The performance of a timer-controlled token passing mechanism with finite buffers in an industrial communication network

The timer-controlled token-passing mechanism widely used in industrial communication networks is analyzed. Several real network parameters, such as finite buffers and finite token-holding time (THT), which generally determine the overall performance of a network, are considered. The approximate matrix equation between the queue length distribution and the token rotation time is derived. Based on this matrix equation, the equations for the mean waiting time and the blocking probability are also derived. These equations can be easily solved using personal computers, due to its simple matrix structure and small computation time. Using these equations, the performance of field bus or other timer-controlled token-passing networks can be more accurately evaluated, since finite size buffers and finite THT are considered. The approximation error is shown to be small by computer simulation