Incremental Scheduling for TTEthernet Networks
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Solution Overview
Problem
Existing time-triggered computer networks face challenges in dynamically adding new scheduled messages without disrupting the real-time properties of existing messages, especially in large or dynamic networks where global schedule approaches are not feasible.
Innovation Solution
A method is introduced to add new time-triggered flows by determining free transmission gaps in the transmission cycle, modifying existing cycles iteratively by shifting transmission windows, and extending the consideration set if necessary, to ensure the new flow's window is placed without overlapping with existing flows, thus preserving the real-time properties of both old and new messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a global schedule approach is used to manage time-triggered message transmissions, then the real-time properties of existing messages are preserved, but the ability to dynamically add new scheduled messages is limited
Solution Approach 1:
The global transmission schedule is segmented into individual transmission cycles for each network component (nodes and star couplers). Each component maintains its own local transmission cycle with transmission windows for different flows, allowing independent modification of local schedules without affecting the entire global schedule. This segmentation enables dynamic addition of new messages at the local level while preserving global real-time properties.
Solution Approach 2:
The system transitions from a static global schedule to a dynamic incremental scheduling approach. New time-triggered flows can be dynamically added by determining their transmission windows and iteratively modifying the transmission cycles of affected network components. The scheduling system continuously adapts to accommodate new messages while maintaining the real-time properties of existing messages through localized schedule adjustments.
2Ease of operation
If the transmission schedule is statically defined and calculated once, then the network operation is simple and predictable, but the network cannot adapt to dynamic additions of new flows
Solution Approach 1:
The system combines static baseline schedules with dynamic incremental modifications. Initial transmission cycles are statically defined for simplicity, but the system enables dynamic addition of new flows by iteratively determining transmission windows and adjusting affected local schedules. This allows the network to maintain operational simplicity while adapting to dynamic requirements.
Solution Approach 2:
Transmission windows for new flows are determined in advance by analyzing the transmission cycles of affected network components. The system performs preliminary calculations to identify suitable time slots and iteratively adjusts schedules before implementing new flows, ensuring that dynamic additions do not disrupt existing real-time properties while maintaining predictable operation.
3Reliability
If transmission windows for new flows are added without modifying existing cycles, then existing message transmissions remain unchanged, but sufficient transmission gaps may not be available for new flows
Solution Approach 1:
The system dynamically adjusts transmission cycles by iteratively shifting transmission windows of existing flows to create sufficient gaps for new flows. When adding a new time-triggered flow, the system modifies the transmission cycles of affected network components by moving existing transmission windows in time, thereby creating the necessary space while preserving the real-time properties of existing messages through controlled, incremental changes.
Solution Approach 2:
The iterative modification process acts as an intermediary mechanism between the requirement for new transmission gaps and the constraint of preserving existing message transmissions. By systematically shifting transmission windows and recalculating schedules, the system mediates between these conflicting requirements to achieve a valid schedule that accommodates new flows while maintaining existing real-time properties.
Data Source
AI summary
A method for transmitting messages in a computer network, e.g., a TTEthernet network, the network including nodes and at least one star coupler, which are connected in a multi-hop fashion, the nodes periodically exchanging time-triggered (TT) messages according to a pre-defined transmission schedule, and wherein nodes exchange, according to the schedule, messages via scheduled time-triggered flows, wherein adding a new time-triggered flow into the running computer network includes: 1. determining, for each hop in the new flow path of the new time-triggered flow, a free transmission gap in the transmission cycle of the corresponding port, 2. modifying, if a sufficiently long transmission gap is not free in a transmission cycle, said transmission cycle, wherein 3. modifying transmission cycles occurs iteratively, and 4. if a sufficient transmission gap is found in each transmission cycle along the flow path, the new transmission is incorporated into each of the cycles and executed periodically.