Towards a Complete Virtual Multipath Analysis Tool

Bruce M. Hannah, Rodney A. Walker, Kurt Kubik

Abstract:	It has been previously shown[1] that the Parabolic Equa-tion (PE) technique is well suited to solving GPS propa-gation problems over large domains. The PE provides a direct solution of Maxwell's wave equations by approxi-mating the Helmholtz scalar wave equation. This paper presents the results of a modified model, which can include the effects of the GPS antenna gain pattern and the electromagnetic properties of the ground. Com-parisons of the new PE solution with measured results are made in an open-cut mining environment. The new tech-nique is able to predict GPS C/No with high confidence. Results are also presented from the development of new techniques that allow determination of the Multipath Channel Impulse Response (MCIR) from the PE. The PE technique is a linear time invariant model, however with the use of Fourier Time synthesis techniques, time de-pendence is able to be re-instated into the model. The re-sultant model is known as the PE-based Time Analysis (PETA) model. The model is a wide-angle PE implementation optimised for GPS propagation. Multipath is characterised by am-plitude, time delay, phase, and phase rate-of-change rela-tive to the direct line-of-sight signal[2]. This model pro-vides complete decomposition of the complex electromagnetic field components into these multipath pa-rameters, through the simulation of the Multipath Channel Impulse Response. Results are presented for a variety of terrain features. A discussion is made of the aims of this project whereby a complete environmental and receiver model is developed. This model will extend from the transmission of the signal from the satellite, through the propagation medium, to the manner in which the receiver correlator interprets the sig-nal. This modelling strategy is to determine the definitive relationships between multipath propagation behaviour and its effects in the receiver. These types of effects need to be determined before innovative mitigation techniques can be considered. In conclusion the PE propagation model, in conjunction with GPS receiver models, will form the basis for a com-prehensive multipath analysis tool, necessary for compre-hensive investigation of multipath mitigation techniques.
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:	1055 - 1063
Cite this article:	Hannah, Bruce M., Walker, Rodney A., Kubik, Kurt, "Towards a Complete Virtual Multipath Analysis Tool," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1055-1063.
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