Network Slave Clock Correction via Master Pulses Without Query Traffic
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Solution Overview
Problem
Existing Ethernet devices under the Precision Time Protocol (PTP) require frequent time query messages to a master node, increasing network traffic and inefficiency in time-of-day and frequency corrections.
Innovation Solution
Ethernet nodes correct their time-of-day and frequency using internal clock signals and a 'pulse-per-second' signal from a master node, eliminating the need for external clock signals and reducing network traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If slave nodes periodically query master node for time correction using PTP protocol, then time synchronization accuracy is maintained, but network traffic increases and system efficiency decreases
Solution Approach 1:
The slave node performs self-correction of its time-of-day clock by comparing its own pulse signal edges with received master pulse signal edges, and self-correction of its clock frequency by measuring interval differences. This eliminates the need for continuous query-reply message exchanges with the master node, reducing network traffic while maintaining synchronization accuracy.
Solution Approach 2:
The slave node continuously monitors and measures the time difference and frequency deviation between its local clock and the master clock using pulse signal edges, preparing correction values in advance. When correction is needed, the slave node applies these pre-calculated corrections without requiring real-time communication with the master node, thereby reducing network overhead.
2Measurement precision
If slave nodes use external clock signals from master node for correction, then synchronization accuracy is achieved, but device complexity and external dependencies increase
Solution Approach 1:
The slave node uses its own internal pulse signal and time-of-day counter, combined with received master pulse signals, to perform self-correction of both time-of-day and frequency. The correction logic is implemented within the slave node using its existing hardware resources, eliminating the need for additional external clock signal inputs and reducing device complexity.
Solution Approach 2:
The slave node's existing pulse signal generator and time-of-day counter, originally designed for basic timekeeping, are made multi-functional by using them for both time measurement and frequency correction. This eliminates the need for separate external clock signal paths and simplifies the overall system architecture.
Data Source
AI summary
In a network having at least one slave node including a slave clock, a method of adjusting the slave clock relative to a master clock of a master node includes, at the slave node, correcting a time of day of the slave clock using (a) a slave pulse signal having a known slave pulse rate, (b) a time-of-day counter of the slave node, and (c) a master pulse signal, based on values of the slave clock at nearest corresponding edges of the slave pulse signal and the master pulse signal, and correcting a frequency of the slave clock using the slave pulse signal, a clock signal of the slave node, and the master pulse signal, based on values of the slave clock at nearest corresponding edges of the master pulse signal. No other clock signal from outside the slave node is used for the corrections.