Synchronization Algorithm Research Articles

Research on Teaching Resource Management in Colleges and Universities Based on Multiple Data Chain Networks

Abstract In this paper, we first take the datalink network as the entry point and construct a university teaching resource management model based on a multivariate datalink network. A Link-22 data chain time synchronization algorithm with KF-RTPT is proposed to address the actual existence and unavoidable time deviation based on accuracy and timestamp acquisition errors. Meanwhile, a time slot allocation and optimization algorithm designed to maximize message transmission benefits is being developed to optimize the allocation of node time slot requirements. Finally, the constructed teaching resource management model is empirically analyzed from three perspectives: error optimization, dynamic time slot allocation, and model application effect. According to the findings, the KF-RTPT algorithm increases motion error efficiency by 3.83 in low-speed motion states and 8.16 in high-speed motion states when compared to the conventional RTT method. This effectively eliminates motion error and boosts the effectiveness of teaching and managing resources in colleges and universities.

Time Synchronization in Satellite Quantum Key Distribution

Time synchronization is one of the most crucial issues that must be addressed in developing quantum key distribution (QKD) systems. It not only lets the transmitter and the receiver to assign a sequence number to each event and then do correct basis reconciliation, but also allows to increase signal-to-noise ratio. Time synchronization in satellite communications is especially complicated due to such factors as high loss, signal fading, and Doppler effect. In this work, a simple, efficient, and robust algorithm for time synchronization is proposed. It was tested during experiments on QKD between Micius, the world’s first quantum communications satellite, and an optical ground station located in Russia. The obtained synchronization precision lies in the range from 467 to 497ps. The authors compare their algorithm for time synchronization with the previously used methods. The proposed approach can also be applied to terrestrial QKD systems.

Multisensor and Multiscale Data Integration Method of TLS and GPR for Three-Dimensional Detailed Virtual Reconstruction.

Integrated TLS and GPR data can provide multisensor and multiscale spatial data for the comprehensive identification and analysis of surficial and subsurface information, but a reliable systematic methodology associated with data integration of TLS and GPR is still scarce. The aim of this research is to develop a methodology for the data integration of TLS and GPR for detailed, three-dimensional (3D) virtual reconstruction. GPR data and high-precision geographical coordinates at the centimeter level were simultaneously gathered using the GPR system and the Global Navigation Satellite System (GNSS) signal receiver. A time synchronization algorithm was proposed to combine each trace of the GPR data with its position information. In view of the improved propagation model of electromagnetic waves, the GPR data were transformed into dense point clouds in the geodetic coordinate system. Finally, the TLS-based and GPR-derived point clouds were merged into a single point cloud dataset using coordinate transformation. In addition, TLS and GPR (250 MHz and 500 MHz antenna) surveys were conducted in the Litang fault to assess the feasibility and overall accuracy of the proposed methodology. The 3D realistic surface and subsurface geometry of the fault scarp were displayed using the integration data of TLS and GPR. A total of 40 common points between the TLS-based and GPR-derived point clouds were implemented to assess the data fusion accuracy. The difference values in the x and y directions were relatively stable within 2 cm, while the difference values in the z direction had an abrupt fluctuation and the maximum values could be up to 5 cm. The standard deviations (STD) of the common points between the TLS-based and GPR-derived point clouds were 0.9 cm, 0.8 cm, and 2.9 cm. Based on the difference values and the STD in the x, y, and z directions, the field experimental results demonstrate that the GPR-derived point clouds exhibit good consistency with the TLS-based point clouds. Furthermore, this study offers a good future prospect for the integration method of TLS and GPR for comprehensive interpretation and analysis of the surficial and subsurface information in many fields, such as archaeology, urban infrastructure detection, geological investigation, and other fields.

HyNTP: A Distributed Hybrid Algorithm for Time Synchronization

This paper presents a distributed hybrid algorithm that synchronizes the time and rate of a set of clocks connected over a network. Clock measurements of the nodes are given at aperiodic time instants and the controller at each node uses these measurements to achieve synchronization. Due to the continuous and impulsive nature of the clocks and the network, we introduce a hybrid system model to effectively capture the dynamics of the system and the proposed hybrid algorithm. Moreover, the hybrid algorithm allows each agent to estimate the skew of its internal clock in order to allow for synchronization to a common timer rate. We provide sufficient conditions guaranteeing synchronization of the timers, exponentially fast, with robustness. Numerical results illustrate the synchronization property induced by the proposed algorithm as well as its performance against comparable algorithms from the literature.

