The broadcast media industry is also at a critical turning point
in its development, with many countries starting to move from
analogue to digital broadcasts. The chief advantage of digital
broadcasts is that they prevent a number of complaints with traditional
analogue broadcasts. For television, this includes the elimination
of problems such as snowy pictures, ghosting and other distortion.
These occur because of the nature of analogue transmission, which
means that perturbations due to noise will be evident in the final
output. Digital transmission overcomes this problem because digital
signals are reduced to binary data upon reception and hence small
perturbations do not affect the final output.
In a simplified example, if a binary message 1011 was transmitted
with signal amplitudes [ 1.0 0.0 1.0 1.0 ] and received with signal
amplitudes [ 0.9 0.2 1.1 0.9 ] it would still decode to the binary
message 1011 — a perfect reproduction of what was sent.
From this example, a problem with digital transmissions can also
be seen in that if the noise is great enough it can significantly
alter the decoded message. Using forward error correction a receiver
can correct a handful of bit errors in the resulting message but
too much noise will lead to incomprehensible output and hence
a breakdown of the tranmission. |
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