Time Synchronization Function Research Articles

Time Synchronization Method of Low-Voltage Distribution Network Based on Wi-Fi and Voltage Detection

Under the background of frequent electric fires caused by leakage and arc faults, the low-voltage distribution network uses the Internet of Things technology to solve the problem of low-voltage monitoring, so as to ensure the safe use of electricity. In order to tag the collected data with time tags, a large number of low-voltage terminal units need to have time synchronization function, while the cost and accuracy of existing time synchronization methods cannot adapt to the demand of low-voltage distribution network monitoring system. Based on analyzing the demand of low-voltage distribution network monitoring function for time synchronization, this paper puts forward a time synchronization method combining WiFi communication with voltage detection by taking advantage of the characteristics of short low-voltage line and small voltage phase angle change at both ends of the line. Time synchronization of low-voltage terminal unit at the time when the power frequency voltage crosses the zero point, using WiFi communication to transmit time synchronization commands. This method is economical and does not require additional equipment. Finally, the feasibility of the method is verified by building a test system, and the time synchronization accuracy can be within 1 ms.

Research on Clock Acquisition and Correction Technology of Measurement Equipment

Comprehensive energy metering and electricity market-oriented transactions under the dual carbon goals put forward higher requirements on the accuracy of metering equipment clocks. The existing inventory of metering equipment has complex specifications, complex communication methods, and difficult management. Because of different production years, the old version of the metering equipment has poor clock retention capability and insufficient automatic time synchronization function. In order to solve the problems of clock accuracy and time management of metering equipment, a wide-area hierarchical collection and synchronization technology of clocks is designed, a technical framework for clock collection and synchronization of equipment at all levels of the system is constructed, and the normal state of system equipment is strengthened and maintained through the method of serial broadcast time calibration. Clock, designed a time-calibration protocol for object-oriented metering equipment. This technology has been applied to the clock management of on-site metering equipment, and the qualified rate of metering equipment clocks has reached more than 95%, which has improved the automation level of metering equipment clock management, the efficiency of time schooling, and the timely rate of time schooling.

Hardware Efficient Clock Synchronization Across Wi-Fi and Ethernet-Based Network Using PTP

Precision time protocol (PTP), a state-of-the-art clock synchronization protocol primarily designed for wired networks, has recently gained attention in the wireless community, due to the increased use of the IEEE 802.11 wireless local area networks (WLAN) in real-time distributed systems. However, all the existing WLAN-based PTP designs either incorporate software timestamping (TS) delivering poor clock synchronization accuracy, or hardware (HW) TS providing better synchronization accuracy at the cost of a significant amount of HW overhead. Moreover, the performance of the existing PTP solutions is mostly evaluated in single-hop wireless networks, while the performance across wired and wireless networks is taken for granted. In this article, a new software-defined-radio-based approach to implement PTP is introduced and validated for the IEEE 802.11 WLAN. Instead of using a dedicated HW clock, the solution utilizes the timing synchronization function clock, an existing clock in the IEEE802.11 standard for synchronization between access point and WLAN stations. The performance of the proposed solution is first investigated within a single-hop WLAN and then across wired–wireless networks. Experimental results unveil that 90% of the absolute clock synchronization error falls within 1.4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu \mathrm{s}$</tex-math></inline-formula> .

Implementation of White Rabbit Time Synchronization System in State Acquisition System of High-energy Physics Experimental Device

Abstract The state acquisition system of high energy physics experimental device has very high requirements for the clock synchronization accuracy of each node. The White Rabbit (WR) distributed synchronous timing technology can realize multi node sub nanosecond clock distribution within several kilometers, and meet the requirements of clock synchronization accuracy of the system. This paper presents an implementation of WR timing system with ZYNQ 7045 as the core in the state acquisition system. This paper introduces the hardware design and implementation scheme of collector node, the implementation scheme of WR node, and the statistical data of WR-PTP time synchronization experiment results. The test results show that this method can realize the time synchronization between the nodes of the state collector, and the accuracy is better than 1 nanosecond. It can provide high-precision time synchronization function for the multi node signal acquisition system of high-energy physics experiment.

