ITT300 - CHAPTER 6 TRANSMISSION MEDIA St.pdf

ITT300 INTRODUCTION TO DATA COMMUNICATION AND NETWORKING CHAPTER 6 TRANSMISSION MEDIA ADAPTED FROM: Behrouz A. Forouzan Learning Outcomes Able to discover type of transmission media that being used for data transmission Able to distinguish g...

ITT300 INTRODUCTION TO DATA COMMUNICATION AND NETWORKING CHAPTER 6 TRANSMISSION MEDIA ADAPTED FROM: Behrouz A. Forouzan Learning Outcomes Able to discover type of transmission media that being used for data transmission Able to distinguish guided transmission media and unguided transmission media Able to understand the characteristics for each transmission media 2 Transmission Media Transmission medium can be defined as anything that carry information eg:- [air, vaccum, water, UTP cable, fiber optic] Data represent as signal will transmit in the electromagnetic energy. In chapter 4, we have discussed that before data is transferred over the medium it will be converted from digital information to become a (digital signal or analog signal). 3 2 type of Transmission Media Transmission Media Guided Unguided (Wired) (Wireless) Free Space Twisted pair (mircowave, Coaxial Cable Fiber Optic Cable Cable radiowave, Statellite) 4  Guided Media Introduction Provide physical conductor from one device to another Include twisted pair wire, coaxial cable and fiber optic A signal traveling along any of these media is directed and contained by the physical limits of the medium Twisted pair and coaxial cable use cooper that transport signal in the form of electrical current Fiber optic use a glass or plastic that transport signals in the form of light * Physical mean something that we can touch 5 TWISTED-PAIR CABLE Consists of two conductors, each with its own plastic insulation, twisted together. And there will be 5 different pair of cable in the wire. With twisted, the cumulative effect of the interference is equal on both wires and the total effect is 0. Figure 7.5 UTP connector 7  TWISTED-PAIR CABLE Consists of two conductors, each with its own plastic insulation, twisted together. And there will be 5 different pair of cable in the wire. 20 20 20 A 10 10 10 B With twisted, the cumulative effect of the interference is equal on both wires and the total effect is 0. To calculate the noise, we use Decibel(dB) A = 20+10+20+10=60 B = 10+20+10+20=60 Cumulative effect : A – B = 0 Signal negative mean signal is attenuated (the signal power is decrease) Signal positive signal is amplified(the signal power is increase)  Twisted Pair Cable Can be divided into two forms Unshielded Twisted Shielded Twisted Pair Cable Pair Cable (UTP) (STP) – Cover by metal shield 9 Figure 7.4 UTP and STP 10 Guided Media Unshielded Twisted Pair(UTP) Suitable for transmitting both data and voice Frequency range for twisted pair wire is between 100 Hz to 5 Mhz Consists of two conductors(cooper) each with its own colored plastic insulation Advantages of UTP are cost and ease to use With twisted, the cumulative effect of interference is equal on both wires and the total effect is 0 11 Guided Media Shielded Twisted Pair(STP) Has a metal shield that encases each pair of insulated conductors The metal casing prevents the penetration of electromagnetic noise Also can eliminate phenomenon called crosstalk More expensive than UTP but uses same connectors 12 Table 7.1 Categories of unshielded twisted-pair cables 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 13 Guided Media Coaxial Cable * The data is conducted through Carriers signals of higher frequency the inner conductor ranges than twisted pair wire Frequency range of coaxial cable is between 100 KHz to 500 MHz Has a central core conductor of solid wire(usually cooper) enclosed with insulator which encased an outer conductor of metal foil(usually cooper) Figure 7.7 Coaxial cable The whole cable is protected by a plastic cover. 14 Guided Media Best for HDTV A few common of coaxial cable RG-59 used for Cable TV RG-11 RG-58 used for Thin Ethernet RG-11 used for Thick Ethernet Usually low-power signal and RF connections Usually for CCTV 15  Most commonly connectors used are Bayone-Neill-Concelman (BNC) connector, BNC T connector and BNC terminator Three popular types: BNC connector – used to connect in TV set BNC T connector – used in Ethernet networks BNC terminator – prevent signal reflection Figure 7.8 BNC connectors 16 Guided Media Fiber optic cable To understand fiber optic, we first need to understand about the nature of light The Nature of light Light is a form of electromagnetic energy It travels at its fastest in a vacuum:300,000 km/second The speed of light depends on the density of the medium through which it is traveling (the bigger the data, the slower the speed) 17  Made of glass or plastic. Outer jacket is made of either Figure 7.14 Fiber construction PVC or Teflon. Inside jacket are Kevlar (strong material used to strengthen the cable) - DuPont Kevlar Below inside jacket is another plastic coating to cushion the fiber. Fiber is at the center – consist of cladding and core. 18 Guided Media Refraction (Bending) Light travels in straight line If the speed changes abruptly when the ray of light traveling through one substance to another, the phenomenon called refraction Two angles made by the beam of light in