A Reliability Analysis of Local Telecommunication Switches

This paper presents a reliability analysis of Local Exchange Carrier telecommunication switches in the United States, based upon empirical data. Telecommunication switch outage statistics are analyzed for a multiyear period, allowing examination into switch failure frequency, causes, and trends. Failure categories are created by reported outage cause codes, including human error, design error, hardware failure, and external factor causality categories. During this study period, the number of local exchange switches remained fairly constant in the public switched telephone network. The major result of this study is that, as a total population, local telecommunication switches exhibited reliability growth during this period, and failure event arrivals may be classified as a nonhomogeneous Poisson process (NHPP). Another result is that procedural, software design, and hardware design errors account for 40% of all local telecommunication switch failures.