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Chapter Four

Chapter Four. Transmission Basics and Networking Media. Objectives. Explain data transmission concepts including full-duplexing, attenuation, and noise Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media

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Chapter Four

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  1. Chapter Four Transmission Basics and Networking Media

  2. Objectives • Explain data transmission concepts including full-duplexing, attenuation, and noise • Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media • Explain the benefits and limitations of different networking media • Identify the best practices for cabling buildings and work areas • Describe the methods of transmitting data through the atmosphere

  3. Transmission Basics • Transmission has two meanings: • Refers to process of issuing data signals on a medium • Refers to progress of data signals over a medium • On a data network, information can be transmitted via one of two methods: • Analog • Digital

  4. Transmission Basics • Both analog and digital signals are generated by electrical current, pressure of which is measured in volts • In analog signals, voltage varies continuously • In digital signals, voltage turns off and on repeatedly

  5. Transmission Basics Analog signal Signals 0 and 1 are transmitted as electric waves. Digital signalsCode 1 is transmitted when applying a specific voltage and code 0 is transmitted in the case of 0V.. Figure 4-1: Example of an analog and digital signal

  6. Transmission Basics • Amplitude • Measure of a signal’s strength • Frequency • Number of times a signal’s amplitude changes over a period of time • Expressed in hertz (Hz) • Wavelength • Distances between corresponding points on a wave’s cycle

  7. Transmission Basics • Phase • Refers to progress of a wave over time in relationship to a fixed point Figure 4-2: Phase differences

  8. Transmission Basics Figure 4-3: A complex analog signal representing human speech

  9. Transmission Basics • Binary system encodes using 1s and 0s • Bits= binary signal (1 or 0) • 8bits = 1byte • Noise or any interference that may degrade signals affects digital signals less than analog signals

  10. Transmission Basics Figure 4-4: Example of a digital signal

  11. Data Modulation • Modem • Name reflects function as modulator/demodulator • Modulation • Technique for formatting signals • Frequency modulation (FM) • Method of data modulation in which frequency of carrier signal is modified by application of a data signal • Amplitude modulation (AM) • Modulation technique in which amplitude of carrier signal is modified by application of a data signal

  12. Data Modulation Figure 4-5: A carrier wave modified by frequency modulation

  13. Transmission Direction • Simplex • Signals travel in only ONE direction • Half-duplex • Signals may travel in BOTH directions over a medium BUTin only one direction at a time • Full-duplex • Signals are free to travel in BOTH directions over a medium simultaneously • Also referred to just as duplex

  14. Transmission Direction • Channel • Distinct communication path between two or more nodes Figure 4-6: Simplex, half-duplex, and full-duplex transmission

  15. Simplex, half-duplex, and full-duplex communication

  16. Transmission Direction • Multiplexing • Allows multiple signals to travel simultaneously over one medium • To accommodate multiple signals, single medium is logically separated into subchannels • For each type of multiplexing: • Multiplexer (mux) is required at sending end of channel • Demultiplexer (demux) separates the combined signals and regenerates them in original form

  17. Multiplexer & Demultiplexer

  18. Transmission Direction • Time division multiplexing (TDM) • Divides channel into multiple intervals of time Figure 4-7: Time division multiplexing

  19. Transmission Direction • Wavelength division multiplexing (WDM) • Used only with fiber-optic cable • Data is transmitted as pulses of light • Fiber-optic modem (FOM)is a demultiplexer used on fiber networks that employ WDM Figure 4-9: Wavelength division multiplexing

  20. Relationships Between Nodes • Point-to-point • Transmission involving 1transmitter and 1 receiver • Broadcast • Transmission involving 1transmitter and multiplereceivers

  21. Point-to-point TRANSMISSION Broadcast TRANSMISSION

  22. Relationships Between Nodes Figure 4-10: Point-to-point versus broadcast transmission Point-to-point versus broadcast transmission

  23. Throughput and Bandwidth • Throughput is amount of data the medium can transmit during a given period of time • Also called capacity.Unit = bit/s • Bandwidthmeasures difference between highest and lowest frequencies a media can transmit.Unit = Hz/Mhz. • Range of frequencies is directly related to throughput

  24. Transmission Flaws • NOISE a) Electromagnetic interference (EMI) • Interference that may be caused by motors, power lines, television, copiers, fluorescent lights, or other sources of electrical activity b) Radiofrequency interference (RFI) • Interference that may be generated by motors, power lines, televisions, copiers, fluorescent lights, or broadcast signals from radio or TV towers c) Crosstalk signal traveling on a wire or cable infringes on signal traveling over adjacent wire or cable

  25. Transmission Flaws Noise random background mixed up with your signal Ex: switch on radio + ‘hiss sound’ Unit = dB Figure 4-11: An analog signal distorted by noise

