Space-time analyses of CSMA/CD protocols

The CSMA/CD (carrier-sense multiple-access/code division) protocols are analyzed in both time and space domains using space-time models. The models show that collisions are determined by the locations of nodes in a spatial domain as well as by the packet arrival times. A vulnerable area where a collision can potentially take place is determined by considering spatial dependency. Accurate estimation of the size of the vulnerable area and a corresponding collision probability allows one to derive the expected throughput rather than the worst-case throughput. The analytic results indicate that the expected performance is considerably higher than the previous worst-case performance. For example, compared to the previous result of 0.6 for α⩽0.01, the throughput of the one-persistent CSMA/CD protocol in the space-time model is shown to be as much as 0.8