1 Kyung Hee University Transmission Media

2 Kyung Hee University 7 장 Transmission media o Transmission medium and physical layer

3 Kyung Hee University Transmission media( 전송매체 ) 7.1 Guided Media( 유도매체 ) 7.2 Unguided media( 비유도매체 ) : Wireless

4 Kyung Hee University Transmission Media(cont’d) ~ Can be divided into two broad categories : 유도매체, 비 유도매체 oClasses of transmission media

5 Kyung Hee University 7.1 Guided Media( 유도매체 ) o Twisted-Pair Cable two copper conductors one carries signals, the other is the ground reference interference may affect both wires receiver operates on the difference between the signals this is why they are twisted, to maintain balance more twists mean better quality

6 Kyung Hee University 유도매체 (cont’d) oTwisted-Pair Cable ~ comes in two forms : unshielded ( 비차폐 ) and shielded( 차폐 ) oUTP(Unshielded Twisted-Pair) Cable ~ is the most common type of telecommunication medium in use today. oFrequency range for twisted-pair cable

7 Kyung Hee University 유도매체 (cont’d) oTwisted-Pair Cable consists of two conductors (usually copper), each with its own colored plastic insulation Color-banded for identification PVC : polyvinyl chloride two copper conductors one carries signals, the other is the ground reference interference may affect both wires receiver operates on the difference between the signals this is why they are twisted, to maintain balance more twists mean better quality

8 Kyung Hee University 유도매체 (cont’d) oEffect of noise on parallel lines

9 Kyung Hee University 유도매체 (cont’d) oEffect of noise on twisted-pair lines

10 Kyung Hee University 유도매체 (cont’d) oAdvantage of UTP cheap, flexible, and easy to install. 2 ~ 12 twists per foot oCable with 5 unshielded twisted pairs of wires

11 Kyung Hee University 유도매체 (cont’d) oUTP standards has developed to grade by quality CategoryBandwidthData RateDigital/AnalogUse 1very low< 100 kbpsAnalogTelephone 2 < 2 MHz2 MbpsAnalog/digitalT-1 lines 3 16 MHz 10 MbpsDigitalLANs 4 20 MHz 20 MbpsDigitalLANs MHz 100 MbpsDigitalLANs 6 (draft) 200 MHz 200 MbpsDigitalLANs 7 (draft) 600 MHz 600 MbpsDigitalLANs

12 Kyung Hee University 유도매체 (cont’d) oUTP connectors RJ – Registered Jack keyed connector, can be inserted one way

13 Kyung Hee University Performance

14 Applications of UTP o telephone lines for voice and data o DSL o LAN – 10Base-T and 100Base-T

15 Kyung Hee University 유도매체 (cont’d) oSTP(Shielded Twisted-Pair) cable has the same quality consideration as UTP (more expensive, less susceptible to noise) l eliminating most of the effects of crosstalk

16 Kyung Hee University 유도매체 (cont’d) o 동축 케이블 (Coaxial Cable) carries signals of higher frequency ranges oFrequency range of coaxial cable

17 Kyung Hee University 유도매체 (cont’d) oCoaxial cable

18 Kyung Hee University 유도매체 (cont’d) oCoaxial Cable Standards ~ are categorized by RG(radio government) rating CategoryImpedanceUse RG  Cable TV RG  Thin Ethernet RG-1150  Thick Ethernet

19 Kyung Hee University 유도매체 (cont’d) o Coaxial Cable Connectors

20 Kyung Hee University 유도매체 (cont’d) o Performance

21 Kyung Hee University 유도매체 (cont’d) o Applications Cable TV traditional Ethernet LANs, 10Base-2, 10Base-5

22 Kyung Hee University 유도매체 (cont’d) oOptical Fiber( 광섬유 ) ~ is made of glass or plastic and transmits signals in the form of light oNature 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.

23 Kyung Hee University 유도매체 (cont’d) o 굴절 (Refraction)

24 Kyung Hee University 유도매체 (cont’d) o 임계각 (critical angle) As the angle of incidence( 입사각 ) increase, it moves away from vertical and closer to the horizontal.

25 Kyung Hee University 유도매체 (cont’d) o 반사 (Reflection) When the angle of incidence becomes greater than the critical angle, a new phenomenon occurs called reflection

26 Kyung Hee University 유도매체 (cont’d) o Optical Fiber

27 Kyung Hee University 유도매체 (cont’d) oPropagation Models current technology supports two models for propagating light along optical channel.

28 Kyung Hee University 유도매체 (cont’d) oMultimode step-index ~ multiple beams from a light source move through the core in different paths.

