Showing papers on "Precision Time Protocol published in 2020"
TL;DR: 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: 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.
34 citations
TL;DR: The pre-standard protocol is revised 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.
Abstract: 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.
33 citations
TL;DR: A phasor measurement unit (PMU) integrating the white rabbit (WR) protocol and its experimental validation with a focus on the synchrophasor phase estimation in steady state conditions is presented, by using a PMU calibrator generating the reference signals.
Abstract: Within the context of time dissemination techniques for power systems applications, this paper discusses the use of the white rabbit (WR) protocol for synchrophasor networks. Specifically, this paper presents a phasor measurement unit (PMU) integrating the WR technology and its experimental validation with a focus on the synchrophasor phase estimation in steady state conditions, by using a PMU calibrator generating the reference signals. We further compare the accuracy of the developed PMU with other state-of-the-art time synchronization technologies for PMUs, i.e., global positioning system (GPS) and precision time protocol (PTP), demonstrating applicability of WR for PMU sensing networks.
25 citations
TL;DR: This article proposes to close the PTP loop through an extension that introduces new functionality and messages and demonstrates that the approach preserves PTP functionality, while successfully detecting cyber attacks against PTP components in a timely manner.
Abstract: The precision time protocol (PTP) is considered as one of the most favorable mechanisms for providing unified and precise time at the substation level in the smart grid. Nevertheless, PTP was shown to be vulnerable to cyber-attacks targeting its components and synchronization services. In this article, we capitalize on the theory and outcome of our previous work to contribute a more complete solution that addresses PTP cyber security. We propose to close the PTP loop through an extension that introduces new functionality and messages. This extension covers the PTP attack surface and enables the detection of attacks on PTP time synchronization. We formally model and verify the proposed extension using UPPAAL model checker. In addition, we validate the proposed extension using Omnet++ simulation. The evaluation demonstrates that our approach preserves PTP functionality, while successfully detecting cyber attacks against PTP components in a timely manner.
24 citations
TL;DR: A detailed threat analysis of the Precision Time Protocol standard is presented, in which the security properties that should be addressed by any security extension are highlighted and an efficient elliptic-curve Public-Key signatures are suggested.
Abstract: The Precision Time Protocol (PTP) aims to provide highly accurate and synchronized clocks. Its defining standard, IEEE 1588, has a security section (“Annex K”) which relies on symmetric-key cryptography. In this paper we present a detailed threat analysis of the PTP standard, in which we highlight the security properties that should be addressed by any security extension. During this analysis we identify a sequence of new attacks and suggest non-cryptographic network-based defenses that mitigate them. We then suggest to replace Annex K's symmetric cryptography by an efficient elliptic-curve Public-Key signatures. We implemented all our attacks to demonstrate their effectiveness, and also implemented and evaluated both the network and cryptographic defenses. Our results show that the proposed schemes are extremely practical, and much more secure than previous suggestions.
22 citations
TL;DR: This paper constructs an experimental PTP test bed and performs the baseline measurements of synchronization between multiple clocks, and demonstrates successful attacks that disrupt PTP synchronization, including vulnerabilities based on the lack of message authentication between master and slave clocks.
Abstract: The IEEE 1588 standard known as Precision Time Protocol (PTP) was developed to provide highly accurate and synchronized clocks for a wide range of applications. In particular, it is critical for latency-sensitive applications, such as enterprise-class financial transactions. In this paper, we analyze some of the security risks associated with this protocol, in particular, cyberattacks that disrupt the synchronization between multiple PTP devices or the synchronization between system clock and PTP hardware. We construct an experimental PTP test bed and perform the baseline measurements of synchronization between multiple clocks. We then demonstrate successful attacks that disrupt PTP synchronization, including vulnerabilities based on the lack of message authentication between master and slave clocks. Proposed mitigations of these vulnerabilities are discussed, in an effort to improve the next-generation implementations of this timing protocol or recommend additional external authentication devices in the network architecture.
