Communication Mediums for Signal, ITS, and Freeway Surveillance Systems Final Report (1996) / Chapter Skim
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A.5.5 Reliability
A.5.5 Reliability
Pages 518-537
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From page 518... ...
A prudent communications equipment designer Includes bit error rate In his specifications. A system is composed of components, which in a non-integrated sense may also be considered as a system.
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From page 519... ...
For example, wireless communications may have an expected bit error rate (BER) of ~ error in 105 bits while a fiber optic communications linic may have a BER of ~ error in 10~ bits or less.
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From page 520... ...
An increase in bit error rate indicates a problem in communicators links, such as increased interfering noise in wireless transmission from an aging transmitter solid state device causing a decrease In transmit signal power. Within wireless communications systems, a failure may occur and yet the system may be performing to specification.
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From page 521... ...
' procurements, verifiable MTBF information is necessary; otherwise, the cost analysis is unsubstandable. A.5.5.1 How Reliability is Achieved Reliability in communications equipment starts u id quality design.
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From page 522... ...
The reason is Eat mechanical interconnects are minimized and noise interference is more easily managed when protection is considered a part of We integrated circuit design. Perhaps We use of large scale integrated circuits has enhanced reliability of advanced communications products compared with convendonal products more so Dan improved manufacturing methods and testing.
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From page 523... ...
Disruption may be through cable damage, or in the case of winless, an obstruction in the radio line of sight Pa~-sw~tched optical rings and packet radio networks are examples of cable and wireless communications path disruption fault tolerance. Id packet radio networks, to achieve fault tolerance a system must be designed wad a minimum of two communications paths for each transceiver location.
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From page 524... ...
Thus, use of advanced communications technology, assuming Mat it has successfully been Trough beta testing and is in production status, usually exhibits a much hider MIBF Man conventional technology. A.5.5.3 tmpactofInstalIation Design on Reliability Communications equipment may be designed win high reliability; however, if installation design is improper, reliability can be significantly impacted.
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From page 525... ...
must be designed to maintain operating temperatures of junctions at an acceptable level to achieve the reliability objective of He equipment within He specified operating temperature range and cooling approach. There are many types of solid state components from low cost plastic, to industrial grade ceramic, to surface mount MIL-STD-~83 compliant.
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From page 526... ...
~ a NEMA cabinet on a freeway in Arizona wig a 49° C ambient environment and solar loading of Me cabinet, an internal temperature of 74° C is highly probable dunng peak solar loacling periods. Solid state component junction temperature will increase perhaps by 60° C causing an MIFF decrease from 107 hours to 104 hours (10 million to 10 thousand hours)
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From page 528... ...
Britishtelecom's Approach to Software Quality," discussing Be impact of software quality assurances on software reliability For software to be reliable it must be weB designed and weB tested, including stress testing. Stress testing is associated with worst case loading of Be processor (within its specified operational envelope)
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From page 529... ...
Software quality and reliability is a formal process and should be treated by jur~sdichons as an important requirement of a procurement Advanced communications systems employ more software and firmware Wan convendonal commun~cabons systems. The result is Fat hardware components are minimized since these systems use digital processors which support multifunctional operations.
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From page 530... ...
chips, advanced communications hardware reliability is increased. Since software and/or firmware provides Me communications functionality, reliability of software must be considered.
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From page 531... ...
SR-TSY-000385 Reliability Manual for Telecommunications SR-TSY-001130 Reliability and System Architecture Testing SR-TSY-001369 ~ Reliability of Laser Diodes and Modules: Generic Requirements TA-NWT-357 Assuring Reliability of Components Used In Telecommunications Equipment: Generic Requirements _ . TA-NWT-000942 Hardware Reliability Assurance Program: Generic Requirements TA-NWT-001089 ~ Electromagnetic Compatit lity and Electrical Safety: Generic Criteria for Network Telecommunications Equipment TA-NWT-001202 Supplier Quality Process Requirements TA-NWT-001221 | Generic Requirements for Passive Fiber Optic Component Reliability Assurance Practices TR-NWI-000063 Network Equipment- Building Systems: Generic Requirements (Environment and Electrical Safely)
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From page 532... ...
