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Communication Circuits: Types, Media, and Ownership

Learn about the different types of communication circuits, including point-to-point and multipoint circuits, as well as the various circuit media available. Understand ownership and error conditions, prevention, and correction in communication circuits.

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Communication Circuits: Types, Media, and Ownership

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  1. Chapter 9 Communication Circuits

  2. Agenda • Definition • Types • Media • Ownership • Error conditions, prevention, and correction

  3. Definitions • Telecommunication circuit • Link • Data link • Channel • Data circuit • Forward channel (high speed for data) • Reverse channel (low speed for control) • Node

  4. Type of Circuits • Point-to-point circuits • Multipoint circuits or multidrop circuits • Two-wire circuits and four-wire circuits • Analog • Digital circuits • ISDN • T-carrier systems

  5. Point-to-Point Circuits • Only two points or nodes • Between two telephones or terminal to computer • More expense • Necessary & high volume of traffic

  6. Multipoint circuits • Multidrop circuit or a network • Low volume of traffic • Less expensive

  7. Two-wire and Four-wire circuits • Two-wire circuits • Half-duplex circuits • Frequency division multiplexing for full-duplex data flow • Standard dial-up telephone • Less expensive • Four-wire circuits • Full-duplex circuits • Leased lines • More expensive

  8. Analog Circuits • Voice grade circuits • Low speed but up to 56,00bps • Noise • Error • Low-speed circuits or subvoice-grade circuits • Subdivide voice grade circuit to 12 or 24 circuits • Speed ranges between 45 to 200 bps • Burglar alarm, fire alarm, telegraph, & Teletypewriter usage • Use Amplifier for long distance

  9. Digital Circuits • Low error rate, noise, & high speed • Data service unit/channel service unit (DSU/CSU) • Shape and time the pulses • Less complicated • Less expensive • Need repeater for long distance

  10. Integrated Services Digital Network (ISDN) - I • Types of channels • B (bearer) channel: 64kbps data • D (delta) channel: 16kbps signal • Broadband ISDN (BISDN): a full-duplex circuit or two asymmetrical simplex channel for high speed • Access methods • Basic rate interface: 2B+D • Primary rate interface: 23B+D • Broadband ISDN (B-ISDN)

  11. Integrated Services Digital Network (ISDN) - II • Benefits • Efficient • Integrated voice and data • Programmable to meet user’s need • Robust signaling channel for network management • International defined open system interface • Problems in US • Difficulty in agreeing on precise standards • High cost • Not active marketed service

  12. T-carrier Systems • T1, T2, T3, T4 • T2 and T4 for carriers • T1 and T3 for carriers and customers • T1 Line • Repeater for every mile • 24 circuits of 64,000 bps • Pulse Code Modulation (PCM) or Adaptive Differential Pulse Code Modulation (ADPCM) • Multiplexing equipment needed • Flexible to reconfiguration, low cost for high quality and volume • Fractional T1 (any multiple of 64kbps)

  13. Switched Multimegabit Data Service (SMDS) • High-speed switched digital service from carrier • Two speeds • T1 speed (1.544 Mbps) • T3 speed (44.736 Mbps) • Configuration • Lease line from organization to central office • Normal, shared communication facilities between central offices • Benefit: less expensive

  14. Digital Subscriber Line (DSL) - I • Deliver digitized signals over telephone lines • Higher data communication speed for Internet usage • xDSL for dedicated, point-to-point, public network access over twisted pair copper wire • More bandwidth downstream than upstream • More for individual customer than business organization

  15. Digital Subscriber Line (DSL) - II • Asymmetric digital subscriber line (ADSL) • Standard voice band • Medium speed upstream band • High speed downstream band • New offerings • G.Lite ADSL: lower bandwidths for less cost • SDSL (symmetric digital subscriber line): equal speed in both direction • VDSL (very-high-rate digital subscriber line): high speed over short twisted pair telephone lines up to 1,000 feet

  16. Circuit Media • Conducted or guided media • Twisted pair or unshielded twisted pair (UTP) • Shield twisted pair • Coaxial cable • Optical fiber • Radiated or unguided media (wireless) • Microwave radio • Satellite • Infrared

  17. Twisted Pair • 22, 24, 26 gauge • Twisted pair or unshielded twisted pair (UTP) • Electrical noise & other interference • Electrical Industries Association (EIA): Category 1, 2, 3, 4, 5,5E (extended), 6, and 7 (data grade starting Cat 3) • Punchdown block