17 citations
TL;DR: This study has compared the well-known synchronization techniques and concluded that the PTP is the most appropriate answer to robust clock synchronization though challenges are there that requires thoughtful efforts and modification in the current version.
Abstract: Precise time synchronization becomes a vital constituent due to the rigorous needs of several time-sensitive applications. The clock synchronization protocol is one of the fundamental factors that can define the quality of communication. Our study starts with a brief discussion on the application domain of precise time synchronization and comes with an in-depth study of the synchronization with the main focus on the IEEE 1588 Precision Time Protocol (PTP). We have compared the well-known synchronization techniques and conclude that the PTP is the most appropriate answer to robust clock synchronization though challenges are there that requires thoughtful efforts and modification in the current version. The working mechanism and main components of the PTP network are discussed. We have established a testbench using commercially available devices and development boards to evaluate the PTP performance under different configurations. Major sources of synchronization error and other aspects contributing to precision are examined. This paper discussed numerous approaches that could enhance the performance of the PTP protocol. Structures for PTP based wireless clock synchronization required by advanced applications has also been discussed. In the end, paper focuses on the main industrial application areas in which PTP plays an important role, including WLAN, optical data centers, Smart grid, IEC 61850, etc. We conclude the paper by identifying the future trends and research directions for PTP based clock synchronization.
16 citations
08 Jun 2020
TL;DR: An extension of the precision time protocol to improve clock synchronization in hybrid networks including both wireless and wire-bound segments and presents a simulation framework for the proposed protocol to evaluate it with TSN-based systems that support the TSN features.
Abstract: This paper proposes an extension of the precision time protocol (IEEE 802.1AS) to improve clock synchronization in hybrid networks including both wireless and wire-bound segments. This extension targets systems based on Time Sensitive Networking (TSN) such as industrial applications and vehicular systems. By considering the deterministic delays and the clock drift, the precision of the clock synchronization of the standard 802.1AS scheme can be significantly improved. Furthermore, in order to support dynamic communication environments with mobile nodes, the problem of asymmetric delays in the transmission of the timing packets of the synchronization protocol is also considered. Therefore, a Path Deviation Delay (PDD) filter is introduced to monitor the traffic behavior of timing packets as well as to exclude outlier values which can occur as a result of dynamic and asymmetric scenarios. The paper presents a simulation framework for the proposed protocol to evaluate it with TSN-based systems that support the TSN features (e.g. IEEE 802.1Qci and IEEE 802.1Qbv sub-standards). The simulation results show that the proposed protocol improves the synchronization precision compared with the standard 802.1AS protocol. It shows that the proposed protocol enhances the synchronization precision to less than 1 microsecond. In contrast, the synchronization error increases significantly with the standard protocol in the presence of different asymmetric ratios and in mobile node scenarios.
10 citations
19 Mar 2020
TL;DR: The IEEE 1588 Precision Time Protocol is a widely used mechanism to provide time synchronization of computer clocks down to microsecond accuracy as required by many financial and industrial applications, however, PTP is vulnerable to infrastructure cyber-attacks that reduce the desired accuracy.
Abstract: The IEEE 1588 Precision Time Protocol (PTP) is a widely used mechanism to provide time synchronization of computer clocks down to microsecond accuracy as required by many financial and industrial applications ("IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems," 2008). However, PTP is vulnerable to infrastructure cyber-attacks that reduce the desired accuracy. IEEE 1588 defined an experimental security extension (Annex K) in order to protect a PTP network, but various drawbacks have been discovered, resulting in further improvements including the use of public-key encryption ( Itkin & Wool, 2020 ) and reduce the three-way handshake mechanism to one way authentication ( Onal & Kirrmann, 2012 ). Today Annex K is deprecated in favor of L2 / L3 security mechanisms. Further on, in 2020 a backwards compatible IEEE 1588 version (v2.1) will be introduced, that contains a new security extension called Annex S. Annex S consists of four prongs as follows ("IEEE Draft Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems," 2019): • Prong (A) PTP Integrated Security Mechanism describes an authentication type-length-value (TLV) that is aligned with and integrated into the PTP message. • Prong (B) PTP External Transport Security Mechanisms describes the current external security mechanisms that can be used to provide protection to PTP message i.e., IPsec and MACsec. • Prong (C) Architecture Guidance describes a redundant time system, redundant grandmaster, and redundant paths. • Prong D (Monitoring and Management Guidance) suggests monitoring the slaves’ synchronization process.
