Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

3. transmission media

6,079 views

Published on

Published in: Business, Technology
  • Be the first to comment

3. transmission media

  1. 1. Transmission Media ( Guided and Wireless Transmission ) Pg 128
  2. 2. Overview <ul><li>Guided – provide a physical path along which the signals are propagated </li></ul><ul><ul><li>Wire: Coaxial Cable, Optical Fiber, Twisted Pair </li></ul></ul><ul><li>Unguided –employ an antenna for transmitting through air, vacuum or water. </li></ul><ul><ul><li>wireless </li></ul></ul><ul><li>Characteristics and quality determined by medium and signal </li></ul><ul><ul><li>For guided, the medium is more important </li></ul></ul><ul><ul><li>For unguided, the bandwidth produced by the antenna is more important </li></ul></ul><ul><li>Key concerns are data rate and distance </li></ul>Key Points
  3. 3. Design Factors <ul><li>Bandwidth </li></ul><ul><ul><li>Higher bandwidth gives higher data rate </li></ul></ul><ul><li>Transmission impairments </li></ul><ul><ul><li>Attenuation </li></ul></ul><ul><li>Interference </li></ul><ul><li>Number of receivers </li></ul><ul><ul><li>In guided media </li></ul></ul><ul><ul><li>More receivers (multi-point) introduce more attenuation </li></ul></ul>
  4. 4. Electromagnetic Spectrum
  5. 5. 2.2.1 Guided Transmission Media <ul><li>To become part of network, a PC uses a network interface card (NIC). </li></ul><ul><li>(For portable comp., NIC can be in form of a PC Card/ USB adapter ) </li></ul><ul><li>Backbone ,connection leading to and from it might use: </li></ul><ul><li>Twisted Pair </li></ul><ul><li>Coaxial cable </li></ul><ul><li>Optical fiber </li></ul>PC’s RAM NIC LAN’s backbone signal signal
  6. 6. Transmission Characteristics of Guided Media     Frequency Range Typical Attenuation Typical Delay Repeater Spacing Twisted pair (with loading) 0 to 3.5 kHz 0.2 dB/km @ 1 kHz 50 µs/km 2 km Twisted pairs (multi-pair cables) 0 to 1 MHz 0.7 dB/km @ 1 kHz 5 µs/km 2 km Coaxial cable 0 to 500 MHz 7 dB/km @ 10 MHz 4 µs/km 1 to 9 km Optical fiber 186 to 370 THz 0.2 to 0.5 dB/km 5 µs/km 40 km
  7. 7. Twisted Pair – Physical Description
  8. 8. Twisted Pair - Applications <ul><li>Most common transmission medium for analog/digital signal </li></ul><ul><li>Telephone network </li></ul><ul><ul><li>Between house and local tel. exchange (subscriber loop) </li></ul></ul><ul><li>Com. within buildings </li></ul><ul><ul><li>To private branch exchange (PBX) </li></ul></ul><ul><li>For local area networks (LAN) </li></ul><ul><ul><li>10Mbps or 100Mbps </li></ul></ul>
  9. 9. Twisted Pair - Pros and Cons <ul><li>Pros </li></ul><ul><li>Cheap </li></ul><ul><li>Easy to work with </li></ul><ul><li>Cons </li></ul><ul><li>Low data rate </li></ul><ul><li>Short range </li></ul>
  10. 10. Twisted Pair - Transmission Characteristics <ul><li>Analog </li></ul><ul><ul><li>Amplifiers every 5km to 6km </li></ul></ul><ul><li>Digital </li></ul><ul><ul><li>Use either analog or digital signals </li></ul></ul><ul><ul><li>repeater every 2km or 3km </li></ul></ul><ul><li>Limited distance </li></ul><ul><li>Limited bandwidth (1MHz) </li></ul><ul><li>Limited data rate (100MHz) </li></ul><ul><li>Susceptible to interference and noise </li></ul>
  11. 11. Coaxial Cable - Physical Description
  12. 12. Coaxial Cable - Applications <ul><li>Most versatile medium </li></ul><ul><li>Television distribution </li></ul><ul><ul><li>Arial to TV </li></ul></ul><ul><ul><li>Cable TV </li></ul></ul><ul><li>Long distance telephone transmission </li></ul><ul><ul><li>Can carry 10,000 voice calls simultaneously </li></ul></ul><ul><ul><li>Being replaced by fiber optic </li></ul></ul><ul><li>Short distance computer systems links </li></ul><ul><ul><li>Connections between devices </li></ul></ul><ul><li>Local area networks </li></ul>