29 Kyung Hee University 유도매체 (cont’d) oMultimode graded-index fiber with varying densities highest density at the center of the core

30 Kyung Hee University 유도매체 (cont’d) oSingle 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.

31 Kyung Hee University 유도매체 (cont’d) oFiber sizes ~ are defined by the ratio of the diameter of their core to the diameter of their cladding. Fiber Type Core(microns)Cladding(microns) 62.5/125 50/ / /

32 Kyung Hee University 유도매체 (cont’d) oCable 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

33 Kyung Hee University 유도매체 (cont’d) o Cable Composition

34 Kyung Hee University 유도매체 (cont’d) o Applications of Fiber-optic network backbones cable TV LANs, 100Base-FX, 1000Base-X

35 Kyung Hee University 유도매체 (cont’d) oFiber-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.

36 Kyung Hee University 유도매체 (cont’d) o Fiber-optic Cable Composition

37 Kyung Hee University 유도매체 (cont’d) o Optical Fiber Performance

38 Kyung Hee University 유도매체 (cont’d) oAdvantages of Optical Fiber Noise resistance Less signal attenuation Higher bandwidth oDisadvantages of Optical Fiber Cost Installation/maintenance Fragility

39 Kyung Hee University 7.2 비유도 매체 (Unguided media) owireless osignals are broadcasted through air

40 Kyung Hee University 비유도 매체 (cont’d) oRadio Frequency Allocation 대류층전리층

41 Kyung Hee University 비유도 매체 (cont’d) oPropagation of radio waves Types of propagation

42 Kyung Hee University 비유도 매체 (cont’d) o Type of propagation Surface Propagation l Radio waves travel through the lowest portion of the atmosphere( 대기권 ) Tropospheric ( 대류권 ) Propagation l 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)

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

44 Kyung Hee University 비유도 매체 (cont’d) BandRangePropagationApplication VLF3–30 KHzGroundLong-range radio navigation LF30–300 KHzGround Radio beacons and navigational locators MF300 KHz–3 MHzSkyAM radio HF3–30 MHzSky Citizens band (CB), ship/aircraft communication VHF30–300 MHz Sky and line-of-sight VHF TV, FM radio UHF300 MHz–3 GHzLine-of-sight UHF TV, cellular phones, paging, satellite SHF3–30 GHzLine-of-sightSatellite communication EHF30–300 GHzLine-of-sightLong-range radio navigation

45 Kyung Hee University 비유도 매체 (cont’d) o Wireless Transmission Waves

46 Kyung Hee University 비유도 매체 (cont’d) o Omnidirectional antennas

47 Kyung Hee University 비유도 매체 (cont’d) Radio waves are used for multicast communications, such as radio and television, and paging systems.

48 Kyung Hee University 비유도 매체 (cont’d) oTerrestrial 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

49 Kyung Hee University 비유도 매체 (cont’d) oRepeaters To increase the distance served by terrestrial microwave, a system of repeaters can be installed with each antenna.

50 Kyung Hee University 비유도 매체 (cont’d) o Antennas two types of antenna ¬ Parabolic dish is based on the geometry of a parabola

51 Kyung Hee University 비유도 매체 (cont’d) ­ Horn antenna looks like a gigantic scoop

52 Kyung Hee University 비유도 매체 (cont’d) oSatellite Communication is much like line of sight microwave transmission in which one of the station is a satellite orbiting the earth

53 Kyung Hee University 비유도 매체 (cont’d) oGeosynchronous (geostationary) the view from the North Pole

54 Kyung Hee University 비유도 매체 (cont’d) oFrequency bands for satellite communication ` BandDownlinkUplink C Ku Ka GHz GHz GHz GHz GHz GHz

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

56 Kyung Hee University Cellular and PCS telephony o 서비스 별 비교 항목 IS-95AIS-95BIS-95C(CDMA2000 1X)IMT2000(MC3X) 주파수대역셀룰러 800MHz 대역, PCS 1.7 ~ 1.8GHz 1.9 ~ 2.1GHz 단말기 대기시간 1( 기준 ) 1.3~ 이상 데이터 속도 14.4Kbps64Kbps144Kbps384Kbps ~ 2Mbps A4 100 장 전송 55 초 12 초 6 초 2.5 초 미만 동영상통화불 가불 가가 능가 능 IS : Interim Standard

57 Kyung Hee University Wireless Transmission o Radio waves are used for multicast communications, such as radio and television, and paging systems oMicrowaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs. o Infrared signals can be used for short-range communication in a closed area using line-of- sight propagation