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Abstract This paper introduces an enhanced time synchronization method different from IEEE 1588 (PTP). The proposed algorithm employs a unique synchronous message packet structure with a fixed length of 10 bytes and the highest system priority. This design enables preemptive transmission, effectively reducing transmission and queuing delays. Additionally, it applies a Kalman filtering model to mitigate noise interference, including clock drift, network delay jitter, and network asymmetry. The algorithm also features a clock drift compensation mechanism to continuously adjust the clock, ensuring high precision and stability in time synchronization. The algorithm proposed in this paper has the characteristics of being easy to implement, requiring minimal hardware resources, and being applicable to a variety of networks. Simulation results show that, with an 80 MHz crystal oscillator, the time offset between master and slave clocks does not exceed ± 1 clock cycle in symmetric communication links. In asymmetric links, the maximum time offset is within ± 3 clock cycles. Compared to the original PTP algorithm and the Kalman filter-based time synchronization algorithm, this method reduces the time offset from several microseconds to less than 40 ns.

IEEE 1588, also known as the Precision Time Protocol (PTP), is a standard protocol for clock synchronization in distributed systems. While it is not architecture-specific, implementing IEEE 1588 on Reduced Instruction Set Computer-V (RISC-V) low-power embedded devices demands considering the system requirements and available resources. This paper explores various approaches and techniques to achieve accurate time synchronization in such instruments. The analysis covers software and hardware implementations, discussing each method's challenges, benefits, and trade-offs. By examining the state-of-the-art in this field, this paper provides valuable insights and guidance for researchers and engineers working on time-critical applications in RISC-V-based embedded systems, aiding in selecting the most-suitable stack for their designs. [ABSTRACT FROM AUTHOR]

Time-Sensitive Networking (TSN) requires clock synchronization superior to the well-known Network Time Protocol (NTP). The IEEE 802.1AS-2020 used for synchronization in TSN networks is based on the IEEE 1588-2019 standard (also known as Precision Time Protocol, PTP) defines methods and tools to perform sub-microsecond time synchronization over vari- ous communication channels. However, the IEEE 1588 implementation is commonly used with wired communication protocols, although there are use cases that could gain an advantage from a wireless solution. This paper investigates the possibility of PTP clock synchronization through wireless Ultra Wideband (UWB) communication. UWB excels where other wireless technologies are lacking: it provides high accuracy timestamping even if multipath propagation is present. The method is evaluated using commercial, well-accessible cheap hardware, resulting in the order of 10-nanosecond accuracy. The paper also highlights the main error components and requirements for improving wireless PTP synchronization. [ABSTRACT FROM AUTHOR]

With the vigorous development of industrial automation and the Internet of things, the transmission of data is more dependent on immediacy, so network devices have higher and higher requirements for time synchronization accuracy. The clock source of common network devices is provided by the transistor oscillator in the server, but the oscillator will change with factors such as aging and temperature, and it cannot be guaranteed that the oscillator in the server will work at the same frequency. Time synchronization can be achieved by technologies such as IRIG-B, NTP, or IEEE 1588 (PTP), but the hardware cost of building IRIG-B is high, and NTP has the lowest cost, but it can only provide time accuracy from milliseconds to microseconds. PTP can provide sub-microsecond or even nanosecond time precision. It is a system of time synchronization mechanisms through Ethernet transmission. In this article, we first propose a time synchronization system using the development board and PDP protocol. On the Xilinx Zynq-7000 SOC platform of Petalinux, we implement the hardware solution of Linux PTP. The hardware time stamp is 20 ns. To improve the accuracy, the congenital frequency error between the oscillators must be considered. Therefore, a PTP auxiliary time stamp with dynamic frequency compensation is proposed and designed into a chip. Experimental results show that at 45 nm (TN40G) it can operate at 370 MHz and achieve 2.7 ns resolution, which can be applied to more demands. [ABSTRACT FROM AUTHOR]

Abstract The IEEE 1588 precision time protocol (PTP) is very important for many industrial sectors and applications that require time synchronization accuracy between computers down to microsecond and even nanosecond levels. Nevertheless, PTP and its underlying network infrastructure are vulnerable to cyber-attacks, which can stealthily reduce the time synchronization accuracy to unacceptable and even damage-causing levels for individual clocks or an entire network, leading to financial loss or even physical destruction. Existing security protocol extensions only partially address this problem. This paper provides a comprehensive analysis of strategies for advanced persistent threats to PTP infrastructure, possible attacker locations, and the impact on clock and network synchronization in the presence of security protocol extensions, infrastructure redundancy, and protocol redundancy. It distinguishes between attack strategies and attacker types as described in RFC7384, but further distinguishes between the spoofing and time source attack, the simple internal attack, and the advanced internal attack. Some experiments were conducted to demonstrate the impact of PTP attacks. Our analysis shows that a sophisticated attacker has a range of methodologies to compromise a PTP network. Moreover, all PTP infrastructure components can host an attacker, making the comprehensive protection of a PTP network against a malware infiltration, as for example exercised by Stuxnet, a very tedious task.

