In-Vehicle CAN Frames With Medium Occupancy Reservation
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Solution Overview
Problem
Existing CAN protocols in vehicles do not guarantee 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 to reserve network use, allowing nodes to avoid transmitting until the indicated duration has expired, ensuring consecutive frame transmission without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If standard CAN protocol is used for transmitting large data packets, then nodes can transmit data independently, but delay between consecutive frames is not guaranteed due to repeated arbitration requirements
Solution Approach 1:
The patent applies preliminary action by calculating and inserting the medium occupancy duration (MOD) value into the frame header before transmission. This pre-calculated duration indicates the total time needed to transmit all consecutive frames, allowing receiving nodes to reserve the medium in advance and avoid arbitration delays between frames.
Solution Approach 2:
The MOD field acts as an intermediary mechanism that mediates between transmitting and receiving nodes. By providing this duration indicator, the protocol enables receiving nodes to automatically manage medium access without requiring repeated arbitration, thus reducing delay while maintaining protocol simplicity.
2Productivity
If nodes transmit data independently without coordination, then transmission flexibility is maintained, but network efficiency decreases due to arbitration overhead for each frame
Solution Approach 1:
The transmitting node performs preliminary calculation of the total transmission duration and embeds this information (MOD field) in the frame header. This allows receiving nodes to proactively reserve the medium for the indicated duration, eliminating arbitration overhead and improving network efficiency while nodes maintain operational independence.
Solution Approach 2:
The MOD field provides feedback information to receiving nodes about the required medium occupancy time. This feedback mechanism enables receiving nodes to adjust their transmission behavior accordingly, improving overall network efficiency without compromising the independence of individual node operations.
3Reliability
If arbitration is required before each frame transmission, then collision avoidance is ensured, but transmission delay increases for large data packets
Solution Approach 1:
The patent applies preliminary action by calculating the total medium occupancy duration before transmission and embedding it in the MOD field. Receiving nodes use this pre-provided information to reserve the medium in advance, ensuring collision avoidance without requiring arbitration before each frame, thus reducing transmission delay while maintaining reliability.
Data Source
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.