Delay Asymmetry Compensation Scheme of Railway Time Synchronization Network

Youpeng Zhang; Jianrong Cao; Li Lan

doi:10.3788/LOP202158.0706003

Laser & Optoelectronics Progress, Volume. 58, Issue 7, 0706003(2021)

Delay Asymmetry Compensation Scheme of Railway Time Synchronization Network

Youpeng Zhang^1、*, Jianrong Cao^1、**, and Li Lan^2,3、***

Author Affiliations

¹School of Automatic & Electrical Engineering, Lanzhou Jiaotong University, Lanzhou , Gansu 730070, China

²School of Electronic & Information Engineering, Lanzhou Jiaotong University, Lanzhou , Gansu 730070, China

³Key Laboratory of Opt-Electronic Technology and Intelligent Control, Ministry of Education, Lanzhou Jiaotong University, Lanzhou , Gansu 730070, China

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Abstract Get PDF(in Chinese)

Figures & Tables(14)

Fig. 1. Simplified link model

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Fig. 2. Clock synchronization model

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Fig. 3. Simulation results of queuing delay

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Fig. 4. Flow chart of ERTCQD compensation algorithm

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Fig. 5. Network topology model of station bureau level

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Fig. 6. Node model of servers and clients

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Fig. 7. Queuing delay estimated by algorithm

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Fig. 8. Clock offset before and after compensation

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Fig. 9. Delay before and after compensation

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Fig. 10. Delay difference before and after compensation

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Table 1. Time delay of single link clock

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Table 1. Time delay of single link clock

Transmission path	Delay type
From master clock to router 1	Transmission delay
From router 1 to transmission link	Queuing delay
From transmission link to router 2	Propagation delay
From router 2 to transmission link	Queuing delay
From transmission link to slave clock	Propagation delay

Table 2. Algorithm performance
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Table 2. Algorithm performance
Algorithm Average queuing delay /ms Average error /ms Std
RTCQD 8.92 2.63 6.9
ERTCQD 8.20 0.22 5.8

Table 3. Meaning of statistics set in model

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Table 3. Meaning of statistics set in model

Statistic	Meaning
Q_ueue.r	Queuing delay in downlink
Q_ueue.f	Queuing delay in uplink
Delay	One way delay of link communication
ad.delay	One way delay after compensation
ad.offset	Clock offset after compensation
ntp.offset	Clock offset calculated in NTP
Offset	Standard clock offset

Table 4. Deviation error
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Table 4. Deviation error
Deviation error Maximum /ms Minimum /ms Average /ms
γ₁ 1.578 1.157 1.373
γ₂ 5.495 4.972 5.142

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Youpeng Zhang, Jianrong Cao, Li Lan. Delay Asymmetry Compensation Scheme of Railway Time Synchronization Network[J]. Laser & Optoelectronics Progress, 2021, 58(7): 0706003

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