  18. Shielded Twisted Pair • Pros: • Less interference • Faster speed • Cons: • More expensive • Physically larger and difficult to connect to a terminating block

  19. Coaxial Cable • Pros: • Large bandwidth (400 - 600 MHz) • High capacity • Less interference • Good for noise environment • Cons: • Tapped easy (security problem) • Bulky to install

  20. Optical Fiber - I • Types: • Single mode: more expensive & high capacity • Multimode: less expensive and less capacity • Inexpensive plastic • Expensive glass • Standard • Synchronous optical network (SONET) in US

  21. Optical Fiber - II • Pros: • High bandwidth • No interference • No crosstalk • Small physical size and light weight for installation • Very secure • Cons: • Repeater for long distance • Expansive

  22. Microwave Radio - I • Characteristics • Long distance • Straight line transmission • 20-30 miles between transmission towers • Radio license by FCC • Private microwave links connecting office in a city

  23. Microwave Radio - II • Pros: • Analog or digital signals • For voice, data and television signals • Long distance • Cons: • Interference by heavy rain • Straight line transmission • Security • Vendors • Motorola • Rockwell Communication Systems

  24. Satellite - I • Characteristics: • Geosynchronous orbit • Microwave radio transmission • Uplink and downlink • Types • Geosynchronous satellites (22,300 m) • Medium earth orbit (MEO) satellites (6,000 m) • Low earth orbit (LEO) satellite (300 – 1,000 m) • Usages • Direct broadcast satellite (DBS) system for TV broadcasting • Digital satellite service (DSS) for high speed Internet receive-only access • Global telephone systems

  25. Satellite - II • Pros: • Analog or digital signals • For voice, data and television signals • Long distance • Cons: • Security and encryption • Propagation delay

  26. Infrared • Light waves • Line of sight • Wireless communication between nearby equipment

  27. Circuit Ownership • Private circuits • Leased circuits • Bypass • Switched (dial-up) circuits • Selection criteria • Cost, speed, availability, reliability, maintenance, users’ requirements • Others?

  28. Circuit Identification • Blue prints and document circuit and equipment • Circuit number to each circuit for identification

  29. Multiplexing and Concentrating • Time division multiplexing (TDM) • Bit, character, or entire message • Statistical time division multiplexing (STDM) using address field • Frequency division multiplexing (FDM) • Concentrator using buffering and intelligence • Circuit multiplexer • Concentration • Inverse concentration

  30. Circuit Error Conditions • Background noise (electrical phenomenon) • Impulse Noise (spike) • Attenuation • Attenuation distortion • Envelope delay distortion (different propagation delay) • Phase jitter (by carrier signal) • Echo • Crosstalk • Dropouts

  31. Error Prevention • Line conditioning for leased lines reduce • Attenuation (class C) • Envelope delay distortion (class C) • Noise (class D) • Distortion (class D) • Methods • Shielding • Improving connection for cables and connectors • Electronic versus mechanical equipment • Quality • Trouble-free

  32. Error Detection • Echo checking every character • Vertical redundancy checking (VRC) or parity checking • Longitudinal redundancy checking (LRC) or block check character (BCC) • Cyclic redundancy checking (CRC-16) of polynomial error checking

  33. Parity Check Example • Parity BCC • 1 1 1 1 1 1 0 • 0 0 0 0 0 0 0 • 1 0 1 0 1 1 0 • 0 0 0 1 0 1 0 • 0 0 0 0 1 0 1 • 0 0 1 0 0 0 1 • 0 1 0 1 0 1 1 • 0 0 1 1 1 0 1 VRC

  34. Error Correction • Equipment and circuit requirement • Buffer • Reverse channel or channel turn around • Retransmission - automatic repeat request (ARQ) • Methods • Stop and wait ARQ - ACK and NAK: long data block , low error rate, & having a reverse channel • Continuous ARQ: long propagation time • Forward error correction (FEC): simplex transmission • using Hamming code, Hagelbarger code, Bose-Chaudhuri code • High cost (extra bits & codes)

  35. Guidelines for Wiring • 25% more capacity • Internet usage • Two Cat 5 at each desk • Fiber optic cable for backbone • Good wiring contractor • Others?

  36. Future • High-speed digital service • Bandwidth-on-demand

  37. Points to Remember • Definition • Types • Media • Ownership • Error conditions, prevention, and correction

  38. Discussion • Design the communications circuits needs for a bank and state you reasons to insure the security and accuracy

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