TTEthernet Schedule Generation for Mixed Criticality Networks
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Solution Overview
Problem
In mixed-criticality networks, time-triggered (TT) messages with higher priority can adversely affect the timely behavior of rate-constrained (RC) messages, leading to violations of their real-time requirements due to scheduling interference.
Innovation Solution
A method is proposed to modify the transmission times of TT messages using an optimization function and SMT-solver, ensuring that RC messages meet their real-time requirements by evenly spacing out TT transmissions and using network calculus for feedback-based rescheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TT messages are transmitted with high priority to ensure their real-time delivery, then TT message delivery reliability is improved, but RC message latency increases due to scheduling interference
Solution Approach 1:
The patent modifies transmission parameters by adjusting the timing offsets of TT messages relative to the hyperperiod. By changing the phase relationships between different TT message flows, the system redistributes transmission opportunities to reduce contention on shared links, thereby decreasing RC message latency while preserving TT message delivery guarantees
Solution Approach 2:
The system dynamically adjusts transmission schedules based on calculated hyperperiod offsets. Rather than using fixed periodic transmission times, the offsets are computed to optimize the temporal distribution of TT messages across the network, creating a dynamic scheduling approach that minimizes interference with RC traffic
2Device complexity
If TT transmission times are concentrated to improve scheduling efficiency, then scheduling complexity is reduced, but network contention increases causing RC message deadline violations
Solution Approach 1:
The patent introduces a new dimension to scheduling by calculating offsets in the temporal domain relative to the hyperperiod. Instead of only considering periodic intervals, the system adds an offset dimension that shifts TT message transmission times, effectively distributing traffic across different time phases to reduce link contention while maintaining schedule manageability
3Loss of time
If TT messages are evenly spaced to reduce network contention, then RC message latency is reduced, but TT message scheduling complexity increases
Solution Approach 1:
The system performs preliminary calculation of hyperperiod offsets during the scheduling phase. By pre-computing the optimal temporal distribution of TT messages before actual transmission begins, the system establishes an optimized schedule that reduces RC latency without requiring complex real-time adjustments during operation
Solution Approach 2:
The scheduling mechanism uses feedback from network traffic patterns and deadline requirements to adjust TT message offsets. The system calculates optimal offsets based on observed contention points and RC message timing constraints, creating a feedback-driven scheduling approach that adapts to network conditions
Data Source
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AI summary
A method for generating a schedule for the transmission of time-triggered, TT, messages in a network, for example in a TTEthernet or TSN network, wherein the network comprises components, for example nodes and starcouplers, wherein components of said network communicate time-triggered messages according to said schedule and based on a global, network-wide time, and wherein said components communicate rate-constrained, RC messages, wherein for each of said RC messages real-time requirements are provided, wherein the method comprises the steps of - Step1: setting the transmission time of all TT messages which are communicated in the network, and - Step 2: executing a search function to find a set of TT transmission times so that the real-time requirements of all RC messages are fulfilled, and in case, that all real-time requirements or at least real-time requirements for defined RC messages are fulfilled, generating in a - Step 3: the schedule based on the transmission times retrieved in Step 2, - or executing Step 2 again in case that not all real-time requirements or not all real-time requirements for the defined RC messages are fulfilled.