Kyu Ouk Lee

Publication Date


Document Type


First Advisor

Marcellus, Richard L.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Industrial Engineering


Telephone switching systems; Electronic--Reliability


In order for an electronic telephone switching system to perform its functions without loss of credits and earnings from customers, accurate reliability should be predicted before system release. A methodology for making this prediction is developed within the context of a particular system (Time Division Switching System). A bottom-up approach was used for system reliability prediction with step-by-step methods from component or circuit pack level to board, block, subsystem, and system level. For important component or circuit pack level reliability, a suitable model selection method of failure occurrences is recommended along with its parameter estimation method using statistical analysis. For expensive board level reliability, a weak link identification method and a reliability improving method are recommended. For inexpensive block level reliability, its components or circuit packs reliability were calculated from a model that included part stress analysis. For software reliability prediction, a suitable model selection method of failure occurrences is recommended, along with maximum likelihood parameter estimation. An objective failure intensity set-up method based on system test cost and system operation cost is recommended along with a prediction method of additional testing time required before system release. It was verified that a Time Division Switching system satisfied the reliability recommended by the International Telegraph and Telephone Consult Committee. In addition, the percentages of hardware reliability and software reliability were predicted along with each subsystem reliability, unavailability, number of failures, down time, mean time to first failure, and failure intensity.


Includes bibliographical references (pages 101-103).


x, 103 pages




Northern Illinois University

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