Time Synchronization System Research Articles

Design of IEEE1588 Power Precise Time Synchronization System

An IEEE1588 high precision network time synchronization system suitable for power system was designed based on the IEEE1588 protocol content and requirements for the PTP time synchronization of state grid. The time synchronization system supports IEEE1588 v2 protocol. The system can process event message and general message. The system supports multicast mode based on MAC and best master clock algorithm. The system also has E2E and P2P two timing patterns at the same time. At last, the author analysis the testing data. After all the work has done, we build up an experimental platform and conduct the system testing from two aspects of the time synchronization accuracy and system reliability. The experimental results show that the system time synchronization accuracy and reliability is high. The system can meet the requirements of PTP synchronization clock in power systems.

Hybrid partition- and network-level scheduling design for distributed integrated modular avionics systems

Distributed Integrated Modular Avionics (DIMA) develops from Integrated Modular Avionics (IMA) and realizes distributed integration of multiple sub-function areas. Time-triggered network provides effective support for time synchronization and information coordination in DIMA systems. However, inconsistency between processing resources and communication network destroys the time determinism benefiting from partitions and time-triggered mechanism. To ensure such time determinism and achieve guaranteed real-time performance, system design should collectively provide a global communication scheme for messages in network domain and a corresponding execution scheme for partitions in processing domain. This paper firstly establishes a general DIMA model which coordinates partitioned processing and time-triggered communication, and then proposes a hybrid scheduling algorithm using Mixed Integer Programming to produce feasible system schemes. Furthermore, incrementally integrating new functions causes upgrades or reconfigurations of DIMA systems and will generate integration cost. To control such cost, this paper further develops an optimization algorithm based on Maximum Satisfiability Problem and guarantees that the scheduling design for upgraded DIMA systems inherit their original schemes as much as possible. Finally, two typical cases, including a simple fully connected DIMA system case and an industrial DIMA system case, are constructed to illustrate our DIMA model and validate the effectiveness of our hybrid scheduling algorithms.

Compensation of Multipath Interference in a Separated Passive Time and Frequency Synchronization Systems

Multipath propagation of radio waves negatively affects to the performance of telecommunications and radio navigation systems [1, 3]. When performing time and frequency synchronization tasks of spatially separated standards, the multi­path signal propagation aggravates the probabi­lity of a correct synchronization and introduces an error. The presence of a multipath signal reduces the signal-to-noise ratio in the received signal, which in turn causes an increase in the synchronization error. The mathematical models of multipath interference suppression in the time and in the frequency domain are presented in the article. Compared to time processing, processing in the frequency domain reduces computational costs. The operation of suppression in the time domain has been verified experimentally.

Improved Time-Synchronization Algorithm Based on Direct Compensation of Disturbance Effects.

In this paper, an improved time-synchronization algorithm is proposed. The improvement of time synchronizing performance was achieved by introducing a stochastic model-based direct compensation of the disturbance effects appearing in the IEEE 1588 Precision Time Protocol (PTP)-based time synchronization system. A dynamic model of PTP clock system was obtained by reflecting the three major sources of disturbances, i.e., clock frequency drift, clock rate offset, and network noise. With the application of the dynamic model of the PTP clock system, the effects of the disturbances can be effectively eliminated in the PTP time synchronization control loop. Computer simulations are performed to verify the performance of the proposed time synchronization algorithm by applying the various types of disturbances, including network noise and clock drift. The simulation results are compared with those of other representative time synchronization algorithms, i.e., IEEE 1588 PTP algorithm and Kalman-filter-based algorithm. It is shown that the proposed algorithm improves time synchronizing performance up to 84% with respect to that of the Kalman-filter-based synchronization algorithm when simulated with colored noise type disturbances. The proposed time synchronization algorithm is expected to contribute for the realization of future Ethernet-based industry-plant monitoring and control including IEC 61850-based digital substation.

Time Synchronization in Photon-Limited Deep Space Optical Communications

Random jitter or offset between the transmitter/receiver clocks is an important parameter that has to be accurately estimated for optimal detection of pulse position modulation (PPM) symbols for high-data-rate optical communications. This parameter, in general, is modeled as an unknown random quantity that depends on the clock drift between the transmitter/receiver clocks and the random motion between the transmitter and receiver stations. In this paper, we have modeled the time jitter for two scenarios—phase modulation jitter and frequency modulation jitter. The phase modulation jitter is modeled as a Gaussian random variable which is estimated with the help of a maximum a posteriori probability (MAP) estimator. The frequency modulation jitter is characterized as a random walk, and this leads to the modeling of the jitter as a state space variable in the context of a dynamical system. Since the observations are the photon counts in each slot of a PPM symbol (for both MAP estimation and tracking), the resulting dynamical model is highly nonlinear, and particle filters are employed for tracking the frequency modulation jitter. We evaluate the performance of both the maximum a posteriori estimators and the particle filters in terms of the relative mean-square error and probability of error. We conclude that with MAP estimation and particle filters that estimate/track the time offset, we achieve a significant performance gain in terms of probability of error as compared to systems that do not have a time synchronization system in place.

