different types of transmission media(wired/wireless)

different types of media

1. Transmission Media 1

2. Transmission Media 2

3. Transmission Media Transmission medium the physical path between transmitter and receiver. Transmission media operates at Physical Layer of the OSI Model. Computers and other telecommunication devices use signal to represent data. Repeaters or amplifiers may be used to extend the length of the medium. 3

4. Transmission Media 4

5. GUIDED MEDIA 5

6. TWISTED-PAIR Twisted-pair cable uses metallic (copper) conductors that accept and transport signals in the form of electric current . Twisted pair cables consist of one or more pairs of insulated copper wires that are twisted together and housed in a protective jacket. 6

7. TWISTED PAIR Twisted pair cables have connectors at the end, known as RJ connectors (RJ-45, RJ-11) 7

8. TWISTED PAIR Twisted-Pair Cable Twisting: Twisting wires reduces the effect of electromagnetic interference (the EM energy the cable emits) or crosstalk .  When the wires are twisted, the waves from different twists cancel out, so the wire radiates (produce heat) less effectively More twists = better quality It is important to install cable away from sources of interference such as high-voltage cables and fluorescent lighting. Televisions, computer monitors and microwaves are other possible sources of interference. Crosstalk : Is the leakage of signals between pairs. Crosstalk degrade network performance and are often caused by untwisting too much cable when terminating. If high crosstalk values are detected, the best thing to do is check the cable terminations and re-terminate as necessary 8

9. APPLICATION  Twisted pairs can be used for transmitting either analog or digital signals. Telephone network (between house and local exchange) LAN (10 Mbps or 100 Mbps) - 9

10. Advantages AND DISADVANTAGES ADVANTAGE Easy to work with (Install) Less expensive DISADVANTAGE Low data rate Short range 10

11. TWISTED PAIR 4 Characteristics: Analog transmission - Amplifiers every 5km to 6km Digital transmission - Repeater every 2km or 3km TP is Limited - Distance - Data rate Susceptible to interference and noise 11

12. TWISTED PAIR Types: Shielded twisted pair (STP): a metallic shield around the wire pairs minimizes the impact of the penetration of noise or crosstalk. Unshielded twisted pair (UTP ) 12

13. SHIELDED TWISTED PAIR Shielded Twisted Pair: Shielded Twisted Pair cables are used almost exclusively (not including) in European countries-IBM Production. 13 Note: Foil is a very thin sheet of metal  Preventing the penetration of noise or crosstalk.

14. Shielded Twisted Pair: Cost: - STP cable costs more than thin coaxial or unshielded twisted-pair cable . STP is less costly, however, than thick coax or fiber-optic cable. Capacity: - The most common data rate for STP cable is 16 Mbps, which is the top data rate for Token Ring networks. Attenuation: 14 - All varieties of twisted-pair cable have attenuation characteristics that limit the length of cable runs to a few hundred meters, although a 100- meter limit is most common.

15. UNSHIELEDED TWISTED PAIR \ The Electronic Industries Association-EIA has developed standards to classify UST cable to 7 categories. Categories are determined by cable quality, with 1 as the lowest and 7 as the highest. Each EIA category is suitable for specific uses. 15 Category Bandwidth Data Rate Digital/Analog Use 1 very low < 100 kbps Analog Telephone 2 < 2 MHz 2 Mbps Analog/digital T-1 lines 3 16 MHz 10 Mbps Digital LANs 4 20 MHz 20 Mbps Digital LANs 5 100 MHz 100 Mbps Digital LANs 6 200 MHz 200 Mbps Digital LANs 7 600 MHz 600 Mbps Digital LANs

16. Unshielded Twisted Pair: 16

17. Unshielded Twisted Pair: 17

18. Unshielded Twisted Pair: UTP connector : The most common UTP connector is RJ45 (RJ=Registered Jack) 18

19. Color code for 4 cable pairs 19 Pair # Primary color Secondary color (stripe) 1 Blue White 2 Orange White 3 Green White 4 Brown White

20. 568A AND 568B EIA organization defines two different patterns, or wiring scheme, called T568A and T568B. The two schemes are similar except two of the four pairs are reversed in the termination order. The graphic shows this color-coding and how the two pairs are reversed. On a network installation, one of the two wiring schemes (T568A or T568B) should be chosen and followed. 20

