Two-way Satellite Time Research Articles

Time Transfer Link fusion algorithm based on wavelet multi-resolution analysis

To raise the precision and stability of time transfer links, a wavelet-based multi-resolution data fusion technique is offered. This approach fixes the “Day-Boundary discontinuities” in global positioning system (GPS) precise point positioning (PPP) link and lessens the diurnal in Two-way satellite time and frequency transfer (TWSTFT) link by integrating the model-based dynamic system analysis method with the statistically based multi-scale signal transformation method. It can also handle data from GPS PPP links and TWSTFT links at different sampling rates. More specifically, after applying wavelet transformation to the raw data and Kalman filtering estimation on various scales, this method uses the Mallat fast reconstruction algorithm of wavelet transform to achieve the fused results. The National Time Service Center (NTSC) and the Physikalisch-Technische Bundesanstalt (PTB) handle time transfer results using this method. Experiments show that this strategy greatly improves the link's short-term stability and can manage atypical interruptions while also boosting the link's robustness and reliability, which has a wide range of possible applications.

A NavCom Signal Authentication Scheme Based on Twice Two-Way Satellite Time Transfer

Low Earth Orbit (LEO) satellite communication systems typically achieve identity authentication through the encryption and decryption of two-way information, which requires complex key management systems. In contrast, the integration of navigation and communication (NavCom) signals provides novel opportunities for physical observation and authentication solutions due to its measurement functions. This paper introduces a novel signal authentication scheme based on twice two-way satellite time transfer (TWSTT) for LEO satellite systems. It leverages the non-mutated nature of the clock difference to ascertain the legitimacy of the signal by measuring the clock difference of signals at different instances. Unlike traditional authentication methods, this approach directly exploits the temporal and spatial characteristics of the signal, negating the necessity for intricate authorization key systems. Additionally, it adeptly tackles the challenges posed by spoofing interference. The performance analysis indicates that this scheme can achieve a high detection probability for the repeater spoofing signal in the low carrier-to-noise ratio conditions.

Statistics for quantifying aging in time transfer system delays

Residual time delays in time transfer systems such as two-way satellite time and frequency transfer (TWSTFT), or GPS carrier phase (GPSCP) change over time. A double difference such as TWSTFT—GPSCP provides information on the changes in the relative time delays of the two systems. These changes are referred to as aging or time dispersion. A first difference statistic, RMS time interval error, TIERMS, provides the RMS time dispersion. The time deviation statistic (TDEV) or a variation on the Allan deviation (ADEV), referred to here as ADEVS, provide information on the nature of the random fluctuations in aging. This paper describes analytical and Monte Carlo techniques used to estimate the aging (time dispersion) from TDEV or ADEVS statistics, and finds that the aging can be more than a factor of four larger than TDEV or ADEVS. The use of ADEVS is recommended over TDEV since it is sensitive to time drift.

BDS-3 RDSS two-way time transfer with asymmetric delay compensation model

In the BeiDou navigation satellite system-3 (BDS-3) radio determination satellite service (RDSS), there exists a natural two-way link between the center station and the user site that can be used to achieve time transfer. Traditionally, RDSS two-way time transfer is realized by analogy with the two-way satellite time and frequency transfer (TWSTFT) technique. However, unlike TWSTFT, the signal propagation delays are not completely symmetrical in the RDSS two-way link because of the differences in signal emission time. In this study, a model of two-way time transfer with BDS-3 RDSS is presented. An asymmetric delay compensation method is introduced to solve the asymmetry of RDSS signals and improve the accuracy of two-way time transfer. In addition, BDS-3 RDSS common clock difference experiments are designed to test the performance of two-way time transfer with an asymmetric delay compensation model. Based on analyses of the experimental results, three conclusions can be drawn. First, the accuracy of RDSS two-way time transfer is improved when the asymmetric delay compensation model is applied. Second, BDS-3 RDSS two-way time transfers in different in-station beams and subbands do not show many discrepancies on the whole, and the standard deviation values of the BDS-3 RDSS time transfer results range from 1.7 ns to 2.6 ns for the test signals. Third, the two-way time transfer results are not generally affected by receiver coordinate errors.