• Indian test facility (INTF) to characterize DNB for ITER delivery. • INTF to operate for long pulse duration of upto 3600 s with event driven DAQ and IEEE1588 time synchronization. • The work presents a solution of acquiring high bandwidth signals along with conventional PXIe based acquisition system. • Benchmarking and assessment of ITER relevant IEEE 1588 time synchronization protocol. The Indian Test Facility (INTF) is a negative Hydrogen ion based 100 kV, 60A, 5 Hz modulated NBI system having duty cycle of 3 s ON time to 20 s OFF time. Prime objective of the facility is to characterize ITER Diagnostic Neutral Beam (DNB) with full specifications, prior to shipment and installation in ITER. In order to fully characterize ITER DNB, a matured Data Acquisition and Control system (DACS) is needed which will be responsible for supervisory control of the facility and for acquiring and monitoring signals at run time. Apart from conventional DACS, high speed data acquisition is needed for diagnostics and other signals with sampling rate requirements of 100 MS/s. For acquiring data from such systems it is imperative that the data be acquired only for certain duration on the occurrence of the event. Such acquisition systems are classified as event driven data acquisition system and are widely used in fusion engineering community. Development and implementation of high speed event driven data acquisition systems pose challenges in terms of data buffering, data streaming and synchronization. The precise timing of the event occurrence with respect to the main pulse should also be known for which a timing and synchronization system is needed. To fulfill this purpose, IEEE 1588 protocol offers a network based method of synchronizing multiple nodes based on Ethernet with sub microsecond accuracy. The present work describes the development of an event driven high speed data acquisition in synchronization with IEEE 1588 based timing network. The work proposes the time stamping of the event from synchronized network integrated with the event acquisition platform. The developed system has been tested for pulse durations longer than 3600 s. The performance of event data acquisition system has been thoroughly characterized and improved by applying various software optimizations in LabVIEW. The present work although intended to be used for INTF can be used for any such facility in fusion or other areas. The paper provides results of IEEE 1588 based timing network in various configurations and event data acquisition system developed on high speed FPGA controlled digitizer board with prototype results. [ABSTRACT FROM AUTHOR]

The Precision Time Protocol (PTP) as described in IEEE 1588–2019 provides a sophisticated mechanism to achieve microsecond or even sub-microsecond synchronization of computer clocks in a well-designed and managed network, therefore meeting the needs of even the most time-sensitive industrial and financial applications. However, PTP is prone to many security threats that impact on a correct clock synchronization, leading to potentially devastating consequences. Here, the most vicious attacks are internal attacks, where a threat actor has full access to the infrastructure including any cryptographic keys used. This paper builds on existing research on the impact of internal attack strategies on PTP networks. It shows limitations of existing security approaches to tackle internal attacks and proposes a new security approach using a trusted supervisor node (TSN), in line with prong D as specified in IEEE 1588–2019. A TSN collects and analyzes delay and offset outputs of monitored slaves, as well as timestamps embedded in PTP synchronization messages, allowing it to detect abnormal patterns that point to an attack. The paper distinguishes between two types of TSN with different capabilities and proposes two different detection algorithms. Experiments show the ability of the proposed method to detect all internal PTP attacks, while outlining its limitations. [ABSTRACT FROM AUTHOR]

This work explores clock synchronization algorithms used to process timestamps from the IEEE 1588 precision time protocol (PTP). It focuses on the PTP-unaware network scenario, where the network nodes do not actively contribute to PTP's operation. This scenario typically imposes a harsh environment for accurate clock distribution, primarily due to the packet delay variation experienced by PTP packets. In this context, it is essential to process the noisy PTP measurements using algorithms and strategies that consider the underlying clock and packet delay models. This work surveys some attractive algorithms and introduces an open-source analysis library that combines several of them for better performance. It also provides an unprecedented comparison of the algorithms based on datasets acquired from a sophisticated testbed composed of field-programmable gate arrays (FPGAs). The investigation provides insights regarding the synchronization performance under various scenarios of background traffic and oscillator stability.