21. STRAIGHT-THROUGH Using the T568A and T568B wiring standards, two types of cables can be created: a straight-through cable and a crossover cable A straight-through cable : is the most common cable type. It maps a wire to the same pins on both ends of the cable. In other words, if T568A is on one end of the cable, T568A is also on the other. If T568B is on one end of the cable, T568B is on the other. This means that the order of connections for each color is the exact same on both ends. 21

22. CROSSOVER CABLE Crossover Cable : A crossover cable uses both wiring schemes. T568A on one end of the cable and T568B on the other end of the same cable. This means that the order of connection on one end of the cable does not match the order of connections on the other. 22

23. USES OF STRAIGHT THROUGH Connecting between unlike devices 23

24. straight-through cable : Unlike Device: The pins on the RJ-45 data connector of a PC have pins1 and 2 as transmit and pins 3 and 6 as receive. The pins on the data connector of a switch have pins 1 and 2 as receive and pins 3 and 6 as transmit Examples of unlike devices that require a straight-through cable include: - Switch port to Router port - Switch port to PC - Hub port to PC 24

25. CROSSOVER CABLE Connecting between like devices 25

26. CROSSOVER CABLE Connecting between like devices Like Device: 26

27. Example of using Straight-through and Crossover Cable ] 27

28. Application of UTP - Used in telephone lines to provide voice and data channels. - The DSL lines that are used by the telephone companies to provide high-data-rate connections also use the high-bandwidth capability of unshielded twisted-pair cables. - Local-area networks, such as l0Base-T and l00Base-T, also use twisted-pair cables. 28

29. UTP VS STP 29 Unshielded Twisted Pair (UTP) Used for telephone wire Cheapest type of cable Easiest type to be installed Suffers from external Electromagnetic (EM) interference Shielded Twisted Pair (STP) Metal braid or covering that reduces interference More expensive Harder to handle (thick, heavy) Provide better performance than UTP

30. Coaxial Cable Like twisted pair, coaxial cable (or coax) also carries data in the form of electrical signals. It provides improved shielding compared to UTP, so has a lower signal-to-noise ratio and can therefore carry more data Although coax has improved data carrying characteristics, most local area networking uses twisted pair because coax is physically harder to install and is more expensive. 30

31. Categories of coaxial cables Divided into two basic categories:  50-ohm cable [ baseband ]  75-ohm cable [ broadband or single channel baseband ] 31 Radio Government 

32. Categories of coaxial cables Baseband Coax: - 50-ohm cable is used exclusively (only for) for digital transmissions - 10Base5 Thick Ethernet : thick (10 mm) coax 10 Mbps, 500m max segment length, 100 devices/segment, awkward (difficult) to handle and install. - 10Base2 Thin Ethernet : thin (5 mm) coax 10 Mbps, 185m max segment length, 30 devices/segment, easier to handle. 32

33. Categories of coaxial cables Baseband Coax: 33

34. Categories of coaxial cables Broadband Coax: - 75-ohm cable (Cable TV system standard). - Used for both analog and digital signaling. - For long-distance transmission of analog signals, amplifiers are needed every few kilometers. 34

35. Coaxial Cable Connectors: 35 The BNC connector is used to connect the end of the cable to a device, such as TV set. The BNC T connector is used in Ethernet networks to branch out to a connection to a computer or other device. The BNC terminator is used at the end of the cable to prevent the reflection of the signal.

36. Coaxial Cable Connectors: 36

37. PERFORMANCE AND APPLICATION PERFORMANCE Higher bandwidth than twisted-pair However, attenuation is higher and requires frequent use of repeaters APPLICATION Television distribution  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 37

38. CHARACTERISTICS Analog - Amplifier every few Km Digital - Repeater every 1 Km Problem - Thermal noise 38

39. FIBER OPTIC CABLE A fiber-optic cable is made of glass or plastic and transmits signals in the form of light. Light travels in a straight line as long as it is moving through a single uniform substance. If a ray of light traveling through one substance suddenly enters another substance (of a different density), the ray changes direction. 39

40. Fiber Optic Cable - As the figure shows, if the angle of incidence I is less than the critical angle, the ray refracts and moves closer to the surface. - If the angle of incidence is equal to the critical angle, the light bends along the interface. - If the angle I is greater than the critical angle, the ray reflects (makes a turn) and travels again in the denser substance. 40

41. Fiber Optic Cable ARCHITECTURE 41 Core Glass or plastic with a higher index of refraction than the cladding Carries the signal Cladding Glass or plastic with a lower index of refraction than the core Buffer ( one type of component made from plastic) Protects the fiber from damage and moisture Jacket Holds one or more fibers in a cable