  26. Transmission Flaws Figure 4-12: A digital signal distorted by noise

  27. Transmission Flaws • Attenuation - for analogue signal • Loss of signal strength as transmission travels away from source • Analogue signals pass through an amplifier, which increases not only voltage of a signal but also noise accumulated To strengthen analogue signals :An analog signal distorted by noise, and then amplified

  28. Transmission Flaws Attenuation - for digital signal • Regeneration • Process of retransmitting a digital signal • Repeater • Device used to regenerate a signal A digital signal distorted by noise, and then repeated

  29. Question??? What is the different between noise and attenuation???

  30. Latency • Delay between transmission and receipt of a signal • Causes: a) Media delays may be caused by the finite speed that signals can travel through the physical media(propagation delay) b) Circuits delay may be caused by the electronics that process along the path. c) Software delays maybe caused by the decisions that software must make to implement switching & protocols.

  31. TRANSMISSION MEDIACoaxial Cable • Consists of central copper core surrounded by an insulator, braiding, and outer cover called a sheath • (protective covering) Coaxial cable

  32. Coaxial Cable Some types of coaxial cable

  33. Thicknet (10Base5) • Also called thickwireEthernet • Rigid coaxial cable used on original Ethernet networks • IEEE designates Thicknet as 10Base5Ethernet • Almost never used on new networks but you may find it on older networks • Used to connect one data closet to another as part of network backbone

  34. Thicknet Characteristics • Throughput • According to IEEE 802.3, Thicknet transmits data at maximum rate of 10 Mbps • Cost • Less expensive than fiber-optic but more expensive than some other types of coaxial cable • Connector • Can include a few different types of connectors, which are very different from those used on modern networks

  35. Thicknet Characteristics • N-series connector (or n connector) • Screw-and-barrel arrangement securely connects coaxial cable segments and devices N-Series connector

  36. Thicknet Characteristics • Noise immunity • Because of its wide diameter and excellent shielding, has the highest resistance to noise of any commonly used types of network wiring • Size and scalability • Because of its high noise resistance, it allows data to travel longer than other types of cabling

  37. Thinnet (10Base2) • Also known as thin Ethernet • Characteristics: • Throughput • Can transmit at maximum rate of 10 Mbps • Cost • Less expensive than Thicknet and fiber-optic cable • More expensive than twisted-pair wiring • Connectors • Connects wire to network devices with BNC T-connectors • A seen in Figure 4-19, BNC barrel connectors are used to join two Thinnet cable segments together

  38. Thinnet (10Base2) • Characteristics (cont.): • Size and scalability • Allows a maximum of 185 m per network segment (see Figure 4-20) • Noise immunity • More resistant than twisted-pair wiring • Less resistant than twisted-pair wiring ThinnetBNC connectors

  39. Thinnet (10Base2) • Signal bounce • Caused by improper termination on a bus network • Travels endlessly between two ends of network • Prevents new signals from getting through A 10Base2 Ethernet network

  40. Twisted-Pair (TP) Cable • Color-coded pairs of insulated copper wires twisted around each other and encased in plastic coating • Twists in wire help reduce effects ofcrosstalk • Number of twists per meter or foot known as twist ratio • Alien Crosstalk • When signals from adjacent cables interfere with another cable’s transmission Twisted-pair cable

  41. Shielded Twisted-Pair (STP) • STP cable consists of twisted wire pairs that are individually insulated and surrounded by shielding made of metallic substance STP cable

  42. Unshielded Twisted-Pair • Consists of one or more insulated wire pairs encased in a plastic sheath • Does not contain additional shielding UTP cable

  43. Unshielded Twisted-Pair • To manage network cabling, it is necessary to be familiar with standards used on modern networks, particularly Category 3 (CAT3) and Category 5 (CAT5) A CAT5 UTP cable

  44. Use for voice communication • Most often use for phone line • Used for Data Transmission • Individual pairs are wrapped in a • shield & then entire 4 pairs • wrapped in another shield. • Supports 1000 Mbps – 10Gbps • Used for Data Transmission • An added separator is between • each pair of wires allowing it to • function at higher speed. • Supports 1000 Mbps – 10Gbps • Used for Data Transmission • Cat 5 support 100Mbps • Cat 5e support 1000Mbps

  45. Comparing STP and UTP • Throughput • Both can transmit up to 100 Mbps • Cost • Typically, STP is more expensive • Connector • Both use RJ-45 connectors (see Figure 4-27) and data jacks • Noise immunity • STP is more noise-resistant • Size and scalability • Maximum segment length for both is 100 meters

  46. RJ-45 Connector An RJ-45 connector

  47. Fiber-Optic Cable • Contains one or several glass fibers at its core • Surrounding the fibers is a layer of glass called cladding A fiber-optic cable Front view

  48. Fiber-Optic Cable • Single-mode fiber • Carries light pulses along single path Single-mode fiber-optic cables

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