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 (Debouk et al., 2000) has addressed the performance of a set of protocols under the assumption that messages are received by the coordinator 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 two of the protocols analyzed in Debouk et al. (2000) to account for the reception of out of order messages. We discover conditions on the system structure under which the modified protocols perform as well as the centralized diagnostic scheme proposed in Sampath et al. (1995).