42. Propagation Modes 42

43. Propagation Modes Multi Mode It is referred to as multimode because there are multiple rays of light, each carrying data, being transmitted through the cable simultaneously. Each ray of light takes a separate path through the multimode core. Multimode fiber optical cables are generally suitable for links of up to 2000 meters. However, improvements in technology are continually improving this distance. 43

44. Propagation Modes: Multi Mode Multimode step-index fiber The density of the core remains constant from the center to the edges. Light moves through this constant density in a straight line until it reaches the interface of the core and the cladding. Some beams penetrate the cladding and are lost, while others are reflected down the channel to the destination As a result, beams reach the destination at different times and the signal may not be the same as that which was transmitted Step index multimode was developed first, but rare today because it has a low bandwidth, It has been replaced by graded-index multimode with a higher bandwidth 44

45. Multi Mode Multimode step-index fiber 45

46. Multi Mode Multimode graded-index fiber - Graded-index refers to varying densities of the fiber; highest at center and decreases at edge - May be used to decreases this distortion of the signal through the cable and to allow for more precise (exact) transmissions - Eliminates problem with some of the signals penetrating the cladding - Since the core density decreases with distance from the center, the light beams refract into a curve 46

47. Multimode graded-index fiber 47

48. Single Mode +Propagation Modes: Only one beam from a light source is transmitted through the fiber The single mode fiber itself is manufactured with a much smaller diameter than that of multimode fiber, and with lower density (index of refraction). The decrease in density results in a critical angle that is close enough to 90° to make the propagation of beams almost horizontal. - Delays are negligible (to slight or small) All the beams arrive at the destination "together" and can be recombined with little distortion to the signal Single mode fibers can transmit data for approximately 3000 meters and improvements in technology are continually improving this distance. 48

49. Single Mode 49

50. Propagation Modes 50

51. LIGHT SOURCE OF FIBER OPTICS Light source is light-emitting diode (LED) or a laser Single Mode: - Uses laser as the light source, suitable for long distance applications Multimode: - Uses Light Emitting Diode-LED as the light source -- LEDs are cheaper than lasers -- Suitable for long distance applications, but shorter than single mode. 51

52. Fiber Sizes Optical fibers are defined by the ratio of the diameter of their core to the diameter of their cladding, both expressed in micrometers 52

53. Fiber-Optic Cable Connectors : There are three types of connectors for fiber-optic cables: 53

54. Fiber-Optic Cable Connectors : There are three types of connectors for fiber-optic cables: The subscriber channel (SC) connector is used for cable TV. The straight-tip (ST) connector is used for connecting cable to networking devices. Mechanical Transfer Registered Jack (MT-RJ) is a connector that is the same size as RJ45. MTRJ connectors are designed to snap into the Ethernet port of a computer, modem, or wireless router and provide that computer or network with extremely fast data transfer rates. 54

55. PERFORMANCE AND APPLICATION PERFORMANCE Attenuation is lower than in the case of twisted-pair cable and coaxial cable.  Need Repeater APPLICATION Fiber-optic cable is often found in backbone (SONET) networks because its wide bandwidth is cost-effective. Today, with wavelength-division multiplexing (WDM), we can transfer data at a rate of 1600 Gbps. Cable TV companies also use optical fiber and Local-area networks such as 100Base-FX network (Fast Ethernet) and 1000Base-X also use fiber-optic cable 55

56. Advantages of Optical Fiber: Advantages Fiber-optic cable has several advantages over metallic cable (twisted-pair or coaxial). Higher bandwidth. Fiber-optic cable can support dramatically higher bandwidths (and hence data rates) than either twisted-pair or coaxial cable ( Data rates of hundreds of Gbps ) Less signal attenuation. Fiber-optic transmission distance is significantly greater than that of other guided media. A signal can run for 50 km without requiring regeneration. We need repeaters every 5 km for coaxial or twisted-pair cable. Immunity to electromagnetic interference. Electromagnetic noise cannot affect fiber-optic cables . 56

57. Disadvantages of Optical Fiber: There are some disadvantages in the use of optical fiber. Installation and maintenance. Fiber-optic cable is a relatively new technology. Its installation and maintenance require expertise that is not yet available every where. Unidirectional light propagation. Propagation of light is unidirectional. If we need bidirectional communication, two fibers are needed. Cost is relatively more expensive than those of other guided media. 57