Timing Synchronization System on RF-Driven Neutral Beam Injection System

The timing synchronization system (TSS) in a radio-frequency–driven negative ion–based neutral beam injection system (NNBIS) is an important part of a negative ion–based neutral beam injection control system. In order to ensure the orderly conduct of experiments and the integrity of experimental data, the TSS needs to complete the corresponding timing synchronization function. There are two aspects to control of the NNBIS: controlling the synchronization of NNBIS subsystems within a certain precision and ensuring correct timing and amplitude output during the experiment. This paper presents the design and development of the TSS in the NNBIS, aiming at the characteristics of the IEEE 1588-2019, “IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems,” clock synchronization protocol to achieve the demands of clock synchronization at a submicrosecond level, synchronously triggering other subsystems through the network trigger and hardware trigger. The TSS successfully implemented synchronization accuracy in less than 1 μs, and the network trigger is more efficient than the hardware trigger, which is about 80 μs faster. The TSS meets the requirements of timing synchronization accuracy of the NNBIS.

WSN Data Collection and Routing Protocol with Time Synchronization in Low-cost IoT Environment

The Internet of Things (IoT) is rapidly growing as a topic of research and conversation. IoT includes monitoring applications such as environment, healthcare, and military, requiring real-time gathering and data delivery. In dealing with time-sensitive applications, time synchronization is essential to collaborative wireless sensor network (WSN) nodes’ data collection and routing information sharing. This paper proposes an ad hoc routing and data collection protocol with a time synchronization function. A hybrid packet-based time synchronization is introduced, wherein reference time is sourced from the sink node (centralized) and sourced from the adjacent nodes (distributed). The time synchronization process is integrated into the routing and data transmissions in the network as it lessens overheads and transmission exchanges, which would be beneficial for large-scale WSN. Finally, we evaluate the protocol’s performance using a realistic low-cost WSN testbed. Our proposed protocol has achieved an averaged time offset of less than 100 milliseconds for a 15-minute test duration in multiple topology scenarios.

Time Synchronization Techniques in Wireless Network : A Survey

The time synchronization procedure is very important for power saving in wireless ad hoc network and method used by the synchronization that method chooses a particular node and gives priority for transmitting a signal to that node. All the Other nodes synchronize to the selected node according to Time Synchronization Function. Here increasing research focus on designing synchronization algorithms specifically for sensor networks. This paper look for reviews of time synchronization problem and the need for synchronization in sensor networks, then presents in detail time synchronization methods explicitly designed and proposed for sensor networks and AD-HOC networks.

A novel efficient power‐saving MAC protocol for multi‐hop MANETs

SUMMARYFollowing recent advances in the performance of ad hoc networks, the limited life of batteries in mobile devices poses a bottleneck in their development. Consequently, how to minimize power consumption in the Medium Access Control (MAC) layer of ad hoc networks is an essential issue. The power‐saving mode (PSM) of IEEE 802.11 involves the Timing Synchronization Function to reduce power consumption for single‐hop mobile ad hoc networks (MANETs). However, the IEEE 802.11 PSM is known to result in unnecessary energy consumption as well as the problems of overheating and back‐off time delay. Hence, this study presents an efficient power‐saving MAC protocol, called p‐MANET, based on a Multi‐hop Time Synchronization Protocol, which involves a hibernation mechanism, a beacon inhibition mechanism, and a low‐latency next‐hop selection mechanism for general‐purpose multi‐hop MANETs. The main purposes of the p‐MANET protocol are to reduce significantly the power consumption and the transmission latency. In the hibernation mechanism, each p‐MANET node needs only to wake up during one out of every N beacon interval, where N is the number of beacon intervals in a cycle. Thus, efficient power consumption is achieved. Furthermore, a beacon inhibition mechanism is proposed to prevent the beacon storm problem that is caused by synchronization and neighbor discovery messages. Finally, the low‐latency next‐hop selection mechanism is designed to yield low transmission latency. Each p‐MANET node is aware of the active beacon intervals of its neighbors by using a hash function, such that it can easily forward packets to a neighbor in active mode or with the least remaining time to wake up. As a consequence, upper‐layer routing protocols can cooperate with p‐MANET to select the next‐hop neighbor with the best forwarding delay. To verify the proposed design and demonstrate the favorable performance of the proposed p‐MANET, we present the theoretical analysis related to p‐MANET and also perform experimental simulations. The numerical results show that p‐MANET reduces power consumption and routing latency and performs well in extending lifetime with a small neighbor discovery time. Copyright © 2011 John Wiley &amp; Sons, Ltd.