Evaluation of Asia-Europe TWSTFT Links Using the Express-80 Satellite

Two-way satellite time and frequency transfer (TWSTFT) is extensively used by the Bureau International des Poids et Mesures (BIPM) in the calculation of coordinated universal time (UTC). The Asia-Europe TWSTFT links using the Express-80 satellite were reestablished in June 2021. This paper uses monthly measurements to evaluate the time comparison performance of the Asia-Europe TWSTFT network. We select TWSTFT data for analysis on the long and short baselines over the same period, respectively. Since the TWSTFT link has not been calibrated, we take the GPS precise point positioning (PPP) link, independent of TWSTFT, as a reference and align the TWSTFT results with it. Then, the results from the TWSTFT and GPS PPP solutions are compared on the different baselines. Finally, the modified Allan deviation (MDEV) and the double clock difference (DCD) between the TWSTFT link and the GPS PPP link are used to evaluate the performance of the TWSTFT results. The results show that the TWSTFT results are consistent with the results of CPS PPP time transfer, and the frequency stability of TWSTFT links on long and short baselines can reach 3E-15 or better with an averaging time of 1 d. The standard deviation of the DCD results is less than 0.4 ns on different baselines, which ensures the accuracy of the TWSTFT link. The Asia-Europe TWSTFT link can be used for UTC time transfer after calibration.

Improving BDS broadcast ephemeris accuracy using ground-satellite-link observations

The BeiDou Navigation Satellite System (BDS) employs a hybrid constellation including GEO (Geosynchronous Earth Orbit), IGSO (Inclined Geosynchronous Orbit), and MEO (Medium Earth Orbit) satellites, where the GEO and IGSO satellites are critical to providing continuous and reliable Positioning, Navigation, and Timing (PNT) services in the Asia–Pacific region. To handle the inconsistency between the satellite orbits and clocks in the broadcast ephemeris, which are determined by the Orbit Determination and Time Synchronization (ODTS) and the Two-way Satellite Time Frequency Transfer (TWSTFT) technique, respectively, we present the strategies using ground-satellite-link observations to improve the accuracy of broadcast ephemeris. The clock differences between the ODTS and TWSTFT techniques are used for correcting the radial orbit component to derive the refined orbits, which are used to generate the refined broadcast ephemeris. The test results show the precision of the refined orbits is improved by 50–60% in the 3-h to 12-h predicted arcs for the GEO satellites, and by 40–50% for the IGSO satellites. Moreover, the validation using satellite laser ranging observations shows the mean precision of the refined broadcast ephemeris is improved by 27% compared to the original one. Applying the proposed strategies in the BDS Operational Control Segment (OCS), the time evolution of BDS Single Point Positioning (SPP) in the period from Jan. 2016 to April 2021 is evaluated. The SPP accuracy is improved from 1.94, 2.06 and 3.29 m to 1.39, 1.85, and 2.39 m in the north, east, and up components, respectively. Further update with the inclusion of BDS-3 satellites improve the corresponding SPP precision to 0.68, 0.70 and 1.91 m.

A three-cornered hat analysis of instabilities in two-way and GPS carrier phase time transfer systems

A three-cornered hat analysis has been performed on three independent time transfer systems between the United States Naval Observatory (USNO) and the National Institute of Standards and Technology (NIST). These include (1) a direct Two-Way Satellite Time and Frequency Transfer (TWSTFT) link provided by the USNO, (2) an indirect TWSTFT link, and (3) GPS carrier phase (GPSCP) links. Time transfer instabilities for individual links, as quantified with the time deviation and TOTAL time deviation, have been measured for the first time for averaging periods between 2 h and 85 days. Time transfer instabilities beyond one day are roughly flicker phase in nature and generally range between 40 ps and 120 ps. Frequency transfer instabilities, as quantified by the modified Allan deviation, are observed to be as low as 1 × 10−16 for a 20 day comparison and into the mid 10−17 range at longer comparison times.

Measuring Height Difference Using Two-Way Satellite Time and Frequency Transfer

According to general relativity theory (GRT), the clock at a position with lower geopotential ticks slower than an identical one at a position with higher geopotential. Here, we provide a geopotential comparison using a non-transportable hydrogen clock and a transportable hydrogen clock for altitude transmission based on the two-way satellite time and frequency transfer (TWSTFT) technique. First, we set one hydrogen clock on the fifth floor and another hydrogen clock on the ground floor, with their height difference of 22.8 m measured by tape, and compared the time difference between these two clocks by TWSTFT for 13 days. Then, we set both clocks on the ground floor and compared the time difference between the two clocks for seven days for zero-baseline calibration (synchronization). Based on the measured time difference between the two clocks at different floors, we obtained the height difference 28.0 ± 5.4 m, which coincides well with the tape-measured result. This experiment provides a method of height propagation using precise clocks based on the TWSTFT technique.

