Time Transfer based on the satellite digital TV broadcasting system

摘要

Time transfer using television (TV) signal transmitted over microwave link was first demonstrated by Tolman et. al [1] and utilizing that technique they could set the clocks to microsecond accuracy. Similar level of accuracy was also achieved with another timing system via television networks employed Line-10 as a passive time synchronization technique [2]. TV signals through geostationary satellites are also been used for precise time transfer between remote clocks [3]. With the advent of technologies, all analog TV are being replaced with digital ones and developing an easy deployable and accurate time transfer technique utilizing digital TV signal will be extremely useful for many of the applications like estimating clock offset or drift among servers and clocks. In this article we described a very simple and inexpensive method of time transfer based on the digital TV signal from the geostationary satellites. The basic principle of this kind of time transfer is that it identifies a specific part of the digital TV signal as the time marker and every time the marker signals arrive at any particular station, its time of arrival being recorded with respect to the local clock. Consider two such clocks located at two different places (Fig. 1) A and B and recording time of arrival of the marker signal from a commonly viewed geostationary satellite. If τ_A and τ_B considered to be the travelling time or delay of the marker signal from the satellite to the position A and B respectively and T_A and T_B to be the local time of arrival of that marker signal. The time offset (∇T_AB) between the two local clocks can be estimated as.