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Transmission Media

Transmission Media. Prof. Choong Seon HONG. 7 장 Transmission media( 전송매체 ). 7.1 Guided Media( 유도매체 ) 7.2 Unguided media( 비유도매체 ) 7.3 Performance( 성능 ). Transmission Media(cont’d). ~ Can be divided into two broad categories : 유도매체 , 비 유도매체 Classes of transmission media.

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Transmission Media

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  1. Transmission Media Prof. Choong Seon HONG

  2. 7 장 Transmission media(전송매체) 7.1 Guided Media(유도매체) 7.2 Unguided media(비유도매체) 7.3 Performance(성능)

  3. Transmission Media(cont’d) ~ Can be divided into two broad categories : 유도매체, 비 유도매체 • Classes of transmission media

  4. 7.1 Guided Media(유도매체) • Categories of guided media

  5. 유도매체(cont’d) • Twisted-Pair Cable ~ comes in two forms : unshielded (비차폐) and shielded(차폐) • UTP(Unshielded Twisted-Pair) Cable ~ is the most common type of telecommunication medium in use today. • Frequency range for twisted-pair cable

  6. Color-banded for identification PVC : polyvinyl chloride 유도매체(cont’d) • Twisted-Pair Cable ~ consists of two conductors (usually copper), each with its own colored plastic insulation.

  7. 유도매체(cont’d) • Effect of noise on parallel lines

  8. 유도매체(cont’d) • Effect of noise on twisted-pair lines

  9. 유도매체(cont’d) • Advantage of UTP • cheap, flexible, and easy to install. • 2 ~ 12 twists per foot • Cable with 5 unshielded twisted pairs of wires

  10. 유도매체(cont’d) • UTP standards has developed to grade by quality • Category 1 : basic twisted-pair cabling (telephone systems) • Category 2 : suitable for voice and for digital data transmission of up to 4 Mbps • Category 3 : used for data transmission of up to 10 Mbps (now standard cable) • Category 4 : possible transmission rate to 16Mbps • Category 5 : used for data transmission up to 100Mbps

  11. 유도매체(cont’d) • UTP connectors • a type of snap-in plus like that used with telephone jacks.

  12. 유도매체(cont’d) • STP(Shielded Twisted-Pair) cable • has the same quality consideration as UTP (more expensive, less susceptible to noise) • eliminating most of the effects of crosstalk

  13. 유도매체(cont’d) • 동축 케이블(Coaxial Cable) • carries signals of higher frequency ranges • Frequency range of coaxial cable

  14. 유도매체(cont’d) • Coaxial cable

  15. 유도매체(cont’d) • Coaxial Cable Standards ~ are categorized by RG(radio government) rating • RG-8 (used in Thick Ethernet) • RG-9 (used in Thick Ethernet) • RG-11 (used in Thick Ethernet) • RG-58 (used in Thin Ethernet) • RG-75 (used for TV)

  16. 유도매체(cont’d) • Optical Fiber(광섬유) ~ is made of glass or plastic and transmits signals in the form of light • Nature of Light ~ is a form of electromagnetic energy. It travels at its fastest in a vacuum : 300,000km/s. This speed decreases as the medium through which the light travels become denser.

  17. 유도매체(cont’d) • 굴절(Refraction) * Fiber-optic technology takes advantage of the properties shown in Figure 7.13b to control the propagation of light through the fiber channel.

  18. 유도매체(cont’d) • 임계각(critical angle) • As the angle of incidence(입사각) increase, it moves away from vertical and closer to the horizontal.

  19. 유도매체(cont’d) • 반사(Reflection) • When the angle of incidence becomes greater than the critical angle, a new phenomenon occurs called reflection

  20. 유도매체(cont’d) • Propagation Model • current technology supports two models for propagating light along optical channel.

  21. 유도매체(cont’d) • Multimode step-index ~ multiple beams from a light source move through the core in different paths.

  22. 유도매체(cont’d) • Multimode graded-index • fiber with varying densities • highest density at the center of the core

  23. 유도매체(cont’d) • Single Mode ~ uses step-index fiber and a highly focused source of light that limits beams to a small range of angles, all close to the horizontal.

  24. Fiber Type Core(microns) Cladding(microns) 62.5/125 50/125 100/140 8.3/125 62.5 50 100 8.3 125 125 140 125 유도매체(cont’d) • Fiber sizes ~ are defined by the ratio of the diameter of their core to the diameter of their cladding.