On Fast and Accurate Detection of Unauthorized Wireless Access Points Using Clock Skews

We explore the use of clock skew of a wireless local area network access point (AP) as its fingerprint to detect unauthorized APs quickly and accurately. The main goal behind using clock skews is to overcome one of the major limitations of existing solutions - the inability to effectively detect Medium Access Control (MAC) address spoofing. We calculate the clock skew of an AP from the IEEE 802.11 Time Synchronization Function (TSF) time stamps sent out in the beacon/probe response frames. We use two different methods for this purpose - one based on linear programming and the other based on least-square fit. We supplement these methods with a heuristic for differentiating original packets from those sent by the fake APs. We collect TSF time stamp data from several APs in three different residential settings. Using our measurement data as well as data obtained from a large conference setting, we find that clock skews remain consistent over time for the same AP but vary significantly across APs. Furthermore, we improve the resolution of received time stamp of the frames and show that with this enhancement, our methodology can find clock skews very quickly, using 50-100 packets in most of the cases. We also discuss and quantify the impact of various external factors including temperature variation, virtualization, clock source selection, and NTP synchronization on clock skews. Our results indicate that the use of clock skews appears to be an efficient and robust method for detecting fake APs in wireless local area networks.

Exclusive backoff scheme (EBS) for ad hoc mode in IEEE 802.11 wireless LANs

We propose a new backoff scheme, called exclusive backoff scheme (EBS), for ad hoc mode in IEEE 802.11 wireless LANs. Each station generates a unique backoff number before starting backoff procedure by using timing synchronization function (TSF) timer and a unique user's ID (UID), which makes a collision free access. The EBS shows better performance in the view of channel utilization and packet delay than original IEEE 802.11 CSMA/CA backoff scheme.

A Mutual Network Synchronization Method for Wireless Ad Hoc and Sensor Networks

Mutual network synchronization is a distributed method in which geographically separated clocks align their times to one another without the need of reference or master clocks. Mutual network synchronization is attractive for wireless ad hoc and sensor networks, because there is no overhead associated with the discovery, management, and tracking of specific nodes with reference clocks. Existing mutual network synchronization methods, however, make use of physical and medium access control layers that are proprietary and not widely available. This paper presents clock sampling mutual network synchronization (CS-MNS). CS-MNS is able to achieve microsecond networkwide synchronization accuracy for single-hop or multiple-hop network topologies in mobile or static wireless ad hoc and sensor networks. Different from existing mutual network synchronization approaches, the timing information is exchanged explicitly by using periodic time stamp packets. These packets can be, for instance, the same beacons used in the IEEE 802.11 or IEEE 802.15.4 standards, which, to the best of our knowledge, makes CS-MNS the first mutual network synchronization method compatible to these popular standards. A CS-MNS node adjusts the time and frequency of its clock recursively in the time domain by multiplying the time of its clock by a factor that is updated with any newly received time stamp. Sufficient stability conditions are derived via the discrete Lyapunov direct method. Additionally, CS-MNS enables several beacon medium access approaches, which are discussed and analyzed. Thorough numerical results are presented, which demonstrate at least one and two orders of magnitude improvement in scalability and accuracy, respectively, relative to the IEEE 802.11 timing synchronization function (TSF). CS-MNS also shows better accuracy than the multihop ad hoc TSF (MATSF) and the automatic self-time-correcting procedure (ASP) methods under similar scenarios. The latter is achieved with less complexity and with fully compatible IEEE 802.11 beacons.

