Abstract
: Multipath is the primary range error constraining the accuracy of differential GPS systems. This has been an important motivating factor in the development of receiver and antenna technologies to mitigate multipath errors. This paper describes the results of a study of GPS receiver multipath error envelopes, measured employing a high-resolution technique for use with laboratory-environment GPS signal simulators, and their consistency with multipath errors observed at the Federal Aviation Administration's (FAA) Wide Area Augmentation System (WAAS) reference sites. Using the WAAS reference receiver, the effects of receiver bandwidth, correlator spacing, very short or extended multipath delays, autocorrelation function sidelobes, and multiple specular reflections were explored. Test results showed good agreement among theoretical, experimental, and field-observed multipath error estimates, and illustrated the characteristics and impact of the variety of multipath mitigating receiver technologies employed in the WAAS receiver. The results are widely applicable to GPS receiver designs in general, and to other differential systems, such as the FAA's Local Area Augmentation System. Results confirmed that measurements from the WAAS reference sites are dominated by close-in multipath and multiple reflections. New multipath mitigation techniques, such as ultra-narrow correlator spacing and refined receiver algorithms, coupled with new antenna designs, have the potential for further reducing multipath errors at differential reference sites.
Published Version
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