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Network Media

Network Media. Network media is the actual path over which an electronic signal travels as it moves from one component to another or one device to another. Numerous transmission media types are used for Data Communication. The choice of medium depends on: -Distance to be covered.

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Network Media

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  1. Network Media • Network media is the actualpath over which an electronic signal travels as it moves from one component to another or one device to another. BIT 1102: Communications Technology & the Internet

  2. Numerous transmission media types are used for Data Communication The choice of medium depends on: -Distance to be covered. -Desired BitRate (in bits per second, bps) -Cost Considerations Generally categorized as: -Guided -Unguided (Wireless). BIT 1102: Communications Technology & the Internet

  3. The Basics of Transmission • The Transmitter generates andencodes data as energy which it (energy) transmits through medium. • Transmitted energy is carried through some a medium • Media can be copper, glass, air, etc BIT 1102: Communications Technology & the Internet

  4. At the destination the energy is decoded back into data (Caustic data). Energy can be electrical, light, radio etc. Note: Each form of energy has differentproperties and requirements for transmission. BIT 1102: Communications Technology & the Internet

  5. Fundamental Limits of Transmission Media i) All channels allow only a limited set of frequencies to be passed. This limit is called bandwidth of that channel. • Bandwidth:Is the data transfer rate - the amount of data that can be carried from one point to another in a given time period (usually a second). • I.e., How much data is allowed to move through a medium usually per second. BIT 1102: Communications Technology & the Internet

  6. Fundamental Limits of Transmission Media cont’d ii) All channels are subject to background noise (noise is unwanted electrical or electromagnetic energy that degrades the quality of signals and data). BIT 1102: Communications Technology & the Internet

  7. Fundamental Limits of Transmission Media cont’d • NB:Sources of noise include: a)crosstalk: A signal on one line is picked up by adjacent lines as a small noise signal – For crosstalk, both cables / wires have the same strength. BIT 1102: Communications Technology & the Internet

  8. b) Near-End Crosstalk (NEXT) • Caused when a strongtransmitter output signalinterferes with a much weaker incoming receiver signal. A strong wire Vs a weak energy wire so, the weak /lower strength cable ie the one with low bandwidth or carrying less data is affected BIT 1102: Communications Technology & the Internet

  9. c)Impulse noise • Caused by externalactivity or equipment which generates electricalimpulses. • Can be caused by voltage spikes in equipment, lightening flashes, during thunderstorms and a wide variety of other phenomenon BIT 1102: Communications Technology & the Internet

  10. Thermal noise (whitenoise): • Caused by the thermal agitation of electrons associated with each atom in the device or transmission line material. • Eg , electrical (“UMEME wire”) running parallel butnear with the telephone wire. So, the thermal signals from the electrical wire might disorganize the telephonewire. BIT 1102: Communications Technology & the Internet

  11. Additional Limitations of Transmission Media cont’d iii) SignalAttenuation: Is the phenomenon whereby the Amplitudeof a signal decreases as it propagates along a transmission line. -Attenuation is a function of distance and frequency of signal -Repeaters are used to increase the power of the signal at appropriate intervals. BIT 1102: Communications Technology & the Internet

  12. Research about- Shannon Channel Capacity BIT 1102: Communications Technology & the Internet

  13. Media Types Two categories a) Guided media. b) Unguided. • Guided Transmission Mediauses a "cabling" system that guides the data signals along a specificpath. The data signals are bound by the "cabling" system. Guided Media • Also known as Bound BIT 1102: Communications Technology & the Internet

  14. Media Types. • Guided Transmission Mediainclude: • Fiber optics • Twisted pair cables • Coaxial cables BIT 1102: Communications Technology & the Internet

  15. 1) Twisted-Pair Cable • Twisted-paircable: Two of wires form a circuit that can transmit data. Cables are twisted to provide protection against crosstalk. • When two wires in an electrical circuit are placed close together, the magnetic fields are the exactopposite of each other. • Thetwo magnetic fieldscancel each other out. They also cancel out any outsidemagneticfields. Twisting the wires can enhance this cancellationeffect. BIT 1102: Communications Technology & the Internet

  16. Twisted pair cable • Can be a) Unshielded Twisted Pair (UTP) b) Shielded Twisted Pair (STP) BIT 1102: Communications Technology & the Internet

  17. a) UTP • Unshielded Twisted Pair: UTP cable is a medium that is composed of pairs of wires. • UTP cable is used in a variety of networks. Each of the eight individual copper wires in UTP cable is covered by an insulating material. BIT 1102: Communications Technology & the Internet

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  19. UTP cont’d • UTP cable relies solely on the cancellation effect produced by the twisted wire pairs to limit signal degradation caused by electromagnetic interference (EMI) and radio frequency interference (RFI). BIT 1102: Communications Technology & the Internet

  20. b) Shielded Twisted-Pair (STP) • Combines the techniques of shielding, cancellation, and wire twisting. Each pair of wires is wrapped in a metallic foil). The four pairs of wires then are wrapped in an overall metallic braid or foil. • Has a cancellation effect and a shield to prevent it from attacks like EMI BIT 1102: Communications Technology & the Internet

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  22. STP UTP BIT 1102: Communications Technology & the Internet

