Reliability and Quality
Reliability Program and Specifications
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Overview
The reliability program provides enhanced reliability and is implemented as an integral part of the Lucent Technologies’ Process
Management Architecture (PMA) process. The reliability program is comprehensive, and includes activities such as setting and ensuring compliance with customer-focused system-reliability requirements, ensuring component qualification is consistent with use environment and system design, assuring satisfactory component-attachment reliability, predicting failure rates of Field Replaceable Units (FRUs), making sparing recommendations, assessing reliability architecture, modeling system reliability, assuring satisfactory system-downtime performance, reducing hardware failure rates through Environmental
Stress Testing (EST), and tracking field returns.
Design and development
During the design and development stage, reliability predictions, qualification and selection of components, definition of quality assurance audit standards, and prototyping of critical areas of the system ensure built-in reliability.
Manufacturing and field deployment
During manufacturing and field deployment, techniques such as environmental stress testing, production quality audits, field-return tracking, failure-mode analysis, and feedback and corrective-action further enhance the ongoing reliability improvement efforts on the
DMX Access Multiplexer.
Environmental Stress
Testing
DMX circuit packs are subjected to an Environmental Stress Testing
(EST) program. The purpose of the program is to improve reliability by reducing early life failures and implementing root-cause analysis and corrective action on circuit packs that fail EST.
Transmission downtime
DMX satisfies a stringent set of reliability specifications. Some of the critical specifications include Telcordia Technologies downtime requirements and objectives for multiplexers. Telcordia Technologies requirements state that the downtime of a two-way channel within a
SONET multiplexer, due to hardware failure, shall be less than 1.75 minutes per year in a Central Office (CO) environment and 5.25 minutes per year in a Remote Terminal (RT) environment. The corresponding objectives for these parameters are 0.25 minutes per year in a CO environment and 0.75 minutes per year in an RT
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Reliability Program and Specifications
Reliability and Quality
environment. These requirements and objectives appear in Telcordia
Technologies GR-418-CORE.
These requirements and objectives apply to all system elements needed to process a two-way channel, including the core system as well as the high-speed and low-speed interfaces. System-reliability analysis employing Markov modeling is used to determine the system downtimes. As specified in Telcordia Technologies GR-418-CORE, this analysis assumes a mean time to repair of 2 hours for the CO environment and 4 hours for the RT environment. Individual Field
Replacable Unit (FRU) failure rates used in the model were determined using the method described in Telcordia Technologies SR-332,
“Reliability Prediction Procedure for Electronic Equipment (RPP).”
FRUs are system elements that can be replaced in the field, including items such as circuit packs, removable optical interfaces, housings, cooling units, and removable LEDs.
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