Bus System Media Access Control Using Dual Channel Segmentation
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Solution Overview
Problem
Current CAN protocols face limitations in transmitting large data blocks efficiently while maintaining real-time conditions, as the bit-by-bit arbitration restricts bit rate and interruptions in communication protocols can lead to system failures and delayed transmissions.
Innovation Solution
A media access control method that allows one user station to have exclusive access to a first channel for bit-by-bit arbitration, enabling access to a second channel with a higher bit rate by using the TTCAN time-window structure to define enable intervals, ensuring collision-free and high-capacity transmission without separate arbitration for the second channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bit-by-bit arbitration is used to ensure collision-free transmission, then reliability is improved, but transmission speed deteriorates due to minimum bit duration requirements
Solution Approach 1:
The transmission channel is segmented into two separate channels: a first channel (CAN bus) dedicated to control messages with bit-by-bit arbitration, and a second channel for large data blocks with higher bit rate. This segmentation allows each channel to be optimized for its specific function, resolving the contradiction between reliability and speed.
Solution Approach 2:
The invention adds a temporal dimension to the arbitration mechanism by introducing enable intervals during which a station that has won arbitration on the first channel is granted exclusive access to the second channel. This temporal coordination allows high-speed transmission without collisions.
2Speed
If the communication interface is switched to a different mode for large data block transmission, then transmission speed is improved, but system reliability deteriorates due to protocol interruption
Solution Approach 1:
The invention merges two communication modes into a unified system: the CAN protocol with bit-by-bit arbitration and the high-speed transmission mode. By coordinating access through enable intervals and a coordination signal, the system combines the reliability of CAN arbitration with the speed of high-bit-rate transmission, avoiding protocol interruptions.
3Productivity
If a second channel with higher bit rate is introduced for large data blocks, then productivity is improved, but device complexity increases due to dual channel management
Solution Approach 1:
The first channel serves dual purposes: it transmits control messages using CAN protocol and simultaneously functions as an arbitration channel that grants access to the second channel. This multi-functionality reduces the need for separate complex control mechanisms while maintaining both reliability and high productivity.
4Loss of time
If enable intervals are predefined using TTCAN time-window structure, then real-time properties are improved, but adaptability deteriorates due to fixed time windows
Solution Approach 1:
While the TTCAN time-window structure provides fixed enable intervals for real-time guarantees, the system dynamically coordinates access to the second channel through a coordination signal exchanged between stations. This dynamic coordination within the fixed time windows allows flexible data block transmissions while maintaining real-time properties.
Data Source
AI summary
A media access control method is described for controlling access by one user station of a bus system to a first channel of the bus system utilized jointly by a plurality of user stations, where in the case of the method, at least one enable interval is specified for the user station, within which the user station has exclusive access to the first channel. In order to specify a media access control method in which large volumes of data may be transmitted relatively quickly and real-time conditions can be honored during the transmission of messages via the bus system, access to a second channel is utilized by a plurality of user stations is controlled using the method, the second channel being enabled for access by the user station only within the enable interval.