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Question about digital broadcasting

  1. Jul 9, 2012 #1
    Is the DVB-T broadcasting standard exactly the same as the DVB-C broadcasting standard?
     
  2. jcsd
  3. Jul 10, 2012 #2
    The thread originator is requesting an answer to the question.
     
  4. Jul 10, 2012 #3

    berkeman

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    Staff: Mentor

    Can you post links to information about those standards? What are your thoughts about whether they are the same or not?
     
  5. Jul 10, 2012 #4
  6. Oct 13, 2012 #5
    Both standards deal with properties of communication channels for which they were designed.

    DVB-C (C=Cable): high SNR, no multipath, channel width 10MHz
    DVB-T (T=Terrestrial): low SNR, multipath, channel grid 7 or 8 MHz

    Both use OFDM QAM. Maybe different CRC? The latest incarnations (-C2 and -T2) introduce further improvements.
    Edit: Wikipedia claims that DVB-C used regular QAM. The DVB-C2 uses OFDM.

    The data format should be same (DVB packets). The only difference is in the physical layer.
     
  7. Oct 14, 2012 #6
    Alright, now here is another question: why did computerized digital controls for televisions featuring push button controls, numerical channel markers on screen and a main menu for adjusting various settings appear before digital broadcasting? The digitally controlled televisions and CATV digitally controlled converter boxes for retrofitting analog televisions were launched in the 1980's but they still had analog tuners to receive analog broadcasts, why did the television stations worldwide still maintain analog broadcasts up to the 2010's instead of shutting down all the analog stations at once and upgrading all the stations for digital broadcasting at the same time digitally controlled televisions emerged?
     
    Last edited: Oct 14, 2012
  8. Oct 14, 2012 #7
    Backward compatibility has a strong influence on progress. Color television was introduced, and some make a strong case for the quality being less than optimal, because they didn't want to demand that x hundred million families all throw away their black and white set on Friday and each go out and spend $500 on a new color set, no matter how happy that might have made the television sales channel. Likewise for digital television signal broadcasting.

    Analog cell phones made a similar transition to digital cell phones, but that happened faster because I think the typical lifetime of a cell phone is measured in months and not in years, but again they did not have "national throw your cell phone away on Friday day" and there was a progressive transition, but done in a different way.
     
  9. Mar 8, 2013 #8
    Now here is some more information about broadcasting. Multiple broadcasters such as cable and satellite TV providers can use the same broadcasting standard but they can restrict access to their signals using encryption where each company can use its own unique encryption cipher. Some companies that provide satellites and cable converter boxes actually put the label ENC# <Insert ID #> beside the inscription on their devices indicating the broadcasting standard. This information is used to distinguish their encryption method from the methods used by other companies.

    Encryption, which basically involves the scrambling of the arrangement of the data is done so that people viewing the broadcasts cannot just buy and connect any television or converter box directly to a cable or mount a parabolic antenna on their roofs that use circuits that are compatible with the broadcasting standards of the provider and get broadcasts without paying the provider. The provider has the decryption software saved into the memory chips of their devices so that the customer would have to apply for their service first before receiving the converter boxes or parabolic antennas that have the provider's decryption system in place. As an additional security feature in case someone gets hold of a discarded or stolen converter box or parabolic antenna, such devices are given ID's like the IP and MAC addresses of internet modems and computers which have to be transmitted to the servers of the providers and verified before the packets of data which are tagged with a destination header ID to ensure that only that particular device receives the requested data, are sent to the customer. If a device is reported stolen or discarded, or if the device was stolen after it was recovered from a customer who had their service terminated, the ID of that device can be removed from the approved list of ID's in the servers so that every time that particular device makes a request for the broadcasted data, it is denied by the servers.

    A digital switch such as those used to enable multiple computers to use the same modem cannot be used in enabling multiple digital televisions to use the same receiver box or antenna to access digital television broadcasts because the television sets are not equipped with transceiver chips like the computer internet cards that possess MAC ID's that can be used to identify requests for channels coming from that specific television and additionally, the servers of the cable and satellite TV providers may have a system that only accepts ID's coming from their converter boxes and parabolic antennas.
     
    Last edited: Mar 8, 2013
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