Comparative Simulation of High Speed Unidirectional Local Area Bus Networks

With a rapidly growing trend of using fiber-optics as transmission media, there is an immense interest in high speed local area networks (LAN s). These networks offer an efficient and cost-effective means of communication within a relatively small geographical area. Bus and ring topologies are the two most popular topologies for fiber optics LANs. In this paper, however, we will only consider bus topology. In a typical fiber optics bus network, transmission is unidirectional. In our study the time is slotted and each station attempts to transmit in an empty slot persistently with a preassigned probability. Messages are assumed to be of variable length and are segmented into fixed size packets such that each packet fits in a slot. Fair access to the shared transmission medium can be achieved if access probabilities are assigned propetly to all stations. Three probability assignment schemes are considered: uniform, linearly increasing, exponentially increasing, and optimaI. The average delay per message for this network is studied through a simulation program for various probability assignment techniques. This study shows that there is significant difference in performance of these techniques.