Network visibility and monitoring are critical in modern networks due to the increased density, additional complexity, higher bandwidth, and lower latency requirements. Precise packet timestamping and synchronization are essential to temporally correlate captured information in different datacenter locations. This is key for visibility, event ordering and latency measurements in segments as telecom, power grids and electronic trading in finance, where order execution and reduced latency are critical for successful business outcomes. This contribution presents Precise Network Time Monitoring (PNTM), a novel mechanism for asynchronous Ethernet packet timestamping which adapts a Digital Dual Mixer Time Difference (DDMTD) implemented in an FPGA. Picosecond-precision packet timestamping is outlined for 1 Gigabit Ethernet. Furthermore, this approach is combined with the White Rabbit (WR) synchronization protocol, used as reference for the IEEE 1588–2019 High Accuracy Profile to provide unprecedented packet capturing correlation accuracy in distributed network scenarios thanks to its sub-nanosecond time transfer. The paper presents different application examples, describes the method of implementation, integration of WR with PNTM and subsequently describes experiments to demonstrate that PNTM is a suitable picosecond-level distributed packet timestamping solution.

In distributed network applications such as the Internet of Things (IoT), a master clock is used to provide a frame of reference among all constituent nodes. Any drift in the clock on a single node can cause serious cascading effects in a system that largely involves ordered events and time-critical tasks. To provide a stable reference clock, time synchronisation protocols are utilised in distributed systems where client nodes can synchronise their clock with a master node. IEEE 1588 Precision Time Protocol (PTP) is increasingly being used to provide high time synchronisation accuracy in comparison with other synchronisation protocols. In this paper, we have proposed a hardware design and FPGA-based implementation of the IEEE 1588 protocol to be used in wired LAN communication. Experimental results show synchronisation accuracy in the range of few nanoseconds, which is significantly better than the existing implementations. The FPGA implementation was carried out on a Xilinx Artix-7 evaluation board. [ABSTRACT FROM AUTHOR]

A network-based control system includes many connected devices, and time synchronization plays an important role in the unified operation of those systems. A clock servo needs a guarantee time offset and a clock rate to minimize the time difference between devices. This paper proposes an adaptive clock servo to improve time synchronization. This proposed algorithm uses a fuzzy-based proportional-integral clock servo (fuzzy-PI) based on IEEE 1588 to reduce the frequency of clock compensation. This method adapts the bandwidth and enhances noise reduction, improving both the time offset and rate difference between the slave and master. The node time can synchronize with the master time after just one cycle of synchronization. Experiments validated the effectiveness of the algorithm and demonstrated that the slave can track the master with the mean and standard deviation of the time offset are 0.432ns and 4.402ns. A cycle time of one second is used to ensure a low-bandwidth network. With these results, the number of nodes over a real-time network can be increased.

Time synchronization is a critical feature for many scientific facilities and industrial infrastructures. The required performance is progressively increasing everyday, for instance, few tens of nanoseconds for Fifth Generation (5G) networks or sub-nanosecond accuracy on next family of particle accelerators and astrophysics telescopes. Due to this exigent accuracy, many applications require specific timing dedicated networks, increasing the system cost and complexity. Under this context, the new IEEE 1588-2019 High Accuracy (HA) default profile is intensively based on White Rabbit (WR) which can provide sub-nanosecond accurate synchronization for Ethernet networks. However, current WR solutions have not been designed to work properly with high data bandwidth delivery services even in 1 Gigabit Ethernet (GbE) links. On this contribution, the authors propose a new architecture design that enables WR and, consequently, the IEEE 1588-2019 HA profile to be deployed over 10 GbE links solving the already identified data bandwidth problem. Furthermore, this work addresses different experiments needed to characterize the system performance in terms of time synchronization and data transfer. As final result, this contribution presents for the first time in the literature a new WR system which allows high bandwidth data exchange in 10 GbE networks while providing sub-nanosecond accuracy synchronization. The proposed solution maintains the time synchronization performance of existing WR 1 GbE devices with significant advantages in terms of latency and data bandwidth, enabling its deployment in applications that integrate data and synchronization information in the same network.

Highly accurate synchronization has become a major requirement because of the rise of distributed applications, regulatory requests and position, navigation and timing backup needs. This fact has led to the development of new technologies which fulfill the new requirements in terms of accuracy and dependability. Nevertheless, some of these novel proposals have lacked determinism, robustness, interoperability, deployability, scalability or management tools preventing them to be extensively used in real industrial scenarios. Different segments require accurate timing information over a large number of nodes. Due to the high availability and low price of global satellite-based time references, many critical distributed facilities depend on them. However, the vulnerability to jamming or spoofing represents a well-known threat and back-up systems need to be deployed to mitigate it. The recently approved draft standard IEEE 1588-2019 includes the High Accuracy Default Precision Time Protocol Profile which is intensively based on the White Rabbit protocol. White Rabbit is an extension of current IEEE 1588-2008 network synchronization protocol for sub-nanosecond synchronization. This approach has been validated and intensively used during the last years. This paper revises the pre-standard protocol to expose the challenges that the High Accuracy profile will find after its release and covers existing applications, promising deployments and the technological roadmap, providing hints and an overview of features to be studied. The authors review different issues that have prevented the industrial adoption of White Rabbit in the past and introduce the latest developments that will facilitate the next IEEE 1588 High Accuracy extensive adoption.