Research on the Influence of the Residual Effects of TWSTFT on the Triangular Closure Difference

The triangular closure (TC) method of two-way satellite time and frequency transfer (TWSTFT) can be utilized to conveniently and quickly evaluate the time transfer performance between ground stations without additional equipment. To expand the application of the TC method and make it applicable to inclined geosynchronous orbit (IGSO) satellites, we analyze the influence of various residual effects of TWSTFT on the triangular closure difference (TCD). Relying on the two-way comparison network of the National Time Service Center of the Chinese Academy of Sciences, TC experiments were carried out using a geostationary orbit (GEO) satellite (CHINASAT-12) and an IGSO satellite (BDS I1-S). The results show that the Sagnac effect and ionospheric delay can be ignored without affecting the TCD, whereas the equipment delay and geometric path asymmetry effect cannot be ignored. Specifically, as a systematic error, the equipment delay has a great impact on the TCD and must be corrected. In contrast, the geometric path asymmetry effect caused by the relative motion of satellites and ground stations is small in magnitude for GEO satellites and can be ignored. However, for IGSO satellites, the geometric path asymmetry effect can reach the nanosecond level; thus, it also has a great impact on the TCD and cannot be ignored. Using the correction method proposed in this paper, subnanosecond time synchronization exactness can be achieved in TC experiments based on both types of satellites. Therefore, we have successfully expanded the application of the TC method to IGSO satellites. Theoretically, the TC method can also be applied to medium earth orbit and other satellites.

Analysis and Comparison for Fusion Algorithms of Time Transfer

In order to improve the reliability of precise time comparison, this paper takes advantage of long-term stability of TWSTFT (Two-Way Satellite Time and Frequency Transfer) and short-term stability of PPP (GPS Precise Point Positioning). Stability weighting, Vondrák-Čepek combined filtering, and Kalman filtering methods are applied to fuse the TWSTFT and GPS PPP time comparison between the NTSC (National Time Service Center) and PTB (Physikalisch-Technische Bundesanstalt). The results show that the three fusion methods all improve the diurnal variations in TWSTFT and the discontinuities in GPS PPP solution, and the absolute value of the DCD (Double Clock Difference) between fusion results and PPP solution is kept within the link calibration uncertainty. The 1d time and frequency stability of the three methods can reach the order of sub-nanosecond and 10−15, respectively. The Vondrák-Čepek fusion method has the highest stability within 1d, which is suitable for the fusion of time comparison links with requirements for short stability. Stability weighting and Kalman filtering fusion have better fidelity, which are suitable for the fusion of time comparison links that require high accuracy.

BeiDou-3 broadcast clock estimation by integration of observations of regional tracking stations and inter-satellite links

The BeiDou navigation satellite system (BDS) tracks medium earth orbit (MEO) satellites using only regional tracking stations in China. As a result, the broadcast clock accuracy of the MEO satellites decreases rapidly during the invisible arcs because of the lack of available observations. The inter-satellite link (ISL) technology of the third generation of BDS (BDS-3) can be used to extend the visible arcs of MEO satellites and to measure the relative inter-satellite clock in nearly real time. We propose a broadcast clock approach for BDS-3 by integrating observations from regional tracking stations and ISLs. The clock error between satellites is obtained through centralized estimation based on ISLs. The Ka-band hardware delay is calibrated by taking the double difference between ISL-centralized clock and the Multi-satellite Precise Orbit Determination clock. The deviation between the ISL-centralized clock and the BeiDou time is obtained using only one Two-way Satellite Time Comparison station or anchor station. To validate the algorithms, we analyze clock estimation and prediction accuracy, hardware delay stability, and time synchronization accuracy. The results show that the frequency stability of the BDS-3 onboard passive hydrogen maser (PHM) and rubidium atomic frequency standard (RAFS) is competitive to those of the GPS IIF RAFS and Galileo FOC PHM and better than those of GPS IIR RAFS. The root-mean-square error of the 2-h clock prediction is better than 0.25 ns, and the validation result relative to the post-processed precise clock product is better than 0.4 ns. The time synchronization accuracy of better than 1 ns can be obtained based on only one TSTC station or an anchor station, and the standard deviation of Ka-band hardware delay is about 0.12 ns. It is believed that the ISL and the proposed algorithms will bring a significant upgrade in the estimation of BDS-3 broadcast clock; the broadcast clock accuracy will be greatly improved, and reliance on the ground segment will also be reduced significantly.

