1. CE 4228 DATA COMMUNICATIONS AND NETWORKING Transmission Media

2. Transmission Media – Outline Guided media Twisted pair Coaxial cable Optical fiber Unguided media Antenna Propagation

3. Transmission Media – Design Key concerns are data rate and distance Bandwidth Higher bandwidth gives higher data rate Transmission impairments Attenuation Interference Number of receivers In guided media More multi-point receivers introduce more attenuation

4. Transmission Media – Guided Twisted pair Coaxial cable Optical fiber

5. Twisted Pair (a) Category 3 UTP (b) Category 5 UTP

6. Twisted Pair – Rationale

7. Twisted Pair – Applications Most common medium Telephone networks Between house and local exchange Subscriber loop Within buildings To private branch exchange or PBX Local area networks

8. Twisted Pair – Characteristics Analog Amplifiers every 5 to 6 km Digital Use either analog or digital signals Repeater every 2 or 3 km Limited distance Limited bandwidth Limited data rate Susceptible to interference and noise

9. Twisted Pair – UTP/STP UTP Unshielded twisted pair Ordinary telephone wire Cheapest Easiest to install Suffer from external EM interference STP Shielded twisted pair Metal braid or sheathing that reduces interference More expensive Thick, heavy Harder to handle

10. Twisted Pair – UTP Category 3 Up to 16 MHz Voice grade found in most offices Twist length of 7.5 cm to 10 cm Category 4 Up to 20 MHz Category 5 Up to 100 MHz Commonly pre-installed in new office buildings Twist length 0.6 cm to 0.85 cm Category 5e Enhanced Category 6 Category 7

11. Twisted Pair – Categories

12. TelephoneCategory 3Category 5eCategory 6

13. Twisted Pair – Category 6 UTP

14. Twisted Pair – Categories/Classes Category 3 Class C Category 5 Class D Category 5E Category 6 Class E Category 7 Class F Bandwidth16 MHz100 MHz 200 MHz600 MHz Cable TypeUTPUTP/FTP SSTP Link Cost0.711.21.52.2

15. Twisted Pair – Comparison Attenuation (dB per 100 m)Near-end Crosstalk (dB) Frequency (MHz) Category 3 UTP Category 5 UTP 150-ohm STP Category 3 UTP Category 5 UTP 150-ohm STP 12.62.01.1416258 45.64.12.2325358 1613.18.24.4234450.4 25—10.46.2—4147.5 100—22.012.3—3238.5 300——21.4——31.3

16. Twisted Pair – Summary Cheap Easy to work with Low data rate Short range

17. Coaxial Cable 75-ohm cable is widely used Impedance easily matched with 300- ohm antenna 50-ohm cable is sometimes used when intended for digital transmission from the start

18. Coaxial Cable – Applications Most versatile medium Television distribution Aerial to TV Cable TV Long distance telephone transmission Can carry 10,000 voice calls simultaneously Being replaced by fiber optic Short distance computer systems links Local area networks

19. Coaxial Cable – Characteristics Analog Amplifiers every few km, closer if higher frequency Up to 500 MHz Digital Repeater every 1 km, closer for higher data rates 500 Mbps or higher For comparison 6 MHz/TV channel 1.4 Mbps for CD

20. Optical Fiber

23. Optical Fiber – Applications Long-haul trunks Metropolitan trunks Rural exchange trunks Subscriber loops LANs

24. Optical Fiber – FTTH

25. Optical Fiber – Characteristics Act as wave guide for 10 14 to 10 15 Hz Portions of infrared and visible spectrum Theoretical bandwidth of 50 Tbps Practical data rate of 2 Gbps Speed/distance limited by dispersion Two types of light source LED Light emitting diode ILD Injection laser diode Wavelength division multiplexing

26. Optical Fiber – Light Source

27. Optical Fiber – Modes

28. Optical Fiber – Dispersion

29. Define the following D = dispersion rate in s/km Pulse width increased/distance Depend on types of fiber R = bit rate in bps L = length of fiber in km Sending 101010… L×D ≤ T/2 → R×L ≤ 1/2D Hence, R×L must be less than 10 Mbps × km for a step-index fiber 1 Gbps × km for a graded-index fiber 200 Gbps × km for a single-mode fiber

30. Wavelength range (nm) Frequency range (THz) Band label Fiber typeApplication 820 to 900366 to 333 MultimodeLAN 1280 to 1350234 to 222SSingle modeVarious 1528 to 1561196 to 192CSingle modeWDM 1561 to 1620192 to 185LSingle modeWDM Optical Fiber – Frequency Range

31. Optical Fiber – Frequency Band

32. Optical Fiber – Benefits Greater capacity Data rates of hundreds of Gbps Smaller size & weight Lower attenuation Electromagnetic isolation Can be operated for communications and control networks in close proximity to electrical circuits without problems Greater repeater spacing 10 km or more

33. Guided Media – Characteristics Frequency Range Typical Attenuation Typical DelayRepeater Spacing Twisted pair (with loading) 0 to 3.5 kHz0.2 dB/km @ 1 kHz 50 µs/km2 km Twisted pairs (multi-pair cables) 0 to 1 MHz0.7 dB/km @ 1 kHz 5 µs/km2 km Coaxial cable0 to 500 MHz7 dB/km @ 10 MHz 4 µs/km1 to 9 km Optical fiber186 to 370 THz0.2 to 0.5 dB/km 5 µs/km40 km

