Hard Real-Time Communication Based on Shared Ethernet

Ethernet with CSMA/CD mechanism is not suitable for time-bounded service. This paper presents a hard real-time communication protocol based on shared Ethernet named TTEP to solve the problem. It is unnecessary to change the hardware of Ethernet. TTEP is based on TDMA approach with master/slave scheme, and provides on-line admission control and on-line scheduling. This protocol uses CSMA/CD mechanism to send node addition requests and non-real-time traffic. And it transmits real-time traffic under the TDMA mechanism. Because production requirements, communication requirements and scheduling algorithm are localized in the master, it is easy to calculate when to produce the messages and when to transmit them. The messages are scheduled according to the calculated result within each EC. Therefore, this protocol has the ability to provide the guaranteed hard real-time communication.