Unslotted 1- and P-Persistent CSMS-CD protocol for Fiber Optic Bus Networks

Abstract

We analyze the performance of the unslotted 1-persistent carrier sense multiple access with collision detection (CSMA-CD) protocol for fiber optic bus networks with a finite number of stations M, each of which has an infinite storage buffer for storing packets with its length fixed or exponentially distributed. Treating the bus network as an M-class priority queueing system with apreemptive-repeat-identical retransmission strategy, we show numerically that this 1-persistent retransmission strategy provides better delay-throughput performance than the non-persistent one. To satisfy the fairness of equal delays among stations in the bus network, we next present the unslotted p(i)-persistent CSMA-CD protocol. Under this protocol, the first packet arriving at station i is forced to enter into the backoff procedure with the probability of (1 - p(i)). After backoffs, transmission begins until the station becomes empty. We determine the persistent probability p(i) and show that the delay-throughput performance of the p(i)-persistent strategy is better than that of the 1-persistent one. and further it is robust for any packet lengths. Simulation results are presented to verify the analytical results.