An evaluation of network time protocol for clock synchronization in wide area measurements

Wang, Lei; Fernandez, Javier Oscar; Burgett, Joseph M.; Conners, Richard W.; Li, Fangxing

doi:10.1109/pes.2008.4596234

Cited by 13 publications

(2 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…By contrast, GPS receiver algorithms (in this work, our proposed SR-DKF algorithm) play a key role in maintaining a bound on both the synchronization errors between any two receivers and the absolute time at each receiver in the network. This indicates a standard implementation of PMUs/power grids since the development of newer clocks, for example, the chip-scale atomic clock (CSAC) and communication protocols such as network-time protocol (NTP) and precise-time protocol (PTP) that can provide up to tens of microsecond-level accuracy over shorter time spans (Allnutt et al, 2017;Wang et al, 2008;Zhan et al, 2017).…”

Section: A Distributed Processing Frameworkmentioning

confidence: 99%

GPS Spoofing Mitigation and Timing Risk Analysis in Networked Phasor Measurement Units via Stochastic Reachability

Bhamidipati

Gao

2023

navi

View full text Add to dashboard Cite

Modern power systems analyze real-time grid stability using a widely-dispersed network of advanced devices known as phasor measurement units (PMUs) (Al-Hammouri et al., 2012). As per the American Recovery and Reinvestment Act of 2009, more than 2500 PMUs were deployed across North America as of March 2015 (Tholomier et al., 2009). Figure 1 shows a map of the dense network of these spatially-distributed PMUs (Dagle, 2018). The North American synchrophasor initiative network (NASPInet), which is a collaborative effort by the United States Department of Energy and the North American Electric Reliability Corporation, provides a secure and decentralized infrastructure for communication among the PMUs (Myrda & Koellner, 2010). Each PMU is equipped with a Global Positioning

show abstract

Section: A Distributed Processing Frameworkmentioning

confidence: 99%

GPS Spoofing Mitigation and Timing Risk Analysis in Networked Phasor Measurement Units via Stochastic Reachability

Bhamidipati

Gao

2023

navi

View full text Add to dashboard Cite

show abstract

“…Despite the solid results that offers the NTP method, it can provide inaccurate results when networks are heavily loaded [178], or when the OS of the devices are not specifically designed to deal with time-controlled applications [185], such as Android devices. Even presenting inaccuracies, NTP is still widely used since it offers synchronization of the order of tens of milliseconds [186], which is suitable in applications where a tight clock synchronization is not needed. A native procedure is available in Android OS based on NTP to synchronize its own clock [187].…”

Section: Introductionmentioning

confidence: 99%

Smart Sound Control in Acoustic Sensor Networks: a Perceptual Perspective

Campos¹

View full text Add to dashboard Cite

Audio systems have been extensively developed in recent years thanks to the increase of devices with high-performance processors capable of performing more efficient audio processing. In addition, the expansion of wireless communications has given the possibility of implementing networks in which devices can be placed in different locations without physical limitations, unlike wired networks. The combination of these technologies has led to the emergence of Acoustic Sensor Networks (ASN). An ASN is composed of nodes equipped with audio transducers, such as microphones or speakers. In the case of acoustic field monitoring, only acoustic sensors (or microphones) need to be incorporated into the ASN nodes. However, in the case of control applications, the nodes must interact with the acoustic field through loudspeakers.The ASN can be implemented through low-cost devices, such as Raspberry Pi or commercial mobile devices, capable of managing multiple microphones and loudspeakers and offering good computational capacity. In addition, these devices can communicate through wireless connections, such as Wi-Fi or Bluetooth. This ASN design provides high processing power and flexibility due to the processors and the wireless communications offered by the current mobile devices. Therefore, in this dissertation, an ASN composed of commercial mobile devices connected to wireless speakers through a Bluetooth link is proposed. Additionally, the problem of synchronization between the devices in an ASN is one of the main challenges to be addressed since the audio processing performance is very sensitive to the lack of synchronism. Therefore, a deep analysis of the synchronization problem between commercial devices connected to wireless speakers in an ASN is also carried out. In this regard, one of the main contributions is the analysis of the audio latency of mobile devices when the acoustic nodes in the ASN are comprised of mobile devices communicating with the corresponding loudspeakers through Bluetooth links. A second significant contribution of this dissertation is the implementation of a method to synchronize the different devices of an ASN, together with a study of its limitations. Finally, the proposed method has been introduced in order to implement personal sound zones (PSZ) applications. Therefore, the implementation and analysis of the performance of different audio applications