10 citations
TL;DR: This paper proposes a synchronization method for CAN–Ethernet networks to solve the problems of implementing precision time protocol (PTP) on heterogeneous vehicle networks, and the performance of the proposed synchronization method is evaluated by experiments on a real CAN– Ethernet network.
Abstract: 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.
10 citations
25 Jun 2020
TL;DR: The results indicate that the MSM may represent a workable monitoring solution for MV and LV distribution networks, with an acceptable trade-off between cost and performance.
Abstract: This paper develops a novel approach for distribution system monitoring and state estimation, where time synchronisation of smart-meter measurements is carried out via the Precision Time Protocol (PTP). The approach is based on the concept of a Modified Smart Meter (MSM), a distribution system monitoring instrument that enables accurate time synchronisation of smart meter data. The design, application, communication technique and protocols of the MSM are described in detail. The proposed MSM device features PTP-based time synchronisation of smart meter measurements, and the concept of unbundling is applied to collect measurements utilising the existing smart meter sensors. This is expected to reduce the overall implementation cost of an MSM-based distribution network monitoring system compared to a system based on Phasor Measurement Units (PMUs). The problem of requiring open sky access for GPS links can potentially be solved by means of PTP synchronisation. Three-phase state estimation simulations using the IEEE-13 and 123 bus unbalanced test networks are employed to demonstrate the applicability of the MSM, and its performance is compared to standard PMU devices. The results indicate that the MSM may represent a workable monitoring solution for MV and LV distribution networks, with an acceptable trade-off between cost and performance.
TL;DR: This paper investigates the impact of the most important APT strategies on a PTP network, i.e., the delay attack, packet modification or transparent clock attack, and time reference attack, using a fully programable and customizable man in the middle device, thereby considering the two most popular PTP slave daemons PTPd and PTP4l.
Abstract: The IEEE 1588 precision time protocol (PTP) is used by many time-sensitive applications and systems, as it achieves sub-microsecond time synchronization between computer clocks. However, a PTP network is vulnerable to cyber-attacks that can reduce the protocol accuracy to unacceptable levels for some or all clocks in a network with potentially devastating consequences. Of particular concern are advanced persistent threats (APT), where an actor infiltrates a network and operates stealthily and over extended periods of time before being discovered. This paper investigates the impact of the most important APT strategies on a PTP network, i.e., the delay attack, packet modification or transparent clock attack, and time reference attack, using a fully programable and customizable man in the middle device, thereby considering the two most popular PTP slave daemons PTPd and PTP4l. In doing so, it determines suitable attack patterns and parameters to compromise the time synchronization covertly.
12 Oct 2020
TL;DR: It is argued and shown that the latency introduced by using NTP as a source reference is adequate for human behavior research, and the subsequent cost and modularity benefits are a desirable trade-off for applications in this domain.
Abstract: Existing data acquisition literature for human behavior research provides wired solutions, mainly for controlled laboratory setups. In uncontrolled free-standing conversation settings, where participants are free to walk around, these solutions are unsuitable. While wireless solutions are employed in the broadcasting industry, they can be prohibitively expensive. In this work, we propose a modular and cost-effective wireless approach for synchronized multisensor data acquisition of social human behavior. Our core idea involves a cost-accuracy trade-off by using Network Time Protocol (NTP) as a source reference for all sensors. While commonly used as a reference in ubiquitous computing, NTP is widely considered to be insufficiently accurate as a reference for video applications, where Precision Time Protocol (PTP) or Global Positioning System (GPS) based references are preferred. We argue and show, however, that the latency introduced by using NTP as a source reference is adequate for human behavior research, and the subsequent cost and modularity benefits are a desirable trade-off for applications in this domain. We also describe one instantiation of the approach deployed in a real-world experiment to demonstrate the practicality of our setup in-the-wild.
