Dynamic Behavior of a CSMA-CD System with a Finite Population of Buffered Users

In packet broadcast networks with buffered users, queues of packets at the users interfere with each other through a shared broadcast channel. Therefore, it is difficult to analyze the performance of such Systems by classical queueing theory. This paper provides an approximate performance analysis of a slotted nonpersistent CSMA-CD system with a finite number of users, each having a buffer of finite capacity. We develop an approximate Markovian model of the system with a multidimensional state vector. To analyze the model, We utilize an approximate analytical technique called equilibrium point analysis (EPA). Then, the throughput and average packet delay characteristics are obtained and the system stability behavior is demonstrated. An approximate expression is also derived for the probability distribution of the number of packets in a buffer. Numerical results from both analysis and simulation are given to illustrate the accuracy of those analytic results. Using the analytic results, we examine the effect of the collision detection capability on the system performance. Furthermore, we consider how to select both the rescheduling probability and the buffer size that guarantee the system stability, keep the probability of buffer overflow sufficiently small, and at the same time minimize the average packet delay.