Features of Assured Timing Systems for Communication Networks

S. Yu. Medvedev, K. G. Mishagin, A. V. Ryzhkov, B. A. Sakharov, M. L. Schwartz

Transactions of IAA RAS, issue 70, 19–24 (2024)

DOI: 10.32876/ApplAstron.70.19-24

Keywords: digital communications, clock synchronization, time scale, frequency standard, PRTC (Primary Reference Time Clock), APNT (Assured Positioning, Navigation and Timing), spoofing

Abstract

To ensure the functioning of modern communication networks, special systems of frequency (clock) and time (phase) synchronization are implemented, which are usually based on the use of global navigation satellite systems (GNSS) receivers. However, such systems cannot be considered reliable due to various interferences that affect GNSS receivers and lead to a complete loss of synchronization. Alternative solutions for high-precision time-frequency systems are required. One such solution is proposed in this paper. The paper analyzes available technologies and requirements for time-frequency support of modern communication systems. Using numerical simulation and qualitative estimates, the expected time of autonomous keeping of the atomic time scale for a given accuracy is studied. As a result of the analysis, it was concluded that a promising solution to the problem of ensuring the reliability of the frequency-time synchronization system is the use of a leading network clock based on precision time keepers – quantum frequency standards corrected relative to UTC with a sufficiently long period while monitoring the quality of the received signal. The use of passive hydrogen frequency standards will make it possible to carry out corrections approximately once every two weeks, or less frequently, if the allowable deviation of the time scale from UTC is not more than 100 ns. To improve the reliability of the system, it is proposed to use two frequency standards and an additional spoofing interference detection device. The considered structure of the system for forming and correcting the time scale of the leading network clock based on APNT technology can form the basis for future coherent time-frequency systems that will improve the reliability of the formation of a single time scale and reference frequency for a public communication network.

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