Approximation method for evaluating frequency of long service outages in telecommunications networks

An approximation method is presented for evaluating the frequency of long service outages in telecommunications networks. It measures how often a long service outage occurs, which is important because long service outages can seriously affect customers. The method currently used is problematic because the evaluation time increases exponentially with the telecommunications network size. A recently proposed approximation method by Watanabe et al. is highly accurate but its evaluation time also increases exponentially. Other known heuristic approximations are applicable only to cases in which the telecommunications network can be represented by series and/or parallel systems. The method proposed here overcomes these limitations. It is based on a simple equation that includes the frequency of long service outage and the frequency of failure. This equation gives both the upper and lower bounds of the value obtained with Watanabe's method, where these bounds are very close to each other, under the reasonable assumption that each element of a telecommunications networks is highly reliable. Numerical examples show that this method can be used to more quickly and more accurately evaluate the frequency of service outages for a realistically large network.