Implementation of a bandwidth allocation scheme in a token-passing fieldbus network

This paper presents a method for implementing a bandwidth allocation scheme on Profibus that operates on a token-passing discipline basis. In order to implement the bandwidth allocation scheme, this study incorporates the following additional functions to the fieldbus datalink layer (FDL) protocol of Profibus. First, the medium bandwidth of the network system is separated into both periodic and time-available intervals, and, second, node timers are synchronized over a local link. The validity of this bandwidth allocation scheme is determined using an experimental model of a network system. The results obtained from the experimental model show that the proposed scheme restricts the delay of both periodic and time-critical data to a pre-specified bound. The proposed bandwidth allocation scheme also fully utilized the bandwidth resource of the network system.