Cable modems

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Cable modems

  1. 1. Cable Modems<br />Adam Rudderow<br />TED 111<br />www.wireless-thing.com<br />
  2. 2. External Cable Modems<br />a small box that can provide a computer with an Internet connection through either usb or ethernet. <br />most cable modems do come with USB ports installed as well as the usual Ethernet port<br />
  3. 3. Internal Cable Modems<br />Internal cable modems come in form of a PCI (Peripheral Component Interconnect) bus card for PC's<br />Disadvantage:<br />If cable modem is powered down just itself, computer would be powered down as well<br />
  4. 4. Set Top Box Integrated Cable Modems<br />Commonly used for services like interactive TV and Internet via your television<br />Many companies use this type of cable modem to supply Internet access to your computer<br />
  5. 5. Downstream/Upstream<br />Downstream data is transmitted from the Internet towards the computer that requested it<br />Upstream data is data that is sent or "uploaded" from a computer towards the Internet<br />http://www.tvcinc.com/products/cm550.jpg<br />
  6. 6. CATV Infrastructures <br />Cable Access Television, sometimes known as Community Antenna Television<br />Modems use CATV infrastructures that partly consist of HFC (Hybrid Fibre-Coax)<br />http://www.microsens.pl/gifs_all/catv_node.gif<br />
  7. 7. Typical Cable Modem Components<br />www.talkbroadband.com<br />
  8. 8. Tuner<br />Connects to the CATV outlet<br />Digital modulated signals and then forwards them towards the demodulator<br />Can be attached to a diplexer, which enables the tuner to use a range of frequencies for both the downstream and upstream traffic<br />
  9. 9. Demodulator<br />Four main functions:<br />QAM (Quadrature Amplitude Modulation)<br />A/D converter (Analog to Digital)<br />Error correction<br />MPEG (Moving Picture Experts Group) synchronizer<br />
  10. 10. Demodulator (Cont’d)<br />QAM takes radio-frequency signal and changes it so the A/D converter can process it<br />A/D converter converts signal into a digital signal of 0's and 1's<br />Error correct module then compares the data received to a known standard, fixing errors in transmission<br />MPEG synchronizer is then used to sequence and organise data groups into their correct order<br />
  11. 11. Modulator<br />Three main functions:<br />To insert data that is ready for error correction<br />QAM (Quadrature Amplitude Modulation)<br />D/A conversion (digital to analog)<br />
  12. 12. Modulator (Cont’d)<br />AKA Burst modulator<br />Converts digital data back into analog radio frequency signals so that they are ready for transmission<br />
  13. 13. MAC (Media Access Control)<br /> Acts as the interface between parts of various network protocols<br /> Either the CPU of the cable modem or the CPU of the computer is used to take some pressure away from the MAC because of the complexity of its functions.<br />
  14. 14. CPU (Central Processing Unit)<br /> The brain that controls all of the activity inside the cable modem itself<br />www.novopc.com<br />
  15. 15. Citations<br />http://www.talkbroadband.com/articles/19/1/How-do-Cable-Modems-Work%3F<br />http://www.howstuffworks.com/cable-modem.htm/printable<br />http://www.ehow.com/how-does_4962579_how-cable-modems-work.html<br />

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