V2X Time Offset Compensation for Accurate Moving-Vehicle Positioning
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Solution Overview
Problem
In vehicle-to-everything (V2X) communications, inaccurate time synchronization between vehicles and other entities leads to message rejection and incorrect scene interpretation, with a 1-second error causing a 30-meter position error, especially in moving vehicles.
Innovation Solution
A system that determines a time compensation offset for each sender's time stamps based on the difference between their time and the receiver's ego time, applying this offset to messages to ensure accurate timestamp alignment, and discards messages with time differences exceeding a threshold to prevent errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If V2X units synchronize time to GNSS or GPS time, then time synchronization is achieved, but position errors occur due to time offsets in moving vehicles
Solution Approach 1:
The patent replaces the traditional GNSS/GPS-based time synchronization mechanism with a peer-to-peer time offset measurement and compensation mechanism. Instead of relying on external satellite timing signals, vehicles directly measure time offsets between their own timestamps and received timestamps from other vehicles, then compensate for these offsets in scene interpretation. This substitution eliminates the accumulation of synchronization errors that occur in moving vehicles while maintaining accurate relative timing for safety-critical decisions.
2Productivity
If time synchronization is not accurate, then messages can be exchanged between V2X units, but messages are rejected and scene interpretation becomes impossible
Solution Approach 1:
The patent applies preliminary time offset compensation before message processing and scene interpretation. By measuring and storing time offsets from each sender in advance, and applying these offsets when processing received messages, the system ensures that timestamps are corrected to a common reference frame before being used for safety-critical decisions. This preliminary action prevents message rejection and enables reliable scene interpretation.
3Measurement precision
If a time offset of 1 second is present in a vehicle moving at 30 m/s, then time synchronization is maintained, but position error increases to 30 meters
Solution Approach 1:
The patent changes the reference frame parameter by applying time offset compensation specific to each sender. Instead of using a single global GNSS time reference that accumulates errors in moving vehicles, the system measures and applies individual time offsets for each communicating vehicle, transforming the timestamps to a consistent reference frame. This parameter change eliminates the 30-meter position error that would otherwise result from 1-second time offsets at 30 m/s.
Data Source
AI summary
The assumption that every participating vehicle control unit (VCU) or engine control unit (ECU) in a V2X network is synchronized to GNSS time or GPS time (or some other time base) is discarded. An error is assumed for every time entry. For all messages received from a dedicated communication node, a time compensation offset is determined.