TL;DR: It is confirmed that the fifty (50) clock model-based collaborative correction maintains 10−6 second PTP accuracy for 10 min prolonged period after the master failure when tested with clock offset variations less than 50 ppm.
Abstract: This paper proposes a distributed nodes-based clock synchronization method to sustain sub-microsecond precision synchronization of slave clocks upon master clock failure in IEEE 1588 PTP (precision time protocol) system. The sustaining is achieved by synchronizing the slave clocks to the estimated reference clock which is obtained from the analysis of distributed slave clocks. The proposed method consists of two clock correction functions (i.e., a self-correction and a collaborative correction, respectively). Upon master failure, the self-correction estimates a clock correction value based on the clock model which is constructed during normal PTP operation. The collaborative correction is performed in the preselected management node. The management node estimates a reference clock by collecting and analyzing clock information gathered from the other slave clocks. The performance of the proposed method is simulated by computer to show its usefulness. It is confirmed that the fifty (50) clock model-based collaborative correction maintains 10−6 second PTP accuracy for 10 min prolonged period after the master failure when tested with clock offset variations less than 50 ppm.
15 Jun 2020
TL;DR: In this article, the authors proposed a hybrid approach to synchronize large-scale networks, drawing on Kalman filtering along with time-stamps generated by the Precision Time Protocol (PTP) for pairwise node synchronization.
Abstract: In this work, we propose a hybrid approach to synchronize large scale networks. In particular, we draw on Kalman Filtering (KF) along with time-stamps generated by the Precision Time Protocol (PTP) for pairwise node synchronization. Furthermore, we investigate the merit of Factor Graphs (FGs) along with Belief Propagation (BP) algorithm in achieving high precision end-to-end network synchronization. Finally, we present the idea of dividing the large-scale network into local synchronization domains, for each of which a suitable synchronization algorithm is utilized. The simulation results indicate that, despite the simplifications in the hybrid approach, the error in the offset estimation remains below 5 ns.
TL;DR: In this article, the authors proposed a modular and cost-effective wireless approach for synchronized multisensor data acquisition of social human behavior, which involves a cost-accuracy trade-off by using Network Time Protocol (NTP) as a source reference for all sensors.
Abstract: Existing data acquisition literature for human behavior research provides wired solutions, mainly for controlled laboratory setups. In uncontrolled free-standing conversation settings, where participants are free to walk around, these solutions are unsuitable. While wireless solutions are employed in the broadcasting industry, they can be prohibitively expensive. In this work, we propose a modular and cost-effective wireless approach for synchronized multisensor data acquisition of social human behavior. Our core idea involves a cost-accuracy trade-off by using Network Time Protocol (NTP) as a source reference for all sensors. While commonly used as a reference in ubiquitous computing, NTP is widely considered to be insufficiently accurate as a reference for video applications, where Precision Time Protocol (PTP) or Global Positioning System (GPS) based references are preferred. We argue and show, however, that the latency introduced by using NTP as a source reference is adequate for human behavior research, and the subsequent cost and modularity benefits are a desirable trade-off for applications in this domain. We also describe one instantiation of the approach deployed in a real-world experiment to demonstrate the practicality of our setup in-the-wild.
11 Jun 2020
TL;DR: A programmable Man-in-the-Middle (pMitM) and a programmable injector (pInj) device that allow the implementation of a variety of attacks, enabling security researchers to quantify the impact of APTs on time synchronisation.
Abstract: The Precision Time Protocol is essential for many time-sensitive and time-aware applications. However, it was never designed for security, and despite various approaches to harden this protocol against manipulation, it is still prone to cyber-attacks. Here Advanced Persistent Threats (APT) are of particular concern, as they may stealthily and over extended periods of time manipulate computer clocks that rely on the accurate functioning of this protocol. Simulating such attacks is difficult, as it requires firmware manipulation of network and PTP infrastructure components. Therefore, this paper proposes and demonstrates a programmable Man-in-the-Middle (pMitM) and a programmable injector (pInj) device that allow the implementation of a variety of attacks, enabling security researchers to quantify the impact of APTs on time synchronisation.
