Telcordia Reliability Prediction Procedure: Upper confidence levels

SR-332, reliability prediction procedure for electronic equipment, is a module of the Telcordia family of requirements (FR) known as FR-796, reliability and quality generic requirements (RQGR). The purpose of the Telcordia reliability prediction procedure (RPP) is to document a standard method for predicting device and unit hardware reliability as well as serial system hardware reliability. A prediction of reliability is an important element in the process of selecting equipment for use by telecommunications service providers and other buyers of electronic equipment. As used in the RPP, reliability is a measure of the frequency of equipment failures as a function of time. In 2006, the RPP was revised for the first time since 2001. Among many changes, the new issue 2 introduced a significant enhancement to the procedure: the ability to estimate arbitrary upper confidence levels (UCLs). This paper will provide a brief overview of the RPP, review modifications to the procedure in Issue 2, and in particular describe the motivation for defining these new UCL techniques, the addition of generic standard deviation values, and the methodologies for calculating upper confidence levels. In conclusion, the techniques introduced in issue 2 allow for the calculation of failure rate UCLs at any level of confidence, not just 90%. A side benefit is that the new techniques also allow for the estimation of the mean failure rate of electronic equipment.