Toward secure and scalable time synchronization in ad hoc networks

Time synchronization is crucial in ad hoc networks. Due to the infrastructure-less and dynamic nature, time synchronization in such environments is vulnerable to various attacks. Moreover, time synchronization protocols such as IEEE 802.11 TSF (Timing Synchronization Function) often suffer from scalability problem. In this paper, we address the security and the scalability problems of time synchronization protocols in ad hoc networks. We propose a novel suite of time synchronization mechanisms for ad hoc networks based on symmetric cryptography. For single-hop ad hoc networks, we propose SSTSP, a scalable and secure time synchronization procedure based on one-way Hash chain, a lightweight mechanism to ensure the authenticity and the integrity of synchronization beacons. The “clock drift check” is proposed to counter replay/delay attacks. We then extend our efforts to the multi-hop case. We propose MSTSP, a secure and scalable time synchronization mechanism based on SSTSP for multi-hop ad hoc networks. In MSTSP, the multi-hop network is automatically divided into single-hop clusters. The secure intra-cluster synchronization is achieved by SSTSP and the secure inter-cluster synchronization is achieved by exchanging synchronization beacons among cluster reference nodes via bridge nodes. The proposed synchronization mechanisms are fully distributed without a global synchronization leader. We further perform analytical studies and simulations on the proposed approaches. The results show that SSTSP can synchronize single-hop networks with the maximum synchronization error under 20 μs and MSTSP 55–85 μs for multi-hop networks, which are, to the best of our knowledge, among the best results of currently proposed solutions for single-hop and multi-hop ad hoc networks. Meanwhile, our approaches can maintain the network synchronized even in hostile environments.

AN EVOLVABLE OPERATING SYSTEM FOR WIRELESS SENSOR NETWORKS

With low-power consumption, small code and data size, evolvability as design criteria, we develop an evolvable operating system (EOS) for wireless sensor network applications. The EOS provides memory space efficient thread management, collaborative thread communication model and network stack. It also supports power management of microcontroller and radio transceiver, and network wide time synchronization function. Above all, the most important feature is the concept of evolvability with which the operating system itself can be easily configurable and upgradeable.

A modified power saving mode in IEEE 802.11 distributed coordinator function

Power saving (PS) mode specified in IEEE 802.11 standard is a power efficient method that prolongs the network operation time of battery powered wireless LAN devices. It is a synchronous protocol which requires precise time synchronization among all the participating nodes within the Independent Basic Service Set (IBSS). Therefore, Time Synchronization Function (TSF) is defined for the protocol to operate without the aid of external timing sources. Time synchronization is achieved by periodically transmitting the time synchronization beacon, which will define a series of fixed length beacon intervals. In PS mode for Distributed Coordinated Function (DCF), nodes will wake up at the beginning of each beacon interval for a duration called Announcement Traffic Indication Message (ATIM) window to announce their pending data packets using small ATIM control packets. After the ATIM window, nodes will transmit the announced data packets using contention-based DCF access procedure. This paper proposes a modified mechanism by sending the TSF beacon at the end of each ATIM window and adding certain scheduling information in the beacon to schedule the transmission of announced data packets. The scheduling information will ensure the data packets transmission to be contention-free. Hence, the scheduled data packet transmission will achieve a higher throughput and lower energy consumption. Results based on simulation have shown that as much as 70% of energy saving can be achieved.

Performance modeling of IEEE 802.11 wireless LANs with stochastic Petri nets

In 1997, IEEE standardized the physical layers and the medium access for wireless local area networks. This paper presents a performance study of the distributed coordination function, the fundamental contention-based access mechanism. Most performance studies adopt unchecked simplifying assumptions or do not reveal all details of the simulation model. We develop a stochastic Petri net model, which captures all relevant system aspects in a concise way. Simulation allows to quantify the influence of many mandatory features of the standard on performance, especially the backoff procedure, extended interframe spaces, and the timing synchronization function. We identify conditions when simplifying assumptions commonly used in analytical modeling are justified. Applying these conditions, we derive a more compact and analytically tractable model from the detailed model.