Priority-Based Bus Access Control for Ethernet Data Transmission
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Solution Overview
Problem
Current Ethernet-based network technologies in vehicles face challenges in prioritizing messages across a network segment without causing bus access conflicts, particularly in linear bus structures and wireless networks, which is critical for real-time applications and IP communication.
Innovation Solution
A data transmission method using a transmission frame with a prioritization field that stores the priority of the last received packet in a minimum-priority memory cell, with a timer that decrements the priority if there's a pause in transmission, ensuring that messages are sent based on their priority levels to reduce latency and facilitate fair access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all messages are processed with the same priority in Ethernet networks, then network simplicity is maintained, but real-time communication requirements cannot be met
Solution Approach 1:
The patent introduces a priority parameter (P field) in the message header that changes the processing behavior of nodes. Messages are assigned different priority levels (0-7), and nodes use this parameter to determine transmission order, thereby achieving real-time communication requirements while maintaining relatively simple Ethernet-based infrastructure
Solution Approach 2:
The patent implements preliminary prioritization by setting the priority field in the message header before transmission. Nodes preemptively identify high-priority messages and prepare to transmit them first, ensuring real-time requirements are met without complex runtime decision-making mechanisms
2Loss of time
If message priorities are considered across the entire network segment, then real-time performance is improved, but bus access conflicts increase
Solution Approach 1:
The patent applies partial prioritization by considering message priorities only when necessary for real-time performance. The priority field is used to preempt transmission, but the system does not enforce strict priority ordering in all cases, allowing lower-priority messages to eventually access the bus when high-priority traffic subsides, thus reducing bus access conflicts while still meeting real-time requirements
3Quantity of substance
If IP communication with large packets is used, then data transmission capability is improved, but network bandwidth consumption increases
Solution Approach 1:
The patent segments large IP packets into smaller Ethernet frames for transmission over the bus network. This segmentation allows efficient utilization of the bus medium by transmitting multiple smaller frames in sequence, reducing the time any single transmission occupies the bus and thereby reducing overall bandwidth consumption while maintaining the capability to transfer large amounts of data
Data Source
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AI summary
The invention relates to a method for transmitting data via a communications channel (106), in which the data is transmitted with a transmission frame, wherein the transmission frame has at least one prioritisation field (PCP) for establishing the priority of the message and a data field, wherein the prioritisation field (PCP) functions to control the bus access by prioritising the messages. For this purpose, a bus access controller is used, in which the priority of at least the last received data packet is stored in a minimum priority storage cell (330). After receiving a data packet, a timer (320) is started, for which a timeout value is set, which is reset when a following packet is received. After reaching the timeout value, a decrementing of the value stored in the minimum priority storage cell (330) occurs. Thereafter, for the purpose of bus access control, when sending a packet, it is checked whether the priority of the packet to be sent is lower than the value stored in the minimum priority storage cell (330), and the sending of the data packet is prevented if the priority of the packet is lower than the value stored in the minimum priority storage cell (330).