Research and implementation of substation clock unsynchrony alarm system based on GPS pulse

In order to change the status quo within the substation bay control devices which only passive receiving IRIG-B GPS clock code or PPS, for the purpose of the research and the realization method of substation clock unsynchrony alarm system based on GPS pulse. On the basis of existing substation SCADA system and GPS time synchronization system, this paper realizes the real-time monitoring of time synchronization of substation bay control devices by simple modification and introduction of simple algorithm. This paper describes in detail the system construction method and relative time difference algorithm, as well as the project implementation method, to achieve the correct and punctual on-line monitoring of the bay control device, effective control of substation accidents caused by device time unsynchrony, greatly improving the stability of substation operation.

High-Performance Time Server Core for FPGA System-on-Chip

This paper presents the complete design and implementation of a low-cost, low-footprint, network time protocol server core for field programmable gate arrays. The core uses a carefully designed modular architecture, which is fully implemented in hardware using digital circuits and systems. Most remarkable novelties introduced are a hardware-optimized timekeeping algorithm implementation, and a full-hardware protocol stack and automatic network configuration. As a result, the core is able to achieve similar accuracy and performance to typical high-performance network time protocol server equipment. The core uses a standard global positioning system receiver as time reference, has a small footprint and can easily fit in a low-range field-programmable chip, greatly scaling down from previous system-on-chip time synchronization systems. Accuracy and performance results show that the core can serve hundreds of thousands of network time clients with negligible accuracy degradation, in contrast to state-of-the-art high-performance time server equipment. Therefore, this core provides a valuable time server solution for a wide range of emerging embedded and distributed network applications such as the Internet of Things and the smart grid, at a fraction of the cost and footprint of current discrete and embedded solutions.

Problems and Ways to take Objectives with the Control and Management by the Transmission of Ethnic Time and Frequency Signals in the Armed Forces of Ukraine

Within the limits of the functioning of the military segment of the single time service and reference frequencies, the problems and ways of solving the tasks of controlling and controlling the transmission of reference signals used by the Armed Forces of Ukraine are outlined. The experimental research on the determination of the accuracy characteristics of the time synchronization system (using the PTP protocol IEEE 1588v2) was implemented for its use in telecommunication networks. As a communication channel, an optical fiber network is specially built to create a synchronization system. Experimental studies confirmed the possibility of transmitting reference signals of time and frequency synchronization with the use of modern digital and fiber-optic technologies from the National Standard of Time and Frequency units to the source standard of the Armed Forces of Ukraine units of time and frequency (VEZSU) with an error that is not exceeds 1 цs And also from VESZU to consumers with an error of less than 10 microseconds at a distance of 600 km via fiber-optic communication channel L2. The creation of a corresponding complex of equipment for monitoring and control of the transmission of reference signals used by the Armed Forces of Ukraine remains relevant.

Optimization of Clock Synchronization System Architecture in Nuclear Power Plant

Clock Synchronization System (CSS) can generate standard time, time and frequency signals, and provide various high-precision time reference signals for systems and equipment requiring standard time scale in nuclear power plants. With the rapid development of power system, the requirement of time synchronization is becoming more and more urgent, which requires accurate, safe and reliable clock sources. The structure of nuclear power plant clock synchronization system is constantly optimized to meet the requirements of time synchronization of various systems and equipment, to ensure the time consistency of real-time data acquisition, to improve reliability and to adapt to the interconnection of large power grids in China. At the same time, the interconnection between time synchronization system and time-service equipment or system, and the interconnection of first-level time synchronization system network and operation mode of time synchronization devices from different manufacturers are standard

Error-related negativity predicts failure in competitive dual-player video games.

Along with improvement in electroencephalogram (EEG)-measurement technology, limitations on the situations in which data can be recorded are gradually being overcome. EEG measurement in real environments has become increasingly important as a means to monitor brain activity in our daily lives, such as while playing consumer games in the living room. The present study measured brain EEG activity while two players engaged in a competitive consumer baseball game in conditions that closely resembled daily life. The recorded brain activity was thus likely related to natural mental reactions and cognitive function that occur in similar daily life activities. To measure the EEG from participants who freely moved while playing the game, we developed EEG devices that incorporated a wireless time synchronization system using Global Positioning Satellite (GPS) signals. These devices stamped the time obtained from the GPS signals onto each data sample, which was then used to synchronize the data that were recorded by different devices. When the batter in the game swung and missed, the error-related negativity component of the event-related EEG potential was strongly evoked in frontal electrodes of the participant controlling the batter. Furthermore, the error-related negativity was modulated according to who was winning and by how much. Thus, here we have demonstrated "real-world" brain activity using a competitive consumer game, which increases intrinsic participant motivation.

