An error model for safe industrial communication

The residual error rate of a safety critical system gives the residual risk of a system failing, considering the mitigation mechanisms that are in place to prevent incidents. This calculation has to be based on a model that describes the error rate of the system without mitigation mechanisms in place. For industrial communication protocols, a simple error model is given in IEC 61784-3 [1, B.3]. This simple model is an abstraction of reality, trying to model just those properties of reality needed to calculate the residual error rate for an industrial communication system. Unfortunately, the model has two problems that will be addressed in this paper: burst-errors are not properly modelled and the Bit Error Rate (BER) of the model is under heavy discussion in the standardization committees. Therefore this paper proposes another approach for an error model that does not rely on a BER, but is based on the standards used for electromagnetic compatibility (EMC) testing, and tends to deliver a more realistic distribution of errors for industrial environments.