Real time characteristics of Ethernet for industrial applications

There is a growing interest of using Ethernet to support time constrained communication raised from process control, factory automation and other real- time applications of Industrial Environment. The suitability of Ethernet for industrial applications in the frame of real time is analyzed in this work. Ethernet is incontestably the most cost-effective solution to support communication in industrial applications. However, concerning for real-time traffic, the unpredictable delays and unfairness of station to access Ethernet, such as starvation effect and capture effect, leads to an unpredictable timing behavior of its supported application, such as manufacturing and process control, and directly confines its application in such region. Therefore, many improvements have been made to enable Ethernet to support time-constrained communication. These solutions are either by modifying the MAC protocol of Ethernet itself or implement an additional deterministic sub-layer over MAC protocol. The most straightforward solution to guarantee a bounded access time is to use a TDMA (Time Division Multiple Access) strategy. This paper first presents a comprehensive analysis of the characteristics of traditional Ethernet and the improvements for them, and then summarizes the interesting features offered by a switched Ethernet for supporting time constrained communication. (author)