Clock Offset Estimation for Systems With Asymmetric Packet Delays

Youngmok Ha, Eunji Pak, Jongkil Park, Taeho Kim, Ji Won Yoon

Research output: Contribution to journalArticlepeer-review


This paper proposes a new clock offset estimation that mitigates unwanted link asymmetry for precise clock synchronization. The main contribution is to address the primary and traditional design issue of the IEEE 1588 standard precision time protocol (PTP), which estimates clock offset under the assumption that the delays of exchanged packets are symmetric. To mitigate the issue, we focus on the fact that PTP measures asymmetry variation through the derivatives of its timestamps with respect to the time step. By exploiting the measurement of the variation, the proposed approach defines the asymmetry in the form of a linear differential equation (LDE) and leverages the LDE to define and exclude asymmetry-induced errors. Additionally, we clearly derive the state transition of the asymmetry. Subsequently, we derive a novel state-space model from our approach. The model describes PTP clock offset estimation perfectly, allowing optimal clock offset estimation. We verify the theoretical validity of the proposed method with real data. Our approach improves PTP accuracy by more than thousand times and achieves an accuracy at the level of tens to hundreds of nanoseconds on an asymmetric communication link. Our approach realizes an accuracy comparable to that of PTPv2, without the cost of specialized hardware.

Original languageEnglish
Pages (from-to)1838-1853
Number of pages16
JournalIEEE/ACM Transactions on Networking
Issue number4
Publication statusPublished - 2023 Aug 1

Bibliographical note

Funding Information:
This work was supported by the Institute of Information & Communications Technology Planning & Evaluation (IITP) Grants funded by the Korea Government [Ministry of Science and Information and Communications Technology (MSIT)] (Safety-Critical Distributed Modular software (SW) Platform and Neuromorphic Computing Software Platform for Artificial Intelligence Systems) under Grant B0101-16-0663 and Grant 2022-0-00769. The authors would like to thank the anonymous reviewers, editors, and Dr. Jeman Park for their valuable comments and advice that have resulted in improvements of this work

Publisher Copyright:
© 2022 IEEE.


  • Clocks
  • Kalman filtering
  • State space model
  • precision time protocol
  • synchronization

ASJC Scopus subject areas

  • Software
  • Electrical and Electronic Engineering
  • Computer Networks and Communications
  • Computer Science Applications


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