CAN Bus CRC Adaptation for Variable Error Detection
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Solution Overview
Problem
Current CAN bus systems face limitations in data transmission volume and security, particularly with increasing demands in modern vehicles, as they are optimized for short messages under real-time conditions and lack flexibility in adapting to varying data security requirements.
Innovation Solution
A method that modifies the polynomial used for calculating checksums in CAN bus systems, allowing the CRC field to vary in size based on a switching condition, enabling flexible data transmission security and increased data volume by using multiple generator polynomials and adapting the data length code, while maintaining compatibility with standard CAN systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CAN bus system uses standard fixed-size CRC fields and data structures, then compatibility with existing systems is maintained, but data transmission security and flexibility are limited
Solution Approach 1:
The patent implements dynamic adaptability by allowing the CRC field size to vary based on message priority and type. High-priority safety-critical messages use larger CRC fields (e.g., 32-bit) for enhanced error detection, while standard messages use the conventional 15-bit CRC. This dynamic configuration enables the system to adapt security levels to actual transmission needs, resolving the contradiction between maintaining standard compatibility and providing flexible security adaptation.
Solution Approach 2:
The invention changes the parameter of CRC field size from a fixed value to a variable parameter that can be adjusted according to message requirements. By modifying the CRC polynomial degree and field size based on message priority indicators, the system achieves both standard compatibility (using 15-bit CRC for normal messages) and enhanced security (using larger CRC fields for critical messages), thereby resolving the technical contradiction.
2Productivity
If larger data fields are used to increase data transmission volume, then the data transmission rate improves, but the complexity of the communication controller increases
Solution Approach 1:
The patent segments the data transmission into two phases: a standard arbitration phase using conventional CAN protocols with fixed timing, and a data phase where bit timing can be accelerated. This segmentation allows the controller to maintain compatibility with standard CAN controllers during arbitration while enabling higher transmission rates during data transfer, thus improving productivity without proportionally increasing device complexity.
Solution Approach 2:
The communication controller is designed with multi-functionality to operate in both standard CAN mode and extended high-speed mode. By integrating both standard 15-bit CRC handling and extended CRC capabilities, along with support for variable data field sizes, the controller serves multiple functions without requiring completely separate hardware, thereby achieving higher data transmission rates while limiting the increase in device complexity.
3Reliability
If the CRC field size is increased to enhance error detection capability, then data transmission security improves, but the data transmission time increases
Solution Approach 1:
The patent applies dynamic configuration where the CRC field size is adjusted based on message priority and type. Safety-critical messages with high priority use larger CRC fields (e.g., 32-bit or 64-bit) to maximize error detection capability, while non-critical messages use the standard 15-bit CRC to minimize transmission time. This dynamic adaptation resolves the contradiction by matching error detection effort to actual security needs.
Solution Approach 2:
The invention applies local quality enhancement by providing enhanced error detection (larger CRC fields) only where needed - specifically for high-priority safety-critical messages - while using standard error detection for routine messages. This localized approach to quality enhancement improves reliability for critical functions without unnecessarily increasing transmission time for all messages, thereby resolving the technical contradiction.
Data Source
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AI summary
The invention describes a method for serially transmitting data in a bus system having at least two participating data processing units, wherein the data processing units interchange messages via the bus, wherein the transmitted messages have a logical structure according to the CAN standard ISO 11898-1, wherein the logical structure comprises a start-of-frame bit, an arbitration field, a control field, a data field, a CRC field, an acknowledge field and an end-of-frame sequence, wherein the control field comprises a data length code containing an item of information relating to the length of the data field. The CRC field of the messages may have at least two different numbers of bits depending on the value of an associated changeover condition (UB3).