Telecommunication Laboratories, Taoyuan, Taiwan, ROC.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 Jan;57(1):161-7. doi: 10.1109/TUFFC.2010.1393.
Two-way satellite time and frequency transfer (TWSTFT) is one of the major techniques to compare the atomic time scales between timing laboratories. As more and more TWSTFT measurements have been performed, the large number of point-to-point 2-way time transfer links has grown to be a complex network. For future improvement of the TWSTFT performance, it is important to reduce measurement noise of the TWSTFT results. One method is using TWSTFT network time transfer. The Asia-Pacific network is an exceptional case of simultaneous TWSTFT measurements. Some indirect links through relay stations show better shortterm stabilities than the direct link because the measurement noise may be neutralized in a simultaneous measurement network. In this paper, the authors propose a feasible method to improve the short-term stability by combining the direct and indirect links in the network. Through the comparisons of time deviation (TDEV), the results of network time transfer exhibit clear improved short-term stabilities. For the links used to compare 2 hydrogen masers, the average gain of TDEV at averaging times of 1 h is 22%. As TWSTFT short-term stability can be improved by network time transfer, the network may allow a larger number of simultaneously transmitting stations.
双向卫星时频传递（TWSTFT）是比较时频实验室原子时标的主要技术之一。随着越来越多的 TWSTFT 测量的进行，大量的点对点双向时间传递链路已经发展成为一个复杂的网络。为了提高 TWSTFT 的性能，减少 TWSTFT 结果的测量噪声非常重要。一种方法是使用 TWSTFT 网络时间传递。亚太网络是同时进行 TWSTFT 测量的一个特殊情况。一些通过中继站的间接链路由于测量噪声可能在同时测量网络中被中和，因此表现出比直接链路更好的短期稳定性。在本文中，作者提出了一种通过组合网络中的直接和间接链路来提高短期稳定性的可行方法。通过比较时间偏差（TDEV），网络时间传递的结果显示出明显改善的短期稳定性。对于用于比较 2 台氢 maser 的链路，在平均时间为 1 小时的情况下，TDEV 的平均增益为 22%。由于 TWSTFT 的短期稳定性可以通过网络时间传递得到改善，因此网络可能允许同时传输更多的站。
