New hybrid MAC-layer protocol for real-time bus networks

A hybrid group implicit token-CSMA/CD (GIT-CSMA/CD) access protocol for use in real-time bus networks is introduced. Network control is distributed over all nodes, thus eliminating the need for central switching. Operating features of the hybrid protocol are described together with its computer simulated performance evaluation. The results showing the delay-throughput characteristics are compared with CSMA/CD 1-persistent and token passing MAC-layer protocols. Optimum values for the number of stations comprising a group are obtained according to the requirements and specific conditions of each application. The implementation of the proposed protocol is based on the capabilities and the features of several existing CSMA/CD controllers and requires minor additional hardware and software