Switch Device Time Correction Across Vehicle VLANs
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Solution Overview
Problem
Current on-vehicle network systems, particularly those using Ethernet connections, face challenges in time synchronization between devices belonging to different Virtual Local Area Networks (VLANs), as existing protocols like gPTP only facilitate synchronization within the same VLAN, compromising security and efficiency.
Innovation Solution
A switch device and on-vehicle communication system that calculates and transmits time correction information based on transmission and reception times across different VLANs, enabling devices to synchronize their times accurately through a relay unit, calculation unit, and notification unit, even when connected to different VLANs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing time synchronization protocols like gPTP are used within the same VLAN, then time synchronization is achieved, but time synchronization between different VLANs cannot be performed
Solution Approach 1:
The switch device acts as an intermediary between function units in different VLANs. It receives time stamp information from both VLANs, performs time correction calculations, and distributes corrected time information across VLAN boundaries, enabling synchronization without direct communication between VLANs.
Solution Approach 2:
The switch device performs multiple functions: it acts as a relay unit for data transmission, a calculation unit for time correction, and a notification unit for distributing time information. This multi-functionality allows it to bridge different VLANs while maintaining their security isolation.
2Reliability
If time correction information is calculated and transmitted across VLANs, then time synchronization is achieved, but communication complexity increases
Solution Approach 1:
The switch device integrates multiple functions into a single unit: relay unit for data transmission, calculation unit for time correction, and notification unit for distribution. This consolidation adds functionality without proportionally increasing complexity, as all functions are performed within the existing switch infrastructure.
Data Source
AI summary
This switch device includes: a relay unit configured to perform a first relay process of relaying data between function units installed in a vehicle and belonging to different VLANs; a calculation unit configured to calculate time correction information on the basis of a transmission time of data from a first function unit serving as the function unit to the switch device, a reception time in the switch device of the data transmitted from the first function unit, a transmission time of data from a second function unit serving as the function unit to the switch device, and a reception time in the switch device of the data transmitted from the second function unit; and a notification unit configured to notify the second function unit of the time correction information calculated by the calculation unit.