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Explore the definition, parameters, and characteristics of reliability in communication systems. Learn about different sources of failures, including infant mortality, random failures, and wear out. Discover essential thumb rules for ensuring system reliability.
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Reliability Scope • What is reliability ? • Reliability parameters. • Failure characteristics • Sources of failures in communication system
Reliability Definition • Generally defined as the ability of a product to perform as expected over time • Formally defined as the probability that a communication system performs its intended function for a stated period of time under specified operating conditions
Reliability Definition • Mathematically, this may be expressed as, where is the failure probability density function.
Reliability Reliability parameters • MTBF : Total operating time divided by the number of failures. MTBF is the inverse of failure rate. • MTTR : Mean Time To Repair (MTTR), is the time taken to repair a failed hardware module. • Availability = MTBF MTBF + MTTR
Reliability HardwareFailure characteristic Bath tub curve
Reliability HardwareFailure characteristic Infant Mortality • This class of failures cause newly manufactured hardware to fail. • Mainly due to manufacturing problems like poor soldering, leaking capacitor etc. • These failures can be detected during system burn in tests in factory.
Reliability HardwareFailure characteristic Random Failures • Random failures can occur during the entire useful life of a hardware module. • These failures can lead to system failures. • Normally Redundancy is provided to recover from this class of failures.
Reliability HardwareFailure characteristic Failures due to Wear Out • Mainly due to degradation of component characteristics will cause hardware modules to fail. • can be minimised by preventive maintenance
Reliability Sources of failures in FOP system
Reliability Sources of failures Back
Reliability Sources of failures Back
Reliability Sources of failures Back
Reliability Sources of failures Back
Reliability Sources of failures Back
Reliability Sources of failures Back
Reliability Sources of failures Back
Reliability Thumb Rules • Use good quality hardware from reputed vendor • Get manufacturer test reports • Carry out FAT • Do proper installation and commissioning • Ensure proper installation during SAT • Keep system documentation ready to minimise downtime. • Carry out periodic maintenance. • Asses life of HW and replace it in time.