Probabilistic timing analysis of the h-BEB collision resolution algorithm

Ethernet networks are becoming increasingly popular in industrial computercontrolledsystems, as they allow for a single network protocol at both the higher and the lowerlevels of an industrial communication infrastructure. Despite the introduction in the early 90s ofa full-duplex operating mode, numerous industrial Ethernet networks still operate inheterogeneous environments, with Ethernet Switching Hubs interconnecting both independentnode stations and industrial Ethernet Repeater Hubs. Among node stations interconnected by aRepeater Hub, the network still operates in the traditional shared Ethernet mode; that is,collisions are solved by means of a probabilistic contention resolution algorithm i.e., themedium access is inherently non-deterministic.In this paper, it is analyzed an enhanced collision resolution algorithm for shared Ethernetnetworks, referred as high priority Binary Exponential Backoff (h-BEB). Such algorithm allowsthe coexistence of Ethernet standard devices together with modified (real-time) devices in thesame network segment. Both the analytical and the simulation timing analysis show that theh-BEB algorithm guarantees a maximum access delay that is significantly smaller than for thecase of standard Ethernet stations. Such enhanced collision resolution algorithm enables thetraffic separation between standard and modified (real-time) stations, and is therefore able toguarantee a real-time communication behavior in unconstrained traffic environments