Improving field performance of telecommunication systems is the key objecti
ve of both telecom suppliers and operators, as an increasing amount of busi
ness critical systems worldwide are relying on dependable telecommunication
. Early defect detection improves field performance in terms of reduced fie
ld failure rates and reduced intrinsic downtime. This paper describes an in
tegrated approach to improve early defect detection and thus field reliabil
ity of telecommunication switching systems. The assumptions at the start of
the projects discussed in this paper are: Wide application of code inspect
ions and thorough module testing must lead to a lower fault detection densi
ty in subsequent phases. At the same time criteria for selecting the most c
ritical components for code reviews, code inspections and module test are p
rovided in order to optimize efficiency. The primary goal is to identify cr
itical components and to make failure predictions as early as possible duri
ng the life cycle and hence reduce managerial risk combined with too early
or too late release of such a system to the field. During test release time
prediction and field performance prediction are both based on tailored and
superposed ENHPP reliability models. Experiences from projects of Alcatel'
s Switching and Routing Division are included to show practical impacts.