Сравнительный анализ точности алгоритмов частотной синхронизации для системы спутниковой связи на основе сигнала DVB-S2

The paper investigates the schemes of frequency synchronization of signal reception of satellite communication system based on DVB-S2 standard with different combinations of coarse and fine frequency synchronization algorithms, namely, the following pairs of algorithms are considered: «Edge band» and «Delay & Multiply», «Delay & Multiply» and «L&R», «Edge band» and «L&R», where the first algorithm in each pair performs the task of coarse and the second algorithm performs the task of fine frequency synchronization. The accuracy of the investigated frequency synchronization schemes is evaluated using the Root Mean Square Error (RMSE) metric of frequency offset estimation in the channel. In addition, one of the performance metrics of the algorithm is the estimation of synchronization time. The frequency shift in the signal transmission channel is set constant and equal to 20% of the signal bandwidth. Using combinations of Non-Data-Aided (blind) algorithms for coarse frequency shift estimation and Data-Aided algorithms for fine frequency synchronization, the synchronization time can be reduced by almost a factor of 2, while maintaining high accuracy of RMS estimation.

Алгоритм адаптивной кадровой синхронизации в системах сверхширокополосной радиосвязи

This paper introduces adaptive frame synchronization algorithm in HRP mode of IEEE 802.15.4-2020 radiocommunication system under unintentional; interference signals transmitted in HRP-CoU mode. Proposed algorithm is based on nulls adding to synchronization sequences and packet error rate control. True detection probability is estimated by MATLAB model.

Improved autocorrelation method for time synchronization in filtered orthogonal frequency division multiplexing

Time synchronization is essential in multicarrier systems such as filtered orthogonal frequency division multiplexing (F-OFDM) because it determines the whole system’s performance. Differ with OFDM, where subcarrier allocation is not flexible. In F-OFDM, the subcarrier allocation is more flexible, and the whole subcarrier in one symbol can be grouped into several subbands. The use of subcarriers that are limited to only one subband can reduce the performance of time synchronization based on autocorrelation (AC) methods. In this study, we first compare the performance of the AC-based time synchronization algorithms used in F-OFDM when training symbols are limited to one subband. Secondly, we made improvements to the AC-based time synchronization with the averaging technique of its timing metric, thus increasing the accuracy of time estimates in the F-OFDM system. The averaging technique of the timing metric improved the performance of the AC method in cases where the training symbol is limited to one subband, as shown in the simulation results.

An efficient hexadecimal network flow watermark method for tracking attack traffic

Network flow watermark technology is a traffic marking technique that embeds watermark information into the characteristics of network flows to mark and trace attack flows generated by network attackers. However, with the development of network attack techniques, the time and number of packets required for network attacks have decreased. Existing network flow watermark technologies fail to balance watermark robustness and efficiency, resulting in poor practicality. To address this issue, this paper proposes an efficient hexadecimal network flow watermark method. The method introduces an efficient interval watermark algorithm and utilizes an interval synchronization algorithm to self-learn watermark parameters, thereby improving the encoding efficiency of the watermark. The design of watermark start and end markers ensures the practicality of network watermarks, enabling traceability and source attribution of attack flows in real network environments. The proposed method is experimentally tested using real network traffic, and the results demonstrate that even in the presence of a network jitter, the watermark detection success rate of this scheme remains above 95%. Compared to other network flow watermark schemes, the hexadecimal network flow watermark proposed in this paper achieves a 50% improvement in encoding and decoding efficiency while ensuring robustness. It also exhibits excellent resistance to network jitter, packet loss, and false packet insertion.

Research on permanent magnet synchronous motor algorithm based on linear nonlinear switching self-disturbance rejection control

This paper presents a linear-nonlinear switching control strategy, called Switching Active Disturbance Rejection Control (SADRC), to enhance the disturbance rejection capability of the speed controller in a servo system. SADRC combines the advantages of Linear Active Disturbance Rejection Control (LADRC) and Nonlinear Active Disturbance Rejection Control (NLADRC), and introduces a parameter to switch between nonlinear and linear control, thereby improving the robustness of the servo system. Firstly, the mathematical model of the motor is analyzed as the starting point of the paper. Then, the basic principles of Active Disturbance Rejection Control (ADRC) are analyzed, and improvements are made to address its limitations, resulting in the design of SADRC. The parameters introduced in SADRC are analyzed to determine their appropriate ranges. Finally, the performance of SADRC is validated by comparing the rotational effects of Permanent Magnet Synchronous Motor (PMSM).

