1. Scope Reliability What is reliability ? Reliability parameters.
Failure characteristics
Sources of failures in communication system

2. 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

3. Definition Mathematically, this may be expressed as,
Reliability
Definition
Mathematically, this may be expressed as,
where is the failure probability density function.

4. 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

5. Hardware Failure characteristic
Reliability
Hardware Failure characteristic
Bath tub curve

6. Hardware Failure characteristic
Reliability
Hardware Failure 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.

7. Hardware Failure characteristic
Reliability
Hardware Failure 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.

8. Hardware Failure characteristic
Reliability
Hardware Failure 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

9. Sources of failures in FOP system
Reliability
Sources of failures in FOP system

10. Sources of failures Back
Reliability
Sources of failures Back
Source
Precautionary Measure
End copper cable
Break in cable
Interference
Short circuit due to moisture
Use multistranded conductor and armoured cables
Shielded cables for high
speed data circuit
Jelly filled cables are used

11. Sources of failures Back
Reliability
Sources of failures Back
Source
Precautionary Measure
Connectors
Poor soldering
Improper fitting
Bad quality of connector
Skilled technicians, Use of factory crimped cables
We ensure connectorisation done as per OEM

12. Sources of failures Back
Reliability
Sources of failures Back
Source
Precautionary Measure
Terminal equipment
Common failure point:
Power supply, Transceiver module
Application card failure
Improper grounding
Rodent problem
Aging
Dual power supply
Dual transceiver port
Backup channel is provided on another
application card in same equipment.
Proper grounding is ensured
Sealing of cable entries.
Regular preventive maintenance

13. Sources of failures Back
Reliability
Sources of failures Back
Source
Precautionary Measure
Fiber optic patch cord &
FDF
Break in patchcord
Attenuation due to improper connecter fitting
Break in fiber in FDF
Laid through PVC conduit
Use of FC/PC type connector.
Proper marking of fiber in FDF and proper harnessing of field patchcords in the box.

14. Sources of failures Back
Reliability
Sources of failures Back
Source
Precautionary Measure
Under ground FOP cable
Break in cable
Attenuation due to bending
Laid through HDPE conduit
Laying of FOP cable along with HV power cable is avoided.
Burrried under ground at least 2 ft.
90 degree sharp bends

15. Sources of failures Back
Reliability
Sources of failures Back
Source
Precautionary Measure
FOP Joint Box
Conductor snapping
Breaking of fiber in splice protector
Corrosion of splice protector due to moisture in grace
Following things are ensured
OPGW conductor is tightly fitted in joint box.
Complete sealing of joint box
OPGW and joint box is properly mounted / fitted on tower.

16. Sources of failures Back
Reliability
Sources of failures Back
Source
Precautionary Measure
OPGW conductor
Conductor snapping
Breaking of OPGW due to electrical fault.
Aging
Theft
Good quality OPGW accessories are used.
OPGW is grounded on every tower.
Backup is provided through Ring architecture
Regular maintenance of OPGW is carried out by transmission Div.
In some area fencing is done at the bottom of tower
Joint boxes are painted with Black color
Joint boxes are kept at height as much as possible.

17. Thumb Rules Reliability 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.