Time Synchronization In Networks Research Articles

A Low-Computational Burden Closed-Form Approximated Expression for MSE Applicable for PTP with gfGn Environment

The Precision Time Protocol (PTP) plays a pivotal role in achieving precise frequency and time synchronization in computer networks. However, network delays and jitter in real systems introduce uncertainties that can compromise synchronization accuracy. Three clock skew estimators designed for the PTP scenario were obtained in our earlier work, complemented by closed-form approximations for the Mean Squared Error (MSE) under the generalized fractional Gaussian noise (gfGn) model, incorporating the Hurst exponent parameter (H) and the a parameter. These expressions offer crucial insights for network designers, aiding in the strategic selection and implementation of clock skew estimators. However, substantial computational resources are required to fit each expression to the gfGn model parameters (H and a) from the MSE perspective requirement. This paper introduces new closed-form estimates that approximate the MSE tailored to match gfGn scenarios that have a lower computational burden compared to the literature-known expressions and that are easily adaptable from the computational burden point of view to different pairs of H and a parameters. Thus, the system requires less substantial computational resources and might be more cost-effective.

Hybrid fiber-based time synchronization and vibration detection system.

We propose a hybrid fiber-based time synchronization and vibration detection system. The vibration is detected by exploring the idle light of the time synchronization system, i.e., the Rayleigh backscattering of the timing pulse disseminated in the fiber link. The addition of a sensing function does not affect the performance of time synchronization. In the multiuser experimental demonstration, time deviation results are 3.6 ps at τ = 1 s and 1.4 ps at τ = 104 s on the 40-km fiber link. Meanwhile, the hybrid system can accurately detect and locate vibrations occurring on the link. This method enables multiple functions of the optical fiber network without occupying extra optical channels. Moreover, it gives a possible solution for enhancing the security of the time synchronization network through vibration detection.

Enable Precise Timing with Clock Ensemble in Packet Networks

The need for accurate and reliable time is increasingly important for network infrastructures with precise timing requirements. Traditional time distribution in networks is carried out through dedicated synchronization networks, whose networking mode may limit the applicability of time synchronization for emerging applications in terms of synchronization performance, cost-effectiveness, and reliability. This paper introduces a new concept of Network Clock Ensemble (NCE) and explores the feasibility of constructing an innovative mechanism for network time synchronization. Specifically, an NCE scheme is proposed based on a software-defined time synchronization network architecture to obtain time accuracy and stability by forming a synergistic effect between clocks in packet networks. The NCE model and method are used to reveal the precise timing mechanism. Simulation experiments and numerical analysis results show that our scheme can achieve significant performance improvements in terms of time accuracy and stability. Furthermore, with the improvement of the network time synchronization performance, the NCE results gradually approximate the Clock Ensemble (CE) results in the actual test, further verifying the effectiveness and feasibility of the proposed scheme.

Color-Based Time Synchronization for Future Networks: Advantages, System Architecture, and Potential Use Cases

Color-Based Time Synchronization for Future Networks: Advantages, System Architecture, and Potential Use Cases

Prespecified Time Synchronization of Coupled Dynamic Network With Impulsive Effect Via Quantized Control

In this paper, prespecified time synchronization (PTS) is addressed for dynamic networks with impulsive effects and directed topology. The less conservative cases considering the synchronizing and desynchronizing impulses simultaneously are presented, and the discontinuous nonlinear functions are also involved. Moreover, by constructing a quantized prespecified time (PT) controller, some constraints on impulsive interval are relaxed, which makes our results more widely applicable. Sufficient conditions are derived to realize PTS of impulsive dynamic networks. In addition, synchronization time of PTS is independent to any parameters. Numerical examples are provided to show the validity of our theoretical results.

