1. CSC 535 Communication Networks I Chapter 3C Transmission Media (Section 3.7) Dr. Cheer-Sun Yang

2. 2 Overview zGuided - wire zUnguided - wireless zCharacteristics and quality determined by medium and signal zFor guided, the medium is more important zFor unguided, the bandwidth produced by the antenna is more important zKey concerns are data rate and distance

3. 3 Design Factors zBandwidth yHigher bandwidth gives higher data rate zTransmission impairments yAttenuation zInterference zNumber of receivers yIn guided media yMore receivers (multi-point) introduce more attenuation

4. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks4 10 2 10 4 10 6 10 810 10 12 10 14 10 16 10 18 10 20 10 22 10 24 Frequency (Hz) Wavelength (meters) 10 6 10 4 10 2 1010 -2 10 -4 10 -6 10 -8 10 -10 10 -12 10 -14 power & telephone broadcast radio microwave radio infrared light visible light ultraviolet light x rays gamma rays Figure 3.35

5. 5 Electromagnetic Spectrum

6. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks6 t = 0 t = d/c communication channel d meters Figure 3.36

7. 7 Guided Transmission Media zTwisted Pair zCoaxial cable zOptical fiber

8. 8 Twisted Pair

9. 9 Twisted Pair - Applications zMost common medium zTelephone network yBetween house and local exchange (subscriber loop) zWithin buildings yTo private branch exchange (PBX) zFor local area networks (LAN) y10Mbps or 100Mbps

10. 10 Twisted Pair - Pros and Cons zCheap zEasy to work with zLow data rate zShort range

11. 11 Twisted Pair - Transmission Characteristics zAnalog yAmplifiers every 5km to 6km zDigital yUse either analog or digital signals yrepeater every 2km or 3km zLimited distance zLimited bandwidth (1MHz) zLimited data rate (100MHz) zSusceptible to interference and noise

12. 12 Unshielded and Shielded TP zUnshielded Twisted Pair (UTP) yOrdinary telephone wire yCheapest yEasiest to install ySuffers from external EM interference zShielded Twisted Pair (STP) yMetal braid or sheathing that reduces interference yMore expensive yHarder to handle (thick, heavy)

13. 13 UTP Categories zCat 3 yup to 16MHz yVoice grade found in most offices yTwist length of 7.5 cm to 10 cm zCat 4 yup to 20 MHz zCat 5 yup to 100MHz yCommonly pre-installed in new office buildings yTwist length 0.6 cm to 0.85 cm

14. 14 Near End Crosstalk zCoupling of signal from one pair to another zCoupling takes place when transmit signal entering the link couples back to receiving pair zi.e. near transmitted signal is picked up by near receiving pair

15. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks15 Attenuation (dB/mi) f (kHz) 19 gauge 22 gauge 24 gauge 26 gauge 6 12 3 9 15 18 21 24 27 30 110 1001000 Figure 3.37

16. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks16 Figure 3.38

17. 17 Applications zAsymmetric digital subscriber line (ADSL) yThe system uses existing twisted-pair lines to provide the higher bit rates. yIt is asymmetric in that users can transmit upstream at the speeds from 64 kbps (10**3 bits per second) to 640 kbps and receive information at the speed from 1.536 Mbps (10**6 bps) to 6.144 Mbps. zEthernet

18. 18 Coaxial Cable

19. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks19 Center conductor Dielectric material Braided outer conductor Outer cover Figure 3.39

20. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks20 35 30 10 25 20 5 15 Attenuation (dB/km) 0.010.1 1.0 10100 f (MHz) 2.6/9.5 mm 1.2/4.4 mm 0.7/2.9 mm Figure 3.40

21. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks21 Hea d end Unidirectional amplifier Figure 3.41

22. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks22 Hea d end Upstream fiber Downstream fiber Fiber node Coaxial distribution plant Fiber node Bidirectional Split-Band Amplifier Fiber Figure 3.42

23. 23 Coaxial Cable Applications zMost versatile medium zTelevision distribution yAriel to TV yCable TV zLong distance telephone transmission yCan carry 10,000 voice calls simultaneously yBeing replaced by fiber optic zShort distance computer systems links zLocal area networks

24. 24 Coaxial Cable - Transmission Characteristics zAnalog yAmplifiers every few km yCloser if higher frequency yUp to 500MHz zDigital yRepeater every 1km yCloser for higher data rates

25. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks25 Downstream 54 MHz 500 MHz Upstream Downstream 5 MHz 42 MHz 54 MHz 500 MHz 550 MHz 750 MHz (a) Current allocation (b) Proposed hybrid fiber-coaxial allocation Proposed downstream Figure 3.43

26. 26 Optical Fiber

27. 27 Optical Fiber - Benefits zGreater capacity yData rates of hundreds of Gbps zSmaller size & weight zLower attenuation zElectromagnetic isolation zGreater repeater spacing y10s of km at least

28. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks28 core cladding jacket light cc (a) Geometry of optical fiber (b) Reflection in optical fiber Figure 3.44

29. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks29 100 50 10 5 1 0.5 0.1 0.05 0.01 0.81.01.21.41.61.8 Wavelength (  m) Loss (dB/km) Infrared absorption Rayleigh scattering Figure 3.45

30. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks30 (a) Multimode fiber: multiple rays follow different paths (b) Single mode: only direct path propagates in fiber direct path reflected path Figure 3.46

31. 31 Optical Fiber - Applications zLong-haul trunks zMetropolitan trunks zRural exchange trunks zSubscriber loops zNetwork backbone zLANs

32. 32 Optical Fiber - Transmission Characteristics zAct as wave guide for 10 14 to 10 15 Hz yPortions of infrared and visible spectrum zLight Emitting Diode (LED) yCheaper yWider operating temp range yLast longer zInjection Laser Diode (ILD) yMore efficient yGreater data rate zWavelength Division Multiplexing

33. 33 Optical Fiber Transmission Modes

34. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks34 Optical fiber Optical source Modulator Electrical signal Receiver Electrical signal Figure 3.47

35. 35 Radio Transmission zUnguided media zTransmission and reception via antenna zDirectional yFocused beam yCareful alignment required z Omnidirectional ySignal spreads in all directions yCan be received by many antennae

36. Copyright 2000 McGraw-Hill Leon-Garcia & Widjaja Communication Networks36 10 4 10 6 10 7 10 8 10 910 10 11 10 12 Frequency (Hz) Wavelength (meters) 10 3 10 2 10 1 1 10 -1 10 -2 10 -3 10 5 satellite & terrestrial microwave AM radio FM radio & TV LF MF HF VHF UHF SHF EHF 10 4 Cellular & PCS Wireless cable Figure 3.48

37. 37 Frequencies z2GHz to 40GHz yMicrowave yHighly directional yPoint to point ySatellite z30MHz to 1GHz yOmnidirectional yBroadcast radio z3 x 10 11 to 2 x 10 14 yInfrared yLocal

38. 38 Terrestrial Microwave zParabolic dish zFocused beam zLine of sight zLong haul telecommunications zHigher frequencies give higher data rates

39. 39 Satellite Microwave zSatellite is relay station zSatellite receives on one frequency, amplifies or repeats signal and transmits on another frequency zRequires geo-stationary orbit yHeight of 35,784km zTelevision zLong distance telephone zPrivate business networks

40. 40 Broadcast Radio zOmnidirectional zFM radio zUHF and VHF television zLine of sight zSuffers from multipath interference yReflections

41. 41 Infrared zModulate noncoherent infrared light zLine of sight (or reflection) zBlocked by walls ze.g. TV remote control, IRD port

42. 42 Required Reading zSection 3.7