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lesson_3.pptx

  1. 1. 1 Transmission Media lesson 3
  2. 2. 2 Overview • Guided transmission media – wire (twisted pair, coaxial cable, fiber) • Unguided – wireless (radio wave, microwave, satellite) • Characteristics and quality determined by medium and signal • For guided, the medium is more important • For unguided, the bandwidth produced by the antenna is more important
  3. 3. 3 Design Factors • Bandwidth —Higher bandwidth gives higher data rate • Transmission impairments —Attenuation • Interference • Number of receivers
  4. 4. 4 Electromagnetic Spectrum
  5. 5. 5 Guided Transmission Media • Twisted Pair • Coaxial cable • Optical fiber
  6. 6. 6 Twisted Pair
  7. 7. 7 Twisted Pair - Applications • Most common medium • Telephone network —Between house and local exchange (subscriber loop) • Within buildings —To private branch exchange (PBX) • For local area networks (LAN) —10Mbps or 100Mbps
  8. 8. 8 Twisted Pair - Pros and Cons • Cheap • Easy to work with • Low data rate • Short range
  9. 9. 9 Twisted Pair - Transmission Characteristics • Analog —Amplifiers every 5km to 6km • Digital —Use either analog or digital signals —repeater every 2km or 3km • Limited distance • Limited bandwidth (1MHz) • Limited data rate (100MHz) • Susceptible to interference and noise
  10. 10. 10 STP &UTP • STP&UTP
  11. 11. 11 Unshielded and Shielded TP • Unshielded Twisted Pair (UTP) —Ordinary telephone wire —Cheapest —Easiest to install —Suffers from external EM interference • Shielded Twisted Pair (STP) —Metal braid or sheathing that reduces interference —More expensive —Harder to handle (thick, heavy)
  12. 12. 12 UTP categories The Electronic Industries Association (EIA) has developed standards to grade UTP. 1. Category 1. The basic twisted-pair cabling used in telephone systems. This level of quality is fine for voice but inadequate for data transmission. 2. Category 2. This category is suitable for voice and data transmission of up to 2Mbps. 3. Category 3.This category is suitable for data transmission of up to 10 Mbps. It is now the standard cable for most telephone systems. 4. Category 4. This category is suitable for data transmission of up to 20 Mbps. 5. Category 5. This category is suitable for data transmission of up to 100 Mbps.
  13. 13. 13 Coaxial Cable Coaxial cable consist the followings layers in its construction -The copper conductor -Insulation layer of plastic foam -Second conductor or shield of wire mesh tube or metallic foil -Outer jacket of tough plastic Coaxial cable can be used over longer distances and support more stations on a shared line than twisted pair
  14. 14. 14 Coaxial Cable Applications • Most versatile medium • Television distribution —Ariel to TV —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
  15. 15. 15 Coaxial Cable - Transmission Characteristics • Analog —Amplifiers every few km —Closer if higher frequency —Up to 500MHz • Digital —Repeater every 1km —Closer for higher data rates
  16. 16. Coaxial cable 16
  17. 17. • Coaxial types: — Thicker used with large networks. — Thinner used with small networks. 17 Coaxial Cable (or Coax)
  18. 18. Coax Advantages & Disadvantages Advantages Disadvantages • Higher bandwidth —400 to 600Mhz • Much less susceptible to interference than twisted pair • It will not cause a toxic gas when its burned. That’s why they use it in some buildings. • High attenuation rate makes it expensive over long distance • It’s not used anymore due to high cost and other technical factors. 18
  19. 19. 19 Optical Fiber
  20. 20. 20 Optical Fiber - Applications • Long-haul trunks • Metropolitan trunks • Subscriber loops • LANs
  21. 21. 21 Optical Fiber - Transmission Characteristics • Act as wave guide for 1014 to 1015 Hz —Portions of infrared and visible spectrum • Light Emitting Diode (LED) —Cheaper —Wider operating temp range —Last longer • Injection Laser Diode (ILD) —More efficient —Greater data rate
  22. 22. Digital data is converted to light • Single mode - one light source flashes a light down the cable. —can carries single ray of light • Multimode - supports many simultaneous light transmissions. —capable of carrying multiple beams of light. 22 Fiber Optic Types
  23. 23. Fiber Optic Advantages & Disadvantages Advantages Disadvantages • greater capacity (bandwidth of up to 2 Gbps) • Speed (100 - 500 mbps) • smaller size and lighter weight • lower attenuation • immunity to environmental interference • highly secure • Electromagnetic isolation • expensive over short distance • requires highly skilled installers • adding additional nodes is difficult 23

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