Prespecified time synchronization of dynamic complex network via intermittent event-triggered control

This paper deals with prespecified time synchronization (PTS) for dynamic networks via intermittent event-triggered control (IETC). A novel lemma is developed to analyze PTS under the intermittent control framework. During the controlled intervals of the intermittent control mechanism, an event-triggered mechanism is devised by incorporating a function that gradually approaches zero as time approaches the settling time, acting as a threshold. Correspondingly, the intermittent event-triggered controller is constructed to achieve PTS of controlled networks. With the help of the designed intermittent event-triggered prespecified time (PT) controller, some simpler sufficient criterion are derived for realizing PTS. Additionally, it is demonstrated that the designed controller maintain bounds despite an increase in control gain and the control process is free of Zeno phenomena. And some numerical examples are represented to substantiate our theoretical results.

High-precision Time Synchronization Algorithm for Unmanned Aerial Vehicle Ad Hoc Networks based on Bidirectional Pseudo-range Measurements

The increasing demand for missions involving unmanned aerial vehicles (UAVs) raises the need for reliable and accurate time synchronization in ad hoc networks. Time synchronization plays a crucial role in coordinating the actions of multiple UAVs, particularly when it comes to positioning, coordination, and data fusion. However, achieving high-precision time synchronization is challenging due to the difficult-to-estimate communication transmission delay, measurement noise, relative motion, and clock source characteristics in wireless ad hoc networks formed by UAVs. To address this issue, this paper proposes a fully distributed high-precision network time synchronization algorithm that is suitable for multi-hop dynamic ad hoc networks. The proposed algorithm is based on bidirectional pseudo-range measurements, graph theory, and random matrix correlation theory. It is composed of relative clock skew estimation, logic clock skew compensation and logic clock offset compensation. The algorithm is rigorously derived, requiring no central node, and it is capable of obtaining relative clock skew even when nodes broadcast clock information asynchronously. In addition, the proposed algorithm enables real-time elimination of transmission delays and has noise-resistant capabilities. Simulation results validate the effectiveness of the algorithm, demonstrating that the time synchronization accuracy in UAV ad hoc networks can reach the sub-nanosecond level.

Using All-Digital On-Chip Syntonistor to Compensate Clock Frequency Error in Network Time Synchronization for Accuracy Reaching to Sub-µs Range

The emergence of Internet of Everything has made time-awareness a feature of high priority. One of the enabling factors is time synchronization. High quality synchronization demands frequency source of high stability, which is pricey and bulky. When low-end source is used, synchronization quality would be severely impaired. This situation can be improved by the technique of time synchronization. In mainstream approaches, however, the frequency of clock pulse train is not tuned due to the lack of appropriate tool. As requirement for synchronization advances into microsecond or even nanosecond regime, frequency tuning in hardware is expected to be beneficial. Moreover, wireless networks do not have frequency transfer mechanism. This exacerbates the problem of frequency deviation. Those issues make syntonization (synchronization of frequency) become necessary. In this work, an all-digital frequency-tunable clock source is used as on-chip syntonistor to physically compensate the clock frequency errors of nodes in a network. Time discrepancies are hence alleviated. A wireless network has been built to validate this scheme. Time synchronization quality has reached to sub-µs range. The key contribution is the suggestion of adopting on-chip syntonistor for improving the quality of network synchronization. This work serves as a demonstration of this new scheme.

Precise GNSS Time Synchronization With Experimental Validation in Vehicular Networks

Time synchronization utilizing the Global Navigation Satellite System (GNSS) is being increasingly investigated for vehicular networks. Due to GNSS signal blockages, the availability and accuracy of GNSS timing solutions in various road settings is a recognized challenge. With the recent improvement of Multi-GNSS technology and the increased capacity of consumer-grade receivers, the application of GNSS in vehicular environments has brightened up. This paper systematically analyzes the required time synchronization of vehicular networks and presents a GNSS-based time synchronization solution. It also experimentally demonstrates the availability and capabilities of GNSS time synchronization using commercial-grade GNSS receivers and off-the-shelf communication devices. Our experiments show that the timing accuracy of an individual vehicular node can be as good as ±2 microseconds, resulting in synchronization accuracy of sub-10 microseconds among nodes. A momentary complete outage of the GNSS time solution due to signal blockage on the road adds clock error, leading to synchronization inaccuracy of up to sub-20 microseconds. This level of inaccuracy still meets the desired requirement for most applications in vehicular communication.