Research on Evaluation Method of Time Transfer Performance Between Ground Stations in Two-Way Satellite Comparison Network

High-precision time synchronization between ground stations is essential for the precise measurement and determination of satellite orbits. Among the numerous time synchronization methods available, two-way satellite time and frequency transfer (TWSTFT) technology is widely used because of the approximate symmetry of its signal transmission path, such that most of the error terms can be offset to obtain subnanosecond time transmission accuracy. A C-band two-way satellite comparison network has been constructed at National Time Service Center (NTSC), Chinese Academy of Sciences for orbit determination and to compare the times between ground stations. The gradual increase in the number of ground stations has created a problem in need of urgent resolution: the facile and rapid evaluation of the time transfer performance between ground stations by a two-way satellite comparison network without the use of additional equipment. We solve this problem by applying the TWSTFT triangle closure method and the precise point positioning time transfer method to the NTSC two-way satellite comparison network and conduct joint observations between terrestrial stations to evaluate the network time transfer performance. We select the Xi'an, Kashi and Sanya stations of the NTSC two-way satellite comparison network to carry out verification tests. The results show that the NTSC two-way satellite comparison network can achieve subnanosecond time synchronization accuracy. The accuracy of time synchronization between stations can be checked conveniently and quickly without the use of additional equipment. This study presents the most recent developments for the NTSC two-way satellite comparison network and serves as a reference for evaluating the time transfer performance of similar networks.

Performance Optimization Method of Two-Way Satellite Time and Frequency Transfer Link based on Conditional Adjustment

Two-Way Satellite Time and Frequency Transfer (TWSTFT) is one of the time transfer methods with the highest accuracy at present, and it is also the main method to compare the atomic time scale among the time-keeping laboratories participated in the international atomic time calculation. Improving the short-term stability of TWSTFT links and reducing the influence of Diurnal on the link time transfer result have practical significance for optimizing the performance of TAI (International Atomic Time). In this paper, a method of TWSTFT link performance optimization based on conditional adjustment is proposed. Firstly, the optimized network of TWSTFT link performance (hereinafter briefly called as optimized network) is established according to the noise level and spectrum analysis result of TWSTFT link measurements, and then the weight coefficient matrix is set according to the analysis result of measurement noises of all the links in the optimized network to establish the conditional adjustment model. The Two-Way Satellite Time and Frequency Transfer link between the National Institute of Metrology (NIM) and the National Time Service Center (NTSC) of Chinese Academy of Sciences in the Asia-Pacific region is selected as the link to be optimized, and the TWSTFT links among NTSC, NIM, and Physikalisch-Technische Bundesanstalt (PTB) are used to compose the optimized network. The networking method and conditional adjustment model are verified by experiments. The results show that the short-term stability of the link to be optimized after adjustment is improved, and the influence of Diurnal is reduced about 24.6%. Using this method, the time transfer performance of the link to be optimized can be improved effectively.

Direct comparisons of European primary and secondary frequency standards via satellite techniques

We carried out a 26-day comparison of five simultaneously operated optical clocks and six atomic fountain clocks located at INRIM, LNE-SYRTE, NPL and PTB by using two satellite-based frequency comparison techniques: broadband Two-Way Satellite Time and Frequency Transfer (TWSTFT) and Global Positioning System Precise Point Positioning (GPS PPP). With an enhanced statistical analysis procedure taking into account correlations and gaps in the measurement data, combined overall uncertainties in the range of 1.8 × 10−16 to 3.5 × 10−16 for the optical clock comparisons were found. The comparison of the fountain clocks yields results with a maximum relative frequency difference of 6.9 × 10−16, and combined overall uncertainties in the range of 4.8 × 10−16 to 7.7 × 10−16.

