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IEG 3310 B

IEG 3310 B. Chapter #3 - Physical Media. Page 1. What you need to learn. Wired and Wireless Media Wired: UTP, STP, Coaxial Cable, Fiber Wireless: Radio, Infrared, Free optics Characteristics and Capacity Characteristics – protection, connection, application

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IEG 3310 B

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  1. IEG 3310 B Chapter #3 - Physical Media Page 1

  2. What you need to learn • Wired and Wireless Media • Wired: UTP, STP, Coaxial Cable, Fiber • Wireless: Radio, Infrared, Free optics • Characteristics and Capacity • Characteristics – protection, connection, application • Capacity – frequency response, interference & noise, distortion • Calculations • Attenuation and Distortion • Transmission Time • Propagation Delay

  3. Reading • Textbook sections • LG Section 3.8 Properties of Media and Digital Transmission Systems

  4. Fundamental Issues d meters Communication channel t = d/c t = 0 • Attenuation (dB/km) • Distortion (amplitude-frequency response) • Noise and Interference (S/N ratio) • Capacity of a channel • Bandwidth.distance product

  5. Decibel (dB) • dB is the logarithm ratio of two signals or two powers. • The difference in decibels is defined to be • 10 log10 (P2/P1) dB - power • 20 log10 (V2/V1) dB - V/I 10 log (P2/P1) = 10 log 2 = 3 dB. 10 log (P2/P1)= 10 log 10 = 10 dB. 10 log (P2/P1) = 10 log 1000000 = 60 dB. http://www.phys.unsw.edu.au/~jw/dB.html

  6. Wired Media - Twisted Pair - Unshielded twisted-pair (UTP) cable

  7. Twisted pair • Simple, Low cost, Easy to Connect • Two insulated copper wires arranged in a regular spiral pattern to minimize interference • Various thicknesses, e.g. 0.016 inch (24 gauge) • Applications • Telephone subscriber loop from customer to CO • Old trunk plant connecting telephone COs • Intra-building telephone from wiring closet to desktop • In old installations, loading coils added to improve quality in 3 kHz band, but more attenuation at higher frequencies

  8. 26 gauge 30 24 gauge 24 22 gauge 18 Attenuation (dB/mi) 19 gauge 12 6 f (kHz) 1 1000 100 10 Twisted Pair 0.019in diameter 0.024in Attenuation Characteristics (dB/mile) diameter loss Lower attenuation rate analog telephone Higher attenuation rate for DSL

  9. Twisted Pair Bit Rates • Twisted pairs can provide high bit rates at short distances • Asymmetric Digital Subscriber Loop (ADSL) • High-speed Internet Access • Lower 3 kHz for voice • Upper band for data • 64 kbps inbound • 640 kbps outbound • Much higher rates possible at shorter distances • Strategy for telephone companies is to bring fiber close to home & then twisted pair • Higher-speed access + video Table 3.5 Data rates of 24-gauge twisted pair

  10. Category of UTP cables How to wire a Cat-5 cable? http://www.netspec.com/helpdesk/wiredoc.html

  11. Category 3 unshielded twisted pair (UTP): ordinary telephone wires Category 5 UTP: tighter twisting to improve signal quality 10BASE-T Ethernet 10 Mbps, Baseband, Twisted pair Two Cat3 pairs Manchester coding, 100 meters 100BASE-T Fast Ethernet 100 Mbps, Baseband, Twisted pair Four Cat5 pairs 100/3 Mbps per pair;       Ethernet LANs

  12. Connectors UTP EIA/TIA 568A Wiring Standard UTP EIA/TIA 568B Wiring Standard male male female female RJ-11 RJ-45 Q: How many wires are really used?

  13. Straight Through Cable Computer Hub 1 Tx+ 1 Rx+ 2 Tx- 2 Rx- 3 Rx+ 3 Tx+ 6 Rx- 6 Tx- Straight Connect Other lines: unused.

  14. Cross Connect We need a cross over cable – one side uses 568A and the other side uses 568B

  15. Shielded twisted-pair (STP) cable • More expensive, more difficult to install than UTP because the shield must be grounded. • However, STP is less susceptible to noise and cross-talk than UTP.

