Hybrid Wired Wireless TSN Network Clock Drift Mitigation
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Solution Overview
Problem
Hybrid wired/wireless Time-Sensitive Networks (TSN) face performance degradations due to clock drift and clock jump, affecting time synchronization and quality of service scheduling, with existing solutions not adequately addressing these issues in industrial settings.
Innovation Solution
The approach involves creating separate subdomains within the network, assigning a hot-standby grandmaster to each subdomain, and coordinating TSN switches to manage clock drift and jump, ensuring reliable time synchronization and quality of service through the concept of independent subdomains and deferred scheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wireless links are used in TSN networks to increase flexibility and adaptability, then network versatility is improved, but time synchronization precision and QoS scheduling reliability deteriorate due to clock drift and clock jump
Solution Approach 1:
The network is divided into multiple subdomains, each with its own grandmaster clock. This segmentation isolates clock drift and jump issues to specific subdomains, preventing them from affecting the entire network. Wireless links can be used within subdomains while maintaining synchronization precision through localized time reference.
Solution Approach 2:
Grandmaster clocks act as intermediary time reference points between wireless links and the rest of the TSN network. The grandmaster provides a stable time reference that mediates the synchronization between wireless devices and wired network components, eliminating direct exposure to wireless-induced clock variations.
2Adaptability or versatility
If wireless links are used in TSN networks, then network adaptability is improved, but QoS scheduling reliability deteriorates due to clock jump
Solution Approach 1:
By segmenting the network into subdomains with local grandmasters, QoS scheduling reliability is maintained within each subdomain despite wireless link variations. The segmentation prevents clock jump propagation across the entire network, ensuring reliable scheduling in industrial control applications.
Solution Approach 2:
The system prepares for potential clock jump issues by establishing grandmaster clocks in advance within each subdomain. These pre-positioned time references provide a cushion against synchronization disruptions, ensuring QoS scheduling can continue reliably even when wireless links experience clock jumps.
3Device complexity
If a single grandmaster clock is used in the entire TSN network, then device complexity is reduced, but time synchronization reliability deteriorates in large-scale networks due to clock drift propagation
Solution Approach 1:
The synchronization architecture is segmented into multiple subdomains, each with its own grandmaster. This segmentation prevents clock drift from propagating across the entire network, maintaining synchronization reliability in large-scale deployments while distributing the complexity across manageable units rather than concentrating it in a single central grandmaster.
Solution Approach 2:
The system transitions from a single-dimensional hierarchical structure (one grandmaster at the top) to a multi-dimensional distributed structure with multiple grandmasters operating in parallel across different subdomains. This dimensional change allows the network to scale while maintaining reliability through spatial distribution of time reference functions.
Data Source
AI summary
A method for attenuating performance degradation of an IEEE 802.1 hybrid wired/wireless time sensitive network (TSN) in terms of time synchronization and quality of service (QOS) scheduling. The method makes it possible to attenuate the impact of clock drift on AS and the impact of clock jump on Qbv scheduling. The method comprises two mechanisms that consist (i) in grouping together the nodes of the network into subdomains and assigning a redundant grandmaster per subdomain; and (ii) in coordinating the TSN switches of a subdomain before applying corrected Qbv scheduling.