Fine Delay Estimation Technique Under Multipath

Z. Zhang, C.L. Law and E. Gunawan

Abstract:	In indoor or urban canyon environments, multipath signals remain to be the major source which degrades the positioning accuracy in GPS. Narrow correlator technique is simple and easy to be implemented, but its tracking error for one short-delay multipath signal with a multipath-to-direct ratio of 0.5 can be up to 8 meters. Other technique, such as Peak Tracking with Measurement Compensation (PTMC), also has no significant improvement on mitigating short-delay multipath signal. Although the multipath mitigation performance of Multipath Estimation Delay Lock Loop (MEDLL) is satisfactory, its computation load is too high. In this paper, a new technique for reducing the Pseudorandom Noise (PN) code tracking error caused by multipath is presented under the assumption that the side lobes of the PN code autocorrelation function can be neglected. The partial autocorrelation function of the Line-of-Sight (LOS) signal, which is not affected by multipath signals, is to be detected and estimated by using linear interpolation algorithm. Analysis shows that much simpler hardware architecture than MEDLL can be used to implement the proposed technique, and simulation results indicate that, for 25 out of the 32 PN codes used in GPS, the proposed technique has a superior performance compared with the 0.1-chip-spacing narrow correlator on mitigating multipath signals, especially the short-delay multipath signals. For the left 7 PN codes, the range error is acceptable. Therefore the proposed technique is useful for indoor positioning.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1131 - 1137
Cite this article:	Zhang, Z., Law, C.L., Gunawan, E., "Fine Delay Estimation Technique Under Multipath," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1131-1137.
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