Time Synchronization via Separate Unidirectional Wireless Channel
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Solution Overview
Problem
Current wireless communication systems, such as Wi-Fi, are not optimally suited for highly accurate time synchronization required in industrial applications, particularly in real-time communication systems like TSN and PROFINET, due to inherent latency and jitter issues, and existing solutions like NTP and time propagation methods incur additional delays and security vulnerabilities.
Innovation Solution
A separate, unidirectional wireless channel using simple radio systems in license-free frequency bands is employed for time synchronization, transmitting synchronization signals as pulses or short telegrams, which are initiated by a hardware unit with a high-precision clock, and corrected for propagation delays to ensure precise timing without additional latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate unidirectional wireless channel is used for time synchronization, then time synchronization precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the wireless communication system into two separate channels: a first wireless channel for data transmission and a second unidirectional wireless channel for time synchronization. This segmentation allows each channel to be optimized for its specific function, with the synchronization channel using simple pulse transmission without the complexity of bidirectional protocols, thereby achieving high precision while managing device complexity through functional separation.
2Ease of operation
If time synchronization functions are implemented in software, then ease of operation is improved, but measurement precision deteriorates due to unpredictable duration and jitter
Solution Approach 1:
The patent introduces a dedicated hardware time synchronization unit that acts as an intermediary between the wireless receiver and the system clock. This hardware unit directly processes synchronization pulses from the second wireless channel and adjusts the system clock without software intervention, eliminating the jitter and unpredictable duration associated with software implementations while maintaining operational simplicity through automated hardware-based time adjustment.
3Ease of operation
If NTP protocol is used for time synchronization, then ease of operation is improved, but reliability deteriorates due to security vulnerabilities and additional delays
Solution Approach 1:
The patent extracts the time synchronization function from the data transmission channel and implements it through a separate, dedicated unidirectional wireless channel using simple pulse transmission. This eliminates the need for complex NTP protocols and their associated security vulnerabilities and delays, while the hardware-based implementation ensures reliable and secure time synchronization without requiring sophisticated protocol handling.
Data Source
Figure 1
AI summary
For wireless communication in the industrial environment, there is, inter alia, an iWLAN protocol, which meets the requirements but provides no time synchronization in the data transmission. According to the invention, an additional - ideally wireless - channel is used for the synchronization. In an advantageous embodiment of the invention, a simple radio system is used for this. Pulses or telegrams for time synchronization are initiated directly from a unit, which is designed as hardware and which is responsible for the time synchronization and which has a highly accurate clock, or supplied on the side to be synchronized of such a unit. The radio system can be designed very simply and unidirectionally. The transmission process is started without delay in order to prevent variable delays.