CoSiWiNeT: A Clock Synchronization Algorithm for Wide Area IIoT Network

Recent advances in the industrial internet of things (IIoT) and cyber–physical systems drive Industry 4.0 and have led to remote monitoring and control applications that require factories to be connected to remote sites over wide area networks (WAN). The adequate performance of remote applications depends on the use of a clock synchronization scheme. Packet delay variations adversely impact the clock synchronization performance. This impact is significant in WAN as it comprises wired and wireless segments belonging to public and private networks, and such heterogeneity results in inconsistent delays. Highly accurate, hardware–based time synchronization solutions, global positioning system (GPS), and precision time protocol (PTP) are not preferred in WAN due to cost, environmental effects, hardware failure modes, and reliability issues. As a software–based network time protocol (NTP) overcomes these challenges but lacks accuracy, the authors propose a software–based clock synchronization method, called CoSiWiNeT, based on the random sample consensus (RANSAC) algorithm that uses an iterative technique to estimate a correct offset from observed noisy data. To evaluate the algorithm’s performance, measurements captured in a WAN deployed within two cities were used in the simulation. The results show that the performance of the new algorithm matches well with NTP and state–of–the–art methods in good network conditions; however, it outperforms them in degrading network scenarios.

Chapter 1 LHAASO Instruments and Detector technology

The Large High Altitude Air Shower Observatory ( LHAASO ) ( Fig. 1 ) is located at Mt. Haizi (4410 m a.s.l., 600 g/cm2, 29◦ 21’ 27.56” N, 100◦ 08’ 19.66” E) in Daocheng, Sichuan province, P.R. China. LHAASO consists of 1.3 km2 array ( KM2A ) of electromagnetic particle detectors ( ED ) and muon detectors ( MD ), a water Cherenkov detector array ( WCDA ) with a total active area of 78,000 m2, 18 wide field-of-view air Cherenkov telescopes (WFCTA ) and a newly proposed electron-neutron detector array ( ENDA ) covering 10,000 m2. Each detector is synchronized with all the other through a clock synchronization network based on the White Rabbit protocol. The observatory includes an IT center which comprises the data acquisition system and trigger system, the data analysis facility. In the following of this Chapter, all the above mentioned components of LHAASO will be briefly described, together with infrastructure which is a fundamental component of the LHAASO observatory.

A clock synchronization method in power dispatching based on BeiDou navigation system

This paper introduces the problems of poor signal condition of a single time source in time synchronization or error in time source switching in the power system. It adopts the two-clock mode timing scheme of BeiDou 2 synchronous satellite and GPS synchronous satellite to ensure the stable output of the main clock within a certain accuracy. The system takes full advantage of the field programmable gate array (FPGA) hardware method, aligns the internal clock lock signal with the input second pulse phase, and proposes an improved method for the problem of large clock synchronization deviation based on the network, which proves the effectiveness and superiority of the system to accurately output the pulse and provide reliable time synchronization for the power dispatching system.

An optimization method of clock synchronization for large-scale regional power network based on IEEE 1588

At present, mobile devices generally use GPS, Beidou and other satellite time service methods to obtain time, but the clock synchronization based on IEEE 1588 protocol still has deviation. To solve this problem, a clock synchronization method is proposed to improve IEEE 1588 protocol. Based on the analysis of IEEE 1588 protocol, the clock deviation and frequency deviation which affect the synchronization accuracy are modeled. The second-order Kalman filtering algorithm is used to recursively deduce the clock deviation and frequency deviation, and the Allan variance is used to verify the noise characteristics and constantly correct the clock deviation. Finally, the improved effect is verified by relevant experiments. The results show that the improved system can improve the synchronization accuracy.