Delay analysis of unidirectional fiber-optic bus networks

There is a growing interest in studies on high-speed unidirectional fiber-optic bus networks to be used in metropolitan area networks (MANs). It is well known, however, that the original IEEE 802.6 MAN standard may exhibit an unfairness property depending on the position of stations. To cope with this problem, the p/sub i/-persistent protocol has been proposed. In fiber-optic bus networks various kinds of traffic are supposed to be carried, so that detailed analysis of the delay process is highly desired. However, the interdependence between station queues makes exact analysis intractable. We consider the p/sub i/-persistent protocol used in unidirectional fiber-optic bus networks and present a novel approximation method to evaluate the packet delay. First we model each station as a Geo/sup [X]//SBP/1 queueing system with p/sub i/-persistence and carry out an exact analysis. To take into account the correlation of occupied slots floating from upstream, we use the switched Bernoulli process (SBP) with two states for the service process. Then a moment matching procedure is developed to approximate the output process of occupied slots to the downstream neighbor station. The analysis exhibits good accuracy in the numerical examples.<>