Novel pilot protection for AC transmission line connected to LCC-HVDC inverter station

As known, after AC transmission line fault occurs, LCC-HVDC inverter station has three different statuses: no commutation failure, single commutation failure and continuous commutation failure. And the different statuses of inverter station could lead to wrong operation of traditional protection principles (such as current differential protection and directional pilot protection). Firstly, the paper establishes inverter station’s equivalent model under different statuses and analyzes relationship between voltage and current vectors. Secondly, the paper analyzes the adaptability of conventional protection principles including current differential protection and directional pilot protection. Thirdly, using empirical mode decomposition algorithm, novel pilot protection principle suitable for AC transmission line which is connected to inverter station is proposed. The novel protection principle is only based on power frequency current signal of two ends, and it requires no time synchronization system. Eventually, a PSCAD/EMTDC simulation model of ±800 kV LCC-HVDC and 500 kV AC transmission system is established. And the simulation results prove that the novel protection principle is immune to inverter station working status, fault resistance and fault type.

Key technology of high-precision time frequency transfer via 200 km desert urban fiber link

The precise time and frequency signal dissemination has significant applications in scientific research such as baseline interferometry, deep space network and metrology. Aside from satellite based systems, optical fiber has become an attractive alternative medium for transferring time and frequency signals, offering much improved accuracy. For the urban fiber link in the desert environment, there are many complex noise sources, such as temperature change, outdoor wind and ground vibration. Therefore, a systematical study on the noise source and on the noise reduction method in the dessert environment have practical significance. In this paper, we demonstrate a time (1 pps) and frequency signal dissemination and time synchronization system through a 200 km urban fiber in dessert environment. The noise source of the urban fiber under dessert environment is analyzed and studied in detail; the results show that the vibration and temperature shift are the major influencing factors. The vibration of urban fiber can induce the noise in the high Fourier frequency, and the temperature shift of urban fiber can induce the noise at a low Fourier frequency. An optical compensation setup is used, including the optical delay line with temperature controlled and piezoelectric ceramics driving. The phase fluctuation of frequency signal is detected and used to control the feedback of the optical compensating setup. In order to compensate for the fiber loss in a long range, a special bi-directional erbium-doped fiber amplifier is used to regenerate optical signals to achieve the long distance transmission. Then, we study the effective link noise suppression technology under different feedback compensation parameters. The systematic feedback parameters are optimized through using the different system feedback bandwidths, feedback intensities, optical power and other key parameters. The optimized systematic feedback parameters are obtained via the careful experimental observation and discussion. With the optimized systematic feedback parameters, experimental results show that the frequency stabilities are up to 8 × 10<sup>–14</sup> at 1 s and 1 × 10<sup>–16</sup> at 1000 s, and time stabilities are up to 1.2 ps in an average time of 10<sup>3</sup> s. The phase stabilized transmission of hydrogen clock signal in the 200 km level desert environment urban fiber link is realized. The verification experiment plays an important role in measuring the satellite orbit based on a connected elements’ interferometry. The relevant study result is of significance for improving the precision of time and frequency signal dissemination in the dessert environmental urban fiber.

Near Optimal Timing and Frequency Offset Estimation for 5G Integrated LEO Satellite Communication System

The integration of satellite and terrestrial 5G networks aims to provide ubiquitous coverage, improve service reliability, and enable the network scalability. However, the inherent characteristics of satellite channels bring challenges on the air interface design of integrated terrestrial-satellite networks. For example, for low earth orbits (LEO) mobile satellite communication (SatCom) system, it is unclear so far whether the 5G new radio (5G-NR) synchronization signals could meet the requirement of timing and frequency offset estimation in the presence of large Doppler shifts. In this paper, we investigate time and frequency synchronization for the downlink transmission of 5G-NR signals over LEO satellite channels. Starting from the maximum log-likelihood criterion for timing offset estimation given the observation of the received primary synchronization signals (PSS), we derive an upper bound of the objective function for simplicity. With a priori information that the maximum Doppler shift of LEO satellite-ground link is within a specific range, we construct the local synchronization sequence via using the modulated discrete prolate spheroidal sequences (DPSS) vectors. Then the timing offset estimation can be recast into a one-dimensional peak search problem. Moreover, the cyclic prefix (CP) structure of orthogonal frequency division multiplexing (OFDM) can be utilized to improve the estimation performance further. Once the timing and frequency offset are captured in the above initial synchronization phase, the tracking synchronization can be much simplified as the variation of both the timing and frequency offset is very small between two adjacent synchronization blocks. Simulation results show that by using the proposed algorithms, the 5G-NR signals can achieve near optimal downlink time and frequency synchronization in typical LEO SatCom systems.

