Performance Comparison of ELP and DELP for Multipath Detection

O.M. Mubarak, A.G. Dempster

Abstract:	Early Late Phase (ELP), which has recently been proposed, exploits the carrier phase difference between the line of sight (LOS) and reflected signals to detect multipath [8]. It has been found that ELP has a higher magnitude in the absence of multipath at certain Doppler offsets, termed “critical Doppler offsets” and divided into fixed and variable critical Doppler offsets. Differential ELP (DELP) has been proposed to detect multipath at critical Doppler offsets [7]. This paper statistically compares multipath detection performance of ELP and DELP for all Doppler offsets for each PRN. It has been found that DELP performs better than ELP in terms of probability of false alarm because DELP has lower magnitude at critical Doppler offsets than ELP in absence of multipath. However, DELP performance deteriorates in the presence of multipath since carrier phase from the tracking loop is used for DELP computation and it does not represent phase of the LOS signal in the presence of multipath. It has been found that DELP and ELP have similar response in terms of probability of detecting multipath. These two parameters are further analysed by using ROC curves and area under these curves. However, even in this case it is not possible to clearly identify which one performs better, as at some Doppler offsets DELP has better performance and at some ELP is better. DELP and ELP are compared at only fixed critical Doppler offsets in order to identify the Doppler offsets at which DELP can perform better. However, in this case the Doppler offsets where DELP has a better performance, is found to be dependant on multipath conditions. Thus, overall it has been found that at around half of Doppler offsets, DELP can perform better but further investigation is required to successfully identify those Doppler offsets.
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:	2276 - 2283
Cite this article:	Mubarak, O.M., Dempster, A.G., "Performance Comparison of ELP and DELP for Multipath Detection," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2276-2283.
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