Mitigating the Effect of Multipath on the Stability of Time Transfer Using GNSS

Coordinated Universal Time (UTC) is calculated using the time data of hundreds of remote atomic clocks. These time data are generated by comparing the atomic clocks to another standard clock through time transfer. One-way time transfer using the Global Navigation Satellite Systems (GNSS) is one of the most essential and widely used time transfer techniques. The stability of the transferred time may be degraded due to many phenomena that affect GNSS signals during their path from the transmitter to the receiver. Multipath reflections are one of these phenomena that considerably degrade one way time transfer stability. It is a common notion that the fewer multipath reflections there are, the better the time transfer stability will be. This can be achieved by limiting the reception of GPS signals to high elevation satellites. In this paper, the author studied the effect of satellite elevation on time transfer stability for both GPS and Galileo. The results of this study suggest that the old shape of the relation between the elevation mask and the time transfer stability may have changed. Therefore, the author proposed a new technique for mitigating the effect of multipath on time transfer stability. The proposed technique was applied to real timing data generated from the Golden receiver of the Physikalisch-technische Bundesanstalt (PTB), which is the German national metrology institute.