On the effect of communication delays in failure diagnosis of decentralized discrete event systems

We study the effect of communication delays on the performance of a coordinated decentralized architecture for failure diagnosis of untimed discrete event systems. The architecture consists of local sites communicating with a coordinator that is responsible for diagnosing the failures occurring in the system. A protocol that realizes the architecture is defined by the diagnostic information generated at the local sites, the communication rules used by the local sites, and the decision rule used by the coordinator to infer the occurrence of failures. Our prior work [6] has addressed the performance of a set of protocols under the assumption that messages sent from various local sites to the coordinator axe received in the order in which they are sent globally. In this work we relax the abovementioned assumption. We modify the coordinator's decision rule for one of the protocols analyzed in [6] to account for the reception of out of order messages at the coordinator's site. We discover conditions on the system structure under which the modified protocol performs as well as the centralized diagnostic scheme proposed in [11].