Short-Delay Multipath Errors in NavIC Signals for Stationary Receivers

Abstract

This paper presents, in part, a tutorial overview of the code phase error and carrier phase error caused by a single reflected path and an iterative algorithm to determine the root of the well-known multipath-affected discriminator function. The algorithm is then applied to determine the code error and carrier phase error in GPS signals in a single reflected path environment, and is validated by comparing the results with the known results. The algorithm is further used to determine and illustrate single-path errors in NavIC (Navigation with Indian Constellation) signals for the first time in the literature. The NavIC errors differ significantly from the GPS errors because of the limited and slow traverses of the elevation and azimuth angles of the three geostationary and four geosynchronous NavIC satellites signals to a stationary receiver on the ground. NavIC multipath errors of a real receiver on the ground for both L5 and S1 frequencies are presented. The multipath errors of the two frequencies differ greatly because the S1 wavelength (0.12 m) is nearly half of the L5 wavelength (0.25 m) and, therefore, the S1 multipath error frequencies are nearly twice of the L5 multipath error frequencies. The real multipath errors differ from the ideal single-path ground reflection errors because, in reality, the diffractors may be multiple comprising both horizontal and vertical, and the reflections vary with time due to both elevation and azimuth of the satellite signals, causing substantial disorder in errors.

This research was supported by Space Applications Center, Indian Space Research Organization as a part of NGP-17 project. Manuscript presented at the 72nd International Astronautical Congress, Dubai, 2021-10-28. Copyright by IAF.