relation to the vertical axis are called L, angle for incident, the R, angle for refracted 19 Guided Media Reflection(reproduction) When refracted angle is 90 degree, at this point L is called critical angle When L becomes greater than critical, a new phenomenon occurs called reflection Optical fiber use reflection to guide light through a channel. A glass or plastic core is surrounded by a cladding of less dense glass or plastic The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead of being refracted into it 20 Fiber-Optic Cable Connectors MT-RJ is a connector that is the same size as RJ45. Figure 6.8 Fiber-optic cable connectors Applications Often found in backbone networks (bus topology). Used in some TV companies. This is cost-effective configuration. Applications Advantages of fiber optic Noise resistance Less signal attenuation(signal reduction) Higher bandwidth Immunity of electromagnetic interference Light weight More immune to tapping Resistance to corrosive materials (hardier because the transmission is protected inside cable) Applications Disadvantages of fiber optic Cost Installation Maintenance Unguided Media Wireless Communication Radiowaves Microwave Infrared 25 Unguided Media Media transport electromagnetic waves without using physical conductor It refers to as Wireless communication Unguided signal can travel from the source to destination in several ways (depend propagation type) 1. Ground propagation Radio waves travel through the lowest portion of the earth Distance depends the amount of power in the signal Greater power , greater distance 26 Unguided Media 2. Sky propagation Higher frequency radio waves radiate upward into the ionosphere where they are reflected back to earth (example satellite) 3. Line of sight Very high frequency signal are transmitted in straight line directly from antenna to antenna 27  * Here you can see the light weight is the fastest one Figure 7.17 Electromagnetic spectrum for wireless communication 28 Propagation Types Line of sight must face opposite between each other Atmosphere Figure 7.18 Propagation methods 29 Table 7.4 Bands *Last time radio use AM, now we use FM Band Range Propagation Application VLF 3–30 KHz Ground Long-range radio navigation Radio beacons and LF 30–300 KHz Ground navigational locators MF 300 KHz–3 MHz Sky AM radio Citizens band (CB), HF 3–30 MHz Sky ship/aircraft communication Sky and VHF TV, VHF 30–300 MHz line-of-sight FM radio UHF TV, cellular phones, UHF 300 MHz–3 GHz Line-of-sight paging, satellite SHF 3–30 GHz Line-of-sight Satellite communication EHF 30–300 GHz Line-of-sight Long-range radio navigation 30 Radio waves Frequency between 3Khz to 1 GHz Function of omnidirectional antenna – radio waves propagated in all direction. Sending antenna and receiving antenna do not have to be aligned Radio waves propagate in the sky can travel in long distance eg AM radio Omni directional Antenna Send signal out in other directions Based on the wavelength, strength, and the purpose of transmission 31 Radio wave Omni directional Antenna Send signal out in other directions Useful for multicasting – one sender , many receiver. (everyone can receive the same input) Application Cordless AM & FM radio Television Maritime Radio Phone 32 Microwave Frequencies between 1 to 300 GHz Microwave are unirectional-antenna narrowly focused. Sending and receiving antenna need to be aligned without interfering with another pair of aligned antennas Microwave cannot penetrate walls. 33 Microwave Propagation is line of sight. Tower that mounted with antenna need to be in direct sight of each other. Tower that far apart need to be very tall. Repeaters are needed for long distance communication Use certain portions of band required from authorities 34 Microwave Unidirectional (one direction) antenna Send out signal in one direction 2 types a) Parabolic antenna Based on geometry of a parabola. Every line parallel to Line of Symmetry(LOS) reflect off the curve at angel such that all lines intersect in common point It work as a funnel-catching wide range of wave and direct them to common point. b) Horn antenna Like a gigantic scoop receiver transmission are collected by the scoop 35 Figure 7.21 Unidirectional antennas 36 Microwave Application Cellular phone Satellite Network 37 Infrared Frequencies between 300Ghz to 400THz (wavelenght 1mm – 70 nm) For short range communication eg IrDA port that allow a wireless keyboard to communicate with PC Useful for data transmission because use high frequencies(400THz) Cannot penetrate wall or affected by another system in the next room Infrared wave cannot be used outside a building because the sun’ rays contain infrared waves that can interfere eith the communication 38 Infrared Application It used for communication between devices such as wireless keyboards, mouse and printer Eg;- Infrared signal defined IrDA transmit through line of sight, the IrDA port on the keyboard needs to point to the PC for transmission occur 39 Summary Transmission media lie below the physical layer Guided medium provides a physical conduit from one device to another device Unguided media transport electromagnetic waves without physical conductor. Each types transmission media has own characteristics, advantage and disadvantage and its limitation 40