  16. Coaxial Cable

  17. Coaxial Cable Connectors

  18. 35 0.7/2.9 mm 30 1.2/4.4 mm 25 20 Attenuation (dB/km) 15 10 2.6/9.5 mm 5 0.1 10 100 1.0 f (MHz) Coaxial Cable Twisted pair • Cylindrical braided outer conductor surrounds insulated inner wire conductor • High interference immunity • Higher bandwidth than twisted pair • Hundreds of MHz • Cable TV distribution • Long distance telephone transmission • Original Ethernet LAN medium

  19. Downstream Upstream 5 MHz 42 MHz 54 MHz 500 MHz Cable Modem & TV Spectrum Downstream • Cable TV network originally unidirectional • Cable plant needs upgrade to bidirectional • 1 analog TV channel is 6 MHz, can support very high data rates • Cable Modem: shared upstream & downstream • 5-42 MHz upstream into network; 2 MHz channels; 500 kbps to 4 Mbps • >550 MHz downstream from network; 6 MHz channels; 36 Mbps 750 MHz 550 MHz

  20. Upstream fiber Fiber Fiber Head end Fiber node Fiber node Downstream fiber Coaxial distribution plant = Bidirectional split-band amplifier Cable-TV Network

  21. Optical fiber Modulator Optical source Wired Media - Optical Fiber • Light sources (lasers, LEDs) generate pulses of light transmitted on fiber • Very long distances (>1000 km) • Very high speeds (>40 Gbps/wavelength) • Nearly error-free (BER of 10-15) • Profound influence on network architecture • Dominates long distance transmission • Distance less of a cost factor in communications • Plentiful bandwidth for new services Electrical signal Electrical signal Receiver

  22. Light Cladding Jacket Core c Transmission in Optical Fiber • Very fine glass cylindrical core surrounded by concentric layer of glass (cladding) • Core has higher index of refraction than cladding • Light rays incident at less than critical angle qc is completely reflected back into the core Geometry of optical fiber Total Internal Reflection in optical fiber Rf-c Rf-i

  23. Refraction and reflection total internal reflection: the key to fiber optics

  24. Multimode fiber: multiple rays follow different paths Reflected path Direct path Single-mode fiber: only direct path propagates in fiber Multimode & Single-mode Fiber • Multimode: Thicker core, shorter reach • Rays on different paths interfere causing dispersion & limiting bit rate • Single mode: Very thin core supports only one mode (path) • More expensive lasers, but achieves very high speeds

  25. Fusion Splicing • Prepare fiber • Cleave the fiber • Fuse the fiber • Protect the fiber

  26. Advantages Very low attenuation Noise immunity Extremely high bandwidth Security: Very difficult to tap without breaking No More compact & lighter than copper wire Disadvantages New types of optical signal impairments & dispersion Polarization dependence Wavelength dependence Limited bend radius If physical arc of cable too high, light lost or won’t reflect Will break Difficult to splice Mechanical vibration becomes signal noise Optical Fiber Properties

  27. Fiber cable and connectors • Fiber-optic cable • Transmit data at very high speeds over long distances in a very secure media • Higher cost (Pricing for fiber-optic cable is competitive with high-end copper cabling) • Expertise needed to properly install it and connect devices to it (fiber-optic cable is increasingly easier to work with. Terminating techniques require fewer parts and less expertise) • Each glass strand passes signals in only one direction, so a cable consists of two strands in separate jackets. One strand transmits and one receives. • Fiber-optic cable connectors • All of the popular connectors are barrel shaped and come in male and female versions. The cable is equipped with a male connector that locks or threads into a female connector attached to the device to be connected.

  28. 100 50 10 5 Infrared absorption Loss (dB/km) 1 0.5 Rayleigh scattering 0.1 0.05 0.01 Wavelength (m) 0.8 1.0 1.2 1.4 1.6 1.8 Very Low Attenuation Water Vapor Absorption (removed in new fiber designs) 1300 nm Metropolitan Area Networks “Short Haul” 1550 nm Long Distance Networks “Long Haul 850 nm Low-cost LEDs LANs

  29. vλ1 vλ1 100 50 2(108)m/s 200nm (1450 nm)2 vλ1 + Δλ 10 5 Δλ / λ1 1 + Δλ / λ1 B = f1 – f2 = – v Δλλ12 Loss (dB/km) = ≈ 1 0.5 0.1 0.8 1.0 1.2 1.4 1.6 1.8 Huge Available Bandwidth • Optical range from λ1to λ1+Δλ contains bandwidth • For example: • λ1= 1450 nm λ1+Δλ =1650 nm B = ≈ 19 THz

  30. 1 1 2 1 2 2. m optical fiber optical mux optical demux m m Wavelength-Division Multiplexing • Different wavelengths carry separate signals • Multiplex into shared optical fiber • Each wavelength like a separate circuit • A single fiber can carry 160 wavelengths, 10 Gbps per wavelength: 1.6 Tbps!

  31. Wired Media - Standards

  32. Wireless Media • Radio Frequency (RF) transmission • Unlike networks that use wires or optical fibers, networks using RF transmission do not require a direct physical connection between computers. • Instead, each participating computer attaches to an antenna, which can both transmit and receive RF • Although RF transmission do not bend around the surface of the earth, RF technology can be combined with satellites to provide communication across longer distances.

  33. Wireless Network Wireless LAN Mobile Network

  34. Radio Transmission • Radio signals: antenna transmits sinusoidal signal (“carrier”) that radiates in air/space • Information embedded in carrier signal using modulation, e.g. QAM • Communications without tethering • Cellular phones, satellite transmissions, Wireless LANs • Multipath propagation causes fading • Interference from other users • Spectrum regulated by national & international regulatory organizations

  35. Electromagnetic spectrum Frequency (Hz) 106 108 1010 1012 1014 1016 1018 1020 1022 1024 102 104 power & telephone broadcast radio microwave radio gamma rays infrared light visible light ultraviolet light x rays 106 104 102 10 10-2 10-4 10-6 10-8 10-10 10-12 10-14 Wavelength (meters)

  36. Radio and infrared frequencies

  37. Radio Spectrum Frequency (Hz) 106 1012 105 108 107 104 1011 109 1010 FM radio and TV Wireless cable AM radio Cellular and PCS Satellite and terrestrial microwave LF MF HF VHF UHF SHF EHF 10-1 1 102 10-3 10-2 101 104 103 Wavelength (meters) Omni-directional applications Point-to-Point applications

  38. Wireless Media Signal energy propagates in space, limited directionality Interference possible, so spectrum regulated Limited bandwidth Simple infrastructure: antennas & transmitters No physical connection between network & user Users can move Wired Media Signal energy contained & guided within medium Spectrum can be re-used in separate media (wires or cables), more scalable Extremely high bandwidth Complex infrastructure: ducts, conduits, poles, right-of-way Wireless & Wired Media

  39. Cellular Phone Allocated spectrum First generation: 800, 900 MHz Initially analog voice Second generation: 1800-1900 MHz Digital voice, messaging WirelessLAN Unlicenced ISM spectrum Industrial, Scientific, Medical 902-928 MHz, 2.400-2.4835 GHz, 5.725-5.850 GHz IEEE 802.11 LAN standard 802.11b – 11 Mbps 802.11g – 54 Mbps Point-to-MultipointSystems Directional antennas at microwave frequencies High-speed digital communications between sites High-speed Internet Access Radio backbone links for rural areas SatelliteCommunications Geostationary satellite @ 36000 km above equator Relays microwave signals from uplink frequency to downlink frequency Long distance telephone Satellite TV broadcast Examples

  40. Other wireless media • Infrared – low-speed, small area communications (e.g., remote control). • Free space optics – WDM Gigabit space communications. • Ultrasonics - Deep sea communications • Radar – high frequency signals • Eye communications – low speed, 3D, full color

  41. Calculations Page 41

  42. Propagation Speed • Electromagnetic signals are propagated in free space at the speed of 3x108 meters/second • In copper wire the speed of electromagnetic signals is 2.3x108 meters/second • In optical fiber system the speed of light is 2x108 meters/second

  43. Problem #1 - Capacity • You have an uncompressed photo (800x600, 16-bit colors). How long does it take to transmit the photo over (neglecting protocol overhead) • 56 kbps dialup modem line • 3 Mbps ADSL modem line • 10 Mbps Ethernet • 100 Mbps Ethernet • What if you compressed the photo to JPEG to only 10% of the size? • What if you have a CDROM of 650 Mbyte of data?

  44. Problem#2 – Transmission Delay • Calculate the time needed for station A to transmit a 100 Kbyte file and received by station B: • 100 m 56 kbps modem line • 10 km 56 kbps modem line • 100 m 100 Mbps Ethernet line • 10 km 100 Mbps Ethernet line • 10 Mbps 35000 km Satellite link • Delay involved • Transmission Time - required to transmit the file • Propagation delay – required to reach the destination http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970408d.html

  45. Problem #3 – End-to-End Delay • You are sending a 100 MByte file over a 1 Mbps network. Calculate the end-to-end delay if: • The network has one hop of 1 km fiber cable. • The network has three hops, each of 1 km fiber cable. • Now you decide to divide your file into 1 Kbyte packets. Each packet is added a header of 100 bytes. Each packet is transmitted, received, and forwarded independently. Calculation the end-to-end delay again.

  46. Problem #4 - Attenuation • A Category 5 cable has the following specification: • Cat5– 2500 ft (762m) Cable • UTP 24gauge or lower solid copper twisted pair wire • Impedance: 100 ohms at 1 MHz • Maximum capacitance: 20 pf/foot • Attenuation: 6.6 dB/1000 ft at 1 MHz • Calculate the amplitude of the signal after 1000 ft and 10,000 ft (Ethernet uses Manchester Encoding)

  47. Thank You

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