12 Jun 2020
TL;DR: The basic architecture of the time synchronization system for the seafloor observatory network is introduced and deployment suggestions are proved to be rational and effective according to the performance of the asymmetric delay of the PTP clock port in simulation and evaluation.
Abstract: The special environment and tasks of the seafloor observatory network require sub-microsecond accuracy for time synchronization. It’s the mainstream technology to build a time synchronization system based on Precision Time Protocol (PTP) in the near future. However, for the multi-node, long-distance, ring topology seafloor observatory network, the deployment strategy of the time synchronization system has not been fully studied. In this work, the basic architecture of the time synchronization system for the seafloor observatory network is introduced. PTP clock models are constructed using the OMNeT++ simulation software, based on which the modeling of the time synchronization systems of linear and annular structures are realized. After simulation and analysis, deployment suggestions including synchronization interval setting and clock mode selection of the annular time synchronization system are proposed. The suggestions are proved to be rational and effective according to the performance of the asymmetric delay of the PTP clock port in simulation and evaluation.
01 Sep 2020
TL;DR: Experimental results related to a test PTP architecture are presented, in order to assess its feasibility and investigate the performance of Precision Time Protocol.
Abstract: Accurate and stable time synchronization is crucial for the reliable operation of monitoring, protection and control systems in smart grids. As an alternative to GPS-based time synchronization of Phasor Measurement Units over a wide area network, this paper investigates the performance of Precision Time Protocol (PTP). After introducing time synchronization requirements in power systems and exploring the main vulnerabilities, experimental results related to a test PTP architecture are presented, in order to assess its feasibility.
01 Sep 2020
TL;DR: This work proposes a scheme that rewinds time in time-synchronization software such that the system clock is delayed from the actual time by a certain number of years, and confirmed that it enabled a 32-bit Linux system to operate correctly based on its delayed system clock while it was synchronizing with a Network Time Protocol server and a Precision Time Protocol master.
Abstract: Embedded systems with 32-bit Linux can encounter the year 2038 problem, which is caused by an overflow of the system clock. To prevent this overflow, we propose a scheme that rewinds time in time-synchronization software such that the system clock is delayed from the actual time by a certain number of years. Our method rewinds time received by time-synchronization software immediately after it becomes available as a UTC-based timestamp. We confirmed that our method enabled a 32-bit Linux system to operate correctly based on its delayed system clock while it was synchronizing with a Network Time Protocol server and a Precision Time Protocol master. This was achieved with only 3 lines of modification for ntpd and 2 lines for linuxptp. By adopting our scheme and modifying applications to exchange correct time values with external nodes, a system can avoid the year 2038 problem. This approach saves development costs as it requires no modification to the operating system.
28 Sep 2020
TL;DR: This paper proposes a novel PMU synchronized by a wireless IEEE 1588 Precision Time Protocol (WPTP) which enables precise synchronization of clocks via packet networks.
Abstract: An important application in the Smart Grid area is the large-scale application of measuring systems in Distribution Networks (DNs) with the Micro Phasor Measurement Unit ($\mu$PMU). The majority of traditional $\mu$PMUs and Phasor Measurement Units (PMUs) use GPS as time synchronization signals. However, this time synchronization system limits the installation of $\mu$PMUs only to outdoor applications and they will remain expensive. In this context, IEEE 1588 comes as an effective way to enhance performance in time synchronization, it can allow microsecond accuracy and is designed for wired and wireless networks. Moreover, the wireless Precision Time Protocol (PTP) reduces the convergence time and the number of packets required for synchronization without compromising on the synchronization accuracy. On the other hand, using the embedded systems the Micro Phasor Measurement Unit ($\mu$PMU) becomes possible since the volume of PMU will be small and easy to be installed. This paper proposes a novel PMU synchronized by a wireless IEEE 1588 Precision Time Protocol (WPTP) which enables precise synchronization of clocks via packet networks.
