Open Access

Feedforward Delay Estimators in Adverse Multipath Propagation for Galileo and Modernized GPS Signals

  • Elena Simona Lohan1Email author,
  • Abdelmonaem Lakhzouri1 and
  • Markku Renfors1
EURASIP Journal on Advances in Signal Processing20062006:050971

https://doi.org/10.1155/ASP/2006/50971

Received: 31 May 2005

Accepted: 29 March 2006

Published: 25 May 2006

Abstract

The estimation with high accuracy of the line-of-sight delay is a prerequisite for all global navigation satellite systems. The delay locked loops and their enhanced variants are the structures of choice for the commercial GNSS receivers, but their performance in severe multipath scenarios is still rather limited. The new satellite positioning system proposals specify higher code-epoch lengths compared to the traditional GPS signal and the use of a new modulation, the binary offset carrier (BOC) modulation, which triggers new challenges in the delay tracking stage. We propose and analyze here the use of feedforward delay estimation techniques in order to improve the accuracy of the delay estimation in severe multipath scenarios. First, we give an extensive review of feedforward delay estimation techniques for CDMA signals in fading channels, by taking into account the impact of BOC modulation. Second, we extend the techniques previously proposed by the authors in the context of wideband CDMA delay estimation (e.g., Teager-Kaiser and the projection onto convex sets) to the BOC-modulated signals. These techniques are presented as possible alternatives to the feedback tracking loops. A particular attention is on the scenarios with closely spaced paths. We also discuss how these feedforward techniques can be implemented via DSPs.

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Authors’ Affiliations

(1)
Institute of Communications Engineering, Tampere University of Technology

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Copyright

© Elena Simona Lohan et al. 2006

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.