Evaluation of the normalized proportional allocation scheme's application to the asynchronous bandwidth in the fieldbus protocol

An evaluation of the application of the normalized proportional allocation scheme (NPAS) to the asynchronous bandwidth allocation of the fieldbus protocol is presented. The analysis is focused on the gain that can be achieved by using the NPAS for bandwidth allocation, after deriving the suitable asynchronous bandwidth size that will keep the token cycle time within a certain bound. The gain is compared with the case when the equal partition allocation scheme (EPAS) is used, considering an asymmetrically loaded system (with regards to the aperiodic load distribution among the nodes of the network). The simulation results show the superiority of using the NPAS over using the EPAS, in terms of increasing channel utilization, and decreasing transfer delays for less non-urgent traffic.