In-Vehicle Network Time Synchronization via Priority Delay Measurement
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Solution Overview
Problem
In vehicle network systems, time synchronization accuracy is compromised when using a relative priority scheme due to varying communication delays, especially when intermediate nodes do not guarantee that higher priority messages are sent first, leading to unpredictable and potentially longer delays for high-priority messages.
Innovation Solution
A network system that includes a first and second device configured to manage time, with an intermediate node using a relative priority scheme to buffer and output messages, where communication delays are measured and a representative value is set to minimize delay distribution, allowing for accurate time synchronization by adjusting the time management units based on these measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a relative priority scheme is used in the intermediate node, then message processing flexibility is improved, but time synchronization accuracy deteriorates due to unpredictable communication delays
Solution Approach 1:
The patent segments messages into multiple priority levels (e.g., 8 priorities from highest to lowest) and measures communication delay for each priority level separately. This allows the system to handle different message types with appropriate delay expectations, improving time synchronization accuracy while maintaining the flexibility of relative priority schemes.
Solution Approach 2:
The patent changes the parameter of delay representation from a single value to multiple priority-specific delay values. By measuring and storing communication delays for each priority level individually, the system can select the appropriate delay value based on message priority, thereby improving synchronization accuracy without sacrificing the adaptability of relative priority scheduling.
2Speed
If the highest priority message is used for time synchronization, then minimum communication delay is expected, but delay distribution increases when relative priority scheme is used
Solution Approach 1:
The patent segments the delay measurement into multiple priority categories. Instead of relying solely on the highest priority message, it measures delay for each priority level and uses the priority corresponding to the synchronization message type. This reduces delay distribution by ensuring consistent priority handling for synchronization messages.
Solution Approach 2:
The patent implements a feedback mechanism where the system measures communication delay for each priority level, stores these measurements, and uses the appropriate measured delay value when calculating time offsets. This feedback loop ensures that the delay value used for synchronization reflects actual observed delays for that priority level, reducing variability.
Data Source
AI summary
An in-vehicle network system includes first device and second device configured to send or receive to or from each other, and an intermediate node connected between the first device and the second device, the intermediate node being configured to output buffered messages in a sequence determined by a relative priority scheme. The first device includes a control unit configured to measure a communication delay for each of a plurality of different priority messages, set a delay representative value less than a maximum value of the plurality of communication delays, and adjust time that a time management unit manages, based on time that the first device manages, time that the second device manages, and the delay representative value.