In-Vehicle CAN Frames With MOD Timing for Large Data Packets
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Solution Overview
Problem
Existing CAN protocols in vehicles do not guarantee a delay between consecutive frames for large data packets, leading to potential delays in in-vehicle network communication as more features require larger data transmissions.
Innovation Solution
An improved CAN protocol that includes a medium occupancy duration (MOD) indicator in the frame, allowing nodes to reserve the network for a specified duration, preventing other nodes from transmitting until the transmission of large data packets is complete.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard CAN protocol arbitration is used for each frame, then nodes can transmit data packets, but delay between consecutive frames occurs due to repeated arbitration
Solution Approach 1:
The transmitting node performs preliminary action by calculating and embedding the medium occupancy duration (MOD) value in the first frame before transmission. This预先 calculation of transmission time allows receiving nodes to proactively reserve the bus for the entire packet duration, eliminating the need for repeated arbitration and reducing delays between consecutive frames.
2Adaptability or versatility
If nodes transmit large data packets with multiple frames, then more features can be provided, but network delay increases due to arbitration requirements
Solution Approach 1:
The MOD field acts as an intermediary mechanism that carries timing information between transmitting and receiving nodes. By embedding the medium occupancy duration in the first frame, it mediates the coordination between multiple nodes, allowing them to understand the complete transmission timeline and avoid conflicts, thus enabling large data packet transmission without excessive delays.
3Reliability
If arbitration is required for each frame transmission, then network access is controlled, but transmission delay increases for large data packets
Solution Approach 1:
The solution segments the large data packet into multiple frames while applying different arbitration rules to different frames. The first frame undergoes standard arbitration to ensure reliable network access control, while subsequent frames are transmitted without arbitration based on the预先 established MOD value. This segmentation approach maintains reliability for initial access while reducing delays for the bulk of data transmission.
Data Source
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AI summary
An apparatus for in-vehicle communication, the vehicle includes a memory device; and a first controller including the memory device, the first controller being operatively coupled to a plurality of vehicle controllers via an in-vehicle network, the first controller programmed to: transmit at least a first frame including a first field and a first data to at least a second controller of the plurality of vehicle controller via the in-vehicle network; determine a first duration indicative of a first amount of time to transmit at least the first frame to the second controller; position the first duration in the first field; and transmit at least the first frame including the first duration in the first field and the first data to provide an indication to the at least the second controller to avoid transmitting data on the in-vehicle network until the first amount of time has expired.