A preliminary experiment of determining the geopotential difference using two hydrogen atomic clocks and TWSTFT technique

General relativity theory (GRT) concludes that a precise clock ticks at different running rates if it is under the influence of different geopotentials. Therefore, by comparing the running rates of clocks at arbitrary two stations, the geopotential difference between them can be determined. In this study, with the help of two hydrogen atomic clocks (noted as H-masers), using the two-way satellite time and frequency transfer (TWSTFT) technique, we carried out experiments of the geopotential difference determination at the China Aerospace Science & Industry Corporation (CASIC), Beijing. Here the ensemble empirical mode decomposition (EEMD) method is adopted to remove periodic signals included in the original observations. Finally, the clock-comparison-determined geopotential difference in the experiments is determined. Results show that the difference between the geopotential difference determined by GRT and that determined by measuring tape is about 1316.1 ± 931.0 m2s-2, which is equivalent to 134.3 ± 95.0 m in height, and in consistence with the stability of the H-masers applied in the experiments (at the level of 10−15/day). With the rapid improvement of atomic clocks' accuracy, the geopotential determination by accurate clocks is prospective, and it is promising to realize the unification of the world vertical height system (WVHS).

Common-View Time Transfer Using Geostationary Satellite.

The National Time Service Center (NTSC), Chinese Academy of Sciences (CAS), Xi'an, China, has developed a method for common-view time transfer using Geostationary Earth Orbit (GEO) satellite (GCV) applicable to the time and frequency transfer at distant stations. This method is independent of Global Navigation Satellite System (GNSS) time and frequency transfer, as well as two-way satellite time and frequency transfer (TWSTFT). A master clock at the time laboratory transmits pseudorandom code signals to a GEO telecommunication satellite, and the time signals are retransmitted by the satellite. Receivers at the time laboratory and user locations coincidentally receive the time signals, and the offsets between the user clocks and the master clock of the time laboratory are determined with high precision if the precise coordinates of the user locations are known. For this technology, only a parabolic antenna with receiver devices and a demodulator are required at each user station, but the coordinates and precise orbits need to be obtained in advance. The key features of GCV include 1) continuous coverage of the signal from GEO communication satellites; 2) differential observations to reduce the effects of orbit error and the imprecision of the propagation delay model; 3) using a very small aperture terminal (VSAT) to enhance high signal ratio to noise to obtain precise ranging accuracy and antimultipath ability; and 4) utilizing the C-band or Ku-band to decrease the impact of the ionosphere. Experiments based on the TWSTFT network of CAS showed that the performance of GCV was at the same level as that of TWSTFT, and the rms of the residuals of GCV was less than 1.5 ns with respect to TWSTFT.

Beidou wide-area augmentation system clock error correction and performance verification

On December 27, 2018, the Beidou-3 System (BDS-3) has completed the deployment of 18 Medium Earth Orbit (MEO) satellites combined as a space constellation. In addition to the augmentation information for the new system signals B1C and B2a, the BDS-3 is compatible with the three augmentation information broadcast by the BDS-2 system for B1I and B3I signals: equivalent clock error correction, User Differential Ranging Error (UDRE) and Grid Ionosphere Vertical Error (GIVE). In this paper, the observation data of Beidou monitoring network are used to analyze the pseudo-range observation quality of the smooth transition signals B1I and B3I of BDS-2 and BDS-3. At the same time, the relationship between the equivalent clock error correction and the prediction error of the satellite clock is analyzed by using the Two-Way Satellite Time and Frequency Transfer (TWSTFT) data. The results show that the correlation between the equivalent clock error correction and the monitored clock error by using the TWSTFT data is greater than 60%. We calculate the UDRE by using the equivalent clock error correction. The results show that the satellite equivalent clock error correction can improve the accuracy of User Equivalent Range Error (UERE) by about 50%. This paper also compares the positioning accuracy of the BDS-2 satellites with the BDS-2 satellites combined BDS-3 satellites. The results show that the three-dimensional positioning accuracy is improved by about 30% after the BDS-3 satellites are added.

Performance Analysis of Two-Way Time Comparison of Eurasian Satellites Based on 1 Mcps/s Code

The bandwidth leased on Earth satellites directly affects the operation cost of TWSTFT (Two-Way Satellite Time and Frequency Transfer). Until May 2017, the Ku-band TWSTFT between Asian-European laboratories involved in UTC (Coordinated Universal Time) computing had been using the 2.5 Mcps/s pseudo-random codes with a bandwidth of 2.5 MHz. In order to reduce the cost without affecting the performance of time and frequency, a pseudo-random code with 1 Mcps/s and bandwidth of 1.7 MHz is first attempted to transmit time bidirectionally between Eurasian and Asian satellites in China. An indirect calibration for the bidirectional links by using the calibrated GPS PPP (Global Position System Precise Point Positioning) links reduces the link uncertainty. The TWSTFT link data of December 2018 are selected to analyze the link performance. It is found that the daily frequency stability and time stability of TWSTFT link constructed with 1 Mcps/s code rate reach 10−15 and 0.3 ns respectively through the ABS-2A satellite. The results show that it is feasible to use 1 Mcps/s code rate for ultra-long distance TWSTFT. Compared with the traditional methods, the system has a low cost, and the time transfer performance can meet the needs of international atomic time calculation.

