Distributor Unit for Time-Triggered Message Scheduling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing distributed real-time systems face challenges in efficiently integrating time-triggered messages into event-controlled message distribution units, particularly in non-time-critical communication systems like Ethernet, where event-driven approaches dominate, and modifying existing Ethernet message distribution units to handle time-triggered messages is costly due to ASIC changes.
Innovation Solution
A method involving a distribution unit with a low-level switching unit (LLVME) having access to a global time base, distinguishing between event-triggered and time-triggered messages, and a high-level switching unit (HLVME) that analyzes and schedules ET messages, while ensuring TT messages are transmitted at predetermined times by using a pause frame to prevent ET message scheduling conflicts, thus expanding existing Ethernet message distribution units to handle time-triggered messages without altering the existing units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing Ethernet message distribution units are modified to handle time-triggered messages, then functionality is improved, but manufacturing cost increases due to ASIC changes
Solution Approach 1:
The system is divided into two functional layers: a time-triggered message handling layer (LLVME) and an event-triggered message handling layer (HLVME). The LLVME handles time-critical messages with deterministic timing, while the HLVME handles event-driven messages. This segmentation allows existing Ethernet infrastructure to continue operating without modification while adding time-triggered capability through a separate layer, avoiding expensive ASIC changes.
Solution Approach 2:
The LLVME acts as an intermediary between time-triggered message sources and the existing Ethernet network. It intercepts time-triggered messages, schedules them according to predetermined time slots, and forwards them to the HLVME for transmission over the Ethernet network. This intermediary approach enables time-triggered messaging without requiring modifications to the core Ethernet infrastructure or existing message distribution units.
2Measurement precision
If time-triggered messages are integrated into event-controlled systems, then timing precision is improved, but system complexity increases
Solution Approach 1:
The LLVME autonomously handles time-triggered message scheduling and transmission without requiring complex coordination with the event-driven HLVME. It maintains its own schedule of predetermined time slots and independently manages time-critical message flow. This self-service approach isolates the time-triggered subsystem, allowing it to operate with high timing precision without imposing complex synchronization requirements on the overall system.
Solution Approach 2:
Time-triggered messages are scheduled in advance according to a predetermined schedule stored in the LLVME. The system performs preliminary scheduling of message transmission times before actual message generation occurs. This preliminary action eliminates the need for complex real-time arbitration and scheduling algorithms, simplifying the system while ensuring deterministic timing precision.
3Productivity
If event-triggered messages are allowed during time-triggered transmission slots, then communication efficiency is improved, but timing reliability deteriorates
Solution Approach 1:
The LLVME sends pause frames to the HLVME in advance of scheduled time-triggered message transmissions. These pause frames preemptively prevent the HLVME from scheduling or transmitting event-triggered messages during time slots reserved for time-triggered communications. By applying this preliminary anti-action, the system guarantees timing reliability for critical messages while still allowing efficient event-driven communication during non-reserved slots.
Data Source
Figure 1~2
AI summary
The invention relates to a method for distributing event-triggered (ET) and time-triggered (TT) communications in a distributed real-time system by means of a distributor unit that comprises a low-level relay unit (LLVME) and a high-level relay unit (HLVME), distributor unit communication ports to other relay units and/or end systems of the real-time system being attached to said LLVME. The invention also relates to such a distributor unit and to a real-time system comprising at least one such distributor unit. According to the invention, the LLVME has access to a global time base and is configured to differentiate between ET communications and TT communications, the LLVME forwarding an ET communication that is incoming to one of its ports to the HLVME such that said HLVME can carry out the analysis and temporal scheduling of said ET communication before it delivers this ET communication back to the LLVME for it to be issued at the designated output port of the LLVME, and, prior to the known issuing of a TT communication, said LLVME transmitting a pause-frame to the HLVME such that no ET communication is scheduled to be transmitted by the HLVME during this anticipated and scheduled TT communication transmission slot, and the LLVME delivers an incoming TT communication directly for issue at the designated output port in accordance with the known time plan.