  25. 유도매체(cont’d) • Cable Composition • Fiber can be made of either glass or plastic • Inner core must be ultrapure and completely regular in size and shape • Outer jacket can be made Teflon coating, plastic coating, fibrous plastic, metal tubing, and metal mesh

  26. 유도매체(cont’d) • Light Sources for optical label • LED(Light-Emitting Diode) : Short distance • ILD(Injection Laser Diode) : Long distance

  27. 유도매체(cont’d) • Fiber-Optic Connectors • must be as precise as the cable itself. • All of the popular connector are barrel(원통) shaped and come in male and female versions.

  28. 유도매체(cont’d) • Advantages of Optical Fiber • Noise resistance • Less signal attenuation • Higher bandwidth • Disadvantages of Optical Fiber • Cost • Installation/maintenance • Fragility

  29. 7.2 비유도 매체(Unguided media) • wireless • signals are broadcasted through air

  30. 비유도 매체(cont’d) • Radio Frequency Allocation 대류층 전리층

  31. 비유도 매체(cont’d) • Propagation of radio waves • Types of propagation

  32. 비유도 매체(cont’d) • Type of propagation • Surface Propagation • Radio waves travel through the lowest portion of the atmosphere(대기권) • Tropospheric (대류권) Propagation • can work two ways( signal can be directed in a straight line from antenna to antenna.  It can be broadcast at an angle into the upper layers of troposphere where it is reflected back down to the earth’s surface)

  33. 비유도 매체(cont’d) • Ionospheric (전리층) Propagation • High-frequency radio waves radiate upward into the ionosphere where they are reflected back to earth • Line-of-Sight Propagation • Very high frequency signals are transmitted in straight lives directly from antenna to antenna • Space Propagation • Utilizes satellite relays in place of atmospheric refraction

  34. 비유도 매체(cont’d) • Propagation of Specific Signals • The type of propagation used in radio transmission depends on the frequency(speed) of the signal • VLF(Very Low Frequency) • is propagated as surface waves, usually through air but sometimes through seawater • is used mostly for long-range radio navigation and for submarine communication

  35. 비유도 매체(cont’d) • LF(Low Frequency) • is also propagated as surface waves • is used for long-range radio navigation and for radio beacons or navigation locators

  36. 비유도 매체(cont’d) • MF(Middle Frequency) • is propagated in the troposphere(대류권) • is absorbed by the ionosphere • uses for MF transmissions include AM radio, maritime radio, radio direction finding(RDF), and emergency frequencies

  37. 비유도 매체(cont’d) • HF(High-Frequency) • uses ionospheric propagation • uses of for HF signals include amateur radio(ham radio), CB(Citizen’s band) radio, international broadcasting, military communication, long-distance aircraft and ship communication, telephone, telegraph, and facsimile

  38. 비유도 매체(cont’d) • VHF(Most Very High Frequency) • uses line-of-sight propagation • uses for VHF include VHF television, FM radio, aircraft AM radio, and aircraft navigational aid

  39. 비유도 매체(cont’d) • UHF(Ultrahigh Frequency) • always uses line-of-sight propagation. • Uses for UHF include UHF television, mobile telephone, cellular radio, paging , and micro wave links

  40. 비유도 매체(cont’d) • SHF(SuperHigh Frequency) ~ are transmitted using mostly line-of-sight and some space propagation. ~ uses for SHF include terrestrial and satellite microwave, and radar communication

  41. 비유도 매체(cont’d) • EHF(Extremely High Frequency) • use space propagation • uses for EHF are radar, Satellite, and experimental communication

  42. 비유도 매체(cont’d) • Terrestrial microwaves • require line-of-sight transmission and reception equipment. The distance coverable by a line-of-sight signal depends on a large extent on the height of the antenna : the taller the antenna, the longer the sight distance

  43. 비유도 매체(cont’d) • Repeaters • To increase the distance served by terrestrial microwave, a system of repeaters can be installed with each antenna.

  44. 비유도 매체(cont’d) • Antennas • two types of antenna • Parabolic dish • is based on the geometry of a parabola

  45. 비유도 매체(cont’d) • Horn antenna • looks like a gigantic scoop

  46. 비유도 매체(cont’d) • Satellite Communication • is much like line of sight microwave transmission in which one of the station is a satellite orbiting the earth

  47. 비유도 매체(cont’d) • Geosynchronous (geostationary) satellites @ the view from the North Pole

  48. ` Band Downlink Uplink 03.7 - 04.2 GHz 11.7 - 12.2 GHz 17.7 - 21.0 GHz C Ku Ka 05.925 - 06.425 GHz 14.000 - 14.500 GHz 27.500 - 31.000 GHz 비유도 매체(cont’d) • Frequency bands for satellite communication

  49. 비유도 매체(cont’d) • Cellular telephony • is designed to provide stable communications connections between two moving device or between one mobile unit and one stationary(land) unit.

  50. Cellular and PCS telephony • 서비스 별 비교 IS : Interim Standard

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