Reference Broadcast-Based Secure Time Synchronization for Industrial Wireless Sensor Networks

Security is an important factor that cannot be neglected in the design of time synchronization algorithms since industrial wireless sensor networks are prone to attacks against physical nodes and communication links. The Sybil attack is an intelligent attack with a high destructive capacity in pretending multiple identities and broadcasting illegitimate messages to destroy the network operation. Existing secure time synchronization algorithms mostly focus on distributed protocols; however, they pay less attention to Sybil attacks and centralized network time synchronization. In this paper, we propose a novel reference broadcast-based secure time synchronization (RSTS) for industrial wireless sensor networks with a time source against Sybil attacks. Different from previous protocols, in converging the network structure and the clock status, RSTS employs a public neighbor forwarding mechanism based on reference broadcast to filter the illegal time information automatically. Instead of establishing a table with timestamps of packet transmission and receipt, the least square linear regression is utilized to estimate the compensation relative to the source node with the recorded time and calculated time difference in receiving packets. The simulation results demonstrate that RSTS is resilient to Sybil attacks as well as message manipulation attacks in comparison with existing algorithms.

Time Synchronization and Signal Detection in Non-Orthogonal Unicast and Broadcast Networks

The next generation digital TV (DTV) broadcast, namely Advanced Television System Committee (ATSC) 3.0, relies on substantial single frequency networks (SFN), each of which requires a studio to transmitter link (STL) to transmit data from the broadcast gateway (BG), leading to significant construction costs. Therefore, the wireless in-band distribution link (IDL) technology is proposed, which uses layered-division multiplexing (LDM) to transmit the STL data via wireless links from the BG to the SFN transmitters within the same spectrum as the broadcast services. In this paper, we propose the time synchronization and signal detection algorithm for wireless IDL systems with both unicast and broadcast signals. We introduce two multiplexing schemes, N-LDM and 3-LDM, and demonstrate their superiority over traditional frequency division multiplexing (FDM). To overcome the challenge of multi-access interference and synchronization errors caused by multipath, we develop a unique word (UW) design algorithm for transmitted signals and a double threshold correlation detection algorithm (DTCDA) that outperforms traditional ones. We employ a second threshold to enhance detection performance at low signal-to-noise ratios, and utilizes successive interference cancellation (SIC) to mitigate multiple-access interference. More importantly, our approach requires no knowledge of the unicast user number or channel state information. Simulation results validate the effectiveness of the proposed scheme.

Parameter-Sharing-Based Average-Consensus Time Synchronization in IoT Networks

Average-consensus protocol is one of the ways to develop distributed time-synchronization algorithms in Internet of Things (IoT) networks. However, the large number of iteration leads to a common time notion issue in nodes. This poses a critical challenge in the convergence of the time-synchronization algorithm and resulting asymptotic convergence in the average consensus protocol. In this paper, a parameter-sharing-based average-consensus time-synchronization (PACTS) algorithm is proposed. For fast convergence, the proposed PACTS quickly forwards the time information to multi-hop nodes and employs multi-hop average-consensus instead of single-hop average-consensus. Specifically, a node asynchronously and periodically broadcasts the relative clock offset estimation of neighbors with its local time information. Meanwhile, the relative clock offset estimation of the multi-hop node is calculated and used to estimate the average value. Consequently, an average-consensus among local multi-hop nodes is obtained. As a result, the iteration number and convergence time are significantly reduced over the network. Finally, the experimental results indicate that the proposed PACTS algorithm has low complexity, high accuracy, and quick convergence.

Analysis of application of network time synchronization technology in plant and station automation system

As the inevitable result of the development of social economy and science and technology, the construction of plant and station automation system not only solves the problems existing in the traditional plant and station construction management, but also improves the fundamental requirements of the system operation. According to the accumulated experience in the construction and application of plant and station automation system in recent years, the scholars of various countries should not only ensure the accuracy and high precision of time measurement, but also scientifically control the complexity of application algorithm to reduce the amount of electric energy consumption. Therefore, on the basis of understanding the research status of plant and station automation system and network time synchronization technology, this paper mainly explores how to apply network time synchronization technology in plant and station automation system according to the structure of plant and station automation system and the key points of network time synchronization technology.