Synchronous fluorescence spectra-based machine learning algorithm with quick and easy accessibility for simultaneous quantification of polycyclic aromatic hydrocarbons in edible oils

Polycyclic aromatic hydrocarbons (PAHs) are one of the leading causes of human cancer. Four typical PAHs (PAH4) including benzo(a)pyrene (BaP), benzo(b)fluoranthene (BbF), benzo(a)anthracene (BaA), and chrysene (Chr) have been regarded as reasonable indicators for the occurrence of PAHs in food. In this study, the constant wavelength synchronous fluorescence (CWSF) spectra of PAH4 mixtures were used as the data sets without preprocessing and directly combined with the back propagation neural network (BPNN) algorithm to establish a quantitative analysis method of PAH4. This method is capable of predicting the concentrations of PAH4 in edible oil samples without pre-separation. The detection limits for BaP, BbF, BaA, and Chr were 0.014, 0.068, 0.026, and 0.013 μg/kg, respectively. The recoveries in various oil samples for BaP, BbF, BaA, and Chr were 99.5 ± 2.1, 101.0 ± 4.6, 98.6 ± 3.2, and 98.5 ± 4.9 %, respectively. The proposed method has proved to be a powerful tool for the rapid detection of PAH4.

Design and Implementation of a Low-Complexity Multi-h CPM Receiver with Linear Phase Approximation Synchronization Algorithm.

Multi-h continuous phase modulation (CPM), with extremely high spectral efficiency, involves the plague of high demodulation complexity with a large number of matched filters and a complex trellis. In this paper, an efficient all-digital demodulator for multi-h continuous phase modulation (CPM) is proposed based on a low-complexity decision-directed synchronization algorithm. Based on the maximum-likelihood estimation of the carrier phase and timing errors, we propose a reduced-complexity timing error detector with linear phase approximation (LPA) to the phase of the multi-h CPM. Compared with the traditional synchronization methods, it avoids derivative matched filtering and reduces about 2/3 of matched filters. The estimated accuracy and bit error rate (BER) performance of the LPA-based synchronization algorithm have no loss, as shown by the numerical simulation. Its stability is verified by the derived S-curve. Then, the receivers with the LPA-based synchronization for the three kinds of promising multi-h CPM are implemented on a Xilinx Kintex-7 FPGA platform. The experimental results show that the onboard tested BER of the proposed design has an ignorable loss in the numerical simulation. The implementation overhead on FPGA is significantly reduced by about 27% slices, 64% DSPs, and 70% block RAMs compared with the conventional method.

Adaptive nonlinear second-order sliding mode synchronization control of direct drive H-type platform with zero error constraint

In order to achieve better synchronization performance for H-type platform servo systems during motion, an adaptive nonlinear second-order sliding mode synchronous control method with zero error constraint is proposed in this paper. The reason and mechanism of unsynchronized movement of H-type platform are analyzed. A synchronous thrust allocation algorithm based on dynamics is designed by using the thrust balance equation under zero error constraint to suppress the rotation movement of the crossbeam theoretically. To minimize the impact of external disturbances on the system, the system employs a robust adaptive nonlinear second-order sliding mode control method. In this method, the nonlinear sliding mode function is constructed to enhance the dynamic performance of the system, the second-order sliding mode surface is designed to achieve chatter-free control input. To address the issue of limitations in sliding mode control caused by upper limits of external disturbances, an adaptive control technique is employed to estimate and compensate for uncertainties such as external disturbances. Experimental results demonstrate that the proposed synchronous control strategy can effectively adjust the operating conditions of the two motors, improve the synchronous control performance and enhance the anti-interference ability of the system.

Performances analysis of parallel asynchronous and synchronous algorithms on cloud architecture for PDE

In order to solve discretized stationary linear or non linear diffusion and convection–diffusion problems, the present paper deals with a comparison between the performances of parallel iterative synchronous or asynchronous algorithms implemented on a Cloud computing architecture with several sizes of the algebraic systems to be solved. The parallel algorithms are briefly and intuitively presented and analysis of their behavior is recalled. In particular, criteria of convergence are recalled and estimates of convergence speed are given. Implementation on cloud architectures are briefly described. Finally, for each kind of problem, the performance of the target algorithms on cloud architectures are analyzed.

An asynchronous simulation algorithm for post‐earthquake functional recovery of interdependent infrastructure systems

AbstractThe seismic resilience assessment of infrastructure systems not only requires evaluation of immediate damages after earthquakes, but also estimate of functional losses during the post‐earthquake recovery process. Infrastructure systems are interdependent during post‐earthquake recovery. To accurately consider this interdependence in resilience assessment, many studies have adopted post‐earthquake recovery simulation methods. In this study, an efficient asynchronous simulation algorithm is proposed, which does not require synchronous checking of the states of infrastructure elements at each time step, but rather asynchronously derives the functional recovery time of each element based on its dependency relationships. This study proves that the time complexity of the proposed asynchronous algorithm is proportional to the scale of the infrastructure system and is independent of the time step size. Furthermore, a case study of post‐earthquake recovery of a portfolio of buildings considering safety cordon areas is used to demonstrate that the asynchronous algorithm can significantly reduce the simulation time of large‐scale infrastructure systems compared to synchronous algorithms.

Optimizing wavefront coding for extended depth of field: a synchronous algorithm for optical element and decoding optimization.