  13. 13. Coaxial Cable - Benefits <ul><li>Less susceptible to interference and crosstalk** </li></ul><ul><li>Longer distance** </li></ul><ul><li>**(compared to twisted pair) </li></ul><ul><li>Wide variety of application </li></ul>
  14. 14. Coaxial Cable - Transmission Characteristics <ul><li>Analog </li></ul><ul><ul><li>Amplifiers every few km </li></ul></ul><ul><ul><li>Closer if higher frequency </li></ul></ul><ul><ul><li>Up to 500MHz </li></ul></ul><ul><li>Digital </li></ul><ul><ul><li>Repeater every 1km </li></ul></ul><ul><ul><li>Closer for higher data rates </li></ul></ul>
  15. 15. Optical Fiber - Physical Description
  16. 16. Optical Fiber - Benefits <ul><li>Greater capacity </li></ul><ul><ul><li>Data rates of hundreds of Gbps </li></ul></ul><ul><li>Smaller size & weight </li></ul><ul><li>Lower attenuation </li></ul><ul><li>Electromagnetic isolation </li></ul><ul><ul><li>Not affected by external electromagnetic fields </li></ul></ul><ul><li>Greater repeater spacing </li></ul><ul><ul><li>10s of km at least </li></ul></ul>
  17. 17. Optical Fiber - Applications <ul><li>Tel. network </li></ul><ul><li>Long-haul trunks (laluan) </li></ul><ul><ul><li>aver. 1500 km, 20k-60k voice channels </li></ul></ul><ul><li>Metropolitan trunks </li></ul><ul><li>aver. 12 km, 100k voice channels </li></ul><ul><li>Rural exchange trunks </li></ul><ul><ul><li>Links town-village 40-160 km </li></ul></ul><ul><li>Subscriber (Pelanggan) loops </li></ul><ul><ul><li>Central exchange - subsciber </li></ul></ul><ul><li>LANs </li></ul><ul><ul><li>100 Mbps to 1Gbps </li></ul></ul>
  18. 18. Optical Fiber Transmission Modes
  19. 19. Wireless Transmission Frequencies <ul><li>2GHz to 40GHz </li></ul><ul><ul><li>Microwave frequencies </li></ul></ul><ul><ul><ul><li>Highly directional (one way) </li></ul></ul></ul><ul><ul><ul><li>Point to point transmission </li></ul></ul></ul><ul><ul><ul><li>Satellite </li></ul></ul></ul><ul><li>30MHz to 1GHz ( radio range ) </li></ul><ul><ul><li>Omnidirectional </li></ul></ul><ul><ul><li>Broadcast radio </li></ul></ul><ul><li>3 x 10 11 to 2 x 10 14 Hz </li></ul><ul><ul><li>Infrared </li></ul></ul>
  20. 20. Antennas <ul><li>Electrical conductor (or system of conductor) used to radiate electromagnetic energy or collect electromagnetic energy </li></ul><ul><li>Transmission of signal </li></ul><ul><ul><li>Radio-frequency electrical energy from transmitter </li></ul></ul><ul><ul><li>Converted to electromagnetic energy </li></ul></ul><ul><ul><li>By antenna </li></ul></ul><ul><ul><li>Radiated into surrounding environment; atmosphere, space, water </li></ul></ul><ul><li>Reception of signal </li></ul><ul><ul><li>Electromagnetic energy impinging(melanggar) on antenna </li></ul></ul><ul><ul><li>Converted to radio-frequency electrical energy </li></ul></ul><ul><ul><li>Fed to receiver </li></ul></ul><ul><li>Same antenna often used for both </li></ul>
  21. 21. Terrestrial Microwave <ul><li>Parabolic dish </li></ul><ul><li>Long haul telecommunications (application) </li></ul><ul><ul><li>alternative to coaxial cable or optical fiber. </li></ul></ul><ul><ul><li>requires far fewer amplifiers/repeaters than coaxial cable over the same distance but requires LOS (line-of -sight) transmission. </li></ul></ul><ul><li>Higher frequencies give higher data rates </li></ul><ul><ul><li>common frequencies used for transmission are in the range 1 to 40GHz. </li></ul></ul>
  22. 22. Satellite Microwave <ul><li>Satellite is relay station </li></ul><ul><li>Satellite receives on one frequency (uplink), amplifies or repeats signal and transmits on another frequency (downlink) </li></ul><ul><li>Applications </li></ul><ul><ul><li>Television </li></ul></ul><ul><ul><li>Long distance telephone </li></ul></ul>
  23. 23. Satellite Point to Point Link Uplink Downlink
  24. 24. Satellite Broadcast Link
  25. 25. Broadcast Radio <ul><li>Omnidirectional </li></ul><ul><li>FM radio </li></ul><ul><li>UHF and VHF television </li></ul><ul><li>Suffers from multipath interference </li></ul><ul><ul><li>Reflections </li></ul></ul>
