GNSS Code and Carrier Tracking in the Presence of Multipath

Gary Brodin

Abstract:	It is well known that multipath represents a major error source in differential GNSS positioning. Errors produced are unique to each antenna position and so are uncorrelated between the reference station and the mobile receiver. Reduction techniques, such as narrow correlator spacing[ 1] and the multipath estimating delay lock loop (MEDLL)[2] have improved the situation. However, reflected signals emanating close to the antenna are not reduced by either technique. Carrier multipath is particularly a problem as short delay multipath signals cause maximum carrier errors. This paper describes the analysis that has been carried out into code and carrier tracking in the presence of multipath. Code tracking in this situation produces a non-zero mean error[3]. The source of this bias has been investigated. Code and carrier multipath errors of the Global Orbiting Navigation Satellite System (GLONASS) have been compared with those of the Global Positioning System (GPS). The effects of pre-correlation filtering on code and carrier multipath errors have been determined using data from a measured correlation function. Also discussed is the multipath fading bandwidth. Fast and slow fading effects are presented. A comparison of the performance of typical coherent and non-coherent code discriminators in the presence of multipath has been made. The performance of the GPS and GLONASS P code signal have been determined with respect to code and carrier multipath errors.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	1389 - 1398
Cite this article:	Brodin, Gary, "GNSS Code and Carrier Tracking in the Presence of Multipath," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 1389-1398.
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