Wavefront coding (WFC) combines phase mask design and image restoration algorithm to extend the depth of field (DOF) for various applications. However, discrete design limits finding globally optimal solutions, increasing the complexity of system design, and affecting the accuracy and robustness of image restoration. An end-to-end imaging system design has emerged to break through these limitations by integrating optical design and image processing algorithms. In this study, we propose an algorithm that synchronously optimizes the optical elements and decoding algorithm in WFC using ray-tracing simulation. We also derive formulas for the optical layer's forward and backward propagation for joint optimization of the optical layer and decoding algorithm. Experimental verification demonstrates the algorithm's effectiveness in optimizing the WFC system and offers improved performance under a unified design framework.

Data Synchronization in Vehicular Digital Twin Network: A Game Theoretic Approach

A fundamental issue of the vehicular digital twin (DT) is efficiently synchronizing the data between the DT and the vehicular user (VUE). In this paper, we consider the heterogeneous vehicular networks (HetVNets) in which a VUE can connect to the network through different networks. The HetVNets can improve the efficiency of communication by providing seamless connections. However, the uneven distribution of VUEs and the dynamics of HetVNets make the environment more complex. Therefore, we propose the network selection algorithm for data synchronization between VUEs and DTs in the HetVNets, where the behaviour between the VUEs is considered as a competition for wireless resources. A learning-based prediction model residing in the DT is developed where the DT can predict the waiting time of each relay and transmit the predicted results to the VUE for decision-making. We model the network selection problem as a potential game considering both the transmission time and the waiting time obtained from the prediction model and prove the existence of Nash equilibrium (NE). We analyze the performance of the proposed algorithm, and simulation results show that our approach can effectively find the optimal strategy while achieving a fast convergence speed and high-level performance compared to the baselines.

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.

Fast Kalman filter synchronization algorithm for cooperative synchronization in time sensitive networks

Clock synchronization is crucial in time-sensitive networks (TSN) to ensure the normal operation of devices. However, traditional synchronization techniques face challenges such as the accumulation of synchronization errors over multiple hops and slow synchronization speed, which hinder the development of large-scale and multi-hop TSN. In this paper, we propose a cooperative synchronization scheme based on two-way timestamp exchange to reduce error accumulation and enable synchronization information exchange between any node in the network and the reference node. Moreover, we develop a fast Kalman filter (FKF) algorithm to estimate clock offset and clock skew. To reduce time complexity, we replace the calculation of gain matrices with extremely high dimension with a small matrix based on the randomization matrix approximation in the updating phase of the Kalman Filter. Simulation results show that the proposed method significantly reduces synchronization complexity without sacrificing clock synchronization accuracy, making it highly promising for future TSN deployments.

EcoSync: An Energy-Efficient Clock Discipline Data Synchronization in Wi-Fi IoMT Systems

The growth of the Internet of Medical Things (IoMT) and healthcare data analytics allows wearable Wireless Body Area Networks (WBANs) and ambient sensors to collect the large quantities of physiological signals necessary for better patient diagnostics and treatments. Artificial intelligence and machine learning algorithms frequently require precisely synchronized signals from multiple sensors, which in turn require time-consuming and energy-inefficient synchronization methods with constant wireless network connectivity. We propose ecoSync, a highly energy-efficient time synchronization algorithm for Wi-Fi devices in IoMT applications. We demonstrated that ecoSync can correct the time difference error to ±42 µs with an hour between resynchronizations, using only 658 millijoules of energy. This is an 87% improvement in time difference error and a 99.93% reduction in energy usage over using TSF for synchronization alone over a 1 h period. Wireless synchronization of sensors allows placement of physiological sensors on objects of everyday use (Smart Stuff), which in turn allows seamless collection of physiological status data every time we interact with smart objects in an IoMT environment.

Robust Symbol Timing Synchronization for Initial Access under LEO Satellite Channel.

This paper proposes a robust symbol timing synchronization scheme for return link initial access based on the Digital Video Broadcasting-Return Channel via Satellite 2nd generation (DVB-RCS2) system for the Low Earth Orbit (LEO) satellite channel. In most cases, the feedforward estimator structure is considered for implementing Time Division Multiple Access (TDMA) packet demodulators such as the DVB-RCS2 system. More specifically, the Non-Data-Aided (NDA) approach, without using any kind of preamble, pilot, and postamble symbols, is applicable for fine symbol timing synchronization. However, it hinders the improvement in estimation accuracy, especially when dealing with short packet lengths during the initial access from the User Terminal (UT) to the Gateway (GW). Moreover, when a UT sends a short random access packet for initial access or resource request to the LEO satellite channel, the conventional schemes suffer from a large Doppler error depending on UT's location in a beam and satellite velocity. To ameliorate these problems, we propose a novel symbol timing synchronization algorithm for GW, and its advantage is confirmed through computer simulation.