Improving two-way satellite time and frequency transfer with redundant links for UTC generation

Two-way satellite time and frequency transfer (TWSTFT) is a primary technique for the generation of coordinated universal time (UTC). At present, more than 12 timing laboratories around the world use SAtellite Time and Ranging Equipment (SATRE) modems in TWSTFT operations and contribute data for the realization of UTC. The advantages of TWSTFT are its small calibration uncertainty (⩽1.0 ns if the link is calibrated with a TWSTFT mobile station) and its long-term link stability. However, the precision of SATRE TWSTFT in the operational networks is degraded by a daily variation pattern (diurnal) in the TWSTFT results. The diurnal with varying amplitude appears virtually in all SATRE TWSTFT links. The observed peak-to-peak variation of the diurnals can reach 2.0 ns in some cases. So far, studies on the sources of the diurnal have not provided conclusive understanding of the diurnal’s dominant origin.Therefore, efforts have been made to reduce the impact of the diurnal variation in TWSTFT for UTC computation. The BIPM has been using the combination of SATRE TWSTFT results and GPS carrier-phase precise point positioning solutions (GPSPPP) for UTC computation since 2010. The combination adjusts the GPSPPP results to long-term averages of TWSTFT and is effectively free from the diurnal variations because the GPSPPP results contain almost no diurnal. Lately, the use of software-defined radio receivers (SDR) in TWSTFT has shown one way of how to reduce the diurnal variations by a factor of two to three in most of the inner-continental SATRE TWSTFT links, and furthermore, how the short-term stability for all UTC SDR TWSTFT links can be improved. In addition, there has been research on the full use of the redundancy in the TWSTFT network to improve the TWSTFT link stability. Recent studies on evaluating indirect links revealed that it is possible to apply a simplified procedure to use the redundancy, in a most effective way, to reduce the diurnal variations in the Europe-to-Europe SATRE TWSTFT links by a factor of two to three. Based on these findings, we gained new insights about the diurnals and its dominant origin(s) which are discussed in this paper. The methods of the combination of SATRE TWSTFT and GPSPPP as well as the indirect SATRE TWSTFT links utilize the redundancy in the UTC time transfer network. SDR TWSTFT can largely reduce the diurnal in SATRE TWSTFT, but noticeable residual diurnal remains. In this paper, we provide the analyses of using the combination of SDR TWSTFT and GPSPPP results, as well as using the indirect SDR TWSTFT links. This paper concludes that the use of SDR TWSTFT redundant links can further improve the stabilities of UTC TWSTFT links. In addition, the use of SDR TWSTFT indirect links is a pure TWSTFT solution. The independence of the TWSTFT results to GPS results can improve the robustness of UTC computation.

Foundation and performance evaluation of real-time GNSS high-precision one-way timing system

Global navigation satellite system (GNSS) can realize global time synchronization with tens of nanoseconds precision. For more precise time synchronization applications, two-way satellite time and frequency transfer is commonly used despite its high cost and requiring a geostationary satellite. Considering the high cost, people started to use the GNSS signals to realize high accuracy time transfer, named common-view or all-in-view, which can achieve several nanoseconds according to the analyses and verifications of previous studies. However, time transfer cannot realize real-time timing in a large area as a common GNSS one-way timing receiver does. In such a timing system, a highly stable reference and a matched high-precision timing receiver system are necessary. To solve this problem, we have established a one-way timing system based on a ground-based augmentation system. The system estimates real-time high-precision satellite clocks using the ground-based augmentation network as the time reference. Moreover, the time reference is transferred to the terminal through real-time precise point positioning (PPP). Finally, the timing receiver synchronizes its local clock to the reference by real-time clock adjustment, resulting in high-precision timing. We present the details of this system, including the time reference, the PPP algorithm, and the timing receiver technologies. Finally, we give the precision and stability evaluation of the whole system, especially for one pulse per second (1 PPS) outputs of the terminal. The results show that the stability of the 1 PPS output is better than 1 ns in a day.