Modeling and Simulation in the Study of Real-time Performance in RFieldbus System

摘要

Token-Passing has been adopted on FDL in RFieldbus. Its PHY layer integrates the traditional Asynchrony + DSSS in wired and wireless segment respectively. This protocol was modeled as a multi-server-single-queue when the target token-rotation time meets a dynamic boundary. Two lower priority queues in RFieldbus were transformed into two M/G/1/∞ systems with two different Poisson-arrival rates, so that the complexities of the time properties in RFieldbus was depicted easily by several parameters. Upon the model a simulator based on OMNet++ was built up with 4 layers infrastructure. The top layer is the system-module inclosing 4 compound modules, which was composed by different simple modules on bottom layer. All the activities of the Token-Passing protocol algorithm are implemented in individual subroutine written in C++. The comparison with the real measuring Tcycle in 13 scenarios show the error deviation of the simulator is not more then 25%, and is about 10% when there is no mobile segment.