CAN总线和Ethernet的性能分析与评价

Performance Analysis and Evaluation of CAN and Ethernet

目的分析在工业计算机控制系统中广为应用的基于事件触发方式的CAN总线和Ethernet的网络性能,为通信协议的改进和实际工程应用提供理论和方法的指导.方法通过载波侦听多路访问/冲突避免(CSMA/CA)的CAN总线和基于载波侦听多路访问/冲突检测(CSMA/CD)的Ethernet的通信协议分析数据帧结构和包信息率,并应用实时调度理论分析了周期性信息时延的确定性和有界性,利用一个典型的应用实例对网络性能进行二者的定量和定性分析.结果从分析信息到达间隔与吞吐量、平均信息时延、通信冲突率、网络利用率、网络效率和负载完成率的关系和通信实时性知,CAN总线在诸多性能方面好于Ethernet.结论在通信频繁的工业应用中,CAN总线特别适合于短通信距离的基于事件触发的现场信息实时通信.

CAN and Ethernet, based on event-triggered, are the two of typical networks that are applied in industrial computer-controlled systems widely. The analysis of their network performance is studied in this paper, which will set up a good basis for further improvement and realization of control network. Firstly, a discussion about the features of the CSMA/CA based CAN and the CSMA/CD based Ethernet is presented in this paper. Secondly, the quantitative and the qualitative analyses of CAN and Ethernet are conducted and compared in the following performance aspects： the message frame format, data coding efficient, deterministic and bounded characteristic of messages, and the relation of throughout, average message delay, collision probability, network utilization, network efficiency and message finish rate with arriving interval of messages. Finally, the analysis results indicate that CAN is superior to Ethernet in application in which message traffic has stringent time constraints and the direct transmission distance between two nodes is short.