Stability and Optimization of the CSMA and CSMA/CD Channels

A comprehensive study of the stability and optimization of the infinite population, slotted, nonpersistent CSMA and CSMA/CD channels is presented. The approach to both stability and performance optimization differs significantly from previous work, and provides a number of new results including robustness in stability and performance in the presence of channel and control parameter variations. It is first shown that both channels are unstable under the usual assumption of random retransmission delay. Pake's lemma is then applied to study the properties of a type of distributed retransmission control which provides stable channels. Basic results are in the form of inequalities which define stability regions in the space of channel and control parameters, and further permit one to specify controls which maximize channel throughput as a function of packet length and CD time with stability guaranteed. The delay versus throughput characteristic for the stabilized channels is derived and used to demonstrate the performance achievable with these channels.