Bandwidth allocation scheme for cyclic-service fieldbus networks

Field devices in factory automation and process control systems generate time-critical, periodic, and time-available data that share the bandwidth of one fieldbus network medium. This paper presents a bandwidth allocation scheme that is applicable to cyclic-service fieldbus networks. The bandwidth allocation scheme transmits time-critical data as soon as the server is available. Transmission of periodic data is scheduled such that the network-induced delay will not exceed the maximum limit allowed. The bandwidth allocation scheme restricts the packet length of time-available data to satisfy the delay requirements of time-critical and periodic data. The bandwidth allocation scheme not only satisfies the real-time transmission requirements of both time-critical and periodic data, but also fully utilizes the bandwidth resources of the fieldbus network. The validity of this bandwidth allocation scheme is examined through simulation.