Direct Position Estimation Approach: How Good Can it Get?

P. Closas, C. Fernández-Prades, J.A. Fernández-Rubio

Abstract:	In this paper we compare two alternative positioning approaches. One is the so-called conventional two-steps approach, where the receiver computes a position after estimating the relative distance to a set of visible satellites, i.e., after synchronization. The other approach is termed Direct Position Estimation (DPE) approach and proposes to estimate, directly from the received RF/IF signal, the motion parameters of the receiver. The latter was seen to provide the receiver with appealing enhanced capabilities in scenarios of severe multipath or satellite blockages. First, the paper enumerates some drawbacks of a two-steps approach, as a motivation for DPE. Then, both signal models are presented, discussed and explained. Depending on the model considered, the resulting estimator will follow one of the two possible positioning alternatives. In Proposition 1 we will see a mathematical justification to claim that DPE outperforms a conventional two-steps approach, in the Mean Squared Error (MSE) sense. Finally, a discussion on existent accuracy bounds for unbiased estimators is given and some simulation results confirming previous discussion.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	2661 - 2667
Cite this article:	Closas, P., Fernández-Prades, C., Fernández-Rubio, J.A., "Direct Position Estimation Approach: How Good Can it Get?," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2661-2667.
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