Fast and Low-Overhead Time Synchronization for Industrial Wireless Sensor Networks with Mesh-Star Architecture.

Low-overhead, robust, and fast-convergent time synchronization is important for resource-constrained large-scale industrial wireless sensor networks (IWSNs). The consensus-based time synchronization method with strong robustness has been paid more attention in wireless sensor networks. However, high communication overhead and slow convergence speed are inherent drawbacks for consensus time synchronization due to inefficient frequent iterations. In this paper, a novel time synchronization algorithm for IWSNs with a mesh-star architecture is proposed, namely, fast and low-overhead time synchronization (FLTS). The proposed FLTS divides the synchronization phase into two layers: mesh layer and star layer. A few resourceful routing nodes in the upper mesh layer undertake the low-efficiency average iteration, and the massive low-power sensing nodes in the star layer synchronize with the mesh layer in a passive monitoring manner. Therefore, a faster convergence and lower communication overhead time synchronization is achieved. The theoretical analysis and simulation results demonstrate the efficiency of the proposed algorithm in comparison with the state-of-the-art algorithms, i.e., ATS, GTSP, and CCTS.

Single-Timestamp Skew Correction (STSC) in V2X Networks

Modern vehicles nowadays have many capabilities apart from the basic function of driving. These are now intelligent, smart, and can communicate over the Internet. A vehicle-to-everything (V2X) wireless network represents a network where vehicles communicate vital sensor data with other vehicles, pedestrians, and fixed infrastructure over the internet. There are various challenges in V2X communication that may affect the efficiency of autonomous devices, systems, and infrastructure. Of the many challenges, time synchronization among many devices in V2X networks is a key challenge. In a V2X network, all nodes within the network need to be time-synchronized; this is essential for task scheduling, computation off-loading, event sequencing, resource sharing, and efficient utilization of resources in the network. In recent works, many researchers have addressed time synchronization in V2X networks by considering multiple timestamps in order to estimate the time skew offset with varying results. In this paper, we consider a skew-based approach, namely, a single-timestamp skew correction (STSC) for time synchronization in V2X networks. The proposed method needs a single timestamp to estimate time skew at the hardware level with the help of physical-layer time synchronization using symbol timing recovery. Implementation results prove that the STSC accurately synchronizes the nodes in phase and frequency, therefore resulting in a greater accuracy and better energy savings in the V2X networks.

Reinforcement learning based flow and energy management in resource-constrained wireless networks

This paper aims at developing a learning-based framework for MAC sleep–listen–transmit scheduling in wireless networks. The Reinforcement Learning-based paradigm is shown to work in the absence of network time-synchronization and other complex hardware features, such as carrier-sensing, thus making it suitable for low-cost transceivers for IoT and wireless sensor nodes. The framework allows wireless nodes to learn policies that can support throughput-sustainable flows while minimizing node energy expenditure and sleep-induced packet drops and delays. Each node independently learns a scheduling policy without explicit communication with other network nodes. The trade-off between packet drops and energy efficiency is analyzed, and an application-specific solution is proposed for handling the trade-off. It is shown how this model allows users to prioritize between energy efficiency and packet drops depending on specific application requirements. An analytical model is developed for understanding the underlying system dynamics, which is also validated using extensive simulation experiments. Moreover, the developed mechanism is experimented with for heterogeneous network topologies and traffic patterns

New criteria for predefined finite time synchronization of memristor-based neural networks

The fast synchronization problem of memristor-based neural networks is studied in this article. Firstly, a novel predefined finite time stability of a class of nonlinear dynamical systems is investigated under the incomplete beta function, complete beta function, and inequality technology. Then, an active predefined finite time controller is designed that guarantees finite time stability of synchronization errors of two memristor-based neural networks with/without proportional delay. Some simulation results are presented to show the effectiveness of theoretical results.

