CAN Bus Arbitration Layer Segmentation for Throughput

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Solution Overview

Problem

Conventional CAN communication systems are limited by synchronization requirements and bidirectional message exchange during the acknowledge and arbitration processes, restricting data rate and throughput.

Innovation Solution

Arbitration decisions are made in a higher protocol layer, allowing CAN messages to be sent with a dominant level in the ACK field by the transmitting node, and preventing receiving nodes from sending a dominant level or error frame, enabling unidirectional message transmission and increasing data rate without additional costs or compatibility issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bidirectional message exchange is used during acknowledge and arbitration processes to ensure protocol compliance, then reliability of CAN communication is improved, but data rate is reduced due to synchronization delays

Engineering Contradiction:

Improveprotocol complianceVSAvoiddata rate

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent segments the communication protocol into two distinct layers: a higher protocol layer that performs arbitration decisions, and the CAN protocol layer that handles message transmission. This segmentation allows the CAN layer to operate in a simplified unidirectional mode without bidirectional acknowledge exchanges, thereby increasing data rate while maintaining reliability through the higher layer's arbitration mechanism.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements preliminary arbitration decisions in the higher protocol layer before CAN message transmission occurs. By pre-determining which nodes are authorized to send messages and configuring the ACK field accordingly, the system eliminates the need for time-critical bidirectional exchanges during the acknowledge phase, thus improving data rate while preserving protocol compliance.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If synchronization of all CAN communication nodes to a fraction of one bit cell duration is implemented to meet protocol requirements, then reliability of message transmission is improved, but loss of time increases due to synchronization delays

Engineering Contradiction:

Improvemessage transmission accuracyVSAvoidsynchronization delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent extracts the time-critical synchronization and arbitration functions from the CAN protocol layer and relocates them to a higher protocol layer. This extraction allows the CAN message transmission to proceed without repeated synchronization delays, as the higher layer handles arbitration decisions in advance, thereby reducing time loss while maintaining transmission accuracy.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If arbitration decisions are made at the CAN protocol layer with bidirectional acknowledge exchanges, then protocol compliance is ensured, but device complexity increases due to simultaneous actions requirements

Engineering Contradiction:

Improveprotocol complianceVSAvoidsynchronization coordination

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the arbitration function from the CAN protocol layer and assigns it to a higher protocol layer. This segmentation simplifies the CAN controller's task to unidirectional message transmission with pre-configured ACK fields, eliminating the need for complex simultaneous bidirectional actions and reducing device complexity while maintaining protocol compliance through the higher layer's arbitration logic.

Inventive Principle:

Principle #1Segmentation

4Productivity

If unidirectional message transmission is implemented by preventing receiving nodes from sending dominant levels or error frames, then productivity of data transmission is improved, but reliability of error detection may be affected

Engineering Contradiction:

Improvedata throughputVSAvoiderror detection

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements preliminary error detection mechanisms in the higher protocol layer and configures the ACK field in advance to reflect the transmitting node's state. By pre-configuring the ACK field and performing arbitration decisions before transmission, the system achieves unidirectional high-speed transmission while maintaining reliability through preliminary error detection and validation in the higher layer.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7860984B2Method and device for the creation of a communication system based on CAN communication controllers featuring an increased data throughput

Publication Date: 2010.12.28 TTTECH COMPUTERTECHNIK AG

AI summary

Disclosed is a method for transmitting CAN messages via a CAN bus in a communication system including several network nodes with at least one respective CAN controller. According to the method, the authorization of a network mode to send a CAN message is arbitrated, an arbitration decision being made in a higher protocol layer than the transmission of the CAN message, and the CAN message is already sent by the transmitting network node, the latter providing a dominant level in the ACK field of the message. A network node which receives the CAN message does not generate a dominant level in the ACK field and does not send a complete error frame.