Subscriber Station Scheduling Unit for Deterministic Bus Access
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current CAN-based bus systems cannot guarantee 100% deterministic bus access, which is essential for real-time critical applications, as they rely on arbitration methods that may lead to collisions and unpredictable message transmission times.
Innovation Solution
A subscriber station with a communication control device, transmitting/receiving device, and scheduling unit that allocates specific time slots for deterministic bus access, ensuring each station can transmit messages at a guaranteed time, using information from the bus system to manage and prioritize transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If arbitration method (CSMA/CR) is used for bus access, then device complexity is reduced and ease of operation is improved, but deterministic bus access cannot be guaranteed and message transmission time becomes unpredictable
Solution Approach 1:
The patent applies preliminary action by pre-allocating specific time slots to subscriber stations before actual message transmission. The scheduling unit determines in advance which time slots each station can use for transmission, eliminating the need for arbitration during actual message sending. This pre-planned allocation ensures deterministic bus access while maintaining operational simplicity.
2Reliability
If time slot allocation scheduling is implemented for deterministic bus access, then reliability of real-time communication is improved, but device complexity increases due to additional scheduling unit and control mechanisms
Solution Approach 1:
The scheduling unit is designed to perform multiple functions: it determines time slot allocation, manages transmission scheduling, and ensures deterministic access for all subscriber stations. By consolidating these control functions into a single multi-functional unit, the patent reduces overall system complexity while maintaining deterministic bus access reliability.
3Speed
If strict priority scheduling via arbitration is used, then high priority messages are transmitted quickly, but maximum delays are reduced only partially and real-time critical applications cannot guarantee 100% deterministic access
Solution Approach 1:
The patent implements periodic action by organizing bus access into regular cycles with predetermined time slots for each subscriber station. This cyclic time-division multiplexing ensures that high-priority messages are transmitted at predictable intervals without arbitrary delays caused by arbitration. The periodic structure guarantees maximum delay bounds while maintaining transmission speed for critical applications.
Data Source
AI summary
A subscriber station for a serial bus system. The subscriber station has a communication control device for controlling a communication of the subscriber station with at least one other subscriber station of the bus system, a transmitting/receiving device for transmitting a transmission signal in a frame on a bus of the bus system, and a scheduling unit for scheduling a temporal access of the subscriber station to the bus in at least one time slot of a cycle of temporally consecutive time slots, at least one time slot being provided in a cycle for each subscriber station for transmitting its transmission signal and the cycle repeating cyclically. The scheduling unit is designed to determine an assignment that specifies which time slot of the cycle the transmitting/receiving device is allowed to use for transmitting the frame for the transmission signal on the bus.