geometric multipath delays. The state-of-the-art mitigation techniques have proven efficient against multipath having a medium (30 m to 250 m) or large delay (> 250 m), but ineffective to short-delay (< 30 m) delay multipath. However, in practice, most of the multipath signals enter the receiver with short delays. In space applications, the receivers on the space vehicles even suffer from very-short-delay multipath (< 5 m) that is reflected from the vehicle itself or from other vehicles during the operations of rendezvous and docking. This paper proposed a new multipath mitigation method, called Signal Amplitude-based Multipath Envelope Fitting (SAMEF), which is capable of mitigating short-delay and very-short-delay multipath by up to 50%. It also exhibits a promising performance for medium or large delays as compared to other state-of-the-art methods. SAMEF is based on the fact that the signal quality values (e.g. signal amplitude) mainly contain multipath information. This information will be used to modify the correlator outputs in such a way that multiple weighted modified-correlators can be linearly combined for multipath estimation by the process of curve fitting. A simple implementation strategy for SAMEF is also proposed that operates in-conjunction with the tracking loop and has a very low computational load. The demonstration using a typical scenario in space verifies the feasibility of SAMEF and shows that SAMEF can provide a good multipath immunity for almost all geometric multipath delays larger than 1 m.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	1193 - 1205
Cite this article:	Sun, Rui, Guo, Jian, Gill, Eberhard, "Signal Amplitude-Based Multipath Envelope Fitting: A Promising Method for Short-Delay Multipath Mitigation in Space Applications," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 1193-1205.
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