. __ TR-NWT-001075 Generic Requirements for Outside Plant Bonding and Grounding of System Hardware TR-NWT-001230 SONET Bidirectional Line Switched Ring Equipment Generic Criteria .__ TR-NW1-001274 Reliability Qualification Testing of Printed Wiring Assemblies Exposed to Airborne Hygroscopic Dust TR-NWT-001305 Generic Requirements for Surge Protected Terminal Blocks .
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From page 533... ...
. .._ Recommended Practice for Emergency and Standby Power Systems 493-1 990 Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems _ Guide for the Installation of Electrical Equipment to Minimize Noise to Controllers from External Sources 518-1982 730-1 989 IEEE Standard for Software Quality Assurance Plans l I IEEE Standard for Softwa ~ Configuration Management Plan l 828-1 990 829-1 983 IEEE Standard for Test Documentation 982.1/2-1 988 Measures to Produce Reliable Software 1 008-1 987 l I Standard for Software Uni Testing = 1012-1986 1042-1987 Standard for Software Verification and Validation Plans Guide to Software Configuration Management 1061-1992 Standard for Software Quality Metrics Methodology Standard for Developing Software Lde Cycle Process 1074-1991 1110-1992 Recommended Practice for Powering and Grounding Sensitive Electronic Equipment IEEE Standards for Electromagnetic Compatibility SH 15537 Society for Automotive Engineers _ 1 _ SAEJ 1113 Department of Defense DOD 5000.3 Electromagnetic Susceptibility Procedures for Verifying Vehicle Components .
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From page 534... ...
Specification Number ~ Federal Communications Commission Part 15 Unintentional Radiators, Class A and B Devices, Radiated Emissions and Susceptibility Table A.5.5.6~2 Summary Overview of Communication Reliability Considerations Equipment Related Issues ~ _ '~ _ _ · Formally determined, guaranteed mean · Proper network design with link marked time between failure and high probability of maintaining signal/noise , · System designed to reliability objectives · Compatible specifications at all OSI using subsystem MTBF vex: · Fault tolerant hardware and network· Fault tolerance network architecture architecture · Equipment designed for compatibility· Installation environment designed to with environmental variations equipment compatibility and to reliability · Equipment meeting radio frequency objectives (such as redundant air interference and electromagnetic conditioning) compatibility standards · Equipment designed for compatibility with power variation · Equipment designed using worst case· Prime power interconnect designed to component parametric variations reliability objectives with use of battery backed-up, uninterruptable power system · Equipment with dynamic test, fault~ · Data element secured to prevent detection and fault propagation unskilled, unknowledgeable tampering _ ~ · Equipment using large scale integration· Installation design considering electromagnetic compatibility and grounding standards · Equipment manufactured under formal| · Lightning protection on power end quality assurance program (using metallic signal lines specification-compliant components, materials, processes, and test procedures including bum-in)
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From page 535... ...
A.5.5.7 Summary of Reliability Issues New communications equipment is more reliable Han older equipment for the following reasons: Use of large scale integration; · Use of softwaIe/firmware to reduce hardware components; Perfection of fault tolerant technology and application to advanced communications . equipment; Advances in adaptive signal processing and modulation technology; Evaluation of open standards; and Advances in network routing protocol and network management protocol.
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From page 536... ...
and digital signal processors reducing component count · Evolution of fault tolerar t technology from · Advanced modulation techniques NASA and communications equipment with improved immunity to n~nd He and mu, · Development of OSI interface standards to 7 | · Emphasis on product design for levels reliability and quality assurance sups ng ~ ~ ~ · Emphasis on network interoperability with | · Improved IC packaging and heat L associated standards for bridges, routers, management on printed circuit and switches Roams · Emphasis onnetworcprotocolstandards | · Development ofinten~et protocol with congestion control and dynamic routing and dynamic routing · Improved transmission medium adaptation | · Improvements in hardware and through use of echo cancelers and adaptive software test methodology modern technology | · Evolution of optics communications | · Advancements in error detection technology with low-loss, low-noise and error correction transmissions | · Improved circus design and printed circuit | · Development of hybrid and board design through modem computer- microwave integrated circuit aided design technology · NehNorkmodelingtechnologytoprove- | · Lower cost perforrnanceevatuation before-build and tradeoff analysis Several articles amplifying this information may be of interest to the reader: Proceedings of the [EKE, Volume 82, No.
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From page 537... ...
01d communications equipment typically had MTBFs In the 2000 to 3000 hour range. Advanced commun~cadons system technology can be obtained wad MTBFs in He 50,000 to 100,000 hour range.
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