Research on Combination Clock Error Prediction Under Uncertain Predicted Length
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ORIGINAL PAPER
Research on Combination Clock Error Prediction Under Uncertain Predicted Length Q. Liu1* , X. Chen1, Q. Gu2, J. Sun1, Y. Zhang1 and S. Zhang1 1
Air and Missile Defense College, Air Force Engineering University, Xi’an 710051, China 2
Xiangtan Meteorological Bureau, Xiangtan 411000, China Received: 16 June 2019 / Accepted: 16 June 2020 Ó Metrology Society of India 2020
Abstract: Clock error prediction is of vital importance for the distributed netted systems’ regular operation, like netted satellites, netted radars, etc. Aiming at the problem of predicted length could not get beforehand in some conditions, we put forth a combined clock error method under uncertain predicted length. We estimate the predicted length based on the clock error data quality factor in advance. Then, we operate clock error prediction based on the combination method. If the time synchronization has reestablished earlier than the predicted length, we stop prediction immediately. And if time synchronization has not reestablished when the clock error prediction reaches the predicted length, we re-estimate the predicted length and continue prediction until time synchronization reestablishes. From examples analyses, we could get 0.3–0.5 ns around precision for one-day long precision and 0.9–1.1 ns for 2 days and 1.2–1.4 ns for 1 week. Besides, we could conclude that the combination method could flat the differences of the clocks and the difference of sole algorithms, improving the robustness of the algorithm. The combination clock error prediction method could be both applied in satellites’ clock error prediction and in other distributed netted system, especially in the condition that the predicted length could not be known before predicting, being vital to the whole systems’ performance. Keywords: Clock errors prediction; Uncertain predicted length; Combination method; Time synchronization 1. Introduction Clock error prediction is an important measure to manage the distributed netted system time synchronization operation, like netted satellites [1, 2], precise point positioning (PPP) system [3–6] and netted radar system [7, 8], etc. This is because some stations in the distributed netted system could not transfer time messages with others in some conditions, like satellites will move to the hemisphere of back to earth. Then, they have to operate clock error prediction to maintain time synchronization with the system. As for clock error predictions, in order to improve IGU-P clock products, Wang et al. [9] put forth an algorithm employing a wavelet neural network and single difference clock sequence, which improved the precision and stability of IGU-P clock products. As for outages of real-time service stream, Nie et al. [10] put forth an alternate approach for GPS clock prediction, which improved the predicted
precision by about 50% corresponding to IGU products. Aiming at the periodic influences on satellite clock, Lu et al. [11] put forth a fusion clock error prediction method based on preprocessing by empirical mode decompo
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