Correcting Time Synchronization Asymmetric Delay
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Solution Overview
Problem
Asymmetric delays on communication links reduce the accuracy of time synchronization protocols, such as IEEE 1588, by assuming symmetric delays, leading to inaccuracies in clock offset calculations between devices.
Innovation Solution
Devices determine and incorporate the asymmetry in propagation delays between different portions of a communication link into clock offset calculations by exchanging timing packets and measuring transmit and receive times, using techniques like reversing transmission and reception lines and employing time domain reflectometry to measure asymmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time synchronization protocols assume symmetric delays on communication links, then clock offset calculations are simplified, but time synchronization accuracy deteriorates due to asymmetric propagation delays
Solution Approach 1:
The patent applies preliminary action by measuring and storing the asymmetry in propagation delays before performing clock offset calculations. The system characterizes the communication link's asymmetric delay properties in advance, then uses this pre-measured asymmetry information to correct subsequent time synchronization calculations, thereby improving accuracy without adding complexity to the main synchronization protocol
Solution Approach 2:
The patent introduces an intermediary correction mechanism that acts between the raw timing measurements and the final clock offset calculation. By inserting an asymmetry compensation step that uses pre-measured delay differences, the system mediates between the simplified symmetric assumption and the actual asymmetric reality, improving measurement precision while maintaining calculation simplicity
2Measurement precision
If time synchronization protocols account for asymmetric delays on communication links, then time synchronization accuracy is improved, but device complexity increases due to additional measurement and correction requirements
Solution Approach 1:
The patent reduces operational complexity by performing the complex asymmetry measurement and characterization in advance, during a setup or calibration phase. Once the asymmetry parameters are measured and stored, the actual time synchronization operations can proceed using these pre-computed correction factors, avoiding the need for complex real-time asymmetry analysis during each synchronization cycle
Solution Approach 2:
The patent transforms the complex problem of handling asymmetric delays by changing the approach from dynamically analyzing asymmetry during each synchronization transaction to using static pre-measured asymmetry parameters. This parameter transformation allows the system to account for asymmetry using simple lookup or application of fixed correction values, rather than complex real-time calculations
Data Source
AI summary
Techniques for correcting time synchronization inaccuracy caused by asymmetric delays on a communication link. Time synchronization according to the present techniques includes determining an asymmetry in a propagation delay on a communication link used by a first device and a second device to exchange timing information and incorporating the asymmetry into a determination of a clock offset between the first and second devices.