This article presents the Zynq-embedded node for the Cherenkov telescope array (ZEN-CTA) node, a programmable system-on-chip (SoC) with White Rabbit (WR)-synchronization capability. It targets a solution for the uniform clock and trigger time-stamping module of the small-sized telescopes in the CTA. This module is tasked as a distributed acquisition device with a focus on obtaining time stamps for candidate Cherenkov events, which could be generated at potentially high rates from very-high-energy gamma rays and their subsequent distribution over Ethernet. In this context, the customized design of the ZEN-CTA node is examined thoroughly, including its generic implementation aspects and its main functional blocks. The design of the WR-assisted time-to-digital converters (TDCs) for time-stamping analog triggers is presented in detail alongside the implementation of an upgraded high-speed data path (1 Gb/s) for the WR-compatible Ethernet interfaces of the node. The new data path will feature a direct memory access engine for direct software transmissions and a hardware description language (HDL) coprocessor for high-speed forwarding. Next, the time-stamping accuracy of the WR-enhanced TDCs will be characterized alongside the forwarding efficiency of the new data path. Finally, conclusions are drawn, and the main contributions of this research are enumerated, a potential deployment within the CTA infrastructure to support the acquisition of Cherenkov light is considered, and additional use cases are mentioned. [ABSTRACT FROM AUTHOR]

Emerging power system protection and control applications require faster-responding measurements and more accurate knowledge of the actual latency of the measurement and communications systems. A new method for accurately determining the reporting latency of a phasor measurement unit (PMU) has been developed and demonstrated. This method operates in real-time, works passively for any existing PMU without requiring changes to the PMU hardware or software, and it is very accurate-providing a measurement uncertainty of

The IEEE 1588 precision time protocol (PTP) is very important for many industrial sectors and applications that require time synchronization accuracy between computers down to microsecond and even nanosecond levels. Nevertheless, PTP and its underlying network infrastructure are vulnerable to cyber-attacks, which can stealthily reduce the time synchronization accuracy to unacceptable and even damage-causing levels for individual clocks or an entire network, leading to financial loss or even physical destruction. Existing security protocol extensions only partially address this problem. This paper provides a comprehensive analysis of strategies for advanced persistent threats to PTP infrastructure, possible attacker locations, and the impact on clock and network synchronization in the presence of security protocol extensions, infrastructure redundancy, and protocol redundancy. It distinguishes between attack strategies and attacker types as described in RFC7384, but further distinguishes between the spoofing and time source attack, the simple internal attack, and the advanced internal attack. Some experiments were conducted to demonstrate the impact of PTP attacks. Our analysis shows that a sophisticated attacker has a range of methodologies to compromise a PTP network. Moreover, all PTP infrastructure components can host an attacker, making the comprehensive protection of a PTP network against a malware infiltration, as for example exercised by Stuxnet, a very tedious task. [ABSTRACT FROM AUTHOR]

The Precision Time Protocol (PTP) as described in IEEE 1588–2019 provides a sophisticated mechanism to achieve microsecond or even sub-microsecond synchronization of computer clocks in a well-designed and managed network, therefore meeting the needs of even the most time-sensitive industrial and financial applications. However, PTP is prone to many security threats that impact on a correct clock synchronization, leading to potentially devastating consequences. Here, the most vicious attacks are internal attacks, where a threat actor has full access to the infrastructure including any cryptographic keys used. This paper builds on existing research on the impact of internal attack strategies on PTP networks. It shows limitations of existing security approaches to tackle internal attacks and proposes a new security approach using a trusted supervisor node (TSN), in line with prong D as specified in IEEE 1588–2019. A TSN collects and analyzes delay and offset outputs of monitored slaves, as well as timestamps embedded in PTP synchronization messages, allowing it to detect abnormal patterns that point to an attack. The paper distinguishes between two types of TSN with different capabilities and proposes two different detection algorithms. Experiments show the ability of the proposed method to detect all internal PTP attacks, while outlining its limitations.

Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. Time-synchronization technology can provide a common notion of time among the participating nodes on a network. This is essential not only for protocol operation for time-critical services but also for the time stamp for information included in the message. Precise time information can be very crucial for such things as autonomous driving because there are various sensor measurements from multiple cameras, and radio detection and ranging (radar) and light detection and ranging (LiDAR) are used for perceiving the current situation via sensor fusion. A well-known synchronization method, IEEE 1588, denoted as the precision time protocol (PTP), can be used for various applications. For in-vehicle networks of autonomous cars, we have to consider that the network may be comprised of subnetworks based on different protocols such as controller area network (CAN) and Ethernet. However, implementing PTPs on such heterogeneous vehicle networks causes several problems. First, the PTP procedure must be modified to be implement on a CAN network. Second, to calculate the delay and offset for PTP, the processing delay that occurs during message conversion must be considered. In this paper, we propose a synchronization method for CAN–Ethernet networks to solve these problems. The performance of the proposed synchronization method is evaluated by experiments on a real CAN–Ethernet network. [ABSTRACT FROM AUTHOR]

The time-sensitive network paradigm envisions the integration of operation technology and information technology in the same network. One of the requirements for building time-sensitive networks is sharing a global time along the network. This requirement is especially critical in wireless systems, where there are few robust methods to perform accurate time transfer. In this article, the problem of time transfer over realistic wireless channels is studied, and a time distribution scheme is proposed. The time distribution scheme has three components: Precision time protocol, a novel timestamping method (enhanced timestamps) and an algorithm to implement the enhanced timestamps. The performance of the proposed scheme has been evaluated in MATLAB using the IEEE 802.11n Standard under several standard wireless local area network channel models. The results show that the system can reach subnanosecond time transfer accuracy under non-line-of-sight and time-variant conditions, but its performance greatly depends on the signal-to-noise ratio and on the channel variation rate. [ABSTRACT FROM AUTHOR]

As the SMPTE S T 2059 standards for accurate synchronization and time labeling gain traction, it is important for users and system integrators alike to understand how time transfer, using the IEEE 1588 Precision Time Protocol (PTP), could be affected by unintentional malfunctioning or misconfigured devices as well as by malicious attacks. Given the missioncritical nature of broadcast infrastructure, secured time distribution is rapidly becoming a mandatory requirement. Although S T 2059-2 defines a PTP profile, it does not address how to secure all parts that define the timing system. The IEEE 1588 standard provides a certain level of fault tolerance by autonomously activating an auxiliary reference in the case of loss of the primary time source. Yet, PTP time transfer is not sufficiently well protected to either withstand deliberate attacks or cope with misconfigured or malfunctioning devices. Consequently, both scenarios must be investigated in detail. This entails a thorough analysis of all the relevant attacks on Global Navigation Satellite System (GNSS) receivers to misaligned message rates or corrupted messages, to name but a few. This article addresses ways to secure different components of the timing system, ranging from the Master clock(s) across the IP network and finally to the media nodes generating or receiving S T 2110 flows. Beyond securing the timing system, special care should be taken to immediately identify potentially harmful degradations and/or failures using multiple approaches that provide efficient means to correlate events. This is covered by a series of recommendations and best practices to ensure operational stability. [ABSTRACT FROM AUTHOR]

With the advent of a new Precision Time Protocol specification, new opportunities abound for clock synchronization possibilities within power grid control systems. The third iteration of the Institute of Electrical and Electronics Engineers Standard 1588 specification provides several new features specifically aimed at complex, wide-area deployments in which situational awareness and control require precise time agreement. This paper describes the challenges faced by existing technology, introduces the new time distribution specification, and provides examples to explain how it represents a game-changing innovation.

As the SMPTE S T 2059-2 standard for accurate time transfer enters real-world All-IP Studio deployments, it is important for broadcasters and system integrators to understand how the various parameters and options of the IEEE 1588 Precision Time Protocol (PTP) profile will impact both system performance and the network architecture for all media essence based on standardized IP transports, such as the recently adopted SMPTE S T 2110 series or AES67. Given the mission-critical nature of broadcast infrastructure, fully redundant networks are becoming a mandatory requirement. While S T 2022-7 defines a media essence redundancy model for switching between multiple identical flows on a per Realtime Transport Protocol (RTP) packet basis, such as it would apply to the SMPTE 2110 suite of standards, the IEEE 1588's assumption of constant transmission delays would be violated by this approach, thus resulting in transient errors. The IEEE 1588 Precision Time Protocol (PTP) time transfer paradigm was not designed to be switched on a per PTP message basis. Although PTP has a certain level of redundancy built into the protocol to tolerate the loss of the time reference, it cannot utilize the advantages of redundant networks to their full extent. This paper addresses how the stability and availability of time and frequency transfer for SMPTE S T 2059-2 endpoints can be improved far beyond the basic redundancy mechanism provided by PTP if they are connected via separate paths toward the network as proposed in the SMPTE S T 2022-7 standard. For maximum utilization of multiple parallel channels for time transfer, PTP implementation requires additional enhancements. The solutions presented are complemented by comparative measurements demonstrating the improvements generated by such optimized designs, which includes the presence of common transient and permanent error conditions, thus showing the advantages of fully redundant time transfer over basic redundancy mechanisms provided by PTP. [ABSTRACT FROM AUTHOR]