58. UNGUIDED Media Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication. Signals are normally broadcast through free space and thus are available to anyone who has a device capable of receiving them. Electromagnetic spectrum for wireless communication The electromagnetic spectrum, ranging from 3 kHz to 900 THz, used for wireless communication. 58

59. Propagation methods Unguided signals can travel from the source to destination in several ways: ground propagation, sky propagation, and line-of-sight propagation. 59 The ionosphere is a part of the upper atmosphere , from about 85 km to 600 km altitude

60. ground propagation Radio waves travel through the lowest portion of the atmosphere, hugging the earth. These low-frequency signals emanate (propagate) in all directions from the transmitting antenna and follow the curvature of the planet Distance depends on the amount of power in the signal: The greater the power, the greater the distance. 60

61. sky propagation Higher-frequency radio waves radiate upward into the ionosphere (the layer of atmosphere where particles exist as ions) and then reflect back to Earth This type of transmission allows for greater distances with lower output power. 61

62. line-of- sight propagation Very high-frequency signals are transmitted in straight lines directly from antenna to antenna. Antennas must be directional, facing each other, and either tall enough or close enough together not to be affected by the curvature of the earth. The section of the electromagnetic spectrum defined as radio waves and microwaves is divided into eight ranges (as table below), called bands, each regulated by government authorities. These bands are rated from very low frequency (VLF) to extremely high frequency (EHF). 62

63. UNGUIDED Media 63

64. Transmission Media 4.2 Unguided Media Wireless transmission waves We can divide wireless transmission into three broad groups: radio waves, microwaves, and infrared waves. 64

65. Radio wave Electromagnetic waves ranging in frequencies between 3 kHz and 1 GHz are normally called radio waves; waves ranging in frequencies between 1 and 300 GHz are called microwaves. Radio waves, for the most part, are omni directional. When an antenna transmits radio waves, they are propagated in all directions. This means that the sending and receiving antennas do not have to be aligned (straight line). 65

66. Radio wave Radio waves, particularly those waves that propagate in the sky mode , can travel long distances. This makes radio waves a good candidate for long-distance broadcasting such as AM radio. Radio waves, particularly those of low and medium frequencies, can penetrate walls.  Omni directional Antenna 66

67. Wireless transmission waves Radio wave:  Application: - Broadcast radio (AM,FM) - TV - Cellular phones Micro waves: Electromagnetic waves having frequencies between 1 and 300 GHz are called microwaves. Microwaves are unidirectional . When an antenna transmits microwave waves, they can be narrowly focused. This means that the sending and receiving antennas need to be aligned . 67

68. Transmission Media 4.2 Unguided Media Wireless transmission waves Micro waves: Microwave propagation is line-of-sight  the both antennas that are far apart need to be very tall. Very high-frequency microwaves cannot penetrate walls. This characteristic can be a disadvantage if receivers are inside buildings. 68

69. Transmission Media 4.2 Unguided Media Wireless transmission waves Micro waves: Unidirectional Antenna Microwaves need unidirectional antennas that send out signals in one direction. Two types of antennas are used for microwave communications: the parabolic dish and the horn antennas. 69

70. Transmission Media 4.2 Unguided Media Wireless transmission waves Micro waves: 70

71. Transmission Media 4.2 Unguided Media Wireless transmission waves Micro waves: Microwave Applications Microwaves, due to their unidirectional properties, are very useful when unicast (one-to-one) communication is needed between the sender and the receiver. -- Cellular phones -- Satellite networks -- Wireless LANs 71

72. Transmission Media 4.2 Unguided Media Wireless transmission waves Infrared: Infrared waves, with frequencies from 300 GHz to 400 THz, can be used for short-range communication in a closed area using line-of-sight propagation. Infrared waves, having high frequencies, cannot penetrate walls. This advantageous characteristic prevents interference between one system and another; a short-range communication system in one room cannot be affected by another system in the next room. In Addition, we cannot use infrared waves outside a building because the sun's rays contain infrared waves that can interfere with the communication. 72

73. Transmission Media 4.2 Unguided Media Wireless transmission waves Infrared: Applications The infrared band, almost 400 THz, has an excellent potential for data transmission. The Infrared Data Association (IrDA), an association for sponsoring the use of infrared waves, has established standards for using these signals for communication between devices such as keyboards, mice, PCs, and printers. For example, some manufacturers provide a special port called the IrDA port that allows a wireless keyboard to communicate with a PC. The standard originally defined a data rate of 75 kbps for a distance up to 8 m. The recent standard defines a data rate of 4 Mbps. 73

