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On the Capacity of p-Persistent CSMA


Marek Mi?kowicz


Vol. 7  No. 11  pp. 38-43


The CSMA-based algorithms constitute a heart of contemporary wireless media access control technology. In last decades, various enhancements have been introduced to basic CSMA schemes, first of all, in order to support collision avoidance. At the same time, the performance analysis of the p-persistent CSMA has gained a renewed interest recently since the behavior of many CSMA protocols might be studied by the p-persistent model. The capacity of the p-CSMA is an important performance measure. It establishes the best-case channel utilization that may be obtained in the p-persistent CSMA with varying p. The goal of the paper is to compare the maximum channel utilization of the p-persistent CSMA with the corresponding measure for the predictive p-persistent CSMA implemented in MAC sublayer of LonTalk/EIA-709.1 protocol used for communication between intelligent sensors and actuators in LonWorks technology. A comparison of both CSMA schemes shows that the predictive p-persistent CSMA throughput is close to the capacity of the p-persistent CSMA only for small network sizes. If the number of contenders is greater, the throughput of the predictive p-CSMA is much smaller than p-CSMA capacity.


Media access control, Carrier sense multiple access protocols, Performance evaluation