34. Guided Media – Characteristics

35. Guided Media – Attenuation

36. Electromagnetic Spectrum

38. Wireless – Frequency Band

39. Radio 10 kHz to 1 GHz Omnidirectional Broadcast radio Infrared 3×10 11 to 2×10 14 Hz Local Microwave 1 GHz to 40 GHz Highly directional Point to point Satellite

40. Wireless – ISM Band Industrial, scientific, medical Unlicensed usage Low power only, to avoid interference Garage door openers, cordless phones, wireless mice, wireless LANs, Bluetooth

41. Wireless Unguided transmission media Several reasons of usages Mobility Accessibility Modern wireless digital communications began in Hawaii, where conventional landline system was inadequate

42. Antenna Transmissions Radio frequency energy from transmitter Converted to electromagnetic energy by antenna Radiated into surrounding environment Receptions Electromagnetic energy impinging on antenna Converted to radio frequency electrical energy Fed to receiver Same antenna often used for both

43. Antenna – Radiation Pattern Power radiated in all directions Not same performance in all directions Isotropic antenna is theoretical point in space Radiate in all directions equally Give spherical radiation pattern

44. Antenna – Parabolic Reflective Used for terrestrial and satellite microwave Parabola is locus of point equidistant from a line and a point not on that line Fixed point is focus Line is directrix Revolve parabola about axis to get paraboloid Cross section parallel to axis gives parabola Cross section perpendicular to axis gives circle

45. Antenna – Parabolic Reflective Source placed at focus will produce waves reflected from parabola in parallel to axis Creates theoretical parallel beam of light/sound/radio On reception, signal is concentrated at focus, where detector is placed

46. Antenna – Parabolic Reflective

47. Antenna – Gain Measure of directionality of antenna Power output in particular direction compared with that produced by isotropic antenna Measured in dB Result in loss in power in another direction Effective area relates to size and shape Related to gain

48. Terrestrial Microwave Parabolic dish Focused beam Line of sight Higher frequencies give higher data rates Long haul telecommunications A microwave tower every 50 km

49. Satellite Satellite is relay station Satellite receives on one frequency, amplifies or repeats signal and transmits on another frequency Inherently broadcast media Can be deployed almost instantly Military Cost of transmitting is independent of the distance

50. Satellite Geostationary orbit Height of 35,784 km Relatively large propagation delay Typical value is 270 msec 3 μsec/km for terrestrial microwave 5 μsec/km for coaxial cable or optical fiber Television Long distance telephone Private business networks

51. Satellite – Frequency Band

52. Satellite – Altitude

53. Satellite – Point to Point Link

54. Satellite – Broadcast Link

55. Satellite – VSAT

56. Broadcast Radio Omnidirectional FM radio UHF and VHF television Line of sight Suffer from multipath interference Reflections

57. Infrared Modulate noncoherent infrared light Line of sight or reflection Blocked by walls TV remote control, IrDA port Point to point

58. Cellular System Replace high power transmitter/receiver systems Use lower power, shorter range, more transmitters Area divided into cells Adjacent cells on different frequencies to avoid crosstalk Frequency reuse Hexagonal cells Most resemble to circular shape Can be packed without hole

59. Cellular System – Cells

60. Cellular System – Design Factor Fading Time variation of received signal, caused by changes in transmission paths Multiple access FDMA TDMA CDMA Handoff Base station location

61. Cellular System – Signal Strength

63. Wireless – Propagation Signal travels along three routes Ground wave Sky wave Line of sight

64. Wireless – Ground Wave Frequency less than 2 MHz Follow contour of the earth AM radio

65. Wireless – Sky Wave Frequency of 2-30 MHz BBC world, Voice of America, amateur radio Signal reflected, or actually refracted, from ionosphere layer

66. Wireless – Line of Sight Frequency above 30 MHz May be further than optical line of sight due to refraction

67. Wireless – Refraction Velocity of electromagnetic wave is a function of density of material 3×10 8 m/s in vacuum, less in anything else As wave moves from one medium to another, its speed changes Direction bending of wave at boundary Towards more dense medium Index of refraction sin(angle of incidence)/sin(angle of refraction) Vary with wavelength Also called refractive index

68. Wireless – Refraction May cause sudden change of direction at transition between media May cause gradual bending if medium density is varying Density of atmosphere decreases with height Result in bending towards earth of radio waves

69. Wireless – Impairment Free space loss Signal disperses with distance Greater for higher frequencies But consider antenna gain that can compensate, higher frequencies are better Atmospheric absorption Water vapour and oxygen absorb radio signals Water greatest at 22 GHz, less below 15 GHz Oxygen greatest at 60 GHz, less below 30 GHz Rain and fog scatter radio waves

70. Wireless – Impairment Multipath Better to get line of sight if possible Signal can be reflected causing multiple copies to be received May be no direct signal at all May reinforce or cancel direct signal Refraction May result in partial or total loss of signal at receiver

71. Wireless Free space loss

72. Wireless – Multipath Interference

73. Transmission Media – Conclusion Guided Unguided Understanding the properties