show abstract

Experimental validation of 4D log file‐based proton dose reconstruction for interplay assessment considering amplitude‐sorted 4DCTs

et al. 2022

View full text Add to dashboard Cite

Purpose The unpredictable interplay between dynamic proton therapy delivery and target motion in the thorax can lead to severe dose distortions. A fraction‐wise four‐dimensional (4D) dose reconstruction workflow allows for the assessment of the applied dose after patient treatment while considering the actual beam delivery sequence extracted from machine log files, the recorded breathing pattern and the geometric information from a 4D computed tomography scan (4DCT). Such an algorithm capable of accounting for amplitude‐sorted 4DCTs was implemented and its accuracy as well as its sensitivity to input parameter variations was experimentally evaluated. Methods An anthropomorphic thorax phantom with a movable insert containing a target surrogate and a radiochromic film was irradiated with a monoenergetic field for various 1D target motion forms (sin, sin4) and peak‐to‐peak amplitudes (5/10/15/20/30 mm). The measured characteristic film dose distributions were compared to the respective sections in the 4D reconstructed doses using a 2D γ‐analysis (3 mm, 3%); γ‐pass rates were derived for different dose grid resolutions (1 mm/3 mm) and deformable image registrations (DIR, automatic/manual) applied during the 4D dose reconstruction process. In an additional analysis, the sensitivity of reconstructed dose distributions against potential asynchronous timing of the motion and machine log files was investigated for both a monoenergetic field and more realistic 4D robustly optimized fields by artificially introduced offsets of ±1/5/25/50/250 ms. The resulting dose distributions with asynchronized log files were compared to those with synchronized log files by means of a 3D γ‐analysis (1 mm, 1%) and the evaluation of absolute dose differences. Results The induced characteristic interplay patterns on the films were well reproduced by the 4D dose reconstruction with 2D γ‐pass rates ≥95% for almost all cases with motion magnitudes ≤15 mm. In general, the 2D γ‐pass rates showed a significant decrease for larger motion amplitudes and increase when using a finer dose grid resolution but were not affected by the choice of motion form (sin, sin4). There was also a trend, though not statistically significant, toward the manually defined DIR for better quality of the reconstructed dose distributions in the area imaged by the film. The 4D dose reconstruction results for the monoenergetic as well as the 4D robustly optimized fields were robust against small asynchronies between motion and machine log files of up to 5 ms, which is in the order of potential network latencies. Conclusions We have implemented a 4D log file‐based proton dose reconstruction that accounts for amplitude‐sorted 4DCTs. Its accuracy was proven to be clinically acceptable for target motion magnitudes of up to 15 mm. Particular attention should be paid to the synchronization of the log file generating systems as the reconstructed dose distribution may vary with log file asynchronies larger than those caused by realistic network delays.

show abstract

An evaluation of network time protocol for clock synchronization in wide area measurements

Cited by 13 publications

References 4 publications

GPS Spoofing Mitigation and Timing Risk Analysis in Networked Phasor Measurement Units via Stochastic Reachability

GPS Spoofing Mitigation and Timing Risk Analysis in Networked Phasor Measurement Units via Stochastic Reachability

Smart Sound Control in Acoustic Sensor Networks: a Perceptual Perspective

Experimental validation of 4D log file‐based proton dose reconstruction for interplay assessment considering amplitude‐sorted 4DCTs

Contact Info

Product

Resources

About