Comparison of Two Continuous GPS Carrier-Phase Time Transfer Techniques

Global Positioning System (GPS) carrier-phase (CP) time transfer, as a widely accepted high-precision time transfer method, frequently shows a data-batch boundary discontinuity of up to 1 ns, because of the inconsistency of the phase ambiguities between two consecutive data batches. To eliminate the data-batch boundary discontinuity, several techniques have been proposed in recent years. The question is how large the solutions of these techniques differ from each other and how well the solutions are faithful to clocks. To answer these questions, this paper chooses two techniques to study: Revised RINEX-Shift (RRS) technique [1-2], and Phase Common-View (Phase-CV) technique [3-4]. This paper shows that the time deviation of the difference between the two techniques is below 100 ps, for an averaging time of less than 10 days. Especially, for an averaging time of less than 1 day, the time deviation is less than 30 ps. We also find that both RRS and Phase-CV match TWSTFT (two-way satellite time and frequency transfer) and TWOTFT (two-way optical-fiber time and frequency transfer) quite well. The difference is typically within +/-0.3 ns for more than 20 days. The above results are all based on a short-distance links (less than 2500 km). A long-distance comparison between these two techniques, such as a transatlantic link, has not yet been investigated.