Multipath propagation is one of the major sources of error in GPS measurements. In this research, a ray-tracing technique is\nproposed to study the frequency domain characteristics of multipath propagation.The Doppler frequency difference, also known\nas multipath phase rate and fading frequency, between direct (line-of-sight, LOS) and reflected (non-line-of-sight, NLOS) signals\nis studied as a function of satellite elevation and azimuth, as well as distance between the reflector and the static receiver. The\naccuracy of the method is verified with measured Doppler differences from real data collected in a downtown environment. The\nuse of ray-tracing derived predicted Doppler differences in a receiver, as a means of alleviating the multipath induced errors in the\nmeasurement, is presented and discussed.
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