15 Jun 2020
TL;DR: This paper will focus on how two of these attacks, the asymmetric delay and the byzantine attack, can be implemented in a PTP network, and analyses their impact on slave clocks, and investigates how these attacks can be detected.
Abstract: The IEEE 1588 Precision Time Protocol (PTP) is very important for many financial and industrial applications, as it can provide highly accurate time synchronisation down to microsecond level. However, any PTP infrastructure is vulnerable to cyber-attacks that can de-synchronise some or all network devices, causing potentially destructive consequences. This paper will focus on how two of these attacks, the asymmetric delay and the byzantine attack, can be implemented in a PTP network, analyses their impact on slave clocks, and investigates how these attacks can be detected.
TL;DR: An implementation architecture for distributed RF transmission timing alignment based on synchronized triggering among radio units and centralized processing units is proposed and results validate the functionality of the proposed architecture and illustrate various relevant choices concerning system parameters.
Abstract: This work investigates a mechanism for alignment of the timing on which spatially distributed and cooperative radio units transmit in radio-frequency (RF) when served over a packet-based fronthaul. It analyzes the problem by considering the imperfect clock synchronization of the radio units and the packet delay variation that fronthaul packets are subject to. Following the analysis, this paper proposes an implementation architecture for distributed RF transmission timing alignment based on synchronized triggering among radio units and centralized processing units. Throughout this discussion, special attention is given to the scheme’s impact on the overall achievable fronthaul latency. Subsequently, this work discusses both hardware and software aspects of a prototype that was developed based on field-programmable gate arrays (FPGAs). In the end, it presents results obtained on an Ethernet fronthaul testbed where the referred FPGA-based prototypes implement radio units that are synchronized using the IEEE 1588 precision time protocol or by pulse-per-second references. Results validate the functionality of the proposed architecture and illustrate various relevant choices concerning system parameters.
27 Jul 2020
TL;DR: Results show that the filter is more effective than the PI controller on STM32F429 and the cut-off frequency can lower the time difference within 10 ns per second in the stable synchronous state.
Abstract: Network time synchronization technology is now applied in various fields. IEEE 1588 is one of a high accuracy synchronization standard and Precision Time Protocol daemon (PTPd) is a software that satisfied with IEEE 1588. This paper is going to realize PTPd on STM32F429 and analyze how it works. Then a synchronization model of PTPd is established to find the influence of PTPd parameters and the way to improve the synchronization precision. To verify the synchronization model, several simulations and experiments are carried out. The results show that the filter is more effective than the PI controller. Additionally, filters with positive feedback may lead divergence on this embedded system. Removing the positive feedback and lower the cut-off frequency can lower the time difference within 10 ns per second in the stable synchronous state.
Posted Content•
TL;DR: This work draws on Kalman Filtering (KF) along with time-stamps generated by the Precision Time Protocol (PTP) for pairwise node synchronization, and investigates the merit of Factor Graphs along with Belief Propagation algorithm in achieving high precision end-to-end network synchronization.
Abstract: In this work, we propose a hybrid approach to synchronize large scale networks. In particular, we draw on Kalman Filtering (KF) along with time-stamps generated by the Precision Time Protocol (PTP) for pairwise node synchronization. Furthermore, we investigate the merit of Factor Graphs (FGs) along with Belief Propagation (BP) algorithm in achieving high precision end-to-end network synchronization. Finally, we present the idea of dividing the large-scale network into local synchronization domains, for each of which a suitable sync algorithm is utilized. The simulation results indicate that, despite the simplifications in the hybrid approach, the error in the offset estimation remains below 5 ns.
01 Jul 2020
TL;DR: This work uses White Rabbit device which is an implementation of Precision Time Protocol intended for the synchronization with sub-nanosecond precision to implement the implementation of time transfer both in S-band and C-band.
