Four-constellation Reliability in Challenging GNSS Signal Environments and the Estimation of Inter-system Time-offsets

摘要

The increased in number of ranging signals from newGNSS constellations is expected to result in better systemavailability especially to users in urban-canyon locations.With the new constellations, the challenges are not only tomaximize the benefit from the additional rangingobservations but also to deal with the differences amongsatellite systems such as the time-offset between thesystems.This paper investigates the system availability andreliability performance of current GPS-GLONASSconstellation with additional satellites from Medium EarthOrbit BeiDou and Galileo. The performance of GPSGLONASSwith complete and partial Galileo and BeiDouare investigated. A covariance simulation method isapplied and challenging urban-canyon environments arespecifically considered. Moreover, the paper also analysesthe effect of the between-system time-offset on systemavailability and the reliability of the position solution. Thestandard operation when the clock bias parameters foreach GNSS are estimated by the receiver at each epochand when the clock bias values are provided to thereceiver as a priori information to use during the timewhen the receiver sees a limited number of satellites areexamined using real GPS, GLONASS and BeiDou data.