Extended CAN Bus Framing for IPv6 Data Without Segmentation

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Solution Overview

Problem

The existing CAN bus technology, including CAN FD, is inadequate for supporting IPv6 communication due to limitations in data packet size, increased susceptibility to errors, overhead issues, and latency problems, making it unsuitable for real-time applications and efficient data transmission.

Innovation Solution

The development of an extended CAN protocol (CAN EL) that expands the data field length, introduces an end field with an end-of-frame code, modifies bit stuffing rules, and adjusts identifier assignment to prioritize messages, enabling efficient transmission of large data packets and maintaining real-time capabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If CAN FD protocol is used to transmit IPv6 packets, then data transmission capability is improved, but packet size limitation and segmentation overhead worsen

Engineering Contradiction:

Improvedata transmission capabilityVSAvoidpacket segmentation complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the transmission protocol into distinct phases: arbitration phase for addressing and data phase for bulk data transfer. This allows the protocol to handle large IPv6 packets efficiently by separating control functions from data transmission functions, avoiding the need for multiple segmentation operations while supporting packets up to 64 bytes in a single transmission frame.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If ISO TP transport protocol is used for IPv6 transmission, then data transmission is enabled, but latency increases due to stateful connections

Engineering Contradiction:

ImproveIPv6 transmission capabilityVSAvoidtransmission latency

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent extracts the stateful connection management from the transmission protocol by implementing stateless data transmission with explicit acknowledgment mechanisms. Each packet is transmitted independently without maintaining connection state, removing the latency associated with stateful connection tracking while still ensuring reliable delivery through selective acknowledgment of received packets.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent implements dynamic transmission modes that can adapt between different acknowledgment strategies based on application requirements. The protocol supports both acknowledged and unacknowledged transmission modes, allowing the system to optimize for speed when possible and for reliability when needed, thereby reducing average latency while maintaining versatility.

Inventive Principle:

Principle #15Dynamics

3Reliability

If CAN bus technology is used, then real-time communication is achieved, but data rate is limited by arbitration procedure

Engineering Contradiction:

Improvereal-time communication reliabilityVSAvoiddata rate

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent implements periodic high-speed data transmission phases following the arbitration phase. The protocol structure allows for regular high-rate data bursts at predetermined intervals (after arbitration), maximizing the utilization of high-speed transmission windows while maintaining the deterministic timing characteristics that make CAN suitable for real-time applications.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent performs preliminary arbitration and address resolution before the high-speed data transmission phase. By completing all addressing, prioritization, and control functions in the initial arbitration phase, the protocol ensures that the subsequent data transmission phase can proceed at maximum speed without interruption, thereby achieving both high data rates and real-time performance.

Inventive Principle:

Principle #10Preliminary action

4Productivity

If Ethernet technology is used for IPv6 communication, then transmission efficiency is improved, but hardware cost increases

Engineering Contradiction:

Improvetransmission efficiencyVSAvoidhardware cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent creates a universal protocol that combines the advantages of CAN (real-time performance, low cost, simplicity) with the capabilities needed for IPv6 communication (large packet support, efficient transmission). The CAN EL protocol serves multiple functions: it maintains compatibility with existing CAN infrastructure, supports large IPv6 packets without segmentation, provides real-time performance, and reduces hardware requirements compared to full Ethernet implementations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP3661131B1Method for transmitting data via a serial communication bus, bus interface designed for this purpose, and correspondingly designed computer program

Publication Date: 2022.09.07 VOLKSWAGEN AG

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AI summary

The invention relates to an extension of the existing CAN FD data transmission protocol. The extension aims to enable the use of the IPv6 protocol for the CAN bus. To this end, the CAN FD protocol is further developed in an incompatible manner. One modification involves extending the data field (DF) which is positioned in the transmission frame after an arbitration field (AF). Any number of bytes may be entered into the extended data field (DF) within a defined upper limit. Since the data field (DF) is transmitted at a higher bit rate than the arbitration field (AF), the data throughput is drastically increased. An end-of-frame field (EF) is also provided in the transmission frame. At least one end-of-frame code, which has a length of 11 bits, is entered into the end-of-frame field (EF).