Vehicle Clock Synchronization Using Silent Heartbeat Messages
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Solution Overview
Problem
Vehicular communication networks face challenges in clock synchronization due to clock drifts in GNSS receivers, which are exacerbated by atmospheric conditions, leading to desynchronization and inconsistencies in time-sensitive networking applications.
Innovation Solution
The implementation of silent clock synchronization using heartbeat messages exchanged between vehicles, where the processor updates clock offsets and determines location by comparing distances and velocities, allowing for iterative synchronization without additional message exchange, leveraging trilateration and machine learning for accurate clock and location determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GNSS receiver clocks are used for synchronization, then clock synchronization is achieved, but clock drift and atmospheric conditions cause desynchronization
Solution Approach 1:
The system implements feedback by having vehicles continuously exchange heartbeat messages containing timestamp and location information. Each vehicle measures the time difference between sending and receiving messages, calculates clock offsets, and adjusts its local clock accordingly. This closed-loop feedback mechanism compensates for clock drift and atmospheric effects, resolving the contradiction between achieving synchronization precision and maintaining reliability under varying conditions.
Solution Approach 2:
The synchronization system is self-service in that each vehicle independently determines its own clock offset by processing received heartbeat messages from neighboring vehicles. No central authority or additional synchronization infrastructure is needed; each vehicle uses the exchanged messages to autonomously calculate and adjust its clock, making the system reliable even when GNSS signals are degraded by atmospheric conditions.
2Measurement precision
If additional synchronization messages are exchanged, then synchronization accuracy is improved, but network traffic increases and interference is exacerbated
Solution Approach 1:
The invention merges the clock synchronization function with the existing periodic heartbeat messages already exchanged for presence detection and basic communication. By embedding timestamp and location information in these routine heartbeat messages, the system achieves synchronization without requiring separate dedicated synchronization message exchanges, thus improving accuracy while avoiding increased network traffic volume.
Solution Approach 2:
The heartbeat messages serve multiple functions simultaneously: presence detection, basic communication status indication, and clock synchronization reference. This multi-functionality allows the system to achieve synchronization accuracy using existing communication infrastructure, eliminating the need for additional dedicated synchronization traffic and reducing overall network interference.
3Measurement precision
If trilateration is used for location determination, then location accuracy is improved, but computational complexity increases
Solution Approach 1:
The system performs preliminary action by having vehicles pre-calculate and include their location information in heartbeat messages before synchronization is needed. When synchronization occurs, vehicles already possess location data from previous measurements, reducing the real-time computational burden. The trilateration calculation uses these pre-prepared location references along with timestamp differences, achieving location accuracy while minimizing instantaneous computational complexity.
Data Source
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AI summary
A vehicle includes a controller to control an operation of at least one component of the vehicle, a clock to synchronize the operation of the component of the vehicle, a memory to store a clock offset to the clock of the vehicle to synchronize the operation of the component of the vehicle, and a receiver to receive a set of heartbeat messages from a set of neighboring vehicles, each heartbeat message received from a neighboring vehicle includes a time of transmission of the heartbeat message, a location of the neighboring vehicle and a velocity of the neighboring vehicle. The receiver receives each heartbeat message at a corresponding receipt time measured using the clock of the vehicle. The vehicle also includes a processor to update the clock offset stored in the memory in response to determining concurrently an unknown clock offset and an unknown location of the vehicle at a particular time by comparing distances traveled by light between the times of the transmission of the heartbeat messages and corresponding receipt times adjusted with the unknown clock offset with distances between the vehicle at the unknown location and the locations of the neighboring vehicles retrieved from the heartbeat messages.