Network approaches have been widely utilized in the analysis of system reliability, especially for non-repairable systems. On the other hand, the state-space approach has been used to analyze repairable systems in terms of availability. However, it often requires much computation cost for analyzing the system availability.
In this paper, a 'simple approximation' method is proposed for calculating the unavailability of three basic reliability structures i.e. series, parallel, and k-out-of-n structures. This method is applied to the analysis of three specific telecommunication blocks and also is compared with the conventional method. The proposed method is shown to be valid within less than 0.4% error for the above blocks.