74. Transmission Media 4.2 Unguided Media Wireless transmission waves (Bluetooth:) A technology that makes use of the 2.4 GHz band. It is limited to low-speed, short-range communications. It allows one-to-many communications has made Bluetooth technology the preferred method over IR. Bluetooth can transmit through solid, non-metal objects Its typical link range is from 10 cm to 10 m, but can be extended to 100 m by increasing the power. 74

75. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: What is Satellite? The word "satellite" refers to a machine that is launched into space and moves around Earth or another body in space which play role as a “relay station” Satellite Microwave, Similar to terrestrial microwave except the signal travels from a ground station on earth to a satellite (Uplink) and back to another ground station (Downlink). Satellite receives on one frequency, amplifies or repeats signal and transmits on another frequency A communication satellite can be thought of as a big microwave repeater in the sky. 75

76. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: 76

77. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: How do Satellites Work? Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional (simple) means. The two stations can use a satellite as a relay station for their communication One Earth Station sends a transmission to the satellite. This is called a Uplink . The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink . 77

78. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: Frequency band of satellite Communication 78

79. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: What Are the Parts of a Satellite? Satellites come in many shapes and sizes. But most have at least two parts in common -- an antenna and a power source . The antenna sends and receives information, often to and from Earth. The power source can be a solar panel, battery. Solar panels make power by turning sunlight into electricity. Three Categories of Satellite Geostationary Orbit Satellites (GEO) Medium-Earth Orbit Satellites (MEO) Low-Earth Orbit Satellites (LEO) 79

80. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: Three Categories of Satellite Geostationary Orbit Satellites (GEO): Height of 35,786km above the earth Propagation is line-of-sight  need sending and receiving antennas must face to face forever The satellites is placed in orbit such that they remain stationary relative to a fixed spot on earth. If a satellite is placed at 35,786 km above the earth, its angular velocity is equal to that of the earth, thereby causing it to appear to be over the same point on earth. This allows for them to provide constant coverage of the area 80

81. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: Three Categories of Satellite Geostationary Orbit Satellites (GEO): Number of satellites needed for global coverage are three, separate 120 degree from each other. Lecturer: Kim No 81

82. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: Three Categories of Satellite Medium-Earth Orbit Satellites (MEO): Height of 5 000km to 15 000Km above the earth, higher than low earth orbit (LEO) satellites, but lower than geostationary satellites (GEO). Number of satellites needed for global coverage are 10 82

83. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: Three Categories of Satellite Low-Earth Orbit Satellites (LEO): Height of 500km to 2 000Km above the earth This type of an orbit reduces transmission times as compared to GEO A LEO orbit can also be used to cover a polar region Number of satellites needed for global coverage are 50 83

84. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: The advantages of satellite communication over terrestrial communication are: The coverage area of a satellite greatly exceeds that of a terrestrial system. Higher Bandwidths are available for use The disadvantages of satellite communication: Launching satellites into orbit is costly. There is a larger propagation delay ( round-trip delay time ) in satellite communication than in terrestrial communication. 84

85. Transmission Media 4.2 Unguided Media Wireless transmission waves Satellite Communication: Application: Television Long distance telephone Private business networks Satellites versus fiber cables: More suitable for mobile communication Better suited for connecting remote areas. 85

86. Transmission Media 4.3 Summary A guided medium provides a physical conduit from one device to another. Twisted-pair cable, coaxial cable, and optical fiber are the most popular types of guided media. Twisted-pair cable is used for voice and data communications. Coaxial cable can carry signals of higher frequency ranges than twisted-pair cable. Coaxial cable is used in cable TV networks and traditional Ethernet LANs. Fiber optic transmission is becoming increasingly popular due to its noise resistance, low attenuation, and high-bandwidth capabilities. Fiber-optic cable is used in backbone networks, cable TV networks, and Fast Ethernet networks. Unguided media (free space) transport electromagnetic waves without the use of a physical conductor. 86

87. Transmission Media 4.3 Summary Wireless data are transmitted through ground propagation, sky propagation, and line of-sight propagation. Wireless waves can be classified as radio waves, microwaves, or infrared waves. Radio waves are Omni-directional; microwaves are unidirectional. Microwaves are used for cellular phone, satellite, and wireless LAN communications. Infrared waves are used for short-range communications such as those between a PC and a peripheral device (Keyboard with PC, mouse with PC). 87