Design of Wireless Transmission System for Shallow Seismograph Based on 433 M Module

Because of its portability, the non-cable seismograph has become the future development trend of geophysical instruments. A new wireless data transmission device of 433 M module was proposed; a wireless network was built using the EL1663B_PA module of the SI4463 core, and through the SPI interface to modify the internal parameters. Data transmission used dual antenna mode, the main station as the center of the wireless network coverage up to 550 m or more. The wireless time synchronization system was designed to realize the wireless connection communication between the shallow seismograph and the sensor of each observation point. This program aimed to eliminate the necessary connecting cable and batteries between the conventional shallow seismograph and the detector, greatly reducing the weight of the equipment, and making the shallow seismograph truly low cost, lightweight, flexible and easy to operate and so on.

Continuously analyzing finite, message-driven, time-synchronous component & connector systems during architecture evolution

Understanding the semantic differences of continuously evolving system architectures by semantic analyses facilitates engineers during evolution analysis in understanding the impact of the syntactical changes between two architecture versions. To enable effective semantic differencing usable in practice, this requires means to fully automatically check whether one version of a system admits behaviors that are not possible in another version. Previous work produced very general system models for message-driven time-synchronous (MDTS) systems that impede fully automated semantic differencing but very adequately describe such systems from a black-box viewpoint abstracting from hidden internal component behavior. This paper presents a system model for MDTS systems from a white-box viewpoint (assuming component implementation availability) and presents a sound and complete method for semantic differencing of finite MDTS system architectures. This method relies on representing (sub-)architectures as channel automata and a reduction from the semantic differencing problem for such automata to the language inclusion problem for Büchi automata. The system model perfectly captures the logical basics of MDTS systems from a white-box viewpoint and the method enables to fully automatically calculate semantic differences between two finite MDTS systems on push-button basis, yields witnesses, and ultimately facilitates semantic evolution analysis of such systems.

Design and Implementation of Time Signal Closed-loop Monitoring of Time Synchronization System in Intelligent Substation

Design and Implementation of Time Signal Closed-loop Monitoring of Time Synchronization System in Intelligent Substation

Time Synchronization Network for EAST Poloidal Field Power Supply Control System Based on IEEE 1588

This paper clearly demonstrates the architecture of time synchronization network of experimental advanced superconducting tokamak (EAST) poloidal field (PF) power supply control system and analyzes characteristics of the IEEE 1588 in detail at the same time. IEEE 1588 has unique advantages for this paper to utilize as protocol in order to improve the accuracy of the time synchronization network (TSN). Consequently, we design a time synchronization system based on PCI eXtensions for Instrumentation-6683H. This paper utilizes one master node to synchronize all slave nodes on the time network in each second. The result shows that the synchronization accuracy can be achieved within 50 ns. According to results of experiments, this system can perfectly meet the requirements of EAST PF power supply control system.

Design and implementation of pseudolites time and frequency synchronization system

Design and implementation of pseudolites time and frequency synchronization system

Low cost GNSS receivers in time synchronization systems

The GNSS (GNSS — Global Navigation Satellite Systems) receivers can be utilized to obtain accurate time markers. The preliminary results of the cheap GNSS receivers’ tests are presented in the paper. The one receiver’s price (including antenna) does not exceed 30 $. The studies on the use of receivers in the time synchronization systems were executed. Three identical models of receiver modules were used. The 1PPS (1PPS — 1 Pulse Per Second) signals available on the receiver’s output were used. The 1PPS’s main time characteristics were described. Delay times between different receivers 1PPS signals were measured. Measurements were taken using 1 GHz oscilloscope and precise time/frequency counter T3200U. Keywords: time synchronization, 1PPS, GNSS, GPS time

Analysis of Time Synchronization System

Modern technology has more and more demands on the synchronization of time and the precision of time service with the development of society and science and technology. The satellite time synchronization local time has become one of the main methods of time service at home and abroad. Beidou satellite navigation system is China's self-developed global satellite navigation system, became the third sophisticated satellite navigation system after the United States global positioning system and the Russian GLONASS satellite navigation system. This paper mainly studies the satellite timing system of the time synchronization system, which uses dual signal source of Beidou and GPS. It is not dependent on any single satellite synchronization system. Therefore, the stability of the time synchronization system is very high.