Abstract: We perform the results implemented via time and data transfer using single-mode optical fiber. We use White Rabbit device which is an implementation of Precision Time Protocol (PTP) intended for the synchronization with sub-nanosecond precision. Our work briefs with the implementation of time transfer both in S-band and C-band. The work more focus on every timing system needs a primary time source which serves as a reference for all the nodes. In most sources the reference clock must fulfill rigorous requirements for the long-term stability. In this work atomic clock has been chosen as primary clock source.
30 Jun 2020
TL;DR: Control system TimePictra and SyncView Plus synchronization equipment considered, which allow measurements in packet networks, and the possibility of creating a monitoring system - synchronization signals stability (but today with certain limitations).
Abstract: Control system TimePictra and SyncView Plus synchronization equipment considered, which allow measurements in packet networks. In the latest versions of these control systems, it became possible to measure the stability parameters of outgoing and incoming synchronization signals on network synchronization equipment by means that are hardware implemented in this equipment and supported by the corresponding software in TimePictra and SyncView Plus control systems. TimePictra and SyncView Plus control systems make it possible to perform such internal measurements in packet networks. For example, PDV (Packet Delay Variation), packet MTIE (Maximum Time Interval Error), packet TDEV (Time Deviation), packet minTDEV measurements. That is, the measurement ideology that Microsemi proposed in its TimeAnalyzer 7500 measuring device has seamlessly switched to the synchronization network itself. Based on the considered control systems, the possibility of creating a monitoring system - synchronization signals stability (but today with certain limitations). The principles of creating a modern system for monitoring the synchronization network based on signal analysis using the NTP(Network Time Protocol) and PTP (Precision Time Protocol) protocols are proposed. A monitoring scheme for the quality of reference synchronization signals using the PTP and NTP protocols presented, which includes two local sources. One based on the GPS receiver (Global Positioning System). Second based on the local PTP1 server. PTP1 connected to the calibration circuit and the outgoing signal connected to the averaging scheme. It is also conditionally possible to replace the PTP server with NTP. The scheme considered universal for two protocols. A prototype of the interaction between the three NTP nodes and the central server described. This prototype makes it possible to demonstrate the principles of monitoring by majority rules. In case of accumulation of a sufficient amount of data, you can create a graph or fill in data arrays for further analysis.
Patent•
09 Jan 2020TL;DR: In this paper, the authors describe a method to determine an ingress time from a field in the PTP message overwritten with a value corresponding to the ingress times, and an adjustment for a timing parameter based at least in part on the inggress time.
Abstract: Methods, systems, and devices for wireless communications are described. In an example ingress point of a wireless communication network, a method includes receiving a first ethernet frame comprising a precision time protocol (PTP) message at a first node and determining an ingress time for the PTP message, generating a packet data unit (PDU) for transmission to a second node of the wireless communication network based at least in part on the first ethernet frame by overwriting a field in the PTP message with a value corresponding to the ingress time, and sending the PDU to the second node. An egress point method may include receiving a PDU comprising a PTP message, determining an ingress time from a field in the PTP message overwritten with a value corresponding to the ingress time, and determining an adjustment for a timing parameter based at least in part on the ingress time.
TL;DR: In this study, the local controller of an AC/DC converter is introduced with designs applied to each system to satisfy the requirement and improve its reliability and availability.
Patent•
31 Jan 2020
TL;DR: In this article, a time synchronization method in a precision time protocol network and a computer program therefor which solve the problem of an unbalanced master-slave structure that can cause imbalance problems such as high communication loads and high bandwidth consumption at multiple boundary clocks and enable a fast recovery mechanism in the event of a master clock failure.
Abstract: An embodiment of the present invention relates to a time synchronization method in a precision time protocol network and a computer program therefor which solve the problem of an unbalanced master-slave structure that can cause imbalance problems such as high communication loads and high bandwidth consumption at multiple boundary clocks and enable a fast recovery mechanism in the event of a master clock failure.