Periodic Message Scheduling for Vehicle Bus Load Balancing
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Solution Overview
Problem
Scheduling periodic messages in vehicle communication systems can lead to CPU throughput spikes and communication busload bursts due to multiple messages with shared or multiple periodicities being transmitted simultaneously, causing operating system task overruns and unexpected delays.
Innovation Solution
A processor-based system that schedules periodic message transmission on a communication bus by sorting messages by increasing periodicities, assigning start-up delays, and generating a transmission schedule based on these delays and periodicities, ensuring efficient transmission during time ticks and balancing bus load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If periodic messages are scheduled for transmission based on their periodicity, then message transmission timing is simplified, but CPU throughput spikes and communication busload bursts occur
Solution Approach 1:
The system performs preliminary action by pre-calculating and storing start-up delays for each periodic message during system initialization. This allows the scheduler to avoid CPU throughput spikes by having advance knowledge of when messages should be transmitted, preventing busload bursts before they occur.
Solution Approach 2:
The scheduling system introduces dynamic adjustment through start-up delays that vary for different messages. Instead of uniform periodic transmission, the system dynamically adjusts transmission timing based on message-specific parameters, smoothing out CPU throughput and busload patterns while maintaining periodicity.
2Device complexity
If multiple periodic messages with shared or multiple periodicities are transmitted simultaneously, then transmission scheduling is simplified, but communication busload bursts and transmission delays occur
Solution Approach 1:
The system segments the message transmission process by introducing start-up delays that distribute messages across different time windows. This segmentation prevents simultaneous transmission of multiple periodic messages, reducing busload bursts and transmission delays while maintaining manageable scheduling complexity.
Solution Approach 2:
The scheduler performs preliminary calculation of start-up delays during initialization, storing this information for use during runtime. This preliminary action eliminates the need for complex real-time calculations, reducing scheduling complexity while preventing transmission delays by having pre-computed timing information.
3Reliability
If start-up delays are assigned to periodic messages, then CPU throughput spikes are reduced, but transmission timing precision requirements increase
Solution Approach 1:
The system performs preliminary calculation of start-up delays during initialization, storing these values for use during runtime transmission. This preliminary action reduces the computational burden during execution and simplifies timing implementation, achieving CPU throughput stabilization without proportionally increasing runtime precision requirements.
Solution Approach 2:
The system changes the timing parameters by introducing variable start-up delays for different periodic messages. This parameter change smooths CPU throughput patterns while the delays are calculated based on message periodicities, maintaining timing precision through mathematical relationships between parameters rather than requiring arbitrary high-precision values.
Data Source
AI summary
Methods and apparatus are provided for periodic message transmission. Transmission of messages by the apparatus onto a communication bus are enabled during time ticks. The time ticks are separated by tick time intervals. A plurality of periodic messages configured to be transmitted on the communication bus are identified. Each periodic message has a periodicity that is a multiple of the tick time interval. The periodic messages are sorted by increasing periodicities to generate a sequence of periodic messages. A zero-start-up delay is assigned to a first periodic message in the sequence. A start-up delay is generated for each periodic message in the sequence based on a previous start-up delay associated with a previous periodic message, the tick time interval, and a periodicity of that periodic message. A transmission schedule is generated for the periodic messages based on the start-up delay and the periodicity associated with each of the periodic messages.