  23. It is rather cost effective in comparison to other technologies like the fiber optic. It is extremely easy to terminate. Its thin and flexible and can be strung around walls More lines can be run through the same connection ducts The general merits of the twisted pair technology BIT 1102: Communications Technology & the Internet

  24. It is prone to external interference. They require many repeaters for relatively long distances which makes it expensive. NB: The twisted pair technology uses A Registered Jack (RJ 45) in connections. THE RJ-45 The demerits of the twisted pair technology BIT 1102: Communications Technology & the Internet

  25. 2) Coaxial Cable • Consists of a hollow outer cylindrical conductor that surrounds a single inner wire made of two conducting elements. One of these elements, located in the center of the cable, is a copperconductor. • NB: e.g. those used on TV sets BIT 1102: Communications Technology & the Internet

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  27. Coaxial cable BIT 1102: Communications Technology & the Internet

  28. Coaxial Cable BIT 1102: Communications Technology & the Internet

  29. 3) Fiber-Optic Cable • Uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glassthreads, each of which is capable of transmitting messages as lightwaves BIT 1102: Communications Technology & the Internet

  30. Parts of fiber optics • Core- Thin glass center of the fiber where the light travels • Cladding- Outer optical material surrounding the core that reflects the light back into the core • Buffer coating- Plastic coating that protects the fiber from damage and moisture BIT 1102: Communications Technology & the Internet

  31. How fiber optics operate • The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called total internal reflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances BIT 1102: Communications Technology & the Internet

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  33. Transmission is through electroluminescence (an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage). • The emitted light is incoherent with a relatively wide spectral width of 30-60 nm. • Receivers- the main component of an optical receiver is a photo-detector that converts light into electric-signal through the photoelectric effect . BIT 1102: Communications Technology & the Internet

  34. Transmitter-the most commonly-used optical transmitters are semiconductor devices such as light-emitting diodes (LEDs) and laser diodes. BIT 1102: Communications Technology & the Internet

  35. Fiber-Optic Cable BIT 1102: Communications Technology & the Internet

  36. Two types of fiber-optic cables a) Single-mode Allows only one mode of light to propagate through the fiber. Capable of higher bandwidth, and it is often used as a backbone - (10kms). BIT 1102: Communications Technology & the Internet

  37. Multimode Multimode fiber cable allows multiple modes of light to propagate through the fiber. It uses light-emitting diodes (LEDs) as a light-generating device (2km) BIT 1102: Communications Technology & the Internet

  38. Advantages • Fibers do not leak light and are quite difficult to tap (Secure). • Handles much higher bandwidth than copper wires. • The loss of signal in optical fiber is less than in copper wire. Repeaters are needed at 30 km Vs 5 for copper. • Not affected by electromagnetic interference. Unlike electrical signals in copper wires, light signals from one fiber do not interfere with those of other fibers in the same cable. BIT 1102: Communications Technology & the Internet

  39. Disadvantages • They are quite difficult to install • Its an expensive technology. Its expensive to install. • Very delicate / fragile. BIT 1102: Communications Technology & the Internet

  40. b) Unguided Media-Wireless Communication • Unguided Transmission Media refers to data signals that flow through the air. They are not guided or bound to a channel to follow. • Unguided media provide a means for transmitting electromagnetic waves but do not guide them; examples are propagation through air, vacuum and sea-water. BIT 1102: Communications Technology & the Internet

  41. Wireless communication • Is the transfer of information over a distance with the use of electromagnetic waves. • Electromagnetic waves are formed when an electric field couples with a magnetic field. BIT 1102: Communications Technology & the Internet

  42. Example of unguided media • Radio wave transmission • Micro wave transmission • Light wave transmission • Infrared and bluetooth BIT 1102: Communications Technology & the Internet

  43. 1. Radio transmission • The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave • There are 3 types of RF (Radio Frequency) Propagation: • Ground Wave, • Ionospheric and • Line of Sight (LOS) Propagation. BIT 1102: Communications Technology & the Internet

  44. Xtics of radio transmission • Easily generated. • Omni-directionally travel a long distance. • Can penetrate buildings. • Frequency dependant. • Relatively low bandwidth for data communication. • Tightly licensed by governments. BIT 1102: Communications Technology & the Internet

  45. i) Ground Wave Propagation • Follows the curvature of the Earth. Ground Waves have carrier frequencies up to 2 MHz. AM radio is an example of Ground Wave Propagation. • Radio, television and micro-waves are types of electromagnetic waves. They differ from each other in wavelength. BIT 1102: Communications Technology & the Internet

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  47. ii) Ionospheric Propagation • Bounces off of the Earths Ionospheric Layer in the upper atmosphere. It is sometimes called Double Hop Propagation. It operates in the frequency range of 30 - 85 MHz BIT 1102: Communications Technology & the Internet

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  49. iii) Line of Sight Propagation • Line of Sight Propagation transmits exactly in the line of sight. The receive station must be in the view of the transmit station. It is sometimes called Space Waves or Tropospheric Propagation. • Examples of Line of Sight Propagation are: FM Radio, Microwave and Satellite. BIT 1102: Communications Technology & the Internet

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