New criteria of finite time synchronization of fractional-order quaternion-valued neural networks with time delay

In this paper, to simulate some situations in the real world, a class issue of finite-time synchronization (FTS) about fractional-order quaternion-valued neural networks (FOQVNNs) with time delay is discussed. Firstly, there is no need to divide the QVNNs into several subsystems, some new lemmas related to the sign function of quaternion-valued are established in the quaternion domain. Secondly, based on the proposed sign function framework, a concise and effective controller is directly designed and FTS criteria are derived by constructing the Lyapunov function. Moreover, two settling times of synchronization are effectively estimated. Finally, some examples are shown to testify the correctness of the presented theoretical results.

Energy Stimulated Time Synchronization for Energy Harvesting Wireless Networks

In this work, we develop a new energy-preserving time synchronization method, called the energy stimulated time sync (ESTS), for ultra-low-power wireless networks with energy harvesting capabilities. Compared with existing methods, ESTS does not rely on timestamp exchange but uses short energy tones to synchronize the nodes within the receiving range. ESTS is a centralized synchronization method based on a fully-passive wake-up radio (WuR) circuit, which can provide a variety of synchronization accuracy to meet different application requirements while consuming much lower energy than timestamp-based synchronization methods. We have implemented ESTS on Microchip ATmega256RFR2 system-on-chip (SoC). According to experiment results, ESTS can achieve an average of 5 ms and 70 <inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>s time precision for rough synchronization and fine synchronization, respectively. Moreover, the fully-passive WuR circuit consumes zero energy in the idle status. In the entire synchronization process, the rough synchronization only needs to be performed once, and the node consumes as low as 4 <inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>J of energy for each fine synchronization, making ESTS a promising solution for ultra-low-power wireless networks.

Related Biological Factors of Mobile Sensor Network Technology on Sprint Performance

Node localization and temporal synchronization, as two key parts of each self-organized and localization-aware wireless sensor network (WSN), have been a key topic for research and applications. The initial prototype of the sensor network is the same as that of the local area network. All nodes are connected by wires, and there is a central control node. All nodes transmit data to the central node point-to-point. With the development and progress of wireless communication technology, the current sensor network has developed into a WSN. Without a central node, all nodes can communicate with each other; so, it is natural to develop positioning technology in WSN. Node positioning in wireless sensor networks refers to the process in which sensor nodes determine the location information of other nodes in the network through a certain positioning technology based on the location information of a few known nodes in the network. The principle of positioning is purely geometric in mathematics. With the in-depth promotion of WSN in the application field, there are more and more requirements for high precision positioning, the higher the positioning accuracy, the higher the requirements for network time synchronization, and the problem of node clock synchronization and high precision positioning of the node can be studied together. Solving the problem of node clock synchronization can further provide support for node positioning in a variety of different environments. As a new ultrabroadband (UWB) carrier-free communication technology with nanoscale temporal resolution, it has been widely used in high-precision node positioning systems in recent years, UWB technology is the most advanced noncarrier wireless communication technology that uses bandwidths above 1 GHz and uses nonsine wave narrow pulses from nanoseconds to picoseconds to transmit data. Therefore, it occupies a very wide spectrum. UWB technology has the advantages of low system complexity, low transmit signal power spectrum density, insensitive to channel fading, and high positioning accuracy. It is especially suitable for high-speed wireless access in dense multipath places such as indoors, providing a technical basis for the engineering implementation of high-precision positioning algorithms. However, the current situation of Chinese track and field events has not kept pace with the development of Chinese competitive sports, and even the level of individual events has a gradual decline. Therefore, it is very meaningful to study the relevant biological factors that affect sprint performance. This article analyzes the related biological factors that affect the performance of the sprint, combines the knowledge of physiology to analyze the training methods that appear in the sprint from the physiological perspective, and analyzes the related biological factors that affect the performance of the sprint. This article chooses to divide them into men’s group (3 groups) and women’s group (3 groups), with 4 people in each group. Experiment proved that after the experiment, these are the following factors: the fatigue of the nervous system, the technical difference of sprinting, the change of muscle fiber enzyme activity, the order of muscle fiber cross-sectional area and muscle activation, and the recruitment of muscle fiber types. Impact P value less than 0.05, which shows that the factors that affect sprint performance are complex, and the biological factors that affect step length can be studied through anthropometry. The impact of step frequency on sports performance is very important.