Modern distributed control systems comprise multiple intelligent devices capable of performing complex time and mission-critical tasks both independently of each other or partly jointly with each other. To do so, they strongly depend on an accurate common notion of time as well as a reliable shared communication medium for timely data exchange. Traditional legacy communication technologies (field bus systems) supported time transport to a certain extent or provided at least a common frequency. Due to its numerous undisputed advantages, Ethernet has become the only viable communication medium effectively replacing such systems. Being inherently asynchronous time and frequency transfer has to be accomplished using a packet-based approach when moving to Ethernet. After explaining the basic principles of packet-based time transfer, the most common standards are explained compared with each other with respect to their intended application domains. Special emphasis will be put on the Precision Time Protocol (PTP) as defined in the underlying IEEE 1588 standard and its variant IEEE 802.1AS used for time-sensitive networks. Maintaining a highly accurate common notion of time under all circumstances is a crucial prerequisite for most distributed systems. Although PTP has proven to provide sub-microsecond accuracies, it can cope only with a limited number of error conditions. This paper describes all major sources that can either deteriorate the accuracy or cause a total loss of synchronization altogether. Selected countermeasures and enhancements are presented, which can greatly improve the resilience of PTP against errors as well as malicious attacks. This paper concludes by presenting the selected measurements’ results of a novel proposed method. [ABSTRACT FROM AUTHOR]

Highlights • Real time assessment of IEEE 1588 with multi-protocol traffic interactions. • Combined GNSS and IEEE 1588 systems offer a more reliable timing performance. • Manufactures have vendor-specific interpretations of IEEE 1588 messages. • IEEE 1588 satisfies the ±1 μs accuracy requirement in transmission substations. • Use capture card and impairment simulator to identify performance boundary. Abstract Accurate timestamping with 1 µs precision is required by power system monitoring and control equipment, including: Phase Measurement Units (PMUs) for real-time measurement and control; travelling wave detectors for fault location, protection and control; and sample value measurement techniques associated with the IEC 61850 process bus. The conventional way of achieving this is to transmit 1-PPS or IRIG-B timing signals using dedicated cables but such an approach is expensive and difficult to update as secondary control systems evolve. IEEE 1588 precision time protocol (PTP) allows the transmission of time information with sub-microsecond accuracy in an Ethernet network. However, a comprehensive study is required to enhance the confidence of the power industry in using PTP in present and future IEC 61850 based substations. This paper delivers a design and experimental validation of the real-time time synchronisation characteristics achievable with IEEE 1588. Several factors which can potentially affect the synchronisation accuracy in delivering a time reference from the master clocks to the end devices during both steady-state and transient changes were investigated. The objective is to increase the understanding of the real-time performance of a complete IEEE 1588 timing system applied in transmission substations, and identify the limitations of commercially-available devices. [ABSTRACT FROM AUTHOR]

The Indian test facility (INTF) is a negative hydrogen ion-based 100-kV, 60-A, 5-Hz modulated NBI system having 3-s ON/20-s OFF duty cycle. Prime objective of the facility is to characterize ITER diagnostic neutral beam (DNB) with full specifications, prior to shipment and installation in ITER. The automated and safe operation of the system will require a reliable and rugged instrumentation and control system which provide control, data acquisition (DAQ), safety, and interlock functions, referred as INTF-DACS. The INTF-DACS has been designed based on the ITER CODAC architecture and ITER- plant control design handbook (PCDH) guidelines with the aim of developing the technical understanding of CODAC framework to be utilized for development of plant system instrumentation and control for DNB. Presently, the development work has been initiated for both the control system and DAQ system of INTF DACS. The INTF DAQ system has to perform functions related to acquiring, monitoring, timing synchronization, and archiving of the signals. It also has to interface with the control system of INTF to ensure proper operations. The DAQ system is designed for acquiring over 700 signals for 14 plant systems. The development of this whole system is done in NI LabVIEW using NI real-time PXIe. The PXIe platform with RTOS performs acquisition of signals at sampling rate of up to 10 KS/s. One of the main challenges is to develop the DAQ system to support multichannel triggered-based acquisition and monitoring for pulse durations up to 3600 s. The host layer is a distributed processing system consisting of two hosts and database system. To ensure timing synchronization, a dedicated timing network is included based on IEEE 1588 protocol with help of PXI timing cards. This helps in providing a timing reference to other future systems. For archiving data, MySQL-based data server is integrated for storing data for each experimental shot continuously which can be utilized later for query based data retrieval. In this paper, the development strategy and test results are discussed in order to develop the DAQ system for INTF including the development of interfaces with other components of DACS and experiences obtained, which can be utilized to develop similar DAQ systems of large scale. The novel methods developed for monitoring signals and file size reduction are also discussed. [ABSTRACT FROM AUTHOR]

