Remote Performance Evaluation of High-Precision Timekeeping Systems Based on BDS Real-Time PPP

Abstract

Highlights What are the main findings? A real-time remote monitoring and performance evaluation scheme based on BDS RTPPP is developed for high-precision timekeeping systems, in which receiver-clock constrained PPP processing is adopted for real-time station clock estimation. The developed system achieves frequency stability better than 8 × 10−15 at an averaging time of one day. Short-baseline and long-baseline BDS RTPPP performance evaluation experiments are carried out using optical-fibre and GNSS IPPP time transfer as references, respectively. Experimental results demonstrate that sub-nanosecond-level time-transfer agreement is better than 0.5 ns, enabling accurate performance evaluation of frequency deviation, frequency stability, and other metrics. What are the implications of the main findings? BDS RTPPP time transfer technique provides a flexible remote real-time performance evaluation alternative for high-precision timekeeping systems, eliminating the limitations of traditional on-site accompanying and laboratory-submitted calibration. The presented methodology serves as a vital pathway to achieve real-time traceability and quantity unification of time and frequency across wide-area networks, with broad applicability across diverse research and industry fields. Abstract Remote real-time performance evaluation of standard time and frequency is critical for full-scope time traceability and quantity unification. Conventional time and frequency calibration schemes predominantly adopt on-site accompanying calibration or laboratory submission, which are hampered by bulky equipment, high operational costs and poor flexibility, rendering them incompatible with continuous real-time monitoring and evaluation scenarios. While GNSS common-view and all-in-view techniques are available for remote performance evaluation, their limited precision cannot satisfy the demands of high-precision timekeeping systems with a frequency stability at the 10−15 level. This paper constructs a remote real-time performance evaluation system based on self-developed BDS real-time PPP (RTPPP) receivers. Two validation experiments are carried out: a 43 km short-baseline link between Lintong and Hangtian campus of the National Time Service Center (NTSC) referenced to an optical-fibre time transfer link, and a 1150 km long-baseline link between Lintong and Anhui referenced to a GNSS IPPP link. Experimental results indicate that the frequency stability of the BDS RTPPP link is better than 8 × 10−15 at an averaging time of one day. For the single hydrogen-maser timekeeping system located at Hangtian, the average frequency deviation and frequency stability measured via BDS RTPPP reach 1.93 × 10−15 and 2.07 × 10−15/1 d, respectively, showing close agreement with the independently calibrated optical-fibre reference. For the Anhui timekeeping system, the one-day average frequency deviation is 8.90 × 10−15 and frequency stability reaches 7.95 × 10−15 after one day of averaging, which are in close agreement with the GNSS IPPP reference results. The overall findings verify that BDS RTPPP based on PPP-B2b service is qualified for remote real-time performance evaluation and monitoring of high-precision timekeeping systems.