Packet Selection for IEEE 1588 Clock Synchronization
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Solution Overview
Problem
Packet delay variation (PDV) significantly affects the accuracy and stability of clock synchronization in IEEE 1588 Precision Time Protocol (PTP) networks, leading to clock noise and impairing the quality of synchronized clocks, especially in end-to-end timing transfer scenarios where intermediate network devices introduce variable delays.
Innovation Solution
A packet selection technique that identifies and selects packets with minimal PDV by determining optimal inter-arrival times, using methods like the Mean of Inter-Arrival Times (MNIAT) and Median of Inter-Arrival Times (MDIAT) algorithms, to minimize noise and maintain consistent packet spacing, thereby reducing PDV-induced noise in the recovered clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If packet selection is performed to reduce PDV, then clock synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary classification of packets into different delay categories (e.g., low delay, medium delay, high delay) before clock recovery. By pre-categorizing packets based on their delay characteristics, the system simplifies the subsequent selection process and reduces computational complexity while maintaining synchronization accuracy.
Solution Approach 2:
The patent segments the packet stream into multiple groups based on delay characteristics and uses different processing strategies for each group. This segmentation allows the system to handle packets with different delay profiles separately, reducing the overall complexity of the packet selection algorithm while improving clock synchronization accuracy.
2Reliability
If packet selection algorithm is made more sophisticated to reduce PDV, then clock noise is reduced, but processing time increases
Solution Approach 1:
The patent applies partial packet selection by processing only a subset of packets (e.g., selecting packets from specific delay categories) rather than analyzing all incoming packets. This partial action approach reduces processing time while still achieving sufficient PDV mitigation and maintaining clock quality within acceptable limits.
Solution Approach 2:
By performing preliminary classification of packets into delay categories before the selection process, the system reduces the computational burden during real-time processing. This preliminary organization allows for faster selection operations while maintaining reliable clock recovery performance.
3Productivity
If all received packets are used for synchronization, then productivity is maintained, but clock synchronization accuracy deteriorates due to PDV
Solution Approach 1:
The patent performs preliminary classification of packets into different delay categories before synchronization processing. This pre-organization allows the system to efficiently select appropriate packets for synchronization without sacrificing processing speed, as the classification work is done in advance during packet reception.
Solution Approach 2:
By segmenting packets into delay-based groups and selecting from appropriate segments, the system maintains high productivity by processing packets in an organized manner while improving synchronization accuracy through selective use of low-PDV packets.
Data Source
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AI summary
This invention relates to packet selection techniques that can be used in conjunction with a clock recovery mechanism to mitigate the effects of packet delay variation on timing messages exchanged over a packet network, particularly when seeking to synchronize the time of a clock in a slave device to that of a master clock. The packet selection techniques can assist in reducing the noise in the recovered clock signal at the slave device, allowing recovery to a higher quality. Embodiments of the invention provide techniques based on extracting timing packets that create a constant interval between the arrival of selected packets at the slave device and on extracting timing packets which are closest to making the interval between arrival of the selected packets equal to the interval between the departure of the packets.