Time-synchronization technology can provide a common notion of time among the participating nodes on a network. This is essential not only for protocol operation for time-critical services but also for the time stamp for information included in the message. Precise time information can be very crucial for such things as autonomous driving because there are various sensor measurements from multiple cameras, and radio detection and ranging (radar) and light detection and ranging (LiDAR) are used for perceiving the current situation via sensor fusion. A well-known synchronization method, IEEE 1588, denoted as the precision time protocol (PTP), can be used for various applications. For in-vehicle networks of autonomous cars, we have to consider that the network may be comprised of subnetworks based on different protocols such as controller area network (CAN) and Ethernet. However, implementing PTPs on such heterogeneous vehicle networks causes several problems. First, the PTP procedure must be modified to be implement on a CAN network. Second, to calculate the delay and offset for PTP, the processing delay that occurs during message conversion must be considered. In this paper, we propose a synchronization method for CAN–Ethernet networks to solve these problems. The performance of the proposed synchronization method is evaluated by experiments on a real CAN–Ethernet network.

This paper is concerned with the clock synchronization problem for IEEE 1588 networks. First, the synchronization error is described as a bounded disturbance, and a linear extended state observer (LESO) is designed to estimate the lumped disturbance induced by the oscillator frequency drift and timestamps quantization errors. Then, the lumped disturbance is compensated by the proposed controller. The proposed approach has the advantage that it's able to deal with non-Gaussian disturbance induced by accumulated quantization errors. Simulations are provided to validate the effectiveness and superiority of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper investigates the ultimate limits of White Rabbit (WR), an high-accuracy time distribution system based on field-programmable gate array (FPGA). The knowledge of such limits is essential for new emerging applications that are evaluating WR. In this paper, we identify and study the key elements in the WR synchronization: the digital dual mixer time difference phase detector and the Gigabit Ethernet transceiver. The benchmarks and experimental analysis of these key elements allow us to determine the WR switch (WRS) performance limits and evaluate their evolution with newer FPGAs. The identified performance limits are achievable by the present-day generation of WRS. The ultimate limits of short-term synchronization performance due to FPGA implementation have been derived through analysis and then demonstrated using the existing WRS enhanced with an additional daughterboard. This combination (WRS and daughterboard) achieves a tenfold improvement in terms of phase noise, jitter, and short-term stability with respect to the current WR performance. Both phase detectors and Gigabit transceivers have a similar phase noise contribution equal to a short-term stability of modified Allan deviation 4E−13 at $\tau = 1$ s (dominated by flicker phase modulation noise). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

IEC 61850, which drives to digitalize information in the entire system, is being increasingly adopted in the power utility industry, since the last decade. It is necessary for all devices communicating with distributed digital data to have a common understanding of time. As protection and control devices are directly related to the safety of the power system, they are strictly required to have time accuracies. This paper describes the design of a hybrid slave clock with the transparent clock (TC) functionality defined in the IEEE 1588 precision time protocol. The design objective includes not only the synchronization of the time accuracy but also the transient time, as specified in the IEC/IEEE 61850-9-3 precision time profile for power utility automation. To comply with these objectives, we adopt a hardware–software co-design approach. The timestamp of each port is implemented by hardware. Also, they are connected by hardware to calculate the bridge time on the fly, enabling the design to have a one-step TC functionality with low latency. On the other hand, the synchronizing controller is implemented by software for adapting to the varying external conditions. The controller uses the linear quadratic Gaussian (LQG) to achieve stable steady-state performance. Simultaneously, the least-squares estimator is utilized to estimate the initial conditions of the LQG controller for reducing the transition time. Experimental results show the three-sigma time inaccuracies are 15.6 ns for the TC and 149 ns for the slave with an average transition time of 13.5 s, satisfying the IEEE/IEC 61850-9-3 criteria. [ABSTRACT FROM AUTHOR]

The IEEE 1588 precision time protocol (PTP) is a time synchronization protocol with sub-microsecond precision primarily designed for wired networks. In this letter, we propose wireless precision time protocol (WPTP) as an extension to PTP for multi-hop wireless networks. WPTP significantly reduces the convergence time and the number of packets required for synchronization without compromising on the synchronization accuracy. [ABSTRACT FROM PUBLISHER]

Accurate and precise clock synchronization is one of the fundamental requirements for various applications, such as telecommunication systems, measurement and control systems, and smart grid systems. Precision time protocol (PTP) was designed and specified in IEEE 1588 to meet that requirement. PTP provides a mechanism for synchronizing the clocks in a PTP system to a high degree of accuracy and precision based on exchange synchronization messages through a master-slave hierarchy. The best master clock (BMC) algorithm is currently used to establish the master-slave hierarchy for PTP. However, the BMC algorithm does not provide a fast recovery mechanism in case of master failures. The accuracy and precision of the PTP clocks could be deteriorated by the occurrence of failure in the network (link or node failure). These fault occurrences will affect network performance and reliability, and cause clock time drifting of the PTP nodes. In this paper, we present a novel approach, called timing fault recovery (TFR), to significantly reduce clock time drifting in PTP systems. TFR detects the fault occurrence in the network and recovers it by using a handshake mechanism with a short duration. Therefore, the TFR approach provides clock stability and constancy and increases the reliability and the availability of PTP systems. The performance of TFR has been analyzed and compared to that of the standard PTP. Various simulations were conducted to validate the performance analysis. The results show that, for our sample network, the TFR approach reduces clock drifting by 90% in comparison to the standard PTP, thus providing better clock firmness and synchronization accuracy for PTP clocks. [ABSTRACT FROM AUTHOR]

Accurate timing is often required for the intelligent electronic devices (IEDs) used in transmission substations. A common method of achieving this is direct connection of a device to a local global positioning system (GPS) receiver and the use of its one-pulse-per-second synchronizing signal and the IRIG-B coded message. However, concerns about GPS reliability are encouraging the use of timing systems less dependent on the direct use of local GPS receivers. The IEEE 1588 protocol is a network-based time synchronization technique designed to coexist with IEC 61850 applications and deliver sub microsecond timing accuracy. Many utilities are now considering the adoption of IEEE 1588, but they need confidence in the reliability of this technology before it can be rolled out to real substations. Hence, comprehensive tests were undertaken on an IEEE 1588 timing system, to help gain insight into the limitations of the system. This paper presents a procedure to assess the performance of a timing system based on distributed GPS receivers and one based on a mixture of GPS receivers and IEEE 1588 devices. Test results indicate whichever system is selected, high quality devices and systems, with appropriate installation and engineering, are essential to satisfy the stringent \pm 1\, \mu \texts accuracy requirements needed by critical IED applications. [ABSTRACT FROM AUTHOR]

The working principle and the architecture of a calibration system for devices operating with the IEC 61850-9-2 standard are described. Two different types of devices are considered: stand-alone merging units (SAMUs) used to retrofit conventional transformers in power network substations and commercial test sets suited for nonconventional voltage and current sensor calibration in the field. An SAMU is essentially an analog-to-digital converter delivering its results in the IEC 61850-9-2 format. The functionalities of the test set evaluated here are the analog signal generation (voltage and current) and their synchronous IEC 61850-9-2 representation. This paper presents a calibration setup that has been applied to both types of devices. [ABSTRACT FROM AUTHOR]

The lack of provisioning of synchronized timing support from known timing standards in IEEE 802.11 wireless networks has been overcome in IEEE 802.11-2012 through the timing advertisement (TA) mechanism. The scheme, however, presents a synchronization architecture of a cascade of four clocks. It provides no information on how the external time will be synchronized with the built-in clock of the access point (AP) and when the timestamping is performed on the wireless link, which can lead to a loss in synchronization accuracy. To this end, this work analyzes the quantitative performance of the TA mechanism with a non-IEEE802.11 mechanism, SyncTSF, which also uses the same four clocks as in the TA mechanism and compares their performance with the help of simulations. Both schemes offer similar accuracy and precision if the offset corrections involved in both schemes are carried out properly. Nevertheless, SyncTSF is more flexible, as it can be easily implemented using commercial off-the-shelf hardware using only software support. For the implementation of TA mechanism, additional guidelines from the IEEE 802.11 Standard along with dedicated hardware support is required. [ABSTRACT FROM PUBLISHER]