A Multistage Hierarchical Distributed Arbitration Technique for Priority-Based Real-time Communication Systems

ISO 11898 is a communication protocol based on the Carrier Sense Multiple Access with Collision Detection and Arbitration on Message Priority (CSMA/CD+AMP) technique, which at present is largely used as a real-time network for industrial environments. Unfortunately, because of the peculiarities of the arbitration technique it adopts, it suffers from severe limitations on the maximum extension of the network, which cannot be overcome simply by means of improvements in the transceiver’s technology as they depend on the limited propagation speed of the signals on the communication support. In this paper, a new kind of network is presented that features a behavior very similar to ISO 11898, but which achieves noticeably larger areas to be covered without having to reduce the bit rate. It relies on a tree topology and adopts a brand new multistage hierarchical distributed arbitration technique, which takes the increased propagation delays into account properly. priority). This means that the same techniques that are available to find a feasible schedule of tasks can be used also for the messages to be exchanged over the network.