Explain the concept of DVB.
1 Answer
  • DVB stands for Digital Video Broadcasting, it is a set of standards that define digital broadcasting using existing satellite, cable, and terrestrial infrastructures.
  • This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing (COFDM or OFDM) modulation. It is also the format widely used worldwide (including North America) for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point.
  • Rather than carrying one data carrier on a single radio frequency (RF) channel, COFDM works by splitting the digital data stream into a large number of slower digital streams, each of which digitally modulates a set of closely spaced adjacent sub-carrier frequencies.
  • In the case of DVB-T, there are two choices for the number of carriers known as 2K-mode or 8K-mode. These are actually 1,705 or 6,817 sub-carriers that are approximately 4 kHz or 1 kHz apart.
  • DVB-T offers three different modulation schemes (QPSK, 16QAM, 64QAM)
  • The receiver receives the digital data stream. The data flows into the conditional access module, which contains the content provider's unscrambling algorithms. The conditional access module verifies the existence of a smart card that contains the subscriber's authorization code.
  • If the authorization code is accepted, the conditional access module unscrambles the data and returns the data to the receiver. If the code is not accepted, the data remains scrambled restricting access. The receiver then decodes the data and outputs it for viewing
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