  26. 26. Infrared <ul><li>Achieved using transmitter/receivers (transceiver) that modulate non-coherent infrared light </li></ul><ul><li>Transceivers must be within the line of sight of each other either directly or via reflection form a light-colored surface such as the ceiling of a room. </li></ul><ul><li>Blocked by walls </li></ul><ul><li>e.g. TV remote control </li></ul>
  27. 27. Wireless Propagation <ul><li>Signal travels along three routes </li></ul><ul><ul><li>Ground wave </li></ul></ul><ul><ul><ul><li>Follows contour of earth </li></ul></ul></ul><ul><ul><ul><li>Up to 2MHz </li></ul></ul></ul><ul><ul><ul><li>Best-known example of ground wave communication is AM radio </li></ul></ul></ul><ul><ul><li>Sky wave </li></ul></ul><ul><ul><ul><li>Used for amateur radio, BBC world service, Voice of America </li></ul></ul></ul><ul><ul><ul><li>A signal from an earth-based antenna is reflected from ionosphere layer of upper atmosphere back down to earth. </li></ul></ul></ul><ul><ul><li>Line of sight (LOS) </li></ul></ul><ul><ul><ul><li>Above 30Mhz, neither ground wave or sky wave propagation modes operate, and communication must be by LOS. </li></ul></ul></ul>
  28. 28. Line of Sight Transmission’s Impairment <ul><li>Free space loss </li></ul><ul><ul><li>Signal disperses with distance (signal spread over a larger and larger area) </li></ul></ul><ul><li>Atmospheric Absorption </li></ul><ul><ul><li>Water vapour and oxygen absorb radio signals </li></ul></ul><ul><ul><li>Water greatest at 22GHz, less below 15GHz </li></ul></ul><ul><ul><li>Oxygen greater at 60GHz, less below 30GHz </li></ul></ul><ul><ul><li>Rain and fog scatter radio waves that results in attenuation. </li></ul></ul><ul><li>Multipath </li></ul><ul><ul><li>Better to get line of sight if possible </li></ul></ul><ul><ul><li>Signal can be reflected causing multiple copies to be received </li></ul></ul><ul><ul><li>May be no direct signal at all </li></ul></ul><ul><ul><li>May reinforce or cancel direct signal </li></ul></ul><ul><li>Refraction </li></ul><ul><ul><li>May result in partial or total loss of signal at receiver </li></ul></ul>END!!
  29. 29. Ground Wave Propagation
  30. 30. Sky Wave Propagation
  31. 31. Line of Sight Propagation
  32. 32. Free Space Loss
  33. 33. Multipath Interference
  34. 34. Key Points <ul><li>Transmission media – guided and unguided </li></ul><ul><li>For guided transmission: </li></ul><ul><ul><li>Twisted pair has been the workhorse for com. of all sorts. </li></ul></ul><ul><ul><li>Higher data rates over longer distances can be achieved with coaxial cable, so coaxial cable has been often been used for high-speed LAN and for high-capacity long-distance trunk applications. </li></ul></ul>
  35. 35. Key Points(2) <ul><ul><li>However, tremendous capacity of optical fiber has made that medium more attractive than coaxial cable, and thus optical fiber has taken over much of the market for high-speed LANs and for long-distance applications. </li></ul></ul><ul><li>For unguided transmission: </li></ul><ul><ul><li>Commonly used for info. com. including broadcast radio, terrestrial ( daratan ) microwave, and satellite. Infrared transmission is used in some LAN applications. </li></ul></ul>
  36. 36. Local Telephone Exchange <ul><li>A telephone exchange is the place that users voice and broadband is delivered to and from to their address. </li></ul><ul><li>The exchange splits the signals that it receives so it can then send them on to the correct part of the exchange. Voice calls are sent to the PSTN ( P ublic S witched T elephone N etwork) network and broadband/ADSL signals is sent to the DSLAM ( D igital S ubscriber L ine A ccess M ultiplexer). </li></ul>
  37. 37. private branch exchange <ul><li>A PBX (private branch exchange) is a telephone system within an enterprise that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines. The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company's central office. </li></ul>

×