AFDX Switch Synchronization via Fixed Delay Frames
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Solution Overview
Problem
Existing solutions for synchronizing equipment items in AFDX or Ethernet communication networks require either a dedicated link or complex protocols, leading to increased costs and complexity, and do not ensure a constant delay in synchronization frame transmission.
Innovation Solution
A method that involves receiving synchronization frames from a reference equipment item, delaying their transmission by a fixed average time through switches, allowing local clocks to synchronize based on the emission time, reception time, and propagation delay without requiring additional links or frame modification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated link is used for time-stamping messages (IRIG protocol), then synchronization precision is improved, but device complexity and cost increase due to supplementary link requirements
Solution Approach 1:
The patent merges the data communication path and synchronization message path into a single Ethernet network infrastructure. Synchronization frames are transmitted through the same switches and links used for data traffic, eliminating the need for separate dedicated time-stamping links while maintaining synchronization precision through controlled frame transmission delays.
Solution Approach 2:
The Ethernet network infrastructure is made multi-functional by enabling it to simultaneously handle both data communication and synchronization message transmission. The switches are configured to prioritize and control synchronization frame transmission, allowing the same physical infrastructure to serve dual purposes without compromising performance.
2Measurement precision
If IEEE Standard 1588 is used for synchronization, then synchronization performance is improved, but ease of operation deteriorates due to complex switch requirements and autonomous frame generation capabilities
Solution Approach 1:
Instead of requiring switches to autonomously generate synchronization frames as in IEEE 1588, the reference equipment item generates the synchronization frames and transmits them through the network switches. The switches simply forward these frames with controlled delays, eliminating the need for complex switch-based frame generation while maintaining synchronization accuracy.
Solution Approach 2:
The reference equipment item performs the function of generating and transmitting synchronization frames, making the system self-sufficient without requiring sophisticated switch capabilities. Each equipment item synchronizes itself using the transmitted frames and its local clock, simplifying the overall system operation.
3Device complexity
If synchronization frames are transmitted through switches with variable delays, then device complexity is reduced, but measurement precision deteriorates due to non-constant transmission delays
Solution Approach 1:
The system pre-calculates and compensates for transmission delays through the switches. By measuring or estimating the delay introduced by switch buffering and forwarding, the reference equipment item adjusts the transmission timing of synchronization frames to compensate for these delays, ensuring that equipment items receive frames at consistent intervals despite variable switch processing times.
Data Source
AI summary
The invention has in particular as an object the synchronization of a local clock of an equipment item in a communication network according to synchronization frames emitted by a reference equipment item and transmitted via a switch. After it has received (700) a synchronization frame emitted by the reference equipment item and including its time point of emission, the switch transmits (730) the said received synchronization frame after a delay that is fixed, at least on average, counting from the reception of the said synchronization frame by the said switch (725). The local clock of the equipment item, after reception of the said synchronization frame by the equipment item, is synchronized according to